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📰 De l'uranium pour produire efficacement alcool et éther

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Des chimistes de l'Iramis montrent qu'un oxyde d'uranium (l'ion uranyle) catalyse de manière sélective et efficace la réduction chimique d'un composé organique contenant des liaisons C=O (aldéhydes), en présence d'un composé du silicium (Le silicium est un élément chimique de la famille des cristallogènes, de symbole Si et de numéro atomique 14.) (hydrosilane) pour obtenir ainsi un alcool ou un éther. Une réaction en conditions douces qui intéresse le secteur de la chimie (La chimie est une science de la nature divisée en plusieurs spécialités, à l'instar de la physique et de la biologie avec lesquelles elle partage des espaces...) fine.

Tandis que la pétrochimie (La pétrochimie est la science qui s'intéresse à l'utilisation des composés chimiques de base issus du pétrole pour fabriquer d'autres composés synthétiques qui peuvent exister ou...) utilise des réactions d'oxydation pour transformer les hydrocarbures, les industriels de la chimie fine ont parfois recours à des réactions de réduction pour produire, par exemple, des éthers ou des alcools à partir de composés carbonylés (contenant une liaison C=O) comme des cétones, des aldéhydes ou des esters. Depuis quelques années, les chercheurs en chimie envisagent des réductions catalytiques dans des conditions plus douces que celles de l'industrie, avec des réducteurs hydrosilanes (RnSixHy). Celles-ci requièrent néanmoins un catalyseur (En chimie, un catalyseur est une substance qui augmente la vitesse d'une réaction chimique ; il participe à la réaction mais il ne fait partie ni des produits, ni des...) efficace et sélectif pour obtenir au final un seul produit.

Une équipe de l'Iramis propose pour la première fois un catalyseur à base d' uranium (L'uranium est un élément chimique de symbole U et de numéro atomique 92. C'est un élément naturel assez fréquent : plus abondant que l'argent, autant...) naturel ou appauvri, très abondant, dont l' industrie nucléaire (L'industrie nucléaire comprend l'ensemble des procédés de transformation et des acteurs économiques qui utilisent les propriétés du noyau atomique. Dans le domaine civil,...) possède des tonnages importants. Ce catalyseur contient un ion (Un ion est une espèce chimique électriquement chargée. Le terme vient de l'anglais, à partir de l'adjectif grec ἰόν (ion), se traduisant par " allant, qui va ".) uranyle O=U2+=O, un oxyde (Un oxyde est un composé de l'oxygène avec un élément moins électronégatif, c'est-à-dire tous sauf le fluor. Oxyde désigne également l'ion oxyde O2-.) très stable. Cet ion oxydé ne réagit pas avec les hydrosilanes et catalyse (La catalyse est l'action d'une substance appelée catalyseur sur une transformation chimique dans le but de modifier sa vitesse de réaction. Le catalyseur, qui est en...) très efficacement la réduction d'un aldéhyde (alcool "déshydrogéné"). En modulant l'encombrement de la molécule (Une molécule est un assemblage chimique électriquement neutre d'au moins deux atomes, qui peut exister à l'état libre, et qui...) de silane, la réaction ainsi catalysée produit sélectivement soit un alcool, soit un éther.

Références

Breaking C-O bonds with uranium: uranyl complexes as selective catalysts in the hydrosilylation of aldehydes, ACS Catalysis

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📰 De l'uranium pour produire efficacement alcool et éther

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Des chimistes de l'Iramis montrent qu'un oxyde d'uranium (l'ion uranyle) catalyse de manière sélective et efficace la réduction chimique d'un composé organique contenant des liaisons C=O (aldéhydes), en présence d'un composé du silicium (Le silicium est un élément chimique de la famille des cristallogènes, de symbole Si et de numéro atomique 14.)

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Climate change: Asia 'coal addiction' must end, UN chief warns - BBC News

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The chief of the United Nations has warned Asia to quit its "addiction" to coal in a bid to tackle climate change.

UN Secretary General António Guterres said countries in the region were among the most vulnerable to global warming and should be on the "front line" of efforts to stop it.

He cited a new study that found that Asian countries were at particular risk of climate-driven flooding.

Coal is a major source of power in many Asian countries.

Twelve years to save Earth? Make that 18 months...

UN panel signals red alert on 'Blue Planet'

What is climate change?

Speaking to reporters in the Thai capital Bangkok on Saturday, Mr Guterres described climate change as the "defining issue of our time".

The UN chief referenced a study published on Tuesday, which found that climate change would put millions more people at risk from coastal flooding by 2050 than previously thought.

The majority of those implicated were in developing countries across Asia, the study said.

Mr Gutterres said that while "people can discuss the accuracy of these figures...what is clear is that the trend is there".

He said the issue was "particularly sensitive" in Asia, where a "meaningful number" of new coal power plants are planned.

"We have to put a price on carbon. We need to stop subsidies for fossil fuels. And we need to stop the creation of new power plants based on coal in the future," Mr Gutterres warned.

Who is at risk in Asia?

Tuesday's report by Climate Central, a US-based non-profit news organisation, said 190 million people would be living in areas that are projected to be below high-tide lines in the year 2100.

It found that even with moderate reductions in greenhouse gas emissions, six Asian countries (China, Bangladesh, India, Vietnam, Indonesia, and Thailand), where 237 million people live today, could face annual coastal flooding threats by 2050.

You may be interested in
How coastal erosion destroyed a Ghanaian village

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Quit 'coal addiction', UN boss warns Asia

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The chief of the United Nations has warned Asia to quit its "addiction" to coal in a bid to tackle climate change. UN Secretary General António Guterres said countries in the region were among the most vulnerable to global warming and should be on the "front line" of efforts to stop it.

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Leonardo Di Caprio: 'Greta Thunberg a leader of our time' - BBC News

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Leonardo DiCaprio was impressed when he met Greta Thunberg.

The actor shared a picture of himself with the climate change activist on Instagram.

He wrote he hoped "Greta's message is a wake-up call to world leaders everywhere" and that the "time for inaction is over."

He also praised the teenager for her work and said because of her he is "optimistic about what the future holds".

Image Copyright leonardodicaprio leonardodicaprioReport

The image has had almost 4 million likes since it was posted 22 hours ago.

Greta Thunberg has helped start an international youth movement against climate change.

The Swedish teenager first staged a "School Strike for Climate" in front of the Swedish Parliament in August last year.

Her strike has inspired students from around the world, leading tens of thousands of students from Germany, Japan, the UK, Australia and many more to join her #FridaysforFuture demonstrations.

Leo wrote: "There are few times in human history where voices are amplified at such pivotal moments and in such transformational ways but @GretaThunberg has become a leader of our time.

"History will judge us for what we do today to help guarantee that future generations can enjoy the same liveable planet that we have so clearly taken for granted."

The Hollywood star has also been outspoken about environmental issues.

He told Newsbeat in 2016 he thinks climate change is the biggest issue facing young people today.

He has a foundation which describes itself as being dedicated to addressing climate change and environmental threats to life on Earth.

His organisation recently put $5m (£4.1m) towards helping the Amazon rainforest after the recent outbreak of fires there.

He said it was "an honor to spend time with Greta. She and I have made a commitment to support one another, in hopes of securing a brighter future for our planet."

Listen to Newsbeat live at 12:45 and 17:45 weekdays - or listen back here.

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When Leo met Greta: Di Caprio praises Thunberg

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Leonardo DiCaprio was impressed when he met Greta Thunberg. The actor shared a picture of himself with the climate change activist on Instagram. He wrote he hoped "Greta's message is a wake-up call to world leaders everywhere" and that the "time for inaction is over."

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Jane Fonda: 'I worry about climate activist Greta Thunberg' - BBC News

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The actress and activist Jane Fonda says she "worries" about climate activist Greta Thunberg.

"She understands that if she's attacked it's because she's making a difference and that scares people," says Fonda.

The 81-year-old has vowed to protest every Friday until January to demand for action to be taken to address climate change.

Thunberg, 16, found fame after her youth climate strike protests spread to schools around the world.

"They handcuff you with plastic things, not the old good metal ones. They hurt more," Fonda says of her most recent arrest.

But she says: "I don't want to go to prison.

"I don't think that Jane Fonda the martyr is exactly what the movement needs right now."

"The police are figuring out what to do. I was told if I keep getting arrested every week I may be put in the slammer. I may not get arrested every week because I have to start filming Grace and Frankie (her series for Netflix)."

Fonda has been an active campaigner for years, being involved in Native American rights campaigns, civil rights campaigns and protesting against the Vietnam War.

"I haven't been very well in my skin because I knew I wasn't doing what I can do. I was not a super happy person until I started to do this."

She says she asked an "ocean scientist" taking part in her recent protest, "How do you stop from getting depressed?

"He said, 'I become active. The minute you start doing something about it, the depression goes away'."

Her latest action, she says, was inspired by the student protests led by Thunberg.

They are "more politically savvy than we ever were at that age. They're much more sensitive of diversity. This can't be a white, elite climate action.
You can hear the full interview with Jane Fonda on BBC Radio 4's Broadcasting House.

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Jane Fonda: 'I worry about Greta Thunberg'

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The actress and activist Jane Fonda says she "worries" about climate activist Greta Thunberg. "She understands that if she's attacked it's because she's making a difference and that scares people," says Fonda. The 81-year-old has vowed to protest every Friday until January to demand for action to be taken to address climate change.

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Satellites are key to monitoring ocean carbon | EurekAlert! Science News

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Satellites now play a key role in monitoring carbon levels in the oceans, but we are only just beginning to understand their full potential.

Our ability to predict future climate relies upon being able to monitor where our carbon emissions go. So we need to know how much stays in the atmosphere, or becomes stored in the oceans or on

land. The oceans in particular have helped to slow climate change as they absorb and then store the carbon for thousands of years.

The IPCC Special Report on the Oceans and Cryosphere in a Changing Climate, published in September, identified this critical role that the ocean play in regulating our climate along with the need to increase our monitoring and understanding of ocean health.

But the vast nature of the oceans, covering over 70% of the Earth's surface, illustrates why satellites are an important component of any monitoring.

The new study, led by the University of Exeter, says that increased exploitation of existing satellites will enable us to fill "critical knowledge gaps" for monitoring our climate.

The work reports that satellites originally launched to study the wind, also have the capability to observe how rain, wind, waves, foam and temperature all combine to control the movement of heat and carbon dioxide between the ocean and the atmosphere.

Additionally, satellites launched to monitor gas emissions over the land are also able to measure carbon dioxide emissions as they disperse over the ocean.

Future satellite missions offer even greater potential for new knowledge, including the ability to study the internal circulation of the oceans. New constellations of commercial satellites, designed to monitor the weather and life on land, are also capable of helping to monitor ocean health.

"Monitoring carbon uptake by the oceans is now critical to understand our climate and for ensuring the future health of the animals that live there," said lead author Dr Jamie Shutler, of the Centre for Geography and Environmental Science on Exeter's Penryn Campus in Cornwall.

"By monitoring the oceans we can gather the necessary information to help protect ecosystems at risk and motivate societal shifts towards cutting carbon emissions."

The research team included multiple European research institutes and universities, the US National Oceanic and Atmospheric Administration, the Japan Aerospace Exploration Agency and the European Space Agency.

The researchers call for a "robust network" that can routinely observe the oceans.

This network would need to combine data from many different satellites with information from automated instruments on ships, autonomous vehicles and floats that can routinely measure surface water carbon dioxide.

And recent computing advancements, such as Google Earth Engine, which provides free access and computing for scientific analysis of satellite datasets, could also be used.

The study suggests that an international charter that makes satellite data freely available during major disasters should be expanded to include the "long-term man-made climate disaster", enabling commercial satellite operators to easily contribute.

The research was supported by the International Space Science Institute ISSI Bern, Switzerland, and initiated by Dr Shutler at the University of Exeter and Dr Craig Donlon at the European Space Agency.

The paper, published this week in Frontiers in Ecology and Environment, is entitled: "Satellites will address critical science priorities for quantifying ocean carbon."

###

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.

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Satellites are key to monitoring ocean carbon

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Satellites now play a key role in monitoring carbon levels in the oceans, but we are only just beginning to understand their full potential. Our ability to predict future climate relies upon being able to monitor where our carbon emissions go.

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How plastic bags were supposed to help the planet - BBC News

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How plastic bags were supposed to help the planet

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Family of inventor says they were designed to be reused to stop trees from being destroyed.

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Extinction Rebellion protesters dragged from Tube train roof - BBC News

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Commuters have dragged climate change protesters from the roof of a London Underground train.

Extinction Rebellion activists climbed on top of trains at Stratford, Canning Town and Shadwell during Thursday's rush hour.

The Jubilee Line and Docklands Light Railway were earlier partially suspended. Minor delays are still reported on the lines.

Four protesters have been arrested, British Transport Police (BTP) said.

Extinction Rebellion said the disruption was "necessary to highlight the emergency".

One commuter shouted at protesters on the top of the Tube train: "I have to get to work too - I have to feed my kids."

In a statement BTP said: "We continue to urge protesters to not target the London Underground network. This is dangerous, not only for protesters but for commuters.

"We have increased our patrols on the London Underground and at other rail hubs throughout London."

Analysis
By Tom Edwards, BBC London transport correspondent
Even from within Extinction Rebellion there has been disagreement on targeting public transport - particularly London's Tube and DLR which are pretty efficient, very well-used and low carbon.

Many think public transport is the part of the solution to achieving net zero-carbon transport systems.

By targeting the transport network, protesters are confusing their messages.

However, you have to remember Extinction Rebellion is a decentralised umbrella term for lots and lots of smaller groups and as such they have differing methods - some more radical than others - and can operate independently.

And - ultimately - what they want is publicity for the cause.

Extinction Rebellion co-founder Clare Farrell defended the Tube action, saying "the public, I don't think, realise quite how serious this situation is".

What is Extinction Rebellion and what does it want?

Speaking to BBC Radio 4's Today programme, she added: "It is still peaceful, and it is still non-violent.

"It makes them vulnerable, and that's what people are there to do when they put their body on the line."

Mayor of London Sadiq Khan said in a statement: "I strongly condemn the Extinction Rebellion protesters who have targeted the London Underground and DLR this morning.

"This illegal action is extremely dangerous, counterproductive and is causing unacceptable disruption to Londoners who use public transport to get to work."

Train drivers' union Aslef said the Tube and other public transport were "part of the solution to climate change, not the problem".

Extinction Rebellion should "stick to protesting against those who create the problem - not our industry, members and hard-working commuters", the union added.

A public order ban has been put in place on Extinction Rebellion activities in London since Monday.

In response, Extinction Rebellion called on "all London rebels and friends" to defy the ban.
Were you at one of the affected stations? Share your experiences by emailing haveyoursay@bbc.co.uk
Please include a contact number if you are willing to speak to a BBC journalist. You can also contact us in the following ways:

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Climate protesters dragged from Tube train

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Commuters have dragged climate change protesters from the roof of a London Underground train. Extinction Rebellion activists climbed on top of trains at Stratford, Canning Town and Shadwell during Thursday's rush hour. The Jubilee Line and Docklands Light Railway were earlier partially suspended. Minor delays are still reported on the lines.

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Whale Fall Actively Devoured by Scavengers at Davidson Seamount | Nautilus Live

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During the final dive of this year's Nautilus expedition season, our team discovered a whale fall while exploring Davidson Seamount off central California's coast with researchers from Monterey Bay National Marine Sanctuary. The skeletal remains of the whale lying on its back are estimated to be 4-5 meters long. The team is working to identify the species, but it is confirmed to be a baleen whale as indicated by baleen remaining along the whale's jawbones.

While evidence of whale falls have been observed to remain on the seafloor for several years, this appears to be a relatively recent fall with baleen, blubber, and some internal organs remaining. The site also exhibits an interesting mid-stage of ecological succession, as both large scavengers like eel pouts are still stripping the skeleton of blubber, and bone-eating Osedax worms are starting to consume lipids (fats) from the bones. Other organisms seen onsite include crabs, grenadier, polychaetes, and deep-sea octopus.

Learn more about this expedition.

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Whale Fall Actively Devoured by Scavengers at Davidson Seamount

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During the final dive of this year's Nautilus expedition season, our team discovered a whale fall while exploring Davidson Seamount off central California's coast with researchers from Monterey Bay National Marine Sanctuary. The skeletal remains of the whale lying on its back are estimated to be 4-5 meters long.

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Microplastics: Seeking the 'plastic score' of the food on our plates https://www.bbc.co.uk/news/science-environment-49798057

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Elizabeth Warren Cuts Through the Dumbest Climate Argument - YouTube

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Elizabeth Warren's husband speaks out in rare interview

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Portraits d’atomes : le fluor, pour les dents, les os et... les poêles

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Atomes, portraits de familles (4/9). Dans le tableau périodique des éléments, créé par Dmitri Mendeleïev, il y a 150 ans, le fluor affiche des propriétés très réactives au sein la singulière colonne des halogènes.

Article réservé aux abonnés

Toute règle a ses exceptions. Même pour de vénérables institutions comme le tableau périodique des éléments de Mendeleïev. Chaque atome d'une même colonne a une structure électronique semblable, et, a priori, des propriétés chimiques proches.

Sauf que l'avant-dernière colonne, celles des halogènes, fluor, chlore, brome... s'écarte un peu de cette règle. A température et pression standards, le fluor est un gaz jaunâtre irritant et très agressif. Le chlore, lui, vire au vert et est assez suffocant. Et le brome est un liquide rouge avec une odeur piquante.

Autre exemple. Le terme " halogène " signifie générateur de sel, comme le rappelle Pierre Avenas dans son livre, La Prodigieuse histoire du nom des éléments (EDP Sciences, 2019). Mais les sels obtenus n'ont pas les mêmes propriétés. Le chlorure de sodium est l'anodin sel de cuisine, le bromure de sodium a des propriétés somnifères, l'iodure de sodium réduit les carences en iode et le fluorure de sodium renforce l'émail des dents.

Gagnant

Ce n'est pas tout, ces atomes très réactifs s'associent avec le carbone avec plus ou moins de force. A ce jeu, le fluor gagne, avec une liaison plus importante que celle entre le carbone et l'hydrogène. Plus on descend dans la colonne, moins la liaison est forte, au point que celle entre l'iode et le carbone est même instable.

Cela explique la singularité du fluor dans cette famille. Il est si réactif qu'il fut le dernier de la colonne à être isolé, par Henri Moissan, en 1886, couronné par un Nobel en 1906. Son nom vient du latin fluere (écoulement), car la fluorine, association de calcium et de fluor, fluidifie les minerais à la base de la fabrication d'aluminium. Mais grâce à l'énergie nucléaire, l'industrie du fluor se développe avec de nouvelles applications dans les matériaux et la santé.

Fluorine sur quartz . Didier Descouens / CC BY-SA 3.0

Dans les centrales nucléaires, on utilise des atomes d'uranium dits fissiles. Cette forme étant rare dans la nature, il faut fabriquer un combustible enrichi en forme fissile. L'uranium est donc " fluoré " pour faciliter la séparation entre les deux formes d'uranium. Cela a contribué au développement d'une industrie du fluor qui a trouvé d'autres débouchés.

De nouveaux matériaux polymères, profitant de la force des liaisons carbone-fluor, ont été élaborés comme les célèbres Téflon ou le Gore-Tex. Revers de la médaille, un solvant fluoré utilisé dans ces fabrications, le PFOA, est un perturbateur endocrinien très peu biodégradable. L'Union européenne le mettra à l'index en 2020.

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Portraits d'atomes : le fluor, pour les dents, les os et... les poêles

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Atomes, portraits de familles (4/9). Dans le tableau périodique des éléments, créé par Dmitri Mendeleïev, il y a 150 ans, le fluor affiche des propriétés très réactives au sein la singulière colonne des halogènes. Article réservé aux abonnés Toute règle a ses exceptions. Même pour de vénérables institutions comme le tableau périodique des éléments de Mendeleïev.

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Parisians fight climate change with a surprising weapon - BBC News

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Parisians fight climate change with a surprising weapon

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An initiative in Paris is trying to persuade restaurants to turn food waste into compost.

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The One Science Lesson Every American Adult Can Learn From Greta Thunberg

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Like most people on Earth, Greta Thunberg is not a climate scientist. She has no formal scientific training of any type, nor does she possess any expert-level knowledge or expert-level skills in this regime. She has never worked on the problems or puzzles facing environmental scientists, atmospheric scientists, geophysicists, solar physicists, climatologists, meteorologists, or Earth scientists.

Like most of us, she is an ordinary citizen of the world: with strong beliefs, opinions, and political inclinations. But unlike most of us, Greta has shown a willingness to do what most of us refuse to do. Her starting point for how to move forward in the world is to begin from a position of scientific consensus. While most of us prefer to be given the facts and trust that we, intelligent as we are, can figure it out for ourselves, Greta recognizes the unparalleled value that scientific expertise brings to our world.

It's true that there are many scientific conclusions that are only provisional, and that much of what we conclude is accurate today may be overturned by superior evidence in the future. The way science proceeds is by constantly re-evaluating your theories, ideas and hypotheses in the face of the ever-changing full suite of evidence. When the evidence contradicts the theory, the theory must be thrown out, modified, or otherwise revised.

But when the evidence lines up with the theory's predictions, it provides confirmation and validation that we're at least on a thoroughly reasonable path. This is how scientists in all fields, whenever they're doing good science, proceed. It applies to any issue you can imagine, from vaccinations to fluoridation to evolution to dark matter to the Big Bang and more. And yes, it also applies to global warming and, more generally, to the field of climate science.

Colloquially, in non-scientific parlance, most of us might view the idea of consensus the same way Margaret Thatcher did: as a dirty word that describes abandoning our principles to achieve a politically expedient agreement. As Thatcher put it,

Consensus: "The process of abandoning all beliefs, principles, values, and policies in search of something in which no one believes, but to which no one objects; the process of avoiding the very issues that have to be solved, merely because you cannot get agreement on the way ahead. What great cause would have been fought and won under the banner: 'I stand for consensus?"

But to a scientist, consensus means something very different. Consensus is not a compromise; it's not a fact-free matter of opinion; and it's certainly not immune to challenge. Instead, the consensus is our starting point: the point that all reasonable scientists in a field can agree on.

Scientific consensus is not some made-up, subjective term that you can manufacture. It's vital that the consensus be challenged continuously, and contrarian ideas are always welcome to make concrete predictions that differ from the mainstream ones; if the decisive data comes in and conflicts with the consensus positions, perhaps the contrarian idea may even rise to replace the current consensus.

It's necessary, if we care about science progressing, that we subject every assumption and conclusion we've drawn to meet the challenges posed by new data, methods, and observations. In this regard, scientists who challenge the consensus play an enormous role in probing at the cracks in any prevailing theory. Most often, the theory holds up, but every so often, a revision or even an overhaul is necessary, marking a significant shift in any scientific field.

Most people recognize that these things are true when it comes to science. What Greta Thunberg has to teach us, that most people (perhaps even most scientists) fail to grasp, is that the scientific expertise you learn in the process of becoming a scientist is what enables you to make informed judgments about the merits of various scientific assertions. And, if you care about achieving the most desirable outcome, you must accept the best science the world has to offer - the scientific consensus on an issue, where one exists - or you don't deserve a seat at the table.

A scientific consensus doesn't pop up overnight, or in places where there are legitimate scientific controversies with multiple, equally good explanations. It's why every physicist agrees on what you'll see when you perform a double-slit experiment (there is consensus), but physicists don't agree on which interpretation of quantum mechanics is preferable (there is no consensus).

A consensus will only arise when a theory is good enough to make predictions that are robust, verified by multiple lines of evidence, backed up by a statistically significant amount of data, and where definitive observations have been taken that discern one particular theory's predictions from the others.

It's why General Relativity is the consensus theory of gravity, but also why we continue to challenge it with new observations in regimes where it hasn't yet been tested.

It's why evolution, via the mechanism of genetic mutation and natural selection, is the consensus theory on the origin of the species currently found on Earth.

It's why vaccination and fluoridation are overwhelmingly recommended by public health experts as near-universal goods, while vitamins are only recommended for those with nutritional deficiencies.

And it's why, in the field of climate science, it is overwhelmingly accepted that the world is warming and human modification of our natural environment - largely through the burning of fossil fuels - is the primary cause. It is also part of the consensus that this warming is altering the climate, increasing the frequency and maximum severity of extreme weather events, and is disproportionately impacting coastal and sea-level regions.

The consensus position only includes those points we can confidently state are true. For example, there is an overwhelming consensus about certain features of climate models, but other features have large uncertainties which haven't led to a consensus. But what has occurred, overwhelmingly, is that motivated groups, individuals and industries have engaged in a serious, sustained misinformation campaign, and it has been very persuasive.

A survey from earlier this month shows that, among 28 surveyed countries, the United States of America ranks highest in the percentage of citizens who deny the existence of climate change. 6% of Americans deny that the climate is changing, even though earlier this decade the annual temperature record surpassed the 5-sigma statistical significance threshold: the gold standard in particle physics; for an environmental science result to cross that threshold is almost unheard of.

Moreover, another 9% deny that humans are responsible for climate change, even though the various contributing factors (the Sun, volcanoes, cloud cover and global dimming, etc.) have been well quantified.

What Greta Thunberg gets, and the important lesson she has for all of us, is this. The science has been unambiguous since the late 1980s: the Earth is warming, humans are the cause, and the only way to combat this is through large-scale action taken by our world's governments. The largest contributors to the causes of climate change - the addition of greenhouse gases to our planet's atmosphere - come from just a few dozen corporations. In particular, 71% of all the emissions from 1980 to 2015 come from just 100 companies, practically all of which are fossil fuel producers.

Yet our governments are failing us. They are instead misrepresenting the science and coming to the table dishonestly and disingenuously, planting red herrings to undermine the actual consensus, strawmanning and working to de-fund and devalue the existing knowledge on climate science, sowing doubt in places where there is none on scientific merits, and demanding party loyalty over reason and science.

It's a free world and a free country, and no one can stop you from believing whatever you want. You can believe that vaccines cause autism, that the Earth is flat, that humans never walked on the Moon, and that global warming is a hoax. But if you believe any of those things, you are choosing an unsubstantiated and anti-science conspiracy that, when confronted with the actual evidence humanity possesses, doesn't have a legitimate leg to stand on.

For decades, politicians have commanded scientists to stick to their science and not enter conversations about science and society. Yet we live in a world where some of the most powerful nations are governed by inherently anti-science attitudes. Science has already carried the day when it comes to global warming and climate change; now is the time to be an adult and address the real changes humanity has brought upon planet Earth.

There is an overwhelming scientific conclusion being ignored by the entire world. For decades, scientists have sounded the alarm, only to be met by a government that complains about the volume and tone of the alarm while ignoring the contents of the message. The time for arguing over whether this problem is real, severe, or our fault is long past.

It's time for real action, and long past time to vote out any impostors that can't get on board with the scientific consensus. Every one of us has a voice and a vote, and we cannot let these obstructionist tactics obscure the truth any longer. There's a real problem here, and while fixing it will be a long-term endeavor, we all know where to start: by accepting the truth and considering solutions that address the scientifically legitimate issue at stake. If we can't at least take that step, we're dooming future generations to the worst possible climate scenario. We're capable of preventing that outcome. Whether we do or not depends entirely on what we do next.

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The One Science Lesson Every American Adult Can Learn From Greta Thunberg

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Like most people on Earth, Greta Thunberg is not a climate scientist. She has no formal scientific training of any type, nor does she possess any expert-level knowledge or expert-level skills in this regime. She has never worked on the problems or puzzles facing environmental scientists, atmospheric scientists, geophysicists, solar physicists, climatologists, meteorologists, or Earth scientists.

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Are Cities for People or Cars ? - YouTube

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Global Climate Strike: The best signs from Friday's protests around the world.

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1. Six Ex-Government Scientists Explain What It Was Like to Work for Trump

2. The President Who Wanted Us to Stop Climate Change

3. Artificial Intelligence Has a Huge Carbon Footprint. But It Doesn't Have To.

4. Teens Explain Why They're Striking for Climate Action Today

This piece has been published as part of Slate's partnership with Covering Climate Now, a global collaboration of more than 250 news outlets to strengthen coverage of the climate story.

Millions of people in cities around the world took to the streets Friday to call for immediate climate action. A large portion of those protesters are teenagers and schoolchildren, inspired in part by the Swedish environmental activist Greta Thunberg, whose group, Fridays for Future, led students to skip school on Fridays to go on strike. Thunberg, who is now 16, has said that more than 4,600 events in nearly 140 countries had been scheduled for this week's climate strike. The event appears to have grown even more than anticipated, and more than 150 countries have reportedly seen climate events.

Here are some of the best signs from Friday's march.

Demands for a Future
﻿It's no surprise that young marchers' frustration and anger over the complacency of older generations powered much of the movement. On Friday, those young people made it clear they don't plan to stop fighting for their own say.

Pleas From the Very Young
Some of the most powerful signs on Friday came from the youngest protesters.

Thanks to Greta
Thunberg, the hero of the movement, was invoked often as a rallying cry for action.

No Thanks to Donald
While he wasn't the only politician targeted by the signs, President Donald Trump was a subject of anger in derision in more than just the U.S. marches.

Marching in Costume
A number of protesters got into character to deliver their message.

Anger Through Comedy
The situation may be serious, but some brought some (righteously angry) humor to the scene.

Telling It Like It Is
The point of the day was to remind lawmakers that climate change calls for urgent action. Children and teenagers delivered with a mix of innocent politeness and gleeful vulgarity, but the point was the same: We're here because you're not doing enough.

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The Best Signs From the Global Climate Strike

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Six Ex-Government Scientists Explain What It Was Like to Work for Trump The President Who Wanted Us to Stop Climate Change Artificial Intelligence Has a Huge Carbon Footprint. But It Doesn't Have To.

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L'US Navy confirme l'authenticité de vidéos d'ovni - Sciences et Avenir

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Ces vidéos, au nombre de trois, avaient été diffusées sur les médias américains à partir de décembre 2017. Elles avaient été mises en ligne par l'organisation TTSA (To The Stars Academy of Arts & Science) fondée par le musicien Tom DeLonge du groupe Blink 182 et dédiée à la recherche sur les phénomènes ufologiques. A l'époque, l'armée américaine n'avait pas commenté cette fuite ni même confirmé que les images provenaient bien d'avions de chasse.

Des "phénomènes aériens non identifiés"

C'est désormais chose faite. Un porte-parole de l'US Navy a reconnu lors d'un échange de mails avec un journaliste du site The Black Vault que ces images étaient bien authentiques et que l'armée enquêtait sur les étranges lueurs y apparaissant ; elles stupéfient même les pilotes qui les observent. L'armée ne parle toutefois pas d' Ovnis mais de "Phénomènes aériens non-identifiés" (UAP) se déroulant dans l'espace aérien des Etats-Unis. Elle précise aussi que les investigations sont toujours en cours et que à priori le grand public ne sera pas mis au courant des conclusions, sécurité du pays oblige.

La première des trois vidéos, baptisée "FLIR1" est ancienne : elle date de 2004 et était déjà apparue sur quelques sites spécialisés dès 2007. On parle également d'elle comme de "l'incident du Nimitz", un porte-avion et navire amiral du groupe aéronaval Carrier Strike Group 11. Elle a été filmée par un F/A-18 Super Hornet, le 14 novembre, au large de San Diego.

"Look at that thing, dude!"

Les deux autres séquences "Gimbal" et "GoFast" ont été tournées le 21 janvier 2015, selon la date communiquée par l'armée US, et toutes deux proviennent des enregistrements de F/A-18 Super Hornet. Les deux scènes ont pu être filmées au large de Jacksonville et il pourrait s'agir de deux prises de vues d'un même évènement mais la Navy ne confirme aucune de ces informations.

On entend clairement l'étonnement des pilotes qui poursuivent ces formes bizarres qui semblent se mouvoir de façon tout à fait inhabituelle pour un engin aérien. Les pilotes pensent eux être en face d'un drone, comme ils l'expriment.

Dans cette dernière séquence on voit une forme lumineuse ovoïde se déplaçant à grande vitesse et finalement piégée par le système de capture automatique ATFLIR de l'avion. Là aussi les pilotes n'arrivent pas à identifier l'objet qu'ils ont sous les yeux.

En France, on a les PAN

Aucun officiel de l'armée US n'a jamais fait allusion à une quelconque activité "extraterrestre", ni même les pilotes dans le feu de l'action. Mais les ufologues du monde entier se réjouissent de la confirmation de l'authenticité de ces images. Rappelons que dans les années 1950, de nombreux pilotes de chasse avaient aussi rapporté l'observation d'" ovnis" et que l'armée avait enquêté sur ces manifestations dans le cadre d'une opération baptisée "Blue Book". Finalement, il s'est avéré que les ovnis étaient des avions-espions testés par la CIA dans le cadre d'un programme d'espionnage de l'ex-URSS.

En France, on ne parle pas non plus d'ovnis mais plutôt de PAN pour "Phénomènes Aérospatiaux Non identifiés", une dénomination proche de celle employée par les Etats-Unis. C'est le GEIPAN (Groupe d'Études et d'Information sur les Phénomènes Aérospatiaux Non Identifiés) qui est chargé d'étudier les observations rapportées. Il dépend du CNES et est composé d'enquêteurs et d'experts bénévoles. Actif depuis l'après-guerre, le GEIPAN archive chacune des observations récoltées par son réseau et notamment celles qui au final n'ont pu être explicitées.

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Ovnis : l'US Navy confirme avoir filmé des phénomènes aériens non identifiés

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Ces vidéos, au nombre de trois, avaient été diffusées sur les médias américains à partir de décembre 2017. Elles avaient été mises en ligne par l'organisation TTSA (To The Stars Academy of Arts & Science) fondée par le musicien Tom DeLonge du groupe Blink 182 et dédiée à la recherche sur les phénomènes ufologiques.

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World Oceans Day is a global celebration on June 8 with hundreds of events around the world celebrating our ocean.

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Researchers discover climate-friendly way of extracting hydrogen from oil

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The Canadian researchers say that their method of extracting hydrogen directly from oil sands and oil fields leaves gases such as carbon dioxide and methane in the ground. Furthermore, the process is considerably more economical than existing methods. According to the team, which unveiled its research at the Goldschmidt Geochemistry Conference in Barcelona, the method could produce hydrogen at between $0.10-0.50 per kilo, compared with the current production cost of around $2 per kilo.

"Low-cost hydrogen from oil fields with no emissions can power the whole world using mostly existing infrastructure," Grant Stem, CEO of Proton Technologies, which is commercialising the extraction method, told AFP. "This is the silver bullet for clean energy and clean climate." Steam added that the technology has the potential to supply Canada's entire electricity requirement for the next 330 years.

The development could have a significant impact on the role hydrogen plays in the fight against climate change, although some experts remain guarded. Professor Brian Horsfield from the GFZ German Research Centre for Geosciences to AFP that extensive field testing would be needed to see how the system works on an industrial scale. However, he nevertheless called the project "highly innovative and exciting."

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Researchers discover climate-friendly way of extracting hydrogen from oil

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The Canadian researchers say that their method of extracting hydrogen directly from oil sands and oil fields leaves gases such as carbon dioxide and methane in the ground. Furthermore, the process is considerably more economical than existing methods.

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Climate change: Should you fly, drive or take the train? - BBC News

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The climate campaigner Greta Thunberg chose to sail to a UN climate conference in New York in a zero-emissions yacht rather than fly - to highlight the impact of aviation on the environment. The 16-year-old Swede has previously travelled to London and other European cities by train.

Meanwhile the Duke and Duchess of Sussex have faced criticism over opting to fly to Sir Elton John's villa in Nice in a private jet.

So what is the environmental impact of flying and how do trips by train, car or boat compare?

What are aviation emissions?

Flights produce greenhouse gases - mainly carbon dioxide (CO2) - from burning fuel. These contribute to global warming when released into the atmosphere.

An economy-class return flight from London to New York emits an estimated 0.67 tonnes of CO2 per passenger, according to the calculator from the UN's civil aviation body, the International Civil Aviation Organization (ICAO).

That's equivalent to 11% of the average annual emissions for someone in the UK or about the same as those caused by someone living in Ghana over a year.

And as other sectors of the economy become greener - with more wind turbines, for example - aviation's proportion of total emissions is set to rise.

How do emissions vary?

It depends where passengers sit and whether they are taking a long-haul flight or a shorter one.

The flight figures in the table are for economy class. For long haul flights, carbon emissions per passenger per kilometre travelled are about three times higher for business class and four times higher for first class, according to the Department for Business, Energy and Industrial Strategy (BEIS).

This is because there's more space per seat, so each person accounts for a larger amount of the whole plane's pollution.

Taking off uses more fuel than cruising. For shorter flights, this accounts for a larger proportion of the journey. And it means lower emissions for direct flights than multi-leg trips.

For private jets, although the planes are smaller, the emissions are split between a much smaller number of people.

The increased warming effect other, non-CO2, emissions, such as nitrogen oxides, have when they are released at high altitudes can also make a significant difference to emissions calculations.

"The climate effect of non-CO2 emissions from aviation is much greater than the equivalent from other modes of transport, as these non-CO2 greenhouse gases formed at higher altitudes persist for longer than at the surface and also have a stronger warming potential," Eloise Marais, from the Atmospheric Composition Group, at the University of Leicester, told BBC News.

But there is scientific uncertainty about how this effect should be represented in calculators.

The ICAO excludes it, while the BEIS includes it as an option - using a 90% increase to reflect it.

The EcoPassenger calculator - launched by the International Railways Union in cooperation with the European Environment Agency - says it depends on the height the plane reaches.

Longer flights are at higher altitude, so the calculator multiplies by numbers ranging from 1.27 for flights of 500km (300 miles) to 2.5 for those of more than 1,000km.

In the chart above, the high-altitude, non-CO2 emissions are in a different colour.

Train virtually always comes out better than plane, often by a lot. A journey from London to Madrid would emit 43kg (95lb) of CO2 per passenger by train, but 118kg by plane (or 265kg if the non-CO2 emissions are included), according to EcoPassenger.

However, the margin between train and plane emissions varies, depending on several factors, including the type of train. For electric trains, the way the electricity they use is generated is used to calculate carbon emissions.

Diesel trains' carbon emissions can be twice those of electric ones. Figures from the UK Rail Safety and Standards board show some diesel locomotives emit more than 90g of C02 per passenger per kilometre, compared with about 45g for an electric Intercity 225, for example.

The source of the electricity can make a big difference if you compare a country such as France, where about 75% of electricity comes from nuclear power, with Poland, where about 80% of grid power is generated from coal.

According to EcoPassenger, for example, a train trip from Paris to Bordeaux (about 500km) emits just 4.4kg of carbon dioxide per passenger, while a journey between the Polish cities of Gdansk and Katowice (about 465km) emits 61.8kg.

As with plane journeys, another factor is how full the train is - a peak-time commuter train will have much lower emissions per person than a late-night rural one, for example.

Yes, if the car's electric - but diesel and petrol cars are also in many cases better options than flying, though it depends on various factors, particularly how many people they're carrying.

According to EcoPassenger, a journey from London to Madrid can be done with lower emissions per passenger by plane, even accounting for the effect of high altitude non-CO2 emissions, if the car is carrying just one person and the plane is full. If you add just one more person into the vehicle, the car wins out.

What about travelling by boat?

The BEIS has also put a figure on ferry transport - 18g of CO2 per passenger kilometre for a foot passenger, which is less than a coach, or 128g for a driver and car, which is more like a long-haul flight.

But ferries' ages and efficiency will vary around the world - and a ferry won't get you to America, although a cruise ship or ocean liner would.

The cruise industry has long been under pressure to reduce environmental impacts ranging from waste disposal to air pollution, as well as high emissions - not only from travel but also from powering all the on-board facilities.

And, while the figures are not directly comparable, they suggest cruising falls in similar territory to flying in terms of emissions.

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Climate change: Should you fly, drive or take the train?

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How should you travel to reduce your carbon footprint?

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Ask Ethan: Where Is The Center Of The Universe?

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There are two things that people learn about the Universe that surprise them more than any other: that the Universe hasn't existed forever but only for a finite time since the Big Bang, and that it's been expanding ever since that event took place. Most people intuitively hear that "bang" and picture an explosion, and then conceive of expansion like they would visualize shrapnel hurled outwards in all directions. It's true that the matter and energy in the Universe began in a hot and dense state all at once, and then expanded and cooled as all the various components sped away from one another. But that doesn't mean the "explosion" picture is correct. We got a very good question from Jasper Evers, who ponders:

I am wondering how there isn't a center of the universe and how the cosmic background radiation is [equally] far away everywhere we look. It seems to me that when the universe expands... there should be a place where it started expanding.

After all, what this question is asking is exactly what aligns with our experience whenever we encounter an explosion.

Whenever you have an explosion, regardless of whether it's based on a combustion reaction, a nuclear explosion, a rupture caused by overpressurizing a container, etc., the following things are true.

An explosion always begins at a specific location in space.

An explosion initially occupies a small but finite volume.

And an explosion expands rapidly outward in all directions, limited only by the external forces and barriers it encounters.

When you have an explosion, some material will often be caught up and/or affected by it, and will be pushed radially outward, with some of that material (typically the lightest stuff) moving outward the fastest. That fastest-moving material will spread out more quickly and farther than the rest of the material, and will become less dense as a result. Even though the energy density drops everywhere, it drops fastest farthest away from the explosion, because more energetic material becomes less dense faster: at the outskirts. Just by measuring the trajectories of these different particles, you can always reconstruct where the explosion occurred.

But this picture I've just painted for you - of an explosion - doesn't match up with our Universe. The Universe looks the same here as it does a few million or even a few billion light-years away. It has the same densities, the same energies, the same number of galaxies in a given volume of space, etc.

The objects that are very far away do indeed appear to move away from us at greater speeds than the nearby objects, but they also don't appear to be the same age as the slower, closer objects. Instead, as we go to extreme distances, the farther ones appear younger, less evolved, greater in number, and smaller in size and mass. Despite the fact that we can see galaxies out to distances in excess of 30 billion light-years, if we track how everything is moving and reconstruct their trajectories back to a common origin, we see the most unlikely of outcomes: the perceived "center" lands right on us.

Our of all the trillions of galaxies in the Universe, what are the odds that we would just happen to be right at the center of the explosion that began the Universe? What are the odds, on top of those minuscule ones, that the initial explosion was configured in just such a way, complete with

irregular, inhomogeneous densities,

varying start times for star formation and galaxy growth,

energies that vary tremendously from place-to-place in just the right, fine-tuned fashion,

and a mysterious 2.7 K background glow in all directions,

to conspire so that we're exactly at the center? There's a lot we'd have to contrive to explain this, and many observations would still remain inexplicable. The explosion scenario isn't just unrealistic; it's in defiance of the known laws of physics.

Instead, however, the law of gravity that governs our Universe - Einstein's General theory of Relativity - predicts that a Universe full of matter and energy doesn't explode, but instead expands. A Universe that's full of equal amounts of stuff everywhere, with the same average densities and temperatures, must either expand or contract; since we observe an apparent recession, the expansion solution is the only one that's physical. (The same way that the square root of 4 can be either +2 or -2, but only one of those will correspond to the physical number of apples in your hands.)

There's a misconception that an expanding Universe can be extrapolated back to a single point; this isn't true! Instead, it can be extrapolated back to a region of finite size with certain properties (i.e., filled with matter, radiation, the laws of physics, etc.), but then must evolve according to the rules that our theory of gravity lays out.

What this leads to, inevitably, is a Universe that has similar properties everywhere. This means that in any finite, equally-sized region of space, we should see the same density to the Universe, the same temperature to the Universe, the same number of galaxies, etc. We'd also see a Universe that appeared to evolve with time, as more distant regions should appear to us as they were in the past, having expanded less and having experienced less gravitational attraction and smaller amounts of clustering.

Because the Big Bang happened everywhere at once a finite amount of time ago, our local corner of the Universe will appear to be the oldest corner of the Universe that there is. From our vantage point, what appears to us nearby is almost as old as we are, but what appears at great distances is much more similar to what our nearby Universe was like many billions of years ago.

The distant galaxies that exist are constantly emitting light, and we are seeing the light that has arrived only after it has completed its journey to get to us through the expanding Universe. Galaxies whose light took a billion or ten billion years to get here appear as they were a billion or ten billion years ago. If we go all the way back, towards almost the moment of the Big Bang itself, we'd find that the Universe when it was that young was dominated by radiation, and not matter. It has to expand and cool for matter to become more important, energy-wise.

Over time, as that Universe expands and cools, neutral atoms can finally, stably form without being immediately blasted apart. The radiation that once dominated the Universe, however, still persists, and continues to cool and redshift due to the expansion of space. What we perceive today as the Cosmic Microwave Background is consistent with being the leftover glow from the Big Bang, but is also observable from anywhere in the Universe.

There isn't necessarily a center to the Universe at all; it's only our biased intuition that tells us there ought to be one. We can set a lower limit on the size of the region where the Big Bang must have occurred - it can be no smaller than the size of a soccer ball or so - but there is no upper limit; the region of space where the Big Bang occurred could even have been infinite.

If there truly is a center, it could literally be anywhere, and we would have no way to know. The portion of the Universe that is observable to us is insufficiently large to reveal that information, even if it could be true. We'd need to see an edge to the Universe (we don't), or observe a fundamental anisotropy where different directions appear different (but we see the same temperatures and galaxy counts), and we'd need to see a Universe that appeared to be different from region-to-region on the largest cosmic scales (but it appears to be homogeneous instead).

It sounds so reasonable to ask the question, "where did the Universe begin expanding from?" But once you realize all of the above, you'll recognize that's the wrong question entirely. "Everywhere, all at once," is the answer to that question, and that's largely because the Big Bang isn't referring to a special location in space, but rather a special moment in time.

That's what the Big Bang is: a condition that affects the entire observable Universe - and possibly a much, much larger region than that - all at once at one specific moment. It's the reason why looking at objects that are farther away in space means that we're seeing that object as it was at a moment in the distant past. It's why all directions appear to have rough properties that are uniform regardless of where we look. And it's why we can trace back our cosmic history, through the evolution of the objects we see, as far back as our observatories enable us to go.

Despite all that we have access to - despite all that our theories and observations tell us - there's still a tremendous amount that remains unknown to us. We don't know what the actual size of the entire Universe is; we only have a lower limit that it must now be at least 46.1 billion light-years in radius in all directions from our perspective.

We don't know what the shape of the fabric of space is, and whether it's positively curved like a sphere, negatively curved like a saddle, or perfectly flat, like a sheet or a cylinder. We don't know whether it curves back on itself or whether it goes on forever. All that we know is based on all we can observe. From that information, we can conclude that it's consistent with being infinite in size, it's consistent with perfect flatness, but information to the contrary may lie in the next significant digit of data or just beyond our observable cosmic horizon. It's vital that we keep looking.

The reason we cannot know the true nature of the Universe - the entire, unobservable Universe - is because the portion that we have access to is finite. There's a finite amount of information we're capable of gleaning about our cosmos, even if we develop arbitrarily powerful instruments and detectors. It's eminently plausible that even if we wait an infinite amount of time, we'll never know whether the Universe is finite or infinite, or what its geometric shape is.

Whether you view the fabric of space as a leavening loaf of raisin bread or an expanding balloon with coins glued to the surface, you must keep in mind that the part of the Universe we can access is likely only a tiny component of whatever it is that actually exists. What's observable to us only sets a lower limit on the entirety of what's out there. The Universe could be finite or infinite, but the things we're certain of is that it's expanding, getting less dense, and that more distant objects appear as they were a long time ago. As astrophysicist Katie Mack notes:

The Universe is expanding the way your mind is expanding. It's not expanding into anything; you're just getting less dense.

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Ask Ethan: Where Is The Center Of The Universe?

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There are two things that people learn about the Universe that surprise them more than any other: that the Universe hasn't existed forever but only for a finite time since the Big Bang, and that it's been expanding ever since that event took place.

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Amazon Fire tablet upstages Amazon rainforest fires on Google

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Right now, if you search for news about the massive fires burning in the Amazon rainforest, you might mostly find stories about the Amazon Fire line of tablets and streaming devices.

The search results come at a critical time for the rainforest. Smoke from the fires, which as of this afternoon cover huge swaths of the Amazon basin, completely blotted out the midday sun in Sao Paulo this week, darkening the city at 2:00pm on Monday (Aug. 19). According to Brazil's state satellite agency, the number of fires in the Amazon so far this year is up 85% compared to the same period last year. About half of this year's blazes have occurred in the last 20 days.

Meanwhile, many of the headlines in Google News highlight "midweek deals" on older models of Amazon's Fire tablet and reviews of the latest version of the device. Searches for both "amazon fire" and "fire in the amazon" on Aug. 21 turned up news stories about the products rather than the fires; in one search, news stories about the ongoing Amazonian fires didn't appear until the second page of Google News results.

Google News search results for "Amazon fire," queried on August 21, 2019.

Amazon Watch, one prominent NGO dedicated to advancing the rights of indigenous people living in the Amazon basin, has called on Jeff Bezos and his company to direct some efforts towards protecting its namesake ecosystem in the past. (Bezos installed a model "rainforest" in Amazon's Seattle headquarters last year.)

Google News search results for "fire in the Amazon," queried on August 21, 2019.

The rainforest has suffered ongoing deforestation over the last 50 years, with about one-fifth of the ecosystem cut and burned to make way for logging, ranching, or mining. The fires burning in the Amazon basin are likely set by people in an attempt to clear land for cattle ranching.

Ranchers, loggers, and miners have reportedly been emboldened by Brazilian president Jair Bolsonaro's open disdain for conservation, and his support for using the rainforest for industry. Hundreds of thousands of indigenous people in more than 400 tribes live in the Amazon, and many already struggle to protect their land from illegal invasion. "We know what happens when the state does nothing," Marcelino Da Silva, a member of the Apurinã tribe in the Brazilian Amazon, told the Intercept last month. "We know how quickly the forest can disappear."

Deforestation has accelerated in recent years, reaching a peak last month at a rate of more than three football fields a minute, leading scientists to publicly worry that it could be approaching a tipping point; past a certain point of deforestation, the rainforest could be in jeopardy of degrading into a savannah.

Every section of the rainforest lost means losing natural carbon sinks; the greenhouse gas locked up by the forest's biomass is instead released into the atmosphere, accelerating global climate change. Losing it also means losing the habitats for numerous threatened plant and animal species, many of which can only be found in the biodiverse Amazon.

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Why you won't see much news about the devastating Amazon rainforest fires on Google

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Right now, if you search for news about the massive fires burning in the Amazon rainforest, you might mostly find stories about the Amazon Fire line of tablets and streaming devices. The search results come at a critical time for the rainforest.

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Beaches choked with stinky seaweed could be the new normal - Environment - The Jakarta Post

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Slimy, stinky brown seaweed that ruins beachgoers' vacations from Mexico to Florida may be the new normal unless Brazil halts Amazon deforestation, experts say.

The culprit, called sargassum, turns clear-blue sea water a murky brown and smells like rotten eggs when it washes ashore and starts to rot.

The seaweed is a natural occurrence on beaches in the Caribbean and elsewhere. It's part of an ecosystem for fish, crabs and birds.

But it has proliferated dramatically in recent years, covering shores with thick layers of the weed and forcing tourism officials to clean it up so visitors keep coming.

It is an icky nuisance for tourists and an economic and environmental disaster.

"We came from over there, looking for a spot that is cleaner. But it is this way everywhere," said Maria Guadalupe Vazquez, 70, pointing off into the horizon as she lounges in a beach chair in Miami Beach.

Authorities brought in trucks and front-loaders Friday to scoop the stuff up and haul it away. They know this is no long-term solution, however.

One problem is global warming -- the hotter the ocean, the more these weeds reproduce, said Steve Leatherman, an environmental expert at Florida International University.

But the bigger problem is the Amazon river, he added.

Scientists say that starting around 2011, much more land along that mighty waterway was cleared for farming.

But it yields a poor, muddy red soil so farmers use a lot of fertilizer, which rains wash into the river, where it flows into the Atlantic. And the fertilizer ends up fertilizing the sargassum.

"Now there's 20, or 30, 50 times more, 100 times more than we've ever had before," said Leatherman.

"We think this is going to be the new normal so we are going to have to find a way to deal with this, and it's going to be difficult," said Leatherman, aka Dr. Beach, as he drove by piles of sargassum on Miami Beach.

Read also: Beach hustle: Thousands pack popular Vietnam shore
'Environmental disaster'
The stuff is nothing new. When Christopher Columbus saw a bloom of sargassum to the west of the Bahamas, it was so thick he thought it was an island.

That was out at sea, however.

"What happens out in the Atlantic Ocean, it's fine. But now this is an economic and environmental disaster," said Leatherman.

The pernicious effects are many: fishing boats have trouble starting their engines. Beaches are disgusting for tourists. Fish choke because the seaweed absorbs too much oxygen. Turtles struggle to find a place to lay eggs. When they do, the babies cannot make it from the shore out to sea. And dead seaweed sinks, smothering coral reefs.

No one has calculated how much damage is being done to countries' fishing and tourism industries.

In the British Virgin Islands, the layer of seaweed is seven feet (two meters) thick. Punta Cana, a beach in the Dominican Republic that is famous for its clear water, has turned brown. Barbados recently declared a national emergency. Mexico has called in the navy to restore the beauty of tourist hub Cancun.

"I don't know what's going on but it's really not a good sight to see, you know what I'm saying? We're tourists," said Sed Walker, 48, who was visiting from Los Angeles.

A study published in July by the University of South Florida in the journal Science concluded that the seaweed problem, which started in 2001 and showed peaks in 2015 and 2018, is here to stay.

Satellite imagery shows blooms of sargassum form at the mouth of the Amazon. From there it spreads across the Atlantic, from the Caribbean and the Gulf of Mexico to Africa.

Scientists named it the Great Atlantic Sargassum Belt (GASB). In 2015 and 2018, it stretched over nearly 5,592 miles. In June of last year, its biomass exceeded 20 million tons.

The study blamed the sargassum explosion on discharges of fertilizer in the Amazon and natural nutrients along the coast of Africa.

"A critical question is whether we have reached the point where recurrent GASB and beaching events may become the new norm," wrote Chuanmin Hu, the lead author of the study and a professor of optical oceanography at the university.

"Under continued nutrient enrichment due to deforestation and fertilizer use in agriculture," Hu wrote, "the answer is likely positive."

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Beaches choked with stinky seaweed could be the new normal

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Slimy, stinky brown seaweed that ruins beachgoers' vacations from Mexico to Florida may be the new normal unless Brazil halts Amazon deforestation, experts say. The culprit, called sargassum, turns clear-blue sea water a murky brown and smells like rotten eggs when it washes ashore and starts to rot.

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The 5 Lessons Everyone Should Learn From Einstein's Most Famous Equation: E = mc^2

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If you've ever heard of Albert Einstein, chances are you know at least one equation that he himself is famous for deriving: . This simple equation details a relationship between the energy ( E) of a system, its rest mass ( m), and a fundamental constant that relates the two, the speed of light squared (). Despite the fact that this equation is one of the simplest ones you can write down, what it means is dramatic and profound.

At a fundamental level, there is an equivalence between the mass of an object and the inherent energy stored within it. Mass is only one form of energy among many, such as electrical, thermal, or chemical energy, and therefore energy can be transformed from any of these forms into mass, and vice versa. The profound implications of Einstein's equations touch us in many ways in our day-to-day lives. Here are the five lessons everyone should learn.

1.) Mass is not conserved. When you think about the things that change versus the things that stay the same in this world, mass is one of those quantities we typically hold constant without thinking about it too much. If you take a block of iron and chop it up into a bunch of iron atoms, you fully expect that the whole equals the sum of its parts. That's an assumption that's clearly true, but only if mass is conserved.

In the real world, though, according to Einstein, mass is not conserved at all. If you were to take an iron atom, containing 26 protons, 30 neutrons, and 26 electrons, and were to place it on a scale, you'd find some disturbing facts.

An iron atom with all of its electrons weighs slightly less than an iron nucleus and its electrons do separately,

An iron nucleus weighs significantly less than 26 protons and 30 neutrons do separately.

And if you try and fuse an iron nucleus into a heavier one, it will require you to input more energy than you get out.

Each one of these facts is true because mass is just another form of energy. When you create something that's more energetically stable than the raw ingredients that it's made from, the process of creation must release enough energy to conserve the total amount of energy in the system.

When you bind an electron to an atom or molecule, or allow those electrons to transition to the lowest-energy state, those binding transitions must give off energy, and that energy must come from somewhere: the mass of the combined ingredients. This is even more severe for nuclear transitions than it is for atomic ones, with the former class typically being about 1000 times more energetic than the latter class.

In fact, leveraging the consequences of is how we get the second valuable lesson out of it.

2.) Energy is conserved, but only if you account for changing masses. Imagine the Earth as it orbits the Sun. Our planet orbits quickly: with an average speed of around 30 km/s, the speed required to keep it in a stable, elliptical orbit at an average distance of 150,000,000 km (93 million miles) from the Sun. If you put the Earth and Sun both on a scale, independently and individually, you would find that they weighed more than the Earth-Sun system as it is right now.

When you have any attractive force that binds two objects together - whether that's the electric force holding an electron in orbit around a nucleus, the nuclear force holding protons and neutrons together, or the gravitational force holding a planet to a star - the whole is less massive than the individual parts. And the more tightly you bind these objects together, the more energy the binding process emits, and the lower the rest mass of the end product.

When you bring a free electron in from a large distance away to bind to a nucleus, it's a lot like bringing in a free-falling comet from the outer reaches of the Solar System to bind to the Sun: unless it loses energy, it will come in, make a close approach, and slingshot back out again.

However, if there's some other way for the system to shed energy, things can become more tightly bound. Electrons do bind to nuclei, but only if they emit photons in the process. Comets can enter stable, periodic orbits, but only if another planet steals some of their kinetic energy. And protons and neutrons can bind together in large numbers, producing a much lighter nucleus and emitting high-energy photons (and other particles) in the process. That last scenario is at the heart of perhaps the most valuable and surprising lesson of all.

3.) Einstein's E = mc² is responsible for why the Sun (like any star) shines. Inside the core of our Sun, where the temperatures rise over a critical temperature of 4,000,000 K (up to nearly four times as large), the nuclear reactions powering our star take place. Protons are fused together under such extreme conditions that they can form a deuteron - a bound state of a proton and neutron - while emitting a positron and a neutrino to conserve energy.

Additional protons and deuterons can then bombard the newly formed particle, fusing these nuclei in a chain reaction until helium-4, with two protons and two neutrons, is created. This process occurs naturally in all main-sequence stars, and is where the Sun gets its energy from.

If you were to put this end product of helium-4 on a scale and compare it to the four protons that were used up to create it, you'd find that it was about 0.7% lighter: helium-4 has only 99.3% of the mass of four protons. Even though two of these protons have converted into neutrons, the binding energy is so strong that approximately 28 MeV of energy gets emitted in the process of forming each helium-4 nucleus.

In order to produce the energy we see it produce, the Sun needs to fuse 4 × 10 ³⁸ protons into helium-4 every second. The result of that fusion is that 596 million tons of helium-4 are produced with each second that passes, while 4 million tons of mass are converted into pure energy via . Over the lifetime of the entire Sun, it's lost approximately the mass of the planet Saturn due to the nuclear reactions in its core.

4.) Converting mass into energy is the most energy-efficient process in the Universe. What could be better than 100% efficiency? Absolutely nothing; 100% is the greatest energy gain you could ever hope for out of a reaction.

Well, if you look at the equation , it tells you that you can convert mass into pure energy, and tells you how much energy you'll get out. For every 1 kilogram of mass that you convert, you get a whopping 9 × 10 ¹⁶ joules of energy out: the equivalent of 21 Megatons of TNT. Whenever we experience a radioactive decay, a fission or fusion reaction, or an annihilation event between matter and antimatter, the mass of the reactants is larger than the mass of the products; the difference is how much energy is released.

In all cases, the energy that comes out - in all its combined forms - is exactly equal to the energy equivalent of the mass loss between products and reactants. The ultimate example is the case of matter-antimatter annihilation, where a particle and its antiparticle meet and produce two photons of the exact rest energy of the two particles.

Take an electron and a positron and let them annihilate, and you'll always get two photons of exactly 511 keV of energy out. It's no coincidence that the rest mass of electrons and positrons are each 511 keV/: the same value, just accounting for the conversion of mass into energy by a factor of . Einstein's most famous equation teaches us that any particle-antiparticle annihilation has the potential to be the ultimate energy source: a method to convert the entirety of the mass of your fuel into pure, useful energy.

5.) You can use energy to create matter - massive particles - out of nothing but pure energy. This is perhaps the most profound lesson of all. If you took two billiard balls and smashed one into the other, you'd always expect the results to have something in common: they'd always result in two and only two billiard balls.

With particles, though, the story is different. If you take two electrons and smash them together, you'll get two electrons out, but with enough energy, you might also get a new matter-antimatter pair of particles out, too. In other words, you will have created two new, massive particles where none existed previously: a matter particle (electron, muon, proton, etc.) and an antimatter particle (positron, antimuon, antiproton, etc.).

This is how particle accelerators successfully create the new particles they're searching for: by providing enough energy to create those particles (and, if necessary, their antiparticle counterparts) from a rearrangement of Einstein's most famous equation. Given enough free energy, you can create any particle(s) with mass m, so long as there's enough energy to satisfy the requirement that there's enough available energy to make that particle via . If you satisfy all the quantum rules and have enough energy to get there, you have no choice but to create new particles.

Einstein's is a triumph for the simple rules of fundamental physics. Mass isn't a fundamental quantity, but energy is, and mass is just one possible form of energy. Mass can be converted into energy and back again, and underlies everything from nuclear power to particle accelerators to atoms to the Solar System. So long as the laws of physics are what they are, it couldn't be any other way. As Einstein himself said:

It followed from the special theory of relativity that mass and energy are both but different manifestations of the same thing - a somewhat unfamiliar conception for the average mind.

More than 60 years after Einstein's death, it's long past time to bring his famous equation down to Earth. The laws of nature aren't just for physicists; they're for every curious person on Earth to experience, appreciate, and enjoy.

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The 5 Lessons Everyone Should Learn From Einstein's Most Famous Equation: E = mc^2

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If you've ever heard of Albert Einstein, chances are you know at least one equation that he himself is famous for deriving: . This simple equation details a relationship between the energy ( E) of a system, its rest mass ( m), and a fundamental constant that relates the two, the speed of light squared ().

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Opinion | The Problem With Greta Thunberg’s Climate Activism - The New York Times

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Her radical approach is at odds with democracy.

Mr. Caldwell is the author of "Reflections on the Revolution in Europe: Immigration, Islam, and the West."

The 16-year-old Swedish climate activist Greta Thunberg, second from right, at a session of the French National Assembly in July. Credit... Stephane De Sakutin/Agence France-Presse - Getty Images

Climate activists in Western Europe had already been radicalizing for some time when record heat engulfed the Continent last month. The high reached 109 degrees in Paris two Thursdays ago. Yet many environmentalists have come to believe that extreme weather alone will never spur Europeans to give up fossil fuels. Nor will talking about it. Provocations and disruption are needed.

The problem is not that Europeans think like Americans, 13 percent of whom say human activity is "not responsible at all" for global warming. Europeans are less cynical about official accounts of climate change that come from the United Nations and various universities. The problem, rather, is that Europeans act like Americans, holding tight to their driving and consuming habits.

Climate activists have therefore changed their emphasis. No more eliciting pieties by explaining what happens when carbon dioxide rises past 400 parts per million. Better to use the specter of imminent self-extinction to rally the public behind actions like banning cars from city centers and halting new oil exploration.

This new focus may have the virtue of conveying urgency. But it is going to bring the climate protesters into conflict with democracy, whether they realize it or not.

The symbol of this transformation is the Swedish high school student Greta Thunberg, who describes herself to her 800,000-plus Twitter followers as a "16-year-old climate activist with Asperger." Late last summer she began skipping school on Fridays and traveling to Sweden's Parliament, the Riksdag, where she handed out fliers informing adults, in crude language, that she was doing this because they were ruining her future.

Classmates joined her. Students in other European capitals imitated her. "Fridays for Future," as the protests came to be called, turned Ms. Thunberg into the first world political leader born this century. They have been hailed by Green parties across the Continent, many of which won impressive victories in May's European elections.

Ms. Thunberg believes people should act, not argue. That, perhaps, is why she is planning to travel to next month's United Nations global warming summit in New York by sailboat, not airplane. It is not that Ms. Thunberg does not care about climate data; indeed, she cites the annual reports of the United Nations Intergovernmental Panel on Climate Change as if they were gospel. It is just that she is done debating.

Her politics rests on two things. First is simplification. "The climate crisis already has been solved," she said at a TED Talk in Stockholm this year. "We already have all the facts and solutions. All we have to do is wake up and change." Second is sowing panic, as she explained at the World Economic Forum in Davos last winter.

Normally Ms. Thunberg would be unqualified to debate in a democratic forum. Since a 16-year-old is not a legally responsible adult, she cannot be robustly criticized and, even leaving aside her self-description as autistic, Ms. Thunberg is a complicated adolescent. Intellectually, she is precocious and subtle. She reasons like a well-read but dogmatic student radical in her 20s. Physically, she is diminutive and fresh-faced, comes off as younger than her years, and frequently refers to herself as a "child" - about the last thing the average 16-year-old would ever do.

Kids her age have not seen much of life. Her worldview might be unrealistic, her priorities out of balance. But in our time, and in her cause, that seems to be a plus. People have had enough of balance and perspective. They want single-minded devotion to the task at hand.

This Ms. Thunberg provides. That climate change be understood as an "emergency" is her first objective. Increasingly, authorities share it. The week of the heat wave, according to The Economist,the Met Office, the British meteorological agency, was trying to speed up its "attribution studies" so that it can link incidents of extreme weather to global warming before the public's attention drifts. This is a political, not a meteorological, goal. There are also calls to politicize language: In May, The Guardian announced it would use the term "climate crisis" rather than "climate change" in its articles, and "global heating" rather than "global warming."

Alliances between institutional authorities and activists like Ms. Thunberg often backfire. With questions of global warming, the problems of credibility are already large, even without fresh incitements to politicization. Sometime after the age of 16, most people learn that not even the members of the Intergovernmental Panel on Climate Change are above self-interest and human error.

It is also hard to say what a real, non-utopian low-carbon politics would look like, once the public got involved in legislating and regulating. Contrary to the assumptions of many of Ms. Thunberg's admirers, it might resemble contemporary populist agendas more than the world imagined by the United Nations' modelers and the governance experts of Davos. Protectionism could be in: If you establish a system of carbon pricing, countries that don't practice it are "dumping," and their imports must be excluded. Immigration could be out: It is difficult to see how any kind of long-term mass immigration is consistent with a desire to lower Europe's carbon output.

And that is before we even broach the question of what kind of civilization we want, and at what level of technological complexity. On a planet of eight billion people, it is not just destination weddings that require considerable expenditure of energy. So does food. So does clean drinking water. So does communication.

Increasingly, climate agitators want action, not distraction. That often requires demonizing anyone who stands in the way. In July the climate editor of the Dutch newspaper NRC Handelsblad complained that Paris's declaration of a "climate state of emergency" on July 9 had not been accompanied by a ban on automobile traffic in Paris or by a dimming of the lights on the Eiffel Tower. In Germany the word "Flugscham " is one of the last year's more interesting coinages. It means not fear of flying but shame of flying, and of the pollution it brings about. The German economist Niko Paech urges shaming people for booking cruises and driving S.U.V.s, too.

Behind the new boldness of climate activists is the assumption that ordinary Europeans' good intentions are sincere and their inaction is hypocritical. It could be the other way around. Whatever the case, Europeans' slowness to act on the climate cannot simply be dismissed as "denial." Those who read the United Nations reports and tut-tut but fail to take to the streets might be less resolute - but they might simply disagree, or have other priorities.

Democracy often calls for waiting and seeing. Patience may be democracy's cardinal virtue. Climate change is a serious issue. But to say, "We can't wait," is to invite a problem just as grave.

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Opinion | The Problem With Greta Thunberg's Climate Activism (Published 2019)

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Her radical approach is at odds with democracy. Mr. Caldwell is the author of "Reflections on the Revolution in Europe: Immigration, Islam, and the West." Climate activists in Western Europe had already been radicalizing for some time when record heat engulfed the Continent last month. The high reached 109 degrees in Paris two Thursdays ago.

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Depuis la nuit des temps, le soleil brille sur la Terre. Pourtant, la nature de cette grosse boule jaune est restée mystérieuse pendant des millénaires. Notre étoile, le Soleil, était bien trop loin de la Terre pour comprendre ce qu'elle renfermait.

Ce n'est qu'au début du XX e siècle, avec les travaux de l'astronome Cecilia Payne, que le mystère s'est éclairci. En s'appuyant sur la spectroscopie et la physique atomique, la jeune astronome a trouvé les premières clés pour comprendre ce qu'il y a dans les étoiles. Et cette découverte s'est avérée révolutionnaire.

Notre série documentaire " Chercheuses d'étoiles " vous raconte chaque semaine de grandes découvertes astronomiques faites par des femmes. Des femmes souvent méconnues du grand public qui ont pourtant permis de grandes avancées pour mieux comprendre les mystères de l'Univers. Les épisodes de la série sortiront chaque samedi du mois d'août, à 14 heures. Vous pouvez les retrouver dans notre rubrique " Séries " ou dans la playlist dédiée sur notre chaîne Youtube.

LES AUTRES EPISODES :

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Vidéo. De quoi sont faites les étoiles ?

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Depuis la nuit des temps, le soleil brille sur la Terre. Pourtant, la nature de cette grosse boule jaune est restée mystérieuse pendant des millénaires. Notre étoile, le Soleil, était bien trop loin de la Terre pour comprendre ce qu'elle renfermait.

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Climate change: Current warming 'unparalleled' in 2,000 years - BBC News

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The speed and extent of current global warming exceeds any similar event in the past 2,000 years, researchers say.

They show that famous historic events like the "Little Ice Age" don't compare with the scale of warming seen over the last century.

The research suggests that the current warming rate is higher than any observed previously.

The scientists say it shows many of the arguments used by climate sceptics are no longer valid.

Twelve years to save Earth? Make that 18 months...

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When scientists have surveyed the climatic history of our world over the past centuries a number of key eras have stood out.

These ranged from the "Roman Warm Period", which ran from AD 250 to AD 400, and saw unusually warm weather across Europe, to the famed Little Ice Age, which saw temperatures drop for centuries from the 1300s.

The events were seen by some as evidence that the world has warmed and cooled many times over the centuries and that the warming seen in the world since the industrial revolution was part of that pattern and therefore nothing to be alarmed about.

Three new research papers show that argument is on shaky ground.

The science teams reconstructed the climate conditions that existed over the past 2,000 years using 700 proxy records of temperature changes, including tree rings, corals and lake sediments. They determined that none of these climate events occurred on a global scale.

The researchers say that, for example, the Little Ice Age was at its strongest in the Pacific Ocean in the 15th Century, while in Europe it was the 17th Century.

Generally, any longer-term peaks or troughs in temperature could be detected in no more than half the globe at any one time,

The "Medieval Warm Period", which ran between AD 950 and AD 1250 only saw significant temperature rises across 40% of the Earth's surface.

Today's warming, by contrast, impacts the vast majority of the world.

"We find that the warmest period of the past two millennia occurred during the 20th Century for more than 98% of the globe," one of the papers states.

"This provides strong evidence that anthropogenic (human induced) global warming is not only unparalleled in terms of absolute temperatures but also unprecedented in spatial consistency within the context of the past 2,000 years."

What the researchers saw is that prior to the modern industrial era, the most significant influence on climate was volcanoes. They found no indication that variations in the Sun's radiation impacted mean global temperatures.

The current period, say the authors, significantly exceeds natural variability.

"We see from the instrumental data and also from our reconstruction that in the recent past the warming rate clearly exceeds the natural warming rates that we calculated - that's another view to look at the extraordinary nature of the present warming," said Dr Raphael Neukom, from the University of Bern, Switzerland.

While the researchers did not set out to test whether humans were the chief influence on the current climate, their findings indicate clearly that this is the case.

"We do not focus on looking at what's causing the most recent warming as this has been done many times and the evidence is always agreeing that it is the anthropogenic cause," said Dr Neukom.

"We do not explicitly test this; we can only show that natural causes are not sufficient from our data to actually cause the spatial pattern and the warming rate that we are observing now."

Other scientists have been impressed with the quality of the new studies.

"They have done this across the globe with more than 700 records over the past 2,000 years; they have corals and lakes and also instrumental data," said Prof Daniela Schmidt from the University of Bristol, UK, who was not involved with the studies.

"And they have been very careful in assessing the data and the inherent bias that any data has, so the quality of this data and the coverage of this data is the real major advance here; it is amazing."

Many experts say that this new work debunks many of the claims made by climate sceptics in recent decades.

"This paper should finally stop climate change deniers claiming that the recent observed coherent global warming is part of a natural climate cycle," said Prof Mark Maslin, from University College London, UK, who wasn't part of the studies.

"This paper shows the truly stark difference between regional and localised changes in climate of the past and the truly global effect of anthropogenic greenhouse emissions."

The three papers have been published in the journals Nature (1) and Nature Geoscience (2), (3).

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Global warming 'unparalleled' in 2,000 years

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The speed and extent of current global warming exceeds any similar event in the past 2,000 years, researchers say. They show that famous historic events like the "Little Ice Age" don't compare with the scale of warming seen over the last century. The research suggests that the current warming rate is higher than any observed previously.

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Hong Kong air pollution is ‘serious’ health risk for second day in a row, as low pressure influenced by Tropical Cyclone Danas leads to hazy conditions https://www.scmp.com/news/hong-kong/health-environment/article/3019176/hong-kong-air-pollution-serious-health-risk

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Tache complexe : quelle serait l’équivalent de ce poster pour la gravité ?

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Negative? How a Navy veteran refused to accept a ‘no’ to his battery invention https://techcrunch.com/2019/07/12/naval-veteran-aluminum-air-metalectrique/

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Madrid low emission zone reinstated after protests - BBC News

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Fines for vehicles entering areas of central Madrid have been reinstated, five days after a low emission zone policy was suspended.

The new conservative mayor, José Luis Martínez-Almeida, had shelved the initiative known as Madrid Central.

It was introduced by his left-wing predecessor, Manuela Carmena, in November to meet EU rules on clean air.

A court reinstated the ban after a spike in pollution and mass environmental protests.

The People's Party-run city hall, which came into power on 15 June, had suspended the ban on most petrol and diesel cars entering the centre.

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Air pollution early deaths rise in EU

It had been introduced to ramp up anti-pollution efforts and mirrored schemes in other European cities like London, Stockholm and Milan, whose governments wanted to tackle the harmful effects of vehicle emissions.

Since Madrid Central came into force seven months ago, the lowest air pollution was recorded in 10 years.

But in the five days since the ban was lifted, there had been a "surge" in pollution, environmental groups say.

On Monday, thousands of protesters hit the streets to protest against Mr Martínez-Almeida's decision to shelve the policy.

The Spanish Socialist Workers' Party, along with a group of various environmental organisations, presented an appeal against the lifting of the ban.

The judge said "the health of Madrid" was more important than "the right to travel by car" and reversed the decision.

It will mean that most vehicles once again cannot enter the low emissions zone in central Madrid.

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Madrid low emission zone reinstated after protests

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Fines for vehicles entering areas of central Madrid have been reinstated, five days after a low emission zone policy was suspended. The new conservative mayor, José Luis Martínez-Almeida, had shelved the initiative known as Madrid Central. It was introduced by his left-wing predecessor, Manuela Carmena, in November to meet EU rules on clean air.

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NASA fights to keep the Voyager probes running after four decades https://www.engadget.com/2019/07/13/nasa-voyager-2-heater/

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Physique - chimie : Des ressources pour les nouveaux programmes du lycée

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Physique - chimie : Des ressources pour les nouveaux programmes du lycée

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Revue de l'IUPAC - Physique-Chimie - Éduscol

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Heat waves bring record-breaking temperatures on a geological scale | TechCrunch

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From Alaska to Europe, the world has spent the past few weeks roasting under temperatures never before seen in recorded history.

In Alaska, all-time-high record temperatures were set across the state on July 4th, according to the National Weather Service. In Anchorage, the mercury soared to highs of 90 degrees, the highest temperature since recording began in 1952.

Temperatures in Alaska have reached 90 degrees in other cities around the state before, but this is the first time the thermometer hit that mark in Anchorage.

Meanwhile, hot winds blowing North from the Sahara set temperatures in Europe soaring to record highs, according to data released by the Copernicus Climate Change Service.

It was Europe's record three-degree temperature spike that brought global temperatures to their recorded-history highs.

"Although local temperatures may have been lower or higher than those forecast, our data show that the temperatures over the southwestern region of Europe during the last week of June were unusually high," said Jean-Noël Thépaut, head of the Copernicus Climate Change Service. "Although this was exceptional, we are likely to see more of these events in the future due to climate change."

According to data from Copernicus, the temperature spike across Europe was the highest on record for the month.

Compared for the same five-day period during the last 30-year climatological reference period, six to 10 degree Celsius temperature spikes happened in most of France and Germany, throughout northern Spain, northern Italy, Switzerland, Austria and the Czech Republic.

As these events become common, the need for technologies that can reduce carbon emissions because more pressing.

Increasingly, businesses and investors are returning to the once-shunned market of clean technology and renewable energy to back new electric vehicle manufacturers, new energy efficient construction technologies, the rehabilitation of outdated infrastructure and consumer goods that have a smaller carbon footprint or reduce waste.

Data from Bloomberg New Energy Finance published earlier this year indicated that venture investments into what was once called clean technology hit $9.2 billion in 2018. That's the highest cumulative investment in the sector since 2009. Much of those deals were in Chinese electric vehicle manufacturers that attracted some $3.3 billion in venture capital and private equity dollars.

That's critical, because global carbon emissions have increased over the past two years, according to estimates from the Global Carbon Project.

"We thought, perhaps hoped, emissions had peaked a few years ago," said Rob Jackson, a professor of Earth system science in Stanford's School of Earth, Energy & Environmental Sciences (Stanford Earth). "After two years of renewed growth, that was wishful thinking."

In the U.S. specifically, climate-related pressures (a warmer summer and a colder winter) led to increasing demand along with an uptick in gasoline consumption as demand for bigger vehicles fueled higher gas consumption.

"We're driving more miles in bigger cars, changes that are outpacing improvements in vehicle fuel efficiency," Jackson explained.

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Heat waves bring record-breaking temperatures on a geological scale

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From Alaska to Europe, the world has spent the past few weeks roasting under temperatures never before seen in recorded history. In Alaska, all-time-high record temperatures were set across the state on July 4th, according to the National Weather Service. In Anchorage, the mercury soared to highs o...

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How trees could save the climate | EurekAlert! Science News

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Around 0.9 billion hectares of land worldwide would be suitable for reforestation, which could ultimately capture two thirds of human-made carbon emissions. The Crowther Lab of ETH Zurich has published a study in the journal Science that shows this would be the most effective method to combat climate change.

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Greenland’s ‘unusual’ melting sea ice captured in stunning image - BBC News

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With their sled in tow, a pack of dogs trudge towards a distant mountain range in north-west Greenland.

The stunning picture may seem typical enough of the Danish territory. What's beneath their feet - a shallow pool of crystal-blue water - is anything but.

Last week, however, temperatures soared well above normal levels in Greenland, causing about half of its ice sheet surface to experience melting.

And the sea ice around the territory is, of course, also feeling this heat.

Steffen Olsen, a climate scientist at the Danish Meteorological Institute (DMI), took the photo on 13 June as these warming conditions reached their peak.

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Rain melting Greenland ice sheet 'even in winter'

Mr Olsen and his team were retrieving equipment from a weather station in the Inglefield Fjord area. As they walked across the 1.2m (4ft) thick sea ice, water pooled on the surface.

On Twitter, his colleague at DMI Rasmus Tonboe later shared the image, telling followers "rapid melt" had occurred.

Because the sea ice is compact with almost no cracks, the image gives the impression the dogs are walking on water, Martin Stendel, senior researcher at the institute, told the BBC.

On that day, Greenland is estimated to have lost the equivalent of 2bn tonnes of ice. Temperatures, according to the European Centre for Medium-range Weather Forecasting, were around 22C above normal the day before. In the village of Qaanaaq, a high of 17.3C was recorded.

Since then, Mr Olsen's photo has been shared widely on social media, provoking concern at the extent of the melting event and its causes.

Greenland's ice sheet melts annually, with the season usually lasting from June to August. The summer months - typically in July - are when it reaches its height. This year, however, climate experts say it is early.

"It's very unusual to have this much melt so early in the season," William Colgan, senior researcher at the Geological Survey of Denmark and Greenland, told the BBC.

"It takes very rare conditions but they're becoming increasingly common."

Mr Colgan compared the melt to 2012, when record-breaking ice sheet loss was recorded in Greenland. He said the same two factors were thought to have caused last week's ice melt and the historic event of 2012.

One is high pressure lodged over Greenland, creating warm and sunny conditions. The other is low cloud cover and snowfall, meaning solar radiation can strike the ice sheet surface.

Global warming, Mr Colgan said, was "tremendously important" to these sorts of events.

"What climate change is doing is increasingly loading the dice to set up weather conditions that can tip the ice sheets into these mass loss events," he said.

If these trends continued, said Professor Edward Hanna, a climate scientist at the University of Lincoln, Greenland could experience a record melt this year.

"The thing is, with climate trends, as we've seen over the past 20 years, as it gets warmer and warmer over Greenland, you don't need that much of an exceptional event to melt the whole surface of the ice," he told the BBC.

The consequences, he said, would not only be felt locally but globally, too.

As sea ice disappears, local communities who rely on it for transport, hunting and fishing are expected to suffer. On a global level, Prof Hanna said "sea level rise is the big one".

"You're losing something like 250 billion tonnes of ice a year on average. A huge mass is being transferred from the land into the oceans," he said.

Mr Colgan said we should be mindful that the melt on 13 June was just "a one-day event that is surprising in its magnitude and its early onset".

As studies showed, he said, global warming could mean more extreme melting events were yet to come.

"We can expect to see more of these in the future," he said.

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The stark photo highlighting Greenland's ice loss

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With their sled in tow, a pack of dogs trudge towards a distant mountain range in north-west Greenland. The stunning picture may seem typical enough of the Danish territory. What's beneath their feet - a shallow pool of crystal-blue water - is anything but.

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Saturday Morning Breakfast Cereal - Teaching

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Saturday Morning Breakfast Cereal - Teaching

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Bird feeding chick cigarette end captured in picture - BBC News

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A wildlife photographer has captured a picture of a black skimmer bird feeding its chick a cigarette filter on a beach in Florida, USA.

In a Facebook post, Karen Mason said she had happened upon the pair on St Pete beach outside Tampa last month.

She urged: "If you smoke, please don't leave your butts behind."

The UK's RSPB, which described the picture as "heartbreaking", says nature is struggling to adapt to human littering.

Ms Mason also captured another picture of the chick carrying the filter in its beak:

Birds can mistake the filters for food and feed them to their young.

"Many birds are curious about the things we casually discard, and will often investigate to try and find out if something is food or not," a spokesman for the Royal Society for the Protection of Birds (RSPB) told the BBC.

"Sadly, this parent has decided the cigarette butt is something to feed its chick.

"Nature is struggling to adapt to the things we are doing to our planet; every year, we see more animals trapped, injured or killed by man-made products. We are even seeing litter being used as nesting material.

"Unfortunately for many people, littering seems harmless, at worst it makes an area look untidy; however, heartbreaking images like reveal the true impact of littering on our wildlife."

WATCH: Puffins at risk from warming sea water

Christmas decorations kill NZ birds

RSPB birdsong track highlights loss of 40 million birds

Cigarette filters are usually made of plastic fibres (cellulose acetate), and take years to break down in the environment.

They are the most common item of rubbish collected from beaches globally, according to conservationists.

More stories like this:

How frogs could vanish from ponds

Humans 'threaten 1m species with extinction'

Extreme weather risks for bats.

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Picture captures bird feeding chick cigarette end

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A wildlife photographer has captured a picture of a black skimmer bird feeding its chick a cigarette filter on a beach in Florida, USA. In a Facebook post, Karen Mason said she had happened upon the pair on St Pete beach outside Tampa last month.

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Introduction

Les académies qui ont participé aux TraAM 2018-2019 ont axé leurs productions sur la thématique du codage et de l'algorithmique pour l'enseignement de la physique-chimie.

Les six académies ayant contribué cette année à ce projet national ont élaboré différents types de scénarios pédagogiques, testés en classe, pour lesquels les objectifs de la pratique innovante, le contexte pédagogique, les outils ou fonctionnalités nécessaires ainsi que des exemples d'usages ont été définis. Les scénarios font également le bilan des apports et des freins rencontrés lors de la mise en œuvre en classe.

Les pages TraAM des académies

Synthèse des travaux

Collège
Des signaux pour observer et communiquer L'énergie et ses conservations Mouvement et interactions Organisation et transformations de la matière Transition écologique et développement durable
Lycée
Constitution et transformation de la matière Énergie Mouvement et interactions Ondes et signaux Radioactivité Sources de lumières colorées Signaux et capteurs Vision et image
Lycée pro
Livrer une installation
Supérieur
Traitement numérique du signal Mouvement et interactions Capsules vidéo
Conclusion

Dans le cadre des enseignements de physique-chimie, les élèves utilisent fréquemment des logiciels de simulation, d'acquisition ou de traitement de données basés sur des algorithmes et des programmes qui leur sont inconnus la plupart du temps.

En mettant au point des algorithmes en relation avec des problématiques de physique-chimie et en les programmant eux-mêmes, même modestement, les élèves peuvent dépasser cette logique de " boite noire ", démystifier ces outils et mieux appréhender les notions scientifiques qui sont mobilisées.

Les exemples d'usages proposés par les différents groupes académiques engagés dans les TraAM 2018-2019 permettent de s'éloigner de cette logique de " boite noire " inconnue. Les séquences pédagogiques réalisées intègrent des outils divers et variés : tableur-grapheur ; programmes en Python Arduino ou Scratch ; microcontrôleurs... L'introduction de ces différents outils s'est toujours fait au service de la physique et de la chimie.

Constitution du groupe de travail national

Les Travaux académiques mutualisés de physique-chimie 2018-2019 ont été menés à bien par le groupe de travail suivant :

Jean Cavailles (IGEN) ;
Le groupe d'experts de la DNE :

département du développement des usages et de la valorisation des pratiques (DNE-A2) : Sophie Edouard, David Latouche ;

département du développement et de la diffusion des ressources numériques (DNE-A1) : Christine Trabado.

Les académies impliquées et les professeurs référents :

Amiens : Perrine Gaffet ; Anne-Sophie Agbo-Sonan (IA-IPR) et Thouraya Abdellatif (IA-IPR) ;

Aix-Marseille : Sophie Maier ; Isabelle Tarride (IA-IPR) ;

Créteil : Thomas Lavarenne ; Claude Murcuillat (IA-IPR) ;

Lyon : Sarah Roques ; Marie-Alice Trossat (IA-IPR) ;

Strasbourg : Fabrice Maquère ; Philippe Martin (IA-IPR) ;

Versailles : Alban Goulley ; Annie Zentilin (IA-IPR) et Romain Salvan (IA-IPR).

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Le codage et l\'algorithmique pour l\'enseignement de la physique-chimie (2018-2019) - Physique-Chimie - Éduscol

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Les académies qui ont participé aux TraAM 2018-2019 ont axé leurs productions sur la thématique du codage et de l'algorithmique pour l'enseignement de la physique-chimie. Les six académies ayant contribué cette année à ce projet national ont élaboré différents types de scénarios pédagogiques, testés en classe, pour lesquels les objectifs de la pratique innovante, le contexte pédagogique, les outils ou fonctionnalités nécessaires ainsi que des exemples d'usages ont été définis.

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Pavegen plans to power the world with footsteps

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Canicule : pourquoi observe-t-on des pics de pollution à l'ozone ? - Sciences - Numerama

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Les vagues de chaleur et autres épisodes de canicule peuvent s'accompagner de pics d'ozone. En quoi consiste cette pollution ? Comment se forme-t-elle et quels risques pose-t-elle pour la santé ?

La pollution à l'ozone devrait dépasser le seuil de 180 microgrammes par mètre cube (mg/m³) en Île-de-France ce 26 juin 2019. La situation est favorisée par la vague de chaleur qui touche en ce moment l'hexagone, a annoncé Airparif, l'association qui surveille la qualité de l'air dans la région.

L'association estime que la pollution à l'ozone devrait se situer dans une fourchette entre 170 et 200 mg/m³ au cours de la journée. Le lendemain, le 27 juin, la quantité d'ozone pourrait se situer entre 180 et 210 mg/m³. " Les périodes caniculaires et l'ensoleillement sont propices à cette fabrication intensive à l'ozone ", nous explique Charlotte Songeur, ingénieure au sein d'Airparif.

[Qualité de l'air] [Vigilance] le niveau est moyen aujourd'hui la formation d'Ozone se poursuit et les niveaux montent, le premier seuil dit "d'information" sera passé aujourd'hui comme annoncé par @Airparif .
VIGILANCE le niveau passe à élevé demain suivez les recommandations pic.twitter.com/Rj4qpcGzj0

- Airparif (@Airparif) June 26, 2019

Qu'est-ce que la pollution à l'ozone ?

Il faut distinguer l'ozone qui se trouve à haute altitude dans l'atmosphère et joue un rôle protecteur en filtrant les rayons ultraviolets du Soleil, et l'ozone présent dans la basse atmosphère (celle où nous respirons). Naturellement, il s'y trouve en petite quantité. Si cette quantité augmente, l'ozone peut alors devenir un polluant.

" C'est un polluant secondaire, poursuit l'ingénieure. Il est fabriqué chimiquement dans l'atmosphère. Il est à distinguer des polluants primaires, qui sont émis directement dans l'atmosphère. Certaines particules sont à la fois des polluants primaires et secondaires. " Les polluants primaires peuvent provenir de sources de pollution comme le trafic routier, l'industrie, le chauffage ou l'agriculture.

La formation d'ozone est favorisée par deux éléments : les oxydes d'azote, principalement émis par le trafic routier, ainsi que les composés organiques volatils (COV), des hydrocarbures que l'on trouve principalement dans l'essence, des colles, des peintures, des solvants, mais qui peuvent aussi venir des deux roues motorisés, ou encore de la forêt ou de la végétation. La présence de rayonnements ultraviolets, des températures élevées (au-dessus de 30°C) et l'absence de vent " rend cette réaction plus intense qu'en temps normal ", explique Charlotte Songeur. L'ozone est un " polluant photochimique ", un polluant que l'on retrouve en été.

Sa particularité : c'est un polluant qui voyage

Cette pollution à l'ozone ne concerne pas que les grandes villes. " L'ozone en formation voyage avec le vent jusque dans les zones rurales. C'est une de ses particularités, d'autres polluants ont une durée de vie plus limitée. Les niveaux peuvent être moins importants près du trafic routier... même si je vous déconseille évidemment de rester à cet endroit ", rappelle notre interlocutrice.

L'ozone est un gaz à effet de serre, qui peut avoir des impacts sur la santé comme des irritations (yeux, gorge, nez). Pratiquer une activité physique risque de faire inhaler davantage d'air et donc davantage de polluants. " Il vaut mieux éviter les activités en extérieur aux moments où les niveaux d'ozone sont les plus importants. Le niveau monte dans la journée, pour être maximal en fin d'après-midi. Le matin, le niveau est au plus bas : c'est le meilleur moment pour aérer son logement et pratiquer des activités en extérieur ", conseille l'ingénieure.

Airparif a constaté que depuis 15 ans, les moyennes annuelles d'ozone ont été presque multipliées par deux à Paris. " L'ozone est le seul polluant surveillé en Île-de-France pour lequel les concentrations moyennes relevées tout au long de l'année sont en augmentation ", écrit l'association.

Tant que vous êtes là : nous avons une question pour vous.

Nous pensons à l'avenir de Numerama et votre avis compte beaucoup pour nous : pouvez-vous remplir le formulaire ci-dessous ? Cela ne prendra qu'une minute !

Crédit photo de la une : Flickr/CC/Jeanne Menjoulet (photo recardée)

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Canicule : pourquoi observe-t-on des pics de pollution à l'ozone ? - Sciences - Numerama

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Les vagues de chaleur et autres épisodes de canicule peuvent s'accompagner de pics d'ozone. En quoi consiste cette pollution ? Comment se forme-t-elle et quels risques pose-t-elle pour la santé ? La pollution à l'ozone devrait dépasser le seuil de 180 microgrammes par mètre cube (mg/m³) en Île-de-France ce 26 juin 2019.

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Un concours de la NASA accouche de modèles de colonisation galactique | Journal du Geek

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Lors de ce concours organisé par le mythique Jet Propulsion Laboratory de la NASA, les participants -tous des physiciens, mathématiciens, ingénieurs en aéronautique et en informatique chevronnés- doivent trouver des solutions efficaces à des problèmes extrêmement complexes. Après la gestion des débris spatiaux lors de l' édition précédente, il fallait cette fois se creuses les méninges pour accoucher d'un modèle efficace de colonisation de notre galaxie, rien que ça. D'après les organisateurs du GTOC, il s'agit d'une " façon de favoriser l'innovation dans l'optimisation des trajectoires interplanétaires et l'entre-alimentation des idées entre chercheurs dans les domaines de l'astrodynamique et de l'optimisation."

L'épreuve a été remportée par une équipe chinoise, composée de membres de la China's National University of Defence Technology, et du Xi'an Satellite Control Center. Leur modèle est disponible ici.

La seconde place a également été ravie par des chinois, de l'université de Tsinghua cette fois. Cependant, leur modélisation n'a pas encore été publiée. C'est l'Advanced Concepts Team de l'Agence Spatiale Européenne (ESA) qui complète le podium : voici la modélisation issue de leur travail.

Sur ces simulations, chaque point représente une étoile considérée comme potentiellement habitable, tandis que les lignes représentent les trajectoires empruntées par les colons.

En pratique, chaque équipe s'est vue remettre un ensemble de données représentant environ 100.000 systèmes d'étoiles et un ensemble d'équations détaillant avec précision les paramètres orbitaux des corps célestes en question. A partir de ce point, les équipes étaient livrées à elles-mêmes et devaient mettre au point leur propre méthodologie pour coloniser la galaxie le plus efficacement possible en 90 millions d'années, avec un certain nombre de contraintes :

Chaque équipe démarre sa simulation avec deux vaisseaux mère (en bleu), et deux vaisseaux dits "rapides" (en vert).

Chaque vaisseau mère contient dix "capsules de colonie" pouvant coloniser un système d'étoiles chacun

Trois vaisseaux colons peuvent partir de chaque système deux millions d'années après l'avoir colonisé

Chaque système ne peut être colonisé qu'une seule fois

Pour simplifier, on considère que les étoiles ont une masse nulle. On en déduit qu' il n'y a donc pas d'assistance gravitationnelle (ou "effet fronde") possible

les manœuvres orbitales des vaisseaux sont restreintes en termes de temps, de vitesse et d'accélération, sans quoi la solution serait considérée invalide

Pour désigner le vainqueur, les organisateurs ont mis au point une formule complexe, du genre à faire convulser les allergiques aux mathématiques et censée rendre compte de l'efficacité de la colonisation selon les principaux critères de l'épreuve. Si vous souhaitez y jeter un oeil, elle est disponible en page 4 des instructions. Pour maximiser son score, il fallait ainsi coloniser un maximum de systèmes en 90 millions d'années, avec la distribution spatiale la plus homogène possible, et en utilisant le moins de puissanc e de propulsion possible.

Un scénario très artificiel, mais une simulation néanmoins pertinente

Ces contraintes font de ce problème un véritable casse-tête logistique. Le choix de la destination des premiers vaisseaux, par exemple, est absolument crucial. Mais si l'exercice est fascinant intellectuellement, il n'a pas vocation à être une simulation entièrement réaliste. En témoignent les approximations mentionnées dans l' énoncé du problème.

Mais ce n'est pas parce qu'il ne s'agit pas d'un plan de conquête galactique servi sur un plateau que l'expérience est dénuée d'intérêt. A l'heure où la question des premiers voyages à l'échelle galactique commencera à se poser, il faudra résoudre des problèmes de ce type, mais d'un niveau de complexité encore bien supérieur, sans approximation de confort possible. Des initiatives comme le GTOC permettent donc de travailler sur une méthodologie et de mettre les modèles actuels à l'épreuve, en attendant de disposer de la technologie et de la connaissance nécessaire à la mise en pratique.

La Voie Lactée est âgée d'environ 13.500 millions d'années. Cette conquête virtuelle de 90 Ma ne représente donc même pas un petit pourcent de la vie de notre galaxie ! Un point intéressant à noter est que ce chiffre est concordant avec certaines études sérieuses sur la question.

De quoi jeter encore plus d'huile sur le brasier du paradoxe de Fermi, à travers lequel on tente de comprendre si nous sommes seuls dans l'univers, et si non, pourquoi aucune espèce extraterrestre n'a encore colonisé la galaxie de cette façon. Si vous n'êtes pas familier de cette fascinante expérience de pensée qu'est la paradoxe de Fermi, cet article de l'institut SETI le résume de façon très concise et élégante.

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Un concours de la NASA accouche de modèles de colonisation galactique | Journal du Geek

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Lors de ce concours organisé par le mythique Jet Propulsion Laboratory de la NASA, les participants -tous des physiciens, mathématiciens, ingénieurs en aéronautique et en informatique chevronnés- doivent trouver des solutions efficaces à des problèmes extrêmement complexes.

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Des soudures défectueuses retardent la mise en service du tout dernier cercle des Enfers de nouvelle génération — Le Gorafi.fr Gorafi News Network

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Des soudures défectueuses retardent la mise en service du tout dernier cercle des Enfers de nouvelle génération

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Enfer - C'est un retard qui tombe mal. Le tout dernier cercle des enfers de nouvelle génération qui devait accueillir ses âmes damnés dès 2024 voit sa mise en service repoussée. En cause, des soudures défectueuses détectées par l'Autorité de la Sûreté des Damnations. Reportage.

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What Is The Smallest Possible Distance In The Universe?

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If you wanted to understand how our Universe operates, you'd have to examine it at a fundamental level. Macroscopic objects are made up of particles, which can only themselves be detected by going to subatomic scales. To examine the Universe's properties, you must to look at the smallest constituents on the smallest possible scales. Only by understanding how they behave at this fundamental level can we hope to understand how they join together to create the human-scale Universe we're familiar with.

But you can't extrapolate what we know about even the small-scale Universe to arbitrarily small distance scales. If we decide to go down to below about 10⁻³⁵ meters ⁠- the Planck distance scale ⁠- our conventional laws of physics only give nonsense for answers. Here's the story of why, below a certain length scale, we cannot say anything physically meaningful.

Imagine, if you like, one of the classic problems of quantum physics: the particle-in-a-box. Imagine any particle you like, and imagine that it's somehow confined to a certain small volume of space. Now, in this quantum game of peek-a-boo, we're going to ask the most straightforward question you can imagine: "where is this particle?"

You can make a measurement to determine the particle's position, and that measurement will give you an answer. But there will be an inherent uncertainty associated with that measurement, where the uncertainty is caused by the quantum effects of nature.

How large is that uncertainty? It's related to both ħ and L, where ħ is Planck's constant and L is the size of the box.

For most of the experiments we perform, Planck's constant is small compared to any actual distance scale we're capable of probing, and so when we examine the uncertainty we get - related to both ħ and L - we'll see a small inherent uncertainty.

But what if L is small? What if L is so small that, relative to ħ, it's either comparably sized or even smaller?

This is where you can see the problem start to arise. These quantum corrections that occur in nature don't simply arise because there's the main, classical effect, and then there are quantum corrections of order ~ ħ that arise. There are corrections of all orders: ~ ħ, ~ ħ ², ~ ħ ³, and so on. There's a certain length scale, known as the Planck length, where if you reach it, the higher-order terms (which we usually ignore) become just as important as, or even more important than, the quantum corrections we normally apply.

What is that critical length scale, then? The Planck scale was first put forth by physicist Max Planck more than 100 years ago. Planck took the three constants of nature:

1. G, the gravitational constant of Newton's and Einstein's theories of gravity,

2. ħ, Planck's constant, or the fundamental quantum constant of nature, and

3. c, the speed of light in a vacuum,

and realized that you could combine them in different ways to get a single value for mass, another value for time, and another value for distance. These three quantities are known as the Planck mass (which comes out to about 22 micrograms), the Planck time (around 10⁻⁴³ seconds), and the Planck length (about 10⁻³⁵ meters). If you put a particle in a box that's the Planck length or smaller, the uncertainty in its position becomes greater than the size of the box.

But there's a lot more to the story than that. Imagine you had a particle of a certain mass. If you compressed that mass down into a small enough volume, you'd get a black hole, just like you would for any mass. If you took the Planck mass - which is defined by the combination of those three constants in the form of √( ħc/G) - and asked that question, what sort of answer would you get?

You'd find that the volume of space you needed that mass to occupy would be a sphere whose Schwarzschild radius is double the Planck length. If you asked how long it would take to cross from one end of the black hole to the other, the length of time is four times the Planck time. It's no coincidence that these quantities are related; that's unsurprising. But what might be surprising is what it implies when you start asking questions about the Universe at those tiny distance and time scales.

In order to measure anything at the Planck scale, you'd need a particle with sufficiently high energy to probe it. The energy of a particle corresponds to a wavelength (either a photon wavelength for light or a de Broglie wavelength for matter), and to get down to Planck lengths, you need a particle at the Planck energy: ~10 ¹⁹ GeV, or approximately a quadrillion times greater than the maximum LHC energy.

If you had a particle that actually achieved that energy, its momentum would be so large that the energy-momentum uncertainty would render that particle indistinguishable from a black hole. This is truly the scale at which our laws of physics break down.

When you examine the situation in greater detail, it only gets worse. If you start thinking about quantum fluctuations inherent to space (or spacetime) itself, you'll recall there's also an energy-time uncertainty relation. The smaller the distance scale, the smaller the corresponding timescale, which implies a larger energy uncertainty.

At the Planck distance scale, this implies the appearance of black holes and quantum-scale wormholes, which we cannot investigate. If you performed higher-energy collisions, you'd simply create larger mass (and larger size) black holes, which would then evaporate via Hawking radiation.

You might argue that, perhaps, this is why we need quantum gravity. That when you take the quantum rules we know and apply them to the law of gravity we know, this is simply highlighting a fundamental incompatibility between quantum physics and General Relativity. But it's not so simple.

Energy is energy, and we know it causes space to curve. If you start attempting to perform quantum field theory calculations at or near the Planck scale, you no longer know what type of spacetime to perform your calculations in. Even in quantum electrodynamics or quantum chromodynamics, we can treat the background spacetime where these particles exist to be flat. Even around a black hole, we can use a known spatial geometry. But at these ultra-intense energy, the curvature of space is unknown. We cannot calculate anything meaningful.

At energies that are sufficiently high, or (equivalently) at sufficiently small distances or short times, our current laws of physics break down. The background curvature of space that we use to perform quantum calculations is unreliable, and the uncertainty relation ensures that our uncertainty is larger in magnitude than any prediction we can make. The physics that we know can no longer be applied, and that's what we mean when we say that "the laws of physics break down."

But there might be a way out of this conundrum. There's an idea that's been floating around for a long time - since Heisenberg, actually - that could provide a solution: perhaps there's a fundamentally minimal length scale to space itself.

Of course, a finite, minimum length scale would create its own set of problems. In Einstein's theory of relativity, you can put down an imaginary ruler, anywhere, and it will appear to shorten based on the speed at which you move relative to it. If space were discrete and had a minimum length scale, different observers - i.e., people moving at different velocities - would now measure a different fundamental length scale from one another!

That strongly suggests there would be a "privileged" frame of reference, where one particular velocity through space would have the maximum possible length, while all others would be shorter. This implies that something that we currently think is fundamental, like Lorentz invariance or locality, must be wrong. Similarly, discretized time poses big problems for General Relativity.

Still, there may actually be a way to test whether there is a smallest length scale or not. Three years before he died, physicist Jacob Bekenstein put forth a brilliant idea for an experiment. If you pass a single photon through a crystal, you'll cause it to move by a slight amount.

Because photons can be tuned in energy (continuously) and crystals can be very massive compared to a photon's momentum, we could detect whether the crystal moves in discrete "steps" or continuously. With low-enough energy photons, if space is quantized, the crystal would either move a single quantum step or not at all.

At present, there is no way to predict what's going to happen on distance scales that are smaller than about 10⁻³⁵ meters, nor on timescales that are smaller than about 10⁻⁴³ seconds. These values are set by the fundamental constants that govern our Universe. In the context of General Relativity and quantum physics, we can go no farther than these limits without getting nonsense out of our equations in return for our troubles.

It may yet be the case that a quantum theory of gravity will reveal properties of our Universe beyond these limits, or that some fundamental paradigm shifts concerning the nature of space and time could show us a new path forward. If we base our calculations on what we know today, however, there's no way to go below the Planck scale in terms of distance or time. There may be a revolution coming on this front, but the signposts have yet to show us where it will occur.

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What Is The Smallest Possible Distance In The Universe?

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If you wanted to understand how our Universe operates, you'd have to examine it at a fundamental level. Macroscopic objects are made up of particles, which can only themselves be detected by going to subatomic scales. To examine the Universe's properties, you must to look at the smallest constituents on the smallest possible scales.

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You'll need to put your money on the table for this batch of tricks, then use your scientific knowledge to make 'cents' of what happens!

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Canicule : les gestes pour réduire la température chez soi sans clim

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Il est possible de rester au frais sans abuser de la climatisation, qui représente 10 % de la consommation électrique mondiale.

Article réservé aux abonnés

LA LISTE DE LA MATINALE

Cet été, votre mission, si vous l'acceptez : vous passer de la climatisation ! Energivore, elle représente 10 % de la consommation électrique mondiale, selon l'Agence internationale de l'énergie. Polluante, elle participe au réchauffement climatique en raison des fuites ou du mauvais recyclage des fluides frigorigènes, qui sont de puissants gaz à effet de serre. Calorifique, elle est en partie responsable de la " surchauffe urbaine ", en augmentant à elle seule de 1 à 1,5 °C la température en ville par rapport à celle de la campagne environnante - le différentiel total pouvant atteindre 8 °C en cas de canicule.

Or, si nous ne faisons rien pour limiter le réchauffement climatique, d'ici à la fin du siècle, nous pourrions aller vers des températures de 50 °C, voire supérieures à 55 °C. " Les vagues de chaleur vont doubler ou tripler de fréquence. Il est donc urgent d'adapter nos habitudes mais aussi les formes urbaines ", prévient Charlotte Izard, responsable climat et territoire au Réseau action climat.

Voici quelques solutions pour agir dès maintenant dans votre maison ou votre appartement.

Sur la canicule : une vague de chaleur sans précédent pour un mois de juin arrive en France

Niveau débutant : avoir la maîtrise de son air

Une façade d'hôtel, à Quiberon (Morbihan). ALAIN LE BOT / PHOTONONSTOP

1/Préserver la température intérieure. Pour vous qui débutez, cela va mieux en le disant : il faut fermer les volets en journée dès que le soleil tape sur la fenêtre ou le faire avant de partir travailler le matin. " Les volets roulants sont ceux qui isolent le mieux, l'air qu'ils renferment servant d'isolant ", explique Florence Clément, coordinatrice de l'information grand public à l'Agence de l'environnement et de la maîtrise de l'énergie (Ademe). Fermer aussi les fenêtres dès que la température extérieure dépasse celle de votre logement. Profiter de la nuit pour aérer, ce qui permet de refroidir les murs, les plafonds, les planchers, qui emmagasineront la fraîcheur pour la restituer dans la journée. Traquer les appareils électriques : en cas de grosse chaleur, pas question de cuire un poulet ou de travailler avec l'ordinateur portable sur les genoux.

Si vous disposez d'un étage sous les toits, la nuit, vous pouvez faire un courant d'air efficace appelé " effet cheminée " en ouvrant un Velux et une fenêtre en bas. " Cela créera un mouvement d'air ascendant plus à même de chasser la chaleur vers l'extérieur des combles ", poursuit Florence Clément. Si vous craignez de laisser une fenêtre ouverte en bas toute la nuit, scellez une grille devant l'ouverture.

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Canicule : les gestes pour réduire la température chez soi sans climatisation

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Il est possible de rester au frais sans abuser de la climatisation, qui représente 10 % de la consommation électrique mondiale. Article réservé aux abonnés LA LISTE DE LA MATINALE Cet été, votre mission, si vous l'acceptez : vous passer de la climatisation !

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Une expérience audacieuse décrit comment un atome change d'état. Elle sonde par là même les fondations de la mécanique quantique.

Article réservé aux abonnés

La mécanique quantique, la théorie qui décrit le monde microscopique des particules, aime bien jouer avec notre intuition et cultiver les paradoxes. Pêle-mêle et en simplifiant, elle autorise à passer par deux trous à la fois (dualité onde-corpuscule, en termes plus savants), à franchir les murs (effet tunnel), à créer des chats morts et vivants en même temps (superposition des états), à interagir instantanément à distance (intrication quantique), à téléporter des atomes...

Et maintenant, grâce à une équipe de l'université de Yale, elle proclame mystérieusement que " l'absence de signal constitue le signal ", selon les mots du responsable de cette équipe, Michel Devoret. " C'est joli de constater qu'en ne voyant rien on observe quelque chose, salue Jean-Michel Raimond, professeur émérite de Sorbonne Université, admiratif de ce travail publié dans Nature le 3 juin. Si j'écrivais un manuel scolaire, je mettrais cette expérience dedans ! "

L'équipe américaine est arrivée à cette nouvelle étrangeté en voulant étaler au grand jour l'un des plus anciens mystères de cette théorie, le saut quantique. Cette propriété désigne le fait que, pour les particules, le monde n'est pas continu, mais discontinu. Un atome, pour gagner de l'énergie, ne peut le faire que par paquets, l'équivalent de monter des marches d'escalier plutôt qu'arpenter un plan incliné. D'où le nom d'ailleurs de " quantique " pour la théorie : une particule change d'état si l'énergie apportée est suffisante pour la faire monter directement d'une marche, sinon elle reste dans le même état.

Mais si ces sauts quantiques existent bel et bien, permettant par exemple le phénomène du laser, longtemps la question s'est posée de savoir si ces sauts sont instantanés ou lents. A partir des années 1980, des équipes ont observé ces sauts, imprévisibles. L'équipe de Yale vient, elle, de filmer, à raison d'une image toutes les huit nanosecondes environ, un saut quantique qui dure deux microsecondes. Mieux, elle sait dire quand ce saut est en train d'avoir lieu, grâce à la technique dite du " chien des Baskerville ", comme l'a baptisée Michel Devoret. Dans ce roman de Conan Doyle, Sherlock Holmes démasque le coupable de meurtres en constatant que le chien de la famille n'a pas aboyé lors des assassinats ; ce qui prouve que le meurtrier était de la famille. L'absence de signal apporte l'information.

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Une expérience audacieuse décrit comment un atome change d'état. Elle sonde par là même les fondations de la mécanique quantique. Article réservé aux abonnés La mécanique quantique, la théorie qui décrit le monde microscopique des particules, aime bien jouer avec notre intuition et cultiver les paradoxes.

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Tenir la classe ou faire apprendre les élèves ?

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Tenir la classe ou faire apprendre les élèves ?

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xkcd.com is best viewed with Netscape Navigator 4.0 or below on a Pentium 3±1 emulated in Javascript on an Apple IIGS at a screen resolution of 1024x1. Please enable your ad blockers, disable high-heat drying, and remove your device from Airplane Mode and set it to Boat Mode.

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Cartes microcontrôleurs et programmation - Physique - Chimie - Pédagogie - Académie de Poitiers

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Programmer en Python nécessite l'installation de logiciels spécifiques pour écrire et interpréter ce code facilement. Ces logiciels sont appelés I.D.E. pour "environnements de développement intégrés", et il en existe plusieurs pour Python. Ce document décrit pour les enseignants de physique chimie, les procédures d'installation des principaux IDE, ainsi que quelques utilitaires.
Ce document présente également des logiciels pour commander les cartes Arduino et Micro:bit.

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Programmer en Python nécessite l'installation de logiciels spécifiques pour écrire et interpréter ce code facilement. Ces logiciels sont appelés I.D.E. pour "environnements de développement intégrés", et il en existe plusieurs pour Python. Ce document décrit pour les enseignants de physique chimie, les procédures d'installation des principaux IDE, ainsi que quelques utilitaires.

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Nouveau lycée : une opportunité pour accéder aux classes préparatoires - Ministère de l'Éducation nationale et de la Jeunesse

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Ministère de l'Education Nationale et de la Jeunesse

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Les attentes communes aux classes préparatoires sont en cohérence avec les évolutions du lycée et du nouveau baccalauréat.

avoir du goût pour l'exploration approfondie de savoirs nouveaux et le croisement des disciplines ;

disposer d'un bon niveau de connaissances dans les disciplines fortes de la classe préparatoire envisagée ;

posséder des aptitudes à un travail approfondi et des capacités d'organisation ;

montrer des qualités de réflexion, d'argumentation et de rédaction et être apte à mener des raisonnements rigoureux.

Le nouveau lycée est ainsi un atout pour faciliter le parcours des élèves vers ces classes préparatoires, dites CPGE, avec une offre d'enseignements nouveaux et enrichis, une diversification des parcours des élèves et le développement d'une offre des enseignements les moins courants (langues et cultures de l'antiquité, numérique et informatique, arts).

[Infographie] Bac général 2021 : de nouveaux parcours vers les classes prépa

[Infographie] Bac technologique 2021 : de nouveaux parcours vers les classes prépa

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Nouveau lycée : une opportunité pour accéder aux classes préparatoires

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Les classes préparatoires aux grandes écoles (CPGE) forment les étudiants et les préparent aux concours d’entrée dans les grandes écoles en deux ans. Ce sont des formations sélectives : les élèves de lycée général ou technologique sont retenus par les établissements via Parcoursup, sur des critères…

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Différencier son enseignement au collège et au lycée - Les Cahiers pédagogiques

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" Il n'y a de pédagogie que "différenciée" ". C'est par cette affirmation franche et tranchée que Philippe Meirieu commet l'avant-propos de cet ouvrage élaboré à plusieurs mains ! Les auteurs constituent " une équipe d'enseignants " (presqu'au complet !), portant des casquettes multiples de praticiens et de formateurs dans l'institution scolaire, composée de Frédéric Bablon, DASEN de l'Aube, Pascal Claman, professeur de lettres , Guylaine Raphael-Manhaval et Olivier Letot, professeurs de mathématiques, Marie-Noëlle Bertille professeure d'anglais et Sophie Moutard professeure d'histoire géographie.

Les auteurs convoquent les principes et enjeux de la différenciation, en s'appuyant sur des chercheurs qui se sont intéressés de près à l'enjeu de l'hétérogénéité des classes, comme Philippe Perrenoud, Sabine Khan, Jacques Lévine et Jeanne Moll, Marie Toullec-Théry, Jean-Michel Zakhartchouk.

Ils se rallient en fait à la définition de la différenciation de Philippe Perrenoud, qui est : " une démarche qui cherche à mettre en œuvre un ensemble diversifié de moyens et de procédures d'enseignement et d'apprentissage afin de permettre à des élèves d'âge, d'aptitude, de comportement et savoir-faire hétérogènes, mais regroupés dans une même division, d'atteindre par des voies différentes des objectifs communs ou en partie communs " (p.17).

Ils s'appuient sur les constats du rapport de la conférence de consensus CNESCO de 2017 pour nous rappeler l'urgence de différencier l'enseignement à partir du principe unanime que tous les élèves n'apprennent pas au même rythme, ni de la même manière, ne sont pas égaux face aux obstacles, parfois régulier et ordinaires de l'apprentissage. Les prudences de Sabine Kahn sont apportées pour ne pas confondre une " pédagogie différenciée " avec une " pédagogie différenciatrice ", une pédagogie qui renforcerait et amplifierait les inégalités et les différences entre les élèves par la mise en œuvre de pédagogies différentes en fonction des élèves, sur la simplification des exercices ou encore par l'externalisation de la classe de l'aide apportée aux élèves.

Pour les auteurs, en s'appuyant également sur leurs expériences de praticiens, la différenciation pédagogique consiste en une approche globale composée par quatre grands principes. 1. instaurer une relation de qualité avec les élèves ; 2. prendre en compte le rythme d'apprentissage de chacun ; 3. proposer un étayage personnalisé ; 4. mettre en œuvre une évaluation au service du progrès de chacun.

Au travers chacun des chapitres, les notions de lien, du temps, d'étayage et d'évaluation sont explorées. Le lecteur trouve des pistes de compréhension de ces enjeux pédagogiques et éducatifs, quelques repérages de la recherche en éducation, mais surtout un choix prioritaire pour les réflexions et raisonnements professionnels, étayés par des témoignages de l'expérience du travail éducatif des auteurs.

Ce véritable "guide pratique", sera utile à qui veut s'aventurer sur le chemin de la différenciation, qu'il soit débutant ou non. Les exemples concrets le rassureront peut-être et l'ensemble, avec ses multiples références à des travaux divers, lui donnera peut-être envie d'aller plus loin...
Andreea Capitanescu-Benetti

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Différencier son enseignement au collège et au lycée

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" Il n'y a de pédagogie que "différenciée" ". C'est par cette affirmation franche et tranchée que Philippe Meirieu commet l'avant-propos de cet ouvrage élaboré à plusieurs mains !

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Interface de raccourcisseur d'URL publique   QR code

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Choisissez votre propre URL

Cet outil vous permet de personnaliser une adresse URL trop longue selon votre choix. Entrez votre adresse URL longue dans le champ ci-dessous et choisissez une adresse courte de votre choix. Si cette adresse n'est pas déjà utilisée, elle est à vous. De plus, un code QR est automatiquement généré.

Nouveauté! MonURL.ca vous permet maintenant d'accéder aux statistiques de vos liens raccourcis. Il suffit d'ajoutet le symbole " + " à votre lien court. Par exemple : monurl.ca/recitdp+. De plus, ce lien vous permet aussi de retrouver votre code QR sous l'onglet " Partager ".

Entrez une nouvelle URL à être racccourcie

Ce site est dédié à l'éducation.

Tout lien jugé inapproprié sera enlevé. Toute utilisation inappropriée pourrait entraîner un blocage de votre adresse IP.

Grâcieuseté du

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Interface de raccourcisseur d'URL publique

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Cet outil vous permet de personnaliser une adresse URL trop longue selon votre choix. Entrez votre adresse URL longue dans le champ ci-dessous et choisissez une adresse courte de votre choix. Si cette adresse n'est pas déjà utilisée, elle est à vous. De plus, un code QR est automatiquement généré.

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📰 Vers des batteries fonctionnant dans l'eau de mer

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📰 Vers des batteries fonctionnant dans l'eau de mer

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© Perticarari et al. 2019 Des scientifiques de l'Institut des matériaux Jean Rouxel et du laboratoire Chimie et interdisciplinarité, synthèse, analyse, modélisation (IMN et CEISAM, CNRS/Université de Nantes) ont découvert un matériau (Un matériau est une matière d'origine naturelle ou artificielle que l'homme façonne pour en faire des objets.

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Speech2Face: Learning the Face Behind a Voice

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"On Learning Associations of Faces and Voices", C. Kim, H. V. Shin, T.-H. Oh, A. Kaspar, M. Elgharib, and W. Matusik, ACCV 2018 "Wav2Pix: speech-conditioned face generation using generative adversarial networks", A. Duarte, F. Roldan, M. Tubau, J. Escur, S. Pascual, A. Salvador, E. Mohedano, K. McGuinness, J. Torres, and X. Giroi-Nieto, ICASSP 2019 "Disjoint mapping network for cross-modal matching of voices and faces", Y. Wen, M. A. Ismail, W. Liu, B. Raj, and R. Singh, ICLR 2019"Putting the face to the voice: Matching identity across modality", M. Kamachi, H. Hill, K. Lander, and E. Vatikiotis-Bateson, Current Biology, 2003

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Speech2Face: Learning the Face Behind a Voice

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"On Learning Associations of Faces and Voices", C. Kim, H. V. Shin, T.-H. Oh, A. Kaspar, M. Elgharib, and W. Matusik, ACCV 2018 "Wav2Pix: speech-conditioned face generation using generative adversarial networks", A. Duarte, F. Roldan, M. Tubau, J. Escur, S. Pascual, A. Salvador, E. Mohedano, K. McGuinness, J. Torres, and X.

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When Will The Universe Get Its First 'Black Dwarf' Star?

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The Big Bang happened approximately 13.8 billion years ago, and it might have only taken 50-100 million years to form the very first stars. Ever since then, the Universe has been flooded with starlight. When enough matter - mostly hydrogen and helium gas - gravitates together into a single, compact object, nuclear fusion must take place inside the core, giving rise to a true star.

But as time goes on and fusion continues, eventually that star will run out of fuel. Sometimes, the star is massive enough that additional fusion reactions will take place, but at some point, it all must stop. Even when a star finally dies, however, their remnants will continue to shine. In fact, except for black holes, every remnant ever created still shines today. Here's the story of how long we'll need to wait for the first star to truly go dark.

It all begins from clouds of gas. When a cloud of molecular gas collapses under its own gravity, there are always a few regions that start off just a little bit denser than others. Every location with matter in it does its best to attract more and more matter towards it, but these overdense regions attract matter more efficiently than all the others. Because gravitational collapse is a runaway process, the more matter you attract to your vicinity, the faster additional matter will flow inward.

While it can take millions to tens of millions of years for a molecular cloud to go from a large, diffuse state to a relatively collapsed one, the process of going from a collapsed state of dense gas to a new cluster of stars - where the densest regions ignite fusion in their cores - takes only a few hundred thousand years.

Stars come in a huge variety of colors, brightnesses and masses, and a star's life cycle and fate are determined from the moment of the star's birth. When you create a new cluster of stars, the easiest ones to notice are the brightest ones, which also happen to be the most massive. These are the brightest, bluest, hottest stars in existence, with up to hundreds of times the mass of our Sun and with millions of times the luminosity.

But despite the fact that the brightest ones are the stars that appear the most spectacular, these are also the rarest stars, making up far less than 1% of all the known, total stars. They are also the shortest-lived stars, as they burn through all the nuclear fuel (in all the various stages) in their cores in as little as 1-2 million years.

When these stars, the brightest and most massive ones of all, run out of fuel, they die in a spectacular type II supernova explosion. When this occurs, the inner core implodes, collapsing all the way down to a neutron star (for the low-mass cores) or even to a black hole (for the high-mass cores), while expelling the outer layers back into the interstellar medium.

Once there, these enriched gases will contribute to future generations of stars, providing them with the heavy elements necessary to create rocky planets, organic molecules, and in rare, wonderful cases, life. It is estimated that at least six prior generations of stars contributed to the molecular gas cloud that eventually gave rise to our Sun and Solar System.

If you form a black hole from the collapse of a supermassive star, you don't have to wait very long for it to go dark. In fact, by definition, black holes go almost perfectly "black" immediately. Once the core collapses sufficiently to form an event horizon, everything inside collapses down to a singularity in a fraction of a second. Any remnant heat, light, temperature, or energy in any form in the core simply gets added to the mass of the singularity.

No light will ever emanate from it again, except in the form of Hawking radiation, which is emitted when the black hole decays, and in the accretion disk surrounding the black hole, which is constantly fed and refueled from the surrounding matter. But not every massive star forms a black hole, and the ones that form neutron stars tell a vastly different story.

A neutron star takes all the energy in a star's core and collapses incredibly rapidly. When you take anything and compress it quickly, you cause the temperature within it to rise: this is how a piston works in a diesel engine. Well, collapsing from a stellar core all the way down to a neutron star is maybe the ultimate example of rapid compression.

In the span of seconds-to-minutes, a core of iron, nickel, cobalt, silicon and sulfur many hundreds-of-thousands of miles (kilometers) in diameter has collapsed down to a ball just around 10 miles (16 km) in size or smaller. Its density has increased by around a factor of a quadrillion (10 ¹⁵), and its temperature has grown tremendously: to some 10 ¹² K in the core and all the way up to around 10 ⁶ K at the surface. And herein lies the problem.

You have all this energy stored within a collapsed star like this, and its surface is so tremendously hot that it not only glows bluish-white in the visible portion of the spectrum, but most of the energy isn't visible or even ultraviolet: it's X-ray energy! There is an insanely large amount of energy stored within this object, but the only way it can release it out into the Universe is through its surface, and its surface area is very small. The big question, of course, is how long will it take a neutron star to cool?

The answer depends on a piece of physics that practically isn't well-understood for neutron stars: neutrino cooling! You see, while photons (radiation) are soundly trapped by the normal, baryonic matter, neutrinos, when generated, can pass right through the entire neutron star unimpeded. On the fast end, neutron stars might cool down, out of the visible portion of the spectrum, after as little as 10 ¹⁶ years, or "only" a million times the age of the Universe. But if things are slower, it might take 10 ²⁰-to-10 ²² years, which means you'll be waiting for some time.

But other stars will go dark much more quickly. You see, the vast majority of stars - the other 99+% - don't go supernova, but rather, at the end of their lives, contract (slowly) down into a white dwarf star. The "slow" timescale is only slow compared to a supernova: it takes tens-to-hundreds of thousands of years rather than mere seconds-to-minutes, but that's still fast enough to trap almost all the heat from the star's core inside.

The big difference is that instead of trapping it inside of a sphere with a diameter of only 10 miles or so, the heat is trapped in an object "only" about the size of Earth, or around a thousand times larger than a neutron star. This means that while the temperatures of these white dwarfs can be very high - over 20,000 K, or more than three times hotter than our Sun - they cool down much faster than neutron stars.

Neutrino escape is negligible in white dwarfs, meaning that radiation through the surface is the only effect that matters. When we calculate how quickly heat can escape by radiating away, it leads to a cooling timescale for a white dwarf (like the kind the Sun will produce) of around 10 ¹⁴-to-10 ¹⁵ years. And that will get your stellar remnant all the way down to just a few degrees above absolute zero!

This means that after around 10 trillion years, or "only" around 1,000 times the present age of the Universe, the surface of a white dwarf will have dropped in temperature so that it's out of the visible light regime. When this much time has passed, the Universe will possess a brand new type of object: a black dwarf star.

I'm sorry to disappoint you, but there aren't any black dwarfs around today. The Universe is simply far too young for it. In fact, the coolest white dwarfs have, to the best of our estimates, lost less than 0.2% of their total heat since the very first ones were created in this Universe. For a white dwarf created at 20,000 K, that means its temperature is still at least 19,960 K, telling us we've got a terribly long way to go, if we're waiting for a true dark star.

We currently conceive of our Universe as littered with stars, which cluster together into galaxies, which are separated by vast distances. But by time the first black dwarf comes to be, our local group will have merged into a single galaxy (Milkdromeda), most of the stars that will ever live will have long since burned out, with the surviving ones being exclusively the lowest-mass, reddest and dimmest stars of all. And beyond that? Only darkness, as dark energy will have long since pushed away all the other galaxies, making them unreachable and practically unmeasurable by any physical means.

And yet, amidst it all, a new type of object will come to be for the very first time. Even though we'll never see or experience one, we know enough of nature to know not only that they'll exist, but how and when they'll come to be. And that, in itself - the ability to predict the far-distant future that has not yet come to pass - is one of the most amazing parts of science of all!

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When Will The Universe Get Its First 'Black Dwarf' Star?

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The Big Bang happened approximately 13.8 billion years ago, and it might have only taken 50-100 million years to form the very first stars. Ever since then, the Universe has been flooded with starlight. When enough matter - mostly hydrogen and helium gas - gravitates together into a single, compact object, nuclear fusion must take place inside the core, giving rise to a true star.

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Il y a un siècle, l'éclipse qui confirme Einstein - Sciences et Avenir

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PHYSIQUE. C'était exactement un siècle, et la date est restée gravée dans la mémoire des physiciens. Ce jour-là, le 29 mai 1919, le physicien britannique Arthur Eddington apportait au monde entier la première preuve observationnelle de la relativité générale d' Albert Einstein. Une éclipse de Soleil était alors visible depuis les îles Sao Tomé et Principe, un archipel dans l'Atlantique Sud dans le golfe de Guinée à environ 240 km des côtes du Gabon. L'astrophysicien avait organisé un long périple pour tenter d'observer un subtil effet prédit par Einstein : une masse importante courbe l'espace et dévie la lumière d'une étoile lointaine. Cette courbure de l'espace est la conséquence de la relativité générale.

Des étoiles visibles en plein jour

Or, au moment de l'éclipse pendant la phase de totalité, le ciel s'assombrit en plein jour et les étoiles deviennent visibles. Entre autres, les étoiles de l'amas des Hyades dont l'écart angulaire était alors bien connu. Si Einstein disait vrai, au moment de l'éclipse, leur lumière devait passer à proximité du Soleil. Si la masse de l'étoile - en conformité avec la théorie du physicien - courbe bien l'espace, alors les étoiles ne devraient plus apparaître à leur position habituelle. Selon les calculs effectués par Einstein, l'ensemble des Hyades devait apparaître décalé de 1,75 seconde d'arc. En fait tous les jours sans éclipse, à chaque fois que le Soleil se trouve dans le ciel proche de ces étoiles, cette déviation devait bien exister, sauf qu'en plein jour, il n'est pas possible de les repérer. Il fallait bien profiter de l'éclipse totale pour les surprendre. Cette fois-ci, la phase de totalité de l'éclipse durait 6 longues minutes, de quoi observer tranquillement. C'est au cours de ces 6 minutes qu'Eddington constate le décalage "apparent" de l'amas des 'Hyades conformément aux prédictions d'Einstein.

Einstein a raison

De retour en Europe il présente ses résultats à la conférence de la Royal Astronomical Society à Londres, le 15 novembre 1919. Il signe ainsi le triomphe de la relativité générale, qui a été par la suite testée de nombreuses fois dans toutes les situations. Arthur Eddington, pacifiste - il était d'une famille de quakers - avait refusé de servir dans l'armée pendant la Première Guerre mondiale. C'est ainsi qu'en 1915 il avait reçu l'article relatif à la relativité générale. Il fut l'un des rares physiciens de son époque à avoir compris le caractère révolutionnaire du travail d'Einstein.

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Il y a un siècle, l'éclipse qui confirme la théorie de la relativité générale d'Einstein

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PHYSIQUE. C'était exactement un siècle, et la date est restée gravée dans la mémoire des physiciens. Ce jour-là, le 29 mai 1919, le physicien britannique Arthur Eddington apportait au monde entier la première preuve observationnelle de la relativité générale d' Albert Einstein.

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PhET: Des simulations gratuites en physique, chimie, biologie, sciences de la Terre et mathématiques

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Fondée en 2002 par le prix Nobel Carl Wieman , le projet de Simulations interactives PhET à l'Université du Colorado Boulder, crée des simulations mathématiques et de sciences interactives gratuites . Les sims Phet sont basées sur une formation approfondie la recherche et le fait de faire participer les élèves, à travers environnement intuitif, ressemblant à un jeu.

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Netboard. Un tableau blanc en ligne gratuit et collaboratif • Les Outils Tice

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Article mis à jour le 22 mai 2019 par Fidel Navamuel

Netboard est un outil en ligne gratuit et facile à utiliser qui va vous permettre de collecter, d'organiser et de partager n'importe quel contenu Web seul ou en mode collaboratif. Idéal pour proposer des ressources en ligne à vos étudiants ou pour les initier à la curation en équipes.

Netboard fait bien sûr irrémédiablement penser à des outils comme Padlet et c'est normal. Le fonctionnement et les usages sont assez similaires.

Un tableau blanc virtuel simple et complet

Netboard permet de créer très simplement de belles pages dans des tableaux avec des textes, des liens, des documents, des vidéos, des photos, des présentations, des flux RSS et autres contenus. Chaque tableau thématique peut regrouper plusieurs pages dans lesquelles on peut déposer à peu de chose près tout type de ressources.

Vous pouvez ensuite les organiser ou les réordonner très simplement du bout de la souris. Vous pouvez ajouter une ressource à un tableau via son URL, vous pouvez la télécharger, insérer un code embarqué fourni par un site ou un service. Vous avez aussi la possibilité d'utiliser une extension pour Chrome ou Firefox qui va vous faciliter la captation de contenus. Tout cela fonctionne à merveille.

Un tableau blanc collaboratif

Netboard est particulièrement adapté au travail collaboratif. Le créateur de la page peut la rendre publique ou privée, ilpeut gérer les autorisations et permettre de lire et/ou modifier le contenu de la page aux différents membres d'une équipe. Très pratique vous pouvez partager les liens d'accès à une page avec des participants qui n'ont pas de compte netboard. Ils pourront voir vos pages privées, commenter et éditer sans avoir besoin de s'enregistrer.

Vos pages Netboard se consultent en ligne mais vous pouvez aussi les exporter au format PDF interactif.

Un bon service de curation en équipe qui a l'avantage d'être entièrement gratuit.

L'interface est en anglais mais vous n'avez pas besoin de maîtriser la langue pour pouvoir utiliser l'outil.

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Netboard. Un tableau blanc en ligne gratuit et collaboratif - Les Outils Tice

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Article mis à jour le 22 mai 2019 par Fidel Navamuel Netboard est un outil en ligne gratuit et facile à utiliser qui va vous permettre de collecter, d'organiser et de partager n'importe quel contenu Web seul ou en mode collaboratif.

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L'Allemagne compte le plus de sociétés contrevenant au règlement Reach censé protéger la santé et l'environnement des Européens.

Article réservé aux abonnés

Les substances chimiques se retrouvent dans une large gamme de produits de grande consommation, des cosmétiques aux jouets. ALAIN JOCARD / AFP

La scène se passe en novembre 2018 au Parlement européen, à Strasbourg. Auditionné devant la commission environnement et santé publique, le directeur de l'Agence européenne des produits chimique (ECHA), Bjorn Hansen, finit par admettre que les deux tiers des dossiers instruits par ses services ne sont pas conformes à la réglementation Reach (pour Registration, evaluation, authorisation and restriction of chemicals en anglais, ou " Enregistrement, évaluation, autorisation et restriction des substances chimiques ") censée protéger la santé et l'environnement. Passé au grill par des députés qui dénoncent un " dieselgate de l'industrie de la chimie ", en référence à la fraude des constructeurs automobiles sur les émissions de gaz polluants, le patron de l'ECHA refuse cependant de livrer le nom des entreprises contrevenantes et des produits concernés.

Des documents révélés mardi 21 mai par la plus grande association environnementale allemande, Bund, auxquels Le Monde a eu accès, permettent de lever un coin du voile. Au moins 654 entreprises, à travers l'Europe, emploient massivement des substances de synthèse qui enfreignent le règlement Reach et sont donc potentiellement dangereuses.

Entré en vigueur depuis 2007, ce dernier contraint les industriels à fournir les informations (toxicité, écotoxicité, devenir dans l'environnement, etc.) nécessaires à l'évaluation de la dangerosité des produits qu'ils fabriquent ou importent suivant le principe " pas de données, pas de marché ".

A la demande du gouvernement allemand, l'Institut fédéral allemand d'évaluation des risques (BfR), équivalent de l'Agence française de sécurité sanitaire (Anses), a cherché à éprouver l'efficacité dudit règlement. Révélés par Le Monde en octobre 2018, les résultats des travaux du BfR ont mis au jour des trous béants dans la raquette. Pour 940 substances, les données sont " non conformes ", soit par absence pure et simple d'information, soit par manque d'étude scientifique prouvant leur innocuité. Les données fournies par les industriels sont jugées particulièrement insuffisantes pour les risques écotoxicologiques, mutagènes et reprotoxiques.

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Au moins 654 entreprises ne respectent pas la réglementation sur les substances chimiques

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L'Allemagne compte le plus de sociétés contrevenant au règlement Reach censé protéger la santé et l'environnement des Européens. Article réservé aux abonnés La scène se passe en novembre 2018 au Parlement européen, à Strasbourg.

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The kilo is dead. Long live the kilo! | MIT News

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For 130 years, a cylinder made of a platinum-iridium alloy and stored in a suburb of Paris called Saint Cloud has been the official definition of a kilogram, the internationally accepted basic unit of mass. But that will change once and for all on May 20, when for the first time all of the basic units of measurement will be officially defined in terms of atomic properties and fundamental physics constants, rather than specific, human-made objects.

The other objects on which physical standards are based, such as the standard meter, were already replaced years ago, but the kilogram - generally known as the kilo for short - turned out to be a harder unit to define in absolute terms. Physicists and engineers have been frustrated, however, by the inevitable imprecision of a unit based on a single physical object.

Despite the greatest of precautions, every time the standard kilo was handled - for example, to compare it to another unit that could then be used to calibrate instruments - it would shed some atoms and its mass would be slightly changed. Over its lifetime, that standard kilo is estimated to have lost about 50 micrograms. A better way was needed.

Now, instead of a particular lump of metal in a single location, a kilo is to be defined by fixing the numerical value of a fundamental constant of nature known as the Planck constant. This constant relates the energy of a photon to its frequency, and is referred to by the letter h. It is now defined as 6.62607015 times 10⁻³⁴ kilograms times square meters per second, thereby defining the kilogram in terms of the second and the meter. Since the second and meter are already defined completely in terms of physical constants, the kilogram is now also defined only in terms of fundamental physical constants.

Some may find this new definition complicated and difficult to understand, but Wolfgang Ketterle, a Nobel Prize winner and the John D. MacArthur Professor of Physics at MIT, doesn't see it that way. "Conceptually, the definition is very simple," he says.

Ketterle notes that the new definition of a kilogram corresponds to the mass of an exact number of particles - a very large number of particles. According to his formulation, it is 1.4755214 times 10 40 photons (particles of light) of a particular wavelength, which is that of cesium atoms used in atomic clocks.

No, that's not exactly something your butcher can place on a scale to measure out a kilo of ground beef, but it is something that scientists and engineers everywhere in the world - and even aliens on other worlds - could match precisely, without having to carry a scale to Paris to check it.

Ketterle sees this important shift in measurement standards as a teachable moment, an opportunity to explain some basic principles to a wide audience. "Ideally, every high school teacher would tell his or her science class about this historic change," he suggests.

To mark the occasion of the official change, which takes place on World Metrology Day, May 20, Ketterle will deliver a talk on the new standards at 4 p.m. that day in MIT's Huntington Hall, room 10-250, where he will explain both the concepts behind the new definition of the kilogram and the techniques for its measurement.

Explaining how the other basic units have been defined through basic physical constants is a bit more straightforward than it is for the kilo: The second, for example, is defined as a specific number of vibrations of an atom of cesium. The meter, no longer a metal bar in Saint Cloud, is now defined as the distance that light travels (in a vacuum) in a specific interval of time, namely 1/299,792,458 of a second.

Defining the kilo through the mass of photons has to address the fact that photons are constantly whizzing around at the speed of light - after all, they are light - so getting them to sit still on a balance scale is not possible. Instead, they can be trapped between a pair of mirrors, which form an "optical cavity" that keeps them confined. Then, that cavity and its trapped photons can be placed on a balance and measured. The difference between an empty cavity and an identical one full of photons thus provides the mass of the photons themselves. So that's the concept behind measuring a kilo according to the new definition.

However, collecting 10 40 photons - that's 1 with 40 zeros after it - is not practical, so instead measurements are made of a much smaller number, and then scaled up step by step. "How do you count to 10 ⁴⁰? Well, you can't," Ketterle says. "However, you can do it by using multiple steps."

He explains this process by analogy to money: "If you win a million dollars, and it is paid in pennies, you don't want to count pennies. You will first exchange the pennies into dollar bills, and then the dollar bills into 100 dollar bills, and then you count them."

That's essentially the principle used for measuring mass, he says. "In metrology, something analogous is done by comparing the atomic clock frequency of the cesium atoms to a much higher atomic frequency. Then you use this frequency to measure the mass of the electron or of a single atom, and only then you start counting," he says.

In practice, there are currently two known methods for measuring such masses with great precision. These are known as the Kibble balance and the single-crystal silicon sphere. Both are techniques that laboratories around the world can now use to provide a precise standard for mass and measurements of weights, without ever again having to correlate their measurements with a specific physical object at some central repository.

What's more, now that these units are defined in absolute terms, as soon as better measurement techniques are developed, the accuracy of these measurements will improve accordingly, without the need to revisit the underlying definitions.

The new definitions have great power, Ketterle says, because "every new method to count photons or atoms or measure frequencies will further improve the measurements of mass, since mass is no longer connected to an imprecise, man-made artifact."

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The international standard measurement of the kilogram is being officially changed on May 20, for the first time making all standard units defined in terms of basic physical principles instead of particular human-made objects. MIT professor and Nobel laureate Wolfgang Ketterle explains the change.

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CO2 in the atmosphere just exceeded 415 parts per million for the first time in human history | TechCrunch

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The human race has broken another record on its race to ecological collapse. Congratulations humanity!

For the first time in human history - not recorded history, but since humans have existed on Earth - carbon dioxide in the atmosphere has topped 415 parts per million, reaching 415.26 parts per million, according to sensors at the Mauna Loa Observatory, a research outpost of the National Oceanic and Atmospheric Agency.

The macabre milestone was noted on Twitter by the climate reporter Eric Holthaus, based on the data recorded and presented by the Scripps Institution of Oceanography at the University of California, San Diego.

This is the first time in human history our planet's atmosphere has had more than 415ppm CO2.

Not just in recorded history, not just since the invention of agriculture 10,000 years ago. Since before modern humans existed millions of years ago.

We don't know a planet like this. https://t.co/azVukskDWr

- Eric Holthaus (@EricHolthaus) May 12, 2019

If the threshold seems unremarkable (it shouldn't), it's yet another indication of the unprecedented territory humanity is now charting as it blazes new trails toward environmental catastrophe.

Just last week a report revealed that at least 1 million species were at risk of extinction thanks to human activity and the carbon emissions that are a byproduct of economic development.

That's on top of news that climate change, which has been inextricably linked to carbon emissions, will cost the U.S. alone some $500 billion per year by 2090.

The increasing proportion of carbon dioxide in the atmosphere is important because of its heat absorbing properties. The land and seas on the planet absorb and emit heat, and that heat is trapped in carbon dioxide molecules. The NOAA likens CO2 to leaving bricks in a fireplace that still emit heat after a fire goes out.

Greenhouse gases contribute to the planet maintaining a temperature that can sustain life, but too much can impact the entire ecosystem that sustains us. That's what's happening now. As the NOAA notes, "increases in greenhouse gases have tipped the Earth's energy budget out of balance, trapping additional heat and raising Earth's average temperature."

The properties of CO2 also mean that it adds to the greenhouse effect in a way that other emissions do not, thanks to its ability to absorb wavelengths of thermal energy that things like water vapor can't. That's why increases of atmospheric carbon dioxide are responsible for about two-thirds of the total energy imbalance causing Earth's temperature to rise, according to the NOAA.

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CO2 in the atmosphere just exceeded 415 parts per million for the first time in human history

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The human race has broken another record on its race to ecological collapse. Congratulations humanity! For the first time in human history - not recorded history, but since humans have existed on Earth - carbon dioxide in the atmosphere has topped 415 parts per million, reaching 415.26 ...

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Germany tests its first 'electric highway' for trucks

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The very first eHighway launched in Sweden in 2016. The concept here is the same -- the trucks use pantographs (the pickps on their roofs) to latch on to the overhead cables and draw electricity. Trucks can feed electricity into the grid when they brake, making the system particularly useful if there's ever a jam.

The system won't have a major impact for a while. Just five trucks will run the electrified stretch each day where roughly 10 percent of the road's 135,000 daily vehicles are heavy trucks. That reduced emissions footprint could scale up as more trucks support the system, though, and could encourage trucking companies to go electric knowing that their cargo haulers could drive longer on a charge.

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Germany tests its first 'electric highway' for trucks

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The very first eHighway launched in Sweden in 2016. The concept here is the same -- the trucks use pantographs (the pickps on their roofs) to latch on to the overhead cables and draw electricity. Trucks can feed electricity into the grid when they brake, making the system particularly useful if there's ever a jam.

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L’UE a réduit ses émissions de CO2 en 2018, mais en ordre dispersé

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La réduction globale de 2,5 % a été limitée par de fortes hausses de CO2 en Pologne et en Slovaquie. L'UE s'est engagée à réduire ses émissions de 20 % par rapport à leurs niveaux de 1990 en 2020.

Les pays de l'UE ont réduit de 2,5 % leurs émissions de CO ₂ en 2018, mais l'effort a été limité par de fortes hausses enregistrées en Pologne et en Slovaquie, a annoncé mercredi 8 mai l'Office européen de statistiques Eurostat. La France, elle, fait un peu mieux que la moyenne : elle a réduit ses émissions de CO ₂ de 3,5 %. Les émissions de CO ₂ provenant de la combustion des énergies fossiles ont globalement diminué dans 20 des 28 Etats membres.

Les plus fortes baisses ont été constatées dans les pays suivants :

Portugal (- 9 % par rapport à 2017)

Bulgarie (- 8,1 %)

Irlande (- 6,8 %)

Allemagne (- 5,4 %)

Pays-Bas (- 4,6 %)

Croatie (- 4,3 %)

Grèce (- 3,6 %)

Italie (- 3,5 %)

France (- 3,5 %)

Les émissions ont en revanche continué à progresser dans plusieurs Etats membres :

Lettonie (+ 8,5 %)

Malte (+ 6,7 %)

Estonie (+ 4,5 %)

Luxembourg (+ 3,7 %)

Pologne (+ 3,5 %)

Slovaquie (+ 2,4 %)

Finlande (+ 1,9 %)

L'Allemagne représente 22 % des émissions de l'UE

En 2018, l'Allemagne était le plus gros contributeur (22 %) des émissions de CO ₂ dans l'UE, suivie par le Royaume-Uni (11,4 %), la Pologne (10 %), la France (10 %) et l'Italie (10 %). Si la Lettonie a fortement augmenté ses émissions en 2018, elle ne pèse que pour 0,2 % du total.

Les émissions de CO ₂ contribuent fortement au réchauffement de la planète et représentent environ 80 % de l'ensemble des émissions de gaz à effet de serre dans l'UE. Cette dernière s'est engagée à réduire ses émissions de gaz à effet de serre de 20 % par rapport à leurs niveaux de 1990 en 2020 et de 40 % en 2030.

Or les engagements des pays, dont ceux de l'UE, sont insuffisants pour respecter l'objectif de limiter le réchauffement bien en dessous de 2 °C, et si possible en dessous de 1,5 °C, comme le prévoit l'accord de Paris de 2015.

Lire notre analyse : Climat : l'inertie coupable de l'Union européenne

Un appel de huit pays de l'UE pour " agir maintenant "

Une usine de Porsche à Leipzig en Allemagne. JAN WOITAS / AFP

Huit pays de l'UE ont par ailleurs lancé un appel commun avant le sommet européen de Sibiu (Roumanie), jeudi, pour " agir maintenant " contre le réchauffement climatique, a indiqué l'Elysée. " Du fait de son importance fondamentale pour l'avenir de l'Europe, comme défi et comme opportunité, la lutte contre le changement climatique doit être la clef de voûte de l'agenda stratégique européen pour la période 2019-2024 ", affirme le texte signé par la Belgique, le Danemark, l'Espagne, la France, le Luxembourg, les Pays-Bas, le Portugal et la Suède.

Cette initiative a été prise, selon la présidence française, par " les pays les plus ambitieux en matière climatique " pour ne pas que " les plus réticents (...) donnent le ton ", alors que les dirigeants européens doivent discuter à Sibiu de l'agenda européen pour les cinq prochaines années qui suivront les élections européennes du 26 mai.

Ce texte a été envoyé à l'ensemble des pays membres de l'UE avec l'espoir que " d'autres le signeront avant ou après Sibiu ", a indiqué l'Elysée. L'Allemagne a été " associée " à cette démarche mais " n'a pas à ce stade voulu la soutenir " pour " des questions internes ", précise-t-on de même source.

Le texte appelle l'UE à respecter l'objectif " d'atteindre zéro émission de gaz à effet de serre net d'ici 2050 au plus tard ". " Il est crucial de rediriger les flux financiers, à la fois publics et privés, vers l'action climatique ", avec " au moins 25 % des dépenses " du budget européen consacrées " à des projets destinés à lutter contre le changement climatique ", selon le texte.

Lire sur Les Décodeurs : la concentration de CO2 dans l'atmosphère a augmenté de 40 % en un siècle

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L'UE a réduit ses émissions de CO2 en 2018, mais en ordre dispersé

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La réduction globale de 2,5 % a été limitée par de fortes hausses de CO2 en Pologne et en Slovaquie. L'UE s'est engagée à réduire ses émissions de 20 % par rapport à leurs niveaux de 1990 en 2020.

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xkcd.com is best viewed with Netscape Navigator 4.0 or below on a Pentium 3±1 emulated in Javascript on an Apple IIGS at a screen resolution of 1024x1. Please enable your ad blockers, disable high-heat drying, and remove your device from Airplane Mode and set it to Boat Mode.

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xkcd.com is best viewed with Netscape Navigator 4.0 or below on a Pentium 3±1 emulated in Javascript on an Apple IIGS at a screen resolution of 1024x1. Please enable your ad blockers, disable high-heat drying, and remove your device from Airplane Mode and set it to Boat Mode.

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NASA finally found evidence of the universe's earliest molecule

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NASA used its Stratospheric Observatory for Infrared Astronomy (SOFIA) to detect the primordial molecule. The scientists found it in NGC 7027, a planetary nebula (a remnant of a Sun-like star) located 3,000 light-years away. The discovery proves that helium hydride can exist in space, and it confirms theories about the chemistry of the early universe and its evolution. The findings were published in Nature this week.

The discovery is also a testament to the power of NASA's latest technology. SOFIA is the world's largest airborne observatory. It's a modified Boeing 747SP jetliner, and it returns after every flight. That allows NASA to add new tools as they're available. A recent upgrade to SOFIA's German Receiver at Terahertz Frequencies (GREAT) instruments made this discovery possible. Scientists were able to tune to the frequency of the molecule and search for it in NGC 7027, where they've expected it could exist since the 1970s. As Harold Yorke, the director of the SOFIA Science Center, said in a press release, the molecule was lurking out there, we just needed the right instruments to find it.

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NASA finally found evidence of the universe's earliest molecule

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NASA used its Stratospheric Observatory for Infrared Astronomy (SOFIA) to detect the primordial molecule. The scientists found it in NGC 7027, a planetary nebula (a remnant of a Sun-like star) located 3,000 light-years away. The discovery proves that helium hydride can exist in space, and it confirms theories about the chemistry of the early universe and its evolution.

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Agression d'enseignante à Saint-Denis: «Il y a un désengagement de l'Etat»

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Ce jeudi, trois jeunes se sont introduits dans le collège Elsa-Triolet, en Saint-Denis ( Seine Saint-Denis). L'un d'eux a tiré avec un pistolet à billes en direction d'une enseignante en faisant croire à un attentat. Les employés du collège se sont mis en grève ce vendredi. Timothée, membre du personnel de l'établissement qui a préféré rester anonyme, a répondu à nos questions sur ce mouvement et ces revendications.

Qu'avez-vous mis en place après l'agression ?

Ce vendredi, nous avons fait une assemblée générale et voté à l'unanimité pour faire une grève pour la journée. Nous nous sommes rendus dans les collèges et les lycées de Saint-Denis pour rendre compte de la situation et faire un front commun avec l'ensemble des enseignants et des personnels de ces établissements pour dénoncer ce climat et demander plus de moyens et plus de personnels à l'Etat.

Ce genre d'agression est-il est fréquent dans les établissements de Saint-Denis ?

Non, c'est la première fois que l'on constate une telle intrusion dans ce collège. Ce jeudi, on a atteint une échelle de violence rare et exceptionnelle, mais s'il ne faut donc pas faire de généralités, elle témoigne d'une ambiance qui se dégrade dans la ville.

Qu'est-ce qui contribue à cette dégradation de l'ambiance selon vous ?

Nos personnels sont débordés. Nous comptons par exemple 2 CPE pour plus de 400 élèves. On ne demande pas une réponse sécuritaire, on veut faire de la prévention et mieux accompagner les individus, qu'il y ait plus de personnels mais aussi que les professeurs puissent organiser des demi-groupes ou des ateliers avec moins d'élèves.

On assiste aussi à une dégradation des services publics alentour, qui, comme nous, sont totalement saturés. Ce manque d'effectifs ne nous permet pas de remplir nos missions. C'est aussi pour eux que nous faisons cette grève, pas seulement pour nous donner des moyens à nous mais également à l'ensemble des services de Seine-Saint-Denis.

Justement, quelles sont vos revendications ?

Ce qu'on souhaite, c'est rompre avec cette fracture sociale. Qu'on nous écoute et surtout qu'on nous donne plus de moyens. On sait que les élèves sont les premières victimes, et c'est pour eux qu'on se bat. Si un élève veut voir un psy, il doit attendre des semaines, pareil pour un éducateur, etc.

La grève risque donc de continuer ?

Non car on sait que les grèves ne changent rien. Nous allons faire une nouvelle assemblée générale mardi soir pour réfléchir à différentes actions, notamment dans le cadre de la grève nationale contre la réforme Blanquer.

Justement, beaucoup de professeurs dénoncent cette réforme pour l'inégalité qu'elle renforcerait entre les territoires. C'est une de vos craintes ?

Oui, nous avons peur d'une rupture encore plus grande dans l'égalité des territoires. C'est aussi pour cela que je témoigne en anonyme, car la réforme ​ impose un droit de réserve. Mais ce que nous dénonçons en premier lieu, c'est le désengagement de l'Etat. On est le dernier service public qui fait encore barrage. Un élève ayant besoin d'une assistante scolaire mettra neuf mois à l'obtenir ici, contre un ou deux mois dans d'autres régions. Il y a une distorsion des chances, et les élèves se sentent abandonnés par l'institution, c'est pour ça que certains la défient ensuite comme ce jeudi. On ne peut pas demander à des élèves de croire aux valeurs de la République s'ils voient la République bafouer ses propres valeurs devant lui.

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"Il y a un désengagement de l'Etat à Saint-Denis"

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Ce jeudi, trois jeunes se sont introduits dans le collège Elsa-Triolet, en Saint-Denis ( Seine Saint-Denis). L'un d'eux a tiré avec un pistolet à billes en direction d'une enseignante en faisant croire à un attentat. Les employés du collège se sont mis en grève ce vendredi.

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Working together as a “virtual telescope,” observatories around the world produce first direct images of a black hole | MIT News

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An international team of over 200 astronomers, including scientists from MIT's Haystack Observatory, has captured the first direct images of a black hole. They accomplished this remarkable feat by coordinating the power of eight major radio observatories on four continents, to work together as a virtual, Earth-sized telescope.

In a series of papers published today in a special issue of Astrophysical Journal Letters, the team has revealed four images of the supermassive black hole at the heart of Messier 87, or M87, a galaxy within the Virgo galaxy cluster, 55 million light years from Earth.

All four images show a central dark region surrounded by a ring of light that appears lopsided - brighter on one side than the other.

Albert Einstein, in his theory of general relativity, predicted the existence of black holes, in the form of infinitely dense, compact regions in space, where gravity is so extreme that nothing, not even light, can escape from within. By definition, black holes are invisible. But if a black hole is surrounded by light-emitting material such as plasma, Einstein's equations predict that some of this material should create a "shadow," or an outline of the black hole and its boundary, also known as its event horizon.

Based on the new images of M87, the scientists believe they are seeing a black hole's shadow for the first time, in the form of the dark region at the center of each image.

Relativity predicts that the immense gravitational field will cause light to bend around the black hole, forming a bright ring around its silhouette, and will also cause the surrounding material to orbit around the object at close to light speed. The bright, lopsided ring in the new images offers visual confirmation of these effects: The material headed toward our vantage point as it rotates around appears brighter than the other side.

From these images, theorists and modelers on the team have determined that the black hole is about 6.5 billion times as massive as our sun. Slight differences between each of the four images suggest that material is zipping around the black hole at lightning speed.

"This black hole is much bigger than the orbit of Neptune, and Neptune takes 200 years to go around the sun," says Geoffrey Crew, a research scientist at Haystack Observatory. "With the M87 black hole being so massive, an orbiting planet would go around it within a week and be traveling at close to the speed of light."

"People tend to view the sky as something static, that things don't change in the heavens, or if they do, it's on timescales that are longer than a human lifetime," says Vincent Fish, a research scientist at Haystack Observatory. "But what we find for M87 is, at the very fine detail we have, objects change on the timescale of days. In the future, we can perhaps produce movies of these sources. Today we're seeing the starting frames."

"These remarkable new images of the M87 black hole prove that Einstein was right yet again," says Maria Zuber, MIT's vice president for research and the E.A. Griswold Professor of Geophysics in the Department of Earth, Atmospheric and Planetary Sciences. "The discovery was enabled by advances in digital systems at which Haystack engineers have long excelled."
"Nature was kind"
The images were taken by the Event Horizon Telescope, or EHT, a planet-scale array comprising eight radio telescopes, each in a remote, high-altitude environment, including the mountaintops of Hawaii, Spain's Sierra Nevada, the Chilean desert, and the Antarctic ice sheet.

On any given day, each telescope operates independently, observing astrophysical objects that emit faint radio waves. However, a black hole is infinitely smaller and darker than any other radio source in the sky. To see it clearly, astronomers need to use very short wavelengths - in this case, 1.3 millimeters - that can cut through the clouds of material between a black hole and the Earth.

Making a picture of a black hole also requires a magnification, or "angular resolution," equivalent to reading a text on a phone in New York from a sidewalk café in Paris. A telescope's angular resolution increases with the size of its receiving dish. However, even the largest radio telescopes on Earth are nowhere near big enough to see a black hole.

But when multiple radio telescopes, separated by very large distances, are synchronized and focused on a single source in the sky, they can operate as one very large radio dish, through a technique known as very long baseline interferometry, or VLBI. Their combined angular resolution as a result can be vastly improved.

For EHT, the eight participating telescopes summed up to a virtual radio dish as big as the Earth, with the ability to resolve an object down to 20 micro-arcseconds - about 3 million times sharper than 20/20 vision. By a happy coincidence, that's about the precision required to view a black hole, according to Einstein's equations.

"Nature was kind to us, and gave us something just big enough to see by using state-of-the-art equipment and techniques," says Crew, co-leader of the EHT correlation working group and the ALMA Observatory VLBI team.
"Gobs of data"
On April 5, 2017, the EHT began observing M87. After consulting numerous weather forecasts, astronomers identified four nights that would produce clear conditions for all eight observatories - a rare opportunity, during which they could work as one collective dish to observe the black hole.

In radio astronomy, telescopes detect radio waves, at frequencies that register incoming photons as a wave, with an amplitude and phase that's measured as a voltage. As they observed M87, every telescope took in streams of data in the form of voltages, represented as digital numbers.

"We're recording gobs of data - petabytes of data for each station," Crew says.

In total, each telescope took in about one petabyte of data, equal to 1 million gigabytes. Each station recorded this enormous influx that onto several Mark6 units - ultrafast data recorders that were originally developed at Haystack Observatory.

After the observing run ended, researchers at each station packed up the stack of hard drives and flew them via FedEx to Haystack Observatory, in Massachusetts, and Max Planck Institute for Radio Astronomy, in Germany. (Air transport was much faster than transmitting the data electronically.) At both locations, the data were played back into a highly specialized supercomputer called a correlator, which processed the data two streams at a time.

As each telescope occupies a different location on the EHT's virtual radio dish, it has a slightly different view of the object of interest - in this case, M87. The data received by two separate telescopes may encode a similar signal of the black hole but also contain noise that's specific to the respective telescopes.

The correlator lines up data from every possible pair of the EHT's eight telescopes. From these comparisons, it mathematically weeds out the noise and picks out the black hole's signal. High-precision atomic clocks installed at every telescope time-stamp incoming data, enabling analysts to match up data streams after the fact.

"Precisely lining up the data streams and accounting for all kinds of subtle perturbations to the timing is one of the things that Haystack specializes in," says Colin Lonsdale, Haystack director and vice chair of the EHT directing board.

Teams at both Haystack and Max Planck then began the painstaking process of "correlating" the data, identifying a range of problems at the different telescopes, fixing them, and rerunning the correlation, until the data could be rigorously verified. Only then were the data released to four separate teams around the world, each tasked with generating an image from the data using independent techniques.

"It was the second week of June, and I remember I didn't sleep the night before the data was released, to be sure I was prepared," says Kazunori Akiyama, co-leader of the EHT imaging group and a postdoc working at Haystack.

All four imaging teams previously tested their algorithms on other astrophysical objects, making sure that their techniques would produce an accurate visual representation of the radio data. When the files were released, Akiyama and his colleagues immediately ran the data through their respective algorithms. Importantly, each team did so independently of the others, to avoid any group bias in the results.

"The first image our group produced was slightly messy, but we saw this ring-like emission, and I was so excited at that moment," Akiyama remembers. "But simultaneously I was worried that maybe I was the only person getting that black hole image."

His concern was short-lived. Soon afterward all four teams met at the Black Hole Initiative at Harvard University to compare images, and found, with some relief, and much cheering and applause, that they all produced the same, lopsided, ring-like structure - the first direct images of a black hole.

"There have been ways to find signatures of black holes in astronomy, but this is the first time anyone's ever taken a picture of one," Crew says. "This is a watershed moment."
"A new era"
The idea for the EHT was conceived in the early 2000s by Sheperd Doeleman PhD '95, who was leading a pioneering VLBI program at Haystack Observatory and now directs the EHT project as an astronomer at the Harvard-Smithsonian Center for Astrophysics. At the time, Haystack engineers were developing the digital back-ends, recorders, and correlator that could process the enormous datastreams that an array of disparate telescopes would receive.

"The concept of imaging a black hole has been around for decades," Lonsdale says. "But it was really the development of modern digital systems that got people thinking about radio astronomy as a way of actually doing it. More telescopes on mountaintops were being built, and the realization gradually came along that, hey, [imaging a black hole] isn't absolutely crazy."

In 2007, Doeleman's team put the EHT concept to the test, installing Haystack's recorders on three widely scattered radio telescopes and aiming them together at Sagittarius A*, the black hole at the center of our own galaxy.

"We didn't have enough dishes to make an image," recalls Fish, co-leader of the EHT science operations working group. "But we could see there was something there that's about the right size."

Today, the EHT has grown to an array of 11 observatories: ALMA, APEX, the Greenland Telescope, the IRAM 30-meter Telescope, the IRAM NOEMA Observatory, the Kitt Peak Telescope, the James Clerk Maxwell Telescope, the Large Millimeter Telescope Alfonso Serrano, the Submillimeter Array, the Submillimeter Telescope, and the South Pole Telescope. (Read further in the related press release.)

Coordinating observations and analysis has involved over 200 scientists from around the world who make up the EHT collaboration, with 13 main institutions, including Haystack Observatory. Key funding was provided by the National Science Foundation, the European Research Council, and funding agencies in East Asia, including the Japan Society for the Promotion of Science. The telescopes contributing to this result were ALMA, APEX, the IRAM 30-meter telescope, the James Clerk Maxwell Telescope, the Large Millimeter Telescope Alfonso Serrano, the Submillimeter Array, the Submillimeter Telescope, and the South Pole Telescope.

More observatories are scheduled to join the EHT array, to sharpen the image of M87 as well as attempt to see through the dense material that lies between Earth and the center of our own galaxy, to the heart of Sagittarius A*.

"We've demonstrated that the EHT is the observatory to see a black hole on an event horizon scale," Akiyama says. "This is the dawn of a new era of black hole astrophysics."

The Haystack EHT team includes John Barrett, Roger Cappallo, Joseph Crowley, Mark Derome, Kevin Dudevoir, Michael Hecht, Lynn Matthews, Kotaro Moriyama, Michael Poirier, Alan Rogers, Chester Ruszczyk, Jason SooHoo, Don Sousa, Michael Titus, and Alan Whitney. Additional contributors were MIT alumni Daniel Palumbo, Katie Bouman, Lindy Blackburn, Sera Markoff, and Bill Freeman, a professor in MIT's Department of Electrical Engineering and Computer Science.

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Working together as a "virtual telescope," observatories around the world produce first direct images of a black hole

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An international team of over 200 astronomers, including scientists from MIT's Haystack Observatory, has captured the first direct images of a black hole. They accomplished this remarkable feat by coordinating the power of eight major radio observatories on four continents, to work together as a virtual, Earth-sized telescope.

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You're probably not allergic to vaccines | EurekAlert! Science News

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You're probably not allergic to vaccines

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Five facts about allergies to vaccines, pulled together by two McMaster University physicians.

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Manmade or natural, tasty or toxic, they're all chemicals … | Dr Mark Lorch | Science | The Guardian

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Chemicals are bad, right? Otherwise why would so many purveyors of all things healthy proudly proclaim their products to be "chemical-free" and why would phrases such as "it's chock full of chemicals" be so commonly used to imply something is unnatural and therefore inherently dangerous?

On one level these phrases are meaningless - after all, chemicals are everywhere, in everything. From the air that we breathe to the pills we pop, it's all chemicals. Conversely, many would argue (the Advertising Standards Agency included) that we all know perfectly well what "chemical-free" means and those who rail against the absurdity of the phrase are just being pedantic. Even the Oxford Dictionary defines a chemical as "a distinct compound or substance, especially one which has been artificially prepared or purified."

So "chemical-free" products are adhering to a recognised usage.

But pedantry and definition aren't really the point. The point is that every time anti-chemical slogans are used people are being misinformed. The implication is always that the terms "chemical" and "poison" are interchangeable. This is a perception that permeates our subconscious to the extent that chemists themselves have been guilty of exactly the same lazy language.

As a result of this common usage of "chemicals" the whole subject has been tainted with unpleasant connotations. And while physics and biology have their celebrity scientists extolling the wonders of bosons, bugs and big bangs, chemists are left floundering in their wake or are left completely unrepresented in the mainstream media ( where's the Guardian's chemistry blog?).

This is all despite the modern world having been built on the innovations of chemists. For example, most of the world's population is sustained by the innovations of one of them. Fritz Haber invented a means to turn the nitrogen in the air into useful agricultural fertiliser (40% of the nitrogen in you comes from Haber's reaction). Meanwhile the chemists who artificially prepared or purified antibiotics are responsible for a treatment that saves more lives than any other medical intervention.

All these arguments are trotted out by chemistry bloggers on a regular basis, but these writers are only preaching to the converted. The good news is that on Monday the campaign group Sense about Science joined the discussion with the publication of a guide entitled Making Sense of Chemical Stories. Sense about Science is a respected charitable organisation that "equips people to make sense of scientific and medical claims in public discussion". In short, it facilitates discussions between concerned/interested groups and relevant experts.

'A common misconception is that all manmade chemicals are harmful, and all natural chemicals are good for us. However, many natural chemicals are just as harmful to human health, if not more so.' Photograph: Compound Interest/Sense About Science Photograph: Compound Interest/Sense About Science

The aim of its guide is to bridge the disconnect between the lifestyle view (and popular definition) of chemicals and the realities of how chemistry is used to sustain the modern world. The guide does this by tackling common misconceptions about chemistry.

A key misconception is that natural chemicals are somehow safer than manmade ones. The wrongheadedness of this is nicely illustrated by a pair of infographics (above) created by Compound Interest that don't shy away from admitting synthetic chemicals are often toxic, but also make it clear that whether a chemical is naturally occurring or manmade tells us precisely nothing about its toxicity.

Not only that, but where harmful chemicals do occur (be that in potatoes or lethal injections) the dose is the really important thing to consider.

Making Sense of Chemical Stories is being promoted to the public, journalists, lifestyle press and policymakers. It, along with the infographics, are freely available to download from Sense about Science, or if you prefer a hard copy (or a box full of them) email enquiries@senseaboutscience.org or call 020 7490 9590 with your contact details.

Order some and spread the word: chemicals are good for you!

Mark Lorch is a senior lecturer in chemistry at the University of Hull. He blogs at www.chemistry-blog.com and tweets as @sci_ents

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Manmade or natural, tasty or toxic, they're all chemicals ... | Dr Mark Lorch

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Chemicals are bad, right? Otherwise why would so many purveyors of all things healthy proudly proclaim their products to be "chemical-free" and why would phrases such as "it's chock full of chemicals" be so commonly used to imply something is unnatural and therefore inherently dangerous?

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Examples of chemicals considered to meet (or not meet) the definition of a naturally-occurring chemical.

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© 2019 Campaign for Safe Cosmetics, a project of Breast Cancer Prevention Partners all rights reserved. Site by Rootid.com

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Natural vs. Man-Made Chemicals – Dispelling Misconceptions | Compound Interest

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The term 'chemophobia' has been used on social media amongst chemists with increasing regularity over the past year. Defined as 'a fear of chemicals', more specifically it refers to the growing tendency for the public to be suspicious and critical of the presence of any man-made (synthetic) chemicals in foods or products that they make use of. Sense About Science, a UK-based charitable trust whose mission is 'to equip people to make sense of science and evidence', is attempting to combat this with a new free guide, "Making Sense of Chemical Stories", for which the graphics in this post were made.

In these graphics, I wanted to emphasise the point that whether a chemical is natural or man-made tells us nothing about its toxicity. There are many chemical compounds, found naturally in plants, that are poisonous to humans in small amounts; similarly, there are many man-made compounds which are perfectly harmless unless ingested at very high doses. Although the first of the two graphics sorts natural and man-made chemicals into toxic & non-toxic categories, overall I wanted to show that in reality, this is an impossibility - all chemicals, if taken in a high enough dose, are toxic - even water, which we consider essential to life. "The dose makes the poison" is a rule that applies to all compounds, natural or man-made.

A common argument is that we've become accustomed to, and built up tolerance to, naturally-occurring toxic compounds, whereas we haven't had time to do so with more recent synthetic compounds. However, consider that the most toxic chemical compound known to man is the naturally-occurring botulinum, one teaspoon of which could kill a quarter of the world's population. It's been around for millennia - and yet we still haven't developed resistance to it. Plants, too, are constantly evolving, and producing compounds we've never before been exposed to; however, not every new compound produced by a plant is deadly to us just because we've never been exposed to it before.

The second of the graphics further emphasises the relationship between dose and toxicity. Many fruits and vegetables contain compounds that have been shown to be toxic to humans. However, they are present in such comparatively minute quantities, that they are nowhere near the dose required for them to cause harmful effects.

In recent years, some groups have been in uproar over the presence of chemicals that are known to be harmful or carcinogenic in everyday cosmetics or foods. As an example, some groups maligned the presence of formaldehyde in some vaccines - despite the fact that there's more formaldehyde present in your average pear (for the record, the quantity in both is well below the dose needed to cause any harm). The key fact that is often overlooked about chemical testing is that it often involves concentrations of chemicals well above those that we are normally exposed to. Just because a chemical is harmful or carcinogenic at very high doses, does not necessarily mean it will have any ill effects at the doses we experience. Food regulation exists to prevent harmful levels of chemicals from being used in products we buy - if the levels were harmful, they simply wouldn't be allowed on the shelves.

Another prime example of the spread of chemical misinformation is the self-styled 'Food Babe's' poorly informed attack on the use of azodicarbonamide (unceremoniously dubbed 'the Yoga Mat chemical') in Subway's bread, which is excellently debunked here. It's a sad state of affairs when someone without a chemistry or food science degree, and with little more than a simple knowledge of the subject, is able to spread such misinformation about chemicals much more easily than those who wish to educate the public to better evaluate such stories for themselves.

That's why I was eager to get involved and support Sense About Science's initiative in creating these graphics for their new guide. Whilst, as ever with this kind of information, it's unlikely to reach those in need of it most, it will hopefully encourage those who do read it to more neutrally evaluate claims about chemicals in their food and personal care products, and to discard their pre-conceived notions about natural and man-made chemicals.

You can view and download the Sense About Science guide on their site here, where you can also download the graphics in this post, or request hard copies. Additionally, I've been inspired by the guide to create a few other graphics, unaffiliated with Sense About Science, which I'll be sharing over the next week or so. Please share their guide far and wide, and help stem the flow of chemical misinformation!

EDIT (07/06/2014): I've altered the graphic to remove MSG from from the synthetic section, and replace it with propylene glycol. MSG was included as it was commonly synthetically produced for use as a food additive. However, having been informed that it's now more commonly produced from bacteria, it doesn't fit in the man-made section, so I've altered the graphic to reflect this.

The graphic in this article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. See the site's content usage guidelines.

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Natural vs. Man-Made Chemicals - Dispelling Misconceptions

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The term 'chemophobia' has been used on social media amongst chemists with increasing regularity over the past year.

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Natural vs. Chemical – Which Is Better? – Lab Muffin Beauty Science