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The surprising science of happiness | Dan Gilbert

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Louie Schwartzberg: Hidden miracles of the natural world

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We live in a world of unseeable beauty, so subtle and delicate that it is imperceptible to the human eye. To bring this invisible world to light, filmmaker Louie Schwartzberg bends the boundaries of time and space with high-speed cameras, time lapses and microscopes.

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Swiss artist and photographer Fabian Oefner is on a mission to make eye-catching art from everyday science. In this charming talk, he shows off some recent psychedelic images, including photographs of crystals as they interact with soundwaves. And, in a live demo, he shows what really happens when you mix paint with magnetic liquid--or when you set fire to whiskey.

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Scientists slow down the speed of light travelling in free space

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Scientists slow down the speed of light travelling in free space

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Scientists have long known that the speed of light can be slowed slightly as it travels through materials such as water or glass.

However, it has generally been thought impossible for particles of light, known as photons, to be slowed as they travel through free space, unimpeded by interactions with any materials.

In a new paper published in Science Express today (Friday 23 January), researchers from the University of Glasgow and Heriot-Watt University describe how they have managed to slow photons in free space for the first time. They have demonstrated that applying a mask to an optical beam to give photons a spatial structure can reduce their speed.

The team compare a beam of light, containing many photons, to a team of cyclists who share the work by taking it in turns to cycle at the front. Although the group travels along the road as a unit, the speed of individual cyclists can vary as they swap position.

The group formation can make it difficult to define a single velocity for all cyclists, and the same applies to light. A single pulse of light contains many photons, and scientists know that light pulses are characterised by a number of different velocities.

The team's experiment was configured like a time trial race, with two photons released simultaneously across identical distances towards a defined finish line. The researchers found that one photon reached the finish line as predicted, but the structured photon which had been reshaped by the mask arrived later, meaning it was travelling more slowly in free space. Over a distance of one metre, the team measured a slowing of up to 20 wavelengths, many times greater than the measurement precision.

The work demonstrates that, after passing the light beam through a mask, photons move more slowly through space. Crucially, this is very different to the slowing effect of passing light through a medium such as glass or water, where the light is only slowed during the time it is passing through the material -- it returns to the speed of light after it comes out the other side. The effect of passing the light through the mask is to limit the top speed at which the photons can travel.

The work was carried out by a team from the University of Glasgow's Optics Group, led by Professor Miles Padgett, working with theoretical physicists led by Stephen Barnett, and in partnership with Daniele Faccio from Heriot-Watt University.

Daniel Giovannini, one of the lead authors of the paper, said: "The delay we've introduced to the structured beam is small, measured at several micrometres over a propagation distance of one metre, but it is significant. We've measured similar effects in two different types of beams known as Bessel beams and Gaussian beams."

Co-lead author Jacquiline Romero said: "We've achieved this slowing effect with some subtle but widely-known optical principles. This finding shows unambiguously that the propagation of light can be slowed below the commonly accepted figure of 299,792,458 metres per second, even when travelling in air or vacuum.

"Although we measure the effect for a single photon, it applies to bright light beams too. The effect is biggest when the lenses used to create the beam are large and when the distance over which the light is focused is small, meaning the effect only applies at short range."

Professor Padgett added: "It might seem surprising that light can be made to travel more slowly like this, but the effect has a solid theoretical foundation and we're confident that our observations are correct.

"The results give us a new way to think about the properties of light and we're keen to continue exploring the potential of this discovery in future applications. We expect that the effect will be applicable to any wave theory, so a similar slowing could well be created in sound waves, for example."

The team's paper, titled 'Spatially Structured Photons that Travel in Free Space Slower than the Speed of Light', is published in Science Express, which provides electronic publication of selected papers in advance of print in the journal Science.

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optics; graphene; chemistry; inorganic chemistry; spintronics; solar energy; nature of water; quantum physics

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Scientists slow down the speed of light travelling in free space

# data[].attributes.attachment_link.description
Scientists have long known that the speed of light can be slowed slightly as it travels through materials such as water or glass. However, it has generally been thought impossible for particles of light, known as photons, to be slowed as they travel through free space, unimpeded by interactions with any materials.

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Awareness of thinking; awareness of dreaming

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Awareness of thinking; awareness of dreaming

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To control one's dreams and to live 'out there' what is impossible in real life -- a truly tempting idea. Some persons -- so-called lucid dreamers -- can do this. Researchers from the Max Planck Institute for Human Development in Berlin and the Max Planck Institute of Psychiatry in Munich have discovered that the brain area which enables self-reflection is larger in lucid dreamers. Thus, lucid dreamers are possibly also more self-reflecting when being awake.

Lucid dreamers are aware of dreaming while dreaming. Sometimes, they can even play an active role in their dreams. Most of them, however, have this experience only several times a year and just very few almost every night. Internet forums and blogs are full of instructions and tips on lucid dreaming. Possibly, lucid dreaming is closely related to the human capability of self-reflection -- the so-called metacognition.

Neuroscientists from the Max Planck Institute for Human Development and the Max Planck Institute of Psychiatry have compared brain structures of frequent lucid dreamers and participants who never or only rarely have lucid dreams. Accordingly, the anterior prefrontal cortex, i.e., the brain area controlling conscious cognitive processes and playing an important role in the capability of self-reflection, is larger in lucid dreamers.

The differences in volumes in the anterior prefrontal cortex between lucid dreamers and non-lucid dreamers suggest that lucid dreaming and metacognition are indeed closely connected. This theory is supported by brain images taken when test persons were solving metacognitive tests while being awake. Those images show that the brain activity in the prefrontal cortex was higher in lucid dreamers. "Our results indicate that self-reflection in everyday life is more pronounced in persons who can easily control their dreams," states Elisa Filevich, post-doc in the Center for Lifespan Psychology at the Max Planck Institute for Human Development.

The researchers further want to know whether metacognitive skills can be trained. In a follow-up study, they intend to train volunteers in lucid dreaming to examine whether this improves the capability of self-reflection.

Journal Reference:

Filevich, E., Dresler, M., Brick, T.R., Kühn, S. Metacognitive Mechanisms Underlying Lucid Dreaming. The Journal of Neuroscience, 2015 DOI: 10.1523/JNEUROSCI.3342-14.201

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# data[].attributes.attachment_link.title
Lucid dreams and metacognition: Awareness of thinking; awareness of dreaming

# data[].attributes.attachment_link.description
To control one's dreams and to live 'out there' what is impossible in real life -- a truly tempting idea. Some persons -- so-called lucid dreamers -- can do this. Researchers have discovered that the brain area which enables self-reflection is larger in lucid dreamers.