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24 minute video about a spacecrafts mission to a comet

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24 minute video about a spacecrafts mission to a comet

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The amazing adventures of Rosetta and Philae

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It's all about Earth's tilt!

Many people believe that Earth is closer to the Sun in the summer and that is why it is hotter. And, likewise, they think Earth is farthest from the Sun in the winter.

Although this idea makes sense, it is incorrect.

It is true that Earth's orbit is not a perfect circle. It is a bit lop-sided. During part of the year, Earth is closer to the Sun than at other times. However, in the Northern Hemisphere, we are having winter when Earth is closest to the Sun and summer when it is farthest away! Compared with how far away the Sun is, this change in Earth's distance throughout the year does not make much difference to our weather.

There is a different reason for Earth's seasons.

Earth's axis is an imaginary pole going right through the center of Earth from "top" to "bottom." Earth spins around this pole, making one complete turn each day. That is why we have day and night, and why every part of Earth's surface gets some of each.

Earth has seasons because its axis doesn't stand up straight.

But what caused Earth to tilt?

Long, long ago, when Earth was young, it is thought that something big hit Earth and knocked it off-kilter. So instead of rotating with its axis straight up and down, it leans over a bit.

By the way, that big thing that hit Earth is called Theia. It also blasted a big hole in the surface. That big hit sent a huge amount of dust and rubble into orbit. Most scientists think that that rubble, in time, became our Moon.

As Earth orbits the Sun, its tilted axis always points in the same direction. So, throughout the year, different parts of Earth get the Sun's direct rays.

Sometimes it is the North Pole tilting toward the Sun (around June) and sometimes it is the South Pole tilting toward the Sun (around December).

It is summer in June in the Northern Hemisphere because the Sun's rays hit that part of Earth more directly than at any other time of the year. It is winter in December in the Northern Hemisphere, because that is when it is the South Pole's turn to be tilted toward the Sun.

Earth's lopsided orbit

Earth's perihelion (point closest to Sun) = 91,400,000 miles from Sun

Earth's aphelion (point farthest from Sun) = 94,500,000 miles from Sun

While that is a difference of over 3 million miles, relative to the entire distance, it isn't much.

And, believe it or not, aphelion (when Earth is farthest from the Sun) occurs in July, and perihelion (when we are closest) occurs in January. For those of us who live in the Northern Hemisphere where it's summer in July and winter in January, that seems backwards, doesn't it? That just goes to prove that Earth's distance from the Sun is not the cause of the seasons.

Related Resources for Educators

Seasons (Educator Guide to go with Seasons Spotlite video)
Seasons (Nearpod Lesson to go with Seasons Spotlite video)
Our World: Sun's Position
Sun's Position (Educator Guide to go with Sun's Position Spotlite video)
Sun's Position (Nearpod Lesson to go with Sun's Position Spotlite video)

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This lists the logos of programs or partners of NG Education which have provided or contributed the content on this page. Program

1. Review planet order and relative sizes in our solar system.
Display the NASA illustration: All Planet Sizes. Ask students to point out the location of Earth. Then challenge them to identify all of the planets, outward from the sun (left to right): inner planets Mercury, Venus, Earth, Mars; outer planets Jupiter, Saturn, Uranus, Neptune, and Pluto. Remind students that Pluto is no longer considered a planet in our solar system; it was downgraded to the status of dwarf planet in 2006. Point out the locations of the asteroid belt (between Mars and Jupiter) and Kuiper belt (past Pluto) if they were included in this illustration. Explain to students that the illustration shows the planets in relative size. Ask: What do you think relative size means? Elicit from students that the pictures show how big the planets are when compared to each other and to the sun. Ask: Which planet is the smallest? (Mercury) Which is the largest? (Jupiter)

2. Have students gather data and compare planet sizes.
Divide students into small groups. Distribute one copy of the worksheet Planetary Size Comparison to each group. Have groups use the Planet Size Comparison interactive to find and record data on planet diameters and ratios. Ask:

What do you notice about the size of the planets? (Possible response: The inner, rocky planets are smaller than the outer, gaseous planets.)

How do you think the sizes of the planets compare? (Possible response: There is a big difference in the sizes of the planets. Some are fairly small and others are extremely large.)

Would it be easy to model the planet sizes? Why or why not? (Possible response: No, because of the great differences in size.)

How could we model differences? What everyday objects could represent planets and the sun? (Possible responses: peas/beach ball; grains of sand/orange)

Have students discuss the answers in their small groups. Then regroup as a class to discuss students' ideas.

3. Build background about the astronomical unit (AU).
Explain to students that an astronomical unit, or AU, is a simplified number used to describe a planet's distance from the sun. It is a unit of length equal to the average distance from Earth to sun, approximately 149,600,000 kilometers (92,957,000 miles). Only Earth can be assigned AU 1. Planets farther away would have AU greater than 1; planets closer would have AU less than 1. Ask: Why do you think scientists find it helpful to use astronomical units? (Possible response: Distances in the solar system are very large. Using AU helps keep the numbers manageable, or smaller, so we can easily calculate very large distances.) What are the challenges of using kilometers or miles instead? (Possible response: Using kilometers or miles would make calculations more difficult and could produce errors in measurements required to accurately send a probe or lander to another planet.) Explain to students that the astronomical unit provides a way to express and relate distances of objects in the solar system and to carry out astronomical calculations. For example, stating that the planet Jupiter is 5.2 AU (5.2 Earth distances) from the sun and that Pluto is nearly 40 AU allows you to more easily compare the distances of all three bodies.

4. Introduce the modeling activity.
Tell students that they are going to stand in for the planets and planetary objects in order to create a model of relative planetary sizes and relative distances. Display the NASA illustration: How Big is the Sun? to give students a sense of the relative sizes of planets compared to an everyday object like a basketball. Make sure students understand that the distances between the planets are very large compared to the sizes of each planet. This makes it extremely difficult to create an exact scale of our solar system, so this activity will focus on the distance comparison.

5. Have groups create models of relative planetary distances.
Divide students into groups of 9, 10 or 11, depending on class size. (If 9, one student represents the sun and the remaining students represent 8 planets; If 10, the sun, planets, and asteroid belt; If 11, the sun, planets, asteroid belt, and Kuiper Belts) Take students to a large area, such as the gymnasium or empty parking lot. You'll need enough space for each group to spread out and create their model, using the following scale, with each step equaling approximately 1 meter (about 3.28 feet):

Sun: stands at the edge of the area

Mercury = 1 step from sun

Venus = 2 steps from sun

Earth = 2.5 steps from sun

Mars = 4 steps from sun

Asteroid belt = 8 steps from sun

Jupiter = 13 steps from sun

Saturn = 24 steps from sun

Uranus = 49 steps from sun

Neptune = 76 steps from sun

Kuiper belt = 100 steps from sun

Emphasize that at this scale, the sun would be less than 1.3 centimeters (0.5 inches) in diameter. Ask students to describe what they notice about planetary distances from the model. If needed, allow one student from each group to put an object in their place and walk around their group's model to make observations.

6. Have students make a math connection.
Distribute copies of the worksheet Stepping Out the Solar System to each group. Have students recalculate the number of paces for each planet's orbit, as constrained by the size of the available area. Use the provided answer key to check groups' work. Then have students recreate the model.

Informal Assessment

Have students work independently to summarize, in writing, what they learned about our solar system, including:

locations of planets in relation to the sun and one another

relative sizes of planets, including Earth

relative distances of planets

any conclusions they can draw about the locations of the asteroid belt and Kuiper belt

Extending the Learning

Encourage students to practice backyard astronomy. At certain times of day and year, it's possible to view planets Mercury, Venus, Mars, Jupiter, and Saturn with the naked eye. Students can use Sky and Telescope Magazine's Sky at a Glance feature to find out what planets are visible in the night sky and where to look. Ask students to report back to the class with what they observed.

Background Information

Vocabulary

Video

Websites

Credits

Media Credits

The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited.

Writer

Anna Mika, M.S. Ed., NASA Network of Educator Astronaut Teachers (NEAT)

Editor

Christina Riska Simmons

Educator Reviewers

Dianne Koval Butler, Manager, Education Outreach & Partnerships, Lockheed Martin Corporate Communications
Jeanne Wallace-Weaver, Educational Consultant

Expert Reviewer

Buddy Nelson, Media Relations, Lockheed Martin Space Systems

National Geographic Program

Wildest Weather in the Solar System

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Christina Riska Simmons

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This lists the logos of programs or partners of NG Education which have provided or contributed the content on this page. Program 1. Review planet order and relative sizes in our solar system. Display the NASA illustration: All Planet Sizes. Ask students to point out the location of Earth.

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The energy debate: Renewable energy cannot replace fossil fuels - DevelopmentEducation.ie

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Currently, we are (over)dependent on fossil fuels to heat our homes, run our cars, power our offices, industry and manufacturing, and respond to our insatiable desire to power all of our electrical goods

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Junior Cycle students

Energy in Action is a collection of online activities and ideas. We designed it to support the teaching and learning of energy and sustainability in the Junior Cycle. It is suitable for students of Science, CSPE, Geography and Home Economics.

An inquiry approach to energy and sustainability

These resources have been developed for use with an inquiry approach to education. They aim to enhance students' scientific knowledge, skills and competencies. The focus is on providing students with opportunities to consider and tackle problems that the future holds, e.g. sustainable practices in schools, homes and beyond.

A range of topics linked to our daily lives

It will develop young peoples' knowledge across a range of topics such as, energy sources, efficiency, conservation, climate change and global warming. These concepts will then be linked to students' daily lives.

Programme development

The programme was developed by the SEAI in collaboration with Junior Cycle teachers and CASTeL at Dublin City University.

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Energy in Action is a collection of online activities and ideas. We designed it to support the teaching and learning of energy and sustainability in the Junior Cycle. It is suitable for students of Science, CSPE, Geography and Home Economics. These resources have been developed for use with an inquiry approach to education.

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On February 7th 2020, ESA's Solar Orbiter will be launching to the sun with the help of several Irish connections. To celebrate this exciting mission, ESERO Ireland are offering two schools the opportunity to speak to Dr Niamh Shaw, live from the European Space Operations Centre at Darmstadt. Find out how to win here!

ESERO is an education project of the European Space Agency (ESA), co-funded by ESA and by national partners active in the fields of education and space. In Ireland, the national partner is Science Foundation Ireland.

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Home | ESERO | European Space Education Resource Office

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On February 7th 2020, ESA's Solar Orbiter will be launching to the sun with the help of several Irish connections. To celebrate this exciting mission, ESERO Ireland are offering two schools the opportunity to speak to Dr Niamh Shaw, live from the European Space Operations Centre at Darmstadt.

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Interactive sky chart (now with PDF print option)

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Satellite predictions and other astronomical data customised for your location.

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INSIDE SATURN

ATMOSPHERE AND PLANETARY COMPOSITION
Saturn is about 97% Hydrogen gas, about 3% helium gas and about 0.05% methane, plus ammonia. Near the equator, tremendous winds blow at 1,100 mph (500 meters per second) toward the east. The clouds in the atmosphere are cold, thick and uniform in shape.

Saturn is a gaseous planet with a rocky core, a liquid metallic hydrogen layer above the core, and a molecular hydrogen layer above that. The hot, heavy, rocky core has a radius possibly three times the radius of theEarth.

Saturn has a strong magnetic field (less thanJupiter's, but still very strong). Saturn's magnetic field is probably generated by electrical current in conductive layers near the quickly-rotating planet's core. Because of this strong magnetic field, there are abundant auroras on Saturn and radios emissions from it.

Saturn radiates 79% more energy than it receives from theSun, probably heat from its hot core.

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The Universe is expanding, and it is mysterious dark energy that is driving this expansion. While Einstein asserted that nothing can travel faster than the speed of light, it is only the motion of objects that his law constrains, not the space that the objects actually occupy. Yes, the space between our galaxy and another distant galaxy can stretch and expand at a rate so tremendous that the distant galaxy may recede even faster than the speed of light.

However, if the galaxy recedes away from us faster than the speed of light, shouldn't the light it emits never reach us? To us, such an unobservable galaxy is as good as being nonexistent. Considering the seemingly infinite size of the Universe and the time for which it has existed, billions and billions of galaxies are beyond our reach. Should astronomers then surrender their telescopes and abort their quest?

Hubble Constant

While the nature of dark energy still eludes us, we know the rate at which it stretches space. However, what's astounding is that the rate of expansion isn't constant; the expansion is accelerating, that is, the more distant a galaxy, the faster it is receding. The rate of recession was determined to be 71 km/s for two galaxies separated by a megaparsec. This is Hubble's constant. A parsec is a unit of length used to measure astronomical distances. One parsec is equal to about 3.26 light years (the distance light travels in one year), and a megaparsec is a million parsecs or 3.086×1019 km.

Since the expansion is accelerating at this rate, two galaxies separated by 2 megaparsecs are receding at 142 km/s, and galaxies separated by 4 megaparsecs, at 284 km/s! The speed of light is a stupendous 300 million m/s or 300,000 km/s. It is quite easy to compute the distance by which two galaxies must be separated such that they recede away from each other at 300,000 km/s - approximately 4225 megaparsecs. (Bear in mind that the distance is an approximation, as the speed of light is slightly less than 3,00,000 km/s.)

It is no surprise that billions and billions of galaxies therefore seem beyond our reach; 4225 megaparsecs is merely a speck, perhaps something microscopic, on the massive canvas that is the Universe. The diameter of the observable Universe is estimated to be about 28 billion parsecs. Yet the Hubble telescope, while surveying absolute nothingness, managed to capture this (below) - it had peered far across the ocean, even beyond the horizon... way beyond the horizon.

The objects glinting deeper within the image are galaxies and cluster of galaxies that bloomed to life when the Universe was just an adolescent. The image in its entirety is a photo album that catalogues the Universe's epic life. What you're witnessing is the Universe's past, and it is only in this regard that the galaxies now farther than 4225 parsecs can be observed. We can only observe their past, not their present, because the light they emitted then has reached us now. Today, they might as well be extinguished and deceased. However, we will only find out after the light emitted by their last stars reaches us, that is, billions of years later. Unless it's too late.

The Race with Time

Light emitted by a receding star towards you is like a rolled carpet unspooling from a car receding away from you. The carpet's end reaches your feet if its rate of unspooling is faster than the rate at which the car is receding. However, the recession stretches the length of the carpet; the light we receive has experienced a red- shift. Its wavelength, as the galaxy recedes farther and farther, is stretched or elongated towards red, then infrared, then microwaves and finally radio waves.

Inversely, when a star approaches the observer, the light it emits experiences a blue-shift; its wavelength shortens towards blue, then ultraviolet and so on. The wavelength obeys the Doppler effect: the same effect that causes sirens to sound louder as they approach and dimmer as they recede. It was this observation of red- and blue-shifting that made the astronomer Edward Hubble realize and declare, to Einstein's despair, that the Universe is expanding. The constant is named after him for this revolutionary discovery.

Now, with Earth as the center, let's draw on the spherical map of the Universe, a sphere with a radius of 4225 parsecs. Let's call it the Hubble Sphere. Within this sphere are galaxies that are not receding away faster than the speed of light. Let's call them NFSL galaxies. Beyond this sphere are galaxies that are receding away faster than the speed of light. These are the FSL galaxies.

Remember that the Universe is continually expanding, which means that a long time ago, FSL galaxies inhabited the Hubble Sphere and actually were NFSL galaxies. Therefore, the light they emitted when they inhabited the sphere will reach us because, in the sphere, the light travels faster than the rate at which the galaxies recede, but it limns them as they were then. This light is stretched, of course, but we do receive it.

Today, even though they have traversed the sphere, the car now recedes faster than the carpet unspools. What ensues is a grievous tussle: the light is now increasingly and tremendously stretched, but if the galaxy isn't too far, strenuously, the light will eventually be able to enter the sphere and therefore outpace the stretching of space to reach us. However, this would take billions of years, and therefore, yet again, the light would become a lens into then. The Cosmic Microwave Background Radiation (CMBR) is a map of variegated colors dispersed during the Big Bang itself. It is the oldest light that has ever illuminated humankind! However, it is so old and deep that it is stretched to the level of microwaves. It is located, in fact, way beyond the sphere.

However, as the expansion is accelerated, as the more distant a galaxy, the faster it recedes, the light it emits is further stretched. Eventually, it gets to the extent that it never reaches us or is stretched apart even beyond radio waves, thereby becoming too faint to be perceived. Such a galaxy has receded so far and continues to do so so rapidly that the light it emits never reaches us. It is truly unobservable.

Realize that we can only glimpse the past, and never the present, until eons from now, when the galaxies have receded too far, and it will be too late even for that. Astronomers eons from now would be unable to locate neighboring galaxies and the CMBR, and therefore the Big Bang, the supposed origin of our cosmos.

Astronomers and cosmologists assert that we live in the golden era of cosmology, a time when the galaxies aren't too close and nascent, nor are they too old and far away. If we must begin our quest for the truths of the Universe, now is the time, because eons from now, we will discover that the shores across the horizon are long faded and lost - leaving our tiny, remote island as a stone in an ocean of dark, empty space.

Reference

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Do Galaxies Receding Faster Than The Speed Of Light Disappear From Our Observations?

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The Universe is expanding, and it is mysterious dark energy that is driving this expansion. While Einstein asserted that nothing can travel faster than the speed of light, it is only the motion of objects that his law constrains, not the space that the objects actually occupy.

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LPI Education and Public Engagement collaborates with its partners to make current Earth and planetary science content available to all audiences.

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The danse of the terrestrian planets (heliocentric and geocentric)

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The danse of the terrestrian planets (heliocentric and geocentric)