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The Trip Around the Sun - period of revolution, tilt of axis, orbit
The Trip Around the Sun
period of revolution, tilt of axis, orbit
Astronomy Unit
Want to feel like the Earth for a day? Want to understand why we have nights and days and why we have
seasons? You do? Great! All you will need is an empty room, a lamp sitting on a table in the middle of
the floor, and a strong stomach. If you do not have all of these things, you can use other things, or use
your brain. I know you have a great brain. Why do you need a strong stomach for this? Well, the Earth
spins as it spins around the sun. So this is going to need more than one kind of spinning on your part.
Take it slow.
Set up the lamp in the middle of the room (or your mind). Got it? Great. This is the sun. Your head is the
Earth. Now, walk in an oval around it very slowly. To orbit means for one thing to move around another
thing. We usually use the word orbit to talk about planets moving around a star, such as the Earth moving
around the sun. Or in this case, you walking around a lamp. If anyone asks what you are doing, tell them,
"I am charting the Earth's orbit around our sun!" They will probably leave you alone.
Why do you have to walk so slowly? Space is a very big place, and it takes the Earth a long time to orbit
around the sun. 365 days, in fact. A period of revolution is how long it takes a planet to move around a
star. It is equal to one year. Every planet takes a different amount of time to orbit around the sun. Some
take more time than Earth, some take less. It depends on how far away they are from the sun. Now spin
in small circles while still walking around the lamp. Watch as the light goes in and out of your eyes. Way
to go! You have just made nights and days on your Earth head!
Now you are going to do something that will seem small, but will change almost everything on Earth . . .
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The Trip Around the Sun - period of revolution, tilt of axis, orbit
and your head. While facing the lamp, dip your chin into your neck. Now you are spinning at an angle.
Tilt of axis is how much a planet leans while it spins. You might feel that when you are on one side of the
lamp, your forehead is getting a lot of light. When you are on the other side, your chin will get more light.
This is why we have four seasons. When our part of the Earth is leaning away from the sun for some of
the year, it's winter. When it's leaning toward the sun, it's summer. Other planets have different tilts so
their seasons can be longer or shorter. Your planet head is looking a little green . . . You can stop
spinning.
You can get a feel for what the Earth goes through by spinning in circles and walking around the lamp with
your head tilted toward the light. The ovals you make are like the Earth's orbit, which takes 365 days to
travel around the sun. The spinning is like the days and nights. The tilt of your head is what makes the
seasons. Feel a little sick? That's just fine. Even the Earth spews out of a volcano every now and then.
References:
Windows to the Universe. "Axis Tilt" Windows to the Universe, 2012.
<http://www.windows2universe.org/glossary/axis_tilt.html>
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