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In which season does the Earth move fastest aroud the Sun?

Posted by Miki S.
Grade level: K-3
School: Jefferson Elementary School
City: Honolulu State/Province: HI
Country: USA
Area of science: Astronomy


My teacher asked this but I can't find the answer a the library or on the WWW. Please help me. Thank you.

Hi! You have asked a pretty good question. The answer depends on the shape of the path the Earth takes around the Sun.

For a long time, it was thought the Sun went around the Earth. It sure looks that way to us, sitting on the Earth! But really the Earth goes around the Sun, and the path it takes is called its orbit. After people figured out the Earth went around the Sun, they thought the Earth's orbit was a big circle. It wasn't until much later they found out the Earth's orbit is really an ellipse, or oval shape.

Not only that, but the Sun is not at the center of the ellipse. It is just off to one side of it, so that one part of Earth's orbit is closer to the Sun than all the other parts. Now, the reason the Earth goes around the Sun is because of gravity. The Sun's gravity pulls on the Earth, and how hard it pulls depends on how close the Earth is to the Sun. The closer the Earth is, the harder the Sun pulls. Now imagine you have a rope and are pulling a rock tied to the end. If you don't pull very hard, the rock won't move very fast. But if you pull the rope really hard, the rock will move really fast!

The same thing happens with the Sun and the Earth. When the Earth is close to the Sun, the Sun pulls hardest, and the Earth moves the fastest. The date this happens is usually early in January. The last time the Earth was closest to the Sun was January 4, 1996. So that means it is Winter when the Earth is closest to the Sun! Now you're in Hawaii, so that may not surprise you. But where I am (Washington, DC) it gets very cold in Winter and people are always surprised to hear that we are closest to the Sun in Winter. But the temperature does not depend much on how far we are from the Sun, but instead how the Earth is tilted as it goes around the Sun.

You can find more information about this at the following sites:

This is the web page for the "Earth and Sky" radio program, which talks a lot about astronomy.
I have my own web site which talks about what causes the seasons. It may be a bit complicated, but maybe the teacher can help you with it!

©2008 Phil Plait. All Rights Reserved.

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