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ThenEarth will be at its closest point to the Sun today at 7:00 p.m. U.S.nCentral Time. That closest-to-the-Sun point is called “perihelion.”
ThenEarth will be at its closest point to the Sun today at 7:00 p.m. U.S.nCentral Time. That closest-to-the-Sun point is called “perihelion.”n
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nMostnpeople think of the Earth circling the Sun in a circular orbit –nsee? I just used the verb circling? That’s how we think of it!n– but really its orbit is elliptical. That means it is slightlynoval in shape.
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n(Tonbe precise, a circle is a very special ellipse in which every pointnis equal distance from the geometric center, so what I should say isnthat the orbit of the Earth is a non-circular ellipse.)
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| This diagram shows last year’s perihelion (and also the point at which Earth was farthest from the Sun). NOTE: This diagram is WAY out of scale. |
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Everynellipse has two focus points. Try moving one of the foci of this ellipse, and see how the other focus changes as well to maintain thenelliptical shape. How long and skinny an ellipse can you make? Cannyou make a perfect circle? What happens to the two foci in a circle? n
Everynellipse has two focus points. Try moving one of the foci of this ellipse, and see how the other focus changes as well to maintain thenelliptical shape. How long and skinny an ellipse can you make? Cannyou make a perfect circle? What happens to the two foci in a circle? nn
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- Herenis a website in which you can create an elliptical orbit for “yournplanet.” You can make your orbit closer to a circle or much morenelongated. Notice, with an elongated orbit, that your planet goes anlittle faster when it is closer to the Sun and a little slower whennit is farther away. Also try the zoom in/out and slower/fasternsliders!
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- Tonlearn more about perihelion, check out this website.
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- Youncan make an ellipse with some string and pins and a pencil.nInstructions can be found in Richard Panchyk’s book Galileo for Kids. Orntry the Math Open Reference website.
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nAlsonon this date:
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nWorld Braille Day
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nFirsts for the fourth
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