Date: 1999 - 2000
What makes the sun stay in space?
Where else would it go? Are you thinking that it might fall down
to the Earth? But the Sun is much, much bigger than the Earth. Maybe
that doesn't make sense to you, because the Sun looks small up in the
sky. But that's just because it is far away. You know that when you
are up high in a building or in an airplane the cars and people on the
ground look teeny tiny, like toys. It's the same way with the Sun: it
only *looks* small because it is so very far away. But actually it's
much bigger than the Earth. So it can't very well fall down to the
Earth, can it? It's much more believable that the Earth might fall
onto the surface of the Sun.
And it does, as a matter of fact. The Earth falls towards the
Sun's surface all the time. But, you see, the Earth is also moving
sideways, like a rock that is not dropped straight down but is thrown
sideways. It turns out that by the time the Earth reaches where the
Sun's surface was when the Earth started falling, the Earth has
already gone past the edge of the Sun. That is, the Earth falls
toward the Sun's surface, but misses it. Then the Earth comes around
for another try, falling toward the *back* side of the Sun. And the
Earth misses again. The Earth tries again from the front, and misses,
and so on forever. What ends up happening is the Earth goes around
and around the Sun.
The Earth doesn't miss hitting the Sun by as much during December
and January, so it is closer to the Sun at that time than during June
and July. That's why the winter in the North (during December) is not
as cold as the winter in the South (during July).
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Update: June 2012