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MONDAY JANUARY 22 EARTH-SUN DISTANCE AND THE SEASONS
The earth’s orbit around the sun is not a perfect circle. Rather, it's just a smidge
- that is, oval-shaped. As a result, the earth isn't the same distance from
the sun at all times of the year.
average distance from the earth to the sun is about 93 million miles. But that
ranges from 91 million to about 94 and a half million over the course of a year.
From time to time, I hear this change in earth-sun distance used to explain why we
have seasons. After all, it makes sense that it would be warmer - summer - at the
time of our closest approach to the sun. And colder - winter - when earth is
farthest from the sun.
But there's a
fundamental problem with that argument. When it's winter here, it's
summer in the Southern Hemisphere, and vice versa. So the changes in distance
between the sun and the earth can't be the cause of the seasons, because you can't
have it both ways. Another way to look at this - solely from a Northern Hemisphere
perspective - is to realize that the earth made its closest approach to the sun just
about ten days ago - right smack dab in the middle of our winter.