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July 2002: Earth at Aphelion


With the hot days of July now upon us, you might think we're about as close as we can get to the Sun. Actually, nothing could be further from the truth. On July 5, 2002, the Earth reaches its most distant point from the Sun for the year -- a point astronomers call "aphelion."
On the average, our planet resides about 93 million miles away from the Sun. But since the Earth doesn't orbit the Sun in a perfect circle, its distance from the Sun varies throughout the year. Sometimes, we're as close as 91 and 1/2 million miles; at other times, we're as far away as 94 and 1/2 million.
Keep in mind, however, that it's not the Earth's distance from the Sun that determines the seasons, but the tilt of the Earth's axis. In summer we tilt toward the Sun and in winter we tilt away.
Although aphelion comes when it's summer in our Northern Hemisphere, it doesn't always coincide with the hot season over the long course of time. One thousand years ago, aphelion occurred at springtime, but five thousand years into the future, it'll take place in autumn.
Earth's varying distance from the Sun -- though not responsible for the seasons -- does affect seasonal length. At aphelion the Earth travels most slowly in its orbit, causing the season in which it resides to elongate. At the present time, this makes summer the longest season in our Northern Hemisphere, and winter the longest in the Hemisphere "Down Under."

Copyright 2002 by Bruce McClure

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