July 2006: Earth at Aphelion
With the hot days of July upon us, you might think we're about as close as we can get
to the Sun. Actually, nothing could be farther from the truth. On July 3, 2006, 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's orbit around the Sun is a bit lopsided, its distance from the Sun varies throughout the
year. Sometimes, we're as close as 91.5 million miles; at other times, we're as far away as 94.5 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 aphelion resides to elongate. At the present time, that makes summer the longest season in our Northern Hemisphere
and winter the longest in the hemisphere "Down Under."
copyright 2002 and 2006 by Bruce McClure
June 2006 Feature * August 2006 Feature