Earth & Sky

Earth farthest from the sun for the year

Tonight is Friday, Jul 03 2009

After sunset tonight according to U.S. clocks, our planet Earth will reach its most distant point from the sun for this year.

Astronomers call this point aphelion, and, at aphelion we’re about three million miles farther from the sun than we will be six months from now. That’s in contrast to our average distance from the sun of 93 million miles. Looking for Earth’s exact distance from the sun today? It’s at 94,505,048 miles. Last year, on July 4, 2008, the Earth at aphelion was some 8,000 miles more distant, at 94,513,144 miles.

We’re always farthest from the sun in July during northern hemisphere summer – and closest in January during northern hemisphere winter – and that’s a good illustration of the fact that it’s not the Earth’s distance from the sun that creates the seasons on our world. Instead, the seasons result from Earth’s tilt on its axis. Right now, it’s summer in the northern hemisphere because the northern part of Earth is tilted most toward the sun.

Meanwhile, it’s winter in the southern hemisphere because the southern part of Earth is tilted most away from the sun.

So Earth’s varying distance from the sun doesn’t create the seasons. But it does affect the length of the seasons. That’s because, at our farthest from the sun, like now, Earth is traveling most slowly in its orbit. That makes summer the longest season in the northern hemisphere and winter the longest season on the southern half of the globe – in each case by nearly five days.

Written by Deborah Byrd , 3 July 09