Earth at Aphelion

StarDate: July 5, 2010

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It probably doesn't sound right on a hot summer day, but the Sun is actually farthest from us for the entire year this week -- more than 94 million miles.

Earth's orbit around the Sun is a little bit lopsided. The average distance to the Sun is about 93 million miles. But during the year, that distance varies by about three percent.

That slight variation is known as the "eccentricity" of Earth's orbit. The orbits of all the planets are eccentric, but by varying amounts. Venus's orbit is the least eccentric -- less than one percent -- while Mercury's is the greatest, at about 20 percent.

In fact, it's almost impossible for one body to have a perfectly circular orbit around another. Earth and the other planets of the solar system, for example, are pushed and pulled by the gravity of all the other planets. And powerful collisions with other bodies have also skewed their orbits.

As Earth's distance from the Sun changes, so does the amount of energy we receive from the Sun. At our closest, in January, we receive about six percent more total energy than we're getting right now.

Surprisingly, though, there's little impact on our planet's climate. That's because Earth's atmosphere and oceans do a great job of storing heat and distributing it around the planet. That's why we can have really hot days during summer here in the northern hemisphere, even though the Sun is three million miles farther than during the dead of winter.

Script by Damond Benningfield, Copyright 2010

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