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Close to the Sun

January 3, 2015

From regions where winter has already taken a firm grip, the Sun can seem pale and remote. Yet Earth is actually closest to our star for the entire year late tonight — about a million-and-a-half miles closer than average. We’ll start to pull away from it tomorrow, heading toward our farthest point in early summer.

The orbits of Earth and the other planets aren’t circular. Instead, they’re elliptical — they look like circles that have been flattened a bit. Because of that, each planet’s distance from the Sun varies.

A planet’s orbit is shaped by many factors. Perhaps the most important is the gravitational influence of the other planets. They can nudge a world inward or outward, making it move a little faster at some times and slower at others.

In the early solar system, in fact, the orbits of the giant outer planets may have changed dramatically. Jupiter may have moved inward almost to the orbit of Mars for a while, and Neptune and Uranus may even have switched places.

This activity seems to have had little effect on Earth’s position; our planet has probably always been at about the same distance from the Sun. But the gravitational influence of the other planets has certainly helped give our planet’s orbit its current shape.

One effect of an elliptical orbit is that a planet moves fastest when it’s closest to the Sun, as we are now. That makes winter the shortest season in the northern hemisphere — about five days shorter than summer.


Script by Damond Benningfield, Copyright 2014

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