Earth at Aphelion

And then, around Easter of 1605, he decided he had seen enough circles for one lifetime. He concluded that all he had left to try was an ellipse or, as he so eloquently described it: “a single cartful of dung.”

As Kepler drew an ellipse over his data, his eyes lit up. It fit beautifully. In this single moment of unrivaled genius, Kepler solved a problem that had confounded astronomers for centuries. With unbridled joy, he sketched on his work the goddess of victory riding her chariot above the clouds. “The truth of nature, which I had rejected and chased away,” he later wrote, “returned by stealth through the back door, disguising itself to be accepted ... ah, what a foolish bird I have been!”

We now understand that the Earth, too, orbits the sun along an elliptical path, and our distance from the sun varies by about 3% -- hardly enough to contribute to seasonal temperature differences. Those are caused, instead, by the tilt of the Earth’s axis.

Our planet’s equator is tipped about 23.4 degrees to the plane of its orbit around the sun. This means that during June, July and August, the Earth’s Northern Hemisphere is tilted toward the sun and allows sunlight to beat directly down upon us.

Six months and half an orbit later, our planet’s tilt aims the Northern

Hemisphere away from the sun; solar rays then shine down on us at a much shallower angle and cause our temperatures to be lower.

It may surprise your friends to learn that the Earth reaches its farthest point from the sun during our summertime. This year, “aphelion” occurs on July 6 at 4:06 p.m. EDT (1:06 p.m. PDT). Our planet’s nearest point to the sun -- “perihelion” -- won’t occur until Jan. 2, 2024, at 7:38 p.m. EST (4:38 p.m. PST).