Earth's Elliptical Orbit

By Dennis Mammana

June 22, 2017 4 min read

Week of June 25-July 1, 2017

Summer is only a couple days old, and already we're baking.

As I write these words, the temperature outside of my desert home is hovering at 118 degrees F, and there's no sign of it letting up anytime in the next few months.

It's times like this that make me think of a common misconception in the minds of many people. To see what I mean, try this experiment: Ask some friends which season of the year they think the Earth is nearest to the sun.

It's amazing how many people believe that the warm weather of summer has something to do with how close we get to the sun, but this isn't true. Besides, if we orbit the sun in a circle, why does this distance change at all?

The solution has to do with the fact that we don't orbit the sun in a circle; in fact, hardly anything in the cosmos does. Most objects revolve about another body in an elliptical orbit. An ellipse is simply a circle that's been squashed, and the amount of squashing an orbit has is measured by its "ellipticity." A circle is also an ellipse — with zero ellipticity!

It was little more than four centuries ago that German mathematician Johannes Kepler discovered that our planet — and others — orbits the sun not along a circular path but along an elliptical path. After struggling for years to fit circular orbits to the measured motions of Mars, all he had to show for his work was 900 pages of calculations and 70 worthless orbits. And then, around Easter 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 his ellipse over the data, his eyes lit up. It fit beautifully. In a single moment of unrivaled genius, Kepler solved a problem that had confounded astronomers for centuries. In 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 recalled, "returned by stealth through the back door, disguising itself to be accepted. ... ah, what a foolish bird I have been!"

We now know that the Earth's distance from the sun does change over the course of its annular orbit, but this change is only about 3 percent, hardly enough to cause a significant change in seasonal temperatures. No, our heating and cooling are caused by the tilt of our planet's axis.

In fact, many people are surprised to learn that our Earth is actually farther from the sun during the Northern Hemisphere summer. The farthest point we reach in 2017, the point astronomers call "aphelion," arrives 1:11 p.m. PDT (4:11 p.m. EDT) on July 3. At that moment we will lie only 94,505,901 miles from the sun. Our nearest point, "perihelion," won't arrive until Jan. 3 of next year.

In the meantime, stay cool. It won't be long before we're complaining about the cold!

 Check out Earth's elliptical orbit this week.
Check out Earth's elliptical orbit this week.

Visit Dennis Mammana at www.dennismammana.com. To read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.

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