科学美国人60秒:Happy New Solar Ellipse!

Happy New Year! And don’t feel bad about taking today off. After all, you’ve traveled far.  And I’m not talking about the trip home from the party. According to NASA, just by being on the planet earth in the last year, you’ve zipped about 584 million miles around the sun to get back where you were. At an average speed of about 67,000 miles per hour. Again, not talking about the drive home from the party.

Of course, the trip was not a perfect circle. As Kepler showed, the earth’s orbit is an ellipse, with the sun at one of the two focal points. He also figured out the planet goes faster when it’s at perihelion, nearer the sun, than when it’s at aphelion, its furthest distance. Which would explain why summer seems to zip by, except the seasons are a function of the tilt of the earth’s axis, not its different distances from the sun. And the earth rotated 365 and a quarter times during its sweep around the sun. The trip took 8,766 hours. Or 31,557,600 seconds. Or 525,960 minutes just like this one.

—Steve Mirsky