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This is Scientific American — 60-Second Science. I'm Steve Mirsky.
Happy New Year! And if you've been away from work for a few days, you deserve some time off. After all, you've traveled far. Even if you just stayed at home. According to NASA, just by being on the planet Earth in the last year, you've zipped about 584 million miles around the sun. At an average speed of about 67,000 miles per hour. (Siren sound.) Hey, I wasn't speeding—in my inertial reference frame.
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 farthest distance. Which would explain why summer seems to zip by, except that 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 525,960 minutes. Or 31,557,600 seconds. Tick tock.
For Scientific American — 60-Second Science Science. I'm Steve Mirsky.
