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Q&A: General Astronomy and Space Science

Q:
My friend believes that the universe is only 6000 years old. As proof of this he says the rotation of the Earth is slowing one second a day. If you add one second a day for every day from today back to the dinosaurs, the rotation would be so fast the dinosaurs would not survive. Is the Earth really slowing? If so, how does science disprove the rest of this logic?

A:
The length of the day varies for many reasons -- ocean tides, atmospheric circulation, internal effects, which are cyclical or random, and the transfer of angular momentum to the Moon's orbital motion, which causes the length of the day to increase by about 1.5 - 2 milliseconds per century.

Extrapolating back to the time of the dinosaurs about 100 million years ago, the length of the day would have been about 2000 seconds shorter. Still plenty of time for a dinosaur to find a meal and get a good night's sleep, I would imagine.

Reference:
http://maia.usno.navy.mil/eo/whatiseop.html.

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