Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: slowing down the earth's spin



Thanks to Hugh, John M, Brian, David (and anyone whose name will be
in the next digest :-) for their prompt and well thought out replies.

Once again, the answer is I was missing the obvious. Here's the
explanation I like best:

We begin with a day exactly 24 h long.
In a century, a day will be longer by 44 ns * 1 century = 1.61 ms.
Thus on average during this century a day is longer by 0.8 ms.
Hence timekeeping will now be 0.8 ms * 1 century = 29 s out of whack.

The actual moment of inertia of the Earth about its spin axis is much
closer to I = 0.33078*M*R^2 where R is the equatorial radius.

How was this value obtained? From a model of the earth or from some
timekeeping kind of measurement?
--
Carl E. Mungan, Asst. Prof. of Physics 410-293-6680 (O) -3729 (F)
U.S. Naval Academy, Stop 9C, Annapolis, MD 21402-5026
mungan@usna.edu http://physics.usna.edu/physics/faculty/mungan/

This posting is the position of the writer, not that of SUNY-BSC, NAU or the AAPT.