Barger and Olsson page 295 claim that the earth's rotation is slowing
down at 44 ns per day due to tidal friction. I have checked the math
and come up with a similar answer to within a factor of 2. (Most of
the discrepancy is probably due to what value to use for the moment
of inertia I of the earth. I used the naive value of 0.4MR^2,
undoubtedly an overestimate because of earth's dense core. BTW, is
measurement of the rate at which the earth-moon distance is
increasing, namely 0.5 cm/month, an accurate way to determine I?)
Anyhow, they then say this amounts to 28 s/century. Unless I'm being
really dumb (always possible, if not probable), this is about 4
orders of magnitude too large.
But, they claim that this is confirmed by the fact that astronomical
events such as eclipses have been found to run systematically ahead
of calculations based on observations over preceding centuries. Is
this claim correct? If so, what is the correct explanation of it,
since the 44 ns/day is not enough?
--
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.