Jim Heckman wrote: >John Baez wrote: >> Okay, here comes the puzzle. The earth is not spinning >> exactly around the first principal axis. It's a bit off, >> so it wobbles. Estimate the period of this wobble! >Well... On dimensional grounds alone, it seems like it would almost >*have* to be ~( I1 / (I1-I2) ) times the period of the earth's rotation... >(I'm *guessing* that the wobble period -> infinity rather than -> 0 as >earth -> spherical.)Are you also guessing that the wobble period doesn't depend on the wobble tilt, or something like that? And is there some reason you're guessing this?
>Well... Again dimensionally, inertia is (mass * distance^2). I'm pretty sure >earth's radius is ~6700 kilometers and I *think* the polar vs. equatorial >flattening is ~50 kilometers, so > >( I1 / (I1-I2) ) ~ ( 6700^2 / (6700^2 - (6700-50)^2) ) ~ 70 > >so... ~70 days?I'd prefer not to comment on this until I get a few more takers - I don't want to spoil the fun.
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