On 7/15/11 12:48 AM, Tom Van Baak (lab/iPad) wrote:
1E14 we might be able to notice
Hal,
No. Look at the adev of the earth (earlier posting). The length of earth day
varies in the *milli*second range, day to day. VLBI measurements are under 0.1
millisecond, which comes to about 1e-9 resolution.
Realize that none of the NASA "earthquake may have shortened" press releases
are about real measurements of rotation. They are just impressive models of changes in
momentum. The predictions are in the *micro*second range. The press does not always
distinguish between milli and micro.
And, there's a somewhat non-noise-free-channel from the guys doing the
calculations to the public affairs officer to the media.
This kind of thing is actually sort of interesting in a planetary sense.
While earth is pretty stable, there are places where there are a lot
more earthquakes and internal tidal forces (Jupiter's moons) and changes
in rotation rate of the moons might be detectable by radar.
Is Io gradually slowing? There's also coupling to Jupiter, of course
(e.g. our Moon having a rotation rate synced to orbital period)
What about Mercury?
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