On 1/23/12 1:20 PM, Doug Millar wrote:
A mercury mirror is better than a plumb bob.
Doug
Or Gallium?
But what sort of precision are we looking for here?
1 second of earth rotation is 1/240th degree (15 arc seconds), about
0.07 milliradian.
So on a plumb bob a meter long, you're looking for a displacement of
0.07 mm... Seems a bit challenging.
Even with an optical scheme looking for the reflection coming back from
your mirror a meter away, that's just 70 microns.. Well, at least it's
not a few wavelengths of light.
But I can see a lot of practical problems at that level of precision:
Vibration isolation?
Local gravitational anomalies. (I seem to recall tens of arcseconds for
this)
difference between local gravity vector and normal of the ellipsoid or
geoid due to non spherical earth, etc. (this one is calculatable)
_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
