[time-nuts] Latitude and longitude question
Hal Murray
hmurray at suespammers.org
Mon Jul 10 23:04:21 UTC 2006
> I just read an article about measuring gravitational waves in the
> latest IEEE about the effects of tides and the moon gravitation on
> the earth-crust - that the earth crust moves up and down about 30cm
> every day, plus the gravitational effects cause about 300ps shift
> day to day.
Friends in the radio astronomy business (VLBI) told me about the tide problem
several years ago. They need to know where their antennas are so they can
compute what the signal looks like. Their database of antenna positions also
includes velocity. :)
The other place where I heard about (solid) earth tides was a paper from
CERN. They weren't getting as good an answer as then expected. Finally,
they corrected for the phase of the moon (really tides) and their data looked
much better. Their experiment was very very sensitive to the diameter of the
ring. It gets slightly bigger when the earth expands due to the tide. That
was many years ago. Probably more than 10.
The article from Physics Today March 2006, Time Too Good to Be True
http://www.physicstoday.org/vol-59/iss-3/p10.html
discusses gravitational blue shift, but I don't remember any numbers.
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