| Chronology | Current Month | Current Thread | Current Date |
| [Year List] [Month List (current year)] | [Date Index] [Thread Index] | [Thread Prev] [Thread Next] | [Date Prev] [Date Next] |
Savinainen Antti wrote:
is it possible
to measure changes of gravitation force due to Moon
when you have:
-- a laboratory somewhere on the Earth
-- constant conditions (e.g. density of air which may affect buoyance etc.) in
the laboratory
-- very precise balance
-- object of known mass on the balance
So all other things being equal: would the *balance reading* in the laboratory
vary in time due to change in relative position of the Earth and Moon?
This is exactly the right way to ask the
question. This sets it up very clearly
as a _physics_ question.
My answer is no. Should I change my opinion?
Yes, you should change.
The instrument you describe -- very precise balance
with a known mass -- is called a gravimeter.
You are 100% correct that air density affects the
gravimeter reading via buoyancy "etc." -- in addition
to buoyancy there is the direct gravitational
attraction of the mass of air above you. You can
correct for this if you own a barometer.
Once you make the barometric correction, tidal
effects will jump out at you. You won't see
just the direct effect of the moon's tide-producing
field; gravimeter will be affected by the response
of the earth (oceans and solid earth) to said field.
http://www.google.com/search?q=gravimeter+tidal
The sun's tide-producing field gets into the act,
too.