lew@ihlpa.UUCP (Lew Mammel, Jr.) (03/20/85)
I believe a group at Harvard demonstrated General Relativity circa 1970 by "dropping photons down the stairwell" of the physics building. This experiment depended on the Mossbauer effect, which provides an ultrafine resolution of gamma ray absorption. The Mossbauer effect is the absorption of a gamma ray by a nucleus in a crystal lattice where the lattice as a whole absorbs the recoil. This is more technically known as the "zero phonon line" of the absorption spectrum. Because of the large mass of the macroscopic lattice the line is VERY sharp. Sorry I can't be quantitative, but you could look it up. A preliminary experiment measured the velocity redshift with a sinusoidally oscillating source. The velocities involved were a few cm/sec, but the apparatus had no trouble resolving the redshift. They then proceeded to the stairwell where they measured the GRAVITATIONAL redshift and found it to be in agreement with the prediction of General Relativity (as well as half a dozen rival theories no doubt.) Lew Mammel, Jr. ihnp4!ihlpa!lew
karsh@geowhiz.UUCP (Bruce Karsh) (03/22/85)
I did not see the original posting of this Subject, but I assume
that it asked about experimental verification of *General* relativity.
It is interesting that there is now at least one engineering aplication
of GR. The GPS sattelite system, which provides ultra accurate position
and time signals for navigational and timing purposes, requires GR
corrections in order to work.
The article that I read about this in is:
Microwave Systems News
Volume 14, Number 12
November 1984
The part about GR is on page 75 of the article.
According to the article, the result of not including the relativistic
corrections would be an error of 11 km/day. The system with the correction
is good to a few meters with no accumulated error.
The article states that GPS is a continual application and demonstration
of the Theory of Relativity.
--
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{ihnp4,seismo}!uwvax!geowhiz!karsh | Send for the Free Postal Course today!physics@utcs.UUCP (David Harrison) (03/25/85)
For an everyday experimental verification of GR, Hafele and Keating flew Cesium beam atomic clocks around the world on commerical jetliners in the early '70s. One clock went East, one went West, and one "stayed home" [like the third little piggie]. There is a special relativity factor due to the motion, and a general relativity factor because of the altitude of the flights. Because of the Earth's rotation the spec. rel. factor is different for the moving clocks; in fact in an inertial frame the West one is the most stationary. The predicted and measured results were discrepancies of from about 50 to about 250 nanoseconds relative to the earth clock. The work was published in Phys. Rev. Letters. David Harrison Dept. of Physics Univ. of Toronto ...!utzoo!utcs!physics
myers@bnl.UUCP (eric myers) (03/29/85)
> For an everyday experimental verification of GR, Hafele and > Keating flew Cesium beam atomic clocks around the world on > commerical jetliners in the early '70s. One clock went East, > one went West, and one "stayed home" [like the third little > piggie]. ... > > The work was published in Phys. Rev. Letters. The experiment is also described in J.D. Jackson's book "Electrodynamics", (page 521). The reference to the experiment is : J.C. Hefele, R.E. Keating, Science, vol 177, pg 166, 168 (1972) Eric Myers Brookhaven National Laboratory