And FURTHERMORE,....
GRAVITY PROBE B, the orbiting observatory devoted to testing the
general theory of relativity, has measured the geodetic effect-the
warping of spacetime in the vicinity of and caused by Earth-with a
precision of 1%. The basic approach to studying this subtle effect
is to monitor the precession of gyroscopes onboard the craft in a
polar orbit around the Earth. The observed precession rate, 6.6
arc-seconds per year, is close to that predicted by general
relativity. The geodetic effect can be measured in several ways,
including the use of clocks, the deflection of light, and the
perturbative influence of massive bodies on nearby gyroscopes.


The gyroscopes themselves-four of them for
redundancy-are the most nearly spherical things ever made: the
ping-pong-ball-sized objects are out of round by no more than 10
nm. They are electrostatically held in a small case, spun up to
speeds of 4000 rpm by puffs of gas. The gas is then removed,
creating a vacuum of 10^-12 torr. Covered with niobium and reposing
at a temperature of a few kelvin, the balls are rotating
superconductors, and as such they develop a tiny magnetic signature
which can be read out to fix the sphere*s instantaneous
orientation. (For more information see einstein.stanford.edu)

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THese guys are soooo sexy.



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