Gravitation, Cosmology, and Cosmic-Ray Physics (1986) / Chapter Skim
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2. Experimental Tests of General Relativity: Highlights
2. Experimental Tests of General Relativity: Highlights
Pages 15-23
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From page 15... ...
EQUIVALENCE PRINCIPLE, EOTVOS TO LUNAR LASER RANGING In his approach to the theory of gravitation, Einstein did not seek to explain the equivalence of gravitational and inertial mass but instead elevated it to the status of a principle and proposed a generalization stating that, locally, gravitation and acceleration are indistinguishable. The most accurate experimental tests of this principle are of the Eotvos type to determine whether the ratio of inertial to (passive)
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From page 16... ...
16 o ._ Ct ._ o ._ o o Cat a' V)
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From page 17... ...
This result constrains a combination of PEN parameters; for the special case of fully conservative metric theories without preferred frame or location effects, it implies that the linear combination 4F - ~ - 3 vanishes to within +0.015. Some metric theories predict a violation of the principle of equivalence for massive bodies because, in these theories, only part of the mass due to gravitational self-energy gravitates, although the principle is obeyed for the contributions to mass from all other forms of energy.
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From page 18... ...
TNER~L SH~SPIN AXIS THEE OF FLIGHT, ~ ~S~ , / 1 ~ TRACK. / me' TRANSPONDER AND / ~ CLOCK 51GNA I 1~ I TWITTER tow ~ rS - CE - AFT l ~ / 1 WITH CLOCK MEL EARTH STATION WITH ATOMIC ~ r CLOCKS ~ , H - BASER REDSHIFT ~magnified;\ ANTES—~ 51( `` T O AY SIGNAL TRACKING SIGNALS —E ARTH STATION 2 t DOPPLER MAGNETIC SHIELDS SOLENOID STORAGE BULB CAVITY R ESONATOR 4420 ~Hz ' ~— E:= ,~rraans—| | H-~4SER| ~— APACE SIGNAL OUTPUT STATE - SELECTOR MAGNET ATOMIC HYDROGEN BEAR ATo~lc HYDROGEN OISSOCIATOR H2 INLET DOPPLER CANCELATION SYSTEM 2 t DOPPLER HOWLER ~ H I t DOPPLER ~ _ ~ FIGURE 2.1 A suborbital clock has measured the gravitational redshift eject; the result agrees with theory to within the experimental accuracy of I part in 104.
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From page 19... ...
Signal retardation measurements currently provide our best test of the important space-curvature effects in general relativity. The increase of the round-trip times for light or radio signals propagating between planets, owing to the direct effect of solar gravitation, is predicted by general relativity to reach a maximum of about 250 As for ray paths that graze the limb of the Sun.
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From page 20... ...
The round-trip travel times of radio signals were measured with uncertainty as small as 10 ns, about 10-~ of the total travel time. The measurements were then fit to an elaborate range model including many solar-system parameters, the relativistic delay, and positions for the spacecraft and tracking stations.
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From page 21... ...
The relativistic contribution to the perihelion advance depends not only on space curvature but also on the nonlinearity of the superposition law for the gravitational potential and on preferred-frame and location effects. If one assumes that the contributions of the solar quadrupole moment and of possible preferred-frame and location effects are negligible, the measurements demonstrate that for fully conservative theories the combination (2 + 2y - Q)
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From page 22... ...
LABORATORY TESTING OF GRAVITATION, SEARCHING FOR THE UNEXPECTED We must not allow these impressive advances afforded by space techniques to overshadow completely the important contributions of laboratory gravitation experiments. Many of these experiments achieve great accuracy by using null techniques, as in the celebrated Eotvos experiments.
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From page 23... ...
This is a fundamental assumption of general relativity and is well tested for passive and inertial masses where large solar-system bodies can be used as the active third mass. Unfortunately, experiments to compare active mass with inertial or passive masses necessarily use laboratory-scale masses.
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