From B. AUGENSTEIN
Jim Baggott’s review of Time, Space and Philosophy, by Christopher Ray
(Review, 25 January) contains some serious errors on the observational tests
of general relativity. He cites as tests ‘the perihelion of Mercury’ and
the ‘bending of starlight by the Sun’, and ignores all of the more modern
high precision experimental tests of general relativity already accomplished.
These latter tests include: the Pound-Rebka gravitational red shift test;
the Taylor et al. binary pulsar test; reruns of the Eotvos tests; the Hafele-Keating
aircraft tests combining gravitational red shift and time dilation; the
Vessot-Levine rocket tests of the same; the Shapiro time delay tests; the
Nordtvedt null test of the strong equivalence principle; and variants and
improved repetitions of all such tests.
Finally, the Global Positioning System of satellites, for its effective
and accurate functioning, also requires incorporation of general relativity
effects (as well as numerous special relativity effects, of course) to achieve
its measured accuracies. All in all, there is large-scale experimental verification
of general relativity, very considerably beyond the two ‘classical’ tests
cited by Baggott.
B. Augenstein Santa Monica, California, US
