We find
that general relativity has held up under extensive experimental scrutiny.
The question then arises, why bother to continue to test it? One
reason is that gravity is a fundamental interaction of nature, and as
such requires the most solid empirical underpinning we can provide.
Another is that all attempts to quantize gravity and to unify it with
the other forces suggest that the standard general relativity of Einstein is
not likely to be the last word.
Furthermore, the predictions of general relativity are fixed;
the theory contains
no adjustable constants so nothing can be changed. Thus every test
of the theory is either a potentially deadly test or a possible probe for
new physics. Although it is remarkable
that this theory, born 80 years ago out of almost pure thought,
has managed to survive every test, the possibility of finding
a discrepancy will continue to drive experiments for years to come.
