Experimental tests of General Relativity

The principal cornerstone of all scientific theory is experimental evidence, yet in the case of General Relativity Theory, for almost fifty years, such evidence has been largely lacking. The early experiments th at were said to verify Einstein’s theory, while technological triumphs of their day, must be viewed by today’s standards as only weak or qualitative confirmations, beset as many of them were by large statistical and systematic errors. On the one hand this situation is surprising, in view of the major impact that General Relativity has had on our view of space and time and of the creation and fate of the universe. On the other hand it is not so surprising, in view of the extreme weakness of the gravitational interaction and the consequent difficulty of most experiments. However, the astronomical and technological revolution of the 1960s and 1970s has altered this situation. Advances in atomic clocks, radar and laser ranging to planets and spacecraft, radio interferometry, low-noise motion sensors such as gravimeters, to name a few, have made the high-precision testing of gravitation theory almost routine. In this paper we summarize the present experimental evidence for General Relativity and describe new arenas for future tests of gravitational theory. For a more detailed review see Will (1979).