This Einstein guy, that is.
In unique stellar laboratory, Einstein’s theory passes strict, new test
Precession of binary neutron stars.
Studies of other pulsars in binary systems had indicated that such wobbling occurred, but could not produce precise measurements of the amount of wobbling.
“Measuring the amount of wobbling is what tests the details of Einstein’s theory and gives a benchmark that any alternative gravitational theories must meet,” said Scott Ransom of the National Radio Astronomy Observatory.
The eclipses allowed the astronomers to pin down the geometry of the double-pulsar system and track changes in the orientation of the spin axis of one of them. As one pulsar’s spin axis slowly moved, the pattern of signal blockages as the other passed behind it also changed. The signal from the pulsar in back is absorbed by the ionized gas in the other’s magnetosphere.
http://www.physics.mcgill.ca/~bretonr/doublepulsar/
There is one but observed reality. *All* useful gravitation theories overall agree. Tested disagreement is more interesting and important.
GR postulates isotropic vacuum and then the Equivalence Principle, plus contingent spacetime curvature via the elevator Gedankenexperiment. Testable alternatives exist. Ashtekar resolved GR into chiral halves. Teleparallelism through spacetime torsion (transforming like Lorentz force in electrodynamics) allows a chiral vacuum background. The EP would then suffer violation by opposite parity (chirality in all directions) mass distributions. EM, lacking configuration, would be inert.
Do left and right shoes violate the Equivalence Principle? If so, GR is wrong without ever having made a bad prediction – two of its founding postulates would be falsified. Perturbative string theory (BRST invariance) also dies despite having made zero predictions within its 10^1000 vacuum solutions. Somebody should look (PDF).