By tracking the moon's location to within 1 centimeter, astronomers have put general relativity, Albert Einstein's theory of gravity, to a stringent new test. The theory stood up. In a separate experiment, physicists reconfirmed Einstein's older predictions on the stretching of time.
While both general relativity and quantum theory so far fit experimental data very well, their incompatibility makes physicists believe that at small scales either one of them or both must be wrong. Scientists constantly work to improve the sensitivity of their experiments to violations that might point to a new "theory of everything."