https://motherboard.vice.com/en_us/article/pavz5v/atomic-clocks-einsteins-elevator-nist

Monday, physicists from the National Institute of Standards and Technology published the results of a 14-year experiment that used some of the most accurate atomic clocks in the world to test a fundamental principle in the theory of general relativity. The results, published in Nature Physics, offer the most precise confirmation of one of the core concepts of Einstein’s unified theory of spacetime and gravity, the equivalence principle.

The experiment involved tracking the measurements of 12 atomic clocks located in the United States, Germany, France, Italy, and the United Kingdom from 1999 to 2014. Based on Einstein’s theory of general relativity, the relationship between the measurements of these clocks shouldn’t change as the Earth orbits the Sun. This is exactly what the physicists found, confirming several similar experiments that occurred over the years.