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→Local Position Invariance
In 2018, observations of a star orbiting the supermassive black hole "Sagittarius A*" at the center of our galaxy, showed that the light was stretched from the black hole's gravity just as relativity predicted. The star orbits Sagittarius A* at speeds of up to 16 million miles per hour. This was the first observation of such intense gravity.<ref>https://www.nbcnews.com/mach/science/einstein-s-theory-relativity-aces-its-first-black-hole-test-ncna896641</ref>
In 2018, observations of a star orbiting the supermassive black hole "Sagittarius A*" at the center of our galaxy, showed that the light was stretched from the black hole's gravity just as relativity predicted. The star orbits Sagittarius A* at speeds of up to 16 million miles per hour. This was the first observation of such intense gravity.<ref>https://www.nbcnews.com/mach/science/einstein-s-theory-relativity-aces-its-first-black-hole-test-ncna896641</ref>
===Local Position Invariance===
The ''equivalence principle'', which is the underpinning of gravity under general relativity, states that there is absolutely no perceived effect of gravity on an object in free fall, that is, in a gravitational field. This has been tested many times, and is the basis of all space-time calculations in relativity. But in 2019, it was reported to have been successfully tested in a gravitational field very much stronger than ever before. The phenomenon is called ''local position invariance'', or LPI. It was measured on the light emitted from a star called "S2", closely orbiting the "Sagittarius A*" black hole at the center of the galaxy. The gravitational field that S2 is subject to is vastly more powerful than any other gravitational field that has been measured<ref>https://physics.aps.org/synopsis-for/10.1103/PhysRevLett.122.101102</ref>.
===Geodetic Precession===
===Geodetic Precession===