Albert Einstein theorized that when a black hole is born, there should be a “ringing” sound from the aftermath and that the sound should be a signature of the black hole’s mass and spin. Physicists from MIT recently heard the ringing for themselves for the first time in history, and were able to predict the mass and spin of the new black hole just as predicted by Einstein. This also proved that no other properties besides mass, spin, and electric charge can be identified of a black hole.
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October 10, 2019