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Physicists have conducted the most high-energy test of the speed of light yet, and found that it is still constant, everywhere in the Universe, even in gamma rays spewed out of sources such as exploding stars.
This means that, even at the highest energies we can detect, one of the pillars of Albert Einstein’s theory of special relativity still stands firm.
“How relativity behaves at very high energies has real consequences for the world around us,” said astrophysicist Pat Harding of Los Alamos National Laboratory in New Mexico.