In 1905, a 26-year-old Albert Einstein changed physics forever when he outlined his theory of special relativity. This theory outlined the relationship between space and time and is founded on two fundamental assumptions: the laws of physics are the same for all non-accelerating observers, and the speed of light in a vacuum is always the same.
Over the last century, Einstein’s theories of relativity (both special and general) have withstood the trials of experimental verification and been used to explain a number of physical processes, including the origins of our universe. But in the late 1990s, a handful of physicists challenged one of the fundamental assumptions underlying Einstein’s theory of special relativity: Instead of the speed of light being constant, they proposed that light was faster in the early universe than it is now.
This theory of the variable speed of light was—and still is—controversial. But according to a new paper published in November in the physics journal Physical Review D, it could be experimentally tested in the near future. If the experiments validate the theory, it means that the laws of nature weren’t always the same as what we experience today and would require a serious revision of Einstein’s theory of gravity.
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