Scientists behind a theory that the speed of light is variable -- and not constant as Einstein suggested -- have made a prediction that could be tested.
Einstein observed that the speed of light remains the same in any situation, and this meant that space and time could be different in different situations.
The assumption that the speed of light is constant, and always has been, underpins many theories in physics, such as Einstein's theory of general relativity. In particular, it plays a role in models of what happened in the very early universe, seconds after the Big Bang.
But some researchers have suggested that the speed of light could have been much higher in this early universe. Now, one of this theory's originators, Professor João Magueijo from Imperial College London, working with Dr Niayesh Afshordi at the Perimeter Institute in Canada, has made a prediction that could be used to test the theory's validity.
Structures in the universe, for example galaxies, all formed from fluctuations in the early universe -- tiny differences in density in certain regions. A record of these early fluctuations is imprinted on the cosmic microwave background -- a map of the oldest light in the universe -- in the form of a 'spectral index'.
And we have the familiar refrain, the speed of light is an adjustment for the vacuum, but it should basically be nearly constant.
When we measure the speed of light, the error is much less than Plank' constant, so setting it constant works fine. I has the same error function it always had, and under the right circumstance, the vacuum will take the higher guess.
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