Theory of Relativity
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A potentially divisive theory suggests Einstein may have been wrong to say the speed of light is a constant - and the claims could soon be tested with a new generation of space telescopes.

Since it was first proposed more than 100 years ago, Einstein's theory of general relativity has been one of the fundamental theories upon which our understanding of the Universe is built. His groundbreaking theory relies on the notion that the speed of light is always a constant value - but a controversial new theory has been proposed that has the potential to turn this idea on its head.

Not only does the paper say Einstein was wrong about the speed of light, it also describes - for the first time - how can this notion can be tested in the future.

Professor João Magueijo from Imperial College London, and Dr Niayesh Afshordi from the University of Waterloo in Canada built the theory on a question about the very early Universe, which has plagued cosmologists for centuries.

In terms of the density of stars and galaxies, the Universe looks generally consistent over huge distances, which means light must have travelled far enough to reach every corner - otherwise there would be dense patches and light patches.

This has previously been explained by a theory called inflation, that says at the very start of the Universe there was a period of incredibly rapid growth. The new theory does away with inflation.

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