They don’t make light like they used to. Today’s light, chugging along at 299,792,458 metres per second, would have been blown away by photons of the early universe travelling trillions of times faster – or so says a newly beefed-up theory of physics.

Portuguese physicist João Magueijo first proposed superfast light in 1998 to explain the uniform temperature of the early universe. But because it contradicts Albert Einstein’s theory of special relativity, it never quite caught on.

Now, writing in Physical Review D, Magueijo and his colleague Niayesh Afshordi produced a testable prediction from the theory. That’s something a rival idea, cosmic inflation, has never managed to achieve.

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