A Test For Relativity

There are currently two (count ’em, two) pillars of physics that have withstood all the tests to which they’ve been put; quantum mechanics and relativity. This is something akin to the position physics was in just before the beginning of the 20th century, when it was said (and I paraphrase) “physics is almost completely understood. There’s just one or two little things left to be explained about the hydrogen spectrum…”

Now, understand; there’s a couple of pretty odd and maybe wonderful ideas floating around that are very popular in physics right now, not least of which is string theory (and also dark matter/dark energy in astronomy). These ideas may or may not pan out, and in fact, in the case of string theory, the hot debate is whether it possible, even in theory, to test it.

Relativity, though, has already past many tests, some of remarkable precision. If you can perform an experiment that shows a result in disagreement with Einstein, then you most certainly will win a Nobel Prize.

Yet here is one such experiment. Maybe.

The MAGIC gamma-ray telescope team has just released an eye-popping preprint (following up earlier work) describing a search for an observational hint of quantum gravity. What they’ve seen is that higher-energy gamma rays from an extragalactic flare arrive later than lower-energy ones. Is this because they travel through space a little bit slower, contrary to one of the postulates underlying Einstein’s special theory of relativity — namely, that radiation travels through the vacuum at the same speed no matter what?

It’s not a done deal, yet. There are many possible ways in which the higher energy gamma rays might have been created after the lower energy ones, which would mean relativity, as we know it, is safe. But if none of these mechanisms can be shown to be in operation (bit if), then this is a big deal.

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Explore posts in the same categories: Astronomy, Science

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