If this discovery turns out to be true, would it really “overturn Einstein’s theory of relativity”?
What it would do is show that one type of string theory, which is a theory larger and more encompassing than relativity, may be correct. If unmassed particles don’t move exactly at the speed of light then relativity can’t be exactly correct, but there are already so many problems with trying to create a quantum gravity that everybody is sure that some corrections will have to be made. This particular finding - if it holds up and that’s a very big if - allows for a test of a string theory that few had thought possible. A single test, even if string theory passes it, is by no means a proof, however.
This blog has a pretty good English language summary of the controversy, with links to lots of other sites.
Here’s a start of what the controversy is all about.
String theory, to the best of my knowledge, doesn’t actually predict these kinds of effects; it’s loop quantum gravity, a rather different theory, that does. But your main point holds: relativity will still work in most situations, just not when energies get too high.
Although I don’t understand the particular issue, I would like to say that the idea of “overturning” a scientific theory is usually nonesense. Einstein didn’t “overturn” Newtonian mechanics; it refined it and extended it to a domain in which it had never really been tested. Even Newton didn’t exactly overturn Aristotelian mechanics; he mostly made the claim that bodies will continue in motion unless acted on by an outside force. On earth, every moving body is acted on by friction and Newton realized that there is no (or very little) friction in outer space.
So it is entirely possible, even likely, that Einstein’s theory will eventually be modified in some way, but only in domains in which it has never been tested. It seems that the OP concerns special relativity. General relativity had never been really well tested until the GPS system was in place. The satelite clocks have to be adjusted for the fact that gravity is less strong up there and so they run a bit faster. But for the correction built it to them, the positioning would drift by something like 8 miles a day, every day. Without the correction, it would be reporting you in Australia by now.
But even this will not be the last word. In fact, I rather doubt that there will ever be a final word. But I wish I would never hear of overturning a theory. Doesn’t happen.
It is worth noting that Newtonian Mechanics work in most situations, just not when energies get too high.
Considering how much simpler it is to use this is just fine for most things we go about in our day-to-day lives.
Depends on what you mean by “well-tested”. The first “new” prediction of GR to be tested was light bending in a gravitational field, in 1919 (although that wasn’t fully nailed down until the '60s.) A very precise experiment was performed in 1971 to test time dilation in a gravitational field, involving sending two hydrogen maser clocks around the world on planes going in opposite directions. In 1976, a hydrogen maser clock was launched into orbit to test exactly the same kind of time dilation that the GPS satellites have to take into account. And there’s also the Hulse-Taylor binary pulsar, whose orbital decay very precisely matches the predictions of GR, and whose discoverers got the Nobel Prize in 1993.
So to say that GR hadn’t been tested before GPS came along isn’t really correct. It is true, however, that GPS was the first “practical” use of general relativity, and as such these tests became more important because of it.