Astronomers Planning To Image Milky Way's Central Black Hole

99luftballon writes "Astronomers are planning the Event Horizon Telescope project in Arizona on Wednesday — and say in three or four years they should be able to image the ring of matter around the supermassive black hole at the center of the Milky Way. The black hole is 26,000 light years away, but should be large enough to check if Einstein got his equations right."

Re:Oh, Einstein.

[interkin3tic]

Untested hypotheses that turn out to be wrong often set research back months or years, wasting time testing them. Taking one man's word as law without testing it, if it were wrong, that could cause a huge amount of wasted time.

It would suck if we didn't get teleporters within our lifetimes just because Einstein was a little off and no one bothered to check it.

more of a test of relativistic particle physics

[bcrowell]

It might be a bit of an oversimplification to call this a test of relativity.

Relativity consists of special relativity (SR) and general relativity (GR). GR includes gravity.

SR has been tested in many different ways to extremely high precision. Here [edu-observatory.org] is a summary of experimental tests of SR. Note that even if the faster-than-light neutrino result from CERN/Gran Sasso is correct, it doesn't necessarily conflict with SR. SR doesn't forbid FTL. It only forbids an object from being accelerated from a speed less than c to a speed greater than c.

Here [livingreviews.org] is an article on tests of general relativity. A nice popularization of this kind of thing is the book Was Einstein Right? by Clifford Will. Although GR has not been as thoroughly tested as SR, it has been tested in many different ways. There is not really a heck of a lot of doubt that it's right in many ways. Alternative theories exist, but they are extremely tightly constrained by observation.

We expect that Sagittarius A* is a black hole, and the definition of black hole basically means that it has an event horizon. If, contrary to everyone's expectations, it turns out not to have an event horizon, the most likely interpretation may not actually be that GR is wrong. It may actually mean that there is something wrong with relativistic particle physics. It's possible that the process of formation that we think leads to a black hole actually stops short of forming a black hole, and instead forms some other exotic object. There are various speculations about these things: gravastars, fuzzballs, quark stars, boson stars, q-balls... If we found out that Sgr A* was one of these hypothetical critters, it would be very exciting for the particle physicists, but it would not disprove GR.