Tau.Neutrino said:
Einstein proved right in another galaxy
Astronomers have made the most precise test of gravity outside our own solar system. By combining data taken with NASA’s Hubble Space Telescope and the European Southern Observatory’s Very Large Telescope, the researchers show that gravity in this galaxy behaves as predicted by Albert Einstein’s general theory of relativity, confirming the theory’s validity on galactic scales.
more…
> “General Relativity predicts that massive objects deform space-time, this means that when light passes near another galaxy the light’s path is deflected. If two galaxies are aligned along our line of sight this can give rise to a phenomenon, called strong gravitational lensing, where we see multiple images of the background galaxy. If we know the mass of the foreground galaxy, then the amount of separation between the multiple images tells us if General Relativity is the correct theory of gravity on galactic scales.”
That’s back to front isn’t it? Assuming the correctness of GR, from the distances to the multiple images calculate the mass of the foreground galaxy. That’s how it’s been done in the past. GR is far more accurate than estimates of galaxy mass derived in other ways.
> the galaxy ESO325-G004 is amongst the closest lenses, at 500 million light years from Earth. We used data from the Very Large Telescope in Chile to measure how fast the stars were moving in E325 — this let us infer how much mass there must be in E325 to hold these stars in orbit.
Ah, virial theorem. That would work.
Unfortunately, a 9% precision on bending of light in this new test is somewhat less precise than the 0.0023% precision on the same parameter from the Cassini probe.