Subaru/IPMU: Deepest Galaxy Map Finds Einstein's Theory Stands True

[bystander]

New Test by Deepest Galaxy Map Finds Einstein's Theory Stands True
Subaru Telescope | National Astronomical Observatory of Japan |
Kavli Institute for the Physics and Mathematics of the Universe | 2016 May 11

[c][attachment=0]fig1e[1].jpg[/attachment][/c][hr][/hr]

By using Fiber Multi-Object Spectrograph (FMOS) on the Subaru Telescope, an international team led by Japanese researchers has made a 3D map of 3000 galaxies 13 billion light years from Earth. Based on this comprehensive survey, the first of such a study at this great distance, the team was able to confirm that Einstein's general theory of relativity is still valid.

Since it was discovered in the late 1990s that the universe is expanding at an accelerated rate, scientists have been trying to explain why. The mysterious dark energy could be driving acceleration, or Einstein’s theory of general relativity, which says gravity warps space and time, could be breaking down.

To test Einstein’s theory, a team of researchers led by Kavli IPMU ... used FastSound Survey data on more than 3000 distant galaxies to analyze their velocities and clustering.

Their results indicated that even far into the universe, general relativity is valid, giving further support that the expansion of the universe could be explained by a cosmological constant, as proposed by Einstein in his theory of general relativity. ...

The Subaru FMOS galaxy redshift survey (FastSound).
IV. New constraint on gravity theory from redshift space distortions at z∼1.4 - Teppei Okumura et al

• Publications of the ASJ (online 26 Apr 2016) DOI: 10.1093/pasj/psw029
  arXiv.org > astro-ph > arXiv:1511.08083 > 25 Nov 2015 (v1), 25 Mar 2016 (v2)

[Ann]

Click to view full size image

Experimental results looking at the expansion of the universe, in comparison to that
predicted by Einstein’s theory of general relativity in green. (Credit: Okumura et al.)

I was a little bit confused by this graph. Yes, I realize that it is horribly hard to measure the expansion rate of the very early universe, but it seems to me that the results obtained by Okumara et al. don't agree all that well with previous results, or with Einstein's theory of general relativity.

Ann

[BMAONE23]

Interesting but kind of puzzling. According to the Planck spacecraft, the latest estimated age of the universe is 13.82B years. Assuming that light speed is constant in the confines of space and hasn't changed over time, shouldn't we only be able to see back as far as first light? The graphic supplied is depicting measured galactic distances of almost 14.5B LY. How could we see and measure something that is farther away than light could have traveled in a universe that is 13.8B years old?

[Markus Schwarz]

Interesting but kind of puzzling. According to the Planck spacecraft, the latest estimated age of the universe is 13.82B years. Assuming that light speed is constant in the confines of space and hasn't changed over time, shouldn't we only be able to see back as far as first light? The graphic supplied is depicting measured galactic distances of almost 14.5B LY. How could we see and measure something that is farther away than light could have traveled in a universe that is 13.8B years old?

You implicitly assume that spacetime is static, while in reality it is expanding. This means that time t, distance d, and speed v are no longer related by a simple d=v*t. Thus, the age of the universe is about 13.8By, while the diameter of the observable universe is about 93 Gly, see also Wikipedia on the size of the observable universe or have a look at this table.

[Markus Schwarz]

I was a little bit confused by this graph. Yes, I realize that it is horribly hard to measure the expansion rate of the very early universe, but it seems to me that the results obtained by Okumara et al. don't agree all that well with previous results, or with Einstein's theory of general relativity.

Ann

I agree that this is not a precision experiment. But the data point agrees with general relativity within the errors. If you have a look at Figure 17 and 18 of the publication you see that other theories of gravity strongly disagree with the new data point. Some theories seems to be in slightly better agreement, but keep in mind that other theories of gravities have more free parameters to tinker with.

[Ann]

I was a little bit confused by this graph. Yes, I realize that it is horribly hard to measure the expansion rate of the very early universe, but it seems to me that the results obtained by Okumara et al. don't agree all that well with previous results, or with Einstein's theory of general relativity.

Ann

I agree that this is not a precision experiment. But the data point agrees with general relativity within the errors. If you have a look at Figure 17 and 18 of the publication you see that other theories of gravity strongly disagree with the new data point. Some theories seems to be in slightly better agreement, but keep in mind that other theories of gravities have more free parameters to tinker with.

Thanks, Markus. I understand a little better now... I think.

Ann