Uncovering the Truth: Examining the Existence of Gravitational Waves

[Stingray]

It is obvious the article is Historical, the GW's predicted by Einstein in 1916?..the articles content deals with a peer review dispute.
I am not disputing the existence of GW's, but I do not think they will be detected (in forseeable future), for which reasons the Einstein-Rosen-Paradox must have a baring?
Something can exist, and still be beyond detection?

I don't understand your point. Yes, it was a peer review dispute, but Einstein later agreed (circuitously) that the referee was right.

On what basis are you claiming that gravitational waves won't be detected soon? And what is the Einstein-Rosen paradox?

Their result was only confusing before they realized that their chosen coordinate system was misleading. It's pretty easy to confuse yourself in GR with coordinate problems if you're not very careful. This was not as widely acknowledged then as it is today. People had little experience with recognizing and resolving these issues.

 

[Garth]

On what basis are you claiming that gravitational waves won't be detected soon?

As well as this being a discussion about the interpretation of theory, GWs have not yet been detected and, if this non-detection continues indefinitely, then that interpretation may have to be revised.

As an example this eprint was posted today on the physics ArXiv: Joint LIGO and TAMA300 Search for Gravitational Waves from Inspiralling Neutron Star Binaries

Yet again:

We find no evidence of any gravitational wave signals

Garth

 

[SpaceTiger]

Garth, that paper puts an upper limit of ~50 neutron star mergers per year in the Milky Way galaxy. Are you saying you would have expected it to be larger than that?

 

[Garth]

Garth, that paper puts an upper limit of ~50 neutron star mergers per year in the Milky Way galaxy. Are you saying you would have expected it to be larger than that?

I personally expect GWs to be eventually detected, however, after linking to an article describing Einstein's ambivalence over GWs, the OP question was "So do Gravitational Waves exist?" That question becomes more pertinent the longer their non-detection continues.

Now, as for that paper's expected limit for neutron star/BH mergers. If we, for the moment, accept that short GRBs are such mergers and they are detected about once a month, and they are relatively nearby, though not necessarily in the Milky Way, then we might expect ~ 10 neutron star mergers per year in the Milky Way galaxy. So I am not expecting it to be larger than ~50 , however the upper limit is now at last approaching the expected detection limit and the next few years should be interesting!

Of course, not all NS/BH mergers necessarily produce short GRBs, and there are other sources of GWs as well, so the expected GW detection rate is probably highter than this, but I have no expertise in this area.

Garth

 

[SpaceTiger]

I personally expect GWs to be eventually detected, however, after linking to an article describing Einstein's ambivalence over GWs, the OP question was "So do Gravitational Waves exist?" That question becomes more pertinent the longer their non-detection continues.

I think we're still in the stage where we would have been surprised if we had detected them. LIGO doesn't have the sensitivity to see most of the conventional gravitational wave sources, and those that it can see require a great deal of luck.

Now as for that paper's expected limit for neutron star/BH mergers. If we, for the moment, accept that short GRBs are such mergers and they are detected about once a month, and they are relatively nearby, though not necessarily in the Milky Way, then we might expect ~ 10 neutron star mergers per year in the Milky Way galaxy.

Our understanding of short GRBs is extremely crude and any failure to detect such a signal would almost certainly be due to a failure in those models, not in our theory of gravity. Given the high-quality data that came from PSR 1913+16, the only way you'll see astronomers/physicists seriously questioning the existence of gravitational waves is if we point our detectors at a source that we know is above our threshold of sensitivity and get no detection.

The only observations that tell us anything about gravitational waves have come out in favor of them. None of the direct detection experiments have been able to address GR, they've only been able to put limits on the frequency of certain astrophysical events.

 

[Garth]

Our understanding of short GRBs is extremely crude and any failure to detect such a signal would almost certainly be due to a failure in those models, not in our theory of gravity. Given the high-quality data that came from PSR 1913+16, the only way you'll see astronomers/physicists seriously questioning the existence of gravitational waves is if we point our detectors at a source that we know is above our threshold of sensitivity and get no detection.

Agreed - but when (how many more years) will our theshold of detection increase in sensitivity to below the predicted signal from known sources?

Garth

 

[Stingray]

Agreed - but when (how many more years) will our theshold of detection increase in sensitivity to below the predicted signal from known sources?
Garth

As I've stated in these forums several times, most people would be quite surprised if any of the current detectors found anything in the next few years.

Upgrades to LIGO are expected to start being built in 2008, and observations should start around 2013. These will increase the sensitivity by a factor of 10, which is expected to be sufficient to make a detection within a year or two (at worst). If nothing is found by then, people will start to worry.

 

[Garth]

As I've stated in these forums several times, most people would be quite surprised if any of the current detectors found anything in the next few years.
Upgrades to LIGO are expected to start being built in 2008, and observations should start around 2013. These will increase the sensitivity by a factor of 10, which is expected to be sufficient to make a detection within a year or two (at worst). If nothing is found by then, people will start to worry.

Thank you, that is what I wanted to know!

Garth