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Gravitational Waves

  1. Jun 6, 2005 #1

    Garth

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    What do members think of this paper?
    It reads as 'crackpot' to me, claiming as it does that gravitational waves cannot exist, however, it cites as supporting evidence the fact that GWs have not been detected yet.

    Is this a valid point? As detection sensitivities improve, with new detectors and time, should GWs already have been detected?

    Garth
     
    Last edited: Jun 6, 2005
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  3. Jun 6, 2005 #2

    pervect

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    The paper strikes me as "crackpot", too. The author would have to address the issue of the supposed errors in numerous previous papers and numerous textbooks which do show that gravitational waves follow from Einstein's field equations to have any chance of convicing me.

    The pseudo-erudition of his use of Latin phrases doesn't particularly impress me either.

    While I haven't studied the matter closely, my opinion is that the current results are not any cause for alarm - it would take a fair amount of luck to detect gravitational waves. Consider the quote from the following paper by the Ligo group:

    http://arxiv.org/PS_cache/gr-qc/pdf/0505/0505041.pdf

    So it appears that the non-detection of neutron star inspirals is not a cause for concern, at least in the opinion of the people doing the research. The question remains whether there are other gravitational events that we "should be" detecting at the current sensitivity levels.
     
  4. Jun 6, 2005 #3

    Garth

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    I agree, however there is a nagging doubt.

    When funding for a N $million instrument, LIGO, LISA, LHC, SETI or whatever, is proposed it is stressed that the money is not going to be wasted because there is a very reasonable chance that whatever is the object of the experiment, GWs, Higgs bosons, ETs, will be detected. However, after five years or so of negative results we see lots of papers explaining "that a detection by the present search would be highly surprising".

    Am I being over sceptical?
    Garth
     
  5. Jun 6, 2005 #4

    wolram

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    Garth, as an uneducated guess, i bet a pound to a penny that these waves
    will not be found, this is based on my logic and nothing else.
     
  6. Jun 6, 2005 #5

    Stingray

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    I was just starting to get involved in GR 4-5 years ago. The sentiments back then were exactly the same. Nobody expected any real science (as opposed to engineering) to come out of the current version of LIGO.
     
  7. Jun 6, 2005 #6

    Garth

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    In which case the question is; "When will we see "any real science" to come from the GW detectors?

    Garth
     
  8. Jun 6, 2005 #7

    turbo

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    No, you are not being overly skeptical - backpedaling over expensive projects with no positive result is all-too-common and your attitude shows a healthy level of skepticism.

    There are alternative views (as you are well aware). If my ZPE model of gravitation is accurate, we will never detect gravitational waves from any distant source. In my model gravitation arises as local effect - the interaction of matter with the LOCAL polarized fields of the quantum vacuum. The polarization of the local ZPE fields will never be flipped by a BH inspiral in M31, so detection of such a gravitational "wave" is a non-starter.
     
  9. Jun 6, 2005 #8

    Stingray

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    We should see things from LIGO once its upgrades are completed, and all the bugs are worked out. Work isn't planned to start on this for another 3-5 years (I don't remember exactly).

    I think everything should be done within 10 years. If it works the way it is designed to, we should start seeing things within a few months (at most). As a disclaimer, none of these numbers should be taken too seriously. Although there are good estimates out there, I'm not an expert. My memory could easily be off a bit.

    Anyway, for those who still think this is a big conspiracy theory, you can go look up old papers on the subject. Everything is freely available.
     
  10. Jun 6, 2005 #9

    turbo

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    There are few people who would characterize this as a conspiracy theory - it's pure sociology. Bureaucracies are relentlessly self-perpetuating, and scientific establishments are no exception. There are proposals to be made, grant money to be courted, and politicians to schmooze. If the project does not yield the expected results, tell the money-men that your project has supplied scientifically-important constraints on the standard model and apply for more money for an expanded project.
     
  11. Jun 6, 2005 #10

    Stingray

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    You're right that people have a tendency to do that. My point was that it's easy enough for anyone who's really interested to look up what the expectations were 10 or 15 years ago. Even in the late 80's, I think it was understood that LIGO would have to go through a couple of iterations to have a reasonable chance of seeing anything.

    I should say that there was some over-optimism from the data analysis side of things. Most people assumed that sufficiently efficient analysis techniques could be figured out within a couple of years. This was not correct, and there are still several unresolved issues in this area.
     
  12. Jun 6, 2005 #11

    turbo

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    Yes, and we've got to realize that the definition of an "event" in a new field is predicated on the expectations and assumptions of the model in vogue when the project is proposed. The definitions of an "event" must necessarily change as the field evolves, and the project matures and engineering constraints arise. This is not discouraging to the bureaucrats, though. As an example, administators of particle physics projects propose colliders capable of higher and higher energies, etc. IIR, the Higgs boson was expected to reveal itself at about 85 Gev, and has yet remained elusive at energies of 115 Gev. If the new generation of colliders don't produce the Higgs particle, there will not be a re-evaluation of the standard model, but instead we can expect a flood of proposals to build even higher-energy colliders. It's the nature of the beast.
     
  13. Jun 9, 2005 #12

    SpaceTiger

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    If Advanced LIGO and LISA both fail to detect gravitational waves (and work properly), then we'll have a theoretical crisis on our hands. The current version of LIGO would have to be "lucky" to catch anything (like a black hole merger), so the non-detection has no theoretical significance as of yet.
     
  14. Jun 10, 2005 #13

    Chronos

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    I'm pretty confident LIGO will produce results. The sensitivity is just not quite there yet. The indirect evidence favoring gravitational radiation is strong.
     
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