Gravitational Wave Theory Takes Another Kick in the Teeth

Northern leg of the LIGO facility on the Hanford Reservation (LIGO)
Northern leg of the LIGO facility on the Hanford Reservation (LIGO)

Six years and nearly 400 million dollars later, the Laser Interferometer Gravitational-Wave Observatory (LIGO) still hasn’t turned up the evidence for gravitational waves. Gravitational waves are predicted by fundamental Einstein general relativity theories, but we haven’t been able to detect them. Is it because the first generation laser interferometers are not sensitive enough? Is it because LIGO needs more time to see through the cosmic noise to root out the gravitational wave signature? This is a deeply worrying non-development for physicists as a null result means that something isn’t quite right. We are certain (in theory) that these waves should be rippling through space-time (after all, massive objects are colliding and exploding all the time throughout the Universe), but if we can’t detect the things in our own cosmic back yard, something must be awry. In a recent publication, LIGO scientists have discussed the lack of evidence for gravitational waves, but remain upbeat that they can still be found…

I find myself getting a little uncomfortable when discussing laser interferometers in the search for gravitational waves. On the one hand, the physicists involved are doing some cutting-edge science to search for one of the most observationally difficult things to find; and if they do find a gravitational wave signature it will provide the direct evidence for one of Einstein’s critical general relativity predictions. On the other hand, a huge amount of money has been ploughed into the LIGO project, and despite all the optimistic predictions, it has still generated few results. Unfortunately, the latter is persisting in a new publication from the LIGO scientists.

Using data from three years ago, observational results were combined from the US LIGO detectors and the German GEO600. Looking at a month-period from February to March 2005, the analysis is not good news; no gravitational waves were found during this international effort (combining the US and German detectors would have seriously increased the sensitivity of the results, so this is very bad). The team even go as far to say “No candidate gravitational wave signals have been identified.” Oh dear.

As pointed out by the Physics arXiv Blog, this may just have been bad luck. Perhaps there were no black hole collisions, supernovae or spinning lumpy neutron stars that month? Possibly. It seems more likely that the instrumentation isn’t sensitive enough or something isn’t quite right with the theory. These two options would be terrible news for the LIGO team and other laser interferometer groups around the world.

However, many would argue that this is only the first-generation of laser interferometers and that we are learning so much simply by using an developing the technology. Unfortunately, science funding doesn’t work like that. Try asking for the next half-billion dollars from the NSF when the first $400 million experiment didn’t produce results. I can guarantee there will be little enthusiasm for a gen-2 LIGO proposal…

Still, we have to remain optimistic, after all, six years isn’t very long. The longer LIGO takes data, the better refined the results become. Perhaps LIGO scientists need to think outside the box on this one… why do I get the feeling that the results from LIGO are not as benign as we think, there could be another effect that gravitational waves have on the local Universe we haven’t taken into account. Oddly, this reminds me of a quote in one of my favourite films, Indiana Jones: Raiders of the Lost Ark:

Indiana: Balloq’s medallion only had writing on one side? You sure about that?
Sallah: Positive!
Indiana: Balloq’s staff is too long.
Indiana, Sallah: They’re digging in the wrong place!

Perhaps the LIGO physicists are also digging in the wrong place

Source: Physics arXiv Blog

18 thoughts on “Gravitational Wave Theory Takes Another Kick in the Teeth”

  1. Not shocking… (Pardon the pun, if you know some of my interests.)

    I’ve already mentioned elsewhere that LIGO and the European equivalents have thus far had several failures. Glad it’s not just me that sees it. Theoretically, they should have seen SOMETHING by now. Especially after a full year of continuous observation in S5 (the 5th science taking session)… I’ll see if I can find the references I’d dug up once upon a time.

    Not promising. Especially since several of the articles have said that according to theory the LIGO instruments ARE powerful enough to have detected something, had something been there. The continuing NULL results must thus be troubling for the standard model theories that more-or-less require them as “proof.”

    How many more NULL result are allowed before gravity waves are simply ruled out. We can’t keep simply dumping more and more money into something that’s not producing results. Or rather, something that keeps producing NULL results.

    NSF has already dedicated money to upgrading LIGO’s hardware to make it considerably more sensitive. If it continues turning out NULL results after the upgrade (is the upgrade already completed?), can we call gravitational waves busted?

    Consider, that we should probably be routinely bombarded by gravitational waves from various parts of the sky on a regular basis. If we can’t detect ANY of them, what does that tell us? Are the detectors which are supposed to be plentifully powerful NOT powerful enough, in which case the theory telling us how strong they must be and how strong the GWs are is wrong. Or does it simply mean that there ARE NOT gravity waves, period? And what would THAT do to theory? Scary thought for most mainstreamers, I’d guess…

    To put it succinctly, how do we tell the difference between an “interesting” null result an uninteresting null result and a “falsifying” null result?


  2. Ahh, found it. Discussed the prior null results on another forum.

    (LIGO’s “Null Results,” Interesting or Not?)

    Discusses the various “failures to detect” or “NULL results.” I just wonder how many more they can pop out before the theory itself starts to falter? If gravitational waves go down, what’s next to fall? Neutron stars, colliding black holes? Black holes in general? Probably the latter.

    (The Black Hole, the Big Bang, and Modern Physics)


  3. Hi jeo

    Unexpected “results” are good, but non-results are harder, much harder, to interpret. Maybe GR really doesn’t predict gravity waves and someone messed up doing the equations? Maybe LIGO and kin are too small? Maybe GWs turn into something different in higher dimensions and thus can’t be observed… etc etc. That’s what a non-result can mean – anything – and that’s why it’s the last thing the scientists want.

  4. I think researching things like this is very important. I mean, by learning new things about one particular topic, we may in turn, be helping human kind in another way that we don’t even realize yet. Too bad it takes so much money!

  5. Here elaborates the matter not only extensively but also detailly .I support the write's unique point.It is useful and benefit to your daily life.You can go those sits to know more relate things.They are strongly recommended by friends.Personally

  6. Here elaborates the matter not only extensively but also detailly .I support the write's unique point.It is useful and benefit to your daily life.You can go those sits to know more relate things.They are strongly recommended by friends.Personally

  7. Thanks a landlord it! I acquired yet some insight. Life is so colorful, we should be able to live in, such as Korea and honor the planet. Human life is like rivers, slowly flowing, flowing rivers, flowing through the snow, flows through the prairie and ultimately into the sea, return to the embrace of nature, start a new reincarnation. Allow us to feel the meaning of life will come only to those you have those memories!

  8. Indeed none of the predictions people claim they proove the GR are proper to GR. A massive star that is very very massive, has a gravitationnal field that creates a force that overtakes other forces GR or not, so There must be collapse. The fact is the same with gravitationnal waves, none of the alternative theory don’t predict gravitationnal waves, if you have a field, then you have waves, because of special relativity, information about source position takes a finite time to reach another position. Now you should explain how binary stars collide and loose their orbit.

  9. Since gravity appears weak to our observations, and only inferably observable between large bodies of masses, it is not surprising that the equipment we are using to detect gravitational waves is simply not sensitive enough to detect any waves.

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