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LIGO Fails To Detect Gravity Waves

Posted by kdawson on from the listen-harder dept.

planckscale writes "Last weekend, LIGO (the Laser Interferometer Gravitational-Wave Observatory) did not detect gravitational radiation in association with a gamma ray burst (GRB). The non-detection was actually a valuable contribution, as it helped to distinguish between competing models for what powers GRBs. The detector is due to be upgraded this year for even more accurate measurements. The interferometer is constructed in such a way that it can detect a change in the lengths of the two arms relative to each other of less than a thousandth the diameter of an atomic nucleus."

5 of 357 comments (clear)

  1. As a matter of interest... by gnalre · · Score: 4, Interesting

    This is another failiure in the long history of trying to detect gravity waves.

    As a matter of interest what would be the consequences to modern physics if Gravity waves do not exist?

    --
    Choose your allies carefully, it is highly unlikely you will be held accountable for the actions of your enemies
    1. Re:As a matter of interest... by VernonNemitz · · Score: 5, Interesting

      Actually, ONE possible problem with the experiment has nothing to do with the sensitivity of the detector. See, there is a fundamental and unproved ASSUMPTION in Physics that gravity waves must travel at the speed of light, and therefore when a gamma-ray burst happens, we expect any gravity waves from the event to arrive at the same time as the gamma-ray photons. But if they don't have to travel at light-speed, then they can exist and be detectable, just not at the same time as the gamma rays.

  2. Re:Of couse, they could *both* have it wrong... by boot_img · · Score: 5, Interesting

    ... but I would call this simply "bad" science - You can't use one poorly-understood phenomenon to explore another. You are incorrect. Gravitational waves (the phenomenon) are a very clear and very well understood prediction of the theory of General Relativity. So I would say that this is as far from "bad" science as you can get. If, ultimately, gravitational waves are not detected by LIGO and its successors that would prove GR was incorrect. And that would be a huge scientific advance.
  3. An interesting question... by sapphire+wyvern · · Score: 4, Interesting

    I looked at the Wikipedia article about LIGO and noticed this interesting question in the discussion. No one has answered it there. Apparently it's from some forum somewhere. Maybe someone here can explain the solution to this "conundrum" for me?

    Just getting back to LIGO for a while (sorry if this isn't strictly on topic), I understand that two long laser beams, at 90 degrees to each other, split from one laser source originally by a semi-silvered mirror, are re-combined at a sensitive detector to see whether their wave forms are cancelling or reinforcing. A passing gravity wave will sequentially lengthen and shorten the wavelength of only one of these light beams because the space-time continuum is distorted in only the direction of travel of the gravity wave. This, it is assumed, will cause the interference of the two laser beams to vary also - causing a variation in the light level measured at the detector. I still don't see why LIGO will work because a gravity wave is indiscriminate in the way it distorts things.

    Everything is embedded in our 4-space, including the laser light waves lying along the direction taken by the gravity wave. As the gravity wave compresses and then dilates space-time, the LIGO tube and the laser beam within it will compress and dilate in perfect synchrony. Even the human observers' heads will compress and dilate as the gravity wave passes! The number of light waves per unit length of the LIGO tube (the laser wavelength) will appear unchanged because the actual physical length of the tube will shorten and lengthen as the light waves do, and as the eyeballs of the experimenters do too. If the waves of the re-united beams were re-inforcing peak-to-peak before the gravity wave arrived, they will remain peak-to-peak as the gravity wave passes through also. This alteration in the length of the tube, or arm, of the LIGO experiment, together with the variation in the wavelength of the laser beam, will be completely undetectable for that reason.

    It's not a case of the gravity waves being too weak to detect, their influence is universal within our frame of reference and therefore cannot be directly detected .. by definition! The above is the way I see the situation. But dozens of scientists have spent billions of dollars designing LIGO, so I have to conclude I'm completely incorrect in my reasoning. Can anyone tell me how you can measure a distortion of space-time (4-space) if you, and every tool you use to measure the distortion, including light, are part of the same space-time being distorted?

    I'd be fascinated to see what's wrong with the reasoning here!

  4. Re:Bummer by JohnFluxx · · Score: 4, Interesting

    He's talking about, for example, where we have observed two neutron stars are orbiting each other, and their orbiting speed is slowing down. If you say that it's because they are giving off 'gravity waves' and thus losing energy in that way, then the theory exactly matches the results.

    Personally I'd side with LIGO being wrong or not sensitive enough or something. At least until there's a bit more evidence.