The Search for Gravitational Waves

Regardless of what will or will not be announced on Thursday, I thought it would be worth sharing this nice colloquium talk by Dr Alan Weinstein of Caltech about the search for gravitational waves, featuring the Laser Interferometric Gravitational-wave Observatory (LIGO). I’ve picked this not only because it’s a nice and comprehensive overview, but also that Professor Weinstein doesn’t call them gravity waves!



22 Responses to “The Search for Gravitational Waves”

  1. I’m currently reading “Gravity’s Ghost and Big Dog” by Henry Collins, about the GW experimental process. I don’t know if you came across Collins during your time at Cardiff. I would be interested to hear what you thought if you had. He seems to have written quite a bit about the GW community.

    • That should have been Harry Collins.

    • telescoper Says:

      Yes, I have met him. He’s a sociologist.

    • Big Dog? Reminds me of a book I read when I was about 10 or 12, From the Black Hole to the Infinite Universe. It was basically a popular-science book, but each chapter began with a science-fiction episode (related to the contents of the corresponding chapter). The protagonists, in a future world where insurance companies are the dominant factor in society, cruise the cosmos in their space ship Top Dog.

      It came out in 1974 and, you know, man, really has that early-1970s California vibe. Now where did I put my incense?

      Has anyone else read this?

      • It was called the Big Dog in part because the initial sky localization of that faked signal back in 2010 put it in Canis Major.

  2. Alan is also a pretty awesome person, beyond being a fantastic scientist.

  3. Thanks.

    Someone on Twitter had recommended this tutorial from your old haunt.

  4. Anton Garrett Says:

    49 hours to go…

  5. Lester Jenkins Says:

    Surprising the rumors are so specific considering how closed the analysis is supposed to be.

    • Anton Garrett Says:

      If you are on the team and you want the news out then you leak it to friends rather than tweet it yourself. Whether you should is an amusing discussion.

    • Anton Garrett Says:

      If you are on the team then you leak it to friends, of course; although whether you should is another matter.

  6. Maybe there is no discovery, but they want to discover who leaks and who doesn’t. So, each person in the team gets to hear a rumour specifying a certain date. This date then informs the boss who was indiscreet.

    The British royal family intentionally spread false rumours about the princes among their acquaintances. By seeing which appeared in the press, they knew whom they could trust and whom not.

    • Hehe… I was (am) considering this possibility as well. 😀 Sort of like a false signal injected to test the team’s ability to hold a secret.

  7. Is LIGO shielded from photons having the same frequencies as the gravitational waves to be measured?

    • And do you seriously think that a) this is a problem and b) you were the first to notice it? Really?

    • Anton Garrett Says:

      The graviton is spin-2 and can only be detected via quadrupole effects. LIGO is set to compensate for lower n-pole effects due to spin-1 particles.

      • I have read a lot about Ligo but I never read about how this compensation works. The thing is, in my theory, particles falling into a black holes (which is a five dimensional ring) will spiral around one side of the ring before merging with it. This should produce gravitational waves. The 2 dipoles from the black hole are suppressed because its oscillations are too small relative to us. But the momentum must be conserved, being reciprocal for the black hole and the particle, it’s total is near zero so we are left with two beams of photons in opposite direction and perpendicular to the spin for very specific reasons I won’t elaborate here, related to the fifth dimension. This is what is observed. My most constrained model limit the black hole spin between 0.5 and 1/squareroot(2) (about 0.707).

      • corrections:

        ‘The dipole from the black hole is suppressed’ not ‘the 2 dipoles’

        ‘ two beams of photons in opposite direction and perpendicular to the rotation’ not the spin

        My most constrained model limit the black hole spin between 0.5 and 0.707 in any case.

        My model is based on a deterministic Quantum theory, so the ring is real and the gravity is suppressed in the middle plane so photons can only be ejected from the inside at a perpendicular direction because gravity is not suppressed in the outside plane.

        The linear mass is the Planck mass divided by 2pi, a constant!

        Thus, a gas would produce a sharp beam while a star falling into the black hole would produce a more diffuse beam due to perturbations.

  8. If no, then I won’t be surprised to learn of a positive detection.

    Wavelength is approx.. 3 millions km: very difficult to shield!

    • 30 000 km not 3 million km.

      • Again, I’ve made a mistake… it is 3000 km…

        Only the earth could potentially shield it.

        It is impossible at this point to differentiate GW from photons…

        Seriously, gravitational waves are very difficult to merge with QM. That’s why we need the graviton. Photons are the way to go unless proved wrong.

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