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Physicists Gear Up To Catch a Gravitational Wave

Posted by Soulskill on from the surf's-up dept.

sciencehabit writes: A patch of woodland just north of Livingston, Louisiana, population 1893, isn't the first place you'd go looking for a breakthrough in physics. Yet it is here that physicists may fulfill perhaps the most spectacular prediction of Albert Einstein's theory of gravity, or general relativity. Structures here house the Laser Interferometer Gravitational-Wave Observatory (LIGO), an ultrasensitive instrument that may soon detect ripples in space and time set off when neutron stars or black holes merge. Einstein himself predicted the existence of such gravitational waves nearly a century ago. But only now is the quest to detect them coming to a culmination. Physicists are finishing a $205 million rebuild of the detectors, known as Advanced LIGO, which should make them 10 times more sensitive and, they say, virtually ensure a detection.

88 of 127 comments (clear)

  1. Cheaper method by ArcadeMan · · Score: 4, Funny

    Physicists are finishing a $205 million rebuild of the detectors, known as Advanced LIGO, which should make them 10 times more sensitive and, they say, virtually ensure a detection.

    A cheaper way of virtually ensuring detection is to do the experiment in a simulation.

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    1. Re:Cheaper method by MightyMartian · · Score: 4, Insightful

      Because climatologists never use field data...

      Oh wait, they do, that must me you're either a liar or a retard.

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    2. Re:Cheaper method by Dimwit · · Score: 5, Funny

      Little do they know, they ARE doing the experiment in a simulation.

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    3. Re:Cheaper method by Anonymous Coward · · Score: 1

      Belief in a theory because the mathematics are beautiful is not a substitute for careful experiments. The physics graveyard contains the bones of many beautiful elegant theories. That being said I fully expect gravitational waves to be discovered.

    4. Re:Cheaper method by MightyMartian · · Score: 4, Insightful

      Fortunatley, they don't, and you're still either a liar or a retard. One thing is for sure, you're beneath contempt.

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    5. Re:Cheaper method by ShanghaiBill · · Score: 5, Interesting

      That being said I fully expect gravitational waves to be discovered.

      I am not so sure. There have been other experiments that should have detected them, but didn't. If this experiment also comes up empty, then physics may be facing another Michelson–Morley moment.

    6. Re:Cheaper method by MightyMartian · · Score: 4, Insightful

      Climatologists get paid whether the world is warming or cooling, and it's not as if the politicians are doing much in regards to what the scientists are saying.

      Besides, there's a lot more profit in being a mouthpiece for the fossil fuel industry.

      But hey, maybe you can hire Ben Stein to narrate a documentary detailing how all the biolo... er climatologists are in an evil cabal to hide the truth.

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    7. Re:Cheaper method by Fire_Wraith · · Score: 3, Insightful

      If you're a climate scientist who says there's no Anthropogenic Climate Change, there are lots of Fossil Fuel groups that will shower you with money - much like Tobacco companies would to any Scientists that said Smoking doesn't cause Cancer.

      And yet, it's the ones who report the opposite that get accused of being on the take, when their findings match what everyone else in their field (except those taking money from the fossil fuel industry) almost universally report.

    8. Re: Cheaper method by hAckz0r · · Score: 1

      You are right. The need for Dark Matter and Dark Energy is indicative of the level of their error. Their first problem is the math describes the motion of gravitation, not the process. Their second problem, because of the first, they are ignoring the first law of thermodynamics. The only way to reconcile both problems is to step back for a reexamination the actual evidence. All it takes is a thermodynamic definition of a photon and the gravitational process emerges as a physical property of spacetime itself. No Dark Matter, no Dark Energy required, an unfortunately for these scientsts no measurable gravity waves either.

    9. Re:Cheaper method by aaronb1138 · · Score: 1

      Well, all of the other LIGO detectors have been worthless due to errant signal sources like UPS trucks and natural tremors. I love physics and good experiments, but the LIGO model is a bad one unless you put it on the Antarctic or moon.

    10. Re:Cheaper method by sg_oneill · · Score: 1

      If you're a climate scientist who says there's no Anthropogenic Climate Change, there are lots of Fossil Fuel groups that will shower you with money - much like Tobacco companies would to any Scientists that said Smoking doesn't cause Cancer.

      And predictably its often the very same "scientists" who where tobacco "experts" in the 80s saying that tobacco is harmless who now are "atmospheric scientists" claiming that CO2 violates physics and doesn't heat up when exposed to infrared light.

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    11. Re:Cheaper method by ivano · · Score: 1

      With all that time to spare he could have sent a link to a peer reviewed paper on it. I wonder why he didn't?

    12. Re:Cheaper method by ivano · · Score: 1

      What is the statistical difference between the models and reality? Again, any peer reviewed papers on this?

    13. Re:Cheaper method by MightyMartian · · Score: 1

      Wrist you believe and what actually is at two different things. There is considerable prestige in overthrowing older views. But they are not overthrown by taking money from fossil fuel companies and writing pieces in the WSJ.

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    14. Re:Cheaper method by delt0r · · Score: 1

      Which would be pretty fantastic!

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    15. Re: Cheaper method by delt0r · · Score: 1

      Oh god.. not this kind of crap. You know this solves and explains exactly *nothing* that we have already observed right.

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    16. Re:Cheaper method by eric_harris_76 · · Score: 1

      Some would say String Theory fits that description. Lack of falsifiability, and stuff like that. But the math shore is purty.

      --
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    17. Re:Cheaper method by HuguesT · · Score: 1

      Exactly, whereas somehow the fossil fuel shills are seen by some as the good guys. This may be because somehow no one want to own up to the fact that they are responsible for some ills of the world. Not me with my little car !

  2. Hmmm .... by gstoddart · · Score: 2

    So can anybody better versed in the physics fill this in a little: "an ultrasensitive instrument that may soon detect ripples in space and time set off when neutron stars or black holes merge".

    If the machine goes ping, we infer the machine is working perfectly, and somewhere a neutron star or black hole has merged? But you have no independent confirmation other than the machine going ping?

    So, set the damned thing to go ping, and claim you've found gravitational waves ... profit!!!

    Seriously, I'm confused. Surely there has to be some other way to confirm the machine works than having it tell you it worked.

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    Lost at C:>. Found at C.
    1. Re:Hmmm .... by Anonymous Coward · · Score: 5, Informative

      There *is* a second detector (a third even!) The second main detector is in eastern Washington state. Both will have to go ping before you accept any result.

    2. Re:Hmmm .... by Dunbal · · Score: 2

      You mean like when an electric tester lets you know there's electricity by turning on a little light? Yeah it could be more simple - lick your fingers and grab this wire in that hand and this other wire in...

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    3. Re:Hmmm .... by Baloroth · · Score: 3, Insightful

      Like what? It's designed to detect gravitational waves. It's not designed to detect not-gravitational waves. Since we can't produce artificial gravitational waves (the detector would be almost pointless if we could, since it's meant to prove the existence of gravitational waves), we can't use a known test to confirm it's detecting gravitational waves and only gravitational waves, but since all our theory and all our observation says it should be detecting them and only them, it's fairly safe to assume it's actually doing so (assuming no systematic errors: a large assumption, but not an unreasonable one if everyone involved did their job). In fact, if what it detects isn't gravitational waves, it's almost more interesting, because that means it's detecting something else which isn't accounted for in our theory. If it detects nothing at all, well, that too would be interesting, since (again) our theory says it should. Either way, interesting.

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    4. Re:Hmmm .... by Anonymous Coward · · Score: 4, Informative

      I toured the LIGO in Eastern WA (which is a twin if this, but the article apparently doesn't know it exists). Basically they have two long tubes (2 miles each I think) at right angles. A laser is shined down them and bounced back and forth as much as they can to increase the effective length. Lasers are combined again and they can see by an interference pattern if one arm of the experiment gets shorter or longer than the other, which is what is theorized to happen when a gravity wave passes through.

      A couple of years ago I think they were down to 10^-25m sensitivity, which is pretty amazing to me. They could tell when a truck rolled down the highway 10 miles away, when the hydroelectric dams in the state open their spillways, and when there are big waves from a storm on the coast (200 miles away).

    5. Re:Hmmm .... by Hartree · · Score: 5, Informative

      There are two more detectors at the Hanford Washington site. A primary one like at Livingston, and a secondary one that's half the length.

      Also, there is an European experiment in Italy, called Virgo. It's currently being upgraded to similar sensitivity to the other 3.

      When they are all working, it will allow the detection to not only be verified, but the time of the events at each detector will let them triangulate the location the wave originated from.

      We're pretty darn sure of gravitational waves, as a Nobel prize was awarded in 1993 for showing that the slowing of a binary pulsar was just the right amount to account for the gravitational waves it would generate.

      These detectors will let us do gravitational wave astronomy much like we do with light and radio waves now.

      The huge news would be if they get all of them working with their maximum sensitivity and didn't detect anything. That would mean something was very wrong with their assumptions.

    6. Re:Hmmm .... by Kjella · · Score: 1

      Well somebody has to be the first at discovering something before somebody else can confirm it. And yes, in human years it might take a while to build another billion dollar project to do that. Science works on incomplete information, otherwise there wouldn't be anything to do science on. Has anybody independently verified the Higgs boson yet? All the exoplanets discovered recently? Probably not. That's always how it will be at the leading edge of science.

      --
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    7. Re:Hmmm .... by wonkey_monkey · · Score: 1

      Surely there has to be some other way to confirm the machine works than having it tell you it worked.

      Yes, by building it such in a way that the only explanation for it going "ping" is that it has detected a gravitational wave.

      Not that it will just go "ping," in any case. It's not like the LHC just went "ping" when they were looking for the Higgs. It returned a huge amount of data which had to be processed, at the end of which the conclusion was, to 99.9999% certainty or whatever it was, that the data could only be explained by a Higgs boson.

      There are also, apparently, two other detectors at other locations to confirm LIGO "pings."

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    8. Re:Hmmm .... by jfengel · · Score: 5, Informative

      LIGO works by measuring the distance between two tracks set at right angles. A passing gravitational wave would momentarily change the length of one leg or the other, or both, in characteristic ways.

      It measures the distance with a laser beam. It splits the beam, and sends them down the two tracks. They bounce off mirrors, and when they return, they interfere. Changes in the length will change the interference. That means that they can detect changes at distances on the order of a single wavelength of light.

      That's an interferometer, the I in LIGO. At its core, it's the same thing that Michaelson and Morley used to look for aether, and failed to find it. The trick is that this has to be even more sensitive, because the expected changes are even smaller and the contraption itself is much bigger (4 km, versus a few meters). They have to exclude all kinds of potential interference, from passing trucks to earthquakes.

      I suppose it may well go "ping" when it spots a gravitational wave, and they'll end up comparing it to other experiments. But they'll get more than a ping; they'll get a signal of the changing lengths that they can use to map the size of the wave, and even a hint of its direction.

    9. Re:Hmmm .... by MouseTheLuckyDog · · Score: 2

      I believe the OP is asking, since the deterctor only returns one bit of information, how do we know that it is a gravitational wave and not an Aras freighter passing by the solar system.

    10. Re:Hmmm .... by Wormholio · · Score: 4, Informative

      There are two more detectors at the Hanford Washington site.

      Actually, there is now only one detector at Hanford, the full length H1. The half length H2 interferometer was discontinued as part of the upgrade.

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    11. Re:Hmmm .... by tylerni7 · · Score: 1

      You're assuming the machine simply goes "ping". It will actually return data that would be post processed and then show characteristics of gravitational waves.

      In some (very loose) sense it's like the search for the Higgs Boson. We don't have a machine that says "yeah I saw a Higgs Boson, turning off now!". It returns a bunch of data that gets analyzed and might show characteristics we expect.

      In order to know it is working, we would compare the data it finds to mathematical models of what a black hole merger or something would look like.

    12. Re:Hmmm .... by Maury+Markowitz · · Score: 4, Insightful

      > These detectors will let us do gravitational wave astronomy much like we do with light and radio waves now.

      Mmmm, more like neutrino I'd say. You can't point your GWD at an object.

    13. Re:Hmmm .... by GNious · · Score: 1

      Purely curious: How often do "neutron stars or black holes merge." ?

      Basically, if I understood correctly, these devices test for a specific output of a fairly specific type of event; a type of event that is outside of our ability to cause, or to accurately predict(?).

      So, to verify that they work, and that the theory is sound, we turn them on and wait some time until they all "go ping" ?

      Again, merely being curious, since I'm thinking I'm missing something ....

    14. Re:Hmmm .... by Anonymous Coward · · Score: 4, Interesting

      Yes, they are amazingly sensitive seismometers. However, I don't think they'll ever detect gravitational waves. Physcists are divided over whether the waves can be detected by the devices so far created. They rely on special and general relativity to not cancel each other out when it comes to compressing the wavelenghts of light over a long distince. The small signal strenght combined with noise combined with nearly complete cancellation probably dooms the experiment from the start.

    15. Re:Hmmm .... by Hartree · · Score: 2

      Thanks for pointing it out. My info was a bit old.

      Looks like they put components of H2 in storage and are thinking about using it for LIGO-India. I'd heard of the LIGO-India idea, but hadn't known it would use some of Hanford's equipment.

      Another detector at a long distance from the others would greatly improve the ability to localize the source. Let's hope they can get it built and not just have it remain a proposal.

    16. Re:Hmmm .... by gstoddart · · Score: 1

      but since all our theory and all our observation says it should be detecting them and only them, it's fairly safe to assume it's actually doing so

      So, build me a fucking god detector. And when it goes off, I'm going to call bullshit like I'm calling here.

      Look, I'm no physicist ... but surely someone can explain how a machine that goes "ping" is proof positive that it has detected the thing it claims to be detecting, no?

      It's clearly something glaringly obvious that I'm too dense to understand ... but the mere fact that a machine goes "ping" doesn't mean it worked, or that it proved anything. It means people invested in saying "see, it went ping, therefore it worked" will be happy ... but the rest of us aren't sure how.

      So, a big giant expensive machine goes ping ... and the only plausible explanation, because we have great theories and everybody did their part ... is gravitational waves?

      I'm aware I'm not qualified to refute that fancy physics, but it seems like there's a step in there that could use some dumbing down for the rest of us.

      Because, let's face it, with a simple light switch, I can build you a bullshit detector. It's demonstrating that it actually worked, instead of just being a light switch, which is the tricky part. ;-)

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    17. Re:Hmmm .... by Hartree · · Score: 1

      True. Its more like neutrino astronomy in that respect. But fewer people know about that (and I couldn't come up with a good car analogy to make it Slashdot compatible. ;) ).

      Assuming we detect them, being able to do spectroscopy (frequency measurements) and intensity measurements over extended periods to determine rise and fall times of events should be a powerful tool.

    18. Re:Hmmm .... by Anonymous Coward · · Score: 1

      I don't know if you intended or not, but your post might be misleading to most that don't know the state of neutrino astronomy. A subset of both neutrino and gravity wave detectors are able to measure the direction of incoming neutrinos/gravity waves. In some ways, they are even more advanced than optical astronomy because they are like a very wide field telescope (although with crappy resolution), although radio astronomy is at least building more wide field arrays these days. But the result is you get projects like IceCube labeled a neutrino telescope and not just detector because of the ability to look for point sources in the sky.

    19. Re:Hmmm .... by Anonymous Coward · · Score: 2, Informative

      since the deterctor only returns one bit of information

      Except it doesn't return one bit of information. It returns a spectrum and relative phase of oscillation measurements, for each of two directions, and again for each of two directions at a different site. Not to mention all of the information associated with calibrating and configuring the device. GR makes predictions about how gravity waves would interact with the two arms and two sites. Calibration and analysis of the construction and background determine a noise floor.

    20. Re:Hmmm .... by gstoddart · · Score: 1

      The machine doesn't just go ping. It provides information about frequency, phase, polarization, and time of flight between two points.

      LOL ... Temba, with his arms open!

      OK, this is really big science ... and I just need a few more small words ...

      We have two small widgets a known distance apart, these widgets are essentially fixed in place, but will wobble when acted upon by ... well, obviously gravity waves.

      Since there's nothing big enough to make two things that far apart wobble at the same time (short of something very kinetic, which we'd measure through several other means) ... .. we infer that we have measured the passage of the only phenomenon which could make out widgets wobble? Shit.

      So basically a long baseline widget wobbler which weighs waves of gravity. (Assuming of course the theory is right, the engineering is right, and these events happen often enough to measure.)

      That's some wacky science right there. Still not sure I got it even close.

      --
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    21. Re:Hmmm .... by budgenator · · Score: 1

      I just can't wrap my head around how LIGO works, the gravity waves ripple spacetime, so there is no frame of reference that I can see. Seems to me that the length of the arms would only change from an outside frame of reference.

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    22. Re:Hmmm .... by Anonymous Coward · · Score: 1

      Since there's nothing big enough to make two things that far apart wobble at the same time (short of something very kinetic, which we'd measure through several other means) ... .. we infer that we have measured the passage of the only phenomenon which could make out widgets wobble?

      Wiggle in a specific way, in a certain anti-correlated way between the two arms, with a certain delay between the two locations, and various predictions about the frequencies involved. And even with the physicist in the loop, it is still not a "yes" "no" answer that comes out, but measurements with error bars like most of physics.

    23. Re:Hmmm .... by Neil+Boekend · · Score: 2

      How often do "neutron stars or black holes merge." ?

      Once per pair, give or take.

      --
      Well, I might have a way, but it only works on a semi spherical planet in a vacuum.
    24. Re:Hmmm .... by Anonymous Coward · · Score: 1

      The GP's post seemed perfectly clear to me. They said "You can't point your GWD at an object.". An optical or radio telescope, you point at an object to learn more about it. A neutrino detector or gravitational wave detector, you see the whole sky at once instead.

    25. Re:Hmmm .... by rHBa · · Score: 1
      In Europe we're starting to move our GW detection into space with a Laser Interferometric Space Antenna (Lisa). To start with:

      ...Pathfinder's job is to prove the metrology.

      To do this, it will try to put two small gold-platinum blocks into a perfect free-fall and then track their relative movement using lasers.

      The intention is to get these blocks following a line that is defined only by gravity. To do that requires that all other forces that might interfere with the demonstration are removed.

      This means, for example, carefully controlling the influence of temperatures and magnetic fields. Even the vacuum state will introduce "noise" into the system if some residual gas molecules are allowed to collide with the blocks.

      The experiment has been designed such that disturbances to the blocks as small as just a few picometres should be noticed. One picometre is a small fraction of the width of a hydrogen atom.

    26. Re:Hmmm .... by bluegutang · · Score: 1

      Why not do the experiment in outer space? There are essentially no vibrations there. If the tubes were sufficiently thin and light, they could be affordably launched and then fit together in low earth orbit, and the experiment done there.

    27. Re:Hmmm .... by Hartree · · Score: 1

      If it shortened all dimensions equally and at the same time everywhere, it would be difficult. But you're looking for a difference in shortening (or lengthening) of one arm of the detector (or the test masses in that arm) relative to the other.

      It's a bit waves on the surface of a pond. Sometimes, they expand equally in all directions and form a circular pattern. Sometimes they are different in different directions. This can detect that difference.

      Even if the wave is symmetric in all directions, the squeezing/stretching can reach the arms of the detector at different times, just like the points on a circular ripple will reach the short at different times.

      Now, of course this is assuming that the waves travel at a certain finite speed (the speed of light as far as we know). If they traveled instantly so the change was everywhere all at once, things would be different.

      But, we have pretty solid reasons to believe that they don't travel instantly: That Nobel prize in 1993, I mentioned for example. The amount of energy lost in gravity waves was that of a traveling wave of finite speed, not something that traveled instantly.

    28. Re:Hmmm .... by Steve+Hamlin · · Score: 1

      That seems similar to something I just read about earlier this week: a ring laser gyroscope, which has replaced gimbal-mounted mechanically-spinning gryroscope for inertial navigation. It splits a laser beam into running in opposite directions around a path, then checks the interference patterns of the recombined pair. Due to the Sagnac effect, the interference pattern shifts upon movement - as I understand it, as the measurement point moves, each laser beam must travel a different distance than its pair, which results in a changing interference pattern which can be translated into "this device has moved X amount". Amazing - humanity is so freakin' smart.

    29. Re:Hmmm .... by HuguesT · · Score: 1

      In other words, it requires GRT to be correct. Which is precisely the point.

      The idea of the experiment is described in Misner et al (Gravitation, Misner/Thorne/Wheeler), and a comprehensive explanation of the LIGO experiment is given here, in this Caltech course. But feel free to disprove Kip Thorne and all the others professional physicists who have been working on this experiment for decades, by all means.

    30. Re:Hmmm .... by HuguesT · · Score: 1

      Short answer: no.

      Longer answer: figure 37.3, page 1014 of "Gravitation", by Misner, Thorne & Wheeler (classical text on general relativity).

      Long answer: this thesis..

  3. Virtually ensured? by MetalliQaZ · · Score: 1

    I would be very excited to read about the detection of gravity waves. But man, talk about a setup for disappointment. I wouldn't use that kind of language with the theoretical stuff being in the state that it is.

    --
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  4. Advanced Lego? by g0bshiTe · · Score: 1

    Is this a windup?

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  5. What On Earth Is Wrong With Gravity? by certsoft · · Score: 2

    They've been working on that a long time. Brian Cox visited there in a 2008 episode of BBC Horizon. I'm sure you can find a video on-line.

    http://www.bbc.co.uk/sn/tvradio/programmes/horizon/broadband/tx/gravity/

  6. Catch a Gravitational Wave by TFlan91 · · Score: 2

    Surfs up brah

    1. Re:Catch a Gravitational Wave by Ardipithecus · · Score: 1

      ...You'll be sitting on top of the world

  7. Re:Population? by xxxJonBoyxxx · · Score: 1

    >> patch of woodland just north of Livingston, Louisiana

    The most annoying part of the introduction was the fact that it made it sound like this was going on in somebody's still, rather than a highly funded research project run through nearby LSU. Also it's partial due to work in California:

    >> Key design elements of LIGO came from Ronald Drever, project director at Caltech from 1979 to 1987, who, Thorne says, “has to be recognized as one of the fathers of the LIGO idea."

  8. Re:Everybody gear up by Anonymous Coward · · Score: 1

    I have a cloaca, you presumptuous clod.

  9. Where is the joke? by thebes · · Score: 2

    I was waiting for a joke containing "your momma so fat" and "gravitational waves"...I leave here disappointed

    1. Re:Where is the joke? by Anonymous Coward · · Score: 3, Funny

      Yo momma's so fat, she emits Hawking radiation.

    2. Re:Where is the joke? by Anonymous Coward · · Score: 1

      String Theory predicts that the Universe has 11 dimensions. Three are normal spatial dimensions. The other eight are for your mom.

    3. Re:Where is the joke? by ShanghaiBill · · Score: 1

      Yo momma so fat, she got her own event horizon.

    4. Re:Where is the joke? by Neil+Boekend · · Score: 1

      Yo parents so fat, when you were conceived they emitted gravitational waves detectable with a hardware store laser distance meter.

      --
      Well, I might have a way, but it only works on a semi spherical planet in a vacuum.
  10. So was it by rossdee · · Score: 1

    A stellar collision in a galaxy far, far away, or a gravel truck driving down the other side of the street?

    1. Re:So was it by Anonymous Coward · · Score: 1

      A stellar collision in a galaxy far, far away, or a gravel truck driving down the other side of the street?

      Hence why there will be other identical detectors located far away. They all have to agree or you haven't detected anything.

    2. Re:So was it by wonkey_monkey · · Score: 2

      Welp, that's another $205 million down the drain because someone forgot to ask teh internets.

      --
      systemd is Roko's Basilisk.
  11. Other possibilities? by grasshoppa · · Score: 2

    Physicists are finishing a $205 million rebuild of the detectors, known as Advanced LIGO, which should make them 10 times more sensitive and, they say, virtually ensure a detection.

    That's if they even exist. Personally, I'd be more excited if they DIDN'T find any as that means there is something significantly wrong with their models, suggesting a whole new playing field yet to be discovered.

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    1. Re:Other possibilities? by Anonymous Coward · · Score: 1

      The Hulse-Taylor binary pulsar is inspiraling at the exact rate predicted by General Relativity and the emission of gravitational waves. So indeed it would be absolutely fantastic if A-LIGO doesn't pick up anything, or at the very least the stochastic background fluctuations...

      Fuck yeah, science.

    2. Re:Other possibilities? by Anonymous Coward · · Score: 2, Interesting

      Well, it wouldn't be the only hole in Relativity, but it would be a huge hole in Relativity. Which otherwise describes the observed Universe very, very well. It's not the best-tested theory in science; that probably goes to QED. Plus then you have to account for observations of massive stellar objects spiraling towards each other, which lose energy more-or-less as predicted by GR. See also the 1993 Nobel. New Physics is always fun, but I'm afraid that a null result would be better explained as experimental design flaws. You know, the way that every other similar experiment to date has been explained. The parallels with aether measurements are hard to avoid, but the alternative theories of gravity are, well...insufficiently predictive. Also aether was more of an assumption than a theory per se: there was never any evidence for it. Contrast with Relativity, which is undeniably a true description of reality.

      All told, while I agree with you about finding new things beyond the delineations of our theories, I don't think that a null result here would necessarily lead to much. IANAP, any corrections are appreciated.

    3. Re:Other possibilities? by Guy+From+V · · Score: 1

      The other possibility being gravity is instantaneous, which would be very much more exciting...but this experiment I don't think could discern this if it were true and gravitational waves were not.

    4. Re:Other possibilities? by blueg3 · · Score: 2

      That's why nearly ensuring detection is so attractive. If we don't detect a gravitational wave--which has been the case so far--it's a lot more meaningful with a very sensitive detector.

  12. Nice article by Dan+East · · Score: 1

    That was a good article. Pretty long with lots of background info and details on how it works. My questions is simply this: why not put this thing out west somewhere (Death Valley, etc) where there is less human and natural vibrations to interfere with it?

    --
    Better known as 318230.
    1. Re:Nice article by Whillowhim · · Score: 1

      It is a mixture of geographical separation and pork barrel politics. There are actually two LIGO interferometers, and the other one is "out west somewhere" right next to the Hanford Nuclear reservation in Washington state. The Hanford location has the advantage of being as close to the middle of nowhere as we could find during WWII, while still being close to a city that now has a lot of technical people and resources. The choice for the eastern location was less clear, and Louisiana was chosen as being "good enough" while also appeasing the desires of members of congress for some good old fashioned pork.

      However.... there were problems due to the Louisiana location. The facility passed all the seismic survey tests when they were run before the site was chosen and building was started. And it sure looks nice and pretty with all that woodland situated around it. Soon after coming online, however, that same forest become mature and a logging company started harvesting it for wood. As it turns out, dropping a tree to the ground (even miles away) causes enough seismic noise that it made the interferometer useless for much of the day when logging operations were going on. This forced them to install the active seismic damping system that was planned for Advanced LIGO well ahead of schedule, in order to get functionality back. In the end it worked out ok and gave the active seismic isolation some early testing data, but it definitely caused a lot of extra work for a while.

  13. $205M on LEGO? by Existential+Wombat · · Score: 1

    That’s a lot of bricks.

    1. Re:$205M on LEGO? by Neil+Boekend · · Score: 1

      Though not enough to build a bridge from London to New York.

      --
      Well, I might have a way, but it only works on a semi spherical planet in a vacuum.
    2. Re:$205M on LEGO? by rjhubs · · Score: 1

      I believe this was a reference to an element in the what-if book, not part of the ones posted online. http://www.theguardian.com/lif...

  14. and when they don't? by dltaylor · · Score: 1

    There's as much knowledge to be gained from a well-designed experiment that fails, as one that succeeds. They should ALREADY have found gravitational waves with the multiple space- and Earth-based experiments that have been run, particularly with all the big number-crunching on old data that is happening now.

    What do we learn about the nature of the Universe when THIS experiment also fails to provide evidence of waves of gravitational force propagating through it?

  15. I agree. by tlambert · · Score: 2, Interesting

    That being said I fully expect gravitational waves to be discovered.

    I am not so sure. There have been other experiments that should have detected them, but didn't. If this experiment also comes up empty, then physics may be facing another Michelson–Morley moment.

    I agree. Gravity waves are unlikely. In theory, we can test the idea with a direct experiment, but the cost would be in the multiple billions, and require spacecraft to loft a tetrahedral constellation of some very large masses, and then you'd have to fling another large mass at an appreciable fraction of the speed of light, probably via solar slingshot, and (effectively) have it "instantaneously appear" intersecting a non-orthogonal plane vector through the tetrahedral constellation. That'd basically give you a wave delta that you could see based on laser interferometry along the vertices of the tetrahedron.

    Assuming gravity propagates at the speed of light as a force, rather than being an artifact of space-time, which would mean you don't get any waves. Which we've so far not been able to detect, probably because they don't exist. 8-).

    1. Re:I agree. by GlowingCat · · Score: 1

      Bern, Carrasco, and Henrik Johansson of CERN Laboratory argue that gravitons behave like two copies of gluons, the carriers of the strong nuclear force, which “glues” quarks together inside atomic nuclei.

    2. Re:I agree. by rHBa · · Score: 1

      In theory, we can test the idea with a direct experiment, but the cost would be in the multiple billions

      Link this?

    3. Re:I agree. by painandgreed · · Score: 2

      Assuming gravity propagates at the speed of light as a force, rather than being an artifact of space-time, which would mean you don't get any waves. Which we've so far not been able to detect, probably because they don't exist. 8-).

      I believe I remember running across the proof for gravity waves while looking at the special relativity derivation of the Lorentz transformation. So, if gravity waves don't exist, then Special relativity is under some pressure. Of course, special relativity happens in Minkowski space which is flat and not warped due to gravity which we know is not the case anyway. Unsure about a similar proof of gravity waves using general relativity.

    4. Re:I agree. by Anonymous Coward · · Score: 1

      Gravity waves are inherently a part of general relativity, not special relativity, which doesn't touch gravity (outside of some contrived situations). They come from a linearization of the Einstein field equations in GR, and numeric approaches have been done for non-linear generation of gravity waves for situations like orbiting compact massive objects.

    5. Re:I agree. by tlambert · · Score: 1

      In theory, we can test the idea with a direct experiment, but the cost would be in the multiple billions

      Link this?

      It'll be interesting to see how this works out. I'm not certain that a planar detector will work out like they hope.

    6. Re:I agree. by tlambert · · Score: 1

      Assuming gravity propagates at the speed of light as a force, rather than being an artifact of space-time, which would mean you don't get any waves. Which we've so far not been able to detect, probably because they don't exist. 8-).

      Except for still having to explain the orbital decay of complex objects matching predictions based on GR involving loss of energy due to gravity waves and gravity traveling at the speed of light.

      And you don't need a tetrahedron of space craft, just three space craft to confirm or deny the quadrupole nature of gravity waves.

      It's a fun gedanken experiment, but I'm not sure the Lisa Pathfinder will be successful; the quadrupole formula requires that the plane of polarization be distinct, and that the orbit be an ellipse. The Lisa experiment has some fundamental assumptions about a collision being the wave source, rather than an orbital source.

      It'd totally be a bummer to spend all that money and not see anything because the detector happens to be in a 2D plane coinciding with a detectable event, and the lack of additional planes made it invisible.

      Personally, I have to believe that we have a fundamental misunderstanding of something, because we otherwise should have seen them in one of our existing detectors, if they were there to be seen. I don't think the longer baseline Lisa gives us is going to help detect something that we are fundamentally getting wrong somehow.

      I used to joke with some of my friends that there's be two great reasons Michelson-Morely might not have shown anything:

      (1) The reference frame is sufficiently pinned by the gravity well of the Earth that we don't see any drift through the "luminiferous aether" because we are frame-dragging at a higher degree than the equipment is capable of distinguishing.

      (2) The Earth *really is the center of the Universe*, so also: no drift relative to the universe's inertial frame.

      It may be that we won't see gravity waves (if any exist) until we get a device pretty far out into interstellar space.

  16. An Even Cheaper Method by Anonymous Coward · · Score: 1

    A way cheaper still would have been to construct a Laser ENTERFEROMETER Gravitational-Wave Observatory (LEGO), an ultrasensitive instrument made of little extruded thermoplastic bricks. If they don't have one yet, I'm sure they'll have a kit to build one by Christmas, in toy stores and available at fine toy stores everywhere and online! Recommended for ages 25-75.

  17. Re:Not gonna happen by networkzombie · · Score: 1

    Better yet... will this tell us if Einstein was correct with the whole curvature of space thing, or if matter has an inherent attraction, and therefore space is not a fabric at all, just a void? Has anyone proven this?

  18. LSU 1970s; history by harvey+the+nerd · · Score: 1

    The article only talks about MIT history and laser inferometers (LIGO). It doesn't credit Louisiana State University's efforts to build resonant mass gravity wave detectors from the 1970s. By 1972, physics Prof William O Hamilton at LSU was working on a multi-ton aluminum bar and a He3 dilution cooler in what would become the Allegro graviy wave detector.

    Some interesting history papers:
    http://arxiv.org/ftp/arxiv/pap...
    http://www.slac.stanford.edu/g...

  19. Re:Not gonna happen by ian_billyboy_morris · · Score: 1

    Gravitational Lensing already proves spacetime curvature.

    Lensing Image

  20. duh by gzuckier · · Score: 1

    what would the silver surfer be surfing on otherwise?

    --
    Star Trek transporters are just 3d printers.
  21. Re:Everybody gear up by gzuckier · · Score: 1

    I have a cloaca, you presumptuous clod.

    Keep it in the cloaca room.

    --
    Star Trek transporters are just 3d printers.