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LIGO Fails To Detect Gravity Waves
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."
Fails to detect, or there was nothing to detect? Damn sensationalist headlines.
Write your own Choose Your Own Adventure. http://www.freegameengines.org/gamebook-engine/
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
That must be the most useless analogy ever.
The grass is always greener on the other side of the light cone.
LIGO Succeeds in Detecting No Gravity Waves
"...of less than a thousandth the diameter of an atomic nucleus."
Would that be a hydrogen nucleus... a uranium nucleus? Please be more specific.
"I like to lick butts!" by MobileTatsu-NJG (#32700246) (Score:5, Informative)
... don't abandon the theory, just look harder. Kind of like global warming (or is it "climate change" now?)
They're little plastic blocks that kids build things with. Granted, you can make things like the Millenium Falcon with them but it can't actually fly.
Oh wait, you said LIGO, nevermind.
Summation 2
There is no gravity - Earth sucks!
In Murphy We Turst
1) General Relativity as formulated by Einstein (and a lot of other similar derivates - are there many?) would be in serious doubt. An exam question I had was take GR and show gravity waves exist - you basically show how the wave equation falls out of the formulas and these things carry momentum out of a system.
2) You then need to explain stuff such as Mercury's orbit precession and observed effects of double Neutron stars slowing down - the FSM stirring his planetary meatball lunch slower?
The Singularity is closer than you think
Quant
The non-detection was actually a valuable contribution, as it helped to distinguish between competing models for what powers GRBs.
Alternately, since no one can really say where gravity itself comes from, the concept behind LIGO could simply fail to account for how gravity really works.
Who can say that the same shortening of one side compared to the other doesn't affect the speed of light proportionately to the change in length? In that case, we could just as well have a black hole buzz our solar system and LIGO would hapilly report nothing of interest.
I 100% support science research, especially into some of the "real" unsolved problems such as the nature of gravity itself; but I would call this simply "bad" science - You can't use one poorly-understood phenomenon to explore another.
I mean - I admit to being ignorant, but has there ever been a gravity wave detected?
Just asking.
Gravity Waves, meet Bigfoot, and the Loch Ness Monster and flying saucers and santa claus..
Ain't no such thing.
This is my sig.
For all the people arguing over whether or not this is a failure of LIGO or not...it doesn't really say much at all. Initial LIGO (which is currently running) is more of a proof of concept sold as a viable project. But if you look at the expected rates of detection, the absolute high end for all binary sources is less than one event/year. The low end is between 4 events every 10000 years and 4 events every 100 years. The other source types are not any better.
This article basically says that because LIGO is known to not be sensitive enough to measure past a certain distance from Earth (which encompasses the Andromeda galaxy, in whose direction this burst occurred) and because no detection was seen, the burst was not caused from a source in the Andromeda Galaxy.
I suppose that after spending all this money its not a bad thing that LIGO can actually produce some useful results (though I doubt they were amazingly useful). Advanced LIGO should be able to do the job - but not for another 5-6 years. At that point, the minimum event rate is supposed to be around 1/year and we should finally get some sort of positive detection.
Personally I'm hoping Advanced LIGO does work, because otherwise all this money will have gone to waste and the field of gravitational wave astronomy will be even more damaged than it already is. The thing is, many people in astronomy who are not affiliated with LIGO are not excited by it. Maybe that interest will be rekindled when Adv LIGO actually works, since right now its more of an engineering problem than an astronomy or physics problem. More people are interested in LISA which (if it ever launches) should have many more interesting sources. Its amusing seeing LIGO people try to point out the flaws of LISA while trying to explain why LIGO doesn't work, but then maybe I'm biased since I am working on LISA (though I have worked on LIGO in the past).
Perhaps the LISA (NASA/ESA) project will have more luck (2015+).
and merely an incremental increase in knowledge. It either means that gravity waves are either smaller than "1/1000 of the diameter of a nucleus" (whatever that means) which would require a re-write of the theory because they were predicted to be large enough to detect or LIGO doesn't work which would require a re-write of the theory of gravity because according to that theory LIGO should detect gravity waves. It's a nice result but nothing definitive.
At the risk of opening up some sensitive old wounds here, if you had more than one of these...
would they be called LIGOs?
Nononono... the standard "really tiny" analogy in popular media is "fraction of a human hair", e.g. "one thousands of the width of a human hair".
(completely disregarding that the width of human hair varies by at least an order of magnitude from person to person).
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?
I'd be fascinated to see what's wrong with the reasoning here!
Not only does it mean we've done our job, it's also a whole lot of fun. Suddenly there's a whole new theory (or even better, lack of one) to test. Lots of new experiments to do. More hours to spend in basement labs...
ID'ers just don't know the fun they're missing.
That's strange coz I have to say I did feel a little lighter on Saturday.
Genesis 1:32 And God typed
Comment removed based on user account deletion
State science, you're going to pay for it like it or not.
Something I don't understand from the article is that it seams they experiment supposes that both the X-way burst and the gravitational waves should come on time. But what if the gravitational waves had passed before the X-rays? Is there something in the physics theory that predicts this?
I'm not even a physicist, but I can recall someone arguing that gravity has the estrange property of been instantaneous. Is this is true, the even that generated the x-rays happened many years ago, right? why shouldn't we be able to detect any gravitational waves now?
What you apparently do not understand is that this device can detect gravitational waves.
That has never been demonstrated. For all we know, gravitational waves may simply not exist.
Sorry, I kept saying X-rays in my previous post when I should had say gamma rays.
GR is only one of a large number of possible theories that all make similar predictions for the kinds of phenomena we have actually been able to observe. GR happens to be the one that was first written down, and as long as it worked, there has been no reason to consider any of the others.
I just happened to watch:
...today.
http://video.google.com/videoplay?docid=-3934388013805572309&q=bbc+horizon+death+star&total=2&start=0&num=10&so=0&type=search&plindex=0
The gravitational wave detector doesn't detect gravitational waves?
"Hooray, I'm useful. I'm having a wonderful time." --Dr. Zoidberg
They're using their grammar skills there.
Seriously, how can you trust CDE users ?
I did an internship at LIGO last year, and let me tell you, they're always trying to make it sound useful for things like this. I went to one talk where this guy basically said "LIGO is very useful because the lack of any signal means that there can't be huge mountains on rotating neutron stars.". WTF? Neutron stars are widely expected to be the most perfectly spherical objects in the universe. Why would they have huge mountains? Nobody knows, but LIGO definitely ruled it out too, and that's a good thing I guess...
Honestly, there's very little chance of seeing anything until Advanced LIGO is ready in a few years. Now, if Advanced LIGO doesn't see anything, that will be news.
Neil is that you? Yeah yeah, it's me... Neil...
There have been no direct detections of gravitational waves so far. There have been indirect detections (most robustly with the various binary millisecond pulsars, whose orbits slowly decay due to their radiating energy away in gravitational waves), but no direct detections. However, this was not really seen as an issue, as gravitational wave searches before LIGO suffered from the problem that there were no known sources strong enough for them to detect with good probability. You have to start somewhere, and there is always the chance of either good luck, say a close supernova, or some unknown source that is stronger than expected, but I believe that this is the first actual event whose gravitational waves, by a reasonable model, had a chance of being detected with existing equipment. One such non-detection means nothing - maybe the Gamma Ray Burst occurred way behind the Andromeda Galaxy, for example. If this is consistently repeated, we will eventually conclude that there is something wrong with our physics or our astrophysics, but it is much too soon for that.
Does a geisha painted on a Japanese fan know she's wrinkled? IOW, it's a frame problem, like biting your own forehead.
``Tension, apprehension & dissension have begun!'' - Duffy Wyg&, in Alfred Bester's _The Demolished Man_
They could not find an anticipated ether-drag. Their result nicely dove-tailed with special relativity. However Einstein started from first principles and not their result.
Perhaps the gravity result suggests a replacement for general relativity.
... if alternatives to GR got some more attention.
http://www.plasmacosmology.net/spec.html
http://peswiki.com/index.php/PowerPedia:Tesla's_Dynamic_Theory_of_Gravity#Dynamic_theory_of_gravity
Personally I'm getting the feeling that we're getting more and more off-course with the dark energy, dark matter, 10 dimensional 'string thingy' theories.
Yes, I am saying that this is a feeling.. I'm not a(n) (astro)physicist... but somehow I have the idea that the universe just has to be more elegant than our currently collection of exotic and unwieldy theories.
All good programmers should be able to understand what I'm saying in the previous paragraph.
Many persons have implied that not detecting gravitational radiation will somehow invalidate General Relativity. Unless I am mistaken, every theory of gravitation that requires that
1. Forces due to massive bodies (gravity) to propagate at the speed of light, and
2. Energy to be conserved
must also have gravitational radiation. Information propagates at infinite speed in Newton's theory of gravity, so there is no gravitational radiation.
Why is it whenever I have mod points there are no interesting topics to use them on :(.
Anyway, the parent makes a very valid point.
What if gravity waves are actually slower (or, dare I say it, faster) than the speed of light, what happens to the General Relativity equations then?
Quantum Physics a.k.a. sub-molecular statistics
LIGO sucks, no... wait...
If it's that vibration sensitive, we ought to put it at a Lagrange point.
Gravitational waves *have* already been detected, but they have been detected *indirectly*
(e.g. from observing changes in the rotation of super-massive neutron stars).
The LIGO experiment endeavors to provide *direct* evidence for their existence because
in science such evidence is ultimately more satisfying, but it is not strictly necessary.
Once upon a time, for example, evidence for the existence of atoms was also indirect, being
inferred from the behavior of gasses and other phenomena like Brownian motion. It was only
much, much later that atoms were actually directly observed, via advanced microscopes, but
in the meantime the atomic theory was never called into serious question.
So even if LIGO and its successors fail, the indirect evidence in support of gravity
waves is still strong enough to fully support the concepts of general relativity.
Hello? Of course they couldn't detect anything. Gravity is an observed illusion (in our frame of reference) caused by the curvature of space-time. Do these people honestly get grants for this nonsense?
I have no doubt that if gravity waves exist, LIGO will eventually pick one up. It's question of timing.
I visited one of the LIGO facilities once, it was fascinating. But I learned two things there about how sensitive it was:
(1) When my group and I came in, they showed us the real time data -- there was a gigantic spike in the middle of the screen. One technician pointed to it and said "That was from you guys rolling up to the facility, we knew when you were almost here.". I then got to hear complaints about all of the loggers in the area that interfere, a highway being close enough for big trucks passing to cause spikes, etc.
(2) While in the control room talking, the mirrors went out of alignment and you could hear an alarm. One of the scientists got on his computer and came back with the reason: "There's a small earthquake in Greenland, it should be over soon."
They told us of the plans to upgrade the facility. Most of it involved adding more shocks and counterweights and all to dampen the various effects we saw that day. They claimed it would be enough, and seeing as their first few test runs were almost right on the money, I'm sure they're correct. But I imagine a little bit of luck is involved as well: having some big cosmic event happen when there aren't a lot of truckers on the road or earthquakes, etc.
...Absence of proof != Proof of absence.
What's purple and commutes? An Abelian grape.
"LIGO Detects Absence Of Gravity Waves" would be more accurate.
"LIGO Establishes Absence Of Gravity Waves Above Its Detection Threshold From A GRB" would be more accurate yet but too long for a headline.
Warning: this article may contain humor, sarcasm, parody, and perhaps even irony. Read at your own risk.
"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."
Which atomic nucleus? The nucleus for hydrogen is far smaller than the nucleus for uranium.
Still waiting on Serviscope_minor to wake up to fucking reality and realize that Jessica Price isn't going to fuck him.
Of course, this is as I said only accurate on the order of a percent. Gravitational waves could travel a little faster or slower than light, in principle. But odds are, they don't. For this experiment, a few percent change in speed could mean a big difference in time, considering the distance traveled. So ultimately you're right: experimental constraints don't pin down the speed well enough to ensure that the two events are simultaneous. But given the large amount of evidence supporting relativity, it's probably not a coincidence that the speed of gravitational waves is so close to that of light.
This is another failiure in the long history of trying to detect gravity waves.
And I see lots of replies pointing out that gravity waves apparently do exist (usually citing the rotating binary star pair that are spiraling in at the rate predicted by general relativity).
Of course if gravity waves as predicted do exist and behave according to the predicted mechanism, I expect the physicists who designed this detector would have done it right and that it would detect them.
But that raises a question I have NOT seen answered:
Has this particular detector ever given an indication of actually detecting a gravity wave?
The negative result would IMHO be more significant if we knew that the detector was operating and actually had detected waves - or something - from other events.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
Unfortunately, too many physicists aren't very familiar with the theory of information.
If one can state the one basic principle in that theory it is that to send or store information you have to spend energy, increasing the entropy in the universe. However, thermodynamics is a macroscopic phenomenon, at quantum dimensions all phenomena are reversible. In quantum dimensions one could say that time is bidirectional. Coincidentally or not, it seems that in quantum dimensions there is no limitation in speed, information can be transmitted instantly. And, what is more, there are experimental results confirming this.
I confess I'm not too confident on those proofs that information cannot be transfered faster than light. Until someone creates a theory that conciliates quantum mechanics with general relativity, I'm willing to believe anything. Maybe irreversible time is just an illusion created by the thermodynamic effects in our macroscopic brains...
About a century ago, it was a serious blow to the scientific theories of the time when all the experiments done to prove the existence of the "luminiferous aether" failed. Maybe gravitational waves are the 21st century aether.
In a way, I hope so. Physics has grown too routine, a new grand theory would be nice...
there is always the chance of good luck, say a close supernova
If it's too close, it's very bad luck!
That that is is that that that that is not is not.
They will not, if the sides are curved. The big question is how do you define a straight line. Einstein assumed that in a vacuum you don't have any line that's more perfect than a ray of light. However, gravitation bends light rays, this has been proven experimentally to a very high precision. Therefore, a triangle made by three light rays around a mass will not have its angles adding up to 180 degrees.
Of course, you can always postulate the existence of an immaterial straight line which is not affected by gravity. Using those theoretical lines space wouldn't be curved by gravity, but what good is that? You could never use those theoretical lines to do any measurement or to build anything in this universe, so you might as well assume that the true straight line is the straightest thing we have here in our universe, the rays of light.
...It is integral to the equations that model electromagnetic phenomenon.....True. It is however NOT integral to equations that describe gravity! There is no time value in them. This is false. Time most definitely appears in the Einstein field equations. The linearized version of them is almost identical to Maxwell's equations.
You are thinking of Newtonian gravity, in which gravity is instantaneous. This is not true of relativistic gravity, in which gravity propagates at the speed of light. Therefore, if someone turned on a gravity generator or suddenly removed a gravity shield, the effects of that should be instantaneous, or at least very fast over large distances. This is false, as can be proven from the Einstein field equations. See here. Until Mr. Roemer first measured the speed of light, it too was thought to be instantaneous. Maybe someday the speed of gravity will be measured. It has been, albeit indirectly. The 1993 Nobel Prize in physics was awarded for this work. It equals the speed of light, plus or minus a few percent experimental error. The sun and the center of our galaxy are in gravitational "touch" with each other NOW, not how they were thousands of light years ago. This too is false. See the paper I cited here.
Even if you're trying to save the planet from global warming, I told you not to switch everything off on fridays!
OK, yeah, it's funny... ABOUT THE FIRST TWO TIMES YOU HEAR IT. After about the fiftieth, though... not so funny - more like... pathetic.
That is all.
AC's comments in the Parent Post are not complimentary, but they are true. Articles on wikipedia stay on wikipedia until somebody takes time from their life to challenge them. I agree with AC, that "trusting wikipedia to be accurate about something" is a "BIG MISTAKE." Although wikipedia provides an extremely valuable service, it is only useful as an introduction to topics, and in some cases as a referral to "authoritative" sources. It is, by design, not "authoritative" itself. AC didn't say "everybody who uses wikipedia is a lobotomized moron" or "wikipedia is completely useless; there is no 'correct' way to use it." Those would have been "trolling" comments.
He made a valid point. Down-modding about it won't help you.
All 19 hijackers were known terrorists 09-10-2001. Lack of FBI intelligence does not justify warrantless wiretaps..
I wish I hadn't blown my mod points modding up actual informative articles in this thread. I'd rather see them go unmodded than see wrong claims marked "informative"
And this "Informative" post is wrong as well: relativity always applies when considering the speed of gravity, no matter how slow the motion or how weak the field (more here). And it is ridiculous to claim that relativity has been shown with respect to electromagnetism but not gravity, given all the experimental tests of GR (here).
This is a failure neither of LIGO nor of theories of GRBs. The error box on the sky position of GRB070201 included one of the arms of Andromeda, but it also included a lot of sky behind Andromeda. Possible explanations for not seeing GWs associated with the burst include 1) the source, whatever it was, was not in Andromeda, but farther away, or 2) the source of the GRB was in Andromeda, but it was produced by something other than a compact binary merger. This would also not be inexplicable; the abstract of the article submitted to the Astrophysical Journal says "This upper limit does not exclude current models of SGRs [soft gamma-ray repeaters] at the M31 distance." What is excluded, at >99% confidence, is a neutron star/neutron star or black hole/neutron star merger in M31 (Andromeda).