back to article Gravitational waves: A new type of astronomy

The first time physicists announced that the Laser Interferometer Gravitational-wave Observatory (LIGO) had detected gravitational waves, on September 14, 2015, it was breaking news. The discovery coincided with the 100-year anniversary of Einstein's theory of General Relativity, which predicted the existence of gravitational …

  1. Mike Pellatt

    Michelson-Morely reborn

    I find it wonderful that an experiment we reproduced at school - the Michelson-Morley - that disproved the theory of the stationary aether, is reborn with today's technology, and validates general relativity.

    IFLS, as they say :-)

  2. Anonymous Coward
    Anonymous Coward

    Poor science

    The second announcement does not PROVE that the first wasn't a fluke, but is consistent with the same mistakes being made twice. Other scientists will have to analyse the results to see whether any mistakes in the experiment are present.

    1. This post has been deleted by its author

      1. Dr. Mouse

        Re: Poor science

        You may have a point about someone hiding behind anonymity, but that doesn't make his statement invalid in and of itself.

        We have seen 2 results which corroborate the hypothesis. This is not, yet, enough to be called proof (IMHO), but it is evidence pointing to the hypothesis being valid. We will either see more results validating the hypothesis or (probably more exciting) some weird results which suggest a flaw in the hypothesis, leading to potentially exciting new physics.

        Whatever happens, it's always good to gather more data.

        1. John Sager

          Re: Poor science

          It's true that the gravitational radiation has only been measured by one method, and that more independent methods would be good. However the character of the signals received corresponds with high accuracy to the expected character of gravitational radiation from that scenario and also matches what General Relativity would predict. In fact, the results validate GR in an extreme gravity regime that can't really be measured by other methods. If only Einstein were alive to see it!

          1. John Mangan

            Re: Poor science

            @John Sager - "gravitational radiation has only been measured by one method". Not entirely true. If you are referring to direct measurement I will grant you the point. However I believe that the energy loss of certain pulsars has been calculated to match what would be predicted by GR for gravitational radiation - so an indirect detection and not for the same sources.

        2. Anonymous Coward
          Anonymous Coward

          Re: Poor science - @Dr Mouse

          I was referring to the headline to the post - "Poor science". Headline produced on no evidence whatsoever. There is a big difference between something not being proof [let's bot get too far into what that means], and calling it "poor science". Working at the absolute limits of current detection may be many things, but poor science it is definitely not. Would you have given your post that title?

          1. Dr. Mouse

            Re: Poor science - @Dr Mouse

            I was referring to the headline to the post - "Poor science"

            I agree that was incorrect. I doubt any of this is "poor science".

            1. Anonymous Coward
              Anonymous Coward

              Re: Poor science - @Dr Mouse

              On the other hand articles like this often just throw up more questions..... questions which may well have been answered by those involved with the project but aren't reproduced in the article.

              If I liken gravitational waves to waves on an ocean I can see how seeing a 100 meter high wave and observing some large event (I don't know, a meteor falling into the sea) might lead to the conclusion that one caused the other. I suppose you could then make inferences about the mass of the object which hit the sea given the height and speed of the wave when it reached you.

              However, aren't there quite a lot of other variables to consider? If there's a large sun between us and the event (a sun which passed across the wave front) then wouldn't that distort the wave? So, I would imagine that large events produce such enormous waves that other objects in their path have limited impact but I'd also imagine that there will come a point where it is like looking at the waves on the shore... so many that it's basically noise with no useful information.

              Fascinating subject in either case.......

              1. John Mangan

                Re: Poor science - @Dr Mouse

                "However, aren't there quite a lot of other variables to consider? If there's a large sun between us and the event (a sun which passed across the wave front) then wouldn't that distort the wave? So, I would imagine that large events produce such enormous waves that other objects in their path have limited impact but I'd also imagine that there will come a point where it is like looking at the waves on the shore... so many that it's basically noise with no useful information."

                Not really. The waves are quadropoles and therefore will be pretty well unaffected by a 'monopole' object (not the best scientific explanation but I think gives a clear image of what is happening).

                Also for your second point the waves are incredibly weak to start with, energy falls off according to 1/R^2 as they expand spherically and therefore 'soon' fade into undetectability. Also there is no 'shore' for them to be reflected from (current modesl, etc.)

                1. Stoneshop Silver badge
                  Boffin

                  Re: Poor science - @Dr Mouse

                  energy falls off according to 1/R^2 as they expand spherically

                  ITYM 1/r^3. Area of a spherical object (cow or otherwise) is 4/3*pi*r^3, so energy per unit area of a spherical wavefront is proportional with r^-3

                  1. danR2

                    Area vs Volume of a sphere

                    " 4/3*pi*r³ " That's the volume.

                    Area is grade six math: A=4πr²

                  2. Ken Strain

                    Re: Poor science - @Dr Mouse

                    With GW detectors like Advanced LIGO we measure the wave amplitude (it is not like detecting photons - proportional to energy or power as is done in optical astronomy). The amplitude falls off as 1/r. Power is proportional to amplitude squared, which gives the familiar 1/r^2.

                    Ken

      2. Andy The Hat Silver badge

        Re: Poor science

        Two independent detectors producing time displaced, near identical signals. An error would have to have been replicated independently ... twice now ...

        No, actually amazing science, just poor interpretation by an AC

        1. Terry 6 Silver badge

          Re: Poor science

          Scientific theory says that you can never prove anything to be true. The most that you can do is to make a prediction based on the observed evidence and test that. If the prediction proves true the hypothesis stands until disproved ( "falsified") or until the weight of evidence is such that no alternative is feasible.

          So evolution can be reasonably held "true": There is no rational alternative explanation of observed phenomena.

          Black holes likewise.

          Dark matter and dark energy are the best possible explanations for the existence of a universe that remains stable while expanding, with the current understanding of visible mass, But a better explanation may arise out of new observations.

    2. Stoneshop Silver badge
      FAIL

      Re: Poor science

      Other scientists will have to analyse the results to see whether any mistakes in the experiment are present.

      Don't you think this is already being done?

    3. TitterYeNot

      Re: Poor science

      "The second announcement does not PROVE that the first wasn't a fluke, but is consistent with the same mistakes being made twice. Other scientists will have to analyse the results to see whether any mistakes in the experiment are present."

      Seeing as the data produced by each observation of a gravitational wave was analysed for around 6 months prior to public announcement, I think its fairly safe to say that other scientists' analysis will produce the same results.

      And you're talking about flukes.

      The theory of General Relativity makes very specific predictions about gravitational waves i.e. what causes them, their effects on space/time, their frequency and speed. Then an experiment designed to observe these waves detects a wave in 2 detectors 3000 km apart, the time difference between the two detections matching exactly what you'd expact from a wave propagating at light speed, and with an amplitude and frequency matching those predicted by General Relativity.

      Then a few months later it happens again, demonstrating it wasn't a one off.

      That's not a fluke, it's hard evidence of a phenomenon predicted by a theory whose predictions have always been shown to be correct (when they can be measured.) Obviously replication of these results, especially by other teams with other detectors, will act as further confirmation, but at the moment, if it walks like a duck and quacks like a duck...

      1. Louis Savain

        Re: Poor science

        "Seeing as the data produced by each observation of a gravitational wave was analysed for around 6 months prior to public announcement, I think its fairly safe to say that other scientists' analysis will produce the same results."

        True. Corroboration is indeed powerful, unless, of course, the data was the result of a fake injection that is indistinguishable from what is expected according to the carefully contrived model.

        Fake injections are a bitch. I know. But they happen.

        ahahaha...AHAHAHA...ahahaha...

  3. Anonymous Coward
    Joke

    Politness.

    If it is true, this means that - to be polite - we have to wave back.

    Just ponder on the gravity of my joke.

    1. Anonymous Coward
      Anonymous Coward

      Re: Politness. - If it is true, this means that - to be polite - we have to wave back.

      If you bring one of the large black holes required, I'll try and kickstart the other one.

      1. Anonymous Coward
        Anonymous Coward

        Re: Politness. - If it is true, this means that - to be polite - we have to wave back.

        I'm sure I can find several large black holes in the EU budget.

        1. Fruit and Nutcase Silver badge
          Thumb Up

          Re: Politness. - If it is true, this means that - to be polite - we have to wave back.

          @Ian Emery

          I'm sure I can find several large black holes in the EU budget.

          Ooh you are awful, but I like you

          1. Anonymous Coward
            Anonymous Coward

            Re: Politness. - If it is true, this means that - to be polite - we have to wave back.

            GAWD! I havent had a Dick Emery joke launched at me in over a decade!!

            (You are showing your age!)

  4. Woza
    Black Helicopters

    So how long until

    We can detect a passing GSV?

    1. BoldMan

      Re: So how long until

      It will take a lot more Gravitas...

  5. Arctic fox
    Happy

    RE:"was greater than all the energy radiated by every star in the observable universe"

    "Although the energy released from both pairs of colliding black holes was greater than all the energy radiated by every star in the observable universe, it would have remained invisible if it wasn't for LIGO."

    It is events on that inconvievable scale that really cause my mind to boggle. We can calculate something like that. We can now observe it even. However, imagine it? Quite impossible!

    1. Anonymous Coward
      Anonymous Coward

      Re: RE:"was greater than all the energy radiated by every star in the observable universe"

      > "the energy released from both pairs of colliding black holes was greater than all the energy radiated by every star in the observable universe

      ... is utterly shite and meaningless.

      Was it greater than all the energy radiated by every star in the observable universe in one second? In one year? In totality (from the birth of each star until its extinction?)

      1. Andy The Hat Silver badge

        Re: RE:"was greater than all the energy radiated by every star in the observable universe"

        It was the power output of the gravity wave burst as the two black holes coalesced. One was accelerated from 0.3 to 0.5c in about 0.15seconds ... not bad for a few solar masses.

  6. kmac499

    Astonishing..

    Albert sitting in his patent office imagining what it would be like to ride on a beam of light, or Peter Higgs exploring the consequences of other theories. Both needing massive, hugely expensive, fantastically precise machines to confirm their predictions.

    The real beauty of science is, if the experiemnts proved then wrong, both men would have accepted the finding and moved on.

  7. frank ly

    Clarification

    "... the passing gravitational waves only moved the mirrors by ..."

    As I understand it, it's not that the mirrors are moved/disturbed but that the 'very fabric of space itself' is compressed then expanded along the direction of propogation of the gravitational wave as it passes by. Hence, a single detector arm can't detect a wave passing at right angles to its axis, so they have two detector arms at right angles to each other. (This rasise the question of what happens if a gravitational wave arrives from vertically above.)

    If anyone has a more rigorous or correct explanation then please share it.

    1. Stoneshop Silver badge
      Boffin

      Re: Clarification

      (This rasise the question of what happens if a gravitational wave arrives from vertically above.)

      For one detector that would indeed cause it to not detect it, but there are three: one at 119W, one at 90W and one at 10E. Given that the Earth is, roughly, a sphere, for two of the detectors an incoming wave can not be coming in from straight above if it is for the third.

  8. Winkypop Silver badge

    What a time to be alive

    I'm glad someone was paying attention in science class!

    1. Anonymous Coward
      Anonymous Coward

      Re: What a time to be alive

      Particularly pleasing that the person responsible for those steel and fibreglass suspension wires is Professor Strain.

      > 0.7 of a thousandth of a femtometre (10^-15m) – smaller than a proton

      According to wikipedia, the radius of a proton is about 0.84–0.87fm. So if that statement is correct, they have detected a displacement which is 1/2500th of the diameter of a proton. Incredible.

      I wonder how they arrange it so that, say, a nuke going off in North Korea doesn't disturb the mirrors by such a tiny amount?

      However, El Reg missed the most important part of the announcement which you can find at https://www.ligo.caltech.edu/news/ligo20160615

      > The "chirp" tones of the two LIGO detections are available for download. Formats are suitable as ringtones for either iPhone or Android devices.

      1. John Mangan

        Re: What a time to be alive

        "I wonder how they arrange it so that, say, a nuke going off in North Korea doesn't disturb the mirrors by such a tiny amount?"

        Basically the nuke will generate 'ringing' at one set of frequencies and the detector will be sensitive at different frequencies. Also if there a coincident signal at two or more detectors in the right frequency range there are plenty of seismometers (including at the sites of the detectors) to throw up a 'just check this would you?' alert. Then you look at amplitudes, frwquencies, attack, decay, etc.

  9. smartypants

    Good Things

    This experiment and the work by people to make it goes on my Good Things list...

    It balances nicely some of the recent additions to my Bad Things list.

    It's a shame there are so many people wasting their lives on Bad Things.

  10. Mage Silver badge

    all data is shared

    Good that it's going to be a collaborative world wide effort.

  11. This post has been deleted by its author

  12. Florida1920
    Pint

    Nothing new here

    I personally experience gravity waves whenever I consume too much of what's in the icon accompanying this comment.

  13. AwesomeKhan

    How powerful is a gravitational wave close to the source?

    Imagine that there was a planet (or similar size object) close to the 2 black holes when they collided. Does anyone know how this would be affected by the gravitational waves? I'm guessing that the object would be stretched / compresses but would the magnitude be minimal or would it be observable (e.g. meters in magnitude)?

    1. roeltz

      Re: How powerful is a gravitational wave close to the source?

      I want to know this too.

    2. John Mangan

      Re: How powerful is a gravitational wave close to the source?

      It's an interesting question - and I don't know the answer - but you need to consider that such a proposed planet has to be far enough away from both black holes not to have been ripped apart by tidal forces (which will be far more powerful than the tidal forces of any gravitational radiation emitted by the system) so I am going to say - at such a distance - still pretty negligible.

      1. Ken Strain

        Re: How powerful is a gravitational wave close to the source?

        Very rough order of magnitude calculation: to get "meters of magnitude" distortion on an Earth-size planet requres a strain (i.e. diameter change/diameter in this case) of more than about 1m/10^8m. So for the pulse of waves from the final merger to cause such an effect, the planet would need to be about 1/10000th of a lightyear away. The systems Advanced LIGO detected were around 1 billion LY away and produced a peak strain in the detectors of around 1 part in 10^21. The strain is inversely proportional to distance so we are looking for 10^13 times smaller distance. That is about 6 astronomical units, or a little more than the distance of Jupiter from the Sun.

        It seems unlikely that there could be a planet in an orbit like that (it would have had to survive whatever formed the black holes, e.g. supernovae, then stayed in a stable orbit for probably billions of years for the eventual merger).

        Ken

        ps. If you are the same JM that was previously involved in all this - very best wishes!

        1. John Mangan

          Re: How powerful is a gravitational wave close to the source?

          @Ken Strain - Ken, it is indeed I. And I'm very glad to see you haven't had to correct any egregious errors on my part. It's been a long time and the memory's not what it was. I re-read my thesis after the announcement of the first detection and it really brought home how much I had forgotten..

          Oh, and congratulations of course to everyone in Glasgow!

  14. Louis Savain

    Why LIGO Is a Scam

    http://rebelscience.blogspot.com/2016/05/why-ligo-is-scam.html

    Abstract:

    In this article, I argue that the billion-dollar LIGO project that recently claimed to have detected gravitational waves from the collision of two black holes located more than a billion light years from earth is nothing but a scam to defraud the public. I argue that gravitational waves cannot exist because they are based on the false assumption that changes in gravity propagate at the speed of light. I further argue that the spacetime model is wrong because it is a block universe in which nothing happens and that gravity is a nonlocal or instantaneous phenomenon related to the law of the conservation of energy.

    And for those who are really interested in this sordid affair, read the following:

    Why Steven Carlip Is Mistaken about the Speed of Gravity or Why LIGO Is Still a Scam

    http://rebelscience.blogspot.com/2016/06/why-steven-carlip-is-mistaken-about.html

    ahahahaha...AHAHAHAHA...ahahahaha...

    1. Anonymous Coward
      Anonymous Coward

      Re: Why LIGO Is a Scam

      LIGO LOONY

    2. danR2

      Re: Why LIGO Is a Scam

      "I argue that gravitational waves cannot exist because they are based on the false assumption that changes in gravity propagate at the speed of light at all."

      There is so much about that sentence that isn't even wrong, it's hardly possible to repair it. I've made a start, however. Why is propagation at c particularly egregious about these allegedly non-existent gravitational waves? If they cannot propagate at c, could they propagate at some other velocity and ontologically sneak in that way?

    3. Florida1920
      1. Louis Savain

        Re: Why LIGO Is a Scam

        "Encyclopedia of American Loons, #1112: Louis Savain"

        And proud of it. A sign that I'm a major pain in somebody's arse. Would not have it any other way.

        ahahahaha...AHAHAHAHA...ahahahaha...

      2. Anonymous Coward
        Anonymous Coward

        Re: Why LIGO Is a Scam

        Yes a very reliable source of information... See for example the entry of a well known actress:

        Mayim Bialik

        Perhaps readers can make their own assessment.

  15. Chris G Silver badge

    Poor sod

    Desperate to be noticed even if only as a Loon,

    I think the American Dad laugh as a signature kinda says it all;

    Not fully with the program.

    But I did notice you Louis.

    1. Louis Savain

      Re: Poor sod

      "But I did notice you Louis."

      ahahahaha...AHAHAHAHA...ahahahaha...

  16. science

    Who confirms what happened millions of years ago?

    For as long as it is impossible to design an experiment that is able to falsify the conclusion that the LIGO-instabilities are caused by colliding black holes, this conclusion remains pure speculation. PLEASE return back to Physics Reality!

  17. science
    Unhappy

    Speculation is not Physics-reality

    For as long as an experiment cannot be designed that is able to falsity the conclusion that the LIGO instabilities are caused by black holes which had collided millions of years ago, this conclusion remains pure speculation. I so which that modern theoretical physicists will return to Physics Reality! They have for more than 100 years build castles in the air and wasted tax payers' money.

  18. Anonymous Coward
    Anonymous Coward

    If two black holes collide in the universe...

    ...and there's no LIGO to detect them, do they make a gravity wave?

  19. tweakpanda

    I like physics .. it is interesting ...

    But every time i read things like "... xxx million dollars for ...", i think:

    Yes ... It is great ... Einstein was right!! Now we know it!! The earth and all life on earth dies ... But we know einstein was right ...Yes!! That was really important ... Why take the money and shelter thousands of childs from starvation, when we can do really important things like astro-physics ... OMFG

POST COMMENT House rules

Not a member of The Register? Create a new account here.

  • Enter your comment

  • Add an icon

Anonymous cowards cannot choose their icon

Biting the hand that feeds IT © 1998–2022