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Physicists Detect Gravitational Waves, Proving Einstein Right

• drelihan 11y ago
  ok, so some of the best minds on Earth can build a machine to detect gravitational waves from an event 1.3B light years away. This is an incredible motivation for those of us on what is possible with technology in simple terrestrial projects.
• pinkrooftop 11y ago
  Would it be possible to listen for information transmitted via gravitational waves? Would there be any benefit over radio?
  • irremediable 11y ago
    AFAIK that doesn't seem at all feasible yet. Currently you need an enormous facility, which struggles to detect anything but the most powerful gravitational waves.
  • CGamesPlay 11y ago
    The amount of energy needed to transmit via a gravitational wave is INSANE. It would involve very rapidly accelerating and decelerating a black hole / neutron star. While it might be possible to do this, it's not within the realm of something we could accomplish without several orders of magnitude technology improvements, and possibly may not be physically possible at all (moving object that heavy that quickly might require creating a black hole)--though I don't have the skill to prove or disprove that.
    • jerf 11y ago
      Even if it were possible, what sort of crazy alien would it take to burn 3 solar masses of negentropy to basically run a ping, compared to the amount of data that could be transmitted with electromagnetic waves with 3 solar masses of negentropy? It's literally dozens of orders of magnitude in difference. Any aliens that are that bad at engineering probably aren't going to grow to the point that they can shake neutron stars several times per second.
      • kamaal 11y ago
        Our power generation stations are the black hole equivalent to the caveman with only access to generating fire through rubbing stones. Based on what level of civilization you are. Rubbing two black holes in for a ping, might be the same as rubbing two stones for a spark. Advanced civilization go really advanced, to a point their activities would be undetectable to us or would appear to us the nature of reality itself.
        • jerf 11y ago
          "Advanced civilization go really advanced, to a point their activities would be undetectable to us or would appear to us the nature of reality itself." This is science fiction, not an argument. We have no rational reason at the moment to believe this is the case, or even possible. What we do in fact have is an increasing trend towards efficiency. Projecting that out along crazy growth curves suggests that advanced aliens are likely to be more horrified by such a waste of negentropy than we are. What can we do with that much negentropy? Nothing, basically. What can they do? Simulate many millions/billions/whoknows of human-level civilizations? They're not more likely to be indifferent about such waste, they're more likely to prosecute you, for mass civilizational murder. I've often thought that if civilization could advance to that point in the future, that I'd have a difficult time explaining to my great-great-great-X grandchildren that when ol' great-great-great-X-grandpa was young, you know, pouring a tank of gasoline into the car got me from point A to point B and that was it, despite it being enough energy in that one tank of gas to, say, simulate an entire human's life time. Well, kids, we didn't have that option! The tech didn't exist. So stop trying to put ol' Greats on trial for things he couldn't control, OK?
          • kamaal 11y ago
            >>This is science fiction, not an argument. We have no rational reason at the moment to believe this is the case, or even possible. There are not only rational reasons, but even evidences to support what I'm trying to say. Look at any insect colony or bacteria, they don't even recognize our presence, let alone our technology. >>What we do in fact have is an increasing trend towards efficiency. Projecting that out along crazy growth curves suggests that advanced aliens are likely to be more horrified by such a waste of negentropy than we are. We the advanced aliens to ants, are indulging waste and plastic pollution like never before. And ants the aliens to bacteria might appear the same. Efficiency and waste are very relative terms based on what level of abundance or austerity on is supposed to live on.
  • omgitstom 11y ago
    I think if you really wanted to think outside of box for this, quantum entangled particles is your best bet for instantaneous low energy communication
    • elektropionir 11y ago
      You can't transmit information through entangled pairs. What is instantaneous is the change of the state for the whole system (the pair) after you measure one of particles. However the result of that measurement (if it's non-trivial, i.e. if the measurement actually changes the state) is fundamentally random so the only thing you would be seeing is perfectly and instantaneously correlated noise on both ends.
    • strange_quark 11y ago
      I'm sorry but no, you cannot transfer information with quantum entanglement. What entanglement says is that if you have a photon and I have a photon and they are entangled and you make a measurement on some attribute of your photon, my photon will assume the complimentary state. However, the state your photon assumes when you measure it is random and once you measure it, you lose the entanglement. So, there's no way for you to encode any information in your entangled photon. Yes, I can infer what state your photon was in as soon as you measure it, this is useful for encryption as we can then compare notes after making a measurement and make sure nobody tampered with our entangled photons.
    • krapp 11y ago
      No it isn't. Quantum entanglement doesn't allow for instantaneous communication[0][1]. [0]http://curious.astro.cornell.edu/about-us/137-physics/general-physics/particles-and-quantum-physics/810-does-quantum-entanglement-imply-faster-than-light-communication-intermediate http://curious.astro.cornell.edu/about-us/137-physics/genera... [1]https://physics.stackexchange.com/questions/78118/quantum-entanglement-as-practical-method-of-superluminal-communication https://physics.stackexchange.com/questions/78118/quantum-en...
  • nickhalfasleep 11y ago
    This event was the equivalent of three of our suns turned into pure energy. Pretty expensive to send a message.
    • yk 11y ago
      Burning a few suns per message would significantly reduce spam.
      • wanderfowl 11y ago
        Your post advocates a ( ) technical ( ) legislative ( ) market-based ( ) vigilante (X) Physics-based approach to fighting spam. Your idea will not work. Here is why it won't work. (One or more of the following may apply to your particular idea, and it may have other flaws which used to vary from state to state before a bad federal law was passed.) (X) The amount of energy involved would likely destroy the planet. (X) Many email users cannot afford to lose business or alienate potential employers Specifically, your plan fails to account for (X) The relative sparseness of non-dark energy in our vicinity (X) Huge existing software investment in SMTP and the following philosophical objections may also apply: (X) Incompatiblity with open source or open source licenses (X) I don't want the government reading my email Furthermore, this is what I think about you: (X) Sorry dude, but I don't think it would work. (I'm sorry, but I couldn't resist)
    • Terretta 11y ago
      > This event was the equivalent of three of our suns turned into pure energy. "The collision unleashed the energy of a billion trillion Suns in a fraction of a second."
      • ascorbic 11y ago
        That's the energy emitted by a billion trillion Suns. The total energy being equivalent to three Suns turned into pure energy.
    • bcook 11y ago
      Yeah, but that was for a message sent across a distance of ~1 billion light-years. I naively assume that shorter distances would require less energy.
  • dragonwriter 11y ago
    > Would it be possible to listen for information transmitted via gravitational waves? Would there be any benefit over radio? Well, if you observe a meaningful, non-natural gravity wave signal, you know that you've discovered not merely another technical situation (which you'd know if you detected the same thing in radio waves), but a phenomenally advanced one. So, if not an advantage, there is at least a meaningful difference.
• pavpanchekha 11y ago
  I remember learning about the LIGO experiment back when it was being built, a decade ago, and at the time it seemed so amazing: a giant tube of vacuum, sealed underground and so sensitive that it could detect animals walking nearby, listening to the moving and twisting of space itself… I guess we're finally seeing that with immense human ingenuity and the most careful of engineering, the universe will offer its secrets up to us. This also means that between LIGO and ATLAS/CMS, the last few years have screwed in the final screws on two of the big physics advances of the 20th century: quantum field theory and general relativity are now both experimentally complete, and both look nearly unassailed in their correctness. The next steps for physics look increasingly abstruse: understanding the exceptional cases, like black holes, holography, and the fundamentally computational form of the universe. It's an exciting time, and it looks more and more like we're close to the very bottom, since we have to look so far now to find anything outside our models.
  • jacquesm 11y ago
    > I guess we're finally seeing that with immense human ingenuity and the most careful of engineering, the universe will offer its secrets up to us. That's been going on for a few hundred years now.
  • fluxquanta 11y ago
    >It's an exciting time, and it looks more and more like we're close to the very bottom, since we have to look so far now to find anything outside our models. For what it's worth we thought the same thing a little over 100 years ago. We just had to figure out a few pesky things like blackbody radiation and physics would be all wrapped up.
    • effie 11y ago
      This is a popular thinking, but actually there were people like Kelvin, Jeans, Rayleigh, Planck and many others who did not get famous who knew there were problems with the theory. In no point in time of modern science there was widespread opinion that "it's mostly done".
  • rubidium 11y ago
• lobster_johnson 11y ago
  Dicussed here: https://news.ycombinator.com/item?id=11079462 https://news.ycombinator.com/item?id=11079462
  • tfgg 11y ago
    To be fair, that article is pre-announcement and doesn't have much detail on the actual discovery. Actual paper here: http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.061102 http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116...
• losvedir 11y ago
  > And then the ringing stopped as the two holes coalesced into a single black hole, a trapdoor in space with the equivalent mass of 62 suns. All in a fifth of a second, Earth time. Am I reading this correctly, that shortly after the detector came online we just happened to observe the exact moment a billion years ago that two black holes collided? Was that extremely coincidental? Or do these events happen all the time, and so if it wasn't those two black holes it would be two others?
  • hcrisp 11y ago
    They state in the article that four events were detected during the engineering run. In the future tens of events could be detected per year.
  • dragonwriter 11y ago
    > Was that extremely coincidental? Or do these events happen all the time, and so if it wasn't those two black holes it would be two others? From the article, no one knows: "Black holes, the even-more-extreme remains of dead stars, could be expected to do the same, but nobody knew if they existed in pairs or how often they might collide. If they did, however, the waves from the collision would be far louder and lower pitched than those from neutron stars."
  • antognini 11y ago
    The predictions for the LIGO detection rate are very poor. They're based on a sample of just a handful of binary pulsars observed in our Galaxy, which would produce NS-NS mergers. The BH-BH merger rate is almost totally unconstrained, although it is generally thought to be less than the NS-NS merger rate. So the fact that a BH-BH merger was the first detection, and the fact that it was detected so soon after the sensitivity increases is evidence that the BH-BH merger rate is probably somewhat higher than expected. But we won't know for sure until LIGO detects more events and the rate can be better constrained. Sometimes you do just get lucky. I should add that there are lots of selection biases and educated guesses in all of this, too. The signal from BH-BH mergers is louder and easier to detect from larger distances. At the same time, NSs are probably more common than BHs, but it's not really clear whether there are more NS-NS binaries than BH-BH binaries because NSs receive kicks from the supernova when they are born but BHs (probably) do not. This may have the effect of blowing apart many nascent NS-NS binaries but leaving the BH-BH binaries intact.
• chrismbarr 11y ago
  For someone like me who knows next to nothing about this, that video was extremely well produced and it explained everything i was wondering about.
  • tptacek 11y ago
    Jonathan Corum has had a fun career to watch; he's (I think?) a student of Tufte's. I discovered him with brunch.org; also, check out his style.org.
• rdli 11y ago
  Live stream from the NSF: https://www.youtube.com/user/VideosatNSF/live https://www.youtube.com/user/VideosatNSF/live
• elorant 11y ago
  Are gravitational waves supposed to be that weak or is it because of the distance between us and those black holes? Do they lose power as they travel through space?
  • jonknee 11y ago
    Yes, like all waves they fade over distance. But an event that happened a billion years ago moving stuff around on Earth is still pretty impressive!
  • kordless 11y ago
    Think of waves in a pond when you drop a rock in. The energy spreads out as it travels into the farthest reaches of the pond.
    • davrosthedalek 11y ago
      Only that in space, it drops even faster: The wavefront carries the same energy, but spread out over ever increasing length/area. For gravitational waves (or radio waves) they form spheres, not circles, and the surface size scales with r^2, not r. (Also water waves are /complicated/)
      • bzbarsky 11y ago
        Right, but LIGO detects wave amplitude, not wave energy, which goes down as 1/r.
        • davrosthedalek 11y ago
          Oh, interesting point! I now have to wrap my head around that information transfer normally means energy transfer...
  • dragonwriter 11y ago
    > Are gravitational waves supposed to be that weak or is it because of the distance between us and those black holes? Distance. A billion light-years is a very long distance, and the inverse-square law applies.
• kachnuv_ocasek 11y ago
  Paper here: https://dcc.ligo.org/LIGO-P150914/public https://dcc.ligo.org/LIGO-P150914/public
• 4k 11y ago
  I have a question: what does this mean for theoretical physics? (except for Einstein was right) Does it settle any major debates? Does it make any competing theory more or less likely? Sorry I am not vary knowledgeable on the topic.
  • nickhalfasleep 11y ago
    On the webcast, they described how this let us listen in on massive disruptions of space-time, environments we could never create to test on earth, and that could help us better compare our models to events seen in extreme cases.
  • Steuard 11y ago
    It's by far the most explicit verification we've ever had that black holes exist in pretty nearly the exact form predicted by Einstein's equations of general relativity, which is pretty cool. It provides the tightest limits on any possible mass for the graviton (the presumed particle carrying the gravitational force, which is generally believed to be massless but you always have to wonder about more exotic possibilities). It gives a stunningly clear confirmation that modern numerical simulations of relativistic dynamics are an accurate reflection of nature. (And by the same token, it presumably puts limits on the strength of any potential deviation in the laws of physics from the equations used in designing those simulations.) And it probably does something to give preference to models of astrophysics in which binary systems with these characteristics are common. Beyond that, I guess I'd say that this particular signal doesn't feel like that much of a surprise: we were already pretty confident that if a black hole binary were to merge, a signal more or less like this would be an expected result. The scientists were evidently surprised that their very first signal was so strong (this one was even borderline detectable by the previous version of LIGO), which may teach us something, but it's not revolutionary.
  • thisrod 11y ago
    This is the result the theories predicted, and there's nothing for the theorists to do except gloat. If people had kept building more sensitive detectors, and kept failing to detect gravity waves, then eventually that would have been a very big deal for theoretical physics. But it didn't happen. On the other hand, there is now a way to see dark matter. That could enable a lot of new astronomy.
• oldmanjay 11y ago
  A detector of this sensitivity seems like a boon for spying. Rather difficult to relocate, fortunately, but it makes me wonder about the future of the technology. No one would have looked at the first computer and envisioned an iPhone.
  • shmerl 11y ago
    > No one would have looked at the first computer and envisioned an iPhone. Not really. Portable computers were envisioned quite a long time ago.
    • oldmanjay 11y ago
      Not before they were solid state. Computers had their own buildings and relied on glass tubes for operation. Screens weren't on the radar. Operators were highly educated. But technology did bring us to a point where the vision became more focused, and led to what we have today. There are many possible paths to rebutting my statement, which to be clear is idle morning musing, but your objection doesn't hold water.
      • nitrogen 11y ago
        Is your speculation that the gravity wave detectors would be able to detect the changes in gravity caused by movements of people and things? Submarines already do this to detect other vessels AFAIK.
        • bbcbasic 11y ago
          Surely you are thinking of Sonar?
          • nitrogen 11y ago
            No, this came up on Hacker News recently: https://news.ycombinator.com/item?id=10810390 https://news.ycombinator.com/item?id=10810390
• exodust 11y ago
  I wonder if gravitational waves are responsible for the video starting automatically without me clicking play.
  • mikeash 11y ago
    Yes, in that any given event is ultimately the result of all previous events within its past light cone.
• jshelly 11y ago
  Does anyone else get a bit depressed when you consider how insignificant we are?
  • pklausler 11y ago
    Nah, it's more of a feeling of liberation from unreasonably high expectations.
  • venomsnake 11y ago
    No. But with so much interesting things left to find I start to really really hate the concept of mortality :(
    • grif-fin 11y ago
      I could not agree more. Everyday I wake up and I think why is it that we gave up on massive wave of research on immortality/life extension.
  • eecks 11y ago
    It just depresses me that I'll never reach an Einstein standard in any thing I do :/
    • readme 11y ago
      Not with that attitude!
  • chriswarbo 11y ago
    What makes you think we're insignificant? Maybe it's the psychology of how we (fail to) deal with different scales. Discovering new, larger, more wonderful places in the Universe doesn't make the Earth any smaller or less wonderful than it is. Our brains might "zoom out" our mental map to fit these new places in, which makes us appear smaller, but in fact it's our horizons that have grown. According to https://en.wikipedia.org/wiki/Books_published_per_country_per_year https://en.wikipedia.org/wiki/Books_published_per_country_pe... there were nearly 200,000 books published in the UK in 2011. That doesn't make the works of Shakespeare insignificant.
• scrumper 11y ago
  From the abstract of the paper, energy equivalent to three solar masses were radiated away in gravitational waves. That's a simply incredible amount! Possibly stupid question: Given how far away it was, and that the inverse square law applies, would the effect of these waves be visible on the human scale if we were closer? We can see the effects of the compression of spacetime with LIGO after all, so presumably we could?
  • Semiapies 11y ago
    Yeah,I got to the point mentioning the masses of the black holes before and after collision and said, "What, they didn't just lose three solar masses..." But, they did. Which was the order of predictions I'd read, years back, but egads. Considering how much larger that is than a supernova, I'd be concerned to have such an event happen in this galaxy...
    • mturmon 11y ago
      Yes, mind-boggling. 3 solar masses converted to energy in just a few seconds.
      • adrianN 11y ago
        0.5 seconds actually.
    • pja 11y ago
      The energy is dumped into gravitational waves rather than electromagnetic radiation & they don’t interact with matter much. I’m not sure you’d notice it happening in the same galaxy unless you were looking for it.
      • deleted 11y ago
        [deleted]
  • bzbarsky 11y ago
    This thing was a billion light years away. Say it were closer; let's put it at a single light year away. LIGO measures wave amplitude, as far as I can tell, which goes down linearly with distance (unlike wave energy, which goes down quadratically, since it's proportional to square of the amplitude). So we could expect to see an effect about a billion times bigger. The detected effect was a change in metric of one part in 6e20 if I'm not mistaken: (4e-3 * (diameter of proton))/4km based on the article's claim of "four one-thousandths of the diameter of a proton". So at one light year distance we could expect an effect of one part in 6e11. Not really visible on the human scale, seems to me. You could detect it easily with something like the Mössbauer effect, I expect. Your typical lab bench laser interferometer has errors on the order of 1 in 1e6 as far as I can tell, so probably wouldn't be able to pick this up. Disclaimer: I could be totally off on what a lab bench laser interferometer can do. I'm pretty confident in the rest of the numbers above.
• Roodgorf 11y ago
  Are there any potential competing theories this detection could also support? I'm wondering how much room there is here for confirmation bias, but I suppose that's a pretty hard thing to measure without the benefit of hindsight.
  • Steuard 11y ago
    Even before this discovery, it's been pretty solidly established that any alternative theory to General Relativity would need to behave essentially identically to GR in the limits where we've been able to test it. So, for example, the "low energy limit" of string theory is general relativity (plus other content, in most cases). I'm not sure whether the loop quantum gravity folks have a working low-curvature limit yet (I'm out of touch), but that would be a requirement for them, too. At first glance, I'd guess that this discovery only strengthens that conclusion: even a small deviation from GR might well change the detailed behavior of an immensely high curvature situation like a black hole merger, and what we saw seems to have been a spot on match for the GR-based models.
    • davrosthedalek 11y ago
      Well, they extracted a lot from the waveform: Distance, the two masses, the resulting mass. I could imagine that a competing theory gives the same waveform maybe with different values for these parameters.
      • pdonis 11y ago
        A "competing theory" would first have to match the GR predictions in all the other regimes where it's already been tested. But doing that is an extremely strong constraint on a theory, to the point where the only theory that can meet it is GR itself. Physicists know this because alternative theories to GR have been constructed and tested, and they have all failed. See, for example, here: https://en.wikipedia.org/wiki/Alternatives_to_general_relativity#Results_of_testing_theories https://en.wikipedia.org/wiki/Alternatives_to_general_relati...
• kamaal 11y ago
  Tangential question. With blackholes merging, can more and more merge some time in future, creating a net gravitational pull to slow down the expansion of the universe and then may be eventually cause the universe to collapse into that continually merging mega black hole.
  • macintux 11y ago
    Nope. Gravity is vastly too weak, black holes are far too rare. Consider that major galaxies (apparently all of them?) have a massive black hole at the center, yet those galaxies aren't collapsing in on themselves.
  • gus_massa 11y ago
    The gravity pull of the new black hole is essentially equal to the sum of the gravity pull of the two isolated black holes, and it's essentially equal to the gravity pull of the two stars before they transformed into black holes. So merging black holes don't increase the pull. Actually, in each transformation there is an explosion and part of the mass goes away (try to not be very close). So the total mass in the final black hole is smaller than the mass in the initial stars, the rest are debris forming a nebula or something around the black hole. (And, as the other commenter said, gravity is too weak.)
• known 11y ago
  Everyday we're getting sun rays https://en.wikipedia.org/wiki/Crepuscular_rays https://en.wikipedia.org/wiki/Crepuscular_rays Why are we surprised at gravitational waves when 2 black holes collided?
  • delecti 11y ago
    We actually aren't surprised. This confirms a theory we've been reasonably confident about for about 100 years. This is less "wow, look at what an unexpected result we found!" and more that we finally managed to measure something we've been looking for.
    • macintux 11y ago
      Not only expected, but the predicted wave forms were virtually perfect. We knew what to look for, and we even knew what we saw as soon as we saw it.
• IanDrake 11y ago
  Is the speed of light affected by the gravitational fluctuations mentioned in the article? Or, put another way, is the speed of light only a constant because we measure it in constant gravity?
  • delecti 11y ago
    Any observer will observe the same speed of light in their location. Any effect of gravitational fluctuations in spacetime on the speed of light is a bit like a car driving on a race track that has treadmills scattered around it pointing in various directions and speeds. The car's speedometer will always read the same value because it's measuring the speed of its tires on whatever it's driving on.
• ericjang 11y ago
  The mechanical and software engineering underlying these research endeavors is breathtaking. The laser apparatus, LISA pathfinder, ELISA - how on earth do they calibrate/debug/test such complex systems? ... and I shudder to think that more often than not, anything I code in C/C++ will segfault on first run.
  • iDemonix 11y ago
    As someone who has spent the day trying to get a web app to run, wrestling with Perl dependencies, I feel the same.
  • pif 11y ago
    Don't worry, their code segfaulted umpteen times, too :-)
• spullara 11y ago
  As with most physics experiments for the last 40 years, nothing new was discovered that we didn’t already predict. Confirming something widely believed to be true isn't nearly as valuable as finding out we don't understand something. This is actually one of the reasons I dropped out of my physics phd program.
  • bobinator606 11y ago
    Then you should have concentrated on theoretical physics instead of experimental?
  • gammarator 11y ago
    Because this is astrophysics and not particle physics, this discovery is just the beginning! We don't know the rates of these mergers, the distribution of the masses of the binary components, what electromagnetic signature accompanies the events (if any)... We've known gravity waves existed since the Hulse-Taylor pulsar, so just observing them for the first time is not nearly as interesting as the science to come in the next decade. Advanced LIGO is a powerful new tool that will open up exciting new observations.
• QuadrupleA 11y ago
  One thing I don't quite understand - how can the "chirp" from LIGO be unambiguously categorized as extraterrestrial in origin? The waveform shown onscreen in the NYtimes video looks like an extremely noisy signal - not sure if that's the actual sampled data or just an artistic rendition. Couldn't there be a variety of physical disturbances that explain a sine-tone sweep like that, given how sensitive the instrument is to physical vibrations?
  • cft 11y ago
    There are two independent sites, 2000 miles apart. Additionally, each site has two perpendicular experiments: one shows contraction when the perpendicular one shows expansion. Orientations at both sites are aligned I presume.
    • bobinator606 11y ago
      And there is a third which was offline at the time, and 2 more being worked on. This is no the last experiment.
• nilkn 11y ago
  I hope Kip Thorne gets a Nobel Prize for this, ideally while he's still alive.
  • mikeyouse 11y ago
    Pedanticly, it'd have to be while he was alive since the Nobel Committee won't nominate anyone who's deceased. Rosalind Franklin would've surely received one for her work on DNA (among others who passed before their work was recognized).
• ttflee 11y ago
  How could this result be reproduced in an independent repetition, then?
  • astrosi 11y ago
    In a very real way it was. There were two completely geographically separate instruments which recorded the same signal with a delay that is consistent with the light travel time between them. In the future this will get better when VIRGO in Italy and KAGRA [2] in Japan come online. Then we will have 4 independent detectors which will be able to verify that same signal is observed at the same time. Obviously of course given the transient nature of what is being observed once the merger has occurred it will very rapidly stop producing gravitational waves so we will not be able to measure the same event again. [1]: https://en.wikipedia.org/wiki/Virgo_interferometer https://en.wikipedia.org/wiki/Virgo_interferometer [2]: https://en.wikipedia.org/wiki/KAGRA https://en.wikipedia.org/wiki/KAGRA
• giomasce 11y ago
  I really wonder what the researcher sitting bored at their computer looking at random data thought when they noticed the interesting event!
  • akuchling 11y ago
    http://www.sciencemag.org/news/2016/02/here-s-first-person-spot-those-gravitational-waves http://www.sciencemag.org/news/2016/02/here-s-first-person-s... " On 14 September 2015, while Drago was on the phone with a LIGO colleague in Italy, his pipeline sent him an email alert—of which he receives about one each day—telling him that both LIGO detectors had registered an “event” (a nonroutine reading) 3 minutes earlier, at 11:50:45 a.m. local time. It was a big one. “The signal-to-noise ratio was quite high—24 as opposed to [the more typical] 10,” he says."
• peter303 11y ago
  Note this is a stellar black hole merger of several tens of solar masses. Imagine the disturbance of a galactic core black hole mergers of millions of stellar masses. These are probably much rarer, but do occur when galaxies merge.
  • swombat 11y ago
    Oooh, I can do another back of the envelope calculation here! (cf https://news.ycombinator.com/item?id=11081838 https://news.ycombinator.com/item?id=11081838 ) If this happened in the centre of the Milky Way, we're about 25k light years away. Let's say 2 1 million solar masses black holes merged there... and they also gave off about 3/60 of their mass as radiation, that's about 100'000 solar masses being radiated 25k light years away. Using my calculation in the other post, we're talking 10^52 Joules. Across a distance of 25'000 light years, or about 10^20 metres, that's then decreased by 10^40 (inverse square) so we're left with about 10^12 Joules... Which is good news! If that happened in the Milky Way, we would probably survive it - though we'd definitely notice some strange atmospheric effects...
• xCathedra 11y ago
  Could someone explain what possible applications this might produce?
  • ddingus 11y ago
    It's super early, and detection seems at the limits of our technology. This is just understanding at present. That, in itself is worth it. As that understanding develops, and our tech advances, engineering may be able to apply it in useful ways, maybe object detection above a specified mass? New ways to visualize things? One "application" is to serve as a ruler to measure out tech with. The limits are there, putting these observations just within reach. Now that we have some confirmation, we also have the metrics as well as the compelling new science that may arise from all of this as a strong motivation to advance. It's like being able to detect color for the first time. At first we understand what color is, then we refine, and after iterations, engineering, experiments, we get to a place where we see it all in color. Applications will follow. These waves being confirmed are like a new sense. Crude, but real. We can now follow this new perception to its conclusion, just as we have many other things. We don't always know what that conclusion will be, or the form an application may take, but we do know we won't actualize any of it if we don't do the basic, hard, expensive work needed first.
  • 77pt77 11y ago
    Directly from gravitational waves, absolutely nothing. Indirectly from the technology they had to develop to measure this, possibly something specially due to the precision they needed to measure this.
• soneca 11y ago
  Honest question: there is any example of Einstein being proved wrong? Was he indeed always right on his theories for phenomenons before they could be proved by experiments; or is that the case that we only hear about when he is proved right?
  • marcoperaza 11y ago
    He was a proponent of hidden variable theory, which tried to reconcile quantum mechanics with determinism, famously saying "God does not play dice". People often say that hidden variable theories were proven impossible, and thus Einstein was proven wrong. That's not quite true, and only local hidden variables have been ruled out.
    • lamontcg 11y ago
      It also disparages his contribution to the scientific discussion to just state that he was "proven wrong". Bohr's argument in the discussion was a bit of a mess and I couldn't pull anything out of his rebuttal to EPR other than an assertion that QM behaves the way it does and not to pay any attention to the man behind the curtain. Its a very philosophical argument with very little scientific content and he just proposes that the QM math is correct because its correct, as far as I can tell. EPR made a logical cogent argument. It was based on the philosophical principle of the locality of physics. They translated that into the mathematics of Quantum Mechanics and proposed a simple experimental test. Later that was refined by Bell and tested experimentally by Aspect and others. It was the Einstein-Podolsky-Rosen paper that laid the groundwork of how to test the non-locality/hidden-variables of QM though. EPR moved the scientific discussion forwards much more than Bohr did, but it turns out the test they proposed showed that the position they favored was incorrect. Also Einstein was arguing first and foremost that physics must be _local_. That's in opposition to the "spooky action at a distance" bit that he didn't like. Since local hidden variables are ruled out then he really was proven "wrong". TL;DR I think Bohr's argument is rubbish, and Einstein's is solid, but the Universe is a bitch and doesn't care...
    • nanofortnight 11y ago
      Non-local hidden variable theories are viable, however, such as de Broglie–Bohm. I don't think Eistein would've liked those much either due to 'spooky action at a distance'.
• brudgers 11y ago
  I am a bit skeptical of the conclusion given the methods. Here, there's no observable phenomena independent of the test apparatus that corresponds to the proposed cause. The conclusion is circular. 1. Theory predicts gravitational waves when massive objects collide and that the gravitational waves would have an effect that could be measured by the experimental instruments. 2. The experimental instruments measure something. 3. This is considered proof that massive objects collided. 4. Therefore gravitational waves exist. To reframe my skepticism, the experiment measures something. The conclusion as to what it measures, however, is unsupported by statistical inference or direct experience of a causal phenomenon. That's not to say that what the phenomena measured -- the earth resonating -- is uninteresting or unimportant or even inconsistent with the theory of gravitational waves. Yet, I don't find the possibility of a geophysical cause -- i.e. that the earth maintains consistent dimensions at a sub-atomic scale -- the many orders of magnitude less likely than gravitational waves necessary to reach a conclusion. In particular, I find natural fluctuation to be more likely because the experiment acknowledges its existence. For a point of comparison, consider the Perihelion precession of Mercury that provides evidence in support of general relativity. The theory was used to predict the results of an observable event. The experimenters trained their telescopes at a particular location and particular time and observed phenomena consistent with a prediction based on the theory. The same is true of the Higgs. In both cases the experiment is of the form "when X, I will observe Y." The reasoning here is: If X, then Y. Y, therefore X. It treats an ordinary implication as mutual implication.
  • iso-8859-1 11y ago
    A common logical fallacy: https://en.wikipedia.org/wiki/Affirming_the_consequent https://en.wikipedia.org/wiki/Affirming_the_consequent
  • gaur 11y ago
    > That's not to say that what the phenomena measured -- the earth resonating That's not what the detector measures. RTFA.
    • dang 11y ago
      > RTFA Please don't be rude like that here. It breaks the HN guidelines: https://news.ycombinator.com/newsguidelines.html https://news.ycombinator.com/newsguidelines.html Your comment would be fine without that bit, and better still if it stated briefly what the detector does measure.
• nappy-doo 11y ago
  Does anyone know if G-Waves are effected by velocity, like EM-Waves are? In other words, if two bodies are moving relative to one another, one emits G-Waves, and one detects them. Are the waves at the detector doppler shifted in frequency by the relative velocities?
  • lutorm 11y ago
    I don't see how they could not be. I think that shift arises from transformations between different coordinate frames, it doesn't matter what you're observing.
  • simcop2387 11y ago
    As they're supposed to be traveling at the speed of light I'd jump to the conclusion that you'd find them doppler shifted. In this case though we don't yet have anything like the spectral lines of hydrogen to be able to measure that shift so I don't think we can do anything with it yet.
• jstalin 11y ago
  Does gravity move at the speed of light?
  • ddingus 11y ago
    The videos say the waves do move at exactly the speed of light. They are massless.
• goshx 11y ago
  This is live now: https://www.theguardian.com/science/across-the-universe/live/2016/feb/11/gravitational-wave-announcement-latest-physics-einstein-ligo-black-holes-live https://www.theguardian.com/science/across-the-universe/live...
• boardwaalk 11y ago
  If they build a third observatory, can they triangulate where in the universe the events are occurring?
  • stouset 11y ago
    My intuition is that this is unlikely, but I'd love to see someone do the math. Given the scale of interstellar distances, any locations on our planet (and even in our solar system) are going to effectively function as a single point. Given arbitrarily-accurate measurement, it could work, but I'd bet physical limitations will prevent that from being a possibility. To my mind, it'd be roughly like trying to triangulate an earthquake in France with three sensors in a 1mm^3 cube in NYC (scale is probably way off, I definitely didn't do the math).
    • Florin_Andrei 11y ago
      It would work. The delta-t is a few miliseconds. This gives enough precision for a decent estimate of the direction of the signal. Now estimating the distance is a different matter.
      • swamp40 11y ago
        The gravity waves redshift just like any other wave. So, they have estimated a distance: 1.3B light-years.
      • stouset 11y ago
        I think we're on the same page; I was referring to triangulation, which would give the distance and not just direction.
    • lutorm 11y ago
      It definitely would work. The distance to the event is irrelevant, it's the light travel time between the detectors compared to the accuracy with which you can pin the event down in time that matters. The light travel time across the Earth is of order a hundredth of a second, which is a significant fraction of an event that takes ~ a tenth of a second. However, the error ellipse will probably be quite larg, and given that they come from cosmological distances it's unlikely that they would be anything but isotropically distributed (like gamma ray bursts are).
• hiphopyo 11y ago
  Does this bring us any closer to warp drives?
  • ingenter 11y ago
    No, because "warp drives" in the sense of "Alcubierre drive" requires negative mass, which is not observed anywhere.
  • drdeca 11y ago
    Uh, I guess it might help with testing things that would? Iirc the idea would be that inferometers would be used to test things like that. I don't think we (humanity) will achieve warp drives, though, I do support the attempt.
• msie 11y ago
  So does this verification of gravitational waves help with Physics theory-building? Have people really doubted Einstein : the existence of gravitational waves?
• jharohit 11y ago
  For those who missed the live announcement by the team https://youtu.be/aEPIwEJmZyE?t=27m13s https://youtu.be/aEPIwEJmZyE?t=27m13s
• frandroid 11y ago
  > The future for the dark side looks bright. Oh no you didn't.
• amai 11y ago
  Wow, the list of authors to the paper is three pages long: https://dcc.ligo.org/public/0122/P150914/014/LIGO-P150914_Detection_of_GW150914.pdf https://dcc.ligo.org/public/0122/P150914/014/LIGO-P150914_De...
• stevebmark 11y ago
  How do the detectors work? In my mind they don't make physical sense. They're saying the distance between the mirrors changes, but I don't understand how that's possible in this context. Let's say a gravitational wave compresses space. To someone inside that compressed space, there should be no noticeable difference. Light will still flow the same way through the compressed space at the same speed relative to the compression. Matter will behave identically, because both light and matter are part of the fabric of that space. As I understand it, the only way the mirror lengths could change is if space is created or destroyed. If that doesn't make sense, consider the 2d analogy of drawings living on paper. Assume also that light moves only along the surface of the paper. If you bend the paper, the light will bend with it. But when you bend the paper, the creatures living on the paper can't know it's bent. The fabric of the paper is still identical. Even if some of the paper gets compressed in one direction, it will still have the same amount of particles, so any light travelling through there will hit the same amount of resistance. And stretching the paper, even if you're a drawing on the part being stretched, would have no effect. A 2d creature looking at something 1 foot away, even if the paper is stretched to 10 feet, won't see any difference, because the fabric light travels through is also stretched. The only way I can see this making sense is if light travels independent of the fabric of space, but it's my understanding that light travels through it, not independent of it?
  • yosyp 11y ago
    I think the crucial detail you are missing from the article is this: "According to the equations physicists have settled on, gravitational waves would compress space in one direction and stretch it in another as they traveled outward." LIGO is two sets of 2 L-shaped antennas spread far apart on the globe, so that we can compare the compression of space in orthogonal directions and measure the very short delay between the gravitational wave hitting the first detector followed by the second. In this case, that difference was 7 milliseconds, which is also consistent with the speed of gravitational waves (also the speed of light)
    • stevebmark 11y ago
      I still don't understand. It doesn't matter where the compression happens, because it should be undetectable to any light/matter that's fundamentally a part of that space? If one of the arms gets compressed - the matter will be compressed too, so light still has the same density and amount of space to travel through?
• ScottBurson 11y ago
  This made me wonder how far we are from being able to create and detect gravitons. The Wikipedia page on gravitons [0] addresses this question: Unambiguous detection of individual gravitons, though not prohibited by any fundamental law, is impossible with any physically reasonable detector. The reason is the extremely low cross section for the interaction of gravitons with matter. For example, a detector with the mass of Jupiter and 100% efficiency, placed in close orbit around a neutron star, would only be expected to observe one graviton every 10 years, even under the most favorable conditions. [...] However, experiments to detect gravitational waves, which may be viewed as coherent states of many gravitons, are underway (such as LIGO and VIRGO). Although these experiments cannot detect individual gravitons, they might provide information about certain properties of the graviton. For example, if gravitational waves were observed to propagate slower than c (the speed of light in a vacuum), that would imply that the graviton has mass [...]. Fascinating! I take it that the question of whether the graviton could have mass is now considered to be well answered in the negative. [0] https://en.wikipedia.org/wiki/Graviton https://en.wikipedia.org/wiki/Graviton
  • sandworm101 11y ago
    If gravitons have mass, then the universe is too strange to exist. Gravity is an interaction that defines the presence of matter (see dark matter). For the object that transmits that force between masses to itself have mass ... how can a black hole then project gravity? Imho whatever is carrying gravity between masses cannot itself have a mass.
    • TrainedMonkey 11y ago
      Gravitation does not technically interact with light either, but rather bends the spacetime the light travels through. So question is, what makes gravitons different?
      • noobermin 11y ago
        I'm a physicist, but in a different field, but my (possibly incorrect) impression is what a quantized particle is is a bit mysterious when the field is strong, for example, with lensing. Best example: the Hydrogen atom is supposedly quantum, but if it is quantum, where are the photons? the q^2/r potential is a mean field that one finds from classical electrodynamics, it isn't formed by the summation of photons. [Another mental poker, photons are momentum eigenstates, so how can potential be described in position space? You'd need to sum up an infinite number of them! (For EM students, recall how to represent 1/r in spherical harmonics or in terms of sines and cosines)] What happens, as I understand it, is with strong fields, one tends to use a semi-classical description because in the strong field limit, one deals with many photons, which should approach the classical limit. Basically, quanta are like "pertubations" of the fields from their "free" solutions, as they are in GR (linearization of the GR field eqns) and as they are in EM. Free essentially means in the absence of sources, like charges, or masses for GR. So trying to explain general phenomena in terms of "pertubations", which are basically the solutions for "free" fields, is not always fair. One doesn't always face this in high energy physics because in HEP, most of the incoming and outgoing states in a problem are these "free" solutions. For example when doing scattering off a hydrogen atom, the incoming states are "free" (a free nuclei, a free electron), so one can use photons for that phenomena, and one finds that the scattering is like scattering against a (mean) 1/r potential. But in the case where the strong fields don't turn off, like when you are bound to a Hydrogen atom, or when considering nucleons in nuclei in the low energy limit, one turns away from the pertubative, photon/gluon model and either solving the problem numerically or treats the fields as semi-classical, as with the Hydrogen atom. For my field of laser-plasma physics, this shows up in the so-called "Volker-state", rather than treating the strong laser field as a sum of innumerable (ie., not-simulatable) photons, one treats the Laser field as a semi-classical background for the quantum guys (electrons, ions). I think lensing is like strong static fields in EM. One wouldn't really think of them in terms of quanta of the field.
• amai 11y ago
  On November 25, 1915 (at the time of WWI) Einstein presented the actual Einstein field equations to the Prussian Academy of Sciences. Almost exactly 100 years later on September 14, 2015 LIGO observed the first gravitational-wave signal. Is that a coincidence?
  • flexie 11y ago
    Yes
  • bobinator606 11y ago
    No. Spooky Action at a Distance.
• jcoffland 11y ago
  I wonder of this means the space version of these antennas, eLISA, will get more funding. Using space seems like a much better way to access long distance laser conduits in a vacuum needed to detect gravitational waves.
  • gammarator 11y ago
    Since the LISA has longer baselines, it measures gravitational waves of different frequencies, from different phenomena--supermassive black hole coalescence, not these (mere!) stellar mass black holes. So the experiments are complimentary
• swehner 11y ago
  The "proving Einstein right" part would be more fitting if there was some independent evidence of the collision. As it is it seems to go in circles. But that's the NYT I guess.
  • sandworm101 11y ago
    Maybe we will get lucky and literally see two black holes merge somewhere nearby. But I think these detectors will be the last of our concerns with all the praying and bunker building going on. Bruce Willis won't save us from that one.
  • swehner 11y ago
    why was this downvoted?
• ernesto95 11y ago
  I generally dislike idolatry and pinning mayor scientific advancement on one single person, but honestly, Einstein really was something else.
  • dheera 11y ago
    In all honesty I do think Einstein is getting too much credit today. I'd paste the list of co-authors here to congratulate them but HN doesn't allow comments that large. The list is available here for reference, and I think every one of them deserves credit for this. http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.061102 On another note, I feel like the importance of this finding is less in proving Einstein's theory; having taken a formal relativity class and an degree in Physics, I think GR itself is an astounding mathematical framework for describing spacetime, to which Einstein deserves credit, but the existence of gravitational waves is completely natural consequence of the equations within. It's not very different from the existence of light being a natural consequence of Maxwell's equations. I'd say the true importance of this discovery is in successfully creating an experimental apparatus to detect what was previously almost universally agreed to probably exist but thought to be nearly impossible to detect. What's truly exciting isn't proving Einstein right, but the possibilities of what we'll be able to to detect with this apparatus in the future. So it's the team that built the apparatus which truly deserves the credit today.
• hendekagon 11y ago
  Has anyone converted the spectrograms given in the paper, or better still the raw data, into sound yet ? Each location in each ear please!
  • astrosi 11y ago
    The data release contains the data converted to sound if you scroll to the bottom [1]. I don't think anyone has combined them as you suggest though! [1] https://losc.ligo.org/events/GW150914/ https://losc.ligo.org/events/GW150914/
• kkylin 11y ago
  A conceptual issue that some of the commenters may have missed is that part of the detection is done by matched filtering (https://en.wikipedia.org/wiki/Matched_filter https://en.wikipedia.org/wiki/Matched_filter), in which it is necessary to have a good idea of the signal you're looking for. This detection has built upon analytical and numerical advances in relativity. While people may not know about the prevalence of e.g. binary black hole collisions, they have a pretty good idea of the signal that would result if such a collision were to occur. Similarly with other potential sources like binary neutron star collisions.
  • auntienomen 11y ago
    Yeah, too many LHC reports have primed people to expect counting experiments where the scientists struggle to get to 5 sigma. The waveforms we're talking about here have a signal to noise ratio over 20.
    • rattray 11y ago
      Sorry, what does that ratio imply?
      • tempestn 11y ago
        That one can be very confident the effect observed was real.
      • Gibbon1 11y ago
        I'm assuming that the same rules apply as do in straight RF detection. A signal becomes a decent signal at 6db above noise and gets exponentially better every 6db above that. Something 20db above noise is rock solid reliable.
        • im3w1l 11y ago
          Uhh, 20db isn't the same as 20s/n ratio though?
• josephv 11y ago
  I swear a big bang theory rerun about this was on last night. Sheldon detected waves at the north pole, but they were actually a blender turned on by the rest of the gang. He's embarrassed and goes home. Leonard beds Penny. Decent episode.
• aabbccdd 11y ago
  I'm wondering no-one mentioned Electric Universe which is the greatest opponent of this gravitational hocus-pocus religion. It would be much more beneficial to the humanity to focus smart peoples' attention to Birkeland currents or plasma or to the recent experiments of the SAFIRE project. They have several series on their youtube channel: https://www.youtube.com/user/ThunderboltsProject/videos https://www.youtube.com/user/ThunderboltsProject/videos
  • vecter 11y ago
    You ... must be trolling.
• pkrumins 11y ago
  Can't wait until this discovery can be utilized to creating some kind of a new technology! Such as time travel!
• JabavuAdams 11y ago
  Where can I find out more about how thermal effects in the LIGO optics are controlled for? Basically, I want to understand how it's possible to measure a distance change on the femtometer scale.
  • selimthegrim 11y ago
    You probably want to read about their active isolation measures. Then you should find anything by Vladimir Braginsky you can get your hands on. This is a good start: http://www.amazon.com/Quantum-Measurement-Vladimir-B-Braginsky/dp/0521484138 http://www.amazon.com/Quantum-Measurement-Vladimir-B-Bragins...
    • JabavuAdams 11y ago
      Great! Thanks. My local university has this.
    • JabavuAdams 11y ago
      More accessible / concise info on the vibration isolation, here: https://news.ycombinator.com/item?id=11084282 https://news.ycombinator.com/item?id=11084282
• wuliwong 11y ago
  I am not sure why but I am really hung up on the quote “Finally, astronomy grew ears. We never had ears before.” They are detecting gravitational waves not sound waves.
  • swamp40 11y ago
    The interference pattern is audible - a chirp that "rose to the note of middle C".
    • wuliwong 11y ago
      Interference patterns from two lasers do not make any sound. You can take data describing the interference pattern and convert it to a signal that is run through a speaker but that doesn't mean the interference pattern is audible. The amazing thing is they detected gravitational waves, not that they hooked up a speaker to the data. I think a proper analogy would be if back when someone created the first function generator they connected it to a speaker. Then in an interview the main message they delivered was that you could now "hear electricity." It just seems like they are focusing on an afterthought. I also have no idea why I am so fixated on this. :-p
  • fsloth 11y ago
    Any vibration is just a signal. We don't actually have a direct experience with a sound, hearing is our brains interpreting the nerve signals generated by tiny organelles jiggling in our ears. What is concrete then, is only the shape of the signal, but not the medium through which it propagates. This device just acts like a gigantic hearing device. Except it's not pressure waves, but the fabric of the universe which reverbates. Note that the frequency of the signal is indeed in the audible range. Anyway, I was a bit irritated of this same phrase, but because I tought radio astronomers had been listening to skies for quite some time now.
    • wuliwong 11y ago
      I think it bothers me because it is focusing on the sound that some small piece of this operation creates when the amazing thing is to be able to measure gravitational waves. Who cares if you hook the output of some piece of LIGO up to a speaker or not and make a noise? Unplug that speaker and these results are just as amazing.
• programd 11y ago
  The original science paper is here [0] [0] http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.061102 http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116...
• onetimePete 11y ago
  Would such a gravity wave cause a tsunami on a world circling the two black holes?
• fucsia 11y ago
  once shot up the outside of one of the antenna arms in Louisiana, and a truck crashed into one of the arms in Hanford Does this mean an actual truck, a vehicle? Did they accidentally hurt someone? I liked this quote: The future for the dark side looks bright.
• chejazi 11y ago
  Lost in the transformation was three solar masses’ worth of energy, vaporized into gravitational waves in an unseen and barely felt apocalypse. As visible light, that energy would be equivalent to the brightness of a billion trillion suns. Beautiful.
• oldo-nicho 11y ago
  I'm interested to know how they can be so sure that the change in distance between the two arms of LIGO is attributed to gravitational waves? I would of thought that miniscule movements in the Earth's crust would be a more likely culprit.
  • thisrod 11y ago
    The LIGO mirrors and beam splitter are attached to Earth very loosely. They hang from towers of pendulums; when Earth moves, LIGO catches up eventually, but over the time it takes a gravity wave to oscillate the components might as well be in orbit. That is one of the more routine feats of engineering involved.
  • oldo-nicho 11y ago
    Ahh, just realised that there are two instruments located on either side of the states, so if both instruments register the same event then it is unlikely to be tectonic movement...
• brownbat 11y ago
  Einstein wasn't sure at first. It was Feynman who introduced the thought experiment that settled the debate in the physics community: https://en.wikipedia.org/wiki/Sticky_bead_argument https://en.wikipedia.org/wiki/Sticky_bead_argument
  • gaur 11y ago
    Not sure why this received downvotes. There was significant debate until the 1950s about whether gravitational waves were real phenomena or just coordinate artifacts. The sticky bead argument played a big role in settling the issue.
• wslh 11y ago
  Weird nobody mentioned here the excellent threads on this topic here https://www.reddit.com/r/science/comments/458ppo/ligo_makes_gravitational_wave_announcement_today/ https://www.reddit.com/r/science/comments/458ppo/ligo_makes_... and here https://www.reddit.com/r/askscience/comments/458vhd/gravitational_wave_megathread/ https://www.reddit.com/r/askscience/comments/458vhd/gravitat...
• gnaritas 11y ago
  No they haven't proven Einstein right, they've failed to prove him wrong; that distinction is the essence of science. Theories are never proven right, they can only be proven wrong.
• hun-nemethpeter 11y ago
  According to this paper ( https://dcc.ligo.org/LIGO-P150914/public https://dcc.ligo.org/LIGO-P150914/public ) they detected the signal first at Livingston, Louisiana and 6.9ms later in Hanford, Washington. The distance between them according to wikipedia ( https://en.wikipedia.org/wiki/LIGO https://en.wikipedia.org/wiki/LIGO ) is 3002km (Ok, the 3002 km distance is on the Earth). If the gravity wave travel at the speed of light they should detect 10ms later (300 000/3002 sec = 1/100 sec = 10ms ). From these data the gravity travels at 434 000km/sec instead of 300 000km/sec. Almost 50% faster then light... Is there any error in my calc?
  • josho 11y ago
    Wild guess on my part. The wave is traveling through the earth, while the distance you measured is around the circumference and therefore larger. Too bad, you had me excited for a moment at the thought of faster than light travel.
    • AnonNo15 11y ago
      Even ignoring the curvature of the Earth, the signal source was not necessary located on the straight line between two LIGO locations, but rather at some angle to this line. For example if the signal origin was on the line that is exactly between the two LIGO detectors, the time delay would be zero.
  • demallien 11y ago
    10ms is the absolute maximum difference in time, if the source was located on a line running through the two detectors. If the source was located on a perpendicular bisector of the line running through the two detectors, the difference in time between detections at the two detectors would be zero. Any value between the two is possible depending on the geometry.
  • glial 11y ago
    I think your calculation assumes that the waves are traveling parallel to the line connecting Livingston/Hanford. In the diagram below, 's' is the source of the waves. H-----L-------s If instead the waves are traveling perpendicularly to the line between those two cities, they should be detected at the same time. s /|\ / | \ L-----H Since the measured time difference is between 0ms and 10ms, the reality is probably somewhere in between these two extremes.
• ridgeguy 11y ago
  Obligatory...... http://xkcd.com/1642/ http://xkcd.com/1642/
• sytelus 11y ago
  Better video directly from LIGO/Caltech: https://www.youtube.com/watch?v=wrqbfT8qcBc https://www.youtube.com/watch?v=wrqbfT8qcBc And here's more detailed from PBS Space: https://www.youtube.com/watch?v=gw-i_VKd6Wo https://www.youtube.com/watch?v=gw-i_VKd6Wo
• meganvito 11y ago
  the wave can from two different slits, so one beam travels longer
• meganvito 11y ago
  the wave can come from two slits, one beam comes later maybe
• euske 11y ago
  I sometimes wonder why tech people like space-related stuff so much. It is a major news indeed and a feat of science and technology, but why is space so popular? Because it's otherworldly, large-scale and kind of making you feel empowered or united? I'm probably more interested in mundane, obscure and humble stuff, so this disproportionate popularity of space-related news is always baffling to me.
  • mturmon 11y ago
    In grappling with this question myself -- it's a good question -- I've concluded the interest is in understanding and predicting the behavior of a system based on a few laws. The system is quite complex and full of exotic objects, so ordinary real world intuition is a poor guide. And the laws are couched in a mathematical language that is also foreign to our everyday world. Yet, predictions can be made and tested. It's an intellectual puzzle like "what does this very tight loop do?", or "how does the Y combinator work?" -- but in a different arena.
  • outworlder 11y ago
    Well, it's not just "space", is it? We (as in, species) just observed a phenomenon that's related on a fundamental way to any form of matter, doesn't matter(no pun intended) if it is space or not.
  • foobard 11y ago
    When I was younger, I loved physics because it bridged the gap between pure maths ("when are we ever going to need this stuff?") and the physical world. I didn't pursue it beyond high school Now, as a full-time software engineer and part time jack of all trades, I appreciate stuff like this experiment and the work of Space X and others much as I appreciate good engineering. It's a difficult problem to solve. So many disciplines had to cooperate to grant us some small insight into the inner workings of our universe. It's marvelous, and makes me feel like a kid again.
  • kbart 11y ago
    I believe it's all about the thrill of discovery. We know Earth comparatively well and there's simply not many areas left where a major discovery can be made. Sure, there's still much to learn, but these advances are made in small, incremental steps rather than major leaps. Space, on the other hand, is still largely a mystery, just like the oceans were for our ancestors.
• AYBABTME 11y ago
  So what does this mean about the future, now? What new capability do we have? What is possible now that wasn't possible before?
• terryf 11y ago
  It was mentioned that during this event, three sun's mass equivalents were turned into gravity waves, I guess that means that matter particles were turned into gravitons. But what happens to them? Is there any way to turn them back into matter? If not, then at some point, will all matter in the universe end up as gravitons? Also, if an object moving through space creates gravitational waves, doesn't that violate the law that states that a non-accelerating object will not lose/gain any energy? Because if you have to emit gravitons as you move in space, and emitting them requires energy or matter expenditure, then an object moving through space will slowly lose all it's mass?
• srkiranraj 11y ago
  I understood how LIGO works but one question I have is, how did scientists conclude the gravitational waves they detected are from a collision of 2 black holes that happened before 1.3 Billion/Million years ago. Could someone explain ?
• ksec 11y ago
  And we are one step closer Gravity Shockwave Generating Division Tool.
• dschiptsov 11y ago
  But there is no "fabric of space-time". Time is a mental concept, it cannot be detected. Whatever they have detected or calculated is something else.
• known 11y ago
  A hole that is less than the sum of its parts. Three suns’ worth of mass has been turned into energy, in the form of gravitational waves; The coalescing holes pumped 50 times more energy into space this way than the whole of the rest of the universe emitted in light, radio waves, X-rays and gamma rays combined.
• jakeogh 11y ago
  Technical details and hints on future results: https://news.ycombinator.com/item?id=11092982 https://news.ycombinator.com/item?id=11092982
• known 11y ago
  Did collision of 2 black holes prove E = MC2
• UhUhUhUh 11y ago
  1.1. billion and 40 years vs. pencil and paper and a few years. That should tell us something about education, mode of thinking and research. And a few other things.