Physicists Detect Gravitational Waves, Proving Einstein Right

http://www.nytimes.com/2016/02/12/science/ligo-gravitational-waves-black-holes-einstein.html

by intull • 10 years ago

2011 477 10 years 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.

fluxquanta• 10 years 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.

effie7• 10 years 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• 10 years ago

"fundamentally computational form of the universe", you must be a seth lloyd guy :)

But yes, it's the fringes that we'll find new physics. It's not unlike the late 19th century when newtonian + E&M seemed to account for all there was to know.

There hardest thing in fundamental physics right now is to know what questions to ask. We've got answers that work for a lot of the biggest ones that the last 100 years have been spent developing and exploring.

212• 10 years ago

You're way too optimist.

You forgot about dark matter.

And the devices required to probe Plank length/mass/energy are way beyond even our imagination.

jacquesm• 10 years 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.

snowwrestler4• 10 years ago

Well we've accounted for about 5% of the universe--the stuff we know about.

Dark matter (about 25%) seems to only interact gravitationally, which means that we've just, today, proven that we have an instrument that could possibly observe it directly. To date, all our evidence for dark matter is indirect--observing the otherwise unexplained behavior of normal matter. Today is the gravitational equivalent to Galileo pointing his first telescope at the night sky.

Dark energy (about 70%) still seems to be a total mystery.

And of course there is our inability to reconcile quantum mechanics with gravity. With each further proof of the correctness of each of those theories, the mystery of their apparent incompatibility deepens.

All of these factors lead me to believe that we may still have a long way to go in our understanding of the physical universe. I hope I'm right.

This is also why I believe it is so important to pursue nuclear energy. If we do invent further theories and experiments, it's likely that they will require even greater energy levels than we can create now, and potentially imply even greater dangers. If we can't learn to manage nuclear physics in a practical, routine way, we'll never have a hope of going beyond it (if indeed there is a "beyond.")

gsibble• 10 years ago

Completely agree. We have a long way to go.

daveguy• 10 years ago

How do we know dark matter is some mysterious form of matter and not just small distributed particles (gas or solid) that are beyond our ability to detect? Do we have proof of a specific, exotic, non-atomic matter?

ericjang2• 10 years ago

An underground device sensitive enough to detect animals walking around could be useful for other things... (from ecology research to large-scale surveillance)

selimthegrim2• 10 years ago

It's not underground - it's raised up about a meter off the ground.

evanpw2• 10 years ago

quantum field theory and general relativity are now both experimentally complete, and both look nearly unassailed in their correctness

Well, we know that both theories are "wrong" in the sense that they give nonsense answers if you ask them the wrong questions. It's just that all of those questions are well beyond our ability to test experimentally.

lobster_johnson• 10 years ago

Dicussed here: https://news.ycombinator.com/item?id=11079462

tfgg2• 10 years 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...

losvedir• 10 years 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• 10 years 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.

dragonwriter6• 10 years 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."

antognini2• 10 years 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.

tomp• 10 years ago

If this events are so rare (that we don't even know how rare they are), how is it possible that they achieved the required certainty (5 sigma)?

I guess you could count one looong wave as a series of one-time events/measurements, but it could as well be a loooong interference.

mikeash5• 10 years ago

Is there any idea how far away these black holes were? It would be interesting to know the volume of space it can potentially detect evens.

rdancer• 10 years ago

What does that mean in plain English?

zoke• 10 years ago

I recall reading some years ago that gravitational wave would be used to prove multiverse theory. How would that scale compared to bh-bh or ns-ns mergers?

Also, have read today that this discovery backs inflationary theory, how so?

It seems highly unlikely that they could say a specific bh-bh merger was the cause. It seems implied they are triangulating the source, with two detectors?

theptip• 10 years ago

Do you know the current best estimate for BH-BH and NS-NS mergers? (Or at least, what they were before this experiment moved the needle).

Interested to know what they were shooting for when they spun this experiment up.

cyphar6• 10 years ago

Well, the number of solar-mass black holes in our galaxy is about 10^8. Since black holes form from stars, you can assume the probablity of having binaries is probably related to the probablity of having binary systems in stars, which is high. And the distance to the event is several megaparsecs (much bigger than our galaxy). The fact that they detected two 30 solar mass black holes coalescing 2 days after their sensitivity upgrades says that they almost certainly have had other, less pretty, detections in the few months they've been running their detectors for. Or they should go buy some lottery tickets.

nathanielc• 10 years ago

Typically one would assume that it was not coincidental and then adjust the bounds for how often we expect the event occurs based on observations, or lack thereof.

misnome• 10 years ago

In the press conference Kip Thorne mentioned that the estimates were for several events per year, before sensitivity upgrades.

davrosthedalek5• 10 years ago

But he neglected to mention the error bars on this, which AFAIK are huge at least for BH-BH mergers. Every time we built a new instrument, we saw something new, whether in astrophysics, or nuclear physics, or particle physics. Maybe the BH-BH rate is much higher than expected.

sandworm10110• 10 years ago

> that shortly after the detector came online we just happened to observe the exact moment a billion years ago that two black holes collided?

Counterintuitive, but yes. Because it happened billions of years ago, it happened a long long way away. The sphere of objects billions of years away/ago is far larger than those closer to us. So such a detector should be detecting exponentially more very old objects than new ones. Given the rarity, I would expect nearly all detected events to have happened long long ago in galaxies far far away.

Also, models point to such events being more common in the distant past where there were more black holes (primordials) floating around than there are now.

idanoeman• 10 years ago

*Polynomially more objects.

The volume of a constant-thickness spherical shell is O(r^2).

pistle• 10 years ago

If one event happens 1B years ago 1B light years away and another event happens at .5B years ago .5B light years away... how would we know there are two events?

tizzdogg4• 10 years ago

I am not a physicist, and dont have a good mental model of gravitational waves (or general relativity at all), so maybe someone can answer my laymans question: do these waves behave like ripples in water, so a single event generates multiple repetitive, concentric waves permeating through space? That would make me think that a single massive event would be easier to detect because it would leave many repeated "echoes", ringing space for a long time after the actual event.

The article makes it sound like the detection of these waves is just a quick one-time blip though. I'd expect something as big as black holes merging to generate more longer lasting waves than just a quick blip. What is the period of these waves?

ScottBurson3• 10 years ago

An echo is a reflection. I don't know whether gravitational waves can be reflected even in principle, but even if they can, space is so empty that in practice there's nothing to reflect them. So even a single massive event, like the one described in the article, will just send out a single expanding spherical wavefront; if you're not listening at the right moment, you'll miss it.

lutorm4• 10 years ago

https://www.black-holes.org/gw150914 has some visualization of the event. There is the initial inspiral, and then there is a ringing afterwards. However, the entire event is over in a fraction of a second, which may be a "blip" to humans, but is very long when things happen at the speed of light.

itaibn• 10 years ago

"do these waves behave like ripples in water, so a single event generates multiple repetitive, concentric waves permeating through space?"

No they don't. There is a law known as [Huygens' principle](https://en.wikipedia.org/wiki/Huygens%E2%80%93Fresnel_princi...) which says that when a disturbance at a particular point creates a wave, that wave only propagates on an outwards-expanding sphere that is centered at that point of disturbance, and does not produce any effect on the interior of that sphere. This was originally formulated for light waves, but it also holds for other kinds of waves, such as sound waves or, in this case, gravitational waves. What this means is that when you look at something that's far away you see a sharp image of exactly what happened there a short time ago (the time it had taken the light to reach you), whereas if the principle did not hold, each light source would have a small "echo" after it which would blur the image.

However, one of the reasons Huygens' principle holds is that the waves are propagating over three dimensions. In contrast, water waves only propagate over two dimensions, so Huygens' principle fails. That is why ripples continue to emanate from a spot even long after the disturbance there is over. More generally, Huygens' principle holds whenever the number of dimensions is odd and fails whenever the number of dimensions is even.

[Note: I may be wrong on why Huygens' principle fails for water waves. Water waves are actually pretty complicated compared to other kinds of waves and I am not knowledgeable in all the subtleties.]

swayvil• 10 years ago

Excellent catch. That's damn suspicious.

cdelsolar4• 10 years ago

I may have suffered permanent eye damage from the rolling.

Florin_Andrei3• 10 years ago

The coalescing and ring-down takes a fraction of a second. The fraction of a second refers to the duration of the event. It does not mean they caught an event a fraction of a second after they turned it on.

Here's a better article:

http://www.newyorker.com/tech/elements/gravitational-waves-e...

gammarator3• 10 years ago

Or do these events happen all the time, and so if it wasn't those two black holes it would be two others?

This is right. Soon we'll have a much more precise value for "all the time!"

chrismbarr• 10 years 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• 10 years 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• 10 years ago

Live stream from the NSF: https://www.youtube.com/user/VideosatNSF/live

elorant• 10 years 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• 10 years 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!

kordless4• 10 years 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.

davrosthedalek5• 10 years 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/)

dragonwriter6• 10 years 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.

Steuard6• 10 years ago

Both!

As others have said, intensity (power per unit area) decreases according to the same inverse square law that governs most effects due to localized sources in three dimensions of space. In this case, you're looking at a distance of over a billion light years, and then squaring it: that's a pretty enormous "per unit area"!

But gravity itself is also a tremendously weak force compared to the others. That may seem surprising at first, but it becomes pretty clear when I point out that a cheap little refrigerator magnet exerts enough force to overcome the gravitational pull of an entire planet right beneath it. Gravitational waves are pretty much just ripples on the top of that already tiny force.

bzbarsky10• 10 years ago

LIGO is measuring wave amplitude, which is the square root of the power. So the thing it measures actually goes down linearly, not as inverse square.

ufmace• 10 years ago

Near as I can tell, they're intrinsically extremely weak, so much so that the only thing we've been able to see it all is extreme events like these black hole mergers. In theory, pretty much any time anything moves, some level of gravitational waves should be generated, though no telling if we'd ever be able to detect them.

bzbarsky10• 10 years ago

A bit of both. https://en.wikipedia.org/wiki/Gravitational_wave#Wave_amplit... runs through the numbers for the gravitational waves the Earth produces by orbiting the sun; it claims that at 1 light-year the amplitude would be 1 part in 1e26.

For comparison, the wave that was detected is claimed to be "four one-thousandths of the diameter of a proton". That's about 7e-18 meters, on a baseline arm length of 4 km, so about one part in 6e20 -- about 175,000 times stronger than the waves Earth's orbit produces. And that was about 40x as strong as minimal sensitivity on LIGO, according to the article ("can detect changes in the length of one of those arms as small as one ten-thousandth the diameter of a proton").

Obviously if we were closer to the black hole collision we'd see much stronger waves. But you really do need very massive bodies accelerating very much (or equivalently orbiting very fast) to produce something that's detectable by LIGO over interstellar distances at all. The key part from this article is that the orbital period was about 1/250 of a second at the end; compare to Earth's orbital period. Going back to the formula given in the above Wikipedia entry, the frequency dependence is hiding in the "1/r" factor for the amplitude. 1/r is proportional to w^{2/3} (though it's not clear to me whether that's still true in a general-relativistic treatment; it's true enough for the Earth's orbit), which tells you how the wave amplitude scales with frequency...

drelihan• 10 years 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• 10 years ago

Would it be possible to listen for information transmitted via gravitational waves? Would there be any benefit over radio?

irremediable• 10 years 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• 10 years 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.

jerf2• 10 years 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.

omgitstom• 10 years 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• 10 years 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• 10 years 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• 10 years 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/genera...

[1]https://physics.stackexchange.com/questions/78118/quantum-en...

nickhalfasleep2• 10 years ago

This event was the equivalent of three of our suns turned into pure energy. Pretty expensive to send a message.

yk3• 10 years ago

Burning a few suns per message would significantly reduce spam.

Terretta• 10 years 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."

bcook• 10 years 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.

dragonwriter6• 10 years 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.

kachnuv_ocasek• 10 years ago

Paper here: https://dcc.ligo.org/LIGO-P150914/public

4k• 10 years 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.

nickhalfasleep2• 10 years 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.

Steuard6• 10 years 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.

thisrod3• 10 years 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.

oldmanjay2• 10 years 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• 10 years 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.

oldmanjay2• 10 years 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.

exodust• 10 years ago

I wonder if gravitational waves are responsible for the video starting automatically without me clicking play.

mikeash5• 10 years ago

Yes, in that any given event is ultimately the result of all previous events within its past light cone.

jshelly• 10 years ago

Does anyone else get a bit depressed when you consider how insignificant we are?

pklausler• 10 years ago

Nah, it's more of a feeling of liberation from unreasonably high expectations.

venomsnake• 10 years ago

No. But with so much interesting things left to find I start to really really hate the concept of mortality :(

grif-fin• 10 years 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.

chriswarbo• 10 years 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_pe... there were nearly 200,000 books published in the UK in 2011. That doesn't make the works of Shakespeare insignificant.

ttflee2• 10 years ago

Total Perspective Vortex told me that I was important.

eecks• 10 years ago

It just depresses me that I'll never reach an Einstein standard in any thing I do :/

readme• 10 years ago

Not with that attitude!

kamaal4• 10 years ago

If we can keep our heads cool, and priorities right. We can get very significant.

Wherever we went on earth we've colonized quickly. If we can do that to space, universe might be our backyard.

adrianN3• 10 years ago

Space is pretty big tough and entropy gets you eventually.

mc8082• 10 years ago

Most of those very subtle gravitational waves are also rather insignificant. Normally their effects would be swamped by other forces and interactions. At least as far as we know, we are the first agents in the universe to build structures that isolate and amplify those effects in a way that allows them to be perceived and appreciated. That seems pretty significant. We may also be the only means the universe has to feel proud of this little accomplishment.

auntienomen2• 10 years ago

FWIW, I take some comfort in knowing that I can beat up the vast majority of gravitational waves.

ddingus4• 10 years ago

I have. There is just so much out there...

On the other hand, it's nice to know the world really does appear to be boundless. I mean in terms of the possible.

We aren't much, but we are here and it's a pretty awesome experience.

Maybe we need to be here, otherwise what is the point?

I like to think there are others too, thinking thoughts like we are. Maybe that is necessary too. Maybe nobody has reached a point in their development for more, or contact to make sense.

I find our time here and now bittersweet. So much is yet to be experienced and understood. But, then again, here and now isn't all bad. We have great science, new frontiers opening up all the time. Our stories of the future are fantastic, and there is still a lot of magic and wonder about us, the world, reality...

We may not see the best. In fact, I say none of us will, but right now is never dull.

I feel like we are just beginning to get a real grasp on reality. That seems powerful and exciting. We could have lived in much darker, harder, ignorant times.

These times may be seen that way too, or they may be a peak, with a decline to come. Nobody knows, and I like it that way.

orionblastar• 10 years ago

Does this discovery make us insignificant or does it increase our understanding of the universe?

It depends on how you look at it. You are taking a pessimist's view on things that the universe is so large and we are so small that we don't matter. If you take an optimists's view on things you'll discover that we do matter and learning new things increases our significance.

aws_ls• 10 years ago

I do. People compare crossing the oceans with space travel. In our present form (on evolutionary scale) we are less than equipped for that.

Also I wonder, in this form as humans, can anyone really comprehend what this all means, beyond the Math and experimental confirmations?

What if we are living in a simulation, and just being played?

scrumper2• 10 years 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• 10 years 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...

mturmon2• 10 years ago

Yes, mind-boggling. 3 solar masses converted to energy in just a few seconds.

pja2• 10 years 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.

bzbarsky10• 10 years 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.

yellow_postit• 10 years ago

What I didn't understand after reading the article is how do they separate out a set of waves for one specific thing vs. the many other objects sending out waves. Is it just that the set of blackholes are the strongest set of waves and thus the ones we can detect?

scrumper2• 10 years ago

I see, thanks.

ISL• 10 years ago

The longer the interferometer arms, the better you can do in sensitivity. The reason LIGO has 4000 m long arms is that it makes the experiment 4000x more sensitive than something you can do on a bench. (and their laser stabilization is excellent, improving things further)

swombat5• 10 years ago

On the other hand, we may well detect the 3 solar masses radiated away as energy. That decreases as an inverse square law, so as one solar mass is about 10^30kg, and 1kg gives off about 10^17 J, we're talking about an explosion releasing something around 10^47 J. For comparison, a 1 kiloton nuclear bomb gives off about 10^15 J.

So, inverse square that explosion... 1 light year is about 10^16m, so we square that and get 10^32m, so we're now talking about ... 10^15 J.

So, unless my maths is all off (which is possible), if this happened about a light year away, whoever's on the side facing towards the blast wouldn't get to observe very much because they'd feel as if a 1kt nuke just went off above their head. Not a great way to start the day.

Chances are it would wipe out life on Earth too, through the ensuing side-effects like lighting the atmosphere on fire, sterilising half the planet, significantly heating up the oceans, possibly even stripping part of the atmosphere away, etc.

For a great novel based around a strikingly similar premise to what was just observed (and the main reason I even bothered to calculate this), Diaspora by Greg Egan is a fantastic book.

contravariant4• 10 years ago

In this case it's not an inverse square law, the amplitude is simply inversely proportional to the distance.

InclinedPlane2• 10 years ago

Yup. Possibly one of the most energetic events in the Universe. Fascinating in many ways when you think about it. That mass was once matter, and somehow it got converted into gravitons.

Roodgorf• 10 years 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.

Steuard6• 10 years 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.

davrosthedalek5• 10 years 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.

nanofortnight3• 10 years ago

Einstein–Cartan theory is the only viable classical alternative.

I am unfamiliar with modern alternatives to comment.

known3• 10 years ago

Everyday we're getting sun rays https://en.wikipedia.org/wiki/Crepuscular_rays

Why are we surprised at gravitational waves when 2 black holes collided?

delecti3• 10 years 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.

macintux3• 10 years 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• 10 years 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?

delecti3• 10 years 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.

ericjang2• 10 years 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• 10 years 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• 10 years ago

Don't worry, their code segfaulted umpteen times, too :-)

spullara• 10 years 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.

bobinator6063• 10 years ago

Then you should have concentrated on theoretical physics instead of experimental?

gammarator3• 10 years 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• 10 years 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• 10 years 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.

bobinator6063• 10 years 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• 10 years ago

I hope Kip Thorne gets a Nobel Prize for this, ideally while he's still alive.

mikeyouse• 10 years 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).

ttflee2• 10 years ago

How could this result be reproduced in an independent repetition, then?

astrosi3• 10 years 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

[2] https://en.wikipedia.org/wiki/KAGRA

giomasce• 10 years ago

I really wonder what the researcher sitting bored at their computer looking at random data thought when they noticed the interesting event!

akuchling• 10 years ago

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• 10 years 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.

swombat5• 10 years ago

Oooh, I can do another back of the envelope calculation here! (cf 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...

soneca• 10 years 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?

wildmusings• 10 years 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• 10 years 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...

nanofortnight3• 10 years 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'.

twoodfin• 10 years ago

I don't know if you can say he was proven wrong, but the Einstein-Podolsky-Rosen paradox was put forward to demonstrate that quantum mechanics must be incomplete, because to accept it implied "spooky action at a distance".

Today, most physicists accept the spooky action at a distance rather than the idea that QM is incomplete.

https://en.wikipedia.org/wiki/EPR_paradox

alkonaut• 10 years ago

He (kind of) had to add the cosmological constant to GR just so the universe wouldn't collapse onto itself and instead be static. The idea of the unchanging universe was maybe partly due to personal or religious preconceptions. So at least in his mind the universe was static, which of course was proven "wrong" by the discovery that the universe is expanding. This was not a proper scientific theory of his, rather a preconception, like his aversion to the randomness of Quantum Physics (again, religion it appears).

Of course, being Einstein, he was again on the right side of the argument when the universe was much later discovered to be accelerating, again requiring a cosmological constant (or some similar fudge factor).

thisrod3• 10 years ago

Try asking that question in Hiroshima :-(

brudgers8• 10 years 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• 10 years ago

A common logical fallacy: https://en.wikipedia.org/wiki/Affirming_the_consequent

gaur4• 10 years ago

That's not to say that what the phenomena measured -- the earth resonating

That's not what the detector measures. RTFA.

dang2• 10 years ago

RTFA

Please don't be rude like that here. It breaks the HN guidelines:

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.

brudgers8• 10 years ago

I read the article. I am in the habit of calling periodic changes in dimension "resonance." I consider it rather consistent with the use of "wave" in the discussion and hence a handy way of describing what the instruments measured rather than what the theory suggests as the first cause.

sandworm10110• 10 years ago

Except that if two detectors, preferably three, detect the wave at the appropriate times then it can be said that whatever phenomena is the cause exists at a particular vector. A bunch of waves all coming from a direction pointing to the center of a huge galaxy would fit the wave model more than any earthbound cause.

corndoge• 10 years ago

http://physics.aps.org/assets/0e3ca952-a3d3-49f2-bbc2-259c0a...

Lower two graphs are predicted waveform in event of binary system coalescence. Upper waveform left and right are observed events at each LIGO facility.

Consider furthermore that the event was observed at each facility with the appropriate lightspeed time offset, and that the wave directionality of the event was lateral and not radial from the center of the earth or some other point as would be expected from a "geophysical" cause.

Furthermore I find it highly unlikely that multiple theoretical and applied physicists would come to apparently total agreement on the significance of these findings and simply overlook the gaping logical fallacy you imply.

brudgers8• 10 years ago

It's not a gaping logical fallacy. It's human nature to tell interesting stories. Black holes colliding is sexy. "We measured a 10^-18 variation in the diameter of the Earth and we are uncertain regarding its cause" is not sexy.

As Jack Friday used to say, "Just the facts, mam."

acchow• 10 years ago

Logical fallacy, yes. But fairly accepted anyway.

Someone comes up with a theory that's mathematically simple, beautiful, and consistent. That's great, but we don't consider it "correct" until it actually predicts something novel and we verify the prediction holds experimentally.

That's your "Y, therefore X".

ddingus4• 10 years ago

Iteration and verification is a part of this.

The core idea is plausible, if circular at present. That's OK. Now, we take that and run with it to expand on what we think we understand and hopefully, confirm and even more hopefully, crack open some new physics.

Seems like Einstein nailed it.

But, questions remain. Any of those could yield insights of similar potency and, ahem... gravity.

dragonwriter6• 10 years ago

I think your argument fails for a few reasons:

(1) It simply fails to understand the scientific method, which is empiricism, not mathematical/logical proof. Scientific evidence is essentially failed disproof, not logical proof.

(2) It mischaracterizes the nature of the prediction, which includes not merely that something will be measured, but that a particular pattern will be measured.

(3) It proposes unspecified "geophysical causes" as an alternate explanation, but there was no pre-existing geophysical model which predicted the pattern observed. (Any after-the-fact geophysical -- or other -- alternative explanation which explains the observed pattern would also need to perform differently on some other test to be verifiably different, and then we could do the test to distinguish the source.)

(4) It misstates the reasoning to contrast it with other experiments, this is exactly "when X, I will observe Y" (where X is "I construct detectors of a particular type in more than one location" and Y is "I will periodically detect particular patterns of signals on those detectors -- not just one of them alone -- which the model predicts will be produced by collisions of massive, distant objects.")

brudgers8• 10 years ago

Under the theory of science as the study of what is falsifiable, there's nothing here to falsify because there is no way to disprove that a conjectured but unobserved collision of two massive bodies was something else or didn't occur. Which is to say that it is impossible to falsify that a conjecture is a conjecture.

That there is not a geophysical theory, doesn't have a bearing on the correctness of the gravitational wave theory one way or the other...anymore than the absence of a helio-centric model for the solar system made the geocentric model more correct or the absence of a theory of oxygen made the theory of pholgiston more correct. More importantly, both these incorrect theories had reasonable explanatory power to the point that they were useful.

The reason they were useful theories is because they were predictive, pholgiston allowed a person to calculate the weight of ashes after burning and the geocentric solar model made the prediction of the location of stars possible with reasonable precision. On the other hand, theories that offer conclusions about unfalsifiable propositions are what Carnap and the Vienna circle termed "metaphysics".

The conclusion that the experiment justifies is that the Earth resonates. There is no external event to which the measurements can be correlated to establish causality. There's no confidence interval. It's a case where the observations confirm a pre-existing world view under the same human cognitive structures by which seashells on mountain tops confirm a world-wide flood. It assumes that because we live on the Earth we know everything about it.

Anyway, it's a case of over-reaching with the conclusions. It's an argument from design.

guscost5• 10 years ago

Unfortunately not-entirely-unreasonable skepticism can be mistaken for hostility by people excited about a potentially groundbreaking result.

That said, it sounds like they did a lot more work to eliminate sources of error than you may be aware of. OTOH if seismic resonance was causing the correlation, there would probably be more time between the events at the two facilities.

Scientists will try to poke holes in these results while further experiments will try to corroborate them. Meanwhile laypeople will be introduced to more oversimplified and counterproductive ways to think about this stuff. Business as usual.

brudgers8• 10 years ago

I'm sure I was not clear, since that was the first pass.

What the experiment indicates is that the Earth varies in size. Roughly:

  measured distance of 10^-20 meters 
  4km is 10^-5 of earth circumference.
  delta Earth's circumference 10^-25
  total distance change in earth's diameter = 10^-18 meters

Given the non-intuitive nature of geology[1], I am saying that the possibility that the Earth varies that much in dimension due to it's internal structure is not so vanishingly remote as to be left unaddressed. Saying it's ten or a thousand times less likely doesn't move the needle much at that scale...if such a thing were said.

[1]: I'm old enough to have been introduced to platetechonics as a distuptive theory.

igravious• 10 years ago

Skepticism is healthy most of the time.

In this case I don't know if your skepticism is warranted.

1st: Paper said that the waves are redshifted to a certain degree (it's in the abstract) [1], ergo 1.3 billion light-years away in space-time. I'm not thinking you want to be so fundamentally skeptical.

2nd: It's in Wikipedia now https://en.wikipedia.org/wiki/Binary_black_hole#Observation so it's pretty much fact.

You may choose to believe 1st or 2nd piece of evidence.

---

[1] https://dcc.ligo.org/public/0122/P150914/014/LIGO-P150914_De...

Steuard6• 10 years ago

[0. A long history of theoretical and experimental discoveries lead to a specific, well-motivated theory (General Relativity) describing gravitational phenomena.]

1. Theory predicts a very specific and recognizable class of gravitational wave patterns for likely sources, whose details are determined by a small number of parameters that correspond to meaningful physical quantities (specifically, two masses and a distance; I don't know if there are any more than that).

2. Two independent experimental instruments measure a wave pattern that (apart from some low-level noise) is an excellent match to one of the predictions. Fitting the model to match the specific data, the resulting parameters have entirely plausible astrophysical values.

3. This is considered an example of a theory making a specific, novel prediction that is later confirmed by experiment: pretty close to the classic definition of the scientific method.

4. Therefore, the experimental data has provided strong support for the premises of the theory being tested: both its prediction of gravitational waves and its detailed dynamical predictions for the source scenario matching the observations.

Maybe I'm misunderstanding something in your argument, but I don't see any circularity here. What about this process isn't precisely the way that science is supposed to work?

nappy-doo• 10 years 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?

lutorm4• 10 years 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• 10 years 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• 10 years ago

Does gravity move at the speed of light?

ddingus4• 10 years ago

The videos say the waves do move at exactly the speed of light. They are massless.

goshx• 10 years ago

This is live now: https://www.theguardian.com/science/across-the-universe/live...

kamaal4• 10 years 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.

macintux3• 10 years 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• 10 years 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.)

xCathedra• 10 years ago

Could someone explain what possible applications this might produce?

ddingus4• 10 years 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• 10 years 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.

boardwaalk• 10 years ago

If they build a third observatory, can they triangulate where in the universe the events are occurring?

stouset3• 10 years 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_Andrei3• 10 years 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.

lutorm4• 10 years 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).

anchpop• 10 years ago

They'd have to build 4, actually. Imagine 3 intersecting spheres, there would be 2 possible positions remaining (just as with 2d triangulation, having 2 circles would leave 2 points remaining and we'd need a 3rd to find out which was correct

swamp403• 10 years ago

Yes.

There is a third one (VIRGO) near Pisa, Tuscany - a French/Italian collaboration.

Unfortunately it was not online for this event.

There is also one being built in Tokyo, and another being planned in India.

TheOtherHobbes• 10 years ago

There's also a planned project called eLISA which will use satellites to increase accuracy and sensitivity.

https://en.wikipedia.org/wiki/Evolved_Laser_Interferometer_S...

enedil• 10 years ago

Triangulation doesn't work in this case, since how would you expect that the waves aren't curved by gravitational electromagnetic field?

Steuard6• 10 years ago

Even with just two LIGO locations, they were able to give a very rough estimate of the source location during the livestream this morning. (It was somewhere kinda in the direction of the Magellanic clouds. Probably.) Once advanced VIRGO comes online (later this year?) we'll have three, which will significantly improve directional accuracy for much of the sky. And when KAGRA turns on in Japan sometime around 2018, we'll have four. During the livestream this morning, someone said that would lead to source locations accurate to within 5-10 degrees on the sky.

elihu• 10 years ago

One would think so. I'm not an expert in this area, but from the descriptions it seems like they would have at least two options for finding the source direction:

One is to compare the arrival time at each of the detectors and infer direction from the speed-of-light delay.

Another option is to measure the difference in relative strength between each of the detectors. I'm assuming the detectors aren't uniformly sensitive; perhaps they're most sensitive to waves travelling in a direction parallel to one arm of the detector and perpendicular to the other, and completely insensitive to waves that are perpendicular to both (i.e. it would affect them both the same and cancel out, or perhaps not affect either of them at all). With multiple detectors at right angles to each other, you can get a pretty good idea which way it came from.

Combining the two methods could give you greater accuracy, and also help to rule out spurious signals that are not gravity waves.

This makes me wonder what you would see if you had a sufficiently accurate directional gravity wave detector and let it run for a long time. Sooner or later, you'd get an actual image, like a telescope.

thecrazyone• 10 years ago

I'm guessing they can already do that by corroborating with other techniques.

hiphopyo• 10 years ago

Does this bring us any closer to warp drives?

ingenter• 10 years ago

No, because "warp drives" in the sense of "Alcubierre drive" requires negative mass, which is not observed anywhere.

drdeca• 10 years 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• 10 years ago

So does this verification of gravitational waves help with Physics theory-building? Have people really doubted Einstein : the existence of gravitational waves?

jharohit• 10 years ago

For those who missed the live announcement by the team https://youtu.be/aEPIwEJmZyE?t=27m13s

frandroid• 10 years ago

The future for the dark side looks bright.

Oh no you didn't.

amai2• 10 years ago

Wow, the list of authors to the paper is three pages long:

https://dcc.ligo.org/public/0122/P150914/014/LIGO-P150914_De...

stevebmark3• 10 years 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• 10 years 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)

stevebmark3• 10 years 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?

tedd4u2• 10 years ago

Thanks - still not sure I get it. The "fabric" is stretched in x, squeezed in y, sure. Is it that the wavelength of the light is -not- stretched? Guess I need to go back and study physics again :/

theophrastus2• 10 years ago

Here's my re-statement of this confusion, isn't everything we can experience embedded in time-space, including the LIGO experiment itself? So how is there any relative shift allowed to be detected when everything we know is fundamentally intrinsic to time-space? That is, I too would appreciate having this mis-conceptualizing, of mine, cleared away.

ScottBurson3• 10 years 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

sandworm10110• 10 years 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• 10 years 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?

kingkawn• 10 years ago

maybe a black hole projecting gravity is how it sends information back out

contravariant4• 10 years ago

Force carrying particles in general don't have mass. Except that some of them seem to do, which was rather puzzling for some time, but was solved using the Higgs mechanism.

I can't think of an obvious reason the Higgs mechanism wouldn't work for gravitons, but I could be mistaken, it's not exactly the most intuitive area of physics.

Also, keep in mind that the strong force transmits the force between colour charges while also having a colour charge itself, so it isn't entirely inconceivable for the force transmitting the attraction between masses to have a mass.

No clue if a massive graviton would allow for black holes, but it's not entirely sure what black holes even are (especially quantum mechanically). At the very least it's presumably possible for some particles to escape it (e.g. as Hawking radiation).

SaberTail2• 10 years ago

What do you think of the strong nuclear force? Gluons are the force carriers between color-charged particles. And gluons themselves have a color charge. So gluons transmit force between each other. Does that mean the universe is already too strange to exist?

By the way, this is why the strong nuclear force has such a short range. Gravity has infinite range as far as we can tell, so that makes it unlikely that the graviton, if it exists, has mass.

Manishearth6• 10 years ago

Imho whatever is carrying gravity between masses cannot itself have a mass.

Forget gravitons, this already exists in pure general relativity. Spacetime is curved around a massive object, and that curvature contains energy. That's just another word for mass, so the curvature itself exerts gravity. This creates more curvature (...etc etc). This is one of the reasons as to why Einstein's equations are nonlinear.

Note that the concept of having mass is separate from the gravity force. Interaction with the Higgs field gives rise to mass, whereas gravitons are the force carrying particle for gravity.

dbranes• 10 years ago

Gravitational waves are a prediction of classical linearlized gravity - gravitational waves are to (classical) gravitons what light waves are to photons.

smegel2• 10 years ago

But we have direct experimental confirmation of light behaving light both a wave and as a particle. Do we have any such evidence to show gravity exhibiting particle like behavior?

jug• 10 years ago

Related to this... According to Kip Thorne, this recent discovery alone places an upper bound of maximum mass for a graviton, if it exists and has mass, at no more than 10^-55 grams. Since otherwise the observed waves would have been distorted. It's cool that we are already seeing conclusions drawn from this observation. This single obsrrvation. https://starguyspeaks.wordpress.com/2016/02/11/on-gravitatio...

pbhjpbhj2• 10 years ago

how far we are from being able to create and detect gravitons //

Surely we create gravitons whenever we move a mass just like we create photons whenever we move a body that interacts electromagnetically? Isn't the point that we're constantly exchanging gravitons with all matter as they mediate gravitational attraction.

ScottBurson3• 10 years ago

I think you must be right -- but maybe there's some other way to create them, without needing to move a mass. The ability to manipulate gravity itself might be the key to space travel.

andrepd• 10 years ago

Keyword here is detect. As the post says, even if we created them we would have no way of knowing because they are virtually impossible to detect.

thedatabase• 10 years ago

Here's a quote from John Baez's G+:

"Gravity is a weak force, in the sense that the gravitational force between two protons is about 10^33 times weaker than the electric force between them. And I'm using protons rather than electrons here to make the gravity stronger - with electrons gravity would be almost 10^40 times weaker.

This has various consequences, but one is that gravitational waves are absorbed by matter much less than electromagnetic waves. It would be fun to estimate the amount of energy absorbed by the Earth as this particular gravitational wave came through, but it would be absurdly small. Gravitational waves make neutrinos look like rampaging gorillas."

Rephrasing, and assuming waving commutes with rampaging, gravitons make neutrinos look like WAVES of rampaging gorillas. I'm no physicist but to answer the original question I'd hazard a guess: quite far!

amai2• 10 years 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• 10 years ago

Yes

bobinator6063• 10 years ago

No. Spooky Action at a Distance.

jcoffland2• 10 years 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.

gammarator3• 10 years 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

swehner2• 10 years 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.

sandworm10110• 10 years 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.

swehner2• 10 years ago

why was this downvoted?

ernesto95• 10 years ago

I generally dislike idolatry and pinning mayor scientific advancement on one single person, but honestly, Einstein really was something else.

dheera• 10 years 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• 10 years 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!

astrosi3• 10 years 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/

kkylin• 10 years 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), 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.

auntienomen2• 10 years 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• 10 years ago

Sorry, what does that ratio imply?

smegel2• 10 years ago

Are you saying there is some kind of confirmation bias at play, or does this increase confidence in the result?

wfunction• 10 years ago

The latter.

Panoramix• 10 years ago

They also injected fake signals into the detector now and then, partly to keep the analysts on their toes.

http://www.ligo.org/news/blind-injection.php

bbcbasic2• 10 years ago

I don't think they are expected to tell its fake though? It's hard to do a double blind experiment without a "placebo universe".

josephv• 10 years 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• 10 years 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

vecter• 10 years ago

You ... must be trolling.

pkrumins• 10 years ago

Can't wait until this discovery can be utilized to creating some kind of a new technology! Such as time travel!

JabavuAdams5• 10 years 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.

selimthegrim2• 10 years 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-Bragins...

JabavuAdams5• 10 years ago

Great! Thanks. My local university has this.

JabavuAdams5• 10 years ago

More accessible / concise info on the vibration isolation, here: https://news.ycombinator.com/item?id=11084282

wuliwong3• 10 years 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.

swamp403• 10 years ago

The interference pattern is audible - a chirp that "rose to the note of middle C".

wuliwong3• 10 years 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• 10 years 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.

wuliwong3• 10 years 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.

delecti3• 10 years ago

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.

Radio waves are light too though. Or at least they're photons.

noselasd• 10 years ago

It's perhaps not the perfect metaphor. But up till now all we have really directly observed from outside[1] our solar system are electromagnetic waves(of various wavelengths including visible light), and this is something quite different.

http://gmunu.mit.edu/sounds/sounds.html has a bit more info on why scientists tend to use the sound analogy when talking about gravitational waves.

[1] Maybe not entirely true, we have convincing evidence of some extra-solar dust reaching earth too..

ajkjk3• 10 years ago

It is a bit awkward, but, I kinda like it: it's not common in physics for signals to come at frequencies that are actually audible, and these ones definitely are.

programd• 10 years ago

The original science paper is here [0]

[0] http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116...

onetimePete• 10 years ago

Would such a gravity wave cause a tsunami on a world circling the two black holes?

fucsia• 10 years 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• 10 years 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-nicho2• 10 years 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.

oldo-nicho2• 10 years 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...

thisrod3• 10 years 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.

brownbat• 10 years 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

gaur4• 10 years 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• 10 years ago

Weird nobody mentioned here the excellent threads on this topic here https://www.reddit.com/r/science/comments/458ppo/ligo_makes_... and here https://www.reddit.com/r/askscience/comments/458vhd/gravitat...

gnaritas• 10 years 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• 10 years ago

According to this paper ( 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 ) 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• 10 years 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• 10 years 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• 10 years 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• 10 years 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.

hoodoof• 10 years ago

Weird, that's exactly what I was thinking.

codeplay• 10 years ago

I am just curious that is the speed of gravity wave travel at different speed in different medium?

eyko• 10 years ago

Consider that the black holes merged about 1.3 billion years ago. If gravitational waves travelled 50% faster than the speed of light, they would've passed by earth long before our species came around, unless the effect of the collision went on for, say, a few million years after the event?

ridgeguy• 10 years ago

Obligatory......

http://xkcd.com/1642/

sytelus• 10 years ago

Better video directly from LIGO/Caltech: https://www.youtube.com/watch?v=wrqbfT8qcBc

And here's more detailed from PBS Space: https://www.youtube.com/watch?v=gw-i_VKd6Wo

meganvito2• 10 years ago

the wave can from two different slits, so one beam travels longer

meganvito2• 10 years ago

the wave can come from two slits, one beam comes later maybe

euske• 10 years 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.

mturmon2• 10 years 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• 10 years 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• 10 years 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• 10 years 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• 10 years 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?

ksec• 10 years ago

And we are one step closer Gravity Shockwave Generating Division Tool.

terryf2• 10 years 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• 10 years 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 ?

dschiptsov• 10 years 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.

known3• 10 years 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• 10 years ago

Technical details and hints on future results: https://news.ycombinator.com/item?id=11092982

known3• 10 years ago

Did collision of 2 black holes prove E = MC2

UhUhUhUh• 10 years 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.

Physicists Detect Gravitational Waves, Proving Einstein Right

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