What does the discovery of Gravitational waves mean?

Article here.

So apparently we have discovered that the space-time field itself can vibrate, meaning we can not just see but also hear objects in space (in a way). What are the ramifications of this, other than being a fairly solid support of Einsteins theories? How will it change the way we view the world and what new sorts of openings will it bring?

Well, from what I heard on NPR this morning, gravity waves can pass through objects that would absorb electromagnetic radiation – so, if this technology can be refined to the point of real gravity-telescopy, that could greatly increase our knowledge about what’s out there.

Then there’s this “Dark Matter” stuff – supposedly it is invisible, intangible, and cannot interact with ordinary baryonic matter . . . except gravitationally. If so, then perhaps now its existence can be confirmed and it can be directly observed.

The discovery of gravity waves won’t change our view at all, since essentially all physicists had no doubt that gravity waves exist. So far as I know, there is no viable theory of gravity that is consistent with relativity that does not predict gravity waves. However, we now have a unique new way to probe the universe. It can only see extremely violent events, but the stunning data announced today shows that we can extract significant astrophysical information from the observations.

Will this lead to jetpacks? Flying cars…?

Interest waning…

Yes, yes, of course it will. With antigravity, like Luke Skywalker’s landspeeder.

Basic research in science isn’t done in the expectation of making jetpacks, or flying cars, or any other blingy devices; it is done to better understand how the world works. This understanding, in turn, often leads to novel and interesting technologies after a period of maturity and innovation, but it is ridiculous to expect that a basic scientific discovery (or in this case, better characterized as a confirmation) is going to instantly translate into technomagical novelties.

It is unlikely, to the point of near certainty, that we will be able to control gravity or generate gravity waves in the foreseeable future simply by virtue of the energy requirements, much less the knowledge of how to manipulate gravity in more than the crude fashion of moving large masses around. Currently, we can’t even control nuclear forces with any finesse; in order to “look inside” the nucleus or at other composite particles we have to accelerate hadrons and run them into one another, which is sort of like studying piezoelectricity by smashing chunks of quartz together.

It is worth pointing out that circa 1820, electricity and magnetism were viewed as separate forces that were largely a novelty, until a bright young experimentalist came along and suggested that they were not only two aspects of the same force, but that this force could be envisioned as a set of lines along which electric charges flow and about which magnetic force from that current flow was graduated. Michael Faraday lacked the mathematics to describe his concept analytically but essentially intuited electromagnetism as we know it. However, because the only way to generate electricity was to make series of giant electrochemical cells which produced only a weak current, the phenomenon was still regarded as mostly of interest as a parlor trick, and while physicists still sought a coherent theory there was little expectation of its ultimate utility in any technology.

It wasn’t until James Clerk Maxwell (arguably one of the greatest and prolific physicists who should be counted with Archimedes, Newton, and Planck, Einstein, and Heisenberg) came along that we had a mathematically complete theory of electromagnetism. Even at that point the steam engines required to generate sufficient electricity for practical applications beyond telegraphy were still large, stationary, and of limited utility, and Maxwell’s formulation (originally twenty laws in a quaternion notation that was understood by essentially no one until Oliver Heaviside reformulated (and simplified) them into the four vectorized equations that every student learns in introductory physics. Advances in more efficient and compact power generation allowed for experimental research and verification, and ultimately, in the vast array of useable technologies that transformed the world and dominate our lives today in nearly every way, fro illumination on demand to global telecommunications.

Basic research is almost always valuable, not because it makes better buggy whips, but because the insight it gives into the fundamental nature of the world will result in technological innovations that we cannot even dream of. In the case of gravitational waves, it may give us the ability to peer into the world far beyond what we can see in the visual spectrum, and if there are advanced intelligent alien societies out there, it is probably the only practical way to communicate over vast interstellar distances that would otherwise be obscured by dust and diluted by distance.


Well it provides direct confirmation of the existence of gravitational waves (predicted by Einstein 100 years ago) and thus helps further confirm General Relativity, ah, in general. It also confirms that black hole binary systems can form, and that they can merge - that hadn’t been observed before. More generally, it opens up a whole new way of observing the universe, which may reveal new information about the early universe and about the physics of relativistic systems and strong gravitational fields.

Also, it’s both an amazing physical phenomenon and an amazing technical achievement to observe it. We’re talking two black holes whose total mass was 65 times that of the Sun, merging together and kicking off 3 solar masses worth of energy in a fraction of a second, sending that energy out across a billion or so light-years so that when it reached us all it produced was the tiniest of distortions. The detectors are about as long as the height of a large mountain, and it altered their length by a fraction of the size of a proton – and yet, the scientists were able to measure this tiny change definitively, with a very high degree of certainty. Using lasers, because of course lasers.

How epic is that? :cool:

Does it give us any insight into whether a particle or wave model is a better way to conceptualize the fabric of space itself?

I am struck that the measuring mechanism relies on the cancellation of waves, and that the perturbation seen is conceptualized as a ripple in spacetime. Aside from the benefit of quantizing a local event for the purpose of mathematical modeling, it seems to me that thinking of the “stuff” of spacetime as rather more similar to a smoothly contiguous jello as opposed to very densely packed (but individual) components makes more sense.

Is the postulation of gravitons (which would have to be massless to act at infinite distances) the best way to think of a gravitational wave? Why can’t spacetime be a single, smoothly continguous entity which, if jerked at one end, pulls at the other?

The regime which is being probed is one in which gravity is expected to behave completely classical; hence, we won’t learn anything about the constitution of spacetime at the fundamental level. (And if gravity is described by a quantum theory—as most physicists expect it to be—then there is no dichotomy between wave and particle; rather, just as with other quanta, both are appropriate, but incomplete descriptions in different situations.)

One problem (there are others) is that it’s difficult to consistently couple a classical gravitational field to quantum matter (in fact, I don’t think there is any viable model of such a thing right now): quantum particles can enter into superpositions; however, the superposition of the gravitational fields of the particle in either configuration is, in general, not a solution of Einstein’s equations (due to their nonlinear nature).

An approach known as ‘semiclassical gravity’ replaces the quantum matter part essentially with an averaged contribution, and postulates that this acts as a source of the gravitational field; but there are theoretical arguments that this can’t be the full picture, and there are currently experiments being proposed to test this proposal.

Just as a piece of history, the (to the best of my knowledge) first argument that gravity needs to be, eventually, quantized actually came from Albert Einstein himself, and in the very same paper that first predicted the gravitational waves that have now been observed: one of the first reasons to postulate the ‘quantum principle’ was that otherwise, charged electrons would continually emit radiation and hence, spiral into the nucleus, leading to atoms being unstable. But the same should be true for gravitational radiation: since electrons are massive particles, they should emit gravitational waves, and thus, loose energy, leading to an eventual destabilization of their orbits.

I’m however not clear on the magnitude of this effect, and what the time scale of stability for atoms would be.

I understand the universe was opaque in the early days, which puts a hard limit on the visible universe.

I understand this pushes the limit out further, since gravitational waves can pass through opaque stuff. What I don’t understand is whether gravitational waves can be perceived directionally. How did they tie the observations to a particular pair of colliding black holes? I suppose you could use time delays between 2 observatories, but aren’t 3 required for triangulation? (Hm: but triangulation is used with distance calculations. :confused:)

What if the universe is infinite size? Would that generate testable hypotheses with regards to these new instruments?

Can one surf a Gravitational Wave?

You totally forgot the air quotes when saying “lasers”.

Seriously, useful or not, the whole thing is cool as hell. And I love that the most energetic events in the Universe sing at Middle C. Seems fitting somehow.

Only with the right board :wink:

. . . and the Power Cosmic! :cool:

CMC fnord!

They didn’t this time. They said, quoting from the LIGO page: “Based on the observed signals, LIGO scientists estimate that the black holes for this event were about 29 and 36 times the mass of the sun, and the event took place 1.3 billion years ago.”

All we know come from these observations, and they don’t contain a direction for the event or any sort of guess about where it happened.

Which is why more observatories are being build.

Not quite, It hit the LIGO in Louisiana a few milliseconds before the one in Washington, so it’s known it was in an area in the southern hemisphere. The area is fairly large though, somewhere in, IIRC, three constellations.

Yes, a third observatory, especially if it were far away, such as on another continent, would have narrowed the location quite a bit.

Actually, you can get direction from LIGO, because the sensitivity is different in different directions. You get the most sensitivity for a wave coming from straight “up” or “down” (those directions meaning the local up and down at the location of the detector), and considerably less for one coming in “horizontally”. This would, in principle, be enough by itself to narrow the source down to two antipodal points on the sky, with the time delay being able to determine which of the two it was. In practice, though, this information is fairly vulnerable to noise, and so you’d get much better directionality data from more detectors (both because you’d have more time delays to work with, and because you’d have them pointed in more different directions). The even bigger advantage to having more detectors is that it’d let you rule out more noise sources: One of the biggest ways that signal is distinguished from noise in a gravitational-wave detector is that the signal will occur at both detectors simultaneously (or nearly so), while the noise sources at the two detectors will be basically uncorrelated, and so will usually not coincide (this is why they built two to begin with).

Every event observed by LIGO will be at a different frequency, and even for any given event, the frequency will change with time, producing a “chirp”. At some point the chirp will reach a maximum frequency and then abruptly stop, with the maximum frequency depending mostly on the final mass. So there’s really nothing special about middle C in particular. It does happen, though, that the range of frequencies that LIGO is sensitive to corresponds to a portion of the range of frequencies we can hear, so the frequency of any event we can detect with it can be assigned to some musical tone. This is just a coincidence of the design of this particular detector; the proposed but now canceled LISA would have been sensitive to frequencies about a thousand times lower, and pulsar timing methods are sensitive to frequencies far lower yet.

One way we can establish location is to correlate LIGO with observations from other types of telescopes. So if we observe a pair of spinning black holes or a Supernova we can then look at the timestamps of the data and look up LIGO measurements at the same time. We already do this with neutrino detectors.

But this first detector is kind of like Galileo’s scope - now that we know it works and can use the data to fine-tune improvements, we will be able to build better, higher resolution instruments over time. Who knows where the limits will be, and what we will be able to learn?

Benjamin Franklin was supposedly once asked about what use a new scientific discovery was good for. His alleged response was to ask “What is the use of a newborn baby?”

Gravitational waves are a brand new discovery. It hasn’t done anything useful in its first week but we have no way of knowing what might develop from it.

To put it in perspective, the discovery Franklin was commenting on was electricity. It was a firm belief among most people that studying the movement of little particles too small to see was an obvious waste because no possible use could ever come from it.

New Yorker article on discovery: http://www.newyorker.com/tech/elements/gravitational-waves-exist-heres-how-scientists-finally-found-them

I admit I’m a little surprised this was funded given the difficulty of the task. I’m glad it was though.