Slashdot Mirror
It's Official: LIGO Scientists Make First-Ever Observation of Gravity Waves (economist.com)
A few days ago, we posted reports that a major finding -- the discovery of the long-predicted gravity waves -- was expected to be formally announced today, and reader universe520 is the first to note this coverage in the Economist : It is 1.3 billion years after two black holes merged and sent out gravitational waves. On Earth in September 2015, the faintest slice of those waves was caught. That slice, called GW150914 and announced to the world on February 11th, is the first gravitational wave to be detected directly by human scientists. It is a triumph that has been a century in the making, opening a new window onto the universe and giving researchers a means to peer at hitherto inaccessible happenings, perhaps as far back in time as the Big Bang. Reader
DudeTheMath adds: NPR has a nice write-up of the newly-published results: "[R]esearchers say they have detected rumblings from that cataclysmic collision as ripples in the very fabric of space-time itself. The discovery comes a century after Albert Einstein first predicted such ripples should exist. ... The signal in the detector matches well with what's predicted by Einstein's original theory, according to [Saul] Teukolsky [of Cornell], who was briefed on the results."
Update: 02/11 18:08 GMT by T : Worth reading: this letter, inspirational and informative, from MIT president L. Rafael Reif, about the discovery. (Hat tip to Brian Kulak.)
This matters for a bunch of reasons. First, it helps close confirm predictions of general relativity. We had a lot of evidence already but more is good. Second, if we get more data we might be able to rule out or narrow down our search space for any eventual quantum gravity theory since they have predictions about how gravity waves should behave (although this would require massively upgrading LIGO). Third, this gives us insight into stellar objects that we normally lack the ability to examine. For example, we don't know much about what the cores of neutron stars are like, but different ideas about them give different predictions about what sort of gravity waves two merging neutron stars will create. So this may give us more data about what exotic objects are actually doing. Fourth, this gives us for the first time a way of getting data from very far away sources that isn't in the electromagnetic spectrum. Right now, we can detect neutrino bursts if they come from a few million light years away but pretty much everything from outside our little galactic neighborhood has to come either from electromagnetic radiation or detecting cosmic rays. But LIGO can already detect gravity waves from events that are a billion light years away. So this gives us a whole new long type of data.
While gravity can be viewed as having an instant effect, the propagation of changes in gravity influence moves at the speed of light. That propagation action can been rationalized like a wave.
'...if only "Jumping to a Conclusion" was an event in the Olympics.'
Its possible to formulate theories of gravity that don't have gravity waves, but there was already strong evidence of their existence from measurements of the orbit decay of neutron star binaries.
Direct detection was fantastic - but it confirmed what was already believed to be extremely likely.
> Nobody actually ever thought that gravity waves wouldn't exist
Which is precisely why this is such a non-important result. You don't learn much about the universe by demonstrating something everyone already knew is true. It would be much, MUCH more interesting if it didn't work.
To the contrary. Now that we have detected gravitational waves, we can start comparing the predictions to the measured data. Until we had detected them, we couldn't compare theory to data. Now we we have a possibility to do so.
That's why the MMX is cool, and this isn't.
>But it's amazing that we can actually detect it.
From a technology point of view, yes. From a theoretical perspective, not so much.
http://www.geoffreylandis.com
Are gravitational waves different from gravity? Because this article would have you believe that the speed at which they propagate is speed of light, where as gravity has instant effect AFAIK.
Gravity does not have instantaneous effect.
Nothing physical has instantaneous effect.
In any case, if you're talking about the gravity of something just sitting unmoving, it doesn't really mean anything to say that the gravitational effect is instant, or delayed. It only makes sense to ask the question when something is accelerated away from sitting stationary, and in that case, the effect isn't instantaneous; the change in effect at an observer is at the speed of light.
http://www.geoffreylandis.com
Well, except for the niggling one where it demands a completely different vacuum energy level than the similarly well-tested theories of Quantum Mechanics.
It's an odd situation - we have two well-tested and widely accepted theories, neither of which show any significant cracks, but which are utterly incompatible with each other.
--- Most topics have many sides worth arguing, allow me to take one opposite you.
Finding them means we can start developing better instruments. Primordial gravity waves are our best shot at understanding the inflationary epoch and understanding the Big Bang itself. This is one of physic's greatest triumphs.
And, of course, it confirms once again that Einstein remains one of the titans of human thought.
The world's burning. Moped Jesus spotted on I50. Details at 11.
This has happened in science before, with contradictions between Newton and Maxwell. The whole special relativity thing was the reconciliation.
To date, everything they've ever tested says that the theory of relativity, as far as we've been able to investigate, hasn't shown any cracks.
That's not quite right.
- GR breaks down when you go to quantum levels
- GR does not fully describe black holes (particularly their horizon and the singularity)
- GR is incomplete with regards to explaining the expansion of the universe (the discrepancy is called Dark Energy)
NB: The message above might reflect my opinion right now, but not necessarily tomorrow or next year.
If it were possible, you could use gravity for FTL communication, possibly even allowing you to violate causality.
"When information is power, privacy is freedom" - Jah-Wren Ryel
It just came out in Physical Review Letters today: http://journals.aps.org/prl/ab...
They don't. If you get distortion in the exact direction of the perpendicular then it is hard to detect. The key to detection is that if it comes in at even a little angle then the two lasers will be distorted relative to each other.
For those who are interested, the scientific journal has a companion article here. It describes the design and sensitivity of the experiment, as well as some of the context. There is also a link to the actual journal article to the right, but you may need institutional access to download it.
I would rather be killed by a terrorist than enslaved by my government.
Any science you can explain in a few sentences to a layman will be so full of holes as to be nothing more than hearsay and astrology.
A big event, that would have created ripples that would arrive here roughly at the time of the experiment, happened. As we listened, at that time, we saw inconsistencies representative of just such a gravitational wave hitting the experiment. It's tiny, but above background noise and experimental error (it's mentioned elsewhere that this basically means 6-sigma certainty), and coincides with a particular event that we were able to "observe" (not literally) in other ways.
The source of the wave barely matters. We detected gravitational fluxes that would otherwise be unexplained. That we are able to correlate them to one single event, that's just of the type of rare event that we predict might be able to cause such signals "loud" enough to be "heard" by us, and match up the timing means that it's the most likely explanation too.
But more importantly - 100-year-old mathematics predicts some absolutely insane, bonkers things that - when we are finally able to look for them - turn out to be true. That's all science cares about.
You can't just make up shit and then - in 100 years - several people invent an instrument that correlates perfectly to the shit you made up, several times, to the satisfaction of major scientific institutions unless - basically - you were absolutely spot-on correct all along.
That's pretty much what happened. The Einstein field equations are fucking bonkers to understand, let alone try and solve the implications of them. And I'm a mathematician. But they predict stuff like this that we then find. When it came from barely matters. A simplification of the definition of "size" in a mass-media article doesn't matter at all (tell people black holes have no size, and they look at you like you're an idiot).
So, no, it's not as bad as you make out.