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Physicists Detect Gravitational Waves, Proving Einstein Right

nytimes.com

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Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#31

Post by cdelsolar »

tomp wrote: post #23
antognini wrote: post #10

Earlier quoted context omitted.

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 sens…

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.

Both detectors detected the same event at slightly different times

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#32

Post by nickhalfasleep »

4k wrote: post #29

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.

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.

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#33

Post by davrosthedalek »

tomp wrote: post #23
antognini wrote: post #10

Earlier quoted context omitted.

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 sens…

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.

It's not a counting experiment, which makes the calculation of a false positive rate somewhat harder. The key for LIGO is certainly that they saw the signal coincident at two stations, far apart.

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#34

Post by nickhalfasleep »

pinkrooftop wrote: post #18

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

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

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#36

Post by antognini »

tomp wrote: post #23
antognini wrote: post #10

Earlier quoted context omitted.

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 sens…

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.

The detection uncertainty is a separate matter from the predicted rate. Sure, if you had a strong prior that GWs should be detected once in a billion years, then you would want a better detection. But as it is the priors on the detection are pretty weak and this is totally consistent with what is expected.

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#37

Post by shmerl »

oldmanjay wrote: post #35

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.

> No one would have looked at the first computer and envisioned an iPhone.

Not really. Portable computers were envisioned quite a long time ago.

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#39

Post by mikeash »

antognini wrote: post #10
losvedir wrote: post #4

> 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 tim…

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 sens…

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.

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#40

Post by davrosthedalek »

kordless wrote: post #21
elorant wrote: post #15

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?

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.

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/)
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