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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

#221

Post by gradi3nt »

drx wrote: post #54
mikeash wrote: post #39

Earlier quoted context omitted.

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.

TFA says "they had heard and recorded the sound of two black holes colliding a billion light-years away" and "1.2 billion years ago". And from the paper: "The source lies at a luminosity distance of 410+160-180 Mpcc corresponding to a redshift z=0.09+0.03-0.04.". ( https://dcc.ligo.org/LIGO-P150914/public ) Which corresponds to 1.337+0.522-0.587 billion ly (or between 750.2 million and 1.859 billion ly).

So that's wayyyyyyy outside our galaxy? Any idea how many galaxies fit into a 1 billion ly sphere around the milky way? I'm guessing a shit ton, which makes the detection of a bh merger seem more realistic to me.

That's some serious range!

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#222

Post by zoke »

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…

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?

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#223

Post by JabavuAdams »

JoeAltmaier wrote: post #186
snowwrestler wrote: post #180

Earlier quoted context omitted.

Scientists are pretty sure that dark matter is not just regular gas and dust because the amount required to create the gravity we see, would be visible. It would block or reflect a lot of the nearby starlight. Just on the back of an envelope: If we assume the percentages in my post above apply to an individual galaxy, then there has to be 5x as much dark matter mass as lit mass. There's no way you could have 5x as mu…

That always confused me. We have an Oort cloud, whose members we cannot resolve very well/at all. Why do we assume only our star has such a thing? If all stars did, that isn't enough mass to explain dark matter?

> For comparison, the sun makes up about 99.8% of the Solar System mass (500x as much mass as all the planets, dust, etc. combined).

That leaves just 0.2% for all the planets, dust, Oort cloud, Kuiper belt, etc. So ... no.

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#224

Post by rdancer »

pja wrote: post #194
rdancer wrote: post #172

Earlier quoted context omitted.

But gravitational waves are a phenomenon without equivalent. Nothing like that had been observed before. (Am I wrong?) W̶h̶e̶n̶ ̶t̶h̶e̶ ̶L̶H̶C̶ ̶d̶e̶t̶e̶c̶t̶e̶d̶ ̶H̶i̶g̶g̶s̶,̶ ̶f̶o̶r̶ ̶e̶x̶a̶m̶p̶l̶e̶,̶ ̶t̶h̶e̶y̶ ̶h̶a̶d̶ ̶b̶e̶e̶n̶ ̶f̶i̶n̶d̶i̶n̶g̶ ̶p̶a̶r̶t̶i̶c̶l̶e̶s̶ ̶f̶o̶r̶ ̶m̶i̶l̶l̶i̶o̶n̶s̶ ̶o̶f̶ ̶m̶a̶n̶-̶y̶e̶a̶r̶s̶,̶ ̶a̶n̶d̶ ̶ s̶o̶ ̶i̶t̶ ̶s̶t̶a̶n̶d̶s̶ ̶ t̶o̶ ̶r̶e̶a̶s̶o̶n̶ ̶t̶h̶a̶t̶ ̶t̶h̶e̶y̶ ̶o̶n̶l̶y̶ ̶n̶e̶e̶d̶e̶d̶…

The Higgs detection was not a single event but resulted from the statistical analysis of many events.

Thank you for correcting me!

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#225

Post by gaur »

dang wrote: post #135
gaur wrote: post #113

Earlier quoted context omitted.

> That's not to say that what the phenomena measured -- the earth resonating That's not what the detector measures. RTFA.

> 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.

Fine, but I find comments like "I don't really grasp what's going on, but I can show it's crap using high school logic" to be extremely low-quality, and I'm sure I'm not the only one.

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#226

Post by tossaway1 »

drx wrote: post #54
mikeash wrote: post #39

Earlier quoted context omitted.

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.

TFA says "they had heard and recorded the sound of two black holes colliding a billion light-years away" and "1.2 billion years ago". And from the paper: "The source lies at a luminosity distance of 410+160-180 Mpcc corresponding to a redshift z=0.09+0.03-0.04.". ( https://dcc.ligo.org/LIGO-P150914/public ) Which corresponds to 1.337+0.522-0.587 billion ly (or between 750.2 million and 1.859 billion ly).

If these waves travel at the speed of light shouldn't the distance and time match up...?

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#227

Post by aabbccdd »

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

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#228

Post by astrosi »

hendekagon wrote: post #198

Has anyone converted the spectrograms given in the paper, or better still the raw data, into sound yet ? Each location in each ear please!

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/

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#229

Post by enedil »

boardwaalk wrote: post #138

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

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

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#230

Post by swombat »

bzbarsky wrote: post #190
platz wrote: post #143

Earlier quoted context omitted.

I would like to understand why a gravitational wave distorts length in relation to normal gravity wells; specifically is this particular to waves? Why don't lengths get distorted in a normal gravity well, or do they? In essence, what is different between a gravity wave and a gravity well, which i understand both distort space, but only the wave distorts it in a way we can measure? Does the gravity well change lengths…

A gravity well also distorts lengths, as best I understand (which is not very well, to be honest; take everything I'm saying here with a big grain of salt). The difference in terms of detection is that the wave does this in a time-varying, periodic fashion. For something like LIGO, we're trying to measure length changes on the order of 1e-18 meters. We're not actually measuring the lengths of LIGO's arms to that accu…

Actually, we have ample proof of the distortion of spacetime in a gravity well - gravitational lensing. It's an observed effect around very massive objects and we have been able to see it at work very well. Also, arguably, the fact that we're not falling towards the sky is itself evidence of a spacetime gradient near the Earth, but that was also explained by Newton's Law of Gravitation.

But back in 1916, Einstein also theorised, as part of his general theory of gravitation, that there would be such things as gravity waves, caused by very massive objects moving through spacetime making 4-dimensional ripples appear in spacetime. Until today, that was just an unproven theory, though everyone believed it was likely to be true. There is now solid evidence to back it.

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