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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

#201

Post by contravariant »

scrumper wrote: post #47

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 co…

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

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#202

Post by lamontcg »

wildmusings wrote: post #114
soneca wrote: post #108

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?

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.

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...

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#203

Post by jdmichal »

daveguy wrote: post #163
snowwrestler wrote: post #70

Earlier quoted context omitted.

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 po…

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?

Dark matter was "invented" because there wasn't enough observable mass in galactic-scale objects to account for their behavior. In other words, they acted like they had more mass than we could observe. Dark matter is basically characterized by not responding on the electromagnetic spectrum, which is what we use to do these observations. Since all the matter we know of generally does respond on this spectrum, that's why dark matter is considered to be "exotic".

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#204

Post by brudgers »

guscost wrote: post #134
brudgers wrote: post #109

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 some…

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 the…

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.

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#205

Post by TrainedMonkey »

sandworm101 wrote: post #181
ScottBurson wrote: post #176

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 mas…

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.

Gravitation does not technically interact with light either, but rather bends the spacetime the light travels through. So question is, what makes gravitons different?

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#206

Post by pja »

Semiapies wrote: post #76
scrumper wrote: post #47

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 co…

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...

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.

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#207

Post by kingkawn »

sandworm101 wrote: post #181
ScottBurson wrote: post #176

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 mas…

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.

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

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#208

Post by auntienomen »

kkylin wrote: post #200

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…

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.

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#209

Post by snowwrestler »

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?

Well for that explanation to scale up, the Oort Cloud would have to total about 5x the mass of the sun. That would have a pretty good chance of perturbing the orbits of all the planets, and vice versa.

A bit of Googling tells me that the current estimate of its mass is in the order of 5-10 Earth masses--not nearly enough to explain dark matter.

Re: Physicists Detect Gravitational Waves, Proving Einstein Right

#210

Post by contravariant »

sandworm101 wrote: post #181
ScottBurson wrote: post #176

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 mas…

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.

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).

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