Re: LIGO: Gravity Waves detected
Posted: Mon Feb 22, 2016 2:17 am
What effect would that gravity wave event have on a nearby nebula or star?
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It's as reliable as refrigerators, aircraft, or transistors.JoeP wrote:How reliable is the above?
Depends how big they are and how far away.JoeP wrote:If they can detect black hole collision from so far away, can other disturbances in the gravity field be detected?
It's a matter of scale. If we had a black hole to wave around, and something to wave it with, we could make detectable gravity waves, but that's pretty far from anything we're currently able to do.JoeP wrote:Such as moving a massive object around near the detector? I assume no, but do not understand why not.
No. This discovery does not prove that gravity is mediated by gravitons.JoeP wrote:Also, does this discovery mean that a particle like the graviton must exist to mediate gravitational force?
Sure, but there isn't anything else dense enough to make detectable gravity waves. If Jupiter and Saturn collided and merged, the gravity waves it would make would not be detectable by LIGO, and if there were anything less massive than a couple black holes somewhere close enough to the Solar System to make detectable gravity waves by colliding, we'd be able to see the perturbations in the orbits of the planets. We don't, and that's that.JoeP wrote:Another thought occurred to me: how does the LIGO team know that the gravity wave detection is due to the merger of two black holes, aside from the energy calculation? It seems to me that they are just picking the most likely explanation as to what most fits the expected space-time distortion and the rough distance of the source.
We only have two LIGO detectors; thus, we cannot pin down the exact direction to look in. When we get a third one up and running, then we'll be able to look and see if there's anything happening in the direction the gravity wave came from. Radio triangulation with only two receivers is possible because we look in a limited volume, on the surface of the Earth or within a few kilometers of it. In space, three are required to pin it down. If we watched all of the sky all of the time for GRBs or flashes or whatnot, we might be able to say, "Well, we saw a gravity wave and it was in this area, and we detected a GRB (or saw a flash) right over there that corresponds to it," but we don't have that capability yet either; we just don't have enough telescopes.JoeP wrote:It isn't close enough to get any other supporting data, was it? e.g. gamma burst.
Actually, if you turn your argument around, you'll see that it's not that there's something different about gravity, it's that we only have half of the story when we talk about gravity.Tom Ligon wrote:This is why I have a problem with gravitons. There's something different about gravity. If gravity were mediated by a particle, even one moving at the speed of light, how would gravity escape a black hole at all? If light can't, why should a graviton?
Correct: he made a field theory, not a quantum theory, nor a quantum field theory.Tom Ligon wrote:Einstein didn't postulate gravitons, he postulated a distortion of space-time.
Correct.Tom Ligon wrote:Gravity isn't emitted from the black hole, the black hole distorts space-time. And as the merger of the two black holes approaches, their furious orbiting shakes the blanket of space-time enough to cause waves.
If you like string physics, then spacetime (i.e. dimensionality) is the ultimate "stuff" of which everything else is made. So-called "superstrings" are distortions in spacetime + extra dimensions, which in order to exist must resonate to be stable, and which resonate in some or all of these dimensions and form everything we see as matter and energy; they are self-sustaining solitons in these dimensions, wrapped around and moving in these dimensions and remaining in existence because otherwise there would be no mass/energy conservation when they disappeared. Gravity, then, is merely a distortion of spacetime without any distortion of these other dimensions that create electromagnetism and the strong and weak nuclear forces, and electromagnetism and the strong and weak nuclear forces are distortions that involve these other dimensions as well as spacetime. "Gravitons," then, become minute distortions of the spacetime dimensions, and are weak because spacetime is large, and the dimensions warped by electromagnetism and the strong and weak nuclear forces are small. This explains gravity's weakness, along with many other of its characteristics, and also eliminates the infinite probabilities that plague other quantum gravity theories. Unfortunately, this is not a theory; it is only a hypothesis. It's a great explanation, with a lot of really good features, but there's no way to disprove it.Tom Ligon wrote:Which leaves us still wondering what space-time really is. Quantum entanglement? An ether? The whole idea begs for there to be some edifice out there which still allows Special Relativity to operate as if there were no ether.
String physics explains why gravity is different in kind: it is distortion of the four large dimensions, space and time, whereas the other forces are distortions of the remaining six plus one dimensions: one for electromagnetism, two for the weak nuclear force, three for the strong nuclear force, and one more that relates the theories of strings that have ends to the theories of strings that link back to themselves. The difference may be because gravity affects time as well as space, and time is different: it is hyperbolically symmetric to the other dimensions, rather than circularly symmetric as the space dimensions are to one another and to time. No one has determined what type of symmetry the additional dimensions postulated by string physics have either to the ordinary spatial dimensions or to time; this is the largest current mathematical problem with string physics.Tom Ligon wrote:I believe gravity is different in kind from the other forces, and until that is accepted I expect it will make monkeys out of the people trying to unify it with the other forces. We're obviously still missing about 96% of physics since we are pretty sure dark matter and dark energy exist, but have no clue what they are, and we base their existence on the fact that gravity does not seem to work like it should. Dark matter is known only as gravity with no visible matter associated with it. Dark energy only because it seems to be an anti-gravity push affecting the expansion of the Universe.
More likely it will supplement and illuminate our findings using light, radio, X-rays, and gamma rays. It's the radiation of the only force but electromagnetism that we can expect to detect at astronomical distances; the strong force is limited by relativity and its own nature to distances around the size of an atomic nucleus, and the weak force is limited by the instability of its bosons to similar distances.Tom Ligon wrote:My hope for LIGO is that it turns up something we've been too blind to see, something we are not even looking for. Maybe we'll think it is a malfunction at first, maybe a diurnal zero drift, or noise, and finally realize we've got some signal.