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...?
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...?
This would be true in a static universe, but, during the 1.2 billion years the waves have been traveling, the universe was experiencing accelerating expansion.
For example, the edge of the observable universe is about 46.5 lightyears away, while the universe is thought to be 13.8 billion years.
If they build a third observatory, can they triangulate where in the universe the events are occurring?
Even with just two LIGO locations, they were able to give a very rough estimate of the source location during the livestream this morning. (It was somewhere kinda in the direction of the Magellanic clouds. Probably.) Once advanced VIRGO comes online (later this year?) we'll have three, which will significantly improve directional accuracy for much of the sky. And when KAGRA turns on in Japan sometime around 2018, we'll have four. During the livestream this morning, someone said that would lead to source locations accurate to within 5-10 degrees on the sky.
" On 14 September 2015, while Drago was on the phone with a LIGO colleague in Italy, his pipeline sent him an email alert—of which he receives about one each day—telling him that both LIGO detectors had registered an “event” (a nonroutine reading) 3 minutes earlier, at 11:50:45 a.m. local time. It was a big one. “The signal-to-noise ratio was quite high—24 as opposed to [the more typical] 10,” he says."
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…
Gravitational waves are a prediction of classical linearlized gravity - gravitational waves are to (classical) gravitons what light waves are to photons.
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…
Gravitational waves are a prediction of classical linearlized gravity - gravitational waves are to (classical) gravitons what light waves are to photons.
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…
Skepticism is healthy most of the time.
In this case I don't know if your skepticism is warranted.
1st: Paper said that the waves are redshifted to a certain degree (it's in the abstract) [1], ergo 1.3 billion light-years away in space-time. I'm not thinking you want to be so fundamentally skeptical.
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!
It was mentioned during the press conference today that gravitational waves are not affected by interstellar/intergalactic dust the same way light is. In theory, once our detectors are good enough we should be able to use gravitational wave astronomy to peer all the way back to the big bang!
How do the detectors work? In my mind they don't make physical sense. They're saying the distance between the mirrors changes, but I don't understand how that's possible in this context. Let's say a gravitational wave compresses space. To someone inside that compressed space, there should be no noticeable difference. Light will still flow the same way through the compressed space at the same speed relative to the com…
I think the crucial detail you are missing from the article is this: "According to the equations physicists have settled on, gravitational waves would compress space in one direction and stretch it in another as they traveled outward." LIGO is two sets of 2 L-shaped antennas spread far apart on the globe, so that we can compare the compression of space in orthogonal directions and measure the very short delay between…
Here's my re-statement of this confusion, isn't everything we can experience embedded in time-space, including the LIGO experiment itself? So how is there any relative shift allowed to be detected when everything we know is fundamentally intrinsic to time-space? That is, I too would appreciate having this mis-conceptualizing, of mine, cleared away.