Robittybob1

Th They are not magnetic but points (just compass points). I could have used the clock face but there was no hour number that represented NE, SE, SW or NW it was going to get too complicated to say "half past one" for NE etc. https://en.wikipedia.org/wiki/Gravitational_wave#/media/File:Quadrupol_Wave.gif Are the effects of gravity waves spread out through space evenly in all directions? If they were linear polarized I would say they are not evenly spread. With the setup as described you would see periodic strains on the test masses in the Celestial LIGO. Did you not see that? OK with traditional Newtonian gravity the effects were thought of as instantaneous but the generator of these instantaneous effects still had to go through the motions. That becomes a major difference in that under Newtonian Gravity the merger happened as the signal was received by LIGO rather than 1.3 billion years later. But that wasn't what I was thinking about in the thought experiment, I was thinking whether we would see the polarization pattern and then work out how much force we would see back on Earth using Newtonian gravitational force calculations.

I thought we were saying that the GW had passed close to another star as it traveled toward the Earth. I just could not see how the wave produced within/by the binary would be gravitationally delayed by the masses that produced the wave in the first place. For that would mean it was produced by each mass within the binary separately and I was persuaded that it was the combined mass of the system that produced the wave, a circularly polarized wave, but if that wave passed another star, BH or galaxy on it way through space then it might be Shapiro time delayed. You would have nothing to compare the delayed wave with, so no one could determine if it was delayed. I can see how one member of a pulsar binary affects the pulsar signal, but my doubts were about the GW wave produced from the same pulsar binary, what effect would it have if it was eclipsed? Mordred seems to go for the GW being produced by the system and not by the individual masses #9

That is sort of what I was getting at. With the quadrupolar waves there seems to be varying amounts of movement of the test particles around the ring. With the circular polarisation pattern the points (using the points of the compass to describe where I'm looking) at NE SE SW NW points move less than the points N, E ,S and W. Does that mean if I wanted to spread the effects throughout space that the whole effect wouldn't be reduced at the inverse square law with distance? http://www.johnstonsarchive.net/relativity/gravwavepic.html Some of the animations on this site really show this up http://www.universetoday.com/127255/gravitational-waves-101/ Could Newtonian gravity ever create wave patterns like that?

Because the BHs or masses are orbiting they are accelerating. (Due to the curved motion) Would the test masses cause fluctuating pressure on the ends of the celestial LIGO? (C.LIGO set-up as described above.) We are not asking about gravity waves. "And LIGO would detect nothing because there would be no gravitational waves." So did you try and answer the question? "It would detect nothing". A detection in this thought experiment was increased or decreased pressure on the end of the C.LIGO arm. Are you saying the test mass would not change the pressure it exerted on the end of a C.LIGO arm either inside or outside the orbits of the binary BHs?

This Mordred states "Now in the Binary BH scenario NEITHER BH produces gravity waves. They are both symmetric rotating objects." Are they really "symmetric rotating objects"? So is he saying each BH is accelerating but neither produces a gravity wave? Wikipedia states : https://en.wikipedia.org/wiki/Gravitational_wave#Sources It is unfortunate they use words like "objects", so I would say a BH is an object. "in the case of two planets orbiting each other, it will radiate gravitational waves." It is also unfortunate that they used the plural "waves". Should they have said "in the case of two planets orbiting each other, they will radiate a single gravitational wave"? Maybe they say "waves" because there are two waves per orbit for the binary? Wikipedia basically states each orbiting object will radiate waves. .

I'm only looking at which way that the test masses would be moved by gravity at this stage.

In the whole quote http://www.scienceforums.net/topic/93995-shapiro-or-shapiro-like-delay-of-gw-signals-split/page-3#entry911378 he is talking about these BHs Were the black holes in GW150914 moving at a constant velocity? I accept that a "symmetric rotating object of constant velocity will not produce waves". I was just questioning whether the BHs in a binary orbit are moving at a constant velocity. @Strange - Were the BHs moving at a constant velocity?

I asked a question about mass as well, so could you explain that bit too please? You say "You need mass." ... There is plenty of mass in the BBH. So where abouts do we need this mass please?

That is quite a hard post to follow-on to. Are you OK? The graph could be like your paintings going to the edge of the paper but the scene they represent goes on forever.

@ Mordred - Where did you get this from? "A Shapiro delay will affect all frequencies and polarizations of the chirp equally." Aren't both bodies being accelerated in their orbit? They are not traveling in a straight line but following an ellipse so they don't have a constant velocity. Please in what frame of reference are they traveling with constant velocity? What do you mean by "position"? Where would position be determined from? http://www.physics.usu.edu/Wheeler/GenRel2013/Notes/GravitationalWaves.pdf

EM ok Thanks. You say "You need mass." so was that like the Sun in the path of the GW? For there is plenty of mass in the BBH. So where abouts do we need this mass please? I read up about Shapiro time delay and that "mass" in their case seemed to be the Sun. So could we use the sun again in this case of a GW? We don't know precisely where GW150914 was so it seems impossible to nominate some other mass that the wave passed. I just fail to see how EFE could have taken all these factors into account. What assurance can Mordred give me that this is in the GR equations? @DanMP have you done the Force calculations on a 1kg test mass and the BH masses (M1 and M2) in those arrangements? If you were up there standing close to the binaries orbiting you would need to calculate whether G*m1/(r1^2) + G*m2/(r4^2) < G*m1/(r2^2) + G*m2/(r3^2) where r1 is the distance to M1 when it is closest and r4 is when M2 is furthest away on opposite side of the orbit and r2 and r3 are the side by side distances back to your position.

If it requires active cooling between those temperatures it sounds like a problem for the cooling apparatus may breakdown. What sort of danger would the operators be in if the cooling mechanism failed? Where is equation 2?

What was E&M an abbreviation for please? Was it energy and mass? I'm a bit confused by what you say here. "Shapiro delay is a GR effect, so it's already included when you do a GR solution." Are you saying it is happening and is in the GR model and therefore in the GW150914 "chirp"? I have been asking what arrangement of energy and mass is required to measure Shapiro time delay?

Could you ever get the gravity wave to pass back through the mass that caused it in the first place? There are two gravity waves per orbit so could it be the first wave interfering with the production of the second wave? It would all depend on the speed of gravity. Will the velocity dependent terms be cancelled within the BBH and gravity act as if it was virtually instantaneous? Is this another mental twister? I'd say it is impossible to get one BH around to the other side of the orbit to become affected by its own gravity. For that to happen it would have to be travelling faster than the SoL. But it could be moving fast enough to be experiencing a gravitational pull that is not directed from CoM from one body to the CoM of the other. So what situation will cause a Shapiro time delay of gravity? If it happens it will be happening all the time. Can we ever measure it? We would have to know what position we'd need to be in. Wikipedia discusses Shapiro time delay in connection to GWshttps://en.wikipedia.org/wiki/Shapiro_delay#Shapiro_delay_of_neutrinos_and_gravitational_waves No footnotes but further links are provided. I still imagine they are talking about GWs passing nearby a third massive body and not the two bodies that produced the GW. So we would need the BBH to infall when it was being inline with the edge of the Sun and the LIGO would need to be in a sensitive position on the Earth. All in all a very unlikely coincidental set of events. .

Not much below room temp as methane hydrates.

Keep the idea of "speed of propagation" but think in terms of gravity like Newton did. I only went down that track to overcome Strange's objection in #2 quote: There had to be some way to simplify the situation of the thought experiment, and that was to slow down the orbital rate and increase the distance so that Newtonian gravity would give a good approximation for I'm only looking at which way (way = direction and strength) that the test masses would be moved by gravity at this stage. Remember that change wave diagram. Even at mundane speeds you can get waves.

The Shapiro TD was found using light so if we just for a moment consider light rather than gravity for a while and then go back to gravity. I think this is valid for gravity and light travel at the same speed, so will light coming past the BH close to the photosphere show STD? In the final outcome it still must be a fail for more mass never blocks gravity but it definitely blocks light, so I don't see how we are ever going to get STD but hang on there is Gravitational time delay so gravity might be able to time delay the GW that passes through the BH itself! Now that is possible and has the same cause and effect too isn't it? [i'm not making claims but trying to see possibilities here.] Can a GW go through a BH? Would you get a GW blackout if it can't? (When the line of sight is an eclipse.) I understand what you are saying but I can't see a time delay of that magnitude being important for it is only ever a small fraction of the light or gravity (LoG) that will be affected. You will still have the normal chirp with a small amount of delayed GW hidden in this more massive signal, that any STDed GW is just lost somewhere in the signal as a type of background noise. With light you can pass it through tubes etc to isolate parts of it but that can't be done for gravity, so you will never isolate STD gravity from the background noise. There is plenty of background noise and where is that coming from? Was it partly STD gravity wave signals, who knows?

Could we make the distances great enough so the whole problem can be dealt with by Newtonian Gravity, in fact why not use the dimensions of a known binary pulsar? https://en.wikipedia.org/wiki/Hulse%E2%80%93Taylor_binary The LIGO mechanism would need to be modified to operate in the weightlessness of space. mirrors are set up so both arms can be crossed at their midpoints. There would need to be frictionless movement of the mass within the arm. We measure the pressure of the test mass on the ends of the arm. Let the star be exactly equal in mass. And let the orbit be circular. So the barycenter is exactly in the center of the two masses and ligo arms are centered on that too. Let the LIGO be stationary and the stars are moving around it. If the first arm (arm1) was centralised on the barycenter. Wouldn't the two test masses be attracted toward ends of the arm1 and register maximum pressure when the stars are inline with arm1. The pressure will be least when the stars are orthogonal to the first LIGO arm1. The same applies to the second arm (arm2) but the pressure is recorded at 90 degrees to arm1 .

If we took the LIGO right up to the binary the end of arm that pointed toward the barycenter would experience the greatest G force so the test particles would move apart particularly when they were in the eclipsed position. There was another thought experiment where we brought the LIGO right inside the orbiting binary. "Then, if the infall could take longer to allow us time to take the LIGO further and further away from the BBH but staying on the angular momentum vector, this toing and froing should continue." (The Hulse Taylor binary pulsar is expected to take several hundred thousand years to merger, so we can allow infall and bring the LIGO back to Earth in time to see the last second of the merger.) What sort of gravity wave patterns would we get from placing the LIGO in different orientations near or inside a BBH or binary pulsar? If then we withdraw the LIGO at ever increasing distances from the BBH what effects does this cause?

This was supposed to be DanMP's thread and I'm not advocating Shapiro TD but I appreciated that it was split off and allowed to be discussed separately. The last one was a rushed post as we were going out, and I probably didn't use enough words to explain my thoughts fully. "With the peaks always being spaced closer together as they infall it is really difficult to pick up even a microsecond change." What I was trying to say: So do you agree with the first bit? "the peaks always being spaced closer together as they (the BHs) infall" the frequency rises. But that frequency change is exponential (or something like that) so it is difficult to just say what the frequency is at any one moment to the next. In my understanding in the time it takes to form one wave, the "chirp" frequency may have risen by much more than 1hz maybe as much as 20-40 Hz per orbit. I can't just look at the wave of the "chirp" and mentally predict where the next wave is expected so how could you tell visually if the wave was out by 1 ms? (I should have said "millisecond" not "microsecond" sorry). So if Shapiro TD was possible (which is now doubtful??) and it just delayed part of a wave by less than a millisecond, how would one be able to see it in the GW 150914 "chirp" waveform?

As I said I'm not that great with those thoughts as yet, so your reasoning could be correct but to me it feels like "forbidden" ("can't" and "forbidden" are similar) for want of a better word. It was only a word that has come from me, from my misunderstanding, I never said I was quoting anyone.

Thanks both of you for those valuable links. Should keep me busy for a while!

Well that gives me some new words and ideas to follow up on. I don't know if you are following all the discussions but I came up with some interesting ideas of bringing the LIGO detectors right up to the BBH either within the binary or beside it . It seems then we can see the effects on the test masses even without gravitational energy (GE) production. (at least so I think, for no one has criticised the idea yet.) I could always be wrong for I'm exploring many different ideas to see if we can identify where the GE comes from. I'm trying to understand the EFE but I have no one to teach me, so from what you know can you see any reason why they can't be treated separately? We've been discussing the Shapiro time delay and it was pointed out that this was forbidden by GR equations. Can the same thing happen again? If it wasn't Carlip who gave the option I wouldn't feel like it was a possibility (yet the Gravity wave produced is a single wave) but there are two bodies falling toward each other so I can see the possibility of two Gravitational energy trails. That can only happen if gravity waves and gravitational energy are treated as separate yet connected phenomenon. One is the artifact of the acceleration of the orbiting binary, and the other allowing the binary orbit to decay so the frequency increases as they infall and produce the gravity wave "chirp". So they are very much connected through the effects of gravity acting at the speed of light.

Today after several days of being confounded by the speed of gravity issues I'm coming around to thinking light and gravity have the same path between A & B, the gravity strength is the one from the position you see a mass. This means no matter how tortuous the spacetime is warped between those two points gravity and light will always be in phase. Now this seems like a weird thought but can anyone find the fault in that. I did read something about this recently (I'll see if I can find confirmation of this). "http://math.ucr.edu/home/baez/physics/Relativity/GR/grav_speed.html""Does Gravity Travel at the Speed of Light?" explains it quite well and introduce the idea of gravitational radiation due to the not quite cancelled "velocity terms". This article https://medium.com/starts-with-a-bang/what-is-the-speed-of-gravity-8ada2eb08430#.1lb1mj5ya "What is the Speed of Gravity?" It is weird gravity proven to travel at the speed of light but the problems that this would cause is cancelled out (so gravity behaves as if it is nearly instantaneous) except where the mass accelerates (is in orbit). So the sun disappearing trick should be: we see the light for another 8 minutes but gravity is gone immediately (but no one says that either so I still don't get it!)

@Mordred - where did you get that statement from? It wasn't in the "Gravitational Waves" teaching aid.http://www.physics.usu.edu/Wheeler/GenRel2013/Notes/GravitationalWaves.pdf You make it sound the binary system has more mass than the BHs do. Is that their gravitational potential energy and their kinetic energy as well as their rest mass? Could briefly explain what you mean please?