Jump to content

Each member of the binary produces G-rad at an equal rate. Why?


Robittybob1
 Share

Recommended Posts

I would like to discuss how gravitational radiation is produced.

There is a formula for the amount.

But I what to try and uncover the mechanism behind it. Why is it produced and so I have started this thread so even the most speculative ideas can be thrashed out.

 

Is there anyone who has got a clue as to how to begin answering the question?


Here is a paper mocking us with a clue: Solve this riddle: "Gravitational Radiation is to gravity what light is to electromagnetism".

 

Do they really mean that as "light" and not photons?

http://math.ucr.edu/home/baez/physics/Relativity/GR/grav_radiation.html

 

 

Gravitational Radiation is to gravity what light is to electromagnetism. It is produced when massive bodies accelerate. You can accelerate any body so as to produce such radiation, but due to the feeble strength of gravity, it is entirely undetectable except when produced by intense astrophysical sources such as supernovae, collisions of black holes, etc. These are quite far from us, typically, but they are so intense that they dwarf all possible laboratory sources of such radiation.

They then say "It is produced when massive bodies accelerate". Is that in anyway similar to light?

They also say "gravity waves are fluctuations in the tensorial metric of space-time." Does that mean gravity waves and gravitational radiation are the same?

"The speed of gravitational radiation (Cgw) depends upon the specific model of Gravitation that you use." Is this the same as the speed of gravity?

We need to know about bosons as well!


I'm tending to the thought that there are gravity waves and the waves are waves of gravitational energy. Would that be like a light beacon with a pulse frequency and intensity made up of photons with a wavelength and energy that has some relationship with the pulse frequency and intensity, inasmuch as the total power output is contained by the frequency and intensity is within the emitted photons.


Paper http://ned.ipac.caltech.edu/level5/ESSAYS/Boughn/boughn.html seems to answer the previous questions.

Link to comment
Share on other sites

Here is a paper mocking us with a clue: Solve this riddle: "Gravitational Radiation is to gravity what light is to electromagnetism".

 

Do they really mean that as "light" and not photons?

Light is photons. Photons are light. In this context they are interchangeable.

 

They then say "It is produced when massive bodies accelerate". Is that in anyway similar to light?

When you accelerate a charged particle, it emits EM radiation. If gravitational radiation is analogous, then the details of the radiation depend on the acceleration. If so, each mass would not produce the same radiation in a binary of unequal masses.

Link to comment
Share on other sites

Light is photons. Photons are light. In this context they are interchangeable.

 

 

When you accelerate a charged particle, it emits EM radiation. If gravitational radiation is analogous, then the details of the radiation depend on the acceleration. If so, each mass would not produce the same radiation in a binary of unequal masses.

Light = photons thanks.

The next bit I still don't agree with yet. "Each mass" are you saying that to mean "each body in a binary"? For the lighter mass in your thinking was that lighter mass going to produce more or less radiation?

The larger mass has more matter and if each component of each atom produces some part of the G-rad a larger mass even though not accelerated as much may still overall produce the same amount as the lighter body.

Force = mass * acceleration so mass or acceleration will produce the product. Smaller acceleration could be countered by increased mass. The two bodies of the binary are pulling with equal force. They have the same centripetal force.

Besides that if the waves are produced from individual bodies in the binary the "chirp" amplitudes didn't show any tendency to peak at every second wave crest (even though it wouldn't be the easiest thing to pick as the intensity is rising up till the ringdown). If you thought that there was a second wave peak does it correspond to the wave produced by the less massive of the two BHs?

http://journals.aps.org/prl/pdf/10.1103/PhysRevLett.116.061102

On the other thread http://www.scienceforums.net/topic/93875-warped-spacetime-around-bh-and-the-barycenter/page-2#entry910467 I identified peaks 4, 6 8 as coming from the more massive BH and these crests look slightly lower than the preceding ones depending on what part of the reconstructed waves you look at, so you could be correct. I would take this to mean that the BHs are not acting as true binary objects and a degree of chaotic behaviour is happening.

 

Do you agree with some parts of that?

 

Are you familiar with the terms "numerical relativity" "reconstructed (wavelet)" and "reconstructed (template)" as used in the LIGO paper?

Edited by Robittybob1
Link to comment
Share on other sites

Are you familiar with the terms "numerical relativity" "reconstructed (wavelet)" and "reconstructed (template)" as used in the LIGO paper?

You can only explicitly write down wave solutions to Einstein's field equations in simple cases (pp-waves for example). To work with more realistic sources and waves you need to put the field equations on a computer and use numerical methods. This is basically numerical relativity.

 

The experiments then have to match what they see with possible known sources of the gravitational radiation. This is what they mean by a template. They have a catalogue of wave profiles and their sources. (Kip Thorne showed us some of these templates a couple of months back)

Edited by ajb
Link to comment
Share on other sites

There is a formula for the amount.

 

There isn't really (except for the simplest cases, as ajb says). Which is why they have to use simulations.

 

But I what to try and uncover the mechanism behind it. Why is it produced and so I have started this thread so even the most speculative ideas can be thrashed out.

 

It doesn't need any speculation, does it? It is well-explained by existing theory.

 

Do they really mean that as "light" and not photons?

 

I would say, in this context, they mean light (i.e. electromagnetic waves) rather than photons, specifically. Although the distinction is a bit artificail as they are both descriptions of the same thing.

 

They also say "gravity waves are fluctuations in the tensorial metric of space-time." Does that mean gravity waves and gravitational radiation are the same?

 

They actually mean "gravitational waves" not gravity waves. But, yes, I would say that gravitational waves and gravitational radiation are different words meaning the same thing; like electromagnetic radiation means electromagnetic waves.

 

"The speed of gravitational radiation (Cgw) depends upon the specific model of Gravitation that you use." Is this the same as the speed of gravity?

 

What do you mean by the speed of gravity? You can only measure the speed of changes in gravity, and that is a gravitational wave.

 

We need to know about bosons as well!

 

Why? There are no bosons in GR. There is no quantum theory of gravity. There is no complete model for gravitons or evidence for their existence.

 

I'm tending to the thought that there are gravity waves and the waves are waves of gravitational energy.

 

Well, gravitational waves certainly have energy.

The larger mass has more matter and if each component of each atom produces some part of the G-rad a larger mass even though not accelerated as much may still overall produce the same amount as the lighter bod

 

I doubt you need to worry about the contribution of individual atoms. For one thing, their masses and individual movements are negligible compared to the mass of the whole body. Also, in most cases where we are likely to detect gravitational waves (black holes, neutron stars) there are no atoms.

(You have a bit of a tendency to go off into irrelevant details; I think this is one those cases.)

Link to comment
Share on other sites

Light = photons thanks.

As Strange points out, the use of "light " was most likely deliberate, because this is a classical (not quantum) theory.

 

The next bit I still don't agree with yet.

Which has nothing to do with its veracity.

 

"Each mass" are you saying that to mean "each body in a binary"?

Since we're talking about binaries, yes. I thought was obvious.

 

For the lighter mass in your thinking was that lighter mass going to produce more or less radiation?

The larger mass has more matter and if each component of each atom produces some part of the G-rad a larger mass even though not accelerated as much may still overall produce the same amount as the lighter body.

Force = mass * acceleration so mass or acceleration will produce the product. Smaller acceleration could be countered by increased mass. The two bodies of the binary are pulling with equal force. They have the same centripetal force.

 

As I said, in EM, the details of the radiation depend on the acceleration. So if GR is behaving the same way...

 

Besides that if the waves are produced from individual bodies in the binary the "chirp" amplitudes didn't show any tendency to peak at every second wave crest (even though it wouldn't be the easiest thing to pick as the intensity is rising up till the ringdown). If you thought that there was a second wave peak does it correspond to the wave produced by the less massive of the two BHs?

http://journals.aps.org/prl/pdf/10.1103/PhysRevLett.116.061102

 

On the other thread http://www.scienceforums.net/topic/93875-warped-spacetime-around-bh-and-the-barycenter/page-2#entry910467 I identified peaks 4, 6 8 as coming from the more massive BH and these crests look slightly lower than the preceding ones depending on what part of the reconstructed waves you look at, so you could be correct. I would take this to mean that the BHs are not acting as true binary objects and a degree of chaotic behaviour is happening.

 

Do you agree with some parts of that?

 

I agree there's another thread.

 

I doubt that one can correlate specific peaks with individual masses. They would be oscillating at the same frequency, so I don't see why the frequency of the emitted radiation would be different. They would simply be contributing different amounts of energy to it.

Link to comment
Share on other sites

As Strange points out, the use of "light " was most likely deliberate, because this is a classical (not quantum) theory.

 

Which has nothing to do with its veracity.

 

Since we're talking about binaries, yes. I thought was obvious.

 

 

As I said, in EM, the details of the radiation depend on the acceleration. So if GR is behaving the same way...

 

 

I agree there's another thread.

 

I doubt that one can correlate specific peaks with individual masses. They would be oscillating at the same frequency, so I don't see why the frequency of the emitted radiation would be different. They would simply be contributing different amounts of energy to it.

I was really making sure mass was not some measurement of mass like a kg .

So you are sure that more mass won't make up for the lack of acceleration. I'm a bit taken back by that sorry. How could you convince me 2 * 1kg masses accelerated at half the rate won't produce the same GE as a single 1 kg mass accelerated at the full rate?

 

They are definitely oscillating at the same frequency but the waves are grouped, there is a slight change (1 millisec approx) in phase (that might be the right terminology). I have done my best in trying to explain it before and it is late here I'm just too tired to have another go at it ATM.

Thanks for your views even if we still disagree.

Edited by Robittybob1
Link to comment
Share on other sites

I was really making sure mass was not some measurement of mass like a kg .

 

kg is a measurement of mass, so I have no idea what you meant by this.

 

So you are sure that more mass won't make up for the lack of acceleration. I'm a bit taken back by that sorry. How could you convince me 2 * 1kg masses accelerated at half the rate won't produce the same GE as a single 1 kg mass accelerated at the full rate?

 

I don't know how to convince you. You seem quite immune to science when it disagrees with your personal notions.

 

You also seem quite happy to take statements out of context. Comparing 2 * 1kg masses accelerated at one rate and a single 1 kg mass accelerated at twice the rate was not the example under examination. If my statement does not make sense, perhaps it's because you changed the conditions of the example, and the answer to the new example is different.

 

They are definitely oscillating at the same frequency but the waves are grouped, there is a slight change (1 millisec approx) in phase (that might be the right terminology). I have done my best in trying to explain it before and it is late here I'm just too tired to have another go at it ATM.

Thanks for your views even if we still disagree.

Why are you trying to explain it instead of reading up on the physics that already explains it?

Link to comment
Share on other sites

 

kg is a measurement of mass, so I have no idea what you meant by this.

 

 

I don't know how to convince you. You seem quite immune to science when it disagrees with your personal notions.

 

You also seem quite happy to take statements out of context. Comparing 2 * 1kg masses accelerated at one rate and a single 1 kg mass accelerated at twice the rate was not the example under examination. If my statement does not make sense, perhaps it's because you changed the conditions of the example, and the answer to the new example is different.

 

Why are you trying to explain it instead of reading up on the physics that already explains it?

When you said "If so, each mass would not produce the same radiation in a binary of unequal masses" I was just confirming whether you are looking at these effects on mass on a per kilogram basis. I accept my question was unnecessary now, sorry.

 

Do you know the answer whether or not it had "changed conditions"?

The whole discussion is difficult, for we are talking about accelerations, so there are forces, and these are acting on masses, to cause an effect called G-rad predicted by Einstein who explained gravity without forces.

 

Why - I'm looking for the keywords to look up. All day I'm looking into these effects. But my background in maths is not good enough ATM to read detailed papers loaded with math. So those sorts of explanations don't work for me.

Link to comment
Share on other sites

..... But my background in maths is not good enough ATM to read detailed papers loaded with math. So those sorts of explanations don't work for me.

You need to fix it if you want to go to that level, and understand it. I'm not very competent myself in maths but it seems clear to me, that you expect people who are competent to verbalise everything when, in fact, these concepts are essentially purely mathematical.

Link to comment
Share on other sites

..... each mass would not produce the same radiation in a binary of unequal masses.

Are you saying the lighter body will be radiating more energy? Why? I think the answer must be because it is being accelerated. So where does the force come from? It can only come from the gravitational attraction of the more massive BH.

 

If energy and mass are equivalent will the loss of energy from the smaller BH mean it is losing mass at a greater rate and will this change the orbital dynamics?

You need to fix it if you want to go to that level, and understand it. I'm not very competent myself in maths but it seems clear to me, that you expect people who are competent to verbalise everything when, in fact, these concepts are essentially purely mathematical.

I am learning math too but it isn't something you can jump in at the deep end and learn to swim. I do think in words rather than equations, you're right about that.

Link to comment
Share on other sites

Are you saying the lighter body will be radiating more energy? Why? I think the answer must be because it is being accelerated. So where does the force come from? It can only come from the gravitational attraction of the more massive BH.

 

!

Moderator Note

 

The (rhetorical) question here is why do you think this? Because if it's your gut, then it has NO PLACE in the discussion, even is speculations, but certainly in a mainstream thread. This is a SCIENCE discussion board. You have to bring some science to the conversation. Your posts lack this; it's just you waving your hands. Every time in the last several days that a similar situation has come up, you have failed to point to any physics that supports your ideas. It's just your gut feeling.

 

I am not alone among the staff in saying we're getting tired of this.

 

In mainstream threads you can ask questions, but you are not to be positing anything not supported by mainstream physics there. That means you have a citation to offer up from a credible source. In speculations, you may develop a model, or otherwise present evidence or a way to test the idea you have. But if you can't, then it falls short of what we expect. Your posts of late have gotten worse at following these rules.

 

You've been here about 1.5 years and have ~2400 posts. You do not get any benefit of the doubt when it comes to not following the rules.

 

You should not have to be told not to respond to this in the thread.

 

Link to comment
Share on other sites

Does this picture of fieldlines assist our understanding?

 

Maybe. But, because the relationship between electromagnetism and gravity is an analogy it might just confuse you.

 

I suppose, in this analogy, the "fieldlines" would be equivalent to the geometry of space-time. But the mathematics of electromagnetism and GR are completely different. And therefore the effect of moving charge/mass, are completely different.

Link to comment
Share on other sites

 

Maybe. But, because the relationship between electromagnetism and gravity is an analogy it might just confuse you.

 

I suppose, in this analogy, the "fieldlines" would be equivalent to the geometry of space-time. But the mathematics of electromagnetism and GR are completely different. And therefore the effect of moving charge/mass, are completely different.

Are there ones like that for gravitational radiation? Wasn't it from the same analogy that Einstein made the prediction of G-rad?

The fieldlines would be more like lines of gravitational force wouldn't they?

Edited by Robittybob1
Link to comment
Share on other sites

Are there ones like that for gravitational radiation?

 

You have seen diagrams of the geodesics of space-time being curved by the presence of mass? That would be the equivalent analogy.

 

Wasn't it from the same analogy that Einstein made the prediction of G-rad?

 

I haven't seen the details (and I don't read German) but I assume he found that there was a wave solution to the field equations. (i.e. not by analogy)

Link to comment
Share on other sites

 

You have seen diagrams of the geodesics of space-time being curved by the presence of mass? That would be the equivalent analogy.

 

 

I haven't seen the details (and I don't read German) but I assume he found that there was a wave solution to the field equations. (i.e. not by analogy)

I'll see if I can get a translation.

Link to comment
Share on other sites

 

You have seen diagrams of the geodesics of space-time being curved by the presence of mass? That would be the equivalent analogy.

 

 

I haven't seen the details (and I don't read German) but I assume he found that there was a wave solution to the field equations. (i.e. not by analogy)

 

I think it is also that if you hold as true that changes in an effect propagate and that this propagation (indeed any causal transmission of information) is limited in speed then you get a "change-front" spreading from the source.

 

This part is strictly analogous with the model for electromagnetic radiation - and the famous picture of the charge with "rays" spreading out and when the charge moves all the lines have a kink (except for +ve /-ve direction of motion). What is different is what the propagation of the change is manifest through, and what physical changes in orientation cause a change in effect.

 

That these "change-fronts" which we know are gravitational waves must carry energy away is a result of the EFE I believe

Link to comment
Share on other sites

That paper by S Carlip has a strange paragraph with an option in it. http://arxiv.org/pdf/gr-qc/9909087.pdf

 

 

One could again try to formulate an alternative theory in which gravity propagated instantaneously, but, as in electromagnetism, only at the expense of “deunifying” the field equations and treating gravity and gravitational radiation as independent phenomena.

Has anyone tried to do that by treating "gravity and gravitational radiation as independent phenomena?

So does that mean we could have gravity waves (a single wave) and gravitational radiation (coming from each member of the binary)?

 

Gravity waves is what is being measured by LIGO but it is the loss of energy via the production of gravitational radiation that allows the BBH to experience relativistic orbital decay and final merger. Gravity waves travel at the speed of light but gravity ??.... :)

 

I like the idea treating the two as independent phenomena.

 

.

Link to comment
Share on other sites

Has anyone tried to do that by treating "gravity and gravitational radiation as independent phenomena?

Not that I know of. You are thinking about having some other field on space-time that can carry away some of the energy and angular momentum associated with gravitational phenomena? My first thoughts are something akin to the inflaton or curvaton field. However in models of the early universe people think about gravitational waves generated by these fields.

Edited by ajb
Link to comment
Share on other sites

Not that I know of. You are thinking about having some other field on space-time that can carry away some of the energy and angular momentum associated with gravitational phenomena? My first thoughts are something akin to the inflaton or curvaton field. However in models of the early universe people think about gravitational waves generated by these fields.

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 concur I cannot think of any conjecture of gravity and gravitational radiation as being separate

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.

Edited by Robittybob1
Link to comment
Share on other sites

I'm trying to understand the EFE but I have no one to teach me

 

This is a good introduction: http://math.ucr.edu/home/baez/einstein/

 

We've been discussing the Shapiro time delay and it was pointed out that this was forbidden by GR equations.

 

No, that isn't what was said at all. The Shapiro time delay is a consequence of GR. That is why you can't solve the equations and then add in an extra delay.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.