Gravity Waves and the Fabric of Space-Time

[mmaayeh]

In the search and research of gravity waves in the universe, you have studies on how gravity waves propagate through the universe by colliding black holes or other immense objects.

Is there any indications on the attributes of Space-Time Fabric as a system either being at equilibrium, under damped, or over damped? If so then, what is the significance or impact in detecting gravity waves?

-- by Muhanned Maayeh, Madaba, Jordan
(pronounciation: Moo-hen-ned maya)

[WayneFrancis]

I'm reading your question over and over and I'm trying to understand what you are asking.

First while there are detectors looking for gravity waves as of yet none have been found.

As to the 2nd part, if I understand it properly, I would have to question how you would be able to tell if the "Space-Time Fabric" amplified or damped gravity waves and would it mean anything.

IE a gravity wave is the propagation of gravity through Space-Time. I don't see how "Space-Time" would alter the wave amplitude. I'm thinking I don't really understand what you are asking.

I've heard some complaints that we could not detect gravity waves because the size of our detectors would cause enough gravitational distortion to swamp any measurements but then I don't see how that is relevant with the current detectors.

Perhaps you could elaborate a bit more on your question for me, and maybe others.

[mmaayeh]

Yeah sure, let me try to clarify my question.

First, my background I studied engineering and as you know in materials or systems you can start a wave and then eventually it will damp out (I undertand it is due to other affects such as atmosphere, friction, gravity, etc.) Second, I am aware this is purely theoretical at this point and nothing has been detected to provide empirical data on gravity waves.

So, I started think about our universe as a system (so to speak) and if a large gravitational distortion due to merging super massive black holes can cause a wave then, is there any consideration of the fabric of Space-Time being a system where if a wave is generated will it be damped. If so then, what would the attribute of space-time be in this consideration. If not then, how would space-time be described? I hope this is a little clearer.

[astromark]

Welcome, and a good question; 'Mmaayeh' This is interesting to think about. My take on this would not be supported by any science I can direct you to but, just my considered opinion. There is no medium to slow the progress of your gravity wave. If such is real. The radial depletion of gravity force measured is a simple result of distance. The old square root of the 'with distance from' thingie depletion... It must be added that this is just my opinion.

[mmaayeh]

It seems like my very first posting here was confusing and unclear (sorry about that and bit of a disappointment).

So, I started to think about the implications one time on gravity waves and detection depending on attributes of space-time.

First, let's take the case you have two supermassive black holes merging. Theoretically this would produce a gravity wave that will propagate from the point of the event. Assume the wave does not encounter any other object or event to perturb the wave propagation.

So, if the universe is underdamped or no damping is applicable then, you would have a gravity wave with a given amplitude, wavelength, and frequency propagating more or less as is across the universe. So, this wave is not localized to the vicinity of the event. And, the energy of the wave is maintained for the lifetime of the universe (assuming this wave is not interfered or stopped by other objects in the universe) -- assuming the wave maintains the same energy always.

Now, if you consider that space-time is at equilibrium or over damped then, you would have a gravity wave with a given amplitude, wavelength, and frequency propogating from the event then, this wave will eventually begin to lose energy and decrease amplitude to zero or nearly zero (wave died). Therefore, this wave is localized or nearly localized to the event where we will never detect a gravity wave even if they do exist.

In contrast, if space-time is underdamped or no damping then, gravity waves are propogating every where around us and there should be some sort of pertubations detected directly or indirectly that would affect perhaps even celesitial objects moving about their orbits. Assuming you left time long enough to eventually produce an affect that can't be explained by standard orbital mechanics but, requires a relativitistic understanding to include gravity waves.

So, I guess in the field of study of gravity waves, is there any indications on the "attribute" or nature of space-time -- if this was considered at all. So, what is the implications for the LGO experiments on earth and future ones to be launched in space.

Also, what does this suggest about our current state or reality in a 3space - 1 time reality. Not sure, if this is any clearer or I just muffed this up again.

Anyone have any thoughts or a different understanding.

[mmaayeh]

I just wondered, if there was any science or indicators in general theory, for example, that can describe space-time to account for this and that can lead to some sort of observable phenomenon that could be accounted for by gravity waves. I guess to have a radial depletion of gravity force then, you need something to reduce the wave over distances. So, does space-time in itself do this or do you need another event to counter this?

[cfgauss]

I just wondered, if there was any science or indicators in general theory, for example, that can describe space-time to account for this and that can lead to some sort of observable phenomenon that could be accounted for by gravity waves.

Uhm, yes?
http://nobelprize.org/nobel_prizes/p...993/press.html

[mmaayeh]

Thank you, this was a very interesting article. I enjoyed reading it.

So, what was found that there is indirect detection of gravitational waves but, direct measurements have not been made yet.

Nice, so two pulsars tightly orbiting each other are calculated to lose "orbit period by about 75 millionths of a second per year", which is suggested or predicted by General Relativity, is due to energy loss by gravity waves.

Then, assuming that there is no other interference by other bodies or gravity waves, in general relativity does the propagation of gravity waves in space-time continue forever within the universe? Or, does the gravity wave begin to damp out due to some inherit attribute of space-time?

If there is some sort of dampening nature then, gravity waves will most probably be localized nearly to the vicinity of the event and direct detection will be not possible? Otherwise, future detection is possible.

[cfgauss]

Any damping would violate conservation of energy.

[mmaayeh]

Thank you, yes that makes sense if you can lose energy while propagating then, you are destroying energy which is not in keeping with the law of conservation. So, theoretically then, if gravity waves are possible then the universe is probably a noisy place (so to speak).

[Cougar]

So, I guess in the field of study of gravity waves, is there any indications on the "attribute" or nature of space-time...

I'm not so sure a gravitational wave is a wave through spacetime, but rather a wave of spacetime.

[trinitree88]

I'm not so sure a gravitational wave is a wave through spacetime, but rather a wave of spacetime.

Cougar. Correct, and for the umpteenth time, spacetime is not empty. It contains: 1. the CMB, the putative relic radiation from the creation of the universe. Presence of it causes cosmic rays to have an upper threshold of energy.see:http://en.wikipedia.org/wiki/GZK_paradox
2. the zero point radiation dictated by quantum mechanics, presence of it causes a similar but significantly smaller effect as #1.
3. the neutrino sea, both relic and astrophysical in origin, presence of it also causes a similar effect, as yet indeterminate because of the unknown cross - sections at low energy

cfgauss is correct that "damping" would violate conservation of energy in empty spacetime, but that unfortunately is impossible to make. There is no known way to remove the 2. zeropoint radiation, nor the 3. neutrino sea. You can in principle and practice cool things to a few millikelvins and rid yourself of the CMB though. pete

As for gravitational waves, twas not I who published the claims of them for SN1987a, but over 20 different peer-reviewed journal articles hold to them. As yet, the mainstream physics community thinks the signal was not sufficiently distinct from the near-noise level.

[mmaayeh]

Here is another related question(s), space-time curves under the influence of gravity and most probably waves under the influence of immense gravitational interaction of massive objects. Can it wave under lower gravitational interactions. If I understand correctly the Sun, Earth or moon curves space-time but, can smaller objects interacting cause waves in space-time? Or, do you require a lower limit on the energy or mass required to have a gravity wave propagate in space-time?

Also, a related question regarding the properties of space-time under different wave conditions (please see split post by Astaro -- http://www.bautforum.com/space-astro...ference.html): "Assuming gravity waves exist, is it possible (possibly when two waves interfere?) for an area to acquire, even temporarily, a negative gravitational curvature?
Or, to picture it another way, if gravity stretches space-time, could two interfering waves lead to momentary compression?"

So, what can you expect to see under different conditions of waves where you have compression, amplification, stretching, etc.

Also, is it in the realm of possibility to setup a destructive harmonic in the universe to shake itself apart? kind of like bridges under the correct conditions between structure and wind turbulence.

Also, if waves due exist then, do you think this can account for the imbalance in the CMB that caused the formation of galaxies and everything else?

What do you all think?

[Cougar]

...space-time curves under the influence of gravity and most probably waves under the influence of immense gravitational interaction of massive objects. Can it wave under lower gravitational interactions?

I know of no reason to forbid small masses in motion from causing g-waves. I'd guess the wave amplitude would be proportional to the mass. But the actual effect would be unimaginably minute.

Assuming gravity waves exist, is it possible (possibly when two waves interfere?) for an area to acquire, even temporarily, a negative gravitational curvature?

I expect two (or more) gravitational waves do interfere. But in the most extreme case, they could only cancel each other out, hence zero effect for that point at that time. "Negative" doesn't seem to exist in this domain.

Also, is it in the realm of possibility to setup a destructive harmonic in the universe to shake itself apart?

If I told you that, you would be subject to extraordinary rendition.

Also, if waves due exist then, do you think this can account for the imbalance in the CMB that caused the formation of galaxies and everything else?

Hmm. The early universe was in thermal equilibrium, so the mass density was pretty much uniform everywhere. Vilenkin talked about the gravitational wave background, but I'm not picturing how it's generated. Early structure formation is indeed still an open question as far as I know, but we do have the CMB power spectrum that is statistically consistent with the theory of inflation, which appears to be one contribution to structure formation. Then there's the dark matter, which would not be subject to the thermal equalizing forces, so would be free to form structure gravitationally much earlier than baryonic matter....

[mugaliens]

I'm not so sure a gravitational wave is a wave through spacetime, but rather a wave of spacetime.

Exactly. I believe this conceptualization has proven to be one of the more difficult hurdles for most people to grasp, based on comments made herein and elsewhere.

One of the reasons I asked is that if/when they are confirmed, we may not know how "pure" they are (e.g., BB plus other GWs interfered with -- say, constructive interference may result in deceptively large GWs).

If by "wave" you mean a fluctuation in the gravimetric potential of spacetime, then the occurrence of such interference would be infrequent, as it occurs only when mass is converted to energy and vice-versa. Even then, it has to occur on massive scales, such as supernova explosions, for us to detect it.

[cfgauss]

Hmm. The early universe was in thermal equilibrium, so the mass density was pretty much uniform everywhere. Vilenkin talked about the gravitational wave background, but I'm not picturing how it's generated. Early structure formation is indeed still an open question as far as I know, but we do have the CMB power spectrum that is statistically consistent with the theory of inflation, which appears to be one contribution to structure formation. Then there's the dark matter, which would not be subject to the thermal equalizing forces, so would be free to form structure gravitationally much earlier than baryonic matter....

AFAIK, gravitational effects are way too small for us to detect. I believe that the overall detailed random distribution of stuff we see is due to quantum fluctuations in the very early universe, so because we only expect the universe to be "on average" smooth, it seems reasonable to expect a gravitational wave background. Though I honestly don't know any details about it, but it's apparently fairly well described in the literature.

[Cougar]

...the occurrence of such interference would be infrequent...

Yeah, I've been thinking about that. As an example, we've got electromagnetic waves filling the universe, but constructive and destructive interference doesn't seem to be playing any big role...

[mugaliens]

Yeah, I've been thinking about that. As an example, we've got electromagnetic waves filling the universe, but constructive and destructive interference doesn't seem to be playing any big role...

That and the fact that there is a fundamental difference between EM's cyclical nature (frequency), and gravity's non-cyclical tensor. It's more than the difference between AC and DC, however, as gravity acts by warping spacetime itself.

Some have postulated that EM is a warping of spacetime, too, but merely along two distinctly different properties (electric and magnetic, vs gravitational). If so, the quantization of light is evidence for quantum gravity, and lends credence to both the weak and strong forces as additional warpings of spacetime, thereby incorporating gravity as a the fifth fundamental force, unified at the quantum level by M-theory's 11 dimensions of spacetime. Indeed, Cherkis, Dotsenko, and Samann related earlier this year superspace actions for multiple M2-branes to the original Bagger-Lambert-Gustavsson action.

[cfgauss]

That and the fact that there is a fundamental difference between EM's cyclical nature (frequency), and gravity's non-cyclical tensor. It's more than the difference between AC and DC, however, as gravity acts by warping spacetime itself.

No, gravity can have a characteristic frequency, too (specifically, for a source in periodic motion, or for linearized gravity). The issue is maxwell's equations, which are linear vs. einstein's equations, which are not.

Some have postulated that EM is a warping of spacetime, too, but merely along two distinctly different properties (electric and magnetic, vs gravitational). If so, the quantization of light is evidence for quantum gravity, and lends credence to both the weak and strong forces as additional warpings of spacetime, thereby incorporating gravity as a the fifth fundamental force, unified at the quantum level by M-theory's 11 dimensions of spacetime. Indeed, Cherkis, Dotsenko, and Samann related earlier this year superspace actions for multiple M2-branes to the original Bagger-Lambert-Gustavsson action.

No, this is totally wrong. Theories which treat E&M like gravity (e.g. Kaluza-Klein) write down Einstein's field equations in 5 dimensions, and break them up into something that looks like (circle) x (spacetime), and the circle part gives classical E&M and the spacetime part gives normal GR. No quantum gravity.

String theory is different, and has a different mechanism for generating particles and forces, and generates them all together.

Either way, quantized E&M by itself is absolutely not evidence for quantized gravity.

And please don't cite random string theory papers like they prove your point. The paper you cited has nothing to do with gravity!

Edit:
In fact, the whole point of modern descriptions of yang-mills theories is to describe all theories in the same geometric way; fields, invariances, and actions.

[mugaliens]

No, gravity can have a characteristic frequency...

It's an undulation around a positive bias. There is no negative gravity.

No, this is totally wrong.

Well, then, you better get busy and re-edit Wikipedia so that it's not totally wrong!

Theories which treat E&M like gravity...

I'm not sure why you mention this, as I did not, and do not treat EM like gravity. Similarities with respect to their possible interaction with spacetime, yes (both propogate at the speed of light, for example). Other than that, they're seriously different.

Either way, quantized E&M by itself is absolutely not evidence for quantized gravity.

I've learned that when people make absolute statements, those statements are usually somewhat suspect.

By the way, I usually dislike it (greatly) when others misconstrue my words, so I ask that you go back and read my post. I did not state, "E&M by itself..."

You added the underlined portion. Please refrain from doing so in the future, as it leads to misunderstandings, and generally speaking, putting words in the mouths of others is rude.

And please don't cite random string theory papers...

That's just downride rude, your talking down to me like that. Congratulations - you just lost my respect.

Have a nice day.

[cfgauss]

It's an undulation around a positive bias. There is no negative gravity.

Which has nothing to do with what frequency means... Waves oscillate around their equilibrium, which has nothing to do with anything being negative! Gravitational waves are waves which oscillate around the minkowski metric.

Well, then, you better get busy and re-edit Wikipedia so that it's not totally wrong!

I'm not sure why you mention this, as I did not, and do not treat EM like gravity. Similarities with respect to their possible interaction with spacetime, yes (both propogate at the speed of light, for example). Other than that, they're seriously different.

Err, what? I was responding to "Some have postulated that EM is a warping of spacetime." How is this not "treating E&M like gravity." That's the definition of gravity.

I've learned that when people make absolute statements, those statements are usually somewhat suspect.

A => B
B
therefore A

is a logical fallacy

"If (it's raining and I'm outside), then I'm wet; I'm wet, therefore (it's raining and I'm outside)."

By the way, I usually dislike it (greatly) when others misconstrue my words, so I ask that you go back and read my post. I did not state, "E&M by itself..."

You added the underlined portion. Please refrain from doing so in the future, as it leads to misunderstandings, and generally speaking, putting words in the mouths of others is rude.

What? Again, you said, "Some have postulated that EM is a warping of spacetime." which is what I was responding to, again.

That's just downride rude, your talking down to me like that. Congratulations - you just lost my respect.
Have a nice day.

You do realize that I'm a physicist, and I actually study string theory, right? You can't slip some random paper into your post and pretend it has anything to do with what you said.

Let's recall the abstract of that paper:

We classify canonical metric 3-algebra structures on matrix algebras and find novel three-dimensional conformally invariant actions in N=4 projective superspace based on them. These can be viewed as Chern-Simons theories with special matter content and couplings. We explore the relations of these actions with the N=2 actions based on generalized 3-Lie algebras found earlier and relate them to the original Bagger-Lambert-Gustavsson action.

Saying this has anything to do with your statement "the quantization of light is evidence for quantum gravity, and lends credence to both the weak and strong forces as additional warpings of spacetime, thereby incorporating gravity as a the fifth fundamental force" is a total non sequitur.

[Cougar]

Moving right along....

In fact, the whole point of modern descriptions of yang-mills theories is to describe all theories in the same geometric way; fields, invariances, and actions.

I know you think of Peter Woit as largely inconsequential, but I must say, his book went into more of the "math" than any of the hundred or so other fairly current books attempting to describe what's going on in quantum physics or cosmology or astrophysics that I've read over the past several years. Why had I never heard of representation theory?? I thought Woit, being mainly a mathematician, explained a lot of the abstract algebra and symmetry utilizations pretty well. Most everyone else just made passing reference to this whole area, if at all...

Most everyone else, which includes Gell-Mann, Weinberg, Lederman, Guth, et al... all complain about the publishers not letting them include "math." At least Woit wouldn't take that from his initial publisher and went somewhere else.... Point is, somebody ought to clue the publishers in that the audience for these publications are gaining, you know, a little sophistication.

[cfgauss]

I know you think of Peter Woit as largely inconsequential, but I must say, his book went into more of the "math" than any of the hundred or so other fairly current books attempting to describe what's going on in quantum physics or cosmology or astrophysics that I've read over the past several years. Why had I never heard of representation theory?? I thought Woit, being mainly a mathematician, explained a lot of the abstract algebra and symmetry utilizations pretty well. Most everyone else just made passing reference to this whole area, if at all...

Yeah, most of the basic "baby stuff" he talks about is pretty reasonable. Although there is the occasional weird confusion or misconception or something. It's not until he talks about things that haven't been known for 50 years that he goes off the deep end .

In fact the other LQG people are similar. I've read reviews of some "talks" the LQG people have given, and they typically spend a great deal of time going over "baby stuff" which is mostly accurate, and then spending a hilarious 70 or so percent of the talk stumbling through intermediate to advanced grad stuff before jumping off the deep end for the remainder of the talk.

In terms of the actual math involved in real physics, it is absolutely fantastic. The modern geometric structure of these kinds of theories is very unbelievably beautiful. Much more so IMO than the typical traditional way physicists like to write things out, where things tend to just look odd, random, and mysterious.

Most everyone else, which includes Gell-Mann, Weinberg, Lederman, Guth, et al... all complain about the publishers not letting them include "math."

Yeah, that's definitely a problem. Although Penrose's "road to reality" includes a great deal of math, and I've heard it's pretty good, aside from the last chapter or two which contain a few mistakes.

It's even a problem with textbooks containing insufficient levels of math. It's a very unfortunate problem, and is in fact related to what people're talking about over in the "what good is math" thread .

[Cougar]

It's not until he talks about things that haven't been known for 50 years that he goes off the deep end .

The entire first half of the book, he didn't even mention string theory. A little odd for a book whose subtitle starts off "The failure of string theory..." The long historical development was pretty good. But then he launched his attack, followed by a truly Arpian criticism of the American university system and "no funding for alternative thinkers."

Although Penrose's "road to reality" includes a great deal of math, and I've heard it's pretty good...

Yeah, thanks for the recommendation.

[WayneFrancis]

...
Yeah, that's definitely a problem. Although Penrose's "road to reality" includes a great deal of math, and I've heard it's pretty good, aside from the last chapter or two which contain a few mistakes.

It's even a problem with textbooks containing insufficient levels of math. It's a very unfortunate problem, and is in fact related to what people're talking about over in the "what good is math" thread .

I've got that book. Very good. If you want to know all the maths then those chapters are there for you and explain things very well. It does read a lot more dry then other popular science books at first because of it but then this goes into the whole can you understand something without the maths. If you don't know any of the maths then the book can be a bit frustrating but you can skip it if you really want to .... you just won't be able to make some of the connections you would have if you did learn the maths.

[mugaliens]

Which has nothing to do with what frequency means... Waves oscillate around their equilibrium, which has nothing to do with anything being negative! Gravitational waves are waves which oscillate around the minkowski metric.

For binary stars, I can see this. For gravitational adjustment following mass conversation during supernova, I cannot, as it's a step wave, not an oscillatory wave.

I was responding to "Some have postulated that EM is a warping of spacetime." How is this not "treating E&M like gravity." That's the definition of gravity.

I wasn't intending they warp spacetime in the same manner as does gravity. With 11 dimensions, surely some (5?) are observable and distinct.

You do realize that I'm a physicist, and I actually study string theory, right?

Good for you - you undoubtedly know a great deal more about string theory than I do!

Saying this has anything to do with your statement "the quantization of light is evidence for quantum gravity, and lends credence to both the weak and strong forces as additional warpings of spacetime, thereby incorporating gravity as a the fifth fundamental force" is a total non sequitur.

Instead of summarily dismissing with a non-explanatory comment such as "is a total non-sequitor" (which is itself logically fallacious) please take the time to elaborate, answering questions such as "why" and "how."

This is Q&A - I'm hear to learn! Answers such as "this is rubbish!" do not support the learning process.

Thanks.

[cfgauss]

For binary stars, I can see this. For gravitational adjustment following mass conversation during supernova, I cannot, as it's a step wave, not an oscillatory wave.

No, it's not.

Instead of summarily dismissing with a non-explanatory comment such as "is a total non-sequitor" (which is itself logically fallacious) please take the time to elaborate, answering questions such as "why" and "how."

No, it's not, you said "A => B" when A and B had nothing to do with each other. That's the definition of a non sequitur.

And I can't "elaborate" on nonsense statements like that. I can only say they're wrong.

This is Q&A - I'm hear to learn! Answers such as "this is rubbish!" do not support the learning process.

I don't have the time to give everyone here their own personal degree in physics.

[trinitree88]

[QUOTE=mugaliens;1514750]For binary stars, I can see this. For gravitational adjustment following mass conversation during supernova, I cannot, as it's a step wave, not an oscillatory wave.


Mugs. nitpik...I think you mean mass conversion during "supe"...in an otherwise interesting thread......pete

[captain swoop]

Cfgauss. Your replies are not helpful. This is the Q & A section where people ask questions andexpect people responding to give answers. IF you have no answers to give then don't respond.

[mmaayeh]

If I told you that, you would be subject to extraordinary rendition.

Yeah, I know it was a very outlandish question -- I concede that but, I thought to explore the domain of the problem. You know what if a universe can go into destructive harmonic if you have space-time doing the gravity wave.