Gravity Hysteresis: Effects & Implications

[wolram]

can anyone tell me if gravity suffers hysteresis effects? as gravity
travels at C i imagine this effect would only be relevant to ,a high
speed massive body with an highly eccentric orbit, i also wondered
if this effect had implications at the quantum level.

 

[Njorl]

Do you know of good sites with arguments about the speed of gravity. I have heard some fairly simple yet cogent arguments that it is not observably finite.

I bring this up because I have heard that binary pulsar systems exhibit no trace of effects of retarded gravitaional potentials. If anything observable were to exhibit the behavior you ask about, it would be binary pulsars.

Njorl

 

[wolram]

NJORI.

Do you know of good sites with arguments about the speed of gravity. I have heard some fairly simple yet cogent arguments that it is not observably finite.
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the speed of G has been accepted by main stream science as = to C
but i have read papers that disagree, i will find anti C articles and
post soon.

 

[Stingray]

can anyone tell me if gravity suffers hysteresis effects? as gravity
travels at C i imagine this effect would only be relevant to ,a high
speed massive body with an highly eccentric orbit, i also wondered
if this effect had implications at the quantum level.

What exactly do you mean by hysteresis? There is a path dependence that exists - essentially gravitational waves being emitted and then scattering back to influence the particle in the future. I'm not sure that I'd call that hysteresis though.

You're right that it has more relevance for very extreme motions though.

What do you mean by quantum implications?

Njorl, binary pulsars give the most evidence that the speed of gravity is c. I don't know what you're referring to.

 

[wolram]

STINGRAY.
when i use the term "hysteresis", i use it in its simplest form as such,
"literally, to be late. It describes systems that do not directly follow the forces applied to them", and from this i inferred that a massive body
traveling at high speed will have a delayed reaction to gravity, if gravity travels at C.
at the other end of the mass scale particles are traveling at relativistic
speeds and i thought that reaction to gravity would have some time
dependence.

 

[Stingray]

I'm still not sure exactly how to answer your question. Test particles move according to what the fields (and their derivatives) are at whatever point they are occupying. In this sense everything is completely local, and there is no hysteresis.

The gravitational force is always zero in terms of strict definitions (for test particles), but if you adopt a more intuitive viewpoint, then the forces are velocity dependent. This is closely analogous to the presence of a vxB term in the electromagnetic force. Do you consider vacuum electromagnetism to show hysteresis?

 

[wolram]

STINGRAY.
The gravitational force is always zero in terms of strict definitions (for test particles), but if you adopt a more intuitive viewpoint, then the forces are velocity dependent. This is closely analogous to the presence of a vxB term in the electromagnetic force. Do you consider vacuum electromagnetism to show hysteresis?
--------------------------------------------------------------------------
the dynamics of vacuum magnetism are beyond my learning, but
intuitively i would say yes, as perpetual motion is an impossibility
all systems must have losses of some kind, so a solid body in an
magnetic Field would need time for internal changes to occur
before reaction could happen.

 

[wolram]

NJORI,

www.arxiv.org/abs/astro-ph/0301145 )
(www.arxiv.org/abs/astro-ph/0206266 )

2 papers that discuss speed of gravity results from recent observations.

 

[Njorl]

What exactly do you mean by hysteresis? There is a path dependence that exists - essentially gravitational waves being emitted and then scattering back to influence the particle in the future. I'm not sure that I'd call that hysteresis though.

You're right that it has more relevance for very extreme motions though.

What do you mean by quantum implications?

Njorl, binary pulsars give the most evidence that the speed of gravity is c. I don't know what you're referring to.

From what I've read, the decaying orbits of binary pulsars strongly support the predictions of GR insofar as the radiation of gravitaion is concerned but that the arguments that said radiation travels at c are not necessarily supported by these decaying orbits.

I could easily be wrong. Let me look for it for a while, unless you have a reference at your fingertips.

Njorl

 

[TeV]

From what I've read, the decaying orbits of binary pulsars strongly support the predictions of GR insofar as the radiation of gravitaion is concerned but that the arguments that said radiation travels at c are not necessarily supported by these decaying orbits.

I could easily be wrong. Let me look for it for a while, unless you have a reference at your fingertips.

Njorl

Associate and myself constructed causal model which shows the following:
1)If the velocity of propagation of gravity (Tg wave spacetime disturbance) does not match TEM wave velocity (light) than must be higher than c (not smaller than c under no circumstance)
2)If Tg Wave propagate superluminal it is "faster"* higher its frequency.

Result 2 induces unexceptable consequences (like violating Gauge invariance principle and such) so we concluded "speed of gravity" should equal c.

The paper is currently in peer reviewed process.If it passes ,will be published by the end of this year.
____
* With respect to distant Minkowski space point.

 

[wolram]

http://www.mathpages.com/rr/s6-08/6-08.htm

An even more impressive example of the phase-lag cancellation effects of numerator dynamics involves the "force of gravity" on a massive test particle orbiting a much more massive source of gravity, such as the Earth orbiting the Sun. In the case of Einstein's gravitational field equations the "numerator dynamics" cancel out not only the first-order phase effects (like the uniform velocity effect in electromagnetism) but also the second-order phase effects, so that the "force of gravity" on an orbiting points directly at the gravitating source at the present instant, even though the source (e.g., the Sun) is actually undergoing non-uniform motion. In the two-body problem, both objects actually orbit around the common center of mass, so the Sun (for example) actually proceeds in a circle, but the "force of gravity" exerted on the Earth effectively anticipates this motion.
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if i am reading this correctly the answer is yes but not realy.

 

[Nereid]

http://www.mathpages.com/rr/s6-08/6-08.htm

An even more impressive example of the phase-lag cancellation effects of numerator dynamics involves the "force of gravity" on a massive test particle orbiting a much more massive source of gravity, such as the Earth orbiting the Sun. In the case of Einstein's gravitational field equations the "numerator dynamics" cancel out not only the first-order phase effects (like the uniform velocity effect in electromagnetism) but also the second-order phase effects, so that the "force of gravity" on an orbiting points directly at the gravitating source at the present instant, even though the source (e.g., the Sun) is actually undergoing non-uniform motion. In the two-body problem, both objects actually orbit around the common center of mass, so the Sun (for example) actually proceeds in a circle, but the "force of gravity" exerted on the Earth effectively anticipates this motion.
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if i am reading this correctly the answer is yes but not realy.

The text wolfram is quoting from explores the mathematics of GR, in this section 'sources in motion'. It does not question - or seek to question - that 'the speed of gravity' is c; it examines what sorts of orbits and orbital dynamics may be expected under GR, particularly where one massive body is in orbit around an even more massive body.

Whats' really cool is the last two sentences: "The important point to realize is that the fact that the Earth's gravitational acceleration always points directly at the Sun's present position does not imply that the "force of gravity" is transmitted instantaneously. It merely implies that there are velocity and acceleration terms in the transfer function (i.e., numerator dynamics) that effectively cancel out the phase lag in a simple periodic pattern of motion.[/color]"

 

[wolram]

NEREID,
you are good for the brain, may i prescribe 4 doses a day?

 

[Njorl]

The text wolfram is quoting from explores the mathematics of GR, in this section 'sources in motion'. It does not question - or seek to question - that 'the speed of gravity' is c; it examines what sorts of orbits and orbital dynamics may be expected under GR, particularly where one massive body is in orbit around an even more massive body.

Whats' really cool is the last two sentences: "The important point to realize is that the fact that the Earth's gravitational acceleration always points directly at the Sun's present position does not imply that the "force of gravity" is transmitted instantaneously. It merely implies that there are velocity and acceleration terms in the transfer function (i.e., numerator dynamics) that effectively cancel out the phase lag in a simple periodic pattern of motion.[/color]"

That was one of the things I had come across that raised questions about speed of g=c, that Earth's gravitational acceleration vector was not parallel to the light from the sun.

Now, IIRC from my E&M course so long ago, you don't need to use retarded potentials for moving charges, unless they are accelerating. If gravity works analagously to electrodynamics, you would need to use retarded gravitational potentials because the Earth is accelerating. Right?

1. Am I just remembering wrongly?
2. Is the acceleration insignificant?
3. Is an object in a closed orbit considered to be not accelerating due to the warping of space?

Thanks,
Njorl

BTW, I'm enjoying this. I've been doing the same old stuff for years now (solid state), and I like feeling like a student again for a while. Plus, there are no exams!

 

[Stingray]

From what I've read, the decaying orbits of binary pulsars strongly support the predictions of GR insofar as the radiation of gravitaion is concerned but that the arguments that said radiation travels at c are not necessarily supported by these decaying orbits.

I should of clarified, but I meant that the experiments are in good agreement with GR, which in turn implies speed of gravity = c (To be completely correct, it travels at speeds <=c -- there are "components" which will not travel at light speed due to a scattering effect off the curved spacetime. This is sort of analogous to the addition of a mass to a scalar field theory if you're familiar with that.).

Anyway, theories with speeds of gravity that aren't exactly c are not ruled out AFAIK, but an infinite propagation speed is I think conclusively inconsistent with gravitational radiation effects.

Njorl, that would be quite a miraculous cancellation if EM did not require retarded integrals for uniformly moving charges. It might be true, but I don't remember it.

All of these things become very difficult to state even in linearized GR for fast-moving objects. Forget about it in the full theory. A particle with infinitesimal mass in an orbit is considered to be unaccelerated, but this is not the real two body problem. Its a hard (mostly unsolved) problem.

 

[TeV]

(To be completely correct, it travels at speeds <=c -- there are "components" which will not travel at light speed due to a scattering effect off the curved spacetime. This is sort of analogous to the addition of a mass to a scalar field theory if you're familiar with that.).

.

That was actually the point what we examine:Does the effect of changing spacetime curvatory always decelerate speed of light in comparation with speed of light in inital gravity field of the same source?
We modeled the symmetrical field configuration situation of spherical stationary object lineary INCREASING its mass*.What would happen with velocity of sequence of gravity potential pulse fronts compared with velocity c in start up configuration ?If it doesn't equal c,we show it can't be slower than c in this modell,just higher.It is contrary to what can be expected.Note that it is important to specify condition of c for the purpose of comparation.
Consider this result just preliminary,becouse it's not completely known in present theory (althought some modells exists ) how to realize condition (*) without local source of energy that disturb in reaction gravity potential parameters.

 

[wolram]

by TEV.
If it doesn't equal c,we show it can't be slower than c in this modell,just higher.
--------------------------------------------------------------------------
am i reading this incorrectly or are you saying that speed of G>C ?

 

[Stingray]

TeV, it can be shown that the gravitational Green function has support inside (and on) the light cone when linearizing off of a curved background. To me, this is the proper definition of what it should mean to say light travels at <=c.

For example, if you consider a small particle in orbit around the other one, the radiation reaction effects come from the integrated effect of the "slower than light" portion of the Green function.

 

[TeV]

by TEV.
If it doesn't equal c,we show it can't be slower than c in this modell,just higher.
--------------------------------------------------------------------------
am i reading this incorrectly or are you saying that speed of G>C ?

No.The model is quite artificial.Despite causality preserved it requires local source of energy which interacts with spherical mass and rises its gravitational potential while at the same time doesn't have gravitational energy by itself.For instance,we suspect that this source might be vacuum energy.How that can happen is not disscused or wether is possible for that matter.The consequences would be odd .Specificaly in this geometry,without classical gravity waves .The system gets the energy.Both velocities of light and gravity may be higher than c in vacuum (on other hand this isn't tachyon physics).
.With rotation of the object we get another strange consequence like possibility of antigravity effects.This isn't rigorously forbidden in the equations of GR,but is strange.
Not mentioning other problems,we concluded that real nature of gravity propagation matches c.

 

[wolram]

TEV.
this sounds intriguing, obviously i am far below your level, and maybe
wont understand," i would like to try," I'm sure members on this forum
would be interested in your research.

 

[steve stillman]

Further gravity questions

Ive read nearly every super string and cosmology book. I've formed some basic questions that gnaw at me while reading. I've tried other physicists
and they ignore my mail. Its simple basic stuff that is not given a chapter
in any book. Laymen like me need grounding before appreaciating all the
perterbance journal articles on black hole gravity.

Sorry if this subject has its own heading in the archive. I searched and found nothing.

1. How does gravity get thru an event horizon in a black hole?

2.If gravity begins to pass out of the event horizon how long does it take to get 1 mile away from the horizon? 1000 years?

3. If gravity travels at the speed of light, why don't authors carfully
state that gravity cannot escape a black hole.

4. If a black hole core vibrates, how can gravity escape?

5. How can gravity waves carry away energy. Was it some postulate made
that has not been tested? Why can't gravity just be a state of 4
dimensional space and instantaniously affect anything in its influence?
That gravity waves carry energy is not testable, right? There must be a textbook somewhere with several carfully worded examples explaining how gravity pulses would influence a body, what to expect and what not to expect.

6. If gravity carries energy, how does one calculate the phase delay
from the time a wave peaks to the time a body is influenced fully.

7. If there is a phase delay, will a body feel a tug. I thinkTugs won't be felt on floating objects since gravity is like free fall, but will be felt by seated individuals compressing a springy seat.

8. Gravitons are assumed gravity particles. What justification is there
for this particle. What other particles does it create, destroy or
interact with? What purpose is a graviton in any real mind experiment.
Ive read today that they are not needed to explain observables so far.

9. Can a gravity wave push the local gravity down so much that it can go negative during part of its wave?

10. Why do people think they can detect gravity waves if the arms of the
interferometer shrink the same amount as the time dilation slows the
beam on that arm nothing will be noticed? This one really gets me.

Thanks for your time. Hope Lee Smolin or Kip Thorne is reading this and can help.

Steve Stillman

 

[wolram]

http://www.nu.to.infn.it/Gravitational_Waves/#Theory

STEVE, i can't answer all your questions, but the site i have posted
is quite comprehensive, if you don't find what you need, or want
clarification, start a new thread, that will attract more attention
to your queries.
regards.
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http://en.wikipedia.org/wiki/Graviton

this is from WIKIPEDIA online dictionary.

 

[TeV]

TEV.
I'm sure members on this forum would be interested in your research.

I'm co-authorizing and the policy is not to reveal more details without permission of my associate in first place.Also,we don't know yet if the paper will be published in the current form or not.If everything goes fine,3 months after the publishing I'll put the paper on the internet.I'll let PF know when that happens.I hope about October.
regards,
TeV

 

[wolram]

I'm co-authorizing and the policy is not to reveal more details without permission of my associate in first place.Also,we don't know yet if the paper will be published in the current form or not.If everything goes fine,3 months after the publishing I'll put the paper on the internet.I'll let PF know when that happens.I hope about October.
regards,
TeV
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good luck, and i hope all goes well, I am sure it will be an interesting read.

 

[Stingray]

Steve,
Here is a FAQ which answers several of your questions:
http://math.ucr.edu/home/baez/physics/index.html

I don't want to wander through all of that, so please repost all the questions you still have, and I'll try to answer them directly.

 

[steve stillman]

Thanks for math.ucr.edu link

Im beginning to understand my gravity questions. The link http://math.ucr.edu/home/baez/physics/index.html
says that gravity outside a black hole is the ancient field at the moment of black hole creation and is frozen just as the electric charge is frozen. The photons are not a field so quickly dissipate.

Still need to answer question 10.

I also see that the Speed Of Gravity question was brought up in this thread by several in the last year but Stingray had the best link I've seen.

Steve Stillman

 

[ranyart]

1. How does gravity get thru an event horizon in a black hole?

2.If gravity begins to pass out of the event horizon how long does it take to get 1 mile away from the horizon? 1000 years?

3. If gravity travels at the speed of light, why don't authors carfully
state that gravity cannot escape a black hole.

4. If a black hole core vibrates, how can gravity escape?

5. How can gravity waves carry away energy. Was it some postulate made
that has not been tested? Why can't gravity just be a state of 4
dimensional space and instantaniously affect anything in its influence?
That gravity waves carry energy is not testable, right? There must be a textbook somewhere with several carfully worded examples explaining how gravity pulses would influence a body, what to expect and what not to expect.

6. If gravity carries energy, how does one calculate the phase delay
from the time a wave peaks to the time a body is influenced fully.

7. If there is a phase delay, will a body feel a tug. I thinkTugs won't be felt on floating objects since gravity is like free fall, but will be felt by seated individuals compressing a springy seat.

8. Gravitons are assumed gravity particles. What justification is there
for this particle. What other particles does it create, destroy or
interact with? What purpose is a graviton in any real mind experiment.
Ive read today that they are not needed to explain observables so far.

9. Can a gravity wave push the local gravity down so much that it can go negative during part of its wave?

10. Why do people think they can detect gravity waves if the arms of the
interferometer shrink the same amount as the time dilation slows the
beam on that arm nothing will be noticed? This one really gets me.

Thanks for your time. Hope Lee Smolin or Kip Thorne is reading this and can help.

Steve Stillman

Thanks for your time. Hope Lee Smolin or Kip Thorne is reading this and can help.

 

[wolram]

http://arxiv.org/PS_cache/astro-ph/pdf/0311/0311462.pdf

i thought that this article answer your question No 10.

 

[Stingray]

Still need to answer question 10.

10. Why do people think they can detect gravity waves if the arms of the
interferometer shrink the same amount as the time dilation slows the
beam on that arm nothing will be noticed? This one really gets me.

It is possible to look at things in a way such that there is no time dilation (by picking a coordinate system or gauge), and the experiments are designed to look at data from this viewpoint. That may seem like cheating, but space and time are always very subtle notions in GR (much more so than in SR), and it is mathematically consistent to do this. You end up getting more or less get what you would expect from the simple distance stretching pictures given in popular books.

And none of what ranyart said made any sense...

 

[ranyart]

It is possible to look at things in a way such that there is no time dilation (by picking a coordinate system or gauge), and the experiments are designed to look at data from this viewpoint. That may seem like cheating, but space and time are always very subtle notions in GR (much more so than in SR), and it is mathematically consistent to do this. You end up getting more or less get what you would expect from the simple distance stretching pictures given in popular books.

And none of what ranyart said made any sense...

I have not a single qualification, I have no 'Honorary' affiliations, I have been called a renagade,.. fool, Avant-Garde thinker, I share only a quest of Understanding of the Universe.




No Fear is the Key.