Yes. A gamma ray photon, emitted from a decaying nucleus, is normally thought of as being some exceedingly tiny entity in all 3 dimensions. Yet by SR transformation, ELF output of a huge antenna becomes gamma rays in another frame. When I first realized it's significance, it more or less instantly killed-off my previous notion a photon could be modeled as a soliton-type pulse, and tilted thinking in favor of a point-like particle model. But then it occurred that maybe it's a case of 'there are photons, and then again there are photons'. Meaning it may be meaningful to characterize an effective 3D extent in the frame of photon emission, and then simply allow SR to transform that for any other frame. There must be some sense of effective cross-section - after all shine a laser pointer beam through a hole (larger than the evident beam spot size) in a reflecting or absorbing plate, and there is negligible attenuation or diffraction. Anyway nowadays I don't know what exactly makes sense. But not ready to concede to those theorists who contend no consistent physical model is possible.
QM + GR = black holes cannot exist
- Thread starter RJBeery
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Why ask a question I already answered umpteen times?
AS I POINTED OUT TO YOU!! Or are you really expecting to get away with trying to turn the tables on what #339 exposed - your own lack of real understanding of GR? Here it is again - from your #337:
WRONG!! And, conceited coward that you are, you have continually ducked and weaved and failed to answer BillyT's repeated clear questions on that. A specific scenario presented to you in #356 was met with typical word salad BS in #374 that gave no answer. In keeping with your absolute, unqualified above reproduced statement in #337, you should have given NO as a consistent response - but failed to give any answer. Actually, the standard GR position is an unequivocal YES -as given by eqn's (30), (35) in that 1931 article I referenced. How ironic that you should try and paint me as ignorant of what GR says when the truth is, though I am an acknowledged critic of GR, I know it's consequences better than you as supposed defender-of-the-faith.
You went to ground for at least two days following my own intentionally low-key 'anonymous' rebuttal of #339. It's because you knew darn well sooner or later you would be confronted with your own above unqualified, absolute statement that is dead wrong.
An absurd statement. Effective gravitational mass of light is *synonymous* with it's capacity to effect local spacetime curvature!
More typical brucep meaningless word salad.
Given your own demonstrated lack of real grasp of GR, you're in no position to judge what I really think.
That's because you know that if you did, I would have you in knots - again. Provoke me further, and I will hugely embarrass you by dredging up past postings where you have been repeatedly exposed as a pretender and a cut-and-run coward. Your choice.
I bit my tongue and held back with you in #356 in answering your *loaded* query of #350 - tried to be especially civil and refrained from pointing out your obvious earlier error. But to no avail. As you well know we have a past history of not getting on, to put it mildly. And ALWAYS it has been you initiating an aggressive, nasty attitude. And not just against me. Watched with amusement as you managed to rile the normally unflappable Fednis48 here:
http://www.sciforums.com/threads/galileo-was-technically-wrong.142700/page-12#post-3231047
His civil response was quite a contrast in character. Tach was permanently banned for his continued aggression, and somehow you have avoided that fate though being at least as nasty, and considerably less capable all round than him. Gushing sycophantic praise for those higher up the chain no doubt helps there.
I make no pretense of being a GR expert and am happy to admit being an amateur scientist. But do claim to have a certain level of insight and ability to critically think outside the box - differently and independently of prevailing group-think. And the balls to say so - and to admit when wrong. Whereas you assiduously cultivate via word salad an image of being actually proficient in GR; fancying yourself as some kind of local 'Einstein's bulldog'. It fools some here who are wrongly in awe of you. Not me. We did have a resident proficient in GR - Markus Hanke. But he left in disgust. Too bad.
Photons definitely have an E=hf wave nature. I think you should think in terms of a seismic wave myself. Have a look at weak measurement work by Aephraim Steinberg et al:
http://www.physics.utoronto.ca/~aephraim/PWMar13steinberg-final.pdf
General Relativity is useful for modeling gravity via the construct called space-time. However, GR is not complete, but rather leaves out key attributes connected to classical gravity. Gravity, because it is generated by mass, also generates pressure. GR does not deal with matter under pressure caused by gravity.
With Special Relativity, space-time is impacted by velocity, but the matter in motion does not undergo physical compression (pressure) implicit of all objects turning into black hole density, as we approach the speed of light; maximum space-time contraction in GR.
If you look at the fusion core of a star, this creates the highest energy photons. These photons have the smallest wavelength, which is consistent with this being the place of highest distance contraction due to GR. However, the frequency of the photons are the fastest, while time in space-time is getting slower; time moves in opposite directions relative to pressure and space-time. GR has something missing.
Say we have fusion core energy output, increasing frequency with pressure, while GR is causing space-time to contract in the same area of the contracting core. Since GR and pressure cause time to go in opposite directions, but distance in the same direction, what does the composite imbalance in time and distance, create?
In other words, the composite of time and the composite of space is not what you expect of space-time, since these don't balance out. The composite time is more analogous to the surface or out in space, while the composite distance is more implicit of the core; gravity waves, magnetic field?
With Special Relativity, space-time is impacted by velocity, but the matter in motion does not undergo physical compression (pressure) implicit of all objects turning into black hole density, as we approach the speed of light; maximum space-time contraction in GR.
If you look at the fusion core of a star, this creates the highest energy photons. These photons have the smallest wavelength, which is consistent with this being the place of highest distance contraction due to GR. However, the frequency of the photons are the fastest, while time in space-time is getting slower; time moves in opposite directions relative to pressure and space-time. GR has something missing.
Say we have fusion core energy output, increasing frequency with pressure, while GR is causing space-time to contract in the same area of the contracting core. Since GR and pressure cause time to go in opposite directions, but distance in the same direction, what does the composite imbalance in time and distance, create?
In other words, the composite of time and the composite of space is not what you expect of space-time, since these don't balance out. The composite time is more analogous to the surface or out in space, while the composite distance is more implicit of the core; gravity waves, magnetic field?
Farsight, you just recommend ditching QM in favor of simple wave mechanics and then you link to an article that is essentially off-topic where wave mechanics is rejected in favor of QM.
Farsight, please take the time to read your citations and try to understand them. Physics is not impossible to learn.
Farsight, please take the time to read your citations and try to understand them. Physics is not impossible to learn.
Why not? It seems that one could naturally include that information in the stress-energy tensor.
Ah, you just mean that GR cannot deal with the maximal pressure we get in a black hole. I'm not sure that's correct; GR can model black holes just fine, the problem is whether or not we trust these models.
I think what you are missing is that the creation of the photons is something due to the nuclear reactions taking place in their own rest frame. GR has nothing to say about that until the photons head out of the core. Then one expects some redshift. How much redshift should one expect?
Why don't you give us a model of a star and work this out? It seems that astrophysicists working on stars must do this problem quite often.
I did no such thing.
I've read them and I do understand them. That's why I was able to correct brucep on his false assertion that the force of gravity is down to local spacetime curvature. You didn't.
Please give some hint, at least, as to where I brought in ANYTHING to due with QM into the question. For example let X be either a tiny dust particle OR a photon.
I asked: If two Xs were traveling initially on parallel paths only a micron apart, do they gravitationally (or warp space ) to attract each other?
If X = tiny dust particle, or even just a proton, then clearly the correct answer is: Yes.
If X = photon then answer to whether or not they attract each other is: "Yes" if photons do slightly warp space (make a tiny gravitational field that moves with them); but if they don't, then the answer is "No."
Brucep repeatedly refuses to give a clear Yes/No answer. He wants to explain things, speak of geodesics, or claim the answer is mixing GR with QM.
Just because in one case the two Xs are identical photons does not imply it is a QM question. This question could be asked when Planck quantized light - before the even was any QM theory!
Brucep's post 374 begins with: "The photons energy and momentum contribute to the local spacetime curvature. The local spacetime curvature is the gravity...."
My reply in post 375 begins with: "{that} sounds like: Yes, two identical photons traveling parallel to each other at least initially only 1 micron apart for many years do attract each other, ..."
I. E. He forced me to guess his start of post 374 was a long winded "yes" answer, but then in post 376 he comment on my 375 with:
"No I didn't say anything like your first paragraph (of post 375}. You're Mixing up domain of applicability. GR is a classical theory of gravity and doesn't make any predictions for quantum phenomena. ..."
So I still have no clear answer from Brucep to a simple classical question about photons as a source of very weak gravity. Likewise, I have no idea what QM phenomena he eludes to (And I am quite well educated in QM.)*
If you agree with brucep that I am discussing or asking about QM, please tell why and is the question with X = tiny dust particles also a QM question?
* As evidence of that education, from post 375:
Also note my Ph.D. was an experiment investigation of spectral lines from the Argon ion** - how they were shifted and broadened when the ion radiator was part of high density plasma. - Not even in doing that was ANY quantum mechanical analysis required, nor was any required when I measured the length of some Sodium D lines as ~30 cm.
BTW, don't say: "Anything very small is a QM question." (The proton is at least 1000 times smaller than any atom and all photons are at least a few cm long 1,000 times typical atomic radii!) So that silly reply means you need both GR & QM to know if two carbon atoms near each other gravitationally attract each other.
** Hans Griem had just worked out the theory for these effects for neutral radiators. He had guessed they would be larger for an ion radiator*** - I was first to confirm that. One of the lines I accurately measured the wave length of (with Fabry Perot interferometer cascaded with common spectra graph to "order separate") was displaced by more than an Angstrom.
*** Because a passing electron would curve some due to the ion's positive charge and thus be "near by" the ion longer than if it was passing a neutral. I guessed that the effect would be largest if I made a relatively cool, but 100% ionized plasma. So I did that.
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Please read your own posts. You wrote, "Photons definitely have an E=hf wave nature. I think you should think in terms of a seismic wave myself."
Yes, you "corrected" him by producing a citation that said he was correct. Congratulations on failing to read your citations.
Please learn physics before you pontificate about it.
Billy it may not have been your intent as you frame the question above, which might just be pushing the limits of GR, however the following bits from your earlier post, to me suggest, that the initial question passed that limit and extended the question into areas GR has no real answers.
Am I wrong in interpreting all of the above references as involving quantum effects/interactions that are not explained within the context of GR.
It has seemed from the beginning that your question was asking how the gravitational field of fundamental particles and photons interact, which is outside the scope of GR and something that can or will only be answerable within the context of a successful model of QG. Even our best experimental evidence supporting GR predictions of gravity's effects on single atoms requires some understanding and application of QM. As far as I am aware there is no direct experimental evidence involving charged particles, fundamental or just subatomic, and gravity. We live on a planet that has a significant electromagnetic field that distorts any large scale observations and the particle charges theirselves, at any distance that gravity might be functional between two charged particles, would represent a far greater force than we could expect from any gravitational field.
That is how I have been reading your question based on that first post. If that was not your intent... I've just been confused by my own reading of the initial detail.
As far as that first question, Do photons have a very tiny gravitational field?, which evolved into, do two photons interact gravitationally?, setting aside any QM involvement and only from a theoretical GR approach, Bruce has been answering, it repeatedly, his only error was perhaps not beginning each attempted explanation with a NO to that first question.., followed by the explanation, which is admittedly not nearly as clear as a simple NO.
The photon has a non-zero active gravitational mass. Google it. This isn't rest mass, its a measure of energy, as is inertial mass. The photon has a non-zero inertial mass too. Like any concentration of energy, it causes gravity. Take a look at The Foundation of the General Theory of Relativity here. See page 185 where Einstein says "the energy of the gravitational field shall act gravitatively in the same way as any other kind of energy". A photon causes gravity, and as you know, its path is altered by gravity. So two photons will undergo gravitational attraction. However the huge mass of the Sun bends light by only 1.75 arcseconds, and an arcsecond is 1/3,600th of a degree. So the gravitational attraction between two photons isn't going to be measurable.
I agree as first posed there is no measurable attraction between two parallel traveling photons; In part that is why I asked the question about photon's making gravity a second way that in principle has an experimentally measurable answer; however, my question is what does best current theory say, not can effect be measured with current techology.
Here is part of my post 356:
"Imagine a 1mm diameter 1,000 gigawatt laser beam in vacuum with 50% on duty cycle of 1 second period. Now also in this vacuum is a super resolution electron beam of 1 micron diameter orthogonal to the laser beam path* that just misses or "skims the surface" of the laser beam (when the laser is "on"). The detector of the electron beam is a long way from their point of intersection - say that point is in near earth orbit and the electron detector is on the moon. Is there any one hertz gravitational modulation in the detectors electrical out put?
* The direction of the laser beam slowly turns so that the orthogonal electron beam is always (when laser is off) exactly "filling" the detector. I. e. even a one nano degree deflection of the electron beam, caused by laser's photons warping of geodesic path near their almost grazing point (of laser and electron beams) would show up as a 1 hertz component in the detector's signal.
This is a gedanken - a "thought experiment." Please don't concern your self with technical details. Just clearly say: "Yes, in principle there would be a 1 hertz square wave modulation in the detector signal" or: "No; In principle, there would NOT be any 1 hertz square wave modulation in the detector signal."
With tiny extra cost I can get a trillion, giga, terra watt laser, if need be and at some more expense: an equally well columninated, 1 nano meter neutron beam to be orthogonal to it, so leave out any interaction of the electrons with the E-field of the lasers - just photon's gravity (stress-energy tensor?) does or does not "warp" space "change the geodesic" is my question.
A simple Yes or No would be fine.
Added now:
Note that very high density electronic chips are now made with extremely fine UV light etching the substrate of the chip. (Tiny fraction of a micron UV beam diameter) So instead of an orthogonal electron or neutron beam, we could sent that UV beam to the detector on the moon, to look for the 1hz square wave in the detector's out put signal. That would directly test whether or not zillions of laser photons passing just below the subnano-meter UV beam's photons cause a gravitation deflection of the UV beam.
Again: I am asking about what the theory predicts, but this might even be a "do-able" experiment with the huge laser power now used to compress micron sized D/T fuel pellets, at Livermore Labs as I recall.
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To Farsight Thanks for the google link. The first three hits don't directly address my question. The fourth does:
The first hit is concerned, I think, about post decay event where some mass has become photons - seems to say that with in the future light cones the stronger gravity field the pre decay mass had is "reduced" (by the released photons? or "action at a distance" for points not near a photon, but equally close to the decay point or even slightly closer.) - presumably the reduction of gravity is moving away from the decay point at the speed of light. It doesn't address my question. I think he is thinking about a gamma ray emitting isotopic decay.
I note that if photons do not "make gravity" then the total energy in the gravitational field is reduced by nuclear decay - where did it go to conserved energy?
"Into the photon" is not a very satisfying answer as not all nuclear decays make gamma rays, yet all have lower gravity field, post decay.
Two different answers are then given. Both say "yes" photons do make gravity or in more modern terms (warp space time).http://physics.stackexchange.com/questions/22876/does-a-photon-exert-a-gravitational-pull said:
The first hit is concerned, I think, about post decay event where some mass has become photons - seems to say that with in the future light cones the stronger gravity field the pre decay mass had is "reduced" (by the released photons? or "action at a distance" for points not near a photon, but equally close to the decay point or even slightly closer.) - presumably the reduction of gravity is moving away from the decay point at the speed of light. It doesn't address my question. I think he is thinking about a gamma ray emitting isotopic decay.
I note that if photons do not "make gravity" then the total energy in the gravitational field is reduced by nuclear decay - where did it go to conserved energy?
"Into the photon" is not a very satisfying answer as not all nuclear decays make gamma rays, yet all have lower gravity field, post decay.
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Thanks for a very balanced pair of links. I.e. Prof. Jacobson say "No" and Prof. Engle says "Yes."
Raymond Jensen makes an interesting argument for "No" based on SR's "time dilation." Unfortunately his argument seem to me to also imply, again for his stationary observer. I.e. the period that observer "sees" for a wave in a medium moving towards him at velocity v also contracts and if I extend this speed v movement to the speed of light as he does, then the energy of the photon would become infinite too. That tells me it is not valid to make generalization on how something changes as v increase and extend that to v = c.
Read his paper here: http://www.academia.edu/5364664/Sim...gating_Photons_do_not_Gravitationally_Attract
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Wow! Some vitriol and unsupported accusations being thrown about in this thread!
OK, for what it's worth, as a layman [and an old bastard to boot
] The reply/answer that aligns closest to what I have learnt over the years, is the following.......
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
Prof. Jacobson:
They do not attract each other. See the attached article :
http://www.academia.edu/5364664/Sim...gating_Photons_do_not_Gravitationally_Attract
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
I have said from the beginning that photons/light do actually cause gravity, due to its momentum. This very tiny infinitesimal effect is immeasurable.
Gravity also makes more gravity, due to its property of non-linearity.
see.....
""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
http://scienceworld.wolfram.com/physics/EternalBlackHole.html
Eternal Black Hole
A massless black hole which is a stable topological structure held together by the nonlinearity of its gravitational field.
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
From my position as a layman, I see Prof. Jacobson answer as superior to Prof. Engle, simply due to this property of nonlinearity.
OK, for what it's worth, as a layman [and an old bastard to boot
] The reply/answer that aligns closest to what I have learnt over the years, is the following......."""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
Prof. Jacobson:
They do not attract each other. See the attached article :
http://www.academia.edu/5364664/Sim...gating_Photons_do_not_Gravitationally_Attract
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
I have said from the beginning that photons/light do actually cause gravity, due to its momentum. This very tiny infinitesimal effect is immeasurable.
Gravity also makes more gravity, due to its property of non-linearity.
see.....
""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
http://scienceworld.wolfram.com/physics/EternalBlackHole.html
A massless black hole which is a stable topological structure held together by the nonlinearity of its gravitational field.
"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
From my position as a layman, I see Prof. Jacobson answer as superior to Prof. Engle, simply due to this property of nonlinearity.
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From Prof Carlip's reply............
"Then the answer is "no." If the total energy inside a region is
enough to form a black hole, then anything in that region is
necessarily headed toward the central singularity, and not orbiting
around it. Even outside a black hole, there are no stable orbits
of light very near the event horizon.
One way to describe this is to say that inside a black hole,
spacetime is curved enough that the direction "toward the future"
is the same as the direction "toward the singularity." An object
can stay away from the singularity only if it can move toward
the past.
(Of course, we don't know what happens "at" the singularity --
near enough, we need quantum gravity. But for a large black hole,
the event horizon can be quite far from the center, and most
physicists don't think quantum gravity should be relevant. There
are some who disagree -- there are some arguments that quantum
gravity becomes important as soon as you reach the event horizon
-- but that's pretty speculative.)"
Interesting and needs to be applied to RJBeery's thoughts and hypothesis on the matter......
"Then the answer is "no." If the total energy inside a region is
enough to form a black hole, then anything in that region is
necessarily headed toward the central singularity, and not orbiting
around it. Even outside a black hole, there are no stable orbits
of light very near the event horizon.
One way to describe this is to say that inside a black hole,
spacetime is curved enough that the direction "toward the future"
is the same as the direction "toward the singularity." An object
can stay away from the singularity only if it can move toward
the past.
(Of course, we don't know what happens "at" the singularity --
near enough, we need quantum gravity. But for a large black hole,
the event horizon can be quite far from the center, and most
physicists don't think quantum gravity should be relevant. There
are some who disagree -- there are some arguments that quantum
gravity becomes important as soon as you reach the event horizon
-- but that's pretty speculative.)"
Interesting and needs to be applied to RJBeery's thoughts and hypothesis on the matter......
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I find your replies from the professional experts in the industry as quite educationally revealing and Interesting.
Thanks for the effort.
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