QM + GR = black holes cannot exist

[PhysBang]

I didn't say that.

Why would you say something so obviously untrue. We can just go and read the post where you wrote, "The local spacetime curvature relates to the tidal force." Local spacetime curvature is, according to your citation, the cause of gravitational effects, not merely tides.

However the slope or tilt at some location relates to the local force of gravity, whilst the local curvature relates to the tidal force at that location. It's important that brucep gets this right.

And then you repeat the claim that you just said that you did not make.

 

[Farsight]

...Local spacetime curvature is, according to your citation, the cause of gravitational effects, not merely tides.

No it isn't. According to my citation the local "tilt" is associated with the local force of gravity. As I said, the local spacetime curvature is associated with the local tidal force, not gravitational force. It's the second derivative of potential rather than the first derivative of potential, see for example this book.

 

[Layman]

One of the difficulties that conceptually attributing any form of mass, or even in some respects a gravitational energy, to photons.., is what happens to the cosmological constant, more in terms of models of quantum gravity (QG), than GR... It tends to go off scale, when comparred to observations.

One of the biggest problems right now is being able to find a number big enough that will account for the cosmological constant. It has gotten some physicist involved in the many worlds theory trying to make up more possibilities for other kinds of alternate universes, and they still haven't been able to make up enough different kinds of possible universes that could even come close for the number needed to be the cosmological constant. The problem is they used the Planck Scale to describe it locally, and there would have to be more energy in every unit of space than anything in physics could account for. This kind of thinking all started after the discovery of a more accurate cosmological constant that won the Nobel Prize.

So..,

1. solar sails will work,

No experiment has proved that, that from what I know.

1. ...
2. ...
3. ...
4. I don't see SR breaking down at the speed of light and really don't understand what you mean there. SR is a local or weak field theory, that both GR and QM work well with. How it transitions between the two may present some issues, but that does not imply that SR breaks down. At least as I see it. In fact some of what we learn from SR May and probaly will wind up a critical component of any successful model of QG.

I have been doing a little of my own work in SR, and I was able to derive it from the light triangle. When an objects velocity is the speed of light, then each side of the light triangle is the same size. In geometry, this is an impossible property for a triangle to have. Then any calculation just comes out to zero. The only way all three sides of a triangle can be the same size is if it has no height. Then if there is no distance separating the height from the base of the triangle, then they hypotenuse can be the same distance as the base. Then mathematically in geometry, it tries to make the hypotenuse and the base the same line (that it does when there is no height separating the two). Then what you actually end up describing is just a point, since all lines in all directions have to equal zero when each side of a triangle is the same distance. Also, any theory that comes to be undefined or everything goes to zero at a certain point is said to break down. The same reason why GR breaks down in a black hole; everything goes to infinity. In SR, I can show how everything goes to zero at the speed of light. Then light has quantities that can be measured in real units...

 

[PhysBang]

No it isn't. According to my citation the local "tilt" is associated with the local force of gravity.

You really, really need either better reading comprehension skills or some serious therapy to clear your mind of the blindness you seem to have towards evidence that directly refutes your claims.

Remember, this is a citation that you chose but that you directly disagree with.

That source says, "The gravitational deflection of ordinary objects falling in the vicinity of the sun is due to the curvature of the space-time sheets."

That source says, "Gravity is a curvature of spacetime that affects all free fall motions."

So when that source discusses "tilt", a word that does not appear in the source but I suspect you mean to reference the claim that, "The effect of gravitation is to tip the light cones in the direction of the gravitational attraction," that "tilt" is a result of the curvature of spacetime.

Farsight, you only need to begin to read the sources you cite to begin to learn physics. This is all I ask.

 

[PhysBang]

One of the biggest problems right now is being able to find a number big enough that will account for the cosmological constant.

Hunh?

A very rough estimate of the vacuum energy (so rough that I don't believe it, but it gets bandied about a lot) makes that energy many, many times that of the very weak energy associated with the cosmological constant. So usually the problem presented is the reverse.

 

[Billy T]

... Anyway, given those examples of variously long single-photon wavetrains, what if anything does the theory have to say about lateral extent - 'effective X-section'?

I have never seen the width / cross section of a photon discussed. Rarely is even the measurable length noted. If I had to make a guess, I would say more than half its energy passes thru a circle of diameter equal to its wave length, but there is some conceptual difficulty with that, as its wavelength is a function of the frame you are in yet the orthogonal diameter of a circle is nearly frame independent - at most a second order effect compared to the linear red or blue shift.

 

[paddoboy]

As has already been noted, light has no mass, and subsequently no inertia.
What that means is that it is not possible to accelerate light by applying a force to it. It is not possible to change the speed of light by applying a force to it.
One consequence of that fact is that the speed of light is always
the same. The speed of light is constant.

Attempts to apply a force to change the speed of light will only affect the frequency and direction, and certainly not speed.

I never really believed that something like solar sails could actually work.

Light sails are certainly possible....Have you heard of a Crooke's Radiometer?
http://en.wikipedia.org/wiki/Crookes_radiometer


The methodology is discussed here.....
http://www.universetoday.com/10516/audio-nasa-tests-a-solar-sail/

 

[paddoboy]

This may not be easy to do, since unlike matter and energy, which is tangible, space-time is an abstraction.

No, far from it.....space exists: If it didn't, everything in this Universe would be all compacted to a dimensionless dot. Time exists: If it didn't, we would not be here and neither would space and the evolution of space would not have started at what we know as the BB.
As has been shown many times in the last 100 years or so, neither space and time are absolute quantities as once thought....
Henceforth as Minkowski put it.....
"The views of space and time which I wish to lay before you have sprung from the soil of experimental physics, and therein lies their strength. They are radical. Henceforth space by itself, and time by itself, are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality".
The above taken from....
http://www.spacetimesociety.org/minkowski.html

And of course as has been mentioned many times, this same spacetime, has been effectively measured along with its deformation in the presence of massive bodies by GP-B.

 

[Billy T]

... Light sails are certainly possible....Have you heard of a Crooke's Radiometer?
http://en.wikipedia.org/wiki/Crookes_radiometer

Yes a photo reflected reverses its momentum but one absorted on the black sides of the Radiometer only transfers one, not two units of momentum to blades of the radiometer. I.e. by photons, the silver side is pushed harder than the black side; but if you look carefully at the dynamic illustration of your link, copied below, you see just the opposite!
This is because the residual gas in the "vacuum" strikes both sides with equal pressure and frequency of molecular hits. However the molecules leaving the black side have been heated a little - leave faster - get extra thrust from the black side. To give that extra thrust to the molecules, there is a stronger "reaction force" on the black side. So the silver side actually is the advancing one.

Thus the Crooke's Radiometer does NOT demonstrate that the photon has momentum. But solar-sail space craft do and have been launched. I think they had too much trouble keeping the sail deployed at the desired angle (or even keeping it flat, not folded on its self) so none have been used AFAIK, for 20 years or so.

It amazes how few actually see it as it is!

 

[brucep]

There are several aspects to answering that. First one is simply to again point to that classic 1931 paper by Tolman, Ehrenfest, Podolsky. In that picture, light indeed warps spacetime as formalized in the EFE's and in particular in accordance with EM contribution to stress-energy-momentum tensor. And in that picture, what we now call photons do in general 'pull' on each other, except when they are exactly co-moving. Otherwise, the example I gave of a box full of random radiation should have no active gravitational mass - a photon exterior to the box would not deflect gravitationally. That would clearly contradict the notion of mass-energy equivalence central to both SR and GR. [It was I think several years later that Tolman realized there was a problem with that original paper, requiring an additional, negative formal contribution from stress in the container to arrive at, as I emphasized, a net radiation active mass contribution according to m = E/c^2, and not twice that value as originally determined.]

That's the formal GR position and yes I see no way it can be correct. And if someone wants to open a new thread just on that topic of light/photon active mass (or not), that's the place to really discuss it further.

Really? So the stress energy tensor doesn't describe the contribution light makes to the local spacetime curvature? Well that's the way GR describes it and who gives a crap about effective gravitational mass of light? For light it's energy and momentum and you think this can't be right? It's part of how the theory works for doing physics so you must think the theory can't make accurate predictions for the natural phenomena in the theories domain of applicability. I'm not interested in starting a nonsense thread for you.

 

[brucep]

And I know what you have said, but exactly what you intend still eludes me. So I will ask question a different way:

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 laser's photons by their 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. Your discussions leave me in doubt as I am far from an expert in GR, and not nearly as good in SR as I was 50 years ago.

The photons energy and momentum contribute to the local spacetime curvature. The local spacetime curvature is the gravity. It determines the geodesic path [which is essentially straight in local proper frames]. The laser beam is a pulse of light and GR doesn't predict anything about quantum aspects associated with the laser light. You keep wanting me to answer questions about the quantum aspects of light which I tried to avoid since It doesn't have anything to do with it's predicted path through the universe and it's not my strong suit. The local geodesic path is an invariant while coordinate dependent geodesic paths are coordinate dependent. For example the coordinate dependent analysis predicts the remote coordinate speed of light can vary while the local speed of light is an invariant. If you want to ask questions about the quantum aspects of laser light I'm not a good resource. A good place for that would be reviewing a Feynman diagram, from QED, describing the physics you want to know about.

 

[Billy T]

(1) The photons energy and momentum contribute to the local spacetime curvature. ...
(2) You keep wanting me to answer questions about the quantum aspects of light which I tried to avoid since It doesn't have anything to do with it's predicted path through the universe and it's not my strong suit.

(1) 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, so oscillate thru each other with 1 micron amplitude "over shoot" before being stopped and starting to be drawn back towards each other again, to pass thru each other and over shoot a micron on the other side - completing one "lateral oscillation cycle." and repeating this lateral oscillation "for ever."

Why can you not simply say Yes or No as I asked you?
(2) I have NEVER made or suggested any QM changes or question. I know QM rather well - I have done calculations of its effects even in the original matrix formulation and well as with Schroder's equation formulation! You seem to keep ducking a simple direct answer to the question I have now posed in two very different ways.

... If you want to ask questions about the quantum aspects of laser light I'm not a good resource. A good place for that would be reviewing a Feynman diagram, from QED, describing the physics you want to know about.

I don't so "want" but you seem a little confused. The first classical QM problem any graduate student does is to compute the permitted energy levels of a particle in a box with infinitely high potential walls, then usually one wall is made finite so you can calculated the "tunneling effect." Next you may derive the uncertainty principle,* probably about at this stage you will mathematically watch a mixed state (sum of two weighted eigenvectors) evolve, etc.

For all of this Feynman diagrams are basically useless. I never used them in my first QM course - they find application mainly in nuclear interactions where "virtual particles" are important and you need to consider all possible sets of them.

I admit to being very weak in GR, but doubt there is much you could teach me in QM. - Part of why I did not ask you ANYTHING about QM. There is no doubt a lot you could teach me about GR but you seem not able to give a direct answer to simple question: Do two photons traveling side-by-side, only one micron apart, attract each other via their gravitational interaction (by their warp of space time) by their ("stress-energy tensor) or any other terms you prefer?

Assuming that you are saying {with (1)} that photons do mutually attract, is it conceptually possible that a Black Hole could have no rest mass as it is only "zillions of photons" orbiting the center "like a swarm of bees" due to the mutual warping of space about that point?

* learning while doing so that most pairs of observable can in principle be measured as accurately as you like, I.e. the uncertainty principle only applies to specific pairs whose "operators" "don't commmute" under the Hamiltonian. Many people who don't know much about QM falsely assume that precise measurement of one variable must disturb the other so its value can not be precisely known. That is not it at all. I hope this did not teach you any QM, but would not be surprised if it did.

 

[brucep]

(1) 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, so oscillate thru each other with 1 micron amplitude "over shoot" before being stopped and starting to be drawn back towards each other again, to pass thru each other and over shoot a micron on the other side - completing one "lateral oscillation cycle." and repeating this lateral oscillation "for ever."

Why can you not simple say Yes or No as I asked you?
(2) I have NEVER made or suggested any QM changes or question. I know QM rather well - I have done calculations of its effects even in the original matrix formulation and well as with Schroder's equation formulation! You seem to keep ducking a simple direct answer to the question I have now posed in two very different ways.I don't so "want" but you seem a little confused. The first classical QM problem any graduate student does is to compute the permitted energy levels of a particle in a box with infinitely high potential walls, then usually one wall is made finite so you can calculated the "tunneling effect." Next you may derive the uncertainty principle,* probably about at this stage you will mathematically watch a mixed state (sum of two weighted eigenvectors) evolve, etc.

For all of this Feynman diagrams are basically useless. I never used them in my first QM course - they find application mainly in nuclear interactions where "virtual particles" are important and you need to consider all possible sets of them.

I admit to being very weak in GR, but doubt there is much you could teach me in QM. - Part of why I did not ask you ANYTHING about QM. There is no doubt a lot you could teach me about GR but you seem not able to give a direct answer to simple question: Do two photons travel side-by side attract each other via their gravitational interaction (by their warp of space time) by their ("stress-energy tensor) or any other terms you prefer?

Assuming that you are saying {with (1)} that photons do mutually attract, is it conceptually possible that a Black Hole could have no rest mass as it is only "zillions of photons" orbiting the center "like a swarm of bees" due to the mutual warping of space about that point?

* learning while doing so that most pairs of observable can in principle be measured as accurately as you like, I.e. the uncertainty principle only applies to specific pairs whose "operators" "don't commmute" under the Hamiltonian.

No I didn't say anything like your first paragraph. You're Mixing up domain of applicability. GR is a classical theory of gravity and doesn't make any predictions for quantum phenomena. I can't find a reason for reading the rest because I don't have anything else to say about it. Good luck Billy T.

 

[Billy T]

No I didn't say anything like your first paragraph. You're Mixing up domain of applicability. GR is a classical theory of gravity and doesn't make any predictions for quantum phenomena. I can't find a reason for reading the rest because I don't have anything else to say about it. Good luck Billy T.

I don't need "good luck" All i wanted was a yes or no to the question you keep ducking.

 

[Trippy]

But solar-sail space craft do and have been launched. I think they had too much trouble keeping the sail deployed at the desired angle (or even keeping it flat, not folded on its self) so none have been used AFAIK, for 20 years or so.

Somebody should let the Japanese know that - they successfully deployed IKAROS to Venus using a solar sail to provide propulsion, and they plan (or planned) to send a larger spacecraft to Jupiter and the Trojan asteroids using a solar sail. Not only did they use the solar sail to successfully accelerate IKAROS to venus, but using LCD's they managed to manipulate the reflectance of portions of the solar sail to effect attitude control. As of last contact it had accelerated by a total of 400 m/s using its solar sail.

 

[OnlyMe]

No I didn't say anything like your first paragraph. You're Mixing up domain of applicability. GR is a classical theory of gravity and doesn't make any predictions for quantum phenomena. I can't find a reason for reading the rest because I don't have anything else to say about it. Good luck Billy T.

Bruce, Billy asked a question that clearly crosses the boundary between GR and QM. You continually ignore that and try to respond by saying, GR says....

GR.., CANNOT answer the question that was asked.., unless you can say exactly how a photon contributes to gravity.., and continually falling back on spacetime curvature is gravity does not work...

That is why there is so much theoretical work being done on quantum gravity.

Billy, the question you have asked cannot at this time be answered within the context of either GR or QM, with any certainty. At best you can get specualtions.

The question does not lend itself conceptually to any implied dimensions of wavelength and frequencies, because a photo receptor or emitter, could be as small as a single pixel, much smaller than any conceptual dimension one might associate with the size of a photon's wavelength/frequency. On the other hand, as a point particle a photon has no rest or inertial mass and thus no gravitational mass.., and no independent gravitational field.

My answer I gave long ago in the thread, no two individual photons exert any gravitational influence on eachother... Two photons traveling side by side will do so to the end of time or space, whether it is flat or not. Equally as waves they don't interfere with one another, and thus once again do not affect the path of the each other. Two photons do not become one and one photon does not become two... If this were not true we could make no sense at all of any of the information of the distant universe.

 

[brucep]

Bruce, Billy asked a question that clearly crosses the boundary between GR and QM. You continually ignore that and try to respond by saying, GR says....

GR.., CANNOT answer the question that was asked.., unless you can say exactly how a photon contributes to gravity.., and continually falling back on spacetime curvature is gravity does not work...

That is why there is so much theoretical work being done on quantum gravity.

Billy, the question you have asked cannot at this time be answered within the context of either GR or QM, with any certainty. At best you can get specualtions.

The question does not lend itself conceptually to any implied dimensions of wavelength and frequencies, because a photo receptor or emitter, could be as small as a single pixel, much smaller than any conceptual dimension one might associate with the size of a photon's wavelength/frequency. On the other hand, as a point particle a photon has no rest or inertial mass and thus no gravitational mass.., and no independent gravitational field.

My answer I gave long ago in the thread, no two individual photons exert any gravitational influence on eachother... Two photons traveling side by side will do so to the end of time or space, whether it is flat or not. Equally as waves they don't interfere with one another, and thus once again do not affect the path of the each other. Two photons do not become one and one photon does not become two... If this were not true we could make no sense at all of any of the information of the distant universe.

 

[brucep]

Bruce, Billy asked a question that clearly crosses the boundary between GR and QM. You continually ignore that and try to respond by saying, GR says....

GR.., CANNOT answer the question that was asked.., unless you can say exactly how a photon contributes to gravity.., and continually falling back on spacetime curvature is gravity does not work...

That is why there is so much theoretical work being done on quantum gravity.

Billy, the question you have asked cannot at this time be answered within the context of either GR or QM, with any certainty. At best you can get specualtions.

The question does not lend itself conceptually to any implied dimensions of wavelength and frequencies, because a photo receptor or emitter, could be as small as a single pixel, much smaller than any conceptual dimension one might associate with the size of a photon's wavelength/frequency. On the other hand, as a point particle a photon has no rest or inertial mass and thus no gravitational mass.., and no independent gravitational field.

My answer I gave long ago in the thread, no two individual photons exert any gravitational influence on eachother... Two photons traveling side by side will do so to the end of time or space, whether it is flat or not. Equally as waves they don't interfere with one another, and thus once again do not affect the path of the each other. Two photons do not become one and one photon does not become two... If this were not true we could make no sense at all of any of the information of the distant universe.

No he didn't ask a question that includes both theories. He asked a question about how light effects the gravitational field and I chose to explain it using GR since it makes empirical sense to do so. He included the other stuff when he was paraphrasing what he thought I said. I can't do much about that, as I pointed out several times, other than to try and repeat my answer in a way he can understand it. A group of photons, the pulse of light, interact gravitationally in the way I said many times to no avail. The group contributes to the local spacetime curvature and the spacetime curvature [gravity] determines the geodesic path. Light is in free fall just like everything else. The path of light is different because it doesn't have mass. Lights equations of geodesic motion are different from the equations of motion for objects with mass. For example you can derive the equations of motion for light from the Schwarzschild equation of motion by eliminating the term for proper time and taking m to the limit 0. You're pretty good at mixing up domains of applicability yourself. Common source for misunderstanding what physics you're talking about. I'm moving on from this discussion.

 

[brucep]

I don't need "good luck" All i wanted was a yes or no to the question you keep ducking.

The answer is No. How many times do you need to be told that without me being rude? The only thing I'm ducking is your persistent confusion. Surprising that you can't understand what I've been saying with respect to the path of light as derived from the theoretical model we call GR. Probably my fault but I'm moving on.

 

[OnlyMe]

No he didn't ask a question that includes both theories. He asked a question about how light effects the gravitational field...

Following is Billy's first post on the issue. If you read it through he is asking about gravity, but he also introduces questions formed in a context normally associated with QM and very rarely if ever mentioned within the context of GR... So his five or six original questions, do cross the divide between GR and QM.

I have a few questions (sort of on topic but not much related to BH.):
First is: Do photons have a very tiny gravitational field?
They have no rest mass so I guess the answer is no* (and at end of post support that with simple observation). Here is the problem that makes me have some doubt:

An electron and positron far from all other mater and 2 cm from each other, I think, could be orbiting about their mass center. A meter from it I think there should be a weak and slightly modulated gravitational field. (Modulated as in 1/4 the orbit period the field at 1M from the center of mass changes in magnitude only (not direction) from:
M/(1.01)^2 + M/(0.99)^2 To 2M/(1.0...0X)^2
(Yes I'm too lazy to find X and how many zeros between X and the 1.0 as I'm just justifying "modulated")

Second question: Does this modulation at point 2 meters form the mass center have speed of light delay? - I. e. does not have its max strength (about 25% as strong) exactly when field at 1M from mass center does have its max? - I think "yes.

Third question: These two charges are accelerating so are radiating. Hence spiral closer together will they not? Again, I think "yes."

Fourth question: Eventually they will transform into two ~ 511Mev gamma rays, that travel away from the old mass center point (perhaps the still mass center point if answer to question 1 was yes) will they not?

Fifth question: Does the slightly modulated gravitational field speeding off into space continue but now as a growing "no field hole" centered on the old mass center point? If answer to Q1 was yes, I think there is no hole as that remains forever the mass center of the two gamma rays, but if answer to Q1 is no then I guess there is an expanding field free hole.

Now for my observation supporting the No answer to Q1:
On a clear night I look at some stars - first with one eye then with the other. It is fact that both eye see the same star field. But consider the small (incredibly small) angle the path of the photons reaching my right eye differs from the path of the photons coming to my left eye. If these photons did have mutual gravitational attraction for say 100,000 light year long paths, then the "photo light field" should be "quills of light" with no light voids between. I. e. the field of stars seen by my right eye should not be the same as that seen by my left eye. Likewise, If I did not like the star field one eye was seeing, (other closed) just move head a little to see a different star field.

Comments (or at least what answers do you think correct to my 5 questions?)

* Also the photon's M = E/(c^2) mass is "frame dependent" so that would seem to be a problem with their "bending of space" view of gravity, I think. I do lean to the POV that all energy which is the same in all frames does make gravity. I.e. the gravity from a hot brick deceases slightly as it cools - Its temperature (random KE) is same in all frames. Any arguments on this POV? Note that jar of half ice & half water has T = 0C in all frames.

BTW my intent was not meant as a negative comment on your posts. It was meant to point out that by answering only from a context limited to GR, your were talking past the intent of his initial inquiry... And then to point out that, that initial inquiry has no clear answer, other than opionion and speculation, because GR and QM have not yet been reconciled as far as this question is concerned.