QM + GR = black holes cannot exist

[Layman]

You really ought to try and read and understand that classic article I referenced earlier. In GR, light has no invariant/proper/rest mass, but it does have an effective active gravitational mass (with directional character in general case). A box full of incoherent radiation has in GR a net isotropic 'radiant mass' according to the famous mass energy equivalence E = mc^2. But for reasons touched on, I doubt it really is so. Photon-wall interactions add to the mix though and make it not at straightforward to analyze as for free-propagation-in-vacuum case.

When I read about the possibility of the photon had mass, one thing was for sure is that it didn't have a rest mass that could increase due to relativity. If the photons mass was due to its wavelike interaction with say something like the Higgs Field, then the rest mass of the photon would be like talking about total nonsense. It wouldn't be moving through the Higgs Field as a wave, so then there would be no reason for it to have mass. It seems like some of this type of reasoning needs to be reanalyzed from the discovery of the Higgs Boson, and work on quantum gravity should take more of a direction of describing it as an interaction of the Higgs Field.

I never really believed that something like solar sails could actually work. Then it seems like it would be silly that no one really considered the equation for energy and mass equivalence to be able to just be able to be combined with the equation for the energy of the photon. It comes out in the correct units. I once had a physics teacher tell me that having an equation come out in the correct units was a major key to figuring if that equation was actually valid or not. It would be sad if the only reason why we didn't have a description of quantum gravity was because of the stigma that surrounds SR and how the theory literally breaks down at the speed of light. From a mathematical standpoint, any theory that comes out to be undefined or infinity at a certain value shouldn't be used to figure anything about anything. It always has meant that the theory or equation just doesn't work out for it.

 

[OnlyMe]

You really ought to try and read and understand that classic article I referenced earlier. In GR, light has no invariant/proper/rest mass, but it does have an effective active gravitational mass (with directional character in general case). A box full of incoherent radiation has in GR a net isotropic 'radiant mass' according to the famous mass energy equivalence E = mc^2. But for reasons touched on, I doubt it really is so. Photon-wall interactions add to the mix though and make it not at straightforward to analyze as for free-propagation-in-vacuum case.

Layman, pay special attention to the two sections in bold above. I can't speak to what Q-reeus' intent is or was, but taken together they seem at least to some extent, to be what I have been saying, in one or another of these threads.

We do know that photons carry momentum and it becomes very difficult at times to place that into any coherent context that excludes the concept of mass... So concepts of active and passive gravitaional mass, as well as misleading concepts like relativistic mass, often creep into discussion... But they are a streach or attempts to make sense of something we have difficulty conceptually and putting into words.

When I read about the possibility of the photon had mass, one thing was for sure is that it didn't have a rest mass that could increase due to relativity. If the photons mass was due to its wavelike interaction with say something like the Higgs Field, then the rest mass of the photon would be like talking about total nonsense. It wouldn't be moving through the Higgs Field as a wave, so then there would be no reason for it to have mass. It seems like some of this type of reasoning needs to be reanalyzed from the discovery of the Higgs Boson, and work on quantum gravity should take more of a direction of describing it as an interaction of the Higgs Field.

I never really believed that something like solar sails could actually work. Then it seems like it would be silly that no one really considered the equation for energy and mass equivalence to be able to just be able to be combined with the equation for the energy of the photon. It comes out in the correct units. I once had a physics teacher tell me that having an equation come out in the correct units was a major key to figuring if that equation was actually valid or not. It would be sad if the only reason why we didn't have a description of quantum gravity was because of the stigma that surrounds SR and how the theory literally breaks down at the speed of light. From a mathematical standpoint, any theory that comes out to be undefined or infinity at a certain value shouldn't be used to figure anything about anything. It always has meant that the theory or equation just doesn't work out for it.

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. Most of the theoretical work that attempts to address these issues, is just that theoretical and they toss around ideas and/ or alternate ways to look at issues.., like how photons may or may not be involved with the origin of gravitational fields. This happens in both terms of GR and QG... The two don't fully agree, where the object is to find some common ground or basis for understanding gravitation.

So..,

1. solar sails will work,
2. When your math works out in the correct units and/or as a good description of some observation, it does not automatically make it the best description possible of reality. It just provides a stepping off point for further experimental confirmation, of whatever you are dealing with. I have seen research papers where the math apears sound and yet the conclusions seem to be in conflict. The math is only real to the extent that it describes reality, experience and observation. Beyond that it is like putting on a thinking cap to explore possibilities, when you don't already have a diffinitive answer.
3. the Higgs mechanism is a standard model attempt to explain the mass of fundamental particles like quarks, not protons, neutrons or atoms. The mass of fundamental particles makes up a very small fraction of total mass.
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.

 

[Q-reeus]

When I read about the possibility of the photon had mass, one thing was for sure is that it didn't have a rest mass that could increase due to relativity.

Yep.

I never really believed that something like solar sails could actually work. Then it seems like it would be silly that no one really considered the equation for energy and mass equivalence to be able to just be able to be combined with the equation for the energy of the photon.

Can't follow the last bit but for sure solar sails work - light has inertia p = E/c. One famous bod who embarrassed himself and tarnished his career by denying that was Thomas Gold:
http://www.newscientist.com/article/dn3895-solar-sailing-breaks-laws-of-physics.html
http://www.cfpf.org.uk/correspondence_files/2003-07-04_pearson.php#on
Second linked article has it right. And I see OnlyMe has made the same point.

It comes out in the correct units. I once had a physics teacher tell me that having an equation come out in the correct units was a major key to figuring if that equation was actually valid or not.

More like one necessary minimal requirement.

It would be sad if the only reason why we didn't have a description of quantum gravity was because of the stigma that surrounds SR and how the theory literally breaks down at the speed of light. From a mathematical standpoint, any theory that comes out to be undefined or infinity at a certain value shouldn't be used to figure anything about anything. It always has meant that the theory or equation just doesn't work out for it.

And as OnlyMe points out, SR doesn't break down at c - SR explicitly depends on c. What seems to break down is any reasonable correspondence for photon with classical field picture of a particle convecting with it a gravitating field. I recently came across an interesting lay explanation for virtual particles which hints rather strongly imo that what Einstein's SR denies - the old idea of light propagation in vacuo as a 'disturbance of and through the aether', seems to be in fact eerily close to what QFT envisages:
http://profmattstrassler.com/articl...ysics-basics/virtual-particles-what-are-they/
Of course a very different aether than the 19th C one.
But either way one cannot recover a 'gravitating photon' picture consistent with that of an ultrarelativistic classically gravitating massive particle in the limit as m0 -> 0 but p = constant. It has to be radically different. And here we are again - chatting way off topic. Which is par for the course here at SF.

 

[Billy T]

... EVEN A DROPPED GOLF BALL CAUSES THE WHOLE EARTH TO MOVE TO MEET IT, ...

At about age 10 or 12 when I understood that I decided to "move the earth." First thing I did when getting up was to push the brick sitting on my window sill off and let it fall to ground moving the Earth towards Fixed Star S.

Then after dinner, about 12 hours later, I picked the brick back up, again pushing the earth with my feet towards star S (or one quite near it) and placed it back on my window sill. (I lived in a very modest one story 2 BR house.) I did this most days for more than a month.

Did I move the Earth? If not can you tell why in terms a bright ~11 year old can understand?

 

[RJBeery]

When you first lifted the brick you separated the center of the Earth away from the Earth/brick center of gravity. When you dropped the brick, the center of the Earth again coincided with the Earth/brick center of gravity. The center of gravity never moves relative to the Earth/brick system. What you could have done is throw the brick very hard away from Fixed Star S.

 

[Billy T]

When you first lifted the brick you separated the center of the Earth away from the Earth/brick center of gravity. When you dropped the brick, the center of the Earth again coincided with the Earth/brick center of gravity. The center of gravity never moves relative to the Earth/brick system. What you could have done is throw the brick very hard away from Fixed Star S.

That gets (from the 11 year old) a "B" for effort, but he notes you seem to think the CoG of earth brick system is in fixed orbit about the sun; however, it is already wobbling about the CoG of the Earth Moon system. He wants to know if dropping the brick (and putting it back 12 hours later only every 14 days), moves the Earth Moon CoG or at least th size of the Earth's wobble about that CoG. - That would be more impressive than just moving the Earth.

 

[brucep]

Given a recent statement claiming photons do not gravitationally interact according to GR, looks like I need to repeat myself. According to GR, photons (strictly speaking, light-beams, as photon per se is a concept foreign to classical GR) *do* gravitationally interact in general. The *sole* exception being when such photons/'pencil-lead' light-beams are strictly parallel i.e. co-moving/co-propagating. That is stock standard GR, and afaik was first elaborated by Tolman et. al. back in 1931:
http://authors.library.caltech.edu/1544/1/TOLpr31a.pdf

If anyone wishes to continue disputing that is still the standard GR position and call it 'crank', it would be kind of ironic. Having reiterated my position and reasoning of #319, will take this occasion to firstly retract the following statement made in #330:

I was carelessly applying that to a bullet-like point-particle picture of photon. Some kind of fuzziness has to be assumed, whether owing to position indeterminacy for particle picture, or finite field distribution on a field picture. So all that can be said is that IF a freely propagating photon does have an active gravitational mass, the ensuing field must according to SR be everywhere strictly transverse to the propagation vector k. And among other things this raises some severe issues of which a bit I touched on in #330. So I have genuine doubts the stock standard GR position as above referenced is in fact correct. While there is no doubt about light possessing an effective passive gravitational mass, the more I think about consequences of an active gravitational mass for a freely propagating photon/light-beam, the less sensible it seems. But off-topic to elaborate here.

The comment about photons interacting was to answer the question do they bump into eachother and merge. No, GR doesn't predict any natural phenomena in the quantum domain and if it did it wouldn't predict photons are pulled together and merge. The way everything interacts with the local gravitational field is contribute to the local spacetime curvature which determines the objects local geodesic path. That's how everything interacts with the gravitational field. According to GR. That's what the physics says. You think it might be wrong?

 

[RJBeery]

That gets (from the 11 year old) a "B" for effort, but he notes you seem to think the CoG of earth brick system is in fixed orbit about the sun; however, it is already wobbling about the CoG of the Earth Moon system. He wants to know if dropping the brick (and putting it back 12 hours later only every 14 days), moves the Earth Moon CoG or at least th size of the Earth's wobble about that CoG. - That would be more impressive than just moving the Earth.

Same exact situation, but the Earth/Moon/brick system's center of gravity remains motionless when the brick is moved. Complicating the scenario does not complicate the outcome.

 

[Billy T]

The comment about photons interacting was to answer the question do they bump into eachother and merge. No, GR doesn't predict any natural phenomena in the quantum domain and if it did it wouldn't predict photons are pulled together and merge. ...

I suggested that if identical photons do "warp space" time, and travel "side-by-side" only microns apart for many years they would mutually attract each other and pass thru each other to "over shoot" by 1 micoro before stopping their "over shooting" and then with their mutual attraction do this again, and again etc.
I.e. their common center of mass travels at speed of light and they oscillate with amplitude 1 micron from it "forever."

I mentioned "merge" as the only other alternative to this oscillation, but see no way they can become one of twice the frequency to conserve their total energy. I mentioned that two flash light beams in vacuum cross thru each other with no observable change. Not the slightest mutual scattering as if that did happen we would not see the stars as points. Zillions to the zillionth power of other star's photons have passed thru the light from any star coming to my eye.

BTW, It is worth nothing that the common image / idea of photons as tiny balls of energy is wrong. Photons have appreciable length. Some I once measured were ~30 cm long. Those of the green line from the northern lights are several meters long. (they come from a first order forbidden transition of oxygen and the gas density is so low that the emission is usually completed before any energy level disturbing collision happens - little "pressure broadening" of the spectral lines.) The duration of their emission is unusually long ("delta t" of the uncertainty principle is unusually great) and their energy is very precisely defined. zillions of cycles required for that as simple Fourier analysis will show.

BTW2: It may be possible for many pair of identical photons traveling essentially on same path thru carefully cut non-linear dielectric crystal to merge into (or more accurately generate some of twice their energy). This is one of the best ways to get two perfectly coherent pairs of photons - actually "coherent" is not fully correct either - what you can create is ONE quantum state of net zero polarization or zero spin. If the spin or polarization of one that has reach point 10Km away from the other is measured in less times than 10,000/ speed of light in meters/ second, and found to be + then the other when measured will be -. I.e. the measuring process splits this one mixed quantum system into two separate ones but does not destroy the total spin = zero. etc. It gives the illusion that information has traveled the 10Km faster than the speed of light.

Don't feel bad if you don't believe this - Einstein did not either, at least not until the fact was so clearly demonstrated (if it was before he died.)

 

[OnlyMe]

Same exact situation, but the Earth/Moon/brick system's center of gravity remains motionless when the brick is moved. Complicating the scenario does not complicate the outcome.

RJ, forget the CoG.

When you drop the brick with the star overhead, the earth moves up and toward the star. When you 12 hours later pick the brick up, placing it on the windowsill, the star is underfoot and your feet push the earth toward the star... I think that restates the problem.

The question is why does this not move the earth toward the star?

Rephrasing the question, does not offer an answer.

 

[Billy T]

RJ, forget the CoG. ... Rephrasing the question, does not offer an answer.

No RJ gave the correct answer - he got a "B" instead of an "A" only because the "bright 11 year old" might not be fully persuaded, but ask as I did for him about fact earth brick CoG is wobbling with 28 day period. Perhaps half that rather than half day is time interval needed to change things, the 11 year old thinks.

 

[brucep]

I suggested that if identical photons do "warp space" time, and travel "side-by-side" only microns apart for many years they would mutually attract each other and pass thru each other to "over shoot" by 1 micoro before stopping their "over shooting" and then with their mutual attraction do this again, and again etc.
I.e. their common center of mass travels at speed of light and they oscillate with amplitude 1 micron from it "forever."

I mentioned "merge" as the only other alternative to this oscillation, but see no way they can become one of twice the frequency to conserve their total energy. I mentioned that two flash light beams in vacuum cross thru each other with no observable change. Not the slightest mutual scattering as if that did happen we would not see the stars as points. Zillions to the zillionth power of other star's photons have passed thru the light from any star coming to my eye.

BTW, It is worth nothing that the common image / idea of photons as tiny balls of energy is wrong. Photons have appreciable length. Some I once measured were ~30 cm long. Those of the green line from the northern lights are several meters long. (they come from a first order forbidden transition of oxygen and the gas density is so low that the emission is usually completed before any energy level disturbing collision happens - little "pressure broadening" of the spectral lines.) The duration of their emission is unusually long ("delta t" of the uncertainty principle is unusually great) and their energy is very precisely defined. zillions of cycles required for that as simple Fourier analysis will show.

I know what you asked. And I gave you an answer according to the prediction of GR. In GR we can call it a ''pulse of light', a collection of photons such as what constitutes a laser beam, whose energy and momentum [described by the stress-energy tensor] contribute to the local spacetime curvature which determines the geodesic path of the 'pulse of light'. All the stuff you want to include in the analysis is irrelevant. In GR and quantum mechanics.

 

[Billy T]

I know what you asked. And I gave you an answer according to the prediction of GR. In GR we can call it a ''pulse of light', a collection of photons such as what constitutes a laser beam, whose energy and momentum [described by the stress-energy tensor] contribute to the local spacetime curvature which determines the geodesic path of the 'pulse of light'. All the stuff you want to include in the analysis is irrelevant. In GR and quantum mechanics.

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.

 

[Q-reeus]

The comment about photons interacting was to answer the question do they bump into eachother and merge. No, GR doesn't predict any natural phenomena in the quantum domain and if it did it wouldn't predict photons are pulled together and merge. The way everything interacts with the local gravitational field is contribute to the local spacetime curvature which determines the objects local geodesic path. That's how everything interacts with the gravitational field. According to GR. That's what the physics says. You think it might be wrong?

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.

 

[Q-reeus]

BTW, It is worth nothing that the common image / idea of photons as tiny balls of energy is wrong. Photons have appreciable length. Some I once measured were ~30 cm long. Those of the green line from the northern lights are several meters long. (they come from a first order forbidden transition of oxygen and the gas density is so low that the emission is usually completed before any energy level disturbing collision happens - little "pressure broadening" of the spectral lines.) The duration of their emission is unusually long ("delta t" of the uncertainty principle is unusually great) and their energy is very precisely defined. zillions of cycles required for that as simple Fourier analysis will show.

Good point. I had known of that but somewhere still in my head are arguments from certain QM buffs that prefer to interpret things from a photon-as-particle (plus some kind of 'pilot-wave' presumably) perspective. There are problems with Planck-like loading theory (screen detector clicks/flashes) that point-photon model nicely avoids. The evidently 'neat answers' of QED's counterintuitive formalism is something I have never really gotten into. 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'?

 

[Farsight]

The comment about photons interacting was to answer the question do they bump into eachother and merge. No, GR doesn't predict any natural phenomena in the quantum domain and if it did it wouldn't predict photons are pulled together and merge. The way everything interacts with the local gravitational field is contribute to the local spacetime curvature which determines the objects local geodesic path. That's how everything interacts with the gravitational field. According to GR. That's what the physics says. You think it might be wrong?

That's wrong. The local spacetime curvature relates to the tidal force. The spacetime "tilt" relates to the force of gravity which then determines the object's path. This article by J D Norton isn't ideal, but it does say "The effect of gravitation is to tip the light cones in the direction of the gravitational attraction".

I suggested that if identical photons do "warp space"

A photon has an E=hc/λ wave nature. It is a wave. An electromagnetic wave. Like you said, it can me 30cm long, or longer. It isn't some billiard-ball thing. When a seismic wave propagates through the ground, the ground waves. When an ocean wave propagates through the sea, the sea waves. When an electromagnetic wave propagates through space...

 

[wellwisher]

The conceptual problem comes down to the what came first, the chicken or the egg.

We can't measure space-time, directly. Rather we infer space-time from the motion of matter and/or energy. The question becomes is the construct, called space-time, derived from the curved paths of matter and energy, or are the curved paths of matter and energy the result of the curvature of space-time; chicken or egg?

The only way to answer this would be to measure space-time, all by itself, so we can isolate this apart from matter and energy; show it is self standing. This may not be easy to do, since unlike matter and energy, which is tangible, space-time is an abstraction. I tend to think that space-time is a more compact and practical way to say the same thing, but this approach requires the imagination leading realty. Space-time is more like a lever for the mind that allows an easier way to manipulate reality but is more of an invention than a natural thing. This may be why many people just don't get it; it is not natural but usefully contrived.

 

[PhysBang]

That's wrong. The local spacetime curvature relates to the tidal force. The spacetime "tilt" relates to the force of gravity which then determines the object's path. This article by J D Norton isn't ideal, but it does say "The effect of gravitation is to tip the light cones in the direction of the gravitational attraction".

Yes gravitation distorts lightcones, because of the curvature of spacetime. To actually quote your source, "The gravitational deflection of ordinary objects falling in the vicinity of the sun is due to the curvature of the space-time sheets." The very citation that you provide, as almost always, show that one of your claims is false, in this case that spacetime curvature only creates tidal forces.

Good for you for finding Norton's work however. I urge you to read his work, not cherry-pick specific claims and use his work to support a claim that the author obviously does not believe like you have just done.

A photon has an E=hc/λ wave nature. It is a wave. An electromagnetic wave. Like you said, it can me 30cm long, or longer. It isn't some billiard-ball thing. When a seismic wave propagates through the ground, the ground waves. When an ocean wave propagates through the sea, the sea waves. When an electromagnetic wave propagates through space...

Physics is not done well through analogies. If you have a theory that photons wave space, then show us the theory, along with its predictions and how we can test the theory. This is something that you fail to do and it is why you are presenting fantasy, not physics.

 

[PhysBang]

The conceptual problem comes down to the what came first, the chicken or the egg.

We can't measure space-time, directly. Rather we infer space-time from the motion of matter and/or energy. The question becomes is the construct, called space-time, derived from the curved paths of matter and energy, or are the curved paths of matter and energy the result of the curvature of space-time; chicken or egg?

If one is describing things in the world, then one needs to use space and time together. So one always needs spacetime of a sort to describe physical events. Once one has spacetime, then different relationships between space and time can be made assumptions of a theory of physics. We can then test these theories of physics.

This is what has been done.

 

[Farsight]

Yes gravitation distorts lightcones, because of the curvature of spacetime. To actually quote your source, "The gravitational deflection of ordinary objects falling in the vicinity of the sun is due to the curvature of the space-time sheets." The very citation that you provide, as almost always, show that one of your claims is false, in this case that spacetime curvature only creates tidal forces.

I didn't say that. Remember I've said Riemann curvature, which relates to the second derivative of potential and tidal force, is the defining feature of a gravitational field, because without it your plot can't get off the flat and level in the middle:


CCASA image by AllenMcC see Wikipedia

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.