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Originally posted by Neon Haze
Originally posted by Tom Bedlam
The stress-energy tensor in GR says that they do. Not because they have mass, but because they have energy.
As far as warping space-time, since photons have energy, even one is enough, by the stress-energy tensor in GR. This is the substance of Einstein's paper, and Carlip's, among several others which I cited above.
This is where I believe you have it all wrong, and I'm not alone.
Does Light Produce a Gravitational Field?
Originally posted by Tom Bedlam
So, just to be clear, you refute GR's stress-energy tensor, in that it describes light as possessing a gravitational field due to its energy?
Originally posted by Abandon777
Photons must increase and decrease in energy or our understanding of space/time is all sorts of screwed up since the RedShift of photons is what is used as the measurement of universal expansion. (Not to say our understanding of spacetime isn't all sorts of screwed up....heh just that huge chunks of SM are based on it).
Originally posted by Neon Haze
I don't refute GR's stress energy tensor at all. I simply state you cannot relate density and flux of energy and momentum to light.
In Loop Quantum gravity as I stated earlier a photon is not exactly considered a particle, light is propagated by braided space-time vibrations. There is no braid to describe a photon.
The only time I ever use the term photon is in attempting to relate concepts into GR and SR.
I hear what you are saying and if we are talking about reality in a classical sense then let's not get confused between light waves and a single photon.
In classical quantum physics the concepts of "intensity" and "amplitude" do not apply to an individual photon.
It is outrageous that Tom is suggesting that light would somehow gain more and more energy as it bounced around a mirror box indefinitely. I will re-state my earlier argument... No MATHS can add up to create a singularity based on photonic energy alone.
The photon in a mirror box would bounce around will split into many photons in correlation to quantum theory... but the energy carried by the photons would equal exactly the same as the original. There can never be an increase in energy output of a system without some change in the input…. It’s a principle law of thermodynamics.
This is such simple physics it's really frustrating to hear that people often get bogged down in theory when the answer is truly just a single step away.
Here is a paper that is attempting to marry observations in classical science to validate Loop Quantum Gravity.
As I mentioned earlier by the time our students have reached us we hope all of this historical classical learning has been absorbed and questioned.
The nature of our classes has always been on pushing back the boundaries and looking not only at conjecture for new and interesting idea's but also in allowing our students some freedom to reach out and prove or disprove so called established laws.
Tom is obviously studying a subject that is not open for discussion in this way and as such I understand his inability to open his mind to concepts outside of what a text book states.
And I might also add that if there are subs out there with nuke missiles in them I would want a man like Tom in sonar.
Originally posted by jbondo
Since you are inferring to think beyond the textbook yourself, do you believe the concept of time travel is feasible? If so, do you see a direction to start looking for answers?
Originally posted by fullbrain
Sorry to break it to you, but Back To The Future was only a movie!
An article on the work titled "Paradox in Wave-Particle Duality" recently published in Foundations of Physics, a prestigious, refereed academic journal, supports Albert Einstein’s long-debated belief that quantum physics is incomplete. For eight decades the scientific community generally had supported Niels Bohr’s ideas commonly known as the Copenhagen Interpretation of Quantum Mechanics. In 1927, in his “Principle of Complementarity,” he asserted that in any experiment light shows only one aspect at a time, either it behaves as a wave or as a particle. Einstein was deeply troubled by that principle, since he could not accept that any external measurement would prevent light to reveal its full dual nature, according to Afshar. The fundamental problem, however, seemed to be that one has to destroy the photon in order to measure either aspects of it. Then, once destroyed, there is no light left to measure the other aspect.
Dr Carlip:
Following a recent publication in smithsonian.com by
Dr Mallett (www.smithsonianmagazine.com...),
we’ve been having a small tiff on a forum about something
which I thought was relatively straightforward and non-conjectural.
Oddly enough, the argument isn’t about Dr Mallett’s theory per se,
but whether or not a photon has any gravitational effects at all, much
less that they can cause Cauchy horizons, closed time-like curves or
singularities.
I say that it’s been pretty much accepted since Einstein’s paper in 1906
that photons cause gravitational fields by their energy, through the stress-energy
tensor in GR. I’ve quoted Wheeler, geons, Podolsky, you, Einstein’s box, Baez et al,
posted links to refereed papers and what not, and still there are some that say
that since a photon has no rest mass, there is no associated gravitational field.
I’m standing alone, one poor EE working on a masters in Physics, vs a proclaimed
PhD in quantum physics.
In a nutshell, could you give me a quote I can drop in, whether it supports my
position or no? If you say I’m wrong, then I’ll post that too.
Thanks,
Tom
His response:
There are a number of different levels on which this can be addressed:
1. Theory: it is clearly and unambiguously true that in the general
theory of relativity, light gravitates. The source of gravity in general
relativity is not just rest mass, but the stress-energy tensor, and the
stress-energy tensor for light is not zero. There are exact solutions
of the Einstein field equations for electromagnetic plane waves -- these
date back to 1926 (Baldwin and Jeffery, Proc. Roy. Soc. A 111 (1926) 95).
In his 1934 book _Relativity, Thermodynamics, and Cosmology_, Tolman
has an extensive discussion of approximate solutions of the field equations
with light as the source -- see sections 109 through115. (Section 110,
for example, is entitled "The gravitational mass of disordered radiation.")
Bonnor has a nice derivation and discussion of exact solutions in Commun.
Math. Phys. 13 (1969) 163.
2. Experiment: we know observationally that electrostatic binding energy
gravitates, with an effective gravitational mass of E/c^2 to within a few
parts in 10^10. The limits come from precision tests of the equivalence
principle; there is a good discussion of this in section 2.4 of Will's book
_Theory and experiment in gravitational physics_. Thus at least some
forms of electromagnetic energy definitely gravitate, just as predicted by
general relativity.
3. Experiment + theory: we do not yet have a direct experimental test of
whether free electromagnetic radiation gravitates. We do know, however,
that free radiation responds to a gravitational field (deflection of light),
in precisely the manner predicted by general relativity. If light responded
to gravity but did not itself gravitate, we would have a violation of
Newton's third law, with extraordinary (and extraordinarily unlikely)
consequences -- momentum nonconservation, free energy, etc.
4. Cosmology: in standard big bang cosmology, electromagnetic radiation
gravitates, and for much of the early universe (the "radiation-dominated
era") it was the main source of gravity. If one were to assume that radiation
did not gravitate, it would have drastic effects, almost certainly destroying
the good fits of current models to observation -- for instance, primordial
nucleosynthesis. (On the other hand, this would also require throwing out
general relativity, so it's hard to say what the effect would be -- we would
no longer be able to do quantitative cosmology.)
Steve Carlip
Originally posted by Neon Haze
I notice tom that you haven't authored any threads?? I wonder why that is?
Originally posted by Neon Haze
Simply put, light has no mass and so regardless of how much of it there may be it will never be able to deform space-time. In fact we physicists often use the exact opposite when calculating the location of objects in space.
Originally posted by Neon Haze
Nice Tom very nice... I especially liked the part about the LQG ray....
Tom my best advice meant with the best of intentions, would be not to be blinded by the brilliance of the great thinkers of history... If you do then you run the risk of loosing your own luminosity....
The Seattle scientist who wants to test a controversial prediction from quantum theory that says light particles can go backward in time is, himself, running out of time.