Photons Debate: Is There an Authentic Special Case?

[zoobyshoe]

Yup, that's exactly correct (except I think you mean "ultraviolet catastrophe," but whatever). Long story short: you can treat a blackbody as a box with a bunch of waves in it. If you assume that there is a continuous distribution of possible waves in the box and integrate, you reproduce the correct energy density at low frequencies, but it goes to infinity at high energies. But if you assume the waves are discrete and do a summation instead of an integral, the spectrum goes to zero at high frequency. That's the motivation for assuming that light is quantized. However, it turns out to have other applications. For example, the photoelectric effect is explained by light quantization.

Yes, I should have said "ultraviolet catastrophe".

http://en.wikipedia.org/wiki/Ultraviolet_catastrophe

The wiki article is interesting: it asserts that Planck wasn't actually trying to resolve the ultraviolet catastrophe when he introduced the notion light was quantized. He had other reasoning for it.

Many popular histories of physics, as well as a number of physics textbooks, present an incorrect version of the history of the ultraviolet catastrophe. In this version, the "catastrophe" was first noticed by Planck, who developed his formula in response. In fact Planck never concerned himself with this aspect of the problem, because he did not believe that the equipartition theorem was fundamental – his motivation for introducing "quanta" was entirely different. That Planck's proposal happened to provide a solution for it was realized much later, as stated above.

Though this has been known by historians for many decades, the historically incorrect version persists, in part because Planck's actual motivations for the proposal of the quantum are complicated and difficult to summarize to a modern audience.

"That Planck's proposal happened to provide a solution for it was realized much later, as stated above." So, someone else realized Planck had resolved it.


The "black body", as I understand it, is a conceptual, idealized, perfect, absorber of light. Being perfectly black it absorbs all light and reflects none.

 

[Phrak]

But what if there's NO mass?

Then there's no tiny, tiny little ball of light.

 

[K^2]

Phrak: pull his other leg; it's got bells on it!

But if you pull both my legs, I'll fall!

The following is one method we might examine to establish a lower bound, to first order, for the size of an isolated photon.

Even if you could establish the Schwarzschild Radius that way, which you can't because photon is delocalized, it wouldn't tell you the size of the photon.

A black hole is a singularity. A point object. Despite its event horizon having a cross-section.

 

[Phrak]

But if you pull both my legs, I'll fall!

Even if you could establish the Schwarzschild Radius that way, which you can't because photon is delocalized, it wouldn't tell you the size of the photon.

A black hole is a singularity. A point object. Despite its event horizon having a cross-section.

No, no, no. If it fell into its own black hole it could disappear and reemerge as a glueball. The radius is the photon radius; not the Schwarzschild radius. If it didn't stay in its own photon sphere it would leak away.

 

[alxm]

The wiki article is interesting: it asserts that Planck wasn't actually trying to resolve the ultraviolet catastrophe when he introduced the notion light was quantized. He had other reasoning for it.

Well since we're setting the record straight, he never introduced the notion that light was quantized either, but rather the "oscillators" (an abstraction he used) in material which emit light. It was Einstein with his work on the photoelectric effect who showed you could re-interpret it this way and explain both phenomena.

 

[Dickfore]

Well since we're setting the record straight, he never introduced the notion that light was quantized either, but rather the "oscillators" (an abstraction he used) in material which emit light. It was Einstein with his work on the photoelectric effect who showed you could re-interpret it this way and explain both phenomena.

this^

 

[johng23]

There are some quantum states (e.g. coherent states) where the number of photons is uncertain. But even so I am with you on this. If you don't like the idea of virtual photons then you may not want to consider a near-field antenna like a microwave to be photons, but it is certainly accepted by the QED community.

I don't know what you're talking about with the virtual photons/near field antenna. Can you tell me where I could read about this? (unless you feel like explaining it yourself!)

 

[K^2]

No, no, no. If it fell into its own black hole it could disappear and reemerge as a glueball. The radius is the photon radius; not the Schwarzschild radius. If it didn't stay in its own photon sphere it would leak away.

You know, this sort of humor works a lot better when every other post by other people doesn't contain similar nonsense they genuinely believe.

 

[Phrak]

You know, this sort of humor works a lot better when every other post by other people doesn't contain similar nonsense they genuinely believe.

Hmm. Well, it's all nonsense; Here and every other thread. The true believers in their pet theories make as much sense as anyone--but using a lot less effort too get the same results. The slightest contact between quantum mechanics and general relativity and it all falls down like a house of cards. Loop quantum gravity, MTW, string theory. And what about string theory, and second quantization and the duality revolution? 50 years and it's still quantum mechanics with nonlocal action at a distance. What a mess.

 

[K^2]

Oh, it's not nearly as bad. Quantum mechanics works perfectly within context of general relativity - as long as quantum system doesn't affect curvature in any significant way.

 

[Phrak]

I don't know what bad is, but it's surely fiction. I happen to know three electricians, for various reasons. Each has some very interesting, and bazaar ideas of what electricity is, yet manages to accomplish his allotted taskes none the less. So we have these nice systems in physics that manage to accomplish a few tasks at hand as long as we don't confuse plumbing with dry wall.

We spend our time here in these forums, with 'superior' ideas, casting incantations, often in one-upmanship, in mutually agreed-upon games of make-believe.

I don't find the state of physics today to be bad, just wrong. If it were correct, it would be reduced to engineering with the best challenges gone.

 

[Phrak]

And more. There is a popular ongoing thread in this forum at this time: "Is action at a distance possible as envisaged by the EPR Paradox." What in the world is going on? The framework of physics as it stands today provides no clear path to answer one of the most compact questions, resulting in another thread in a never-ending debate. And this hardly completes the set.

The framework of physics is so poor its not even wrong. Each and every one of the advocates, one having stance A, and another with stance B in diametrical opposition to stance A, is working with the wrong set of axioms.

Maybe one of the old and wizen mentors of physics will show up telling me I'm advancing a personal theory. Gravity and quantum mechanics and logic will never coexist without some fundamental redirection of core concepts that have evolved out of such things as counting on fingers and measuring distance with hand widths.