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Posted

If there's a physical limit, it exceeds by far the technology's capability. We can produce photons in colliders, supposedly of a few TeV. Cosmic rays contain much bigger energies; whether each one has been a photon or something else is hard to determine, but they do result partially in photons in a shower.

 

One limit on the propagation over big distances could be the interaction with other photons making the cosmic background. It's not a limit on the existence of photons.

 

An other limit would be a minimum length predicted by unification theories. Very far both from technology limits and from observed photon energies.

Posted (edited)

The only cutoff I can think of would be at the Planck energy scale, where it would likely turn into a black hole.

Edited by elfmotat
Posted

The only cutoff I can think of would be at the Planck energy scale, where it would likely turn into a black hole.

 

Black hole from photon... ?

 

Please elaborate this speculation..

Posted

AFAIK black hole must exist in the all reference frames to be black hole.

Photon doesn't have reference frame.

 

I'm not sure I understand. What do photons having rest frames have to do with them turning into a black hole?

Posted (edited)

 

I'm not sure I understand. What do photons having rest frames have to do with them turning into a black hole?

 

In one frame of reference f.e. v=0, [math]\gamma = 0[/math], photon has one frequency/wavelength/energy

when we will be detecting the same photon from other frame of reference f.e. v=0.5, [math]\gamma=1.1547[/math], photon might be redshifted, or blueshifted, and appearing having lower or higher energy..

Edited by Sensei
Posted

 

In one frame of reference f.e. v=0, [math]\gamma = 0[/math], photon has one frequency/wavelength/energy

when we will be detecting the same photon from other frame of reference f.e. v=0.5, [math]\gamma=1.1547[/math], photon might be redshifted, or blueshifted, and appearing having lower or higher energy..

 

The event would have to take place at some sort of interaction vertex. A high energy photon could scatter off something (an electron, another photon, etc.) with one of the products being a black hole. A free photon won't spontaneously collapse, for the reason you mention.

Posted (edited)

 

The event would have to take place at some sort of interaction vertex. A high energy photon could scatter off something (an electron, another photon, etc.) with one of the products being a black hole. A free photon won't spontaneously collapse, for the reason you mention.

 

After pair production, it won't be photon anymore, but particle at its antiparticle (or shower of them). But they have concentrated mass, and high kinetic energy.

 

The highest energy photons ever detected:

http://en.wikipedia.org/wiki/Ultra-high-energy_gamma_ray

 

The highest kinetic energy believed to be proton ever detected:

http://en.wikipedia.org/wiki/Oh-My-God_particle

http://en.wikipedia.org/wiki/Ultra-high-energy_cosmic_ray

Edited by Sensei
Posted

 

After pair production, it won't be photon anymore, but particle at its antiparticle (or shower of them). But they have concentrated mass, and high kinetic energy.

 

The highest energy photons ever detected:

http://en.wikipedia.org/wiki/Ultra-high-energy_gamma_ray

 

The highest kinetic energy believed to be proton ever detected:

http://en.wikipedia.org/wiki/Oh-My-God_particle

http://en.wikipedia.org/wiki/Ultra-high-energy_cosmic_ray

 

Sorry, but I don't see what any of that has to do with anything.

Posted

In standard quantum electrodynamics there is no cut-off for the energy of a photon. However, we cannot expect that QED will be a good theory for all energies, and as elfmotat has hinted at the quantum nature of space-time itself will become important somewhere near the Planck scale. Maybe before that we will have to take into account new physics.

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