"Dumb" question : is there an upper bound on the energy of a photon?

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Discussion Overview

The discussion revolves around whether there is an upper bound on the energy of a photon, exploring theoretical limits, the implications of high-energy photons, and the relationship between photons and electric/magnetic fields. The conversation includes both conceptual and technical aspects.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions if there is an upper bound on the energy of a photon, suggesting that if there were none, it could lead to the creation of extremely powerful electric and magnetic fields with a single photon.
  • Another participant explains that the energy a photon can carry depends on the process that emits it, implying that there is a finite limit based on the energy available in that process.
  • It is noted that high-energy photons can create particle-antiparticle pairs in the presence of other particles, but not in a vacuum, where conservation of energy and momentum must be maintained.
  • Theoretical considerations are raised regarding electroweak symmetry, suggesting that at sufficiently high energies, the concept of a photon may no longer apply as the governing theories change.
  • A participant clarifies that electric and magnetic fields are composed of many photons, indicating that the phenomena associated with single photons differ significantly from those of electric and magnetic fields.

Areas of Agreement / Disagreement

Participants express differing views on the existence of an upper bound on photon energy, with some acknowledging finite limits based on emission processes while others explore theoretical implications without reaching consensus.

Contextual Notes

Participants discuss the implications of high-energy photons and the conditions under which they can create particle pairs, highlighting the dependence on the presence of other particles and the limitations of current theories at high energies.

s00mb
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TL;DR
Looking for an upper bound on energy of a photon.
I was wondering if anybody knew if there was an upper bound on how much energy you can pack into a photon, if such a thing exists. I'm wanting to say no there isn't but it occurred to me that I did not know the answer. Sorry if this is an absurdly easy question but I don't remember reading anywhere that said whether there was or was not one. If there was not one wouldn't that mean that you could create an extremely powerful electric and magnetic field with just a single photon? Also, wondering if anyone knew if someone recorded a record for the most high energy beam of photons? Just curious thanks for feedback! :) -James
 
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s00mb said:
if there was an upper bound on how much energy you can pack into a photon

It depends on what kind of upper bound you mean.

Any photon is going to have to come from some process that emits energy, and how much energy can be packed into that photon is going to depend on how much energy the process that emits it can produce and pack into one photon. I don't know how much energy the most energetic photons we've ever observed from an actual process had, but it will be some finite number.

Also, if a photon has enough energy and is in the presence of other particles, it can create an electron-positron pair--or, if it has even more energy, other particle-antiparticle pairs. (Note that in vacuum this can't happen--a single photon can't create a pair, because there is no way to conserve both energy and momentum. It takes two photons to create a pair in vacuum. But in the presence of other particles that can recoil in response to the pair creation, a single photon can do it.) So once you get to high enough energies, you can't really think in terms of just photons any more, because other particles can be created.

Theoretically speaking, we know that at high enough energies, electroweak symmetry is no longer broken, and if electroweak symmetry is not broken, there are no "photons" in the sense we use the term; the set of gauge bosons for the electroweak interaction is different. So it wouldn't make any sense to think of a "photon" having energies that high because at that high an energy the theory that describes things in terms of "photons" wouldn't apply.

s00mb said:
if there was not one wouldn't that mean that you could create an extremely powerful electric and magnetic field with just a single photon?

No, because the kinds of things we call electric and magnetic fields are made up of huge numbers of photons. The phenomena associated with single photons are very different from the phenomena associated with electric and magnetic fields.
 
That makes sense. Mostly in reference to the comment about high energies. I knew about the process of creating photons had to be finite I was just wondering if there was a theoretical limit thank you.
 
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