High-Energy Photon: What Happens?

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Discussion Overview

The discussion centers around the hypothetical scenario of a high-energy photon with a wavelength smaller than the Planck length, exploring the implications of such a photon within the framework of physics. Participants engage with concepts from theoretical physics, including energy-mass equivalence and the nature of photons at extreme scales.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant calculates the energy of a 1kg mass using E=mc² and derives a corresponding wavelength for a photon, questioning what would happen if such a photon were produced.
  • Another participant emphasizes the need for certain physical rules to be satisfied, acknowledging the high energy but questioning the existence of a photon with a wavelength smaller than the Planck length.
  • Some participants argue that, according to local Lorentz invariance, a photon can theoretically have any wavelength, including those smaller than the Planck length, and challenge the notion that such wavelengths are impossible.
  • A participant points out a common misconception regarding the Planck length, suggesting that it is not the smallest possible length and that new physics may emerge at that scale, though current understanding does not preclude the existence of such photons.

Areas of Agreement / Disagreement

Participants express differing views on the implications of a photon with a wavelength smaller than the Planck length. While some argue for the theoretical possibility based on established principles, others raise concerns about the physical implications and the validity of such scenarios. No consensus is reached regarding the existence or implications of such a photon.

Contextual Notes

Participants acknowledge limitations in current experimental capabilities to explore phenomena at the Planck scale, and discussions reflect uncertainty regarding the implications of high-energy photons and the nature of spacetime at such scales.

Tumorsito
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Ok guys, so let's suppose we have a mass of 1kg.
We can calculate the energy that matter could deliver. E=mc², roughly 10^8c. Supposing this energy was delivered from a photon (supposing it exists such a processus that could delivery such energy in a single photon), we can calculate the wavelength corresponding. More or less 2x10^-42. Which is less than the Planck length . My question is, (i just started a physics degree so I don't have that much knowledge), when this photon will be produced, what will happen? Space between wavelength is smaller than PL.
 
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Hi T, :welcome:

Don't get carried away -- there are a few rules that need to be satisfied. But ##c^2## in Si units is an awful lot of energy, that's for sure. If it's real, your high-energy photon simply propagates until it encounters something ...
 
BvU said:
Hi T, :welcome:

Don't get carried away -- there are a few rules that need to be satisfied. But ##c^2## in Si units is an awful lot of energy, that's for sure. If it's real, your high-energy photon simply propagates until it encounters something ...
Yes, we are ok for saying it's a lot lot of energy, but just in the case we have a photon this energetic, how could it exists if it has a wavelength less big than pl.
 
By (at least local) Lorentz invariance, the wavelength of a photon can be anything, either much larger or smaller than the Planck length. After all, if you emit a photon in my direction, I can boost to a very fast (close to the speed of light) velocity where the photon wavelength becomes arbitrarily small. Anything preventing me from doing so would violate local Lorentz invariance.

It is not clear to me what your problem is with photons with such a small wavelength unless you believe that local Lorentz invariance fails, in which case you should specify what theory you propose to replace what is currently accepted.
 
Tumorsito said:
how could it exists if it has a wavelength less big than pl.
You may have been victimized by the common misconception that the Planck length is the smallest possible length, sort of the "pixel size" of the universe. This misconception is so common that we even have an Insights article about it: https://www.physicsforums.com/insights/hand-wavy-discussion-planck-length/

Nonetheless it is possible likely that some interesting new physics will appear at that length scale. The Planck length is many orders of magnitude smaller than any of our experiments can reach so anything anyone says about what that interesting new physics might be is complete guesswork. All we can say now is that based on what we know now there's nothing wrong with photons whose wavelength is smaller than the Planck length... but it wouldn't be amazing to find that when we know more we'll have a different answer.
 
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Ok ty everybody for your awnsers. I think it's what Nugatory said. Didnt knew that, thanks for sharing!
 

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