# B High energy photons

1. Dec 1, 2018

### Tumorsito

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 lenght . 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.

2. Dec 1, 2018

### BvU

Hi T,

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 ...

3. Dec 1, 2018

### Tumorsito

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.

4. Dec 1, 2018

5. Dec 1, 2018

### king vitamin

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.

6. Dec 1, 2018

### Staff: Mentor

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.

7. Dec 2, 2018

### Tumorsito

Ok ty everybody for your awnsers. I think it's what Nugatory said. Didnt knew that, thanks for sharing!