What would happen if an incredibly high energy photon passed through a human body (or any other material)? When I say incredibly high energy photon, I mean higher than any known energy scales... higher than electronic energy scales, higher than nuclear transition energies, etc...

In my mind, I pictured the photon tearing apart whatever it passed through. However, browsing Wikipedia's article on the Photoelectric Effect, I noticed that the cross section went as $1/E^p$, where I think $E$ is energy and $p$ is some number. So, the probability of an atom being ionized by a high energy photon actually drops with the photon energy (although I don't know what approximations went into this calculation... first order perturbation theory?). If the other light-matter interaction processes also have cross sections of the form $1/E^p$, then an incredibly high energy photon would pass through us without harming us!

Or maybe this question is unanswerable because we don't yet understand physics at such high energy scales. What are your thoughts on this? What do you think would happen if an incredibly high energy photon passed through a human body?

  • $\begingroup$ Please specify the energy of this "incredibly high" energy photon. Also, give the link from where you got $\frac{1}{E^P}$. And then use both of these to work out the effect. I'm just guessing, but it should be like a very very small hole through your body. $\endgroup$ – Hasan Jan 3 '14 at 11:44
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    $\begingroup$ Related: physics.stackexchange.com/q/6435. $\endgroup$ – dmckee --- ex-moderator kitten Jan 3 '14 at 17:05

Thinking about the basic types of ionising radiation, we have alpha particles, beta particles and gamma rays: the alpha/beta are far more ionising, but a lot less penetrating - whereas the gamma (high energy photons) can easily pass through most materials. Along with UV and X-Rays, Gamma radiation is just at a higher frequency and energy (which is what this photon would be). Even for Ultra-high-energy gamma rays, the highest detected is only about 0.16J (a LOT for a photon, but compared to the whole human body not huge). If it hit something it would probably cause damage, but it's very small. Beyond that, it is very theoretical - however this question might be of interest, basing a (very) small wavelength for a photon on the Planck length: What is the minimum wavelength of electromagnetic radiation?


As far as i can see, the high energy of the photon (if we depict that itl only be given out or seen as its KE) will simply pass through us the apparently small size that it has, itl be like shooting a bullet through a football net (a not-to-scale example) even if it passes through us, itl pass through the sub-atomic particles and the ones that itl hit, itl simply lose its energy to them probably pushing them off course a little (seeing how high the energy you stated it has) but the momentum will be fairly less owing to its negligible mass, so in conclusion itl either pass through us or even if it does hit any part of us it will just be an elastic collision with fair amounts of energy loss off the photon and at the end it just might not even be able to pass through , but if it does, itl lose most of its KE and because of its small size if it doesnt encounter any much of the atomic particles itl pass through us with nearly the same KE as before with just about no damage to us

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    $\begingroup$ I'd basically agree: the photons which do interact, e.g. visible, X-ray, do so because their energies are a match for various excitation states of electrons or nucleii. A superhigh energy photon w/ a wavelength below the whoozis limit won't interact except for a rare kinetic collision maybe :-) $\endgroup$ – Carl Witthoft Jan 3 '14 at 12:53
  • $\begingroup$ Hey, some of us are USAians, you (slashdot meme) insensitive clod! There are no nets in HandEgg :-) $\endgroup$ – Carl Witthoft Jan 3 '14 at 13:29
  • $\begingroup$ ^i didnt get you, sorry? $\endgroup$ – divay pandey Jan 3 '14 at 14:14
  • $\begingroup$ "HandEgg" is a slang term created to describe more accurately the shape of an American football and how it's transported, as opposed to Euro football aka soccer. $\endgroup$ – Carl Witthoft Jan 3 '14 at 14:18
  • $\begingroup$ When the energy of the photon very much exceeds the binding energies of the system the photon interacts with the components as if they were free. so @Carl's argument is rather misguided even though it is based on very reasonable principles: he just applying it outside it's range of validity. $\endgroup$ – dmckee --- ex-moderator kitten Jul 23 '15 at 21:33

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