4 ms·
Light by light scattering is also why we can't see gamma rays above 80 TeV or so from far away (the gamma rays would pair produce e+/e- pairs with CMB photons).
by cozzyd 8y ago
Light by light scattering is also why we can't see gamma rays above 80 TeV or so from far away (the gamma rays would pair produce e+/e- pairs with CMB photons).
- saagarjha 8y agoHow do we detect high-energy cosmic rays, which to my knowledge can exceed this "limit" by several orders of magnitude?
- marcosdumay 8y agoIf you are talking about [1], I think nobody knows how they are possible. https://en.wikipedia.org/wiki/Oh-My-God_particle https://en.wikipedia.org/wiki/Oh-My-God_particle
- saagarjha 8y agoThat article links to a much better written one that appears to discuss this exact issue: https://en.wikipedia.org/wiki/Greisen–Zatsepin–Kuzmin_limit https://en.wikipedia.org/wiki/Greisen–Zatsepin–Kuzmin_limit. Thanks!
- adrianratnapala 8y agoThose rays are unlikely to be photons, so EM-self interaction is not likely to stop them. The articles linked in this sub-thread all speculate/assume that the cosmic rays were protons.
- cozzyd 8y agoThey're not gamma rays :) But a similar limit happens to protons (the GZK limit at 50 EeV, where protons and CMB photons can make a Delta+). For heavier nuclei, photodisintegration will happen at even higher energies.