Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Reflecting Cosmic Rays

  1. Nov 28, 2014 #1
    Just being curious. I was wondering what kind of material you could use to reflect a cosmic ray like visible light to a mirror. It would probably pass right through it, but I was just wondering. =P
  2. jcsd
  3. Nov 28, 2014 #2

    Doug Huffman

    User Avatar
    Gold Member

    Depending on just what daughter products your reflections are allowed to be, any shielding will have some small negative flux - cosmic ray shielding like our atmosphere.
  4. Nov 28, 2014 #3


    User Avatar
    Science Advisor

    Well, you can't make anything like a mirror. You can bounce a few particles off of a shielding material. But different particles will bounce off of atoms in the shielding material at different depths, and as Doug alludes to above, much of the energy that comes back will not be in the muons that make up most of the cosmic rays.

    The fundamental problem is that the incoming muons are going so fast that when they interact with any sort of normal matter, they only see a bunch of atomic nuclei swimming in a field of electrons. The electrons will slow the muons down, while they'll have a rather energetic reaction if they strike an atomic nucleus. The specific type of matter will only impact how much the muons are slowed by the electrons, and how likely the muon is to strike a nucleus.

    As for the impact on the nucleus, the mean energy of muons at sea level is approximately 4GeV, which is around four proton masses. I don't think it's possible for an atomic nucleus to survive an impact of that magnitude: the combination of the muon and the nucleus would be turned into a shower of particles. That said, most of the time such collisions don't happen: the muon just gets slowed down until it nearly stops, and then it decays into an electron and a pair of neutrinos. Most of the energy escapes via the neutrinos, and the electron rapidly slows.
  5. Nov 29, 2014 #4
    That makes sense. Thank you for your answers =P
  6. Dec 4, 2014 #5


    User Avatar
    Science Advisor

    The magnetic field of the Earth deflects a good portion of the cosmic rays, which are mostly charged particles. Now, if mere deflection counts as reflection...
  7. Dec 11, 2014 #6


    User Avatar
    Gold Member

    Yes, magnetic fields can do some of the work, eg in Plasmas for gamma rays...
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook