Boltzmann-tail of the Planck-spectrum
15 Oct 2014Can you estimate the time how long would you have to wait until 1. the Hubble space telescope would see a CMB photon at visible energies? 2. XMM-Newton registers a CMB photon at \(X\)-ray energies? 3. Fermi-LAT would register a CMB photon at MeV-energies?