A beam of which of the following will produce a magnetic field? Gamma rays X-Rays Neutrons Protons Now, the answer they want is protons, to emphasize that moving charged particles create magnetic fields. But is that really accurate? Do moving photons NOT consist of a changing magnetic field that propagates as it travels, and could be described as creating the field? OR, couldn't you think about it as the field always exists everywhere, but the moving protons, or the moving photons are only creating changes in the EM field?