2. In Neu theory, radiation is a general term that applies to:
- The emission of photons (from atomic and nuclear events) which are then transported by moving space filling the cosmic volume until they are absorbed by matter.
- The emission of electrons, helium-4 nuclei, and other sub atomic objects from nuclear activity into space with varying kinetic energies.
- The isotropic flux of fully ionized nuclei (cosmic rays) filling space.