Intergalactic Plasma

Radio astronomy observations at 144-m wavelength suggest a plasma filling intergalactic space. This plasma may have one electron and proton pair per 100 cm3. The plasma radiates hectometer waves by free-free transitions. The energy of electrons is replenished from visible light. It interacts with electrons by compton transitions. Accordingly, light tires as it travels through intergalactic space. Such is manifest by a shift in spectral lines toward the red proportional to distance. There is no need for an expanding universe.