It is claimed that all forms of EM radiation travel at the speed of light, but science refuses to prove such to the general public, in any of its forms, while science claims images can travel on light , which any child studying science will know that, is a total lie.
Light ** IS ** EM radiation. The ONLY difference is the wave length. They all travel at the same speed.
There is TONS of research on the speed of electromagnetic radiation. All our satellites functioning and information is dependent on this speed being a constant of just under 300 k/s.