&gt; As spacetime expands, energy density decreases, space becomes less light-emitting and more transparent, and light already in transit becomes red-shifted. Our field of vision is still technically flooded with light, as it always has been, but by now the red-shift is so extreme that the light is in the radio spectrum.<p>You talk about the radiation generated before 1M years in the universe. This article talked about the light from the existing stars in the universe.