  Progress in observational cosmology over the past five years has established
that the Universe is dominated dynamically by dark matter and dark energy. Both
these new and apparently independent forms of matter-energy have properties
that are inconsistent with anything in the existing standard model of particle
physics, and it appears that the latter must be extended. We review what is
known about dark matter and energy from their impact on the light of the night
sky. Most of the candidates that have been proposed so far are not perfectly
black, but decay into or otherwise interact with photons in characteristic ways
that can be accurately modelled and compared with observational data. We show
how experimental limits on the intensity of cosmic background radiation in the
microwave, infrared, optical, ultraviolet, x-ray and gamma-ray bands put strong
limits on decaying vacuum energy, light axions, neutrinos, unstable
weakly-interacting massive particles (WIMPs) and objects like black holes. Our
conclusion is that the dark matter is most likely to be WIMPs if conventional
cosmology holds; or higher-dimensional sources if spacetime needs to be
extended.
