Gamma ray astronomy, the branch of high energy astrophysics that studies the sky in energetic ?-ray photons, is destined to play a crucial role in the explorati

A review of the current observational knowledge and understanding of the cosmic X-ray background.

Proceedings of the NATO Advanced Study Institute on the Cosmological Background Radiation, Strasbourg, France, May 27-June 7, 1996

This is the story of the cosmic background radiation, the "afterglow" of the Big Bang in which the Universe was born. Fifteen billion years after the event, the