The spectrum of the cosmic background radiation (red curve) obtained in 1990 by the Cosmic Background Explorer satellite (COBE). The spectrum confirmed at a stroke the theory that the Universe started with a hot Big Bang. The cosmic background radiation is the heat of the Big Bang, diluted as the Universe expanded so that it is now just a faint microwave glow a few degrees above absolute zero. It was discovered by US physicists Wilson & Penzias in 1964. The COBE spectrum is an almost perfect fit to an ideal black body" curve, as predicted by theory. COBE was launched on 18 November 1989. The spectrum has been coloured & set against a computerised starry sky background."