expansion of the universe
- noun the process by which the universe is moving outwards after the Big Bang some 20 billion years ago
- The universe is expanding from the Big Bang which marked its birth, perhaps some 20 billion years ago. The expansion is seen by terrestrial observers in the form of the redshift in the radiation from distant galaxies. The Hubble Constant which tells us how fast objects recede for their distance is today put at 55 kilometres per second per million parsecs of distance. Distance has been determined from looking at Cepheid variables in nearby galaxies and by other means for more distant ones, while the velocities are found from redshifts in optical or other wavelengths.