ABSTRACT
This chapter traces some of these extraordinary developments in cosmology and challenges for the future. Some highly respected physicists, such as Astronomer Royal Sir Martin Rees, further propose that following the Big Bang explosion, the present universe may be one of many. The Big Bang theory is not one model but represents a whole class of cosmogonical theories that predict an extremely small hot early universe. One of the reasons proposed for the universe being so large and flat is accelerated expansion of space called cosmic inflation. Stephen Hawking put the whole system in perspective when he calculated from the Hubble constant that the universe is expanding only at a rate of 5-10 per cent every billion years. The red-shifted light of distant galaxies is therefore due to the space expanding or stretching, not the galaxies moving through space.
