The Multiverse - the universe is not enough

[Rick]

BBC Radio 4's "In Our Time" this morning was worth a listen. Participants were Martin Rees, Fay Dowker, and Bernard Carr. Catch the repeat this evening at 9:30, or download the podcast (usually available for a week only).

From: http://www.bbc.co.uk/radio4/history/inourtime/

If you look up the word 'universe' in the Oxford English Dictionary you will find the following definition:

"The whole of created or existing things regarded collectively; all things (including the earth, the heavens, and all the phenomena of space) considered as constituting a systematic whole."

That sounds fairly comprehensive as a description of everything, but for an increasing number of physicists and cosmologists the universe is not enough. They talk of a multiverse – literally many universes – to explain aspects of their theory, the character of the universe and the riddle of our existence within it. Indeed, compared to the scope and complexity of the multiverse, the whole of our known reality may be as a speck of sand upon a beach.