Horizons: Parallel Universes

00:00:03 Imagine you could find an explanation for everything in the Universe

00:02:13 The only explanation which anyone could come up with

00:04:17 It's a dream which has driven the work of almost every physicist.

00:06:35 In Britain the famous physicist Stephen Hawking

00:08:30 All of a sudden we realised the Universe is a symphony

00:10:38 We have confidence in extrapolating back from the present

00:12:39 There would be no awkward gaps

00:14:07 you discover what we call a singularity, a cosmic singularity

00:16:06 But just as the scientists were about to give up hope

00:17:59 We normally think of ourselves as living in a three-dimensional world.

00:19:37 working to tease out all the properties of the known universe

00:21:08 Now something almost magical happened to the five competing String Theories.

00:23:11 They stretched and they combined.

00:24:30 there was a theory which might explain everything in the Universe

00:26:24 At first this idea wasn't taken very seriously

00:28:20 and stick it on top of a metal pin.

00:29:52 but by the time it reached us it would only be a faint signal.

00:31:37 They may be completely different with completely different laws of nature operating.

00:33:26 In fact they either move away from each other, or they bang into each other

00:35:34 had been brought together to explore its implications.

00:36:59 and Neil sort of pitching in and saying well

00:38:52 It cannot be perfectly flat. It has to ripple.

00:40:32 the collision of those can be explained within M Theory

00:42:39 But this isn't quite the end of the story.