Before the Big Bang

Is there a hidden parallel universe?

By BBC News Online science editor Dr David Whitehouse

A new theory for the origin of the Universe is intriguing astronomers with the idea that a "Big Splat" preceded the Big Bang.

It proposes that there may be an unseen parallel universe to ours.

The idea, which is still at the development stage, may provide hints about what happened before our Universe exploded into existence some 15 billion years ago.

The theory has been outlined in the past few days at the University of Cambridge in the UK and the Space Telescope Science Institute in the US.

Paul Steinhardt and colleagues at Princeton University propose the so-called "ekpyrotic model". It explains important details about the nature of our Universe such as why the cosmos is expanding the way it is.

M-theory

For the uninitiated, the ideas are difficult to grasp. At their heart is string theory, the idea that the fundamental building blocks of space and time are tiny vibrating strings. String theory has excited theorists in the past few years although it has remained very much untested.

Steinhardt's ideas about the origin of the Universe are based on an extension of string theory called M-theory.

M-theory does not do away with the Big Bang. The evidence that everything emerged from a 'fireball' with a temperature of 10 billion degrees, expanding on a timescale of one second, is now very compelling and uncontroversial.

Instead, M-theory looks at events before the Big Bang, proposing that the Universe has 11 dimensions, six of them rolled up into microscopic filaments that can, for all intents, be ignored.

Professor Sir Martin Rees of Cambridge University told BBC News Online: "Steinhardt and his colleagues offer a fascinating idea, invoking the idea of more than one universe embedded in higher-dimensional space."

The ideas won't be firmed up until we have a proper understanding of space and time, the 'bedrock' of the physical world

Professor Sir Martin Rees

The action of the Universe takes place in five-dimensional space. Before the Big Bang occurred the Universe consisted of two perfectly flat four-dimensional surfaces.

One of these sheets is our Universe; the other, a "hidden" parallel universe.

According to the Princeton researchers, random fluctuations in this unseen companion universe caused it to distort and reach towards our Universe.

The floater "splatted" into our Universe and the energy of the collision was transformed into the matter and energy of our Universe in a Big Bang.

According to Professor Sir Martin Rees: "All these ideas about the ultra-early universe highlight the link between cosmos and micro-world - the ideas won't be firmed up until we have a proper understanding of space and time, the 'bedrock' of the physical world."