Endless Universe – Neil Turok & Paul J. Steinhardt ****
The standard big bang inflationary model of cosmology describes our Universe as beginning as an infinitesimal point of infinite density, energy and mass known as a singularity, where all of the known laws of physics break down. For reasons we are still not certain about, this singularity started to expand. In order to explain certain features of the universe around us (mainly the smoothness of the cosmic background radiation), it has been proposed that our early universe went through an exponentially rapid period of expansion – this is dubbed ‘inflation’.
Although this is the conventional view that cosmology holds about the origins of our universe, it is not without its flaws. In particular some astrophysicists are unhappy about the proposed singularity at the start of our universe. Inflation theory has also had to be tinkered with in order to take in to account the existence of dark matter and more recently dark energy, driving our universe’s expansion to accelerate, contrary to the expectations from the original inflationary theory.
Turok and Stienhardt have been developing their repost to the inflationary model for a number of years. Known as the ekpyrotic (without fire) theory – in essence this puts forward the idea that instead of a singularity, our universe was created as the result of two branes colliding with each other and triggering a ‘big bang’ event. They take this idea further and propose that we live in a cyclic universe (this is not a new idea in itself) where the two branes move along higher dimensional space and regularly collide and separate over periods of billions of years. If they are correct their model could successfully explain the features of our universe that the inflationary model fails to cover.
This book describes in a highly accessible and readable manner the outline of Turok and Stienhardt’s new theory. Mercifully, in place of complex mathematics, diagrams are employed to get across the complex ideas featured. This is no mean feat given the fact that the book’s topic is at the cutting edge of 21st century cosmology.
After deftly describing inflationary theory and pointing out where its flaws lie, the authors give an account of how they developed their theory. Parts of this are auto-biographical, which really gives you a flavour of how cosmologists work.
At present there is little observational evidence to support the ekpyrotic model – as the authors themselves point out. This may be about to change within the next decade or so as gravitational wave detectors could detect the characteristic energy signature from gravity waves created in the brane collision.
The idea that there may well have been a universe before ours has also gained credence as some cosmologists have claimed as recently as this week to have detected imprints in the cosmic microwave background that suggest our universe may have ‘bubbled off’ from a previous universe.