Steven Manly, Visions of the Multiverse, New Page Books, New Jersey, 2011

There is general agreement among astronomers and cosmologists that about 13.7 billion years ago the universe we live in began with an event generally known as the "big bang" (a term invented by the astronomer Fred Hoyle, who was noted for his scepticism about the theory). It should be understood, though, that this does not mean that the universe expanded into space, but that it was space itself which expanded.

Much of this book is devoted to describing the development of the theories of special and general relativity, and quantum theory. The descriptions of the discoveries and properties of the various sub-atomic particles are fairly interesting. For example, some particles are not fundamental, but are composed of three other particles, called quarks, and these quarks come in six varieties, known as up, down, strange, charm, bottom and top. These descriptions, though, are perhaps not very enlightening to those of us who have not spent years studying higher mathematics and particle physics.

The most interesting part of the book describes the theories of the multiverse. The big bang theory by itself has problems, one of which is that by extrapolating the universe back to its beginning it collapses to a point of infinite density. Although it is possible to make calculations concerning what is thought to have happened a tiny fraction of a second after the big bang, the theory, according to MIT physicist Alan Guth (who described the universe as the "ultimate free lunch") "makes no attempt to describe what 'banged,' how it 'banged,' or what caused it to 'bang.'.

This and other problems with the big bang theory were tackled using an idea known as "inflation". Some physicists also use String Theory, which is based on the idea that fundamental particles can be considered not as points but as string-like objects. Manly attempts to describe these as simply as possible, but I suspect one would need to understand the mathematical treatments in order to make much sense of them.

These theories led to the idea of there being multiple universes, rather than just the one we live in. There are several different kinds of scientifically theoretical universes including, for example, the Fecund Multiverse, in which quantum gravity effects in black holes might lead to the births of new universes isolated by these black holes from the universes that spawned the black holes. There is also a Many-Worlds Multiverse, whose description is worth quoting:

In quantum mechanics, different quantum mechanical outcomes are separated in a mathematical space called Hilbert space. In the many worlds interpretation of quantum mechanics coupled with the concept of decoherence, these different realities emerge as distinct branches of the evolving universal wave function -- effectively parallel universes.
Of course there is also the question of our place in the universe, or universes. Manly briefly describes the discussions between scientists and philosophers on the connection between quantum mechanics and consciousness, and the fact that in the Copenhagen interpretation the collapse of the wave function is caused by observation. This is a topic, however, which appears to be more concerned with philosophy than physics and Manly, perhaps wisely, writes: "I will not attempt to do justice to this subject here".

Although the author has tried to lighten the tone with some of his jokes and witticisms, this book is not an easy read, so you will have to pay attention at the back, there! -- Reviewed by John Harney

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