John Gribbin. In Search of the Multiverse. Allen Lane, 2009. -- Reviewed by Peter Rogerson

Time was, about 500 years ago, when the universe seemed simple, there was the earth at the centre, a few miles above it were the sun, moon and planets going about their orbits on celestial tram lines, pushed by angles, Beyond them was the crystal sphere on which the fixed stars were fixed, slowly rotating around, and beyond that heaven with God a bearded old gentleman on a throne with Jesus on his right hand side. In the centre of the earth was Hell, Satan in the exact centre, with Judas sat on his knee.

But gradually things got more complicated, the sun took over the centre of the universe, then it was relegated to just another star in the galaxy, then the galaxy just one among millions in the observable universe. As recounted by Gribbin in the last twenty years or so, things have got a lot more complicated. For many cosmologists the visible universe is just an infinitesimal speck in a humungous, possibly infinite bubble, which in turn is just one of an infinity of bubbles in some region of perpetually inflating space. And these bubbles and this space between them may be just one of an immense number of three (and other) dimensional islands in some higher dimensional superspace. Some of these islands are just separated by a trillionth of a millimetre in this higher dimensional space. If that were not enough there are all the parallel universes, all the possible histories suggested by the many worlds hypothesis of quantum mechanics. So the super multiverse is, at least, all possible histories of all possible universes.

Now this stuff, it has to be said, is not the product of some vision inspired by ingesting a surfeit of some not altogether legal substance, but serious science, backed by serious scientists and based on serious maths, and given the fact that our bit of the universe (i.e. the visible bit) seems unusually adapted to life, generally taken to be the only alternative to something pretty supernatural.

Even within the multiverse, it might be that our universe was created by aliens in some other part of the multiverse. Making universes in the laboratory is something that human beings can imagine, and can even imagine how to do; and it is probable that the sort of super aliens technically capable of doing that will know lots more physics than we can imagine and be doing things that we can no more imagine than a gerbil can imagine building a nuclear reactor. Then universe building will be something really simple, the sort of thing that the alien equivalent of school children will be doing. If the universe was created by aliens then it is much more probable that it will be as a result of a primary school science experiment than the work of main stream science in a civilisation in the narrow time band in which universe building is frontier physics.

Of course, the argument which makes Gribbin suspect that the universe was designed by aliens not too dissimilar from us - that we find the universe comprehensible - is unlikely to be valid. It seems to me that we just comprehend that part of the universe which is just about comprehensible to human beings. As Gribbin confesses, quantum physics really isn't comprehensible to human beings at all, physicists can do the maths, work with it, and build the modern array of electronic goodies with it, but no way can they understand it.

Further wild ideas follow if 'infinity' means infinity in is full mathematical sense and is not just shorthand for some inconceivably vast number. If the universe and multiverse are truly infinite, then everything that is logically possible will happen somewhere, there will be an infinite number of Peter Rogersons, John Rimmers, Gordon Brown's etc., etc. There will be an infinite number of domains almost identical to each other, ones which are slightly different, in an infinite number of worlds, you dear reader will have won the Nobel Prize, been Prime Minister/President/Pope, but also an infinite number of worlds in which you have been killed in a nuclear war, been the victim of a serial killer, and been a serial killer yourself. An infinite number of worlds in which Oliver Twist wrote a novel called Charles Dickens, with an infinite variety of plots.

Even this vast assemblage of all possible histories of all possible universes as described by Gribbin may not be enough, The physicist Mark Tegmark, has suggested there may be an infinite set of total assemblages, all underpinned by quantum mechanics. Beyond even this there might be other realms where quantum mechanics does not apply, where there is a completely different maths, or realms totally without physics and maths. One of the big mysteries is why is there is something rather than nothing. The answer might be that there is both nothing and something, and perhaps infinitely less than nothing, or more than something (whatever that might mean).

Perhaps in a century or two even this might seem as parochial as Dante's universe does to us, or the wild waffle which marked the breakdown of all of our current theories of physics.

Sadly (or perhaps not!!) as far as these theories go, these realms (or most of them) are quite inaccessible, so they are not likely to explain Fortean mysteries. There is one possible exception, though it is not one I have seen physicists speculate on, (and for all I know the science may just not work out). That would be another membrane universe so close to ours in a higher dimensional space that it would come close to the Planck length at which the uncertainty principle would come into play, so the two membranes have a tendency to merge and re-seperate back and forth. I leave this idea for science fiction writers to develop.

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