Lee Smolin

THE LIFE OF THE COSMOS

As one of our leading cosmologists, Smolin is well placed to advance daring ideas without straying beyond the boundaries of science, and this is what he does here. His starting point is the by now well-known fact that the existence of a universe with galaxies and stars, and hence our own existence, is critically dependent on a number of physical parameters. If one or more of these differed to only a small extent from what is actually found the universe would be very different from what it is: no stars might form at all, or they might last for too short a time to allow life to develop. This has led some people to conclude that the numbers must have been set by God, and that there is now scientific evidence for the existence of a Creator. Alternatively, it could be the case that the seeming arbitrariness of these values is an illusion and they are really necessitated by the deepest laws of physics, but attempts to find such laws have so far been unsuccessful.

One possible solution to the problem that does not involve a resort to religion is that favoured by Martin Rees among others (see Just Six Numbers). This is the idea that there is an infinite series of universes (the "multiverse"), all with different values for the basic parameters; our universe is one of those with the "right" values, which of course explains the fact that we are here to know about it. However, it's difficult not to feel that there is something rather ad hoc about this suggestion. Smolin's view is similar in some ways but it differs by including elements derived from biology and ecology, including Darwin's theory of natural selection.

Smolin thinks that the laws of physics are not eternal and universal but evolve. This evolutionary process is supposed to depend on black holes, of which our universe is believed to contain a huge number, most of which are the result of the gravitational collapse of large stars. We don't know what happens inside a black hole but one idea is that, when quantum effects are taken into account, the collapsing star doesn't compress infinitely to a point (a "singularity") but instead it explodes or "bounces" back. We would not see this from outside but the explosion would be, in effect, a Big Bang like that from which our own universe is thought to have begun. In this case, Smolin tells us, "time does not end in the centers of black holes but continues into some region of space-time, connected to our universe only in its first moment". So we are invited to picture black holes continually giving birth to new universes, in many of which new black holes will form to spawn further universes in their turn. And of course our own universe, with its Big Bang, is supposed to have originated in this way.

This idea is not new; it was first suggested many years ago by John Archibald Wheeler. But Smolin has added the crucial suggestion that, when a new universe forms, the laws of physics it contains are different, but only slightly different, from those of the parent universe. This allows for something like Darwinian natural selection. Universes whose laws permit the formation of black holes will tend to leave more "progeny" than those with different laws, and hence there will be an increasing chance that any given universe will contain black holes. We thus get a process of natural selection, whereby universes that favour the production of black holes will tend to outnumber other universes. But since black holes are mostly the result of star formation, universes that contain stars and are therefore favourable to life will also become more common. So Darwinian natural selection will tend to favour the development of complex universes like our own.

Smolin admits that it has taken him a considerable time to adjust psychologically to this novel way of thinking about cosmology, but he insists that it is a scientific hypothesis, not empty speculation, and he makes a number of predictions by which it can be tested empirically. Such questions are dealt with further in an appendix which contains replies to published criticisms.

The evolving universe idea comes quite early in the book, and much of what follows consists in drawing out the implications of the idea that life, order, and structure are the natural state of the cosmos and don't need to be imposed from without. Smolin allows his thinking to range quite widely, touching occasionally on philosophy and even theology. Although he is disarmingly modest about his lack of expertise in these fields, unlike some scientists he is clearly widely read outside physics and never fails to be interesting and stimulating.

He has been deeply influenced by Leibniz and a recurrent theme in the book is the question of whether it is possible to "stand outside" the universe. The idea that this is possible, at least for God, seems to have entered Western philosophy via Plato; the same notion appears in Newton, with his picture of the universe as a complicated piece of clockwork set in motion by God. Smolin finds this to be a deleterious view that has led to the concept of a separation between body and spirit and to the hope that help will somehow come to us from outside. There is no outside.

The world will always be here, and it will always be different, more varied, more interesting, more alive, but still always the world in all its complexity and incompleteness. There is nothing behind it, no absolute or platonic world to transcend to. All there is of Nature is what is around us. All there is of Being is relations among real, sensible things. All we have of natural law is a world that has made itself. All we may expect of human law is what we can negotiate among ourselves, and what we take as our responsibility. All we may gain of knowledge must be drawn from what we can see with our own eyes and what others tell us they have seen with their eyes. All we may expect of justice is compassion. All we may look up to as judges are each other. All that is possible of utopia is what we can make with our own hands. Pray let it be enough.