Advertisement

Fitness and the cosmic environment


Advertisement

Paul C. W. Davies the actual world – the one that “really exists”? Or, to express it more poetically by using Stephen Hawking’s (1988) words, “What is it that breathes fire into the equations and makes a universe for them to govern?” Only two “natural” states of affairs commend themselves in this regard. The first is that nothing exists; the second is that everything exists. The former we may rule out on observational grounds. So might it be the case that everything that can exist, does exist? That is indeed the hypothesis proposed by some cosmologists, most notably Max Tegmark (2003, 2004), although as we shall see some dispute remains over the definition of “everything.” Obviously, if everything existed, human observations would merely sample an infinitesimal subset of the whole of physical reality. At first sight, the hypothesis “everything exists” appears extravagant – even absurd. The problem, however, for those who would reject this thesis is that if less than everything exists, then there must be some rule that divides those things that actually exist from those that are merely possible but are in fact non-existent. One is bound to ask: what would this rule be? Where would it come from? And why that rule rather than some other? Another objection to the hypothesis that everything exists is that it seems to be an extraordinarily complicated explanation for what is observed, and hence undesirable on the grounds of Occam’s razor. But this can be misleading. In certain circumstances, everything can be simpler than something. Consider an infinite crystal lattice. That regular periodic structure is very simple and can be described by specifying a few bits of data such as the periodicity and orientation of the crystal planes. Now remove a random subset of atoms from this array. By the algorithmic definition of “randomness” (Chaitin, 1988), this subset requires a lot of information to describe it (because it is not “algorithmically compressible”). What remains is, by definition, also random. So each subset, by itself, needs a lot of information to specify it – but the two subsets, when combined, require very little information. In that sense, the whole is simpler than the sum of its parts. In the same way, the set of all possible universes may be (algorithmically) simpler than one or a finite collection of universes. (There is considerable scope for these informal statements to be placed on a sound mathematical footing.) Historically, most scientists and philosophers have assumed that only one real universe exists, and this should probably remain the default position today in the absence of direct evidence for the existence of any other universes. Monotheistic theologians sought to explain the specific nature of the universe (that is, why this universe rather than that) by appealing to divine selection: God made this universe (rather than some other universe that God had the power to make) as a free choice, perhaps with certain outcomes in mind (such as the emergence of sentient beings) (Haught, 1986). On the whole, scientists have ignored the matter, it being deemed that the proper job of a scientist is to take this particular universe as given and get on with the job of figuring out what is going on in it. Some scientists have taken a more proactive stance by positively denying that there is any significance in the specific nature of the universe, taking the attitude that there is no reason why it is as it is rather than otherwise. The problem with this position is that science is supposed to explain the world in logical and rational terms. That is, scientists offer reasons for why things are as they are. Normally, this involves chains of reasoning that ultimately lead back to the laws of physics – considered (at least by physicists) to be the bedrock of physical reality. Thus, in answer to the question of, say, Why did the snow melt?, a (partial) scientific explanation might go as follows: because it was warmed by the sun, which was heated by thermonuclear reactions, which were triggered by the high temperatures of the solar core, which was produced by the gravitational attraction of the solar material, which moved according to the laws of gravity. If we now ask, Why that law of gravity?, the scientist might well respond, “No reason; that’s just the way it is!” So a chain of reasoning in which each step is carefully linked logically and rationally to a level below terminates abruptly with the claim that the chain as a whole exists reasonlessly. This bizarre backflip cuts the ground from under the entire scientific enterprise, because it roots the rationality of physical existence in the absurdity of reasonless laws (Davies, 1991, 2007).


Advertisement

SHARE


Advertisement

2 of 10
Use your ← → (arrow) keys to browse