I read Martin Rees's Before The Beginning
a couple of weeks ago and found it remarkably interesting. But, as Nick said, it's also about 15 years old. I decided I needed something a little more modern, hence this book.
Well, if you're interested in Big Questions, there's no doubt that The Goldilocks Enigma
is a fun read. The first half presents the core problem. When you look at the fundamental laws of the universe, a weird pattern emerges: everything is tuned exactly right for life to be possible. There is a whole row of these "coincidences", as they're generally called. If the early universe, just after the Big Bang, had been slightly more uneven, then galaxies couldn't have formed. If gravity were a bit stronger, stars would have burned up quickly rather than shining for billions of years. If carbon didn't have some very special properties, no elements except hydrogen and helium would have been created. If neutrinos didn't react just as strongly as they do with atomic nuclei, supernovae wouldn't happen and there would be no heavy elements. All of these things, and others, have to work for life to have a chance of emerging. Davies covers more or less the same material here as the Rees book, but his treatment assumes less background; for example, he explains how we know that the universe is expanding, and what a quark is. If you know this kind of thing already, you'll be a little irritated, and probably find the Rees more enjoyable.
The rest of the book looks at possible explanations, starting with the most mainstream ones and moving into more and more speculative territory. Even the mainstream stuff is seriously mind-blowing; we seem to be in the middle of a scientific revolution here. One possibility is that the "coincidences" are just that. It's possible, but seems very much against the odds. An explanation which has won some measure of respectability is some version of the "multiverse". People appear to have constructed reasonably plausible models of what happened in the early stages of the Big Bang, when a mysterious process called "inflation" exponentially expanded the universe, in a tiny fraction of a second, from the size of a proton to the size of, perhaps, a few meters across. As far as I can make out, no one really understands what "inflation" is, but it's the only theory that makes sense of the data, in particular the fact that the universe is so homogeneous.
Many models of "inflation" predict that the process keeps on occurring in different places ("eternal inflation"). Every time it kicks in, you get in effect a new Big Bang which creates a bubble of space-time like the one we live in. There is a huge, perhaps infinite, number of these bubbles, separated by incredible distances which make the size of our own universe look tiny in comparison. Moreover, each bubble universe could come with different flavors of the physical laws; it is not impossible that parts of the laws are set when the universe cools down from its initial superhot state. The strongest evidence to support this idea is the now generally accepted idea that the electromagnetic and "weak" nuclear forces are the same thing at high enough energies; the two forces were the same in the early universe, and then split apart. It's speculative, but maybe other and more dramatic changes in the physical laws happened even earlier.
If this account is roughly correct, and "eternal inflation" means that the Big Bang happened many times, then you could indeed in effect have many universes, all with more or less different versions of the physical laws. We just happen to be one of the ones which got the right combination of numbers. It doesn't seem out of the question to investigate the "multiverse" hypothesis scientifically, making testable predictions: in particular, statistical arguments suggest that, when a constant needs to have a value in a particular range to make life possible, we would usually expect it to have a value that's only just good enough, rather than being in the middle of the range. People have been trying to explore this line of reasoning using the strength of "dark energy", which is one of the critical numbers; so far, the results are unclear.
This was the section of the book I found most interesting. Afterwards, it got very speculative indeed, and often seemed to be straying into what to me felt like science fiction or mysticism. It was still fascinating to see Davies, clearly the veteran of many cosmological bull sessions, methodically going through the possibilities. One explanation, of course, is that the universe was designed by a Higher Intelligence. This is a solution, but has no explanatory power; we have no way of knowing anything about the the Higher Intelligence, and there is still the problem of where it
came from. ("Who created God?") A twist I hadn't seen before is a cross between the "multiverse" and the idea that we are living in a simulation ("The Matrix"). If there are an infinite number of universes, the argument goes, then some of them must have advanced enough technologies that they can create simulated Matrix-style universes. It's much easier to create a simulated universe than a real one, hence statistically we are most likely living in a simulation. I'm afraid this idea sounded to me like pure bullshit, but apparently some people like it.
Another way-out suggestion may appeal to some mathematicians. Perhaps the "Platonic World" of mathematics is the real world, and every consistent mathematical theory exists merely by virtue of being consistent. On this account, the world we see as real is no more than a mathematical abstraction. Nothing needs to make
it real; it already is. I have had this thought myself, and I can't actually see any flaw in the argument, but it still feels too bizarre to be credible. But the final chapters are the weirdest of all. Davies thinks about formulations of quantum mechanics where the observer is an essential part of the theory. Maybe the universe needs us, because it has to have observers; without them, it wouldn't exist. Again, this seems to be me ridiculous, and just shows that those versions of quantum mechanics are mistaken. But if as great a thinker as Wheeler took the argument seriously, I'm probably being a bit hasty in dismissing it out of hand.
Okay, okay... frequently annoying, but fun and thought-provoking. I couldn't put it down. Next, I'm reading Brian Greene's The Hidden Reality
and Julian Barbour's The End Of Time
. I will report in due course!