For reasons which may perhaps become clear in later scribblings I’m currently going through a phase of trying to work out just what I am and why I’m here. It’s been driving me crazy but I’m getting a bit more settled with it now.
Short of deciding to believe in a god or something equivalent I think I need to suss out if my existence in this Universe can, at least in principle, be explained rationally. Even if I don’t fully understand it I need to know that someone, or some group, can explain everything right from the beginning of the universe up until now and in as much detail as possible. That’s one hell of a tall order of course but, hey, why not?
So far, I’ve determined that the Universe is probably somewhere around 14 billion1 years old and seems to have appeared from nowhere at all due to some kind of uncertainty. Quantum Theory seems to tell us that you can never be quite sure of anything at all and that right at the beginning (when time equalled zero) there may well have been nothing at all. That, however, is not quite good enough because there would have been a, possibly tiny, chance that what existed was not Nothing but Something. That chance seems to have occurred and the Universe came into existence from nowhere. It’s a bit uncomfortable but I can live with it because some very clever people would be able to explain it to me mathematically if only I were clever enough to understand what they were saying.
OK, so I can accept that Everything is here because of some weird statistical fluke. One minute there was nothing then the next there was quite definitely something except that it’s not really meaningful to speak of minutes because one of the things which came into existence at the beginning was time itself. The Universe had no cause; it just is. It’s all terribly bizarre but does appear to be the best explanation we have at the moment. You can stick a god or two in there somewhere but I don’t see the need to explain one strange inexplicable phenomenon by another.
Can we then explain everything from the beginning right up until the present (remember we’re talking in principle here)? It turns out that we can’t. Opinions seem to vary a little but there does seem to be a reasonably good description of the way the Universe has evolved from rather close to the beginning. It seems that from 10-32 seconds2 or so after the beginning most of the folks who have studied this stuff in depth largely agree. They may differ about details but about the broad outline they generally agree.
10-32 seconds is a very short length of time but isn’t zero. What happened before that? There seems to be more uncertainty about this but by and large the clever folks more or less agree that the Universe became very big very quickly. At somewhere around 10-35 seconds after the beginning the Universe was still very small, somewhat smaller in fact than a proton. Then 10-32 seconds later it was suddenly very big — about 100 million light years across according to some accounts. There’s a furious argument going on about the details but mostly there’s agreement that it had to have happened otherwise it’s impossible to explain why things occur in clumps (stars, galaxies and things) rather than just being one homogenous mass. The clever folks call this period of time the Inflation Epoch at the end of which the expansion slowed to the more leisurely rate which it’s had ever since.
What happened before the time, at 10-35 seconds, when the Universe suddenly started getting very big? I haven’t really been able to suss this out but I more or less gather that it was fairly happy just being very small. Assuming that someone does eventually work out the details of the Inflation Epoch, or replaces it with something else, there should eventually be a reasonable model of everything from the beginning of time right up until the present. Unfortunately, that seems not to be the case. There’s this pesky thing known as the Planck Length which is the smallest length to which anything can be measured without error. Nothing can be measured with an error which is smaller than the Planck Length even in principle. The Planck Length is a fundamental property of the Universe and has nothing at all to do with how good our measuring instruments are — even with a perfect ruler we’ll never be able measure anything smaller. The Planck Length is somewhere around 1.6×10-35 metres — extremely small but not zero — and its existence means that there is also a shortest possible meaningful length of time known as the Planck Time. This is the length of time which a photon would take to travel one Planck Length. The Planck Time then is the shortest length of time which it is possible to measure even in principle. It is somewhere around 10-43 seconds and it is impossible, indeed meaningless, to ask what was happening in the Universe any earlier than one Planck Time after its beginning. The laws of physics break down earlier than one Planck Time and it is thus impossible to ever come up with a model of the Universe from time equals zero up until the present.
This has been exercising my brain now for weeks. I’d set off hoping that it would, in principle, be possible to model the Universe right from its beginning but now I realise that it’s only possible to do so from some time which is only extremely close the beginning. I guess you could stick a god or two in that extremely short length of time too but again I don’t see any reason to compound one mystery with another. I’ll just have to learn to be satisfied with the best which can ever be achieved even if I’m not currently entirely comfortable with it. But then whoever said that the answer would be comfortable?
1 I’m using the usually accepted meaning for ‘billion’ here of one thousand million rather than the old English billion of one million million which is something of a lost cause.
2 That’s 0.00000000000000000000000000000001 seconds.
Posted 30 April 2006, 12:49 BST