Thursday, 13 March 2008

That's entropy, man!

Heat is work and work's a curse
And all the heat in the Universe
Is gonna cooool down 'cos it can't increase
Then there'll be no more work and there'll be perfect peace
Yeah - that's entropy, man! (First and Second Law, Flanders and Swann)
For the past couple of weeks I've been reading up for a talk I'm doing on Darwin, Dawkins and Dictatorship. One of the fascinating ideas I've come across concerns the first and final states of the Universe, as explained by Brian Greene in The Fabric of the Cosmos. So interesting is it, that I thought I'd mention it here.

In the popular imagination, the Universe began as chaos: the Big Bang doesn't sound like a very orderly arrangement of things. But in fact, as Greene explains, from the point of view of thermodynamics and entropy, the Universe began as an incredibly well-organized place, which has been getting more chaotic ever since.

My simplified version of how he explains it is this. Imagine the Universe consists simply of a room of air. Then imagine you are able to enter this room, but when you do, you find to your surprise that all the air is in one half of the room, not the other.

"How can this be?" you ask yourself. The answer lies in the random fluctuations of molecules. Given enough time, every now and then all the air molecules will just happen to wind up in one half of the room. If there were just two air molecules, it would happen frequently. With two hundred air molecules it would happen occasionally, with two thousand, very occasionally, and so on. But even with hundreds of millions, it would still happen once in a while. And it seems you hit one of those occasions.

But then ask yourself this: "Which is the more likely state just before you entered the room: (a) that the air molecules were more spread out or (b) that the air molecules occupied an even smaller space?"

The answer is (a). If the chances of the air molecules all being in just one half of the room is vanishingly small, it is statistically much more likely that they were more spread around the room just before you entered it.

The key to this is the concept of entropy - that and the Second Law of Thermodynamics. All other things being equal, in a physical system entropy tends to increase with time, or to put it another way, things become more disordered. We know, for example, that the air 'organized' in one half of the universe-room very quickly spreads to fill the whole room, and once there, it will only very rarely gather again in just one part of the room. So if we do find the air gathered in one part of the room, it is statistically much more likely that it got there by a random fluctuation of the air spread around the whole room, than that it was previously in an even smaller space and spread out from there. This is because the chances of the air occupying, say, a quarter of the room (and spreading to half the room from there) are even less than it occupying just half the room (and thence spreading back to the whole room).

The thing is, the same applies to the Universe we live in. It is actually a rather 'orderly' place. We see planets, stars and galaxies. But, thanks to the Second Law of Thermodynamics, it is statistically more likely that the Universe we inhabit was previously less ordered - which is to say more chaotic - than it is now. Given that the entropy of the Universe is increasing, just like the air spreading across our universe-room, it is statistically more likely that the Universe took on the exact the configuration we see now just a moment ago than that it was previously even more organized, in an even lower state of entropy, than it is now. Mathematically, then, it is vastly more likely that our memories are false (but constructed out of the chance configuration of molecules) than that they are real and reliable!

What rescues us from this unpalatable conclusion is gravity. The missing ingredient in our universe-room, which makes the half-full-of-air room always more likely than the quarter-full-of-air room is having enough matter for gravity to pull the air into 'clumps' in different parts of the room. But if your 'room' is a Universe the size of ours, with gravity as a significant force, you can get structures, such as stars, emerging without having to rely on the chance movement of molecules.

However - and here's the trick - the Second Law of Thermodynamics remains the same, and so the increase in entropy still applies. And what this means is that the universe we inhabit today has a higher entropy - in other words, it is more disordered overall - than it was when it began.

And so here's the biggest surprise of all: as Greene himself puts it, "the big bang - the process, event or happening that brought the universe into existence - started off the universe in an extraordinarily special, highly ordered state of low entropy." (p 175)

He concludes:-
"Probabilistically speaking, it is mind-bogglingly more likely that everything we now see in the universe arose from a rare but every-so-often-expectable statistical aberration away from total disorder, rather than having evolved slowly from the even more unlikely, the incredibly more ordered, the astoundingly low-entropy starting point required by the big bang." (p 176)
Don't get me wrong. I am not saying, "And therefore we can prove God exists," any more than Greene is. What I am saying (which he is, too) is that this is astonishingly counter-intuitive and makes us look at the whole Universe, including the process of 'evolution', differently.

We naturally assume that the universe proceeded from chaos (big bang) to order, and that this happened because vast amounts of time made the chance coming-together of ordered things possible. The truth (apparently) is the reverse. The universe started as a vastly-improbable ordered system and that the more time goes by the less likely any order becomes. Yet in the process of moving from order to disorder, from low to high entropy, life and consciousness have emerged.

Surely, then, all of us ought at least to ask, "What kind of universe is this, that begins in such a precise way that produces such an astonishing result?" To quote another song, "I think to myself, 'What a wonderful world.'"

Revd John P Richardson
14 March 2008

(PS I will get around to the second article on Christianity and the law at some time.)

No comments will be posted without a full name and location, see the policy.


  1. Now for the niggling question; is entropy a result of the Adam's fall?


    A. Terry

  2. I think there are serious questions to ask about the 'strong anthropic principle': the notion that in some sense the 'shape' of the universe is determined by our being here.

    First, even from a viewpoint that excludes theology, the existence of consciousness and will is 'embedded' in the universe at the point of the 'Big Bang' just as much as are stars and galaxies. We cannot look at the 'evolution' of stars as and planetary systems as a 'natural' outcome of the increasing entropy of the universe and yet treat the existence of beings like ourselves as somehow an 'accident'. Indeed, it is questionable what the term 'accident' could mean in this context.

    Secondly, if the universe is shaped on a 'strong anthropic principle' which does include theology/spirituality, then the 'fallen' nature of nature is built in, to some extent, from the beginning.

    For myself, I have often questioned the assumption of a 'perfect' world (sans any thistles, sans thorns, etc) which then took on its 'imperfect' characteristics post-Fall. I do, though, accept the idea of the historic Fall.

  3. Could it be thorns, thistles and the like had a different function pre-fall?

    Both of my wife's Grandad's were farmers, 1 a Christian the other an Atheist. The Atheist believed that grops were given to us by Aliens as there is no way they could have evolved, they need so much human attention. If left alone all you get is weeds. The other Grandad will just refer you to Gensis 3.

    Darren Moore