The simple truth of evolution by natural selection was staring all those clever Greeks, all those brilliant mathematicians and philosophers before Darwin, in the face. But none of them had the intellectual courage to defy what seemed obvious. They overlooked the wonderful bottom-up explanation for what seemed, wrongly, to have top-down creation written all over it. The fact that the true explanation is so blindingly simple meant that it took even more courage to pursue it and work it out in detail. Natural selection evaded all those brilliant minds precisely because it is so simple. Too simple, one might have thought, to do the heavy lifting of explaining the whole of life in all its complexity and diversity.
We now know – the evidence brooks no alternative – that Darwin was right. There are a few details left to clean up. For example, we still don’t know – yet – exactly how the process of evolution got started, some four billion years ago. But the main mystery of life – how did it come to be so complex, so diverse and so beautifully ‘designed’ – is solved. And my final point in this book is that Darwin’s and Galileo’s and Wegener’s intellectual courage should inspire us to go further, in the future. All those examples of apparently ridiculous propositions turning out to be true should give us new courage when we face the remaining big puzzles of existence. How did the universe itself begin? And where do the laws that govern it come from?
A word of caution, by the way, before we go on. Galileo, Darwin and Wegener proposed daringly surprising ideas and they were right. Plenty of people propose daringly surprising ideas and are wrong, crazy wrong. Courage isn’t enough. You have to go on and prove your idea right.
Our view of the universe has swelled over the centuries. And the universe itself is literally swelling as the seconds tick by. Once, people thought the Earth was pretty much all there was, with the sun and moon circling overhead, and the stars little peepholes through a hemispherical shell into heaven. Now we know the universe is large beyond all contemplation. But we also know that, once upon a time, the universe was small beyond all contemplation. And we know when that was. It was, according to current estimates, about 13.8 billion years ago.
The expanding universe was a twentieth-century discovery. There are people alive in the world today – my 102-year-old mother is one – who were born into a universe consisting of a single galaxy. Now she lives in a universe of 100 billion galaxies rushing away from each other as space itself expands. That’s not an accurate way to put it, of course. She and Shakespeare and Galileo and Archimedes and the dinosaurs were all born into the same expanding universe. But when my mother was born, in 1916, nobody knew about anything other than the one galaxy we call the Milky Way. That was the universe. In Galileo’s time nobody even knew about that. Scientific truths are true even if there’s nobody around to know about them; were true before humans appeared; will be true after we are extinct. That’s an important point that evades many otherwise clever thinkers.
It is likely that even our expanding universe of 100 billion galaxies is not the only universe. Many scientists think – with good reason – that there are billions of universes like ours. On this view, ours is just one universe in a multiverse of billions of universes. We’ll return to that idea in a moment.
Physicists today have a pretty good idea of what happened in the very early history of our universe. By ‘very early’ I mean back in the first tiny fraction of a second after the birth of the universe. And not only after the birth of the universe: after the birth of time itself. What can that possibly mean: ‘the birth of time’? What happened before that? Physicists tell us we are not allowed to ask that question. It’s like (or so they say) asking what is north of the North Pole. But that prohibition may apply only to our universe. That’s if our universe is indeed one of billions in a multiverse.
God-worshippers nowadays (the educated ones, anyway) have given up on the living world as evidence of a creator. This is because they now understand that, where life is concerned, Darwinian evolution provides a full explanation. They’ve switched, instead, to other kinds of argument. With some desperation – or so it seems to me – they have turned their attention to other ‘gaps’. Especially cosmology and the origin of everything, including the fundamental laws and constants of physics.
I need to explain what’s meant by the fundamental constants of physics. There are some numbers that you can measure. Like the number of protons in a silver atom. There are other numbers that you can estimate. Like the number of water molecules in a glassful. And there are other numbers whose value is mathematically necessary. Like π (pi), the ratio of the circumference of any circle to its diameter – and π enters into mathematics in many other fascinating ways. But there are some numbers that physicists just accept without knowing why they have the values that they do. These are called the fundamental constants of physics.
An example is the gravitational constant, symbolized by the letter G. You’ll remember we learned from Newton that all objects in the universe, such as planets, cannonballs and feathers, are attracted to each other by gravity. The more distant the objects are from each other, the weaker the attraction is (it’s inversely proportional to the distance multiplied by itself). And the more massive the two objects, the stronger the attraction between them (it’s proportional to the two masses multiplied together). But to get the actual force of attraction itself you finally have to multiply by another number, G, the gravitational constant. Physicists believe G is the same all over the universe, but they don’t know why it has the value it does. It’s possible to imagine an alternative universe with a different value of G. And if G were even slightly different, the universe would be very, very different.
If G were smaller than it is, gravity would have been too weak to gather matter into clumps. There’d be no galaxies, no stars, no chemistry, no planets, no evolution and no life. If G had been just a little bit bigger than it is, stars couldn’t exist as we know them and they wouldn’t behave as they do. They’d all collapse under their own gravity and perhaps become black holes. No stars, no planets, no evolution, no life.
G is just one of the physical constants. Others include c, the speed of light; and the ‘strong force’, which binds the atomic nucleus together. There are more than a dozen of these constants. Each of them has a value which is known but which is not (so far) explained. And in all cases you can say that, if their value were different, the universe as we know it could not exist.
This has led some theists to hope that God must be lurking somewhere behind the scenes. It’s as if the value of each fundamental constant had been set by a knob that you might twiddle, like the tuning knob on an old-fashioned radio set. All the knobs had to be correctly tuned in order for the universe as we know it to exist – and therefore for us to exist. The temptation is to think that a creative intelligence – a god of some kind, a divine knob-twiddler – did the fine tuning.
It’s a temptation that should be sternly resisted. For reasons we’ve seen in earlier chapters. The fine-tuning of all those knobs might seem improbable, because there are so many other positions each tuning knob could be in. But, however improbable that fine-tuned precision may seem, any god capable of doing the precision tuning must be at least as improbable. How else would he know how to tune them? Importing a god into the reasoning doesn’t solve the problem. It simply pushes it one stage back. It’s a crashingly obvious non-explanation.
The problem Darwin solved, namely the problem of the massive improbability of life, was the big one. Before Darwin came along, the recurring phrase from the first part of this chapter, ‘You cannot be serious!’, would have hit home with immense force for anyone daring to question the divine creation of life. Perhaps with more force than for any other case. All that complexity, the speed and grace of a swallow, the fine-tuned flight surfaces of an albatross or a vulture, the bewildering intricacy of a brain or a retina, to say nothing of every one of the quadrillion cells of an elephant, the shimmering beauty of a peacock or a hummingbird �
� all that came about through the unaided, undirected, unsupervised laws of physics?
Explaining something so comparatively simple as the origin of the laws and constants of physics themselves should be a doddle by comparison. Admittedly we haven’t solved that problem yet. But the success of Darwin and his successors in solving the bigger problem of life, and its fine-tuning to the needs of survival, should give us courage. Especially when we add to Darwin all the other spectacular successes of science. We’re familiar with the list of such successes. Without antibiotics, vaccination and scientific surgery, many of us would be dead. Without scientific engineering, few of us would have travelled more than a few miles from where we were born. Without scientific agriculture, most of us would starve. Here, though, I want to pick out and focus on just one spectacular piece of science, one connected with the deep question we are concerned with – how did the universe come to be the way it is?
Cosmologists, working around the world and feeding constructively on each other’s findings, have built up a detailed theory of what happened after the Big Bang. But how would you test such a theory? You’d need to set up ‘initial conditions’ – meaning the way you think things were immediately after the Big Bang. Then use the theory to deduce how things ought to be today, if your theory is correct. In other words, use your theory to predict the present from the distant past. Then look at the way things actually are to see if your prediction was correct.
You might think you could use mathematical proofs to deduce your prediction. Unfortunately the details are far too complicated for that. On top of the gravitational forces, there are billions and billions of tiny local interactions, for example in the swirling clouds of gas and dust. Such complexity can only be handled by constructing a ‘model’ in a computer and seeing what happens when you run it. Rather like Craig Reynolds and his ‘Boids’ model, which we looked at in Chapter 10. But much more elaborate. And when I said ‘a computer’, that’s just shorthand: a single computer, however big, is nowhere near big enough to simulate the growth of the universe, the calculation is so huge. The most advanced simulation so far is called Illustris, and it needed not one computer but 8,192 computer processors running in parallel. And they weren’t just ordinary computers, they were supercomputers. The Illustris simulation begins not at the Big Bang itself but three hundred thousand years later (a very short time compared to the subsequent 13.8 billion years). Even all those supercomputers couldn’t simulate every last detail of every atom. But it’s fascinating, nevertheless, to compare the predicted shape of today’s universe with the actual reality.
Take a look at this page, which contains a sort of joke. There is a top–bottom split in the picture. One half is the real universe, the famous Hubble Deep Field photograph, taken by the Hubble orbiting telescope in 1995. The other half is the universe as predicted by Illustris. Can you tell which is which? I can’t.
Isn’t science wonderful? If you think you’ve found a gap in our understanding, which you hope might be filled by God, my advice is: ‘Look back through history and never bet against science.’
The Illustris simulation, as I said, begins three hundred thousand years after the Big Bang. Let’s now go back further, to the origin of the cosmos itself, to the fundamental constants and the ‘fine-tuning’ argument – all that twiddling to get the knobs in just the right positions. Let’s look again at the problem. Beginning with an interesting idea called the anthropic principle.
Anthropos is Greek for ‘human’. Hence words like ‘anthropology’. We humans exist. We know we exist because here we are, thinking about our own existence. So, the universe we inhabit has to be the kind of universe that is capable of giving rise to us. And the planet we live on has to have the right conditions to give rise to us. It’s no accident that we are surrounded by green plants. Any planet lacking green plants (or their equivalent) could not give rise to beings capable of thinking about their own existence. We need green plants as our ultimate food source. It’s no accident that we see stars in our sky. A universe without stars would be a universe without any chemical elements heavier than hydrogen and helium. And a universe with only hydrogen and helium would not be rich enough in chemicals to generate the evolution of life. The anthropic principle is almost too obvious to need stating. But it’s still important.
Life as we know it needs liquid water. Water exists as a liquid in only a narrow band of temperatures. Too cold and it’s solid ice. Too hot and it’s gassy vapour. Our planet happens to be just the right distance from our sun, so water can be liquid. Most planets in the universe are either too far from their star (like Pluto – and yes, I know Pluto isn’t classified as a planet any more, but the point remains) or too close to it (like Mercury). Every star has a ‘Goldilocks Zone’ (not too hot and not too cold but, like Baby Bear’s porridge, ‘just right’). Earth is in the sun’s Goldilocks Zone. Mercury and Pluto, in their two opposite ways, are not. But of course, says the anthropic principle, Earth has to be in the Goldilocks Zone because we exist. And we couldn’t exist unless our planet was in the Goldilocks Zone.
Now, what goes for planets would also go for universes. As I’ve already mentioned, physicists have good reason to suspect that our universe is one of many universes in a ‘multiverse’. The multiverse follows – at least according to some interpretations – from the theory called ‘inflation’, which is accepted by most cosmologists today although it is more ‘You cannot be serious’ than anything else in science. And there’s no reason to suppose that all the billions of universes in the multiverse have the same laws and fundamental constants. The tuning of G, the gravitational constant, could be all over the dial in different universes. It could be that only a small number of universes have their G tuned to the ‘sweet spot’. Only a minority of universes are ‘Goldilocks universes’, whose laws and constants happen to be ‘just right’ for the eventual evolution of life. And of course (here’s the anthropic principle again), we have to be in one of that minority of universes. Our very existence determines that our universe has to be a Goldilocks universe. One friendly Goldilocks universe among possibly billions of unfriendly parallel universes.
You cannot be serious!
It’s too early to follow up with But it’s true. Physicists need to do more work on the problem. What we can say is that it’s looking promising. What’s more – and this is the main point of my final chapter – the bold step into the frightening void of what seems improbable has turned out right so often in the history of science. I think we should take our courage in both hands, grow up and give up on all gods. Don’t you?
*Newton was a complicated mixture of contradictions. A superbly rational scientist, he wasted much of his life on a fool’s errand to change base metals into gold. And much of the rest of his life on other fool’s errands such as analysing the Bible for the significance of numbers mentioned there. By the way – not that it has any bearing on his cleverness – he wasn’t a very nice man, unlike Darwin. He treated his rival Robert Hooke badly, although the jealousy, you might think, should have run the other way. As against that, when his dog Diamond upset a lamp and burned some important papers Newton had been working on, he didn’t lose his temper but simply exclaimed, ‘Oh, Diamond, Diamond, thou little knowest the mischief thou hast done!’ That, at least, is how a well-known story goes. Some historians claim it never happened. In which case it’s yet another good example, to add to those of Chapter 3, of how myths get started.
For William
And all young people when they’re old enough to decide for themselves
1 How do religions start? Some are so recent, we can actually watch them emerge. On the island of Tanna in the South Pacific, Prince Philip has been revered as a deity since he visited nearly 50 years ago. Equally young are the cargo cults of several Pacific islands. If new religions can spring up so suddenly and rapidly in our own time, just imagine the scope for distorted legends to grow in the many centuries since the major religi
ons of the world began. (See Chapter 3.)
2 Speed written all over them. Did God design cheetahs to catch gazelles at the same time as he designed gazelles to escape? (See Chapter 7.)
3 The chameleon’s tongue is a beautiful natural harpoon. Note the hyoid bone inside the tubular tongue, which plays a central role in the harpoon’s explosive speed. Elegant ‘design’. Or is it? (See Chapter 7.)
Can you see the octopus (4, left)? No, and nor could the photographer. It suddenly materialized, ghostly white (5, right).
How does a male squid (6) go white to scare away rivals while staying brown to reassure a female? Easy. Go two-tone.
Was the flounder (7) designed by God? More likely designed by Picasso! In fact, the curious distortion of the head has evolutionary history to blame. No designer would ever have chosen this way to make a flatfish. (See Chapter 7.)
8 Naturally selected camouflage, every last detail honed to perfection by the sharp eyes of predators. You can see why people were tempted to credit the hand of God. (See Chapter 7.)
9 Look what selection can do. If (artificial) selection takes only 30 centuries to transform the wild plant Brassica oleracea (top left) into Brussels sprouts, cauliflower, cabbage and Romanesco (not to mention broccoli, curly kale, kohlrabi etc.), just think what (natural) selection could do in the 3 million centuries since our ancestors were fish. (See Chapter 8.)
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