So how did the universe begin? 'Begin' is the wrong word. Nonetheless, there is good evidence that the age of the universe is about 15 billion years,* so nothing — not space, not time — existed before some instant of time roughly 15 billion years ago. See how our narrativium-powered semantics confuses us. This does not mean that if you went back 15 billion and one years, you would find nothing. It means that you cannot go back 15 billion and one years. That description makes no sense. It refers to a time before time began, which is logically incoherent, let alone physically so.
This is not a new point. Saint Augustine made it very clearly in his Confessions of about 400, when he said: '… if there was no time before heaven and earth were created, how can anyone ask what you [God] were doing “then”? If there was no time, there was no “then” '.
Some have gone to greater extremes. In The End of Time, Julian Barbour argues that time does not exist. In his view, the 'real' laws of physics specify a static universe of timeless 'nows'. He argues that time is not a physical dimension in the way that space is. The apparent flow of time is an illusion, created because the collection of nows that corresponds to a human being makes that human experience its world as if it were an ordered series of events, happening one after the other. Apparent gaps of 'duration' between successive events are merely blanks where no 'now' exists. Thief of Time explores some remarkably similar issues from the Discworld viewpoint. But for this book, we will take a conventional attitude towards time, and consider it to be a real part of physics.
Cosmologists are pretty sure that it all began like this. The universe came into being as a tiny speck of space and time. The amount of space inside this tiny speck grew rapidly, and time began to elapse so that 'rapidly' actually had a meaning. Everything that there is, today, right out into the furthest depths of space, stems from that astonishing 'beginning'. Colloquially, the event is known as the Big Bang. The name reflects several features of the event — for example, that tiny speck of space/time was enormously hot, and grew in size exceedingly rapidly. It was like a huge explosion, but there was no stick of cosmic dynamite, sitting there in no-space with its non-material fuse burning away as some kind of pre-time pseudo-clock counted down the seconds to detonation. What exploded was — nothing. Space, time, and matter are the products of that explosion: they played no part in its cause. Indeed, in a very real sense, it had no cause.
The evidence in favour of the Big Bang is twofold. The first item is the discovery that the universe is expanding. The second is that 'echoes' from the Big Bang can still be detected today. The possibility that the universe might be getting bigger first appeared in mathematical solutions to equations formulated by Albert Einstein. Einstein viewed spacetime as being 'curved'. A body moving through curved spacetime deviates from its normal straight line path, much as a marble rolling on a curved surface does. This deviation can be interpreted as a 'force' — something that pulls the body away from that ideal straight line. Actually there is no pull: just a bend in spacetime, causing a bend in the body's path. But it looks as if there's a pull. Indeed this apparent pull is what Newton called 'gravity', back in the days when people thought it really did pull bodies together. Anyway, Einstein wrote down some equations for how such a bendy universe ought to behave. They were very difficult equations to solve, but after making some extremely strong assumptions — basically that at any instant of time space is a sphere — mathematical physicists worked out few answers. And this tiny, very special list of solutions, the only ones their feeble methods could find, told them three things that the universe could do. It could stay the same size forever; it could collapse down to a single point; or it could start from a single point and grow in size without limit.
We now know that there are many other solutions to Einstein's equations, leading to all sorts of bizarre behaviour, but back in the days when today's paradigm was being set, these solutions were the only ones anybody knew. So they assumed that the universe must behave according to one or other of those three solutions. Science was subliminally prepared either for continuous creation (the universe is always the same) or for the Big Bang. The Big Crunch, in which the universe shrinks to an infinitely dense, infinitely hot point, lacked psychological appeal.
Enter Edwin Hubble, an American astronomer. Hubble was observing distant stars, and he made a curious discovery. The further away the stars were, the faster they were moving. He knew this for distinctly indirect — but scientifically impeccable — reasons. Stars emit light, and light has many different colours, including 'colours' that the human eye is unable to see, colours like infra-red, ultra-violet, radio, x-ray ... Light is an electromagnetic wave, and there is one 'colour' for each possible wavelength of light — the distance from one electromagnetic peak to the next. For red light, this distance is 2.8 hundred thousandths of an inch (0.7 millionths of a metre).
Hubble noticed that something funny was happening to the light emitted by stars: the colours were shifting in the red direction. The further away a star was, the bigger the shift. He interpreted this 'red shift' as a sign that the stars are moving away from us, because there is a similar shift for sound, known as the 'Doppler effect', and it's caused by the source of the sound moving. So the further away the stars are, the faster they're travelling. This means that the stars aren't just moving away from us — they're moving away from each other, like a flock of birds dispersing in all directions.
The universe, said Hubble, is expanding.
Not expanding into anything, of course. It's just that the space inside the universe is growing.* That made the physicists' ears prick up, because it fitted exactly one of their three scenarios for changes in the size of the universe: stay the same, grow, collapse. They 'knew' it had to be one of the three, but which? Now they knew that, too. If we accept that the universe is growing we can work out where it came from by running time backwards, and this time-reversed universe collapses back to a single point. Putting time the right way round again, it must all have grown from a single point — the Big Bang. By estimating the rate of expansion of the universe we can work out that the Big Bang happened about 15 billion years ago.
There is further evidence in the Big Bang's favour: it left 'echoes'. The Big Bang produces vast amounts of radiation, which spreads through the universe. Because the universe is spherical, the radiation eventually comes back on itself like a round-the-world traveller. Over billions of years, the remnants of the Big Bang's radiation smeared out into the 'cosmic background', a kind of low-level simmering of radiant energy across the sky, the light analogue of a reverberating echo of sound. It is as if God shouted 'Hello!' at the instant of creation and we can still hear a faint 'elloelloelloelloello ...' from the distant mountains. On Discworld this is exactly the case, and the Listening Monks in their remote temples spend their whole lives straining to pick out from the sounds of the universe the faint echoes of the Words that set it in motion.
According to the details of the Big Bang, the cosmic background radiation should have a 'temperature' (the analogue of loudness) of about 3° Kelvin (0° Kelvin is the coldest anything can get, equivalent to about -273° Celsius). Astronomers can measure the temperature of the cosmic background radiation, and they do indeed get 3° Kelvin. The Big Bang isn't just a wild speculation. Not so long ago, most scientists didn't want to believe it, and they only changed their minds because of Hubble's evidence for the expansion of the universe, and that impressively accurate figure of 3° Kelvin for the temperature of the cosmic background radiation.
It was, indeed, a very loud, and hot, bang.
We are ambivalent, then, about beginnings — their 'creation myth' aspect appeals to our sense of narrative imperative, but we sometimes find the 'first it wasn't, then it was' lie-to-children unpalatable. We have even more trouble with becomings. Our minds attach labels to things in the surrounding world, and we interpret those labels as discontinuities. If things have different labels, then we expect there to be a clear line of demarcation between them. The
universe, however, runs on processes rather than things, and a process starts as one thing and becomes another without ever crossing a clear boundary. Worse, if there is some apparent boundary, we are likely to point to it and shout 'that's it!' just because we can't see anything else worth getting agitated about.
How many times have you been in a discussion in which somebody says 'We have to decide where to draw the line'? For instance, most people seem to accept that in general terms women should be permitted abortions during the earliest stages of pregnancy but not during the very late stages. 'Where you draw the line', though, is hotly debated, and of course some people wish to draw it at one extreme or the other. There are similar debates about exactly when a developing embryo becomes a person, with legal and moral rights. Is it at conception? When the brain first forms? At birth? Or was it always a potential person, even when it 'existed' as one egg and one sperm?
The 'draw a line' philosophy offers a substantial political advantage to people with hidden agendas. The method for getting what you want is first to draw the line somewhere that nobody would object to, and then gradually move it to where you really want it, arguing continuity all the way. For example, having agreed that killing a child is murder, the line labelled 'murder' is then slid back to the instant of conception; having agreed that people should be allowed to read whichever newspaper they like, you end up supporting the right to put the recipe for nerve gas on the Internet.
If we were less obsessed with labels and discontinuity, it would be much easier to recognize that the problem here is not where to draw the line: it is that the image of drawing a line is inappropriate. There is no sharp line, only shades of grey that merge unnoticed into one another, despite which, one end is manifestly white and the other is equally clearly black. An embryo is not a person, but as it develops it gradually becomes one. There is no magic moment at which it switches from non-person to person — instead, it merges continuously from one into the other. Unfortunately our legal system operates in rigid black-and-white terms — legal or illegal, no shades of grey — and this causes a mismatch, reinforced by our use of words as labels. A kind of triage might be better: this end of the spectrum is legal, that end of the spectrum is illegal, and in between is a grey area which we do our best to avoid if we possibly can. If we can't avoid it, we can at least adjust the degree of criminality and the appropriate penalty according to whereabouts in the spectrum the activity seems to lie.
Even such obviously black-and-white distinctions as alive/dead or male/female turn out, on close examination, to be more like a continuous merging than a sharp discontinuity. Pork sausages from the butcher's contain many live pig cells. With today's techniques you might even clone an adult pig from one. A person's brain can have ceased to function but their body, with medical assistance, can keep going. There are at least a dozen different combinations of sex chromosomes in humans, of which only XX represents the traditional female and XY the traditional male.
Although the Big Bang is a scientific story about a beginning, it also raises important questions about becomings. The Big Bang theory is a beautiful bit of science — very nearly consistent with the picture we now have of the atomic and the subatomic world, with its diverse kinds of atom, their protons and neutrons, their clouds of electrons, and the more exotic particles that we see when cosmic rays hit our atmosphere or when we insult the more familiar particles by slamming them together very hard.
Physicists have now found, or perhaps invented, the allegedly 'ultimate' constituents of these familiar particles (more exotic things known as quarks, gluons ... at least the names are becoming familiar).
The Holy Grail of particle physics has been to find the 'Higgs boson', which — if it exists — explains why the other particles have mass. In the 1960s Peter Higgs suggested that space is filled with a kind of quantum treacle called the Higgs field. He suggested that this field would exert a force on particle through the medium of the Higgs boson, and that force would be observed as mass. For 30 years, physicists have constructed ever-larger and more energetic particle accelerators in the search for this elusive particle, such as the new Large Hadron Collider, due to start up in 2007.
Late in 2001, scientists analysing data from its predecessor, the Large Electron Positron Collider (LEP), announced that the Higgs boson probably doesn’t exist. If it does, then it has to be even more massive than everyone expected, and the LEP scientists are sceptical. No good substitute for Higgs’ theory exists, not even the fashionable concept of 'supersymmetry' which pairs every known particle with a more massive partner. Supersymmetry predicts several Higgs particles, which masses well inside the range where the LEP data prove no such thing exists. Some physicists still hope that the Higgs boson will show up when the new accelerator comes on line — but if it doesn’t particle physics will have to rethink the entire basis of their subject.
Whatever happens to the Higgs boson, they’re already starting to wonder whether that are more layers of reality further down, particles more 'ultimate' still.
Turtles all the way down?
Does physics go all the way down, or does it stop at some level? If it stops, is that the Ultimate Secret, or just a point beyond which the physicists' way of thinking fails?
The conceptual problem here is difficult because the universe is a becoming — a process — and we want to think of it as a thing. We don't only find it puzzling that the universe was so different back then, that particles behaved differently, that the universe then became the universe now, and will perhaps eventually cease expanding and collapse back to a point in a Big Crunch. We are familiar with babies becoming children becoming adults, but these processes always surprise us — we like things to keep the same character, so 'becoming' is difficult for our minds to handle.
There is another element of the first moments of our universe that is even more difficult to think about. Where did the Laws come from? Why are there such things as protons and electrons, quarks and gluons? We usually separate processes into two conceptually distinct causal chunks: the initial conditions, and the rules by which they are transformed as time passes. For the solar system, for instance, the initial conditions are the positions and speeds of the planets at some chosen instant of time; the rules are the laws of gravitation and motion, which tell us how those positions and speeds will change thereafter. But for the beginning of the universe, the initial conditions seem not to be there at all. Even there isn't there! So it seems that it's all done by rules. Where did the rules come from? Did they have to be invented? Or were they just sitting in some unimaginable timeless pseudo-existence, waiting to be called up? Or did they uncurl in the early moments of the universe, as Something appeared — so that the universe invented its own rules along with space and time?
Two recent books by top-ranking scientists explore how rules could be 'invented'. The most recent is Stuart Kauffman's 2000 Investigations. This is mainly aimed at biology and economics, but it begins with rules of physics. In a new answer to the old question 'what is life?', Kauffman defines a lifeform to be an 'autonomous agent' — any entity or system that can redirect energy and reproduce. 'Autonomous' here means that such a system makes up its own rules, determines its own behaviour. Such lifeforms need not be at all conventional. For example, the quantum-mechanical vacuum is a seething mass of particles and antiparticles, being created and annihilated in amazingly complicated ways. A vacuum has more than enough complexity to organise itself into an autonomous agent. If it did, then quantum mechanics would be able to make up its own rules.
The other noteworthy book on this topic is Lee Smolin's 1997 The Life of the Cosmos, which asks: can universes evolve? A remarkable feature of our universe is the presence of Black Holes. These are regions of space-time that contain so much mass that light (and matter) cannot get out; they are formed by the collapse of massive stars. It used to be thought that Black Holes are rare, but now they seem to be showing up all over the place, in particular at the cores of most galaxies. Theoretical
work shows that the constants of our universe are unusually good for making Black Holes.
Why? Smolin argues that each Black Hole in our universe is in effect a doorway to an adjacent universe, but because nothing can come out of a Black Hole we cannot know what is on the far side of that door. In particular, the adjacent universe might have different fundamental constants compared to ours. So universes could 'breed' by budding off baby universes through Black Holes, and natural selection would favour those that had the most offspring — whose constants would automatically be unusually good for making Black Holes. So maybe we live in one of those babies.
There are some difficulties with this theory. In particular, how would selection work? How can universes compete? But it's an interesting, if rather wild, idea. And it offers a concrete proposal about how a universe can 'make up' its laws: some, at least, could be imposed upon it at birth.
The Big Bang, then, may have done more than just bringing space and time into being. It may also have brought 'the' rules of physics — the ones that now apply to our world — into being. During the becoming of its first moments, our universe kept changing its state, changing the rules it accessed. In this respect it was rather like a flame, which changes its composition according to its own dynamics and the things that it is burning. Flames are all more or less the same shape, but they don't inherit that shape from a 'parent'. When you set light to a piece of paper, the flame builds itself from scratch using the rules of the outside universe.
In the opening instants of the universe, it wasn't just substances, temperatures and sizes that changed. The rules by which they changed also changed. We don't like to think this way: we want immutable laws, the same always. So we look for 'deeper' laws to govern how the rules changed. Possibly the universe is 'really' governed by these deeper laws. But perhaps it just makes up its own rules as it goes along.
The Science of Discworld Page 6