From time immemorial most tribes and all civilisations have held strong views about the meaning and nature of the universe. The generally held view today is that the universe began about ten billion years ago in what is popularly known as the big bang.
What is meant by this has been excellently described by the astronomer royal, Martin Rees, in Before the Beginning. The book is arranged in short sections, each complete in itself, discussing a clearly explained topic and arriving at a clearly stated conclusion.
Everything turns on the expansion of the universe, which all but a very few extreme dissidents believe to be guaranteed by the observed red shifts of galaxies. Expansion means the following: take a number of moderately distant galaxies to suit yourself and join their centres by straight lines so as to obtain a geometrical figure whose shape depends on how you chose your sample. As time goes along, the scale of this figure will increase, although its shape will remain the same. And if some other set of galaxies had been chosen, leading to a figure of different shape, its scale would increase with time in just the same way. So would the figure obtained by anyone anywhere in the universe.
What happens now if we think backwards in time instead of forwards? Then the scale was less, meaning that galaxies were closer together than they are now. And if the simplest physics is used, a straightforward calculation shows that the shrinkage of scale not only continues progressively back into its past but accelerates. Using the best present-day observations the scale shrinks to nothing at all in 11 billion years, which is where the expression "age of the universe" comes from.
And then what? It is the merit of the cosmology of the past two decades, described in detail in Before the Beginning, that a serious attempt has been made to answer this question. According to current thinking, there is a drastic change in the laws of physics. This new physics is supposed to work only at energies vastly higher than anything known in the laboratory, billions of times higher. There are no particles of matter or radiation in the ordinary sense. The universe in the first instance when space and time exist is supposed to have started with an immense store of energy in the form of a potential. Rather as a weight at the top of a building can gain energy by falling to the ground, so this potential is thought to have led to the emergence of energy, by decaying into a field in a process that big-bang cosmologists refer to as "inflation".
So far, it is possible to follow the mathematics in a reasonably precise way. But then comes a retreat into words and analogies. The idea of a "phase change" is invoked, whereby the field derived from the initially assumed potential is taken to jump suddenly into particles, which then undergo a sequence of transformations from forms that are unknown into, ultimately, forms that are known. Thereafter, physics is supposed to have followed along lines known from laboratory experiments.
The last third of Before the Beginning is concerned with the even more sensitive question: where did the initial moment in such a scenario come from? Was there a kind of pre-universe that gave rise to it? The concept of there being a larger universe with our particular form of beginning, as merely one among an infinite range of possibilities, is extensively discussed. Perhaps even the laws of physics as they have emerged in our own case could have been different in other cases? This would explain why in our universe the laws seem to have properties that are unexpectedly favourable to the emergence of life, otherwise we could not have been here to observe and think about the universe at all; a form of argument that goes by the name of the anthropic principle and on which readers will find much to please them in this book's last two chapters.
It is safe to say that when asked to justify the above scenario, supporters of big-bang cosmology respond rather uniformly by citing two forms of possible relics remaining from quite a late stage of the scenario, the stage after ordinary matter and radiation have emerged. One is the so-called cosmic microwave background and the other is the observed astrophysical abundances of three light nuclei, deuterium, helium and lithium, which are thought to come from the early universe instead of from stars, the assumed source of all other nuclei. Both are good arguments, but the problem is that they are both 30 years old. Nothing to equal them has appeared in almost a third of a century, despite much effort. Moreover, the big-bang theory was designed around them. They were built into the theory from the beginning. I have always thought it a good plan to discount the initial reasons one may have for considering a theory and judge it in the light of subsequent performance. On subsequent performance the position is much weaker than it is usually claimed to be.
When the two arguments are taken together, they lead to the conclusion that most of the material in today's universe must be of an unknown form, often referred to as "missing mass". Missing mass may eventually be found and identified. But it has been looked for now for almost two decades, without success. Furthermore, there are details of the abundances of the fossil nuclei that do not seem to be quite right, despite a great deal of effort having been expended over them. Most cosmologists seem ready, however, to ignore such problems.
Now to what I see as the crucial issue, that big-bang cosmology is back to front in its logic. I have reached the cynical position where I doubt the ability of humans to think correctly unless they are constantly guided by experiment and observation. Standard scientific procedure starts from a known state of affairs whose reality is guaranteed by observation. Theories are then used to argue forwards in time to a conclusion which can again be tested by observation. When the correspondence between prediction and observation is good the theory used to make the prediction is said to be good. But in big-bang cosmology we do not start from a known position. The initial position is entirely conjectural. And it is logically not possible to use present-day observations to test the theory and to infer what the initial situation must have been.
What is done, therefore, is to assume that the theory is correct. The aim then becomes to infer by backwards logic how things must have been in the past, especially how things were in the early moments of the universe. Instead of this being a proof of the theory, it is a protestation of faith. In effect, the theory becomes a religious doctrine.
Once faith becomes an important component in the thinking of supporters of the big bang, several observational discrepancies can be brushed aside, and confidence can be widely expressed that everything will right itself in the fullness of time. Such an attitude is the one mostly taken towards the considerable discrepancy between the age of about 11 billion years given for the universe and of about 17 billion years for old stars in our galaxy. Doubtless these estimates will shift as new observations are made. At all events, this discrepancy has been around now for upwards of 50 years and it has not yet gone away.
On one point, however, everybody seems to agree. Physics must be modified in such a way as to admit the appearance of matter and radiation. In big-bang cosmology the modification of physics occurs in the very earliest moments when a potential supplied to the universe at the big bang leads to a field that leads to the origin of matter and radiation, the energy of the latter being supplied to the universe at its first moment.
Alternatively, the positive energy of matter and radiation can be balanced by the simultaneous creation of a field with negative energy. Such a field was considered almost 50 years ago. Except for the differences of sign, negative instead of positive, the mathematical structure of the theory was very similar to the version involving a big bang. If, in this alternative version, we go backwards in time in the modern universe, in the presence of such a field as required in compensation for the known matter and radiation in the modern universe, it turns out that the universe does not collapse ever faster towards a big bang. The field slows the collapse and eventually halts it. Going back still further, the universe expands and contracts in a sequence of oscillations, which is an entirely different picture from the big bang.
What has the modern generation of very large telescopes revealed about these two versions of the beginning of the universe? Do the telescopes reveal, as they look back into the past, a universe collapsing more and more rapidly towards a catastrophic state? Or do they reveal a universe slowing down towards one of the minima of a series of oscillations?
The situation is that no state of the universe has been found where the scale is less than about one-quarter of the present scale. This is consistent with the minimum scale in a series of oscillations being about a quarter of the present scale - whereas, according to the theory of the big bang, much smaller scales would be expected. But the fact is that, despite the great advance in modern telescopic power, no evidence has yet been found to show that galaxies have ever been a great deal closer together than they are at present - a few times closer, but not many times closer.
At the end of the day the above differences in points of view may be a question of age. Martin Rees belongs to a younger generation that is both happy and anxious to set out on a journey into the unknown, as indeed he shows so effectively in his later chapters. Most readers will probably be better pleased to follow the intrepid explorer than the stay-at-home diehard. But they should not be altogether surprised if, in doing so, they fall off the edge of the world.
Sir Fred Hoyle was formerly Plumian professor of astronomy, University of Cambridge.
Before the Beginning: Our Universe and Others
Author - Martin Rees
ISBN - 0 684 81682 2
Publisher - Simon & Schuster
Price - £16.99
Pages - 282