The trail to life

In the last chapter we said that the Big Bang and the appearance of the universe from the vacuum were two very striking facts. Now we want to turn to a third, very striking, impression, which emerges from this long history of the universe: the fate of the universe seems quite fantastic. The destiny of the universe seems mischievously entwined with a lot of disconnected events. Some of these took place unimaginably quickly, such as the burst of activity during the first 10-32 second of inflation, or the sudden intervention of a cosmic domain creating havoc in its path. Others seem rather protracted affairs, such as the lethargic progress that followed the first quarter of an hour, and the launching of the universe on a never-ending expansion.

Key events like these arise from microphysical properties, such as the Heisenberg uncertainty relations, and from processes operating on the largest scale, such as the expansion of space as described by Einstein's equations.

Among the decisive events, some had direct action on the course of the universe and, therefore, on our place within it. The eventual disappearance of matter, through proton decay, would have major consequences for the universe and in particular for us: no matter, no humans.

Relativistic space

Four-dimensional spacetime

The twentieth century has given rise to two great theories in physics: relativity and the quantum theory. They gave mankind a radically different view of the nature of the universe. We have to use these ideas in order to understand more clearly the meaning of the quick look at the universe that we ran through in Chapter 3. Relativity particularly has provided a complete and coherent history of the universe from 0.01 seconds after the Big Bang right through to the present age of 15 billion years. When you see the majestic unfolding of this immensely rich tapestry for the first time it takes your breath away.

In seeking perfection we find that Einstein's general theory of relativity replaces Newton's law. In doing so, it replaces the Newtonian gravitational force with a completely different concept: gravitation results from the curvature of space created by masses located in space. This curvature guides the motion of particles, and makes them follow trajectories that correspond to the orbits of Newton's theory. This establishes the general framework for our investigation.

General relativity is a theory of gravitation which followed the results of the special theory of relativity. Some years earlier Einstein had completed the special theory, which is essentially a questioning and redefinition of the nature of space and time.

Chapters 4 and 5 tackled the relativistic and quantum aspects of the universe, in accordance with the two major theories of the age, general relativity and quantum theory. Even though these have enjoyed much success in explaining numerous experiments, as well as observational data, they both have shortcomings and need a more complete synthesis. Supersymmetry, supergravity and even Grand Unification are promising ways to approach this goal but they lack experimental support, being only at the stage of preliminary outlines. However, the cosmologist Dennis Sciama has made this encouraging remark: ‘It is hard to imagine that everything is wrong or illusory. We are witnessing the beginning of a new and imaginative scenario for understanding the universe’.

In Chapter 4 we played the game of trying to understand the universe, and took some risks. It is fun to launch out on a promising track, avoiding the pitfalls for the unwary and sidestepping the dead ends, in order to see if the chosen route will open up new horizons or lead to an impasse. In any case, to accompany a scientific mind voyaging a slightly dangerous but rational course is an interesting pursuit.

Weighing up the Big Bang

The Big Bang scenario, which has already been discussed in this book, has plenty of positive features.

Some Roman cosmology…

I'm going to use a wonderful text, written in Rome at the end of the reign of Emperor Augustus by the poet Marcus Manilius, to summarise the thousand-year enigmas of the cosmos. The extracts are taken from his poem on astronomy. This is more than two thousand years old and lay forgotten until the tenth century. The first French translation by Pingré was published in Paris in 1786. I know all this not because I am a historian, but because I stumbled across the book by sheer chance on the stand of a bookseller by the Seine. With my love of astronomy, the Seine, and old books I just could not resist such a find. It was my first introduction to the works of Manilius.

Manilius himself was probably not an astronomer. Instead he drew his knowledge from a variety of Greek and Roman authors. The special fascination of his work is that he gives an extensive review of astronomy, and this summary was made at a pivotal moment during the evolution of western philosophy. Astronomy flourished in the millennium before Manilius: the diameter of the Earth had been determined, and the idea that the Earth was isolated in space was taken seriously.

Night, our window on the universe…

The night is our window on the universe. In the daytime the blueness of the sky prevents us from seeing into space. The blue light is caused when the intense sunlight is scattered by oxygen molecules in the upper atmosphere. Beneath this atmospheric layer, which is a few tens of miles deep, the situation is somewhat like looking through net curtains: if a searchlight were illuminating the fabric, it would be impossible to see anything apart from the searchlight itself. By day we can see only the Sun and the Moon (if it has risen), which is so much fainter by comparison that many people think incorrectly that it is invisible during the day. But when we switch off the searchlight, the surrounding landscape can be discerned: the stars, the planets…

If the Earth did not have an atmosphere, the stars would be visible in broad daylight. The dozen Apollo astronauts who landed on the Moon experienced just such a spectacle, despite the dazzle of sunlight. However, things could be worse. The planet Venus is shrouded in a dense atmosphere and the surface pressure is one hundred times that of the Earth's atmosphere. This blanket is so thick that not a single star is visible at night; even in daytime the Sun itself is invisible and only a feeble glimmer of light reaches the surface.

Where has our exploration of the enigma of the universe left us, after all these pages? Clearly, we have encountered facts that are profoundly significant. In terms of spatial dimensions, we have probed the cosmos from the Planck length to quasars and the cosmological horizon. In time we have gone from the Planck time to the Dyson age. We have looked at structures ranging from the trio of quarks lost inside a proton, like three viruses in a volume the size of the Sun, through to the filamentary structure of the universe at large. Our story has embraced particles as subtle as the neutrino and as hypothetical as massive and destructive magnetic monopoles. The recession of the galaxies and the cosmic microwave background are relics of its explosive beginning. Using relativity, with its fusion of space and time, we can show how this Big Bang leads to what I term the grandiose fresco, or the golden moment that started the universe as we know it. As it aged from one second to fifteen billion years, the universe first experienced fifteen minutes of frenetic nuclear activity, followed by a lengthy period of lethargy, lasting a hundred million years when relatively little happened.

This document was originally distributed in 1975 by the Mathematics Department of King's College, University of London, as a technical report. (The research was supported by the Science Research Council.) A brief account of its most novel conclusions was published as Fulling 1976.

It is reproduced here verbatim, except for certain improvements connected with the revolution in scientific typography, and the updating of references to some journal articles that were not yet in print at that time.

Analogous studies of the Klein effect for fermions have since been conducted by Bilodeau 1977 for the neutrino field and by Manogue 1988 for the massive Dirac field. Ambjorn & Wolfram 1983 investigate the Schiff–Snyder–Weinberg scenario further; they present evidence that the reaction of the quantized field on the electric field suffices to suppress the instabilities.

Recent years have seen considerable attention to the implications of strong-field effects (on fermions, primarily) for realistic nuclear physics. I understand that the experimental evidence is still inconclusive. From this literature I will cite only these reviews: Rafelski et al. 1978; Soffel et al. 1982; Greiner et al. 1985.

Abstract

Part One A relativistic scalar field is quantized in a one-dimensional “box” comprising two broad electrostatic potential wells. As the potential difference increases, the phenomena found by Schiff, Snyder, and Weinberg in such a model occur: merging of mode frequencies and disappearance of the vacuum as a discrete state, followed by appearance of complex frequencies and unboundedness below of the total energy.