A Brief History of Time: From the Big Bang to Black Holes by Stephen Hawking (1988)

The whole history of science has been the gradual realisation that events do not happen in an arbitrary manner, but that they reflect a certain underlying order. (p.122)

This book was a publishing phenomenon when it was published in 1988. Nobody thought a book of abstruse musings about obscure theories of cosmology would sell, but it became a worldwide bestseller, selling more than 10 million copies in 20 years. It was on the London Sunday Times bestseller list for more than five years and was translated into 35 languages by 2001. So successful that Hawking went on to write seven more science books on his own, and co-author a further five.

Accessible As soon as you start reading you realise why. From the start is it written in a clear accessible way and you are soon won over to the frank, sensible, engaging tone of the author. He tells us he is going to explain things in the simplest way possible, with an absolute minimum of maths or equations (in fact, the book famously includes only one equation E = mc²).

Candour He repeatedly tells us that he’s going to explain things in the simplest possible way, and the atmosphere is lightened when Hawking – by common consent one of the great brains of our time – confesses that he has difficulty with this or that aspect of his chosen subject. (‘It is impossible to imagine a four-dimensional space. I personally find it hard enough to visualise three-dimensional space!’) We are not alone in finding it difficult!

Historical easing Also, like most of the cosmology books I’ve read, it takes a deeply historical view of the subject. He doesn’t drop you into the present state of knowledge with its many accompanying debates i.e. at the deep end. Instead he takes you back to the Greeks and slowly, slowly introduces us to their early ideas, showing why they thought what they thought, and how the ideas were slowly disproved or superseded.

A feel for scientific change So, without the reader being consciously aware of the fact, Hawking accustoms us to the basis of scientific enquiry, the fundamental idea that knowledge changes, and from two causes: from new objective observations, often the result of new technologies (like the invention of the telescope which enabled Galileo to make his observations) but more often from new ideas and theories being worked out, published and debated.

Hawking’s own contributions There’s also the non-trivial fact that, from the mid-1960s onwards, Hawking himself has made a steadily growing contribution to some of the fields he’s describing. At these points in the story, it ceases to be an objective history and turns into a first-person account of the problems as he saw them, and how he overcame them to develop new theories. It is quite exciting to look over his shoulder as he explains how and why he came up with the new ideas that made him famous. There are also hints that he might have trodden on a few people’s toes in the process, for those who like their science gossipy.

Thus it is that Hawking starts nice and slow with the ancient Greeks, with Aristotle and Ptolemy and diagrams showing the sun and other planets orbiting round the earth. Then we are introduced to Copernicus, who first suggested the planets orbit round the sun, and so on. With baby steps he takes you through the 19th century idea of the heat death of the universe, on to the discovery of the structure of the atom at the turn of the century, and then gently introduces you to Einstein’s special theory of relativity of 1905. (The special theory of relativity doesn’t take account of gravity, the general theory of relativity of 1915, does, take account of gravity).

Chapter 1 Our Picture of the Universe (pp.1-13)

Aristotle thinks earth is stationary. Calculates size of the earth. Ptolemy. Copernicus. In 1609 Galileo starts observing Jupiter using the recently invented telescope. Kepler suggests the planets move in ellipses not perfect circles. 1687 Isaac newton publishes Philosophiæ Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy) ‘probably the most important single work ever published in the physical sciences’, among many other things postulating a law of universal gravity. One implication of Newton’s theory is that the universe is vastly bigger than previously conceived.

In 1823 Heinrich Olbers posited his paradox which is, if the universe is infinite, the night sky out to be as bright as daylight because the light from infinite suns would reach us. Either it is not infinite or it has some kind of limit, possibly in time i.e. a beginning. The possible beginning or end of the universe were discussed by Immanuel Kant in his obscure work A Critique of Pure Reason  (1781). Various other figures debated variations on this theme until in 1929 Edwin Hubble made the landmark observation that, wherever you look, distant galaxies are moving away from us i.e. the universe is expanding. Working backwards from this observation led physicists to speculate that the universe was once infinitely small and infinitely dense, in a state known as a singularity, which must have exploded in an event known as the big bang.

He explains what a scientific theory is:

A theory is just a model of the universe, or a restricted part of it, and a set of rules that relate quantities in the model to observations that we make… A theory is a good theory if it satisfies two requirements: it must accurately describe a large class of observations on the basis of a model that contains only a few arbitrary elements, and it must make definite predictions about the results of future observations.

A theory is always provisional. The more evidence proving it, the stronger it gets. But it only takes one good negative observation to disprove a theory.

Today scientists describe the universe in terms of two basic partial theories – the general theory of relativity and quantum mechanics. They are the great intellectual achievements of the first half of this century.

But they are inconsistent with each other. One of the major endeavours of modern physics is to try and unite them in a quantum theory of gravity.

Chapter 2 Space and Time (pp.15-34)

Aristotle thought everything in the universe was naturally at rest. Newton disproved this with his first law – whenever a body is not acted on by any force it will keep on moving in a straight line at the same speed. Newton’s second law stats that, When a body is acted on by a force it will accelerate or change its speed at a rate that is proportional to the force. Newton’s law of gravity states that every particle attracts every other particle in the universe with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres. But like Aristotle, Newton believed all the events he described took place in a kind of big static arena named absolute space, and that time was an absolute constant. The speed of light was also realised to be a constant. In 1676 Danish astronomer Ole Christensen estimated the speed of light to be 140,000 miles per second. We now know it is 186,000 miles per second. In the 1860s James Clerk Maxwell unified the disparate theories which had been applied to magnetism and electricity.

In 1905 Einstein published his theory of relativity. It is derived not from observation but from Einstein working through in his head the consequences and shortcomings of the existing theories. Newton had posited a privileged observer, someone outside the universe who was watching it as if a play on a stage. From this privileged position a number of elements appeared constant, such as time.

Einstein imagines a universe in which there is no privileged outside point of view. We are all inside the universe and all moving. The theory threw up a number of consequences. One is that energy is equal to mass times the speed of light squared, or E = mc². Another is that nothing may travel faster than the speed of light. Another is that, as an object approaches the speed of light its mass increases. One of its most disruptive ideas is that time is relative. Different observes, travelling at different speeds, will see a beam of light travel take different times to travel a fixed distance. Since Einstein has made it axiomatic that the speed of light is fixed, and we know the distance travelled by the light is fixed, then time itself must appear different to different observers. Time is something that can change, like the other three dimensions. Thus time can be added to the existing three dimensions to create space-time.

The special theory of relativity was successful in explaining how the speed of light appears the same to all observers, and describing what happens to things when they move close to the speed of light. But it was inconsistent with Newton’s theory of gravity which says objects attract each other with a force related to the distance between them. If you move on of the objects the force exerted on the other object changes immediately. This cannot be if nothing can travel faster than the speed of light, as the special theory of relativity postulates. Einstein spent the ten or so years from 1905 onwards attempting to solve this difficulty. Finally, in 1915, he published the general theory of relativity.

The revolutionary basis of this theory is that space is not flat, a consistent  continuum or Newtonian stage within which events happen and forces interact in a sensible way. Space-time is curved or warped by the distribution of mass or energy within it, and gravity is a function of this curvature. Thus the earth is not orbiting around the sun in a circle, it is following a straight line in warped space.

The mass of the sun curves space-time in such a way that although the earth follows a straight line in four-dimensional pace-time, it appears to us to move along a circular orbit in three-dimensional space. (p.30)

In fact, at a planetary level Einstein’s maths is only slightly different from Newton’s but it predicts a slight difference in the orbit of Mercury which observations have gone on to prove. Also, the general theory predicts that light will bend, following a straight line but through space that is warped or curved by gravity. Thus the light from a distant star on the far side of the sun will bend as it passes close to the sun due to the curvature in space-time caused by the sun’s mass. And it was an expedition to West Africa in 1919 to observe an eclipse, which showed that light from distant stars did in fact bend slightly as it passed the sun, which helped confirm Einstein’s theory.

Newton’s laws of motion put an end to the idea of absolute position in space. The theory of relativity gets rid of absolute time.

Hence the thought experiment popularised by a thousand science fiction books that astronauts who set off in a space ship which gets anywhere near the speed of light will experience a time which is slower than the people they leave behind on earth.

In the theory of relativity there is no unique absolute time, but instead each individual has his own personal measure of time that depends on where he is and how he is moving. (p.33)

Obviously, since most of us are on planet earth, moving at more or less the same speed, everyone’s personal ‘times’ coincide. Anyway, the key central implication of Einstein’s general theory of relativity is this:

Before 1915, space and time were thought of as a fixed arena in which events took place, but which was not affected by what happened in it. This was true even of the special theory of relativity. Bodies moved, forces attracted and repelled, but time and space simply continued, unaffected. It was natural to think that space and time went on forever.

the situation, however, is quite different in the general theory of relativity. Space and time are now dynamic quantities. : when a body moves, or a force acts, it affects the curvature of space and time – and in turn the structure of space-time affects the way in which bodies move and forces act. Space and time not only affect but also are affected by everything that happens in the universe. (p.33)

This view of the universe as dynamic and interacting, by demolishing the old eternal static view, opened the door to a host of new ways of conceiving how the universe might have begun and might end.

Chapter 3 The Expanding Universe (pp.35-51)

Our modern picture of the universe dates to 1924 when American astronomer Edwin Hubble demonstrated that ours is not the only galaxy. We now know the universe is home to some hundred million galaxies, each containing some hundred thousand million stars. We live in a galaxy that is about one hundred thousand light-years across and is slowly rotating. Hubble set about cataloguing the movement of other galaxies and in 1929 published his results which showed that they are all moving away from us, and that, the further away a galaxy is, the faster it is moving.

The discovery that the universe is expanding was one of the great intellectual revolutions of the twentieth century. (p.39)

From Newton onwards there was a universal assumption that the universe was infinite and static. Even Einstein invented a force he called ‘the cosmological constant’ in order to counter the attractive power of gravity and preserve the model of a static universe. It was left to Russian physicist Alexander Friedmann to seriously calculate what the universe would look like if it was expanding.

In 1965 two technicians, Arno Penzias and Robert Wilson, working at Bell Telephone Laboratories discovered a continuous hum of background radiation coming from all parts of the sky. This echoed the theoretical work being done by two physicists, Bob Dicke and Jim Peebles, who were working on a suggestion made by George Gamow that the early universe would have been hot and dense. They posited that we should still be able to see the light from this earliest phase but that it would, because the redshifting, appear as radiation. Penzias and Wilson were awarded the Nobel Prize in 1987.

How can the universe be expanding? Imagine blowing up a balloon with dots (or little galaxies) drawn on it: they all move apart from each other and the further apart they are, the larger the distance becomes; but there is no centre to the balloon. Similarly the universe is expanding but not into anything. There is no outside. If you set out to travel to the edge you would find no edge but instead find yourself flying round the periphery and end up back where you began.

There are three possible states of a dynamic universe. Either 1. it will expand against the contracting force of gravity until the initial outward propulsive force is exhausted and gravity begins to win; it will stop expanding, and start to contract. Or 2. it is expanding so fast that the attractive, contracting force of gravity never wins, so the universe expands forever and matter never has time to clump together into stars and planets. Or 3. it is expanding at just the right speed to escape collapsing back in on itself, but but so fast as to make the creation of matter impossible. This is called the critical divide. Physicists now believe the universe is expanding at just around the value of the critical divide, though whether it is just under or just above (i.e. the universe will eventually cease expanding, or not) is not known.

Dark matter We can calculate the mass of all the stars and galaxies in the universe and it is a mystery that our total is only about a hundredth of the mass that must exist to explain the gravitational behaviour of stars and galaxies. In other words, there must a lot of ‘dark matter’ which we cannot currently detect in order for the universe to be shaped the way it is.

So we don’t know what the likely future of the universe is (endless expansion or eventual contraction) but all the Friedmann models do predict that the universe began in an infinitely dense, infinitely compact, infinitely hot state – the singularity.

Because mathematics cannot really handle infinite numbers, this means that the general theory of relativity… predicts that there is a point in the universe where the theory itself breaks down… In fact, all our theories of science are formulated on the assumption that space-time is smooth and nearly flat, so they break down at the big bang singularity, where the curvature of space-time is infinite. (p.46)

Opposition to the theory came from Hermann Bondi, Thomas Gold and Fred Hoyle who formulated the steady state theory of the universe i.e. it has always been and always will be. All that is needed to explain the slow expansion is the appearance of new particles to keep it filled up, but the rate is very low (about one new particle per cubic kilometre per year). They published it in 1948 and worked through all its implications for the next few decades, but it was killed off as a theory by the 1965 observations of the cosmic background radiation.

He then explains the process whereby he elected to do a PhD expanding Roger Penrose’s work on how a dying star would collapse under its own weight to a very small size. The collaboration resulted in a joint 1970 paper which proved that there must have been a big bang, provided only that the theory of general relativity is correct, and the universe contains as much matter as we observe.

If the universe really did start out as something unimaginably small then, from the 1970s onwards, physicists turned their investigations to what happens to matter at microscopic levels.

Chapter 4 The Uncertainty Principle (pp.53-61)

1900 German scientist Max Planck suggests that light, x-rays and other waves can only be emitted at an arbitrary wave, in packets he called quanta. He theorised that the higher the frequency of the wave, the more energy would be required. This would tend to restrict the emission of high frequency waves. In 1926 Werner Heisenberg expanded on these insights to produce his Uncertainty Principle. In order to locate a particle in order to measure its position and velocity you need to shine a light on it. One has to use at least one quantum of energy. However, exposing the particle to this quantum will disturb the velocity of the particle.

In other words, the more accurately you try to measure the position of the particle, the less accurately you can measure its speed, and vice versa. (p.55)

Heisenberg showed that the uncertainty in the position of the particle times the uncertainty in its velocity times the mass of the particle can never be smaller than a certain quantity, which is known as Planck’s constant. For the rest of the 1920s Heisenberg, Erwin Schrödinger and Paul Dirac reformulated mechanics into a new theory titled quantum mechanics. In this theory particles no longer have separate well-defined positions and velocities, instead they have a general quantum state which is a combination of position and velocity.

Quantum mechanics introduces an unavoidable element of unpredictability or randomness into science. (p.56)

Also, particles can no longer be relied on to be particles. As a result of Planck and Heisenberg’s insights, particles have to be thought of as sometimes behaving like waves, sometimes like particles. In 1913 Niels Bohr had suggested that electrons circle round a nucleus at certain fixed points, and that it takes energy to dislodge them from these optimum orbits. Quantum theory helped explain Bohr’s theory by conceptualising the circling electrons not as particles but as waves. If electrons are waves, as they circle the nucleus, their wave lengths would cancel each other out unless they are perfect numbers. The frequency of the waves have to be able to circle the nucleus in perfect integers. This defines the height of the orbits electrons can take.

Chapter 5 Elementary Particles and Forces of Nature (pp.63-79)

A chapter devoted to the story of how we’ve come to understand the world of sub-atomic particles. Starting (as usual) with Aristotle and then fast-forwarding through Galton, Einstein’s paper on Brownian motion, J.J. Thomson’s discovery of electrons, and, in 1911, Ernest Rutherford’s demonstration that atoms are made up of tiny positively charged nucleus around which a number of tiny positively charged particles, electrons, orbit. Rutherford thought the nuclei contained ‘protons’, which have a positive charge and balance out the negative charge of the electrons. In 1932 James Chadwick discovered the nucleus contains neutrons, same mass as the proton but no charge.

In 1965 quarks were discovered by Murray Gell-Mann. In fact scientists went on to discover six types, up, down, strange, charmed, bottom and top quarks. A proton or neutron is made up of three quarks.

He explains the quality of spin. Some particles have to be spin twice to return to their original appearance. They have spin 1/2. All the matter we can see in the universe has the spin 1/2. Particles of spin 0, 1, and 2 give rise to the forces between the particles.

Pauli’s exclusionary principle: two similar particles cannot exist in the same state, they cannot have the same position and the same velocity. The exclusionary principle is vital since it explains why the universe isn’t a big soup of primeval particles. The particles must be distinct and separate.

In 1928 Paul Dirac explained why the electron must rotate twice to return to its original position. He also predicted the existence of the positron to balance the electron. In 1932 the positron was discovered and Dirac was awarded a Nobel Prize.

Force carrying particles can be divided into four categories according to the strength of the force they carry and the particles with which they interact.

  1. Gravitational force, the weakest of the four forces by a long way.
  2. The electromagnetic force interacts with electrically charged particles like electrons and quarks.
  3. The weak nuclear force, responsible for radioactivity. In findings published in 1967 Abdus Salam and Steven Weinberg suggested that in addition to the photon there are three other spin-1 particles known collectively as massive vector bosons. Initially disbelieved, experiments proved them right and they collected the Nobel Prize in 1979. In 1983 the team at CERN proved the existence of the three particles, and the leaders of this team also won the Nobel Prize.
  4. The strong nuclear force holds quarks together in the proton and neutron, and holds the protons and neutrons together in the nucleus. This force is believed to be carried by another spin-1 particle, the gluon. They have a property named ‘confinement’ which is that you can’t have a quark of a single colour, the number of quarks bound together must cancel each other out.

The idea behind the search for a Grand Unified Theory is that, at high enough temperature, all the particles would behave in the same way, i.e. the laws governing the four forces would merge into one law.

Most of the matter on earth is made up of protons and neutrons, which are in turn made of quarks. Why is there this preponderance of quarks and not an equal number of anti-quarks?

Hawking introduces us to the notion that all the laws of physics obey three separate symmetries known as C, P and T. In 1956 two American physicists suggested that the weak force does not obey symmetry C. Hawking then goes on to explain more about the obedience or lack of obedience to the rules of symmetry of particles at very high temperatures, to explain why quarks and matter would outbalance anti-quarks and anti-matter at the big bang in a way which, frankly, I didn’t understand.

Chapter 6 Black Holes (pp.81-97)

In a sense, all the preceding has been just preparation, just a primer to help us understand the topic which Hawking spent the 1970s studying and which made his name – black holes.

The term black hole was coined by John Wheeler in 1969. Hawking explains the development of ideas about what happens when a star dies. When a star is burning, the radiation of energy in the forms of heat and light counteracts the gravity of its mass. When it runs out of fuel, gravity takes over and the star collapses in on itself. The young Indian physicist Subrahmanyan Chandrasekhar calculated that a cold star with a mass of more than one and a half times the mass of our sin would not be able to support itself against its own gravity and contract to become a ‘white dwarf’ with a radius of a few thousand miles and a density of hundreds of tones per square inch.

The Russian Lev Davidovich Landau speculated that the same sized star might end up in a different state. Chandrasekhar had used Pauli’s exclusionary principle as applied to electrons i.e. calculated the smallest densest state the mass could reach assuming no electron can be in the place of any other electron. Landau calculated on the basis of the exclusionary principle repulsion operative between neutrons and protons. Hence his model is known as the ‘neutron star’, which would have a radius of only ten miles or so and a density of hundreds of millions of tonnes per cubic inch.

(In an interesting aside Hawking tells us that physics was railroaded by the vast Manhattan Project to build an atomic bomb, and then to build a hydrogen bomb, throughout the 1940s and 50s. This tended to sideline large-scale physics about the universe. It was only the development of a) modern telescopes and b) computer power, that revived interest in astronomy.)

A black hole is what you get when the gravity of a collapsing star becomes so high that it prevents light from escaping its gravitational field. Hawking and Penrose showed that at the centre of a black hole must be a singularity of infinite density and space-time curvature.

In 1967 the study of black holes was revolutionised by Werner Israel. He showed that, according to general relativity, all non-rotating black holes must be very simple and perfectly symmetrical.

Hawking then explains several variations on this theory put forward by Roger Penrose, Roy Kerr, Brandon Carter who proved that a hole would have an axis of symmetry. Hawking himself confirmed this idea. In 1973 David Robinson proved that a black hole had to have ‘a Kerr solution’. In other words, no matter how they start out, all black holes end up looking the same, a belief summed up in the pithy phrase, ‘A black hole has no hair’.

What is striking about all this is that it was pure speculation, derived entirely from mathematical models without a shred of evidence from astronomy.

Black holes are one of only a fairly small number of cases in the history of science in which a theory was developed in great detail as a mathematical model before there was any evidence from observations that it was correct. (p.92)

Hawking then goes on to list the best evidence we have for black holes, which is surprisingly thin. Since they are by nature invisible black holes can only be deduced by their supposed affect on nearby stars or systems. Given that black holes were at the centre of Hawking’s career, and are the focus of these two chapters, it is striking that there is, even now, very little direct empirical evidence for their existence.

(Eerily, as I finished reading A Brief History of Time, the announcement was made on 10 April 2019 that the first ever image has been generated of a black hole –

Theory predicts that other stars which stray close to a black hole would have clouds of gas attracted towards it. As this matter falls into the black hole it will a) be stripped down to basic sub-atomic particles b) make the hole spin. Spinning would make the hole acquire a magnetic field. The magnetic field would shoot jets of particles out into space along the axis of rotation of the hole. These jets should be visible to our telescopes.

First ever image of a black hole, captured the Event Horizon Telescope (EHT). The hole is 40 billion km across, and 500 million trillion km away

Chapter 7 Black Holes Ain’t So Black (pp.99-113)

Black holes are not really black after all. They glow like a hot body, and the smaller they are, the hotter they glow. Again, Hawking shares with us the evolution of his thinking on this subject, for example how he was motivated in writing a 1971 paper about black holes and entropy at least partly in irritation against another researcher who he felt had misinterpreted his earlier results.

Anyway, it all resulted in his 1973 paper which showed that a black hole ought to emit particles and radiation as if it were a hot body with a temperature that depends only on the black hole’s mass.

The reasoning goes thus: quantum mechanics tells us that all of space is fizzing with particles and anti-particles popping into existence, cancelling each other out, and disappearing. At the border of the event horizon, particles and anti-particles will be popping into existence as everywhere else. But a proportion of the anti-particles in each pair will be sucked inside the event horizon, so that they cannot annihilate their partners, leaving the positive particles to ping off into space. Thus, black holes should emit a steady stream of radiation!

If black holes really are absorbing negative particles as described above, then their negative energy will result in negative mass, as per Einstein’s most famous equation, E = mc² which shows that the lower the energy, the lower the mass. In other words, if Hawking is correct about black holes emitting radiation, then black holes must be shrinking.

Gamma ray evidence suggests that there might be 300 black holes in every cubic light year of the universe. Hawking then goes on to estimate the odds of detecting a black hole a) in steady existence b) reaching its final state and blowing up. Alternatively we could look for flashes of light across the sky, since on entering the earth’s atmosphere gamma rays break up into pairs of electrons and positrons. No clear sightings have been made so far.

(Threaded throughout the chapter has been the notion that black holes might come in two types: one which resulted from the collapse of stars, as described above. And others which have been around since the start of the universe as a function of the irregularities of the big bang.)

Summary: Hawking ends this chapter by claiming that his ‘discovery’ that radiation can be emitted from black holes was ‘the first example of a prediction that depended in an essential way on both the great theories of this century, general relativity and quantum mechanics’. I.e. it is not only an interesting ‘discovery’ in its own right, but a pioneering example of synthesising the two theories.

Chapter 8 The Origin and Fate of the Universe (pp.115-141)

This is the longest chapter in the book and I found it the hardest to follow. I think this is because it is where he makes the big pitch for His Theory, for what’s come to be known as the Hartle-Hawking state. Let Wikipedia explain:

Hartle and Hawking suggest that if we could travel backwards in time towards the beginning of the Universe, we would note that quite near what might otherwise have been the beginning, time gives way to space such that at first there is only space and no time. Beginnings are entities that have to do with time; because time did not exist before the Big Bang, the concept of a beginning of the Universe is meaningless. According to the Hartle-Hawking proposal, the Universe has no origin as we would understand it: the Universe was a singularity in both space and time, pre-Big Bang. Thus, the Hartle–Hawking state Universe has no beginning, but it is not the steady state Universe of Hoyle; it simply has no initial boundaries in time or space. (Hartle-Hawking state Wikipedia article)

To get to this point Hawking begins by recapping the traditional view of the ‘hot big bang’, i.e. the almost instantaneous emergence of matter from a state of infinite mass, energy and density and temperature.

This is the view first put forward by Gamow and Alpher in 1948, which predicted there would still be very low-level background radiation left over from the bang – which was then proved with the discovery of the cosmic background radiation in 1965.

Hawking gives a picture of the complete cycle of the creation of the universe through the first generation of stars which go supernova blowing out into space the heavier particles which then go into second generation stars or clouds of gas and solidify into things like planet earth.

In a casual aside, he gives his version of the origin of life on earth:

The earth was initially very hot and without an atmosphere. In the course of time it cooled and acquired an atmosphere from the emission of gases from the rocks. This early atmosphere was not one in which we could have survived. It contained no oxygen, but a lot of other gases that are poisonous to us, such as hydrogen sulfide. There are, however, other primitive forms of life that can flourish under such conditions. It is thought that they developed in the oceans, possibly as a result of chance combinations of atoms into large structures, called macromolecules, which were capable of assembling other atoms in the ocean into similar structures. They would thus have reproduced themselves and multiplied. In some cases there would have been errors in the reproduction. Mostly these errors would have been such that the new macromolecule could not reproduce itself and eventually would have been destroyed. However, a few of the errors would have produced new macromolecules that were even better at reproducing themselves. They would have therefore had an advantage and would have tended to replace the original macromolecules. In this way a process of evolution was started that led to the development of more and more complicated, self-reproducing organisms. The first primitive forms of life consumed various materials, including hydrogen sulfide, and released oxygen. This gradually changed the atmosphere to the composition that it has today and allowed the development of higher forms of life such as fish, reptiles, mammals, and ultimately the human race. (p.121)

(It’s ironic that he discusses the issue so matter-of-factly, demonstrating that, for him at least, the matter is fairly cut and dried and not worth lingering over. Because, of course, for scientists who’ve devoted their lives to the origins-of-life question it is far from over. It’s a good example of the way that every specialist thinks that their specialism is the most important subject in the world, the subject that will finally answer the Great Questions of Life whereas a) most people have never heard about the issues b) wouldn’t understand them and c) don’t care.)

Hawking goes on to describe chaotic boundary conditions and describe the strong and the weak anthropic principles. He then explains the theory proposed by Alan Guth of inflation i.e. the universe, in the first milliseconds after the big bang, underwent a process of enormous hyper-growth, before calming down again to normal exponential expansion. Hawking describes it rather differently from Barrow and Davies. He emphasises that, to start with, in a state of hypertemperature and immense density, the four forces we know about and the spacetime dimensions were all fused into one. They would be in ‘symmetry’. Only as the early universe cooled would it have undergone a ‘phase transition’ and the symmetry between forces been broken.

If the temperature fell below the phase transition temperature without symmetry being broken then the universe would have a surplus of energy and it is this which would have cause the super-propulsion of the inflationary stage. The inflation theory:

  • would allow for light to pass from one end of the (tiny) universe to the other and explains why all regions of the universe appear to have the same properties
  • explain why the rate of expansion of the universe is close to the critical rate required to make it expand for billions of years (and us to evolve)
  • would explain why there is so much matter in the universe

Hawking then gets involved in the narrative explaining how he and others pointed out flaws in Guth’s inflationary model, namely that the phase transition at the end of the inflation ended in ‘bubble’s which expanded to join up. But Hawking and others pointed out that the bubbles were expanding so fat they could never join up. In 1981 the Russian Andre Linde proposed that the bubble problem would be solved if  a) the symmetry broke slowly and b) the bubbles were so big that our region of the universe is all contained within a single bubble. Hawking disagreed, saying Linde’s bubbles would each have to be bigger than the universe for the maths to work out, and counter-proposing that the symmetry broke everywhere at the same time, resulting in the uniform universe we see today. Nonetheless Linde’s model became known as the ‘new inflationary model’, although Hawking considers it invalid.

[In these pages we get a strong whiff of cordite. Hawking is describing controversies and debates he has been closely involved in and therefore takes a strongly partisan view, bending over backwards to be fair to colleagues, but nonetheless sticking to his guns. In this chapter you get a strong feeling for what controversy and debate within this community must feel like.)

Hawking prefers the ‘chaotic inflationary model’ put forward by Linde in 1983, in which there is no phase transition or supercooling, but which relies on quantum fluctuations.

At this point he introduces four ideas which are each challenging and which, taken together, mark the most difficult and confusing part of the book.

First he says that, since Einstein’s laws of relativity break down at the moment of the singularity, we can only hope to understand the earliest moments of the universe in terms of quantum mechanics.

Second, he says he’s going to use a particular formulation of quantum mechanics, namely Richard Feynman’s idea of ‘a sum over histories’. I think this means that Feynman said that in quantum mechanics we can never know precisely which route a particle takes, the best we can do is work out all the possible routes and assign them probabilities, which can then be handled mathematically.

Third, he immediately points out that working with Feynman’s sum over histories approach requires the use of ‘imaginary’ time, which he then goes on to explain.

To avoid the technical difficulties with Feynman’s sum over histories, one must use imaginary time. (p.134)

And then he points out that, in order to use imaginary time, we must use Euclidean space-time instead of ‘real’ space-time.

All this happens on page 134 and was too much for me to understand. On page 135 he then adds in Einstein’s idea that the gravitational field us represented by curved space-time.

It is now that he pulls all these ideas together to assert that, whereas in the classical theory of gravity, which is based on real space-time there are only two ways the universe can behave – either it has existed infinitely or it had a beginning in a singularity at a finite point in time; in the quantum theory of gravity, which uses Euclidean space-time, in which the time direction is on the same footing as directions in space it is possible:

for space-time to be finite in extent and yet to have no singularities that formed a boundary or edge.

In Hawking’s theory the universe would be finite in duration but not have a boundary in time because time would merge with the other three dimensions, all of which cease to exist during and just after a singularity. Working backwards in time, the universe shrinks but it doesn’t shrink, as a cone does, to a single distinct point – instead it has a smooth round bottom with no distinct beginning.

The Hartle-Hawking no boundary Hartle and Hawking No-Boundary Proposal

The Hartle-Hawking no boundary Hartle and Hawking No-Boundary Proposal

Finally Hawking points out that this model of a no-boundary universe derived from a Feynman interpretation of quantum gravity does not give rise to all possible universes, but only to a specific family of universes.

One aspect of these histories of the universe in imaginary time is that none of them include singularities – which would seem to render redundant all the work Hawking had done on black holes in ‘real time’. He gets round this by saying that both models can be valid, but in order to demonstrate different things.

It is simply a matter of which is the more useful description. (p.139)

He winds up the discussion by stating that further calculations based on this model explain the two or three key facts about the universe which all theories must explain i.e. the fact that it is clumped into lumps of matter and not an even soup, the fact that it is expanding, and the fact that the background radiation is minutely uneven in some places suggesting very early irregularities. Tick, tick, tick – the no-boundary proposal is congruent with all of them.

It is a little mind-boggling, as you reach the end of this long and difficult chapter, to reflect that absolutely all of it is pure speculation without a shred of evidence to support it. It is just another elegant way of dealing with the problems thrown up by existing observations and by trying to integrate quantum mechanics with Einsteinian relativity. But whether it is ‘true’ or not, not only is unproveable but also is not really the point.

Chapter 9 The Arrow of Time (pp.143-153)

If Einstein’s theory of general relativity is correct and light always appears to have the same velocity to all observers, no matter what position they’re in or how fast they’re moving, THEN TIME MUST BE FLEXIBLE. Time is not a fixed constant. Every observer carries their own time with them.

Hawking points out that there are three arrows of time:

  • the thermodynamic arrow of time which obeys the Second Law of Thermodynamics namely that entropy, or disorder, increases – there are always many more disordered states than ordered ones
  • the psychological arrow of time which we all perceive
  • the cosmological arrow of time, namely the universe is expanding and not contracting

Briskly, he tells us that the psychological arrow of time is based on the thermodynamic one: entropy increases and our lives experience that and our minds record it. For example, human beings consume food – which is a highly ordered form of energy – and convert it into heat – which is a highly disordered form.

Hawking tells us that he originally thought that, if the universe reach a furthest extent and started to contract, disorder (entropy) would decrease, and everything in the universe would happen backwards. Until Don Page and Raymond Laflamme, in their different ways, proved otherwise.

Now he believes that the contraction would not occur until the universe had been almost completely thinned out and all the stars had died i.e. the universe had become an even soup of basic particles. THEN it would start to contract. And so his current thinking is that there would be little or no thermodynamic arrow of time (all thermodynamic processes having come to an end) and all of this would be happening in a universe in which human beings could not exist. We will never live to see the contraction phase of the universe. If there is a contraction phase.

Chapter 10: The Unification of Physics (pp.155-169)

The general theory of relativity and quantum mechanics both work well for their respective scales (stars and galaxies, sub-atomic particles) but cannot be made to mesh, despite fifty of more years of valiant attempts. Many of the attempts produce infinity in their results, so many infinities that a strategy has been developed called ‘renormalisation’ which gets rid of the infinities, although Hawking conceded is ‘rather dubious mathematically’.

Grand Unified Theories is the term applied to attempts to devise a theory (i.e. a set of mathematical formulae) which will take account of the four big forces we know about: electromagnetism, gravity, the strong nuclear force and the weak nuclear force.

In the mid-1970s some scientists came up with the idea of ‘supergravity’ which postulated a ‘superparticle’, and the other sub-atomic particles variations on the super-particle but with different spins. According to Hawking the calculations necessary to assess this theory would take so long nobody has ever done it.

So he moves onto string theory i.e. the universe isn’t made up of particles but of open or closed ‘strings’, which can join together in different ways to form different particles. However, the problem with string theory is that, because of the mathematical way they are expressed, they require more than four dimensions. A lot more. Hawking mentions anywhere from ten up to 26 dimensions. Where are all these dimensions? Well, strong theory advocates say they exist but are very very small, effectively wrapped up into sub-atomic balls, so that you or I never notice them.

Rather simplistically, Hawking lists the possibilities about a complete unified theory. Either:

  1. there really is a grand unified theory which we will someday discover
  2. there is no ultimate theory but only an infinite sequence of possibilities which will describe the universe with greater and greater, but finite accuracy
  3. there is no theory of the universe at all, and events will always seems to us to occur in a random way

This leads him to repeat the highfalutin’ rhetoric which all physicists drop into at these moments, about the destiny of mankind etc. Discovery of One Grand Unified Theory:

would bring to an end a long and glorious chapter in the history of humanity’s intellectual struggle to understand the universe. But it would also revolutionise the ordinary person’s understanding of the laws that govern the universe. (p.167)

I profoundly disagree with this view. I think it is boilerplate, which is a phrase defined as ‘used in the media to refer to hackneyed or unoriginal writing’.

Because this is not just the kind of phrasing physicists use when referring to the search for GUTs, it’s the same language biologists use when referring to the quest to understand how life derived from inorganic chemicals, it’s the same language the defenders of the large Hadron Collider use to justify spending billions of euros on the search for ever-smaller particles, it’s the language used by the guys who want funding for the Search for Extra-Terrestrial Intelligence), it’s the kind of language used by the scientists bidding for funding for the Human Genome Project.

Each of these, their defenders claim, is the ultimate most important science project, quest and odyssey ever,  and when they find the solution it will for once and all answer the Great Questions which have been tormenting mankind for millennia. Etc. Which is very like all the world’s religions claiming that their God is the only God. So a) there is a pretty obvious clash between all these scientific specialities which each claim to be on the brink of revealing the Great Secret.

But b) what reading this book and John Barrow’s Book of Universes convinces me is that i) we are very far indeed from coming even close to a unified theory of the universe and more importantly ii) if one is ever discovered, it won’t matter.

Imagine for a moment that a new iteration of string theory does manage to harmonise the equations of general relativity and quantum mechanics. How many people in the world are really going to be able to understand that? How many people now, currently, have a really complete grasp of Einsteinian relativity and Heisenbergian quantum uncertainty in their strictest, most mathematical forms? 10,000? 1000,000 earthlings?

If and when the final announcement is made who would notice, who would care, and why would they care? If the final conjunction is made by adapting string theory to 24 dimensions and renormalising all the infinities in order to achieve a multi-dimensional vision of space-time which incorporates both the curvature of gravity and the unpredictable behaviour of sub-atomic particles – would this really

revolutionise the ordinary person’s understanding of the laws that govern the universe?

Chapter 11 Conclusion (pp.171-175)

Recaps the book and asserts that his and James Hartle’s no-boundary model for the origin of the universe is the first to combine classic relativity with Heisenberg uncertainty. Ends with another rhetorical flourish of trumpets which I profoundly disagree with for the reasons given above.

If we do discover a complete theory, it should in time be understandable in broad principle by everyone, not just a few scientists. Then we shall all, philosophers, scientists, and just ordinary people, be able to take part in the discussion of the question of why it is that we and the universe exist. If we find the answer to that, it would be the ultimate triumph of human reason. (p.175)

Maybe I’m wrong, but I think this is a hopelessly naive view of human nature and culture. Einstein’s general theory has been around for 104 years, quantum mechanics for 90 years. Even highly educated people understand neither of them, and what Hawking calls ‘just ordinary people’ certainly don’t – and it doesn’t matter. 

Thoughts

Of course the subject matter is difficult to understand, but Hawking makes a very good fist of putting all the ideas into simple words and phrases, avoiding all formulae and equations, and the diagrams help a lot.

My understanding is that A Brief History of Time was the first popular science to put all these ideas before the public in a reasonably accessible way, and so opened the floodgates for countless other science writers, although hardly any of the ideas in it felt new to me since I happen to have just reread the physics books by Barrow and Davies which cover much the same ground and are more up to date.

But my biggest overall impression is how provisional so much of it seems. You struggle through the two challenging chapters about black holes – Hawking’s speciality – and then are casually told that all this debating and arguing over different theories and model-making had gone on before any black holes were ever observed by astronomers. In fact, even when Hawking died, in 2018, no black holes had been conclusively identified. It’s a big shame he didn’t live to see this famous photograph being published and confirmation of at least the existence of the entity he devoted so much time to theorising about.


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The Book of Universes by John D. Barrow (2011)

This book is twice as long and half as good as Barrow’s earlier primer, The Origin of the Universe.

In that short book Barrow focused on the key ideas of modern cosmology – introducing them to us in ascending order of complexity, and as simply as possible. He managed to make mind-boggling ideas and demanding physics very accessible.

This book – although it presumably has the merit of being more up to date (published in 2011 as against 1994) – is an expansion of the earlier one, an attempt to be much more comprehensive, but which, in the process, tends to make the whole subject more confusing.

The basic premise of both books is that, since Einstein’s theory of relativity was developed in the 1910s, cosmologists and astronomers and astrophysicists have:

  1. shown that the mathematical formulae in which Einstein’s theories are described need not be restricted to the universe as it has traditionally been conceived; in fact they can apply just as effectively to a wide variety of theoretical universes – and the professionals have, for the past hundred years, developed a bewildering array of possible universes to test Einstein’s insights to the limit
  2. made a series of discoveries about our actual universe, the most important of which is that a) it is expanding b) it probably originated in a big bang about 14 billion years ago, and c) in the first few milliseconds after the bang it probably underwent a period of super-accelerated expansion known as the ‘inflation’ which may, or may not, have introduced all kinds of irregularities into ‘our’ universe, and may even have created a multitude of other universes, of which ours is just one

If you combine a hundred years of theorising with a hundred years of observations, you come up with thousands of theories and models.

In The Origin of the Universe Barrow stuck to the core story, explaining just as much of each theory as is necessary to help the reader – if not understand – then at least grasp their significance. I can write the paragraphs above because of the clarity with which The Origin of the Universe explained it.

In The Book of Universes, on the other hand, Barrow’s aim is much more comprehensive and digressive. He is setting out to list and describe every single model and theory of the universe which has been created in the past century.

He introduces the description of each model with a thumbnail sketch of its inventor. This ought to help, but it doesn’t because the inventors generally turn out to be polymaths who also made major contributions to all kinds of other areas of science. Being told a list of Paul Dirac’s other major contributions to 20th century science is not a good way for preparing your mind to then try and understand his one intervention on universe-modelling (which turned, in any case, out to be impractical and lead nowhere).

Another drawback of the ‘comprehensive’ approach is that a lot of these models have been rejected or barely saw the light of day before being disproved or – more complicatedly – were initially disproved but contained aspects or insights which turned out to be useful forty years later, and were subsequently recycled into revised models. It gets a bit challenging to try and hold all this in your mind.

In The Origin of the Universe Barrow sticks to what you could call the canonical line of models, each of which represented the central line of speculation, even if some ended up being disproved (like Hoyle and Gold and Bondi’s model of the steady state universe). Given that all of this material is pretty mind-bending, and some of it can only be described in advanced mathematical formulae, less is definitely more. I found The Book of Universes simply had too many universes, explained too quickly, and lost amid a lot of biographical bumpf summarising people’s careers or who knew who or contributed to who’s theory. Too much information.

One last drawback of the comprehensive approach is that quite important points – which are given space to breathe and sink in in The Origin of the Universe are lost in the flood of facts in The Book of Universes.

I’m particularly thinking of Einstein’s notion of the cosmological constant which was not strictly necessary to his formulations of relativity, but which Einstein invented and put into them solely in order to counteract the force of gravity and ensure his equations reflected the commonly held view that the universe was in a permanent steady state.

This was a mistake and Einstein is often quoted as admitting it was the biggest mistake of his career. In 1965 scientists discovered the cosmic background radiation which proved that the universe began in an inconceivably intense explosion, that the universe was therefore expanding and that the explosive, outward-propelling force of this bang was enough to counteract the contracting force of the gravity of all the matter in the universe without any need for a hypothetical cosmological constant.

I understand this (if I do) because in The Origin of the Universe it is given prominence and carefully explained. By contrast, in The Book of Universes it was almost lost in the flood of information and it was only because I’d read the earlier book that I grasped its importance.

The Book of Universes

Barrow gives a brisk recap of cosmology from the Sumerians and Egyptians, through the ancient Greeks’ establishment of the system named after Ptolemy in which the earth is the centre of the solar system, on through the revisions of Copernicus and Galileo which placed the sun firmly at the centre of the solar system, on to the three laws of Isaac Newton which showed how the forces which govern the solar system (and more distant bodies) operate.

There is then a passage on the models of the universe generated by the growing understanding of heat and energy acquired by Victorian physicists, which led to one of the most powerful models of the universe, the ‘heat death’ model popularised by Lord Kelvin in the 1850s, in which, in the far future, the universe evolves to a state of complete homegeneity, where no region is hotter than any other and therefore there is no thermodynamic activity, no life, just a low buzzing noise everywhere.

But this is all happens in the first 50 pages and is just preliminary throat-clearing before Barrow gets to the weird and wonderful worlds envisioned by modern cosmology i.e. from Einstein onwards.

In some of these models the universe expands indefinitely, in others it will reach a peak expansion before contracting back towards a Big Crunch. Some models envision a static universe, in others it rotates like a top, while other models are totally chaotic without any rules or order.

Some universes are smooth and regular, others characterised by clumps and lumps. Some are shaken by cosmic tides, some oscillate. Some allow time travel into the past, while others threaten to allow an infinite number of things to happen in a finite period. Some end with another big bang, some don’t end at all. And in only a few of them do the conditions arise for intelligent life to evolve.

The Book of Universes then goes on, in 12 chapters, to discuss – by my count – getting on for a hundred types or models of hypothetical universes, as conceived and worked out by mathematicians, physicists, astrophysicists and cosmologists from Einstein’s time right up to the date of publication, 2011.

A list of names

Barrow namechecks and briefly explains the models of the universe developed by the following (I am undertaking this exercise partly to remind myself of everyone mentioned, partly to indicate to you the overwhelming number of names and ideas the reader is bombarded with):

  • Aristotle
  • Ptolemy
  • Copernicus
  • Giovanni Riccioli
  • Tycho Brahe
  • Isaac Newton
  • Thomas Wright (1771-86)
  • Immanuel Kant (1724-1804)
  • Pierre Laplace (1749-1827) devised what became the standard Victorian model of the universe
  • Alfred Russel Wallace (1823-1913) discussed the physical conditions of a universe necessary for life to evolve in it
  • Lord Kelvin (1824-1907) material falls into the central region of the universe and coalesce with other stars to maintain power output over immense periods
  • Rudolf Clausius (1822-88) coined the word ‘entropy’ in 1865 to describe the inevitable progress from ordered to disordered states
  • William Jevons (1835-82) believed the second law of thermodynamics implies that universe must have had a beginning
  • Pierre Duhem (1961-1916) Catholic physicist accepted the notion of entropy but denied that it implied the universe ever had a beginning
  • Samuel Tolver Preson (1844-1917) English engineer and physicist, suggested the universe is so vast that different ‘patches’ might experience different rates of entropy
  • Ludwig Boltzmann and Ernst Zermelo suggested the universe is infinite and is already in a state of thermal equilibrium, but just with random fluctuations away from uniformity, and our galaxy is one of those fluctuations
  • Albert Einstein (1879-1955) his discoveries were based on insights, not maths: thus he saw the problem with Newtonian physics is that it privileges an objective outside observer of all the events in the universe; one of Einstein’s insights was to abolish the idea of a privileged point of view and emphasise that everyone is involved in the universe’s dynamic interactions; thus gravity does not pass through a clear, fixed thing called space; gravity bends space.

The American physicist John Wheeler once encapsulated Einstein’s theory in two sentences:

Matter tells space how to curve. Space tells matter how to move. (quoted on page 52)

  • Marcel Grossmann provided the mathematical underpinning for Einstein’s insights
  • Willem de Sitter (1872-1934) inventor of, among other things, the de Sitter effect which represents the effect of the curvature of spacetime, as predicted by general relativity, on a vector carried along with an orbiting body – de Sitter’s universe gets bigger and bigger for ever but never had a zero point; but then de Sitter’s model contains no matter
  • Vesto Slipher (1875-1969) astronomer who discovered the red shifting of distant galaxies in 1912, the first ever empirical evidence for the expansion of the galaxy
  • Alexander Friedmann (1888-1925) Russian mathematician who produced purely mathematical solutions to Einstein’s equation, devising models where the universe started out of nothing and expanded a) fast enough to escape the gravity exerted by its own contents and so will expand forever or b) will eventually succumb to the gravity of its own contents, stop expanding and contract back towards a big crunch. He also speculated that this process (expansion and contraction) could happen an infinite number of times, creating a cyclic series of bangs, expansions and contractions, then another bang etc
A graphic of the oscillating or cyclic universe (from Discovery magazine)

A graphic of the oscillating or cyclic universe (from Discovery magazine)

  • Arthur Eddington (1882-1944) most distinguished astrophysicist of the 1920s
  • George Lemaître (1894-1966) first to combine an expanding universe interpretation of Einstein’s equations with the latest data about redshifting, and show that the universe of Einstein’s equations would be very sensitive to small changes – his model is close to Eddington’s so that it is often called the Eddington-Lemaître universe: it is expanding, curved and finite but doesn’t have a beginning
  • Edwin Hubble (1889-1953) provided solid evidence of the redshifting (moving away) of distant galaxies, a main plank in the whole theory of a big bang, inventor of Hubble’s Law:
    • Objects observed in deep space – extragalactic space, 10 megaparsecs (Mpc) or more – are found to have a redshift, interpreted as a relative velocity away from Earth
    • This Doppler shift-measured velocity of various galaxies receding from the Earth is approximately proportional to their distance from the Earth for galaxies up to a few hundred megaparsecs away
  • Richard Tolman (1881-1948) took Friedmann’s idea of an oscillating universe and showed that the increased entropy of each universe would accumulate, meaning that each successive ‘bounce’ would get bigger; he also investigated what ‘lumpy’ universes would look like where matter is not evenly spaced but clumped: some parts of the universe might reach a maximum and start contracting while others wouldn’t; some parts might have had a big bang origin, others might not have
  • Arthur Milne (1896-1950) showed that the tension between the outward exploding force posited by Einstein’s cosmological constant and the gravitational contraction could actually be described using just Newtonian mathematics: ‘Milne’s universe is the simplest possible universe with the assumption that the universe s uniform in space and isotropic’, a ‘rational’ and consistent geometry of space – Milne labelled the assumption of Einsteinian physics that the universe is the same in all places the Cosmological Principle
  • Edmund Fournier d’Albe (1868-1933) posited that the universe has a hierarchical structure from atoms to the solar system and beyond
  • Carl Charlier (1862-1934) introduced a mathematical description of a never-ending hierarchy of clusters
  • Karl Schwarzschild (1873-1916) suggested  that the geometry of the universe is not flat as Euclid had taught, but might be curved as in the non-Euclidean geometries developed by mathematicians Riemann, Gauss, Bolyai and Lobachevski in the early 19th century
  • Franz Selety (1893-1933) devised a model for an infinitely large hierarchical universe which contained an infinite mass of clustered stars filling the whole of space, yet with a zero average density and no special centre
  • Edward Kasner (1878-1955) a mathematician interested solely in finding mathematical solutions to Einstein’s equations, Kasner came up with a new idea, that the universe might expand at different rates in different directions, in some parts it might shrink, changing shape to look like a vast pancake
  • Paul Dirac (1902-84) developed a Large Number Hypothesis that the really large numbers which are taken as constants in Einstein’s and other astrophysics equations are linked at a deep undiscovered level, among other things abandoning the idea that gravity is a constant: soon disproved
  • Pascual Jordan (1902-80) suggested a slight variation of Einstein’s theory which accounted for a varying constant of gravitation as through it were a new source of energy and gravitation
  • Robert Dicke (1916-97) developed an alternative theory of gravitation
  • Nathan Rosen (1909-995) young assistant to Einstein in America with whom he authored a paper in 1936 describing a universe which expands but has the symmetry of a cylinder, a theory which predicted the universe would be washed over by gravitational waves
  • Ernst Straus (1922-83) another young assistant to Einstein with whom he developed a new model, an expanding universe like those of Friedman and Lemaître but which had spherical holes removed like the bubbles in an Aero, each hole with a mass at its centre equal to the matter which had been excavated to create the hole
  • Eugene Lifschitz (1915-85) in 1946 showed that very small differences in the uniformity of matter in the early universe would tend to increase, an explanation of how the clumpy universe we live in evolved from an almost but not quite uniform distribution of matter – as we have come to understand that something like this did happen, Lifshitz’s calculations have come to be seen as a landmark
  • Kurt Gödel (1906-1978) posited a rotating universe which didn’t expand and, in theory, permitted time travel!
  • Hermann Bondi, Thomas Gold and Fred Hoyle collaborated on the steady state theory of a universe which is growing but remains essentially the same, fed by the creation of new matter out of nothing
  • George Gamow (1904-68)
  • Ralph Alpher and Robert Herman in 1948 showed that the ratio of the matter density of the universe to the cube of the temperature of any heat radiation present from its hot beginning is constant if the expansion is uniform and isotropic – they calculated the current radiation temperature should be 5 degrees Kelvin – ‘one of the most momentous predictions ever made in science’
  • Abraham Taub (1911-99) made a study of all the universes that are the same everywhere in space but can expand at different rates in different directions
  • Charles Misner (b.1932) suggested ‘chaotic cosmology’ i.e. that no matter how chaotic the starting conditions, Einstein’s equations prove that any universe will inevitably become homogenous and isotropic – disproved by the smoothness of the background radiation. Misner then suggested the Mixmaster universe, the  most complicated interpretation of the Einstein equations in which the universe expands at different rates in different directions and the gravitational waves generated by one direction interferes with all the others, with infinite complexity
  • Hannes Alfvén devised a matter-antimatter cosmology
  • Alan Guth (b.1947) in 1981 proposed a theory of ‘inflation’, that milliseconds after the big bang the universe underwent a swift process of hyper-expansion: inflation answers at a stroke a number of technical problems prompted by conventional big bang theory; but had the unforeseen implication that, though our region is smooth, parts of the universe beyond our light horizon might have grown from other areas of inflated singularity and have completely different qualities
  • Andrei Linde (b.1948) extrapolated that the inflationary regions might create sub-regions in  which further inflation might take place, so that a potentially infinite series of new universes spawn new universes in an ‘endlessly bifurcating multiverse’. We happen to be living in one of these bubbles which has lasted long enough for the heavy elements and therefore life to develop; who knows what’s happening in the other bubbles?
  • Ted Harrison (1919-2007) British cosmologist speculated that super-intelligent life forms might be able to develop and control baby universe, guiding the process of inflation so as to promote the constants require for just the right speed of growth to allow stars, planets and life forms to evolve. Maybe they’ve done it already. Maybe we are the result of their experiments.
  • Nick Bostrom (b.1973) Swedish philosopher: if universes can be created and developed like this then they will proliferate until the odds are that we are living in a ‘created’ universe and, maybe, are ourselves simulations in a kind of multiverse computer simulation

Although the arrival of Einstein and his theory of relativity marks a decisive break with the tradition of Newtonian physics, and comes at page 47 of this 300-page book, it seemed to me the really decisive break comes on page 198 with the publication Alan Guth’s theory of inflation.

Up till the Guth breakthrough, astrophysicists and astronomers appear to have focused their energy on the universe we inhabit. There were theoretical digressions into fantasies about other worlds and alternative universes but they appear to have been personal foibles and everyone agreed they were diversions from the main story.

However, the idea of inflation, while it solved half a dozen problems caused by the idea of a big bang, seems to have spawned a literally fantastic series of theories and speculations.

Throughout the twentieth century, cosmologists grew used to studying the different types of universe that emerged from Einstein’s equations, but they expected that some special principle, or starting state, would pick out one that best described the actual universe. Now, unexpectedly, we find that there might be room for many, perhaps all, of these possible universes somewhere in the multiverse. (p.254)

This is a really massive shift and it is marked by a shift in the tone and approach of Barrow’s book. Up till this point it had jogged along at a brisk rate namechecking a steady stream of mathematicians, physicists and explaining how their successive models of the universe followed on from or varied from each other.

Now this procedure comes to a grinding halt while Barrow enters a realm of speculation. He discusses the notion that the universe we live in might be a fake, evolved from a long sequence of fakes, created and moulded by super-intelligences for their own purposes.

Each of us might be mannequins acting out experiments, observed by these super-intelligences. In which case what value would human life have? What would be the definition of free will?

Maybe the discrepancies we observe in some of the laws of the universe have been planted there as clues by higher intelligences? Or maybe, over vast periods of time, and countless iterations of new universes, the laws they first created for this universe where living intelligences could evolve have slipped, revealing the fact that the whole thing is a facade.

These super-intelligences would, of course, have computers and technology far in advance of ours etc. I felt like I had wandered into a prose version of The Matrix and, indeed, Barrow apologises for straying into areas normally associated with science fiction (p.241).

Imagine living in a universe where nothing is original. Everything is a fake. No ideas are ever new. There is no novelty, no originality. Nothing is ever done for the first time and nothing will ever be done for the last time… (p.244)

And so on. During this 15-page-long fantasy the handy sequence of physicists comes to an end as he introduces us to contemporary philosophers and ethicists who are paid to think about the problem of being a simulated being inside a simulated reality.

Take Robin Hanson (b.1959), a research associate at the Future of Humanity Institute of Oxford University who, apparently, advises us all that we ought to behave so as to prolong our existence in the simulation or, hopefully, ensure we get recreated in future iterations of the simulation.

Are these people mad? I felt like I’d been transported into an episode of The Outer Limits or was back with my schoolfriend Paul, lying in a summer field getting stoned and wondering whether dandelions were a form of alien life that were just biding their time till they could take over the world. Why not, man?

I suppose Barrow has to include this material, and explain the nature of the anthropic principle (p.250), and go on to a digression about the search for extra-terrestrial life (p.248), and discuss the ‘replication paradox’ (in an infinite universe there will be infinite copies of you and me in which we perform an infinite number of variations on our lives: what would happen if you came face to face with one of your ‘copies?? p.246) – because these are, in their way, theories – if very fantastical theories – about the nature of the universe and he his stated aim is to be completely comprehensive.

The anthropic principle Observations of the universe must be compatible with the conscious and intelligent life that observes it. The universe is the way it is, because it has to be the way it is in order for life forms like us to evolve enough to understand it.

Still, it was a relief when he returned from vague and diffuse philosophical speculation to the more solid territory of specific physical theories for the last forty or so pages of the book. But it was very noticeable that, as he came up to date, the theories were less and less attached to individuals: modern research is carried out by large groups. And he increasingly is describing the swirl of ideas in which cosmologists work, which often don’t have or need specific names attached. And this change is denoted, in the texture of the prose, by an increase in the passive voice, the voice in which science papers are written: ‘it was observed that…’, ‘it was expected that…’, and so on.

  • Edward Tryon (b.1940) American particle physicist speculated that the entire universe might be a virtual fluctuation from the quantum vacuum, governed by the Heisenberg Uncertainty Principle that limits our simultaneous knowledge of the position and momentum, or the time of occurrence and energy, of anything in Nature.
  • George Ellis (b.1939) created a catalogue of ‘topologies’ or shapes which the universe might have
  • Dmitri Sokolov and Victor Shvartsman in 1974 worked out what the practical results would be for astronomers if we lived in a strange shaped universe, for example a vast doughnut shape
  • Yakob Zeldovich and Andrei Starobinsky in 1984 further explored the likelihood of various types of ‘wraparound’ universes, predicting the fluctuations in the cosmic background radiation which might confirm such a shape
  • 1967 the Wheeler-De Witt equation – a first attempt to combine Einstein’s equations of general relativity with the Schrödinger equation that describes how the quantum wave function changes with space and time
  • the ‘no boundary’ proposal – in 1982 Stephen Hawking and James Hartle used ‘an elegant formulation of quantum  mechanics introduced by Richard Feynman to calculate the probability that the universe would be found to be in a particular state. What is interesting is that in this theory time is not important; time is a quality that emerges only when the universe is big enough for quantum effects to become negligible; the universe doesn’t technically have a beginning because the nearer you approach to it, time disappears, becoming part of four-dimensional space. This ‘no boundary’ state is the centrepiece of Hawking’s bestselling book A Brief History of Time (1988). According to Barrow, the Hartle-Hawking model was eventually shown to lead to a universe that was infinitely large and empty i.e. not our one.
The Hartle-Hawking no boundary Hartle and Hawking No-Boundary Proposal

The Hartle-Hawking no boundary Hartle and Hawking No-Boundary Proposal

  • In 1986 Barrow proposed a universe with a past but no beginning because all the paths through time and space would be very large closed loops
  • In 1997 Richard Gott and Li-Xin Li took the eternal inflationary universe postulated above and speculated that some of the branches loop back on themselves, giving birth to themselves
The self-creating universe of J.Richard Gott III and Li-Xin Li

The self-creating universe of J.Richard Gott III and Li-Xin Li

  • In 2001 Justin Khoury, Burt Ovrut, Paul Steinhardt and Neil Turok proposed a variation of the cyclic universe which incorporated strong theory and they called the ‘ekpyrotic’ universe, epkyrotic denoting the fiery flame into which each universe plunges only to be born again in a big bang. The new idea they introduced is that two three-dimensional universes may approach each other by moving through the additional dimensions posited by strong theory. When they collide they set off another big bang. These 3-D universes are called ‘braneworlds’, short for membrane, because they will be very thin
  • If a universe existing in a ‘bubble’ in another dimension ‘close’ to ours had ever impacted on our universe, some calculations indicate it would leave marks in the cosmic background radiation, a stripey effect.
  • In 1998 Andy Albrecht, João Maguijo and Barrow explored what might have happened if the speed of light, the most famous of cosmological constants, had in fact decreased in the first few milliseconds after the bang? There is now an entire suite of theories known as ‘Varying Speed of Light’ cosmologies.
  • Modern ‘String Theory’ only functions if it assumes quite a few more dimensions than the three we are used to. In fact some string theories require there to be more than one dimension of time. If there are really ten or 11 dimensions then, possibly, the ‘constants’ all physicists have taken for granted are only partial aspects of constants which exist in higher dimensions. Possibly, they might change, effectively undermining all of physics.
  • The Lambda-CDM model is a cosmological model in which the universe contains three major components: 1. a cosmological constant denoted by Lambda (Greek Λ) and associated with dark energy; 2. the postulated cold dark matter (abbreviated CDM); 3. ordinary matter. It is frequently referred to as the standard model of Big Bang cosmology because it is the simplest model that provides a reasonably good account of the following properties of the cosmos:
    • the existence and structure of the cosmic microwave background
    • the large-scale structure in the distribution of galaxies
    • the abundances of hydrogen (including deuterium), helium, and lithium
    • the accelerating expansion of the universe observed in the light from distant galaxies and supernovae

He ends with a summary of our existing knowledge, and indicates the deep puzzles which remain, not least the true nature of the ‘dark matter’ which is required to make sense of the expanding universe model. And he ends the whole book with a pithy soundbite. Speaking about the ongoing acceptance of models which posit a ‘multiverse’, in which all manner of other universes may be in existence, but beyond the horizon of where can see, he says:

Copernicus taught us that our planet was not at the centre of the universe. Now we may have to accept that even our universe is not at the centre of the Universe.


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The Origin of the Universe by John D. Barrow (1994)

In the beginning, the universe was an inferno of radiation, too hot for any atoms to survive. In the first few minutes, it cooled enough for the nuclei of the lighter elements to form. Only millions of years later would the cosmos be cool enough for whole atoms to appear, followed soon by simple molecules, and after billions of years by the complex sequence of events that saw the condensation of material into stars and galaxies. Then, with the appearance of stable planetary environments, the complicated products of biochemistry were nurtured, by processes we still do not understand. (The Origin of the Universe, p.xi)

In the late 1980s and into the 1990s science writing became fashionable and popular. A new generation of science writers poured forth a wave of books popularising all aspects of science. The ones I remember fell into two broad categories, evolution and astrophysics. Authors such as Stephen Jay Gould and Edward O. Wilson, Richard Dawkins and Steve Jones (evolution and genetics) and Paul Davies, John Gribbin, John Polkinghorne and, most famously of all, Stephen Hawking, (cosmology and astrophysics) not only wrote best-selling books but cropped up as guests on radio shows and even presented their own TV series.

Early in the 1990s the literary agent John Brockman created a series titled Science Masters in which he commissioned experts across a wide range of the sciences to write short, jargon-free and maths-light introductions to their fields.

This is astrophysicist John D. Barrow’s contribution to the series, a short, clear and mind-blowing introduction to current theory about how our universe began.

The Origin of the Universe

Billions It is now thought the universe is about 13.7 billion years old, the solar system is 4.57 billion years old and the earth is 4.54 billion years old. The oldest surface rocks anywhere on earth are in northwestern Canada near the Great Slave Lake, and are 4.03 billion years. The oldest fossilised bacteria date from 3.48 billion years ago.

Visible universe The visible universe is the part of the universe which light has had time to cross and reach us. If the universe is indeed 13.7 billion years old, and nothing can travel faster than the speed of light (299,792,458 metres per second) then there is, in effect, a ‘horizon’ to what we can see. We can only see the part of the universe which is about 13.7 billion years old. Whether there is any universe beyond our light horizon, and what it looks like, is something we can only speculate about.

Steady state Until the early 20th century philosophers and scientists thought the universe was fixed, static and stable. Even Einstein put into his theory of relativity a factor he named ‘the cosmological constant’, which wasn’t strictly needed, solely in order to make the universe appear static and so conform to contemporary thinking. The idea of this constant was to counteract the attractive force of gravity, in order to ensure his steady state version of the universe didn’t collapse into a big crunch.

Alexander Friedmann It was a young mathematician, Alexander Friedmann, who looked closely at Einstein’s formulae and showed that the cosmological constant was not necessary, not if the universe was expanding; in this case, no hypothetical repelling force would be needed, just the sheer speed of outward expansion. Einstein eventually conceded that including the constant in the formulae of relativity had been a major mistake.

Edwin Hubble In what Barrow calls ‘the greatest discovery of twentieth century science’, the American astronomer Edwin Hubble in the 1920s discovered that distant galaxies are moving away from us, and the further away they are, the faster they are moving, which became known as Hubble’s Law. He established this by noticing the ‘red-shifting’ of frequencies denoting detectable elements in these galaxies i.e. their light frequencies had been altered downwards, as light (and sound and all waves are) when something is moving away from the observer.

Critical divide An argument against the steady-state theory of the universe is that, over time, the gravity of all the objects in it would pull everything together and it would all collapse into one massive clump. Only an initial throwing out of material could counter-act the affect of all that gravity.

So how fast is the universe expanding? Imagine a rate, x. Below that speed, the effect of gravity will eventually overcome the outward acceleration, the universe will slow down, stop expanding and start to contract. Significantly above this speed, x, and the universe would continue flying apart in all directions so quickly that gas clouds, stars, galaxies and planets would never be formed.

As far as we know, the actual acceleration of the universe hovers just around this rate, x – just fast enough to prevent the universe from collapsing, but not too fast for it to be impossible for matter to form. Just the right speed to create the kind of universe we see around us. The name for this threshold is the critical divide.

Starstuff Stars are condensations of matter large enough to create at their centre nuclear reactions. These reactions burn hydrogen into helium for a long, sedate period, as our sun is doing. At the end of their lives stars undergo a crisis, an explosive period of rapid change during which helium is transformed into carbon nitrogen, oxygen, silicon, phosphorus and many of the other, heavier elements. When the ailing star finally explodes as a supernova these elements disperse into space and ultimately find their way into clouds of gas which condense as planets.

Thus every plant, animal and person alive on earth is made out of chemical elements forged in the unthinkable heat of dying stars – which is what Joni Mitchell meant when she sang, ‘We are stardust’.

Heat death A theory that the universe will continue expanding and matter become so attenuated that there are no heat or dynamic inequalities left to fuel thermal reactions i.e. matter ends up smoothly spread throughout space with no reactions happening anywhere. Thermodynamic equilibrium reached at a universal very low temperature. The idea was formulated by William Thomson, Lord Kelvin, in the 1850s who extrapolated from Victorian knowledge of mechanics and heat. 170 years later, updated versions of heat death remain a viable theory for the very long-term future of the universe.

Steady state The ‘steady state’ theory of the universe was developed by astrophysicists Thomas Gold, Hermann Bondi and Fred Hoyle in 1948. They theorised that. although the universe appeared to be expanding it had always existed, the expansion being caused by a steady rate of creation of new matter. This theory was disproved in the mid-1960s by the confirmation of background radiation

Background radiation theorised In the 1940s George Gamow and assistants Alpher and Herman theorised that, if the universe began in a hot dense state way back, there should be evidence, namely a constant layer of background radiation everywhere which, they calculated, would be 5 degrees above absolute zero.

Background radiation proved In the 1960s researchers at Bell Laboratories, calibrating a sensitive radio antenna, noticed a constant background interference to their efforts which seemed to be coming from every direction of the sky. A team from Princeton interpreted this as the expected background radiation and measured it at 2.5 degrees Kelvin. It is called ‘cosmic microwave background radiation’ and is one of the strong proofs for the Big Bang theory. The uniformity of the background radiation was confirmed by observations from NASA’s Cosmic Background Explorer satellite in the early 1990s.

Empty universe There is very little material in the universe. If all the stars and galaxies in the universe were smoothed out into a sea of atoms, there would only be about one atom per cubic meter of space.

Inflation This is a theory developed in 1979 by theoretical physicist Alan Guth – the idea is that the universe didn’t arise from a singularity which exploded and grew at a steady state but instead, in the first milliseconds, underwent a period of hyper-growth, which then calmed back down to ‘normal’ expansion.

The theory has been elaborated and generated numerous variants but is widely accepted because it explains many aspects of the universe we see today – from its large-scale structure to the way it explains how minute quantum fluctuations in this initial microscopic inflationary region, once magnified to cosmic size, became the seeds for the growth of structure in the Universe.

The inflation is currently thought to have taken place from 10−36 seconds after the conjectured Big Bang singularity to sometime between 10−33 or 10−32 seconds after.

Chaotic inflationary universe Proposed by Soviet physicist Andrei Linde in 1983, this is the idea that multiple distinct sections of the very early universe might have experienced inflation at different rates and so have produced a kind of cluster of universes, like bubbles in a bubble bath, except that these bubbles would have to be at least nine billion light years in size in order to produce stable stars. Possibly the conditions in each of the universes created by chaotic inflation could be quite different.

Eternal inflation A logical extension of chaotic inflation is that you not only have multiple regions which undergo inflation at the same time, but you might have sub-regions which undergo inflation at different times – possibly one after the other, in other words maybe there never was a beginning, but this process of successive creations and hyper-inflations has been going on forever and is still going on but beyond our light horizon (which, as mentioned above, only reaches to about 13.7 billion light years away).

Time Is time a fixed and static quality which creates a kind of theatre, an external frame of reference, in which the events of the universe take place, as in the Newtonian view? Or, as per Einstein, is time itself part of the universe, inseparable from the stuff of the universe and can be bent and distorted by forces in the universe? This is why Einstein used the expression ‘spacetime’?

The quantum universe Right back at the very beginning, at 10−43 seconds, the size of the visible universe was smaller than its quantum wavelength — so its entire contents would have been subject to the uncertainty which is the characteristic of quantum physics.

Time is affected by a quantum view of the big bang because, when the universe was still shrunk to a microscopic size, the quantum uncertainty which applied to it might be interpreted as meaning there was no time. That time only ‘crystallised’ out as a separate ‘dimension’ once the universe had expanded to a size where quantum uncertainty no longer dictated.

Some critics of the big bang theory ask, ‘What was there before the big bang?’ to which exponents conventionally reply that there was no ‘before’. Time as we experience it ceased to exist and became part of the initial hyper-energy field.

This quantum interpretation suggests that there in fact was no ‘big bang’ because there was literally no time when it happened.

Traditional visualisations of the big bang show an inverted cone, at the top is the big universe we live in and as you go back in time it narrows to a point – the starting point. Imagine, instead, something more like a round-bottomed sack: there’s a general expansion upwards and outwards but if you penetrate back to the bottom of the sack there is no ‘start’ point.

This theory was most fully worked out by Stephen Hawking and James Hartle.

The Hartle-Hawking no boundary Hartle and Hawking No-Boundary Proposal

Wormholes The book ends with speculations about the possibility that ‘wormholes’ existed in the first few milliseconds, tubes connecting otherwise distant parts of the exploding ball of universe. I understood the pictures of these but couldn’t understand the problems in the quantum theory of the origin which they set out to solve.

And the final section emphasises that everything cosmologists work on relates to the visible universe. It may be that the special conditions of the visible universe which we know about, are only one set of starting conditions which apply to other areas of the universe beyond our knowledge or to other universes. We will never know.

Thoughts

Barrow is an extremely clear and patient explainer. He avoids formulae. Between his prose and the many illustrations I understood most of what he was trying to say, though a number of concepts eluded me.

But the ultimate thing that comes over is his scepticism. Barrow summarises recent attempts to define laws governing the conditions prevailing at the start of the universe by, briefly describing the theories of James Hartle and Stephen Hawking, Alex Vilenkin, and Roger Penrose. But he does so only to go on to emphasise that they are all ‘highly speculative’. They are ‘ideas for ideas’ (p.135).

By the end of the book you get the idea that a very great deal of cosmology is either speculative, or highly speculative. But then half way through he says it’s a distinguishing characteristic of physicists that they can’t stop tinkering – with data, with theories, with ideas and speculations.

So beyond the facts and then the details of the theories he describes, it is insight into this quality in the discipline itself, this restless exploration of new ideas and speculations relating to some of the hardest-to-think-about areas of human knowledge, which is the final flavour the reader is left with.


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Tau Zero by Poul Anderson (1970)

One of the most dazzling, mind-boggling and genuinely gripping novels I’ve ever read.

The story is set in the future, after the customary nuclear war which happens in so many futurestories. The twist on this one is that, after the radiation died down, the world’s powers agreed under something referred to as ‘the Covenant’ to put Sweden in charge, handing over all nuclear devices to a country big enough to manage them and keep the peace, but small enough not to have any global ambitions of her own.

Thus liberated from war, humanity – again, as in so many of these optimistic futurestories from the 1950s and 60s – has focused its efforts on space exploration using the handy new ‘ion drive’ which has been discovered, along with something called ‘Bussard engines’, helped along by elaborate ‘scoopfield webs’ to create ‘magnetohydrodynamic fields’.

Reaction mass entered the fire chamber. Thermonuclear generators energised the furious electric arcs that stripped those atoms down to ions; the magnetic fields that separated positive and negative particles; the forces that focused them into beams; the pulses that lashed them to ever higher velocities as they sped down the rings of the thrust tubes, until they emerged scarcely less fast than light itself.

The idea is that the webs are extended ‘nets’ a kilometre or so wide, which drag in all the hydrogen atoms which exist in low density in space, charging and channeling them towards the ‘drive’ which strips them to ions and thrusts them fiercely out the back of the ship – hence driving it forward.

Several voyages of exploration have already been undertaken to the nearest star systems in space ships which use these drives to travel near the speed of light, and fast-moving ‘probes’ have been sent to all the nearest star systems.

One of these probes reached the star system Centauri and now, acting on its information, a large spaceship, the Leonora Christine, is taking off on a journey to see if the third planet orbiting round Centauri really is habitable, as the probe suggests, and could be settled by ‘man’.

Einstein’s theory of relativity suggests that as any object approaches the speed of light, its experience of time slows down. The plan is for the Leonora Christine to accelerate for a couple of years towards near light speed, travel at that speed for a year, then slow down for a couple of years.

Five years there, whereupon they will either a) stay if the planet is habitable b) return, if it is not. Due to this time dilation effect those on the expedition will only age twelve years or so, while 43 or more years will pass back on earth (p.49).

(Time dilation is a key feature of Joe Haldeman’s novel, The Forever War, in which the protagonist keeps returning from tours of duty off-world to discover major changes in terrestrial society have taken place in his absence: it is, therefore, a form of one-way time travel.)

The Leonora Christine carries no fewer than fifty passengers, a cross-section of scientists, engineers, biologists and so on. Unlike any other spaceship I’ve read of it is large enough to house a gym, a theatre, a canteen and a swimming pool!

Two strands

Tau Zero is made up of two very different types of discourse. It is (apparently) a classic of ‘hard’ sci fi because not three pages go by without Anderson explaining in daunting technical detail the process workings of the ion drive, or the scoopnets, explaining the ratio of hydrogen atoms in space, or how the theory of relativity works, and so on. Not only are there sizeable chunks of uncompromising scientific information every few pages, but understanding them is key to the plot and narrative.

Starlike burned the hydrogen fusion, aft of the Bussard module that focused the electromagnetism which contained it. A titanic gas-laser effect aimed photons themselves in a beam whose reaction pushed the ship forward – and which would have vaporised any solid body it struck. The process was not 100 percent efficient. But most of the stray energy went to ionise the hydrogen which escaped nuclear combustion. These protons and electrons, together with the fusion products, were also hurled backward by the force fields, a gale of plasma adding its own increment of momentum. (p.40)

But at the same time, or regularly interspersed with the tech passages, are the passages describing the ‘human interest’ side of the journey, which is full of clichés and stereotypes, a kind of Peyton Place in space. To be more specific, the book was first published in instalments in 1967 and it has a very 1960s mindset. Anderson projects idealistic 1960s talk about ‘free love’ into a future in which adults have no moral qualms about ‘sleeping around’.

Before they leave, the novel opens with a pair of characters in a garden in Stockholm walking and having dinner and then the woman, Ingrid Lindgren, proposes to the man, Charles Reymont, that they become a couple. During all the adventures that follow, there is a continual exchanging of partners among the 25 men and 25 women on board, with little passages set aside for flirtations and guytalk about the girls or womentalk about the boys.

When a partnership ends one of the couple moves out, the other moves in with a room-mate of the same sex for a period, or immediately moves in with their new partner. It’s like wife-swapping in space. In a key moment of the plot, the ship’s resident astronomer, a short ugly anti-social and smelly man, becomes so depressed that he can no longer function. At which point Ingrid tactfully gets rid of the concerned captain and officers and… sleeps with him. So sex is deployed ‘tactically’ as a form of therapy.

Sex

He admired the sight of her. Unclad, she could never be called boyish. The curves of her breasts and flank were subtler than ordinary, but they were integral with the rest of her – not stuccoed on, as with too many women – and when she moved, they flowed. So did the light along her skin which had the hue of the hills around San Francisco Bay in their summer, and the light in her hair, which had the smell of every summer day that ever was on earth. (p.62)

Feminism

From a feminist perspective, it is striking how the 25 women aboard the ship are a) all scientists and experts in their fields b) are not passive sex objects, but very active in deciding who they want to partner with and why. One of the two strong characters in the narrative is a woman, Ingred Lindgren.

Characters

  • Captain Lars Telander
  • Ingrid Lindgren, steely disciplined first officer
  • Charles Reymont, takes over command when the ship hits crisis
  • Boris Fedoroff, Chief Engineer
  • Norbert Williams, American chemist
  • Chi-Yuen Ai-Ling, Planetologist
  • Emma Glassgold, molecular biologist
  • Jane Sadler, Canadian bio-technician
  • Machinist Johann Freiwald
  • Astronomer Elof Nilsson
  • Navigation Officer, Auguste Boudreau
  • Biosystems Chief Pereira
  • Margarita Jimenes
  • Iwamoto Tetsuo
  • Hussein Sadek
  • Yeshu ben-Zvi
  • Mohandas Chidambaran
  • Phra Takh
  • Kato M’Botu

Thus the ship’s progress proceeds smoothly, while the crew discuss decorating the canteen and common rooms, paint murals and have numerous affairs. Five years is a long time to pass in a confined ship. And meanwhile the effects of travelling ever closer to light speed create unusual effects and, to be honest, I was wondering what all the fuss was about this book.

When Leonora Christine attained a substantial fraction of light speed, its optical effects became clear to the unaided sight. Her velocity and that of the rays from a star added vectorially; the result was aberration. Except for whatever lay dead aft or ahead, the apparent position changed. Constellations grew lopsided, grew grotesque, and melted, as their members crawled across the dark. More and more, the stars thinned out behind the ship and crowded before her. (p.45)

Tau

Anderson gives us a couple of pages introducing the tau equation. This defines the ‘interdependence of space, time, matter, and energy’, If v is the velocity of the spaceship, and c the velocity of light, then tau equals the square root of 1 minus v² divided by c². In other words the closer the ship’s velocity, v, gets to the speed of light, c (186,00 miles per second), then v² divided by c² gets closer and closer to 1; therefore 1 minus something which is getting closer to 1 gets closer and closer to 0; and the square root of that number similarly approaches closer and closer to zero.

Or to put it another way, the closer tau gets to zero the faster the ship is flying, the greater its mass, and the slower the people inside it experience time, relative to the rest of the ‘static’ universe.

The plot kicks in

So the narrative trundles amiably along for the first 60 or so pages, interspersing passages of dauntingly technical exposition with the petty jealousies, love affairs and squabbles of the human characters, until…

The ship passes through an unanticipated gas cloud, just solid enough to possibly destroy her, at the very least do damage – due to the enormous speed she’s now flying at which effects her mass.

Captain Telander listens to his experts feverishly calculating what impact will mean but ultimately they have to batten down the hatches, make themselves secure and hope for the best, impact happening on page 75 of this 190-page long book.

In the event the ship survives but the technicians quickly discover that impact has knocked out the decelerating engines. Now, much worse, the technicians explain to the captain and the lead officers, First Officer Lindgren and the man responsible for crew discipline, Reymont, the terrible catch-22 they’re stuck in.

In order to investigate what’s happened to the decellerator engines, the technicians would have to go to the rear of the ship and investigate manually. Unfortunately, they would be vaporised in nano-seconds by the super-powerful ion drive if they got anywhere near it. Therefore, no-one can investigate what’s wrong with the decelerator engine until the accelerator engine is turned off.

But here’s the catch: the ship is travelling so close to the speed of light that, if they turned the accelerator engines off, the crew would all be killed in moments. Why? Because the ship is constantly being bombarded by hydrogen atoms found in small amounts throughout space. At the moment the accelerator engines and scoopfield webs are directing these atoms away from the ship and down into the ion drive. The ion drive protects the ship. The moment it is turned off, these hydrogen atoms will suddenly be bombarding the ship’s hull and, because of the speed it is going at, the effect will be to split the hydrogen atoms releasing gamma rays. The gamma rays will penetrate the hull and fry all the humans inside in moments.

Thus they cannot stop. They are doomed to continue accelerating forever or until they all die.

It is at this point that the way Anderson has introduced us to quite a few named characters, and shown them bickering, explaining abstruse theory, getting drunk and getting laid begins to show its benefits. Because the rest of the novel consists of a series of revelations about the logical implications of their plight and, if these were just explained in tech speak they would be pretty flat and dull: the drama, the grip of the novel derives from the way the matrix of characters he’s developed respond to each new revelation: getting drunk, feeling suicidal, determined to tough it out, relationships fall apart, new relationships are formed. In and of themselves these human interest passages are hardly Tolstoy, but they are vital for the novel’s success because they dramatise each new twist in the story and, as the characters discuss the implications, the time spent reading their dialogue and thoughts helps the reader, also, to process and assimilate the story’s mind-blowing logic.

A series of unfortunate incidents

Basically what happens is there is a series of four or five further revelations which confirm the astronauts in their plight, but expand it beyond their, or our, wildest imaginings.

At first the captain and engineer come up with a plan of sorts. They know, or suspect, that between galaxies the density of hydrogen atoms in the ether falls off. If they can motor beyond our galaxy they can find a place where the hydrogen density of space is so minute that they can afford to turn off the ion drive and repair the decelerator.

This is discussed in detail, with dialogue working through both the technical aspects and also the emotional consequences. Many of the crew had anticipated returning to earth to be reunited with at least some members of their family. Now that has gone for good. As has the original plan of exploring an earth-style planet.

And so we are given some mind-blowing descriptions of the ship deliberately accelerating in order to pass right through the galaxy and beyond. But unfortunately, the scientists then discover that the space between galaxies is not thin enough to protect them. Also there is another catch-22. In order to travel out of the galaxy they have had to increase speed. But now they are flying everso close to the speed of light, the risk posed by turning off the ion drive and exposing themselves to the stray hydrogen atoms in space has become greater. The faster they go in order to find space thin enough to stop in, the thinner that space has to become.

The astronomers now come to the conclusion that space is still to full of hydrogen atoms in the sectors which contain clusters of galaxies. They decide to increase the ship’s velocity even more in order not just to leave our galaxy, but to get clear of our entire family of galaxies. This they calculate, will take another year or so at present velocities.

Thus it is that the book moves forward by presenting a new problem, the scientists suggest a solution which involves travelling faster and further, the crew is told and slowly gets used to the idea, as do we, via various conversations and attitudes and emotional responses. But when that goal is attained, it turns out there is another problem, and so the tension and the narrative drive of the book is relentlessly ratcheted up.

And of course, the further they travel and the closer to light speed, the more the tau effect predicts that time slows down for them, or, to put it another way, time speeds up for the rest of the universe. Early on in the post-disaster section, the crew assemble to celebrate the fact that a hundred years have passed back on earth: everyone they knew is dead. It is a sombre assembly with heavy drinking, casual sex, melancholy thoughts.

But by the time we get to the bit where they have flown clear of the galaxy only to be disappointed to find that inter-galactic space is too full of hydrogen for them to stop, by this stage they realise that thousands of years have passed back on earth.

By the time they fly free of the entire cluster of galaxies, they know that tens of thousands of years have passed. And eventually, as their tau approaches closer and closer to zero, they realise that millions of years have passed (one million is passed n page 136).

For when they do eventually fly beyond our entire family of galaxies they encounter another problem which is discovering that empty space is now too dispersed to allow them to decelerate. Even if they turn off the ion drive and fix the decelerating engine, there isn’t enough matter in truly empty space for the engine to latch on to and use as fuel to slow them (p.147).

Thus they decide to continue onwards, letting their acceleration, and mass, increase until they find a part of space with just the right conditions.

The accessible mass of the whole galactic clan that was her goal proved inadequate to brake her velocity. Therefore she did not try. Instead, she used what she swallowed to drive forward all the faster. She traversed the domain of this second clan – with no attempt at manual control, simply spearing through a number of its member galaxies – in two days. On the far side, again into hollow space, she fell free. The stretch to the next attainable clan was on the order of another hundred million light-years. She made the passage in about a week. (p.151)

On they fly at incomprehensible speed, while various human interest stories unfurl between the ship’s crew, until they (and the reader) reach the blasé condition of feeling the ship’s hull rattle and hum for a few moments and a character will say, ‘There goes another galaxy’.

Now if this was a J.G. Ballard novel, they’d all have gone mad and started eating each other by now. Anderson’s take on human psychology is much more bland and optimistic. Some of the crew get a bit depressed, but nothing some casual sex, or a project to redecorate the canteen can’t fix.

The main ‘human’ part of the narrative describes the way the ship’s ‘constable’, Charles Reymont who we met back on the opening pages, takes effective control from the captain. Initially this is basic psychology, Charles realising it will help discipline best if the captain becomes an aloof figure beyond criticism or reproach while he, Charles, imposes discipline, structure and purpose – allotting the crew tasks and missions to perform to maintain their morale, and letting them hate or resent him for it if they will. But over time the captain really does lose the ability to decide anything and Charles becomes the ship’s dictator. This is complicated by the fact that he discovers the woman who had suggested they become a couple, Ingrid, in someone else’s bed though she swears she was only doing it for therapeutic purposes. They split up and Charles pairs off with the Chinese planetologist, Chi-Yuen Ai-Ling, leading to a number of sexy descriptions of her naked body. But Ingrid continues to hold a torch for him and he for her. That’s the spine of the ‘human interest’ part of the novel.

Hundreds of millions of years have passed and indeed, in the last 40 pages or so a character lets slips that it must be over a billion years since they left earth.

it’s at this stage that the book becomes truly visionary. For, after some delay and conferring with colleagues, the astronomer comes to the captain and Reymont and Lindgren to announce that… the universe itself is changing. The galaxies they are flying through no longer contain fit young stars. Increasingly what they’re seeing through their astronomical instruments (not the naked eye) is that the galaxies are made of low intensity red dwarfs.

The universe is running down.

So many billion years have passed – one character estimates one hundred billion years (p.170) that they have travelled far into ‘the future’ and are witnessing the end of the universe. The stars are going out and the actual space of the universe is contracting.

Anderson’s vision is based on the theory that the universe began in a big bang, has and will expand for billions of years but will eventually reach a stage where the initial blast of energy from the bang is so dispersed that it is countered by the cumulative gravity of all the matter in the universe – which will stop it expanding and make it slowly and then with ever-increasing speed, hurtle towards a ‘Big Crunch’ when all the matter in the universe returns to the primal singularity.

Face with this haunting, terrifying fact, the scientists again make calculations and act on a hunch. They guess that the singularity won’t actually become a minute particle but will be shrouded in ‘en enormous hydrogen envelope’ (p.175), the simplest chemical, and calculate that the ship will be flying so fast that it will survive the Big Crunch and live on to witness the creation of the next universe.

‘The outer part of that envelope may not be too hot or radiant or dense for us. Space will be small enough, though, that we can circle around and around the monobloc as a kind of satellite. When it blows up and space starts to expand again, we’ll spiral out ourselves.’ (Reymont, p.175)

And this is what happens. Anderson gives a mind bogging description of the ship reaching such an infinitesimal value of tau that it flies right through the Big Crunch and out into the new universe which explodes outwards (pp.181-3).

Indeed it is travelling so fast, and time outside is moving so fast, that they can chose how many billions of years into the history of the new universe they want to stop (p.184). A quick calculation suggests that it took about 10 billion years for a plenty like earth to come into being and establish the conditions for life to evolve, and so they calculate their deceleration to take place that far into the future of this new universe.

Epilogue

And this is what they do, and the last few pages cut to Reymont and Ingrid, the lovers we met in the opening pages falling dreamily in love, now lying under a tree on a planet which has an earth-like atmosphere but blue vegetation, three moons and all sorts of weird fauna and flora, as they plan their lives together (pp.188-190)

We left plausibility behind a long time ago. Instead the book turns into an absolutely gripping rollercoaster of a ride, one of the most genuinely mind-blowing and gripping stories I’ve ever read. What a trip!


Style

the foregoing summary may give the impression the story is told in language as clear as an instruction manual, but this would be wrong.

Putting the plot to one side, one of the most striking features of Tau Zero is its prose style – an odd and ungainly variant of standard English which makes you pause on every page.

Leonora Christine was nearing the third year of her journey, or the tenth year as the stars counted time, when grief came upon her. (p.63)

Anderson was born in America (in 1926) but his mother took him as a boy to live in Denmark where she’d originally come from, until the outbreak of war forced them to return. For this or the general fact of growing up in an immigrant Scandinavian family, Anderson’s English is oddly stilted and phrased. It often sounds like it’s been translated from a Norse saga.

She gave him cheerful greeting as he entered. (p.52)

They would live out their lives, and belike their children and grandchildren too (p.53)

He stood moveless (p.58)

Nor would he have stopped to dress, had he been abed. (p.64)

Telander must perforce smile a bit as he went out the door. (p.69)

Fedoroff spoke. His words fell contemptuous. (p.80)

He clapped the navigator’s back in friendly wise. (p.159)

She rested elbow on head, forehead on hand. (p.161)

Every pages has sentences containing odd kinks away from natural English. As a small example it’s typified by the way Anderson refers throughout the story not to the ship’s ‘crew’, but to its folk. Another consistent quirk is the way people don’t experience emotions or psychological states, these, in the form of abstract nouns, come over them.

Soberness had come upon her. (p.100)

Dismay sprang forth on Williams. (p.105)

Anger still upbore the biologist. (p.106)

Dismay shivered in her. (p.116)

Hardness fell from him. (p.125)

Weight grabbed at Reymont. (.167)

Sometimes he achieves a kind of incongruous poetry by accident.

Footsteps thudded in the mumble of energies. (p.70)

Ingrid Lindgren regarded him for a time that shivered. (p.71)

The ship jeered at him in her tone of distant lightnings. (p.84)

Sometimes it makes the already challenging technical explanations just that little bit more impenetrable.

Then again, maybe this slightly alien English helps to create a sense of mild dislocation which is not inappropriate for a science fiction story, especially one which takes us right to the edge of the universe and then beyond!


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Other science fiction reviews

1888 Looking Backward 2000-1887 by Edward Bellamy – Julian West wakes up in the year 2000 to discover a peaceful revolution has ushered in a society of state planning, equality and contentment
1890 News from Nowhere by William Morris – waking from a long sleep, William Guest is shown round a London transformed into villages of contented craftsmen

1895 The Time Machine by H.G. Wells – the unnamed inventor and time traveller tells his dinner party guests the story of his adventure among the Eloi and the Morlocks in the year 802,701
1896 The Island of Doctor Moreau by H.G. Wells – Edward Prendick is stranded on a remote island where he discovers the ‘owner’, Dr Gustave Moreau, is experimentally creating human-animal hybrids
1897 The Invisible Man by H.G. Wells – an embittered young scientist, Griffin, makes himself invisible, starting with comic capers in a Sussex village, and ending with demented murders
1898 The War of the Worlds – the Martians invade earth
1899 When The Sleeper Wakes/The Sleeper Wakes by H.G. Wells – Graham awakes in the year 2100 to find himself at the centre of a revolution to overthrow the repressive society of the future
1899 A Story of the Days To Come by H.G. Wells – set in the same future London as The Sleeper Wakes, Denton and Elizabeth defy her wealthy family in order to marry, fall into poverty, and experience life as serfs in the Underground city run by the sinister Labour Corps

1901 The First Men in the Moon by H.G. Wells – Mr Bedford and Mr Cavor use the invention of ‘Cavorite’ to fly to the moon and discover the underground civilisation of the Selenites
1904 The Food of the Gods and How It Came to Earth by H.G. Wells – scientists invent a compound which makes plants, animals and humans grow to giant size, prompting giant humans to rebel against the ‘little people’
1905 With the Night Mail by Rudyard Kipling – it is 2000 and the narrator accompanies a GPO airship across the Atlantic
1906 In the Days of the Comet by H.G. Wells – a comet passes through earth’s atmosphere and brings about ‘the Great Change’, inaugurating an era of wisdom and fairness, as told by narrator Willie Leadford
1908 The War in the Air by H.G. Wells – Bert Smallways, a bicycle-repairman from Kent, gets caught up in the outbreak of the war in the air which brings Western civilisation to an end
1909 The Machine Stops by E.M. Foster – people of the future live in underground cells regulated by ‘the Machine’ until one of them rebels

1912 The Lost World by Sir Arthur Conan Doyle – Professor Challenger leads an expedition to a plateau in the Amazon rainforest where prehistoric animals still exist
1912 As Easy as ABC by Rudyard Kipling – set in 2065 in a world characterised by isolation and privacy, forces from the ABC are sent to suppress an outbreak of ‘crowdism’
1913 The Horror of the Heights by Arthur Conan Doyle – airman Captain Joyce-Armstrong flies higher than anyone before him and discovers the upper atmosphere is inhabited by vast jellyfish-like monsters
1914 The World Set Free by H.G. Wells – A history of the future in which the devastation of an atomic war leads to the creation of a World Government, told via a number of characters who are central to the change
1918 The Land That Time Forgot by Edgar Rice Burroughs – a trilogy of pulp novellas in which all-American heroes battle ape-men and dinosaurs on a lost island in the Antarctic

1921 We by Evgeny Zamyatin – like everyone else in the dystopian future of OneState, D-503 lives life according to the Table of Hours, until I-330 wakens him to the truth
1925 Heart of a Dog by Mikhail Bulgakov – a Moscow scientist transplants the testicles and pituitary gland of a dead tramp into the body of a stray dog, with disastrous consequences
1927 The Maracot Deep by Arthur Conan Doyle – a scientist, engineer and a hero are trying out a new bathysphere when the wire snaps and they hurtle to the bottom of the sea, there to discover…

1930 Last and First Men by Olaf Stapledon – mind-boggling ‘history’ of the future of mankind over the next two billion years
1938 Out of the Silent Planet by C.S. Lewis – baddies Devine and Weston kidnap Ransom and take him in their spherical spaceship to Malacandra aka Mars,

1943 Perelandra (Voyage to Venus) by C.S. Lewis – Ransom is sent to Perelandra aka Venus, to prevent a second temptation by the Devil and the fall of the planet’s new young inhabitants
1945 That Hideous Strength: A Modern Fairy-Tale for Grown-ups by C.S. Lewis– Ransom assembles a motley crew to combat the rise of an evil corporation which is seeking to overthrow mankind
1949 Nineteen Eighty-Four by George Orwell – after a nuclear war, inhabitants of ruined London are divided into the sheep-like ‘proles’ and members of the Party who are kept under unremitting surveillance

1950 I, Robot by Isaac Asimov – nine short stories about ‘positronic’ robots, which chart their rise from dumb playmates to controllers of humanity’s destiny
1950 The Martian Chronicles – 13 short stories with 13 linking passages loosely describing mankind’s colonisation of Mars, featuring strange, dreamlike encounters with Martians
1951 Foundation by Isaac Asimov – the first five stories telling the rise of the Foundation created by psychohistorian Hari Seldon to preserve civilisation during the collapse of the Galactic Empire
1951 The Illustrated Man – eighteen short stories which use the future, Mars and Venus as settings for what are essentially earth-bound tales of fantasy and horror
1952 Foundation and Empire by Isaac Asimov – two long stories which continue the future history of the Foundation set up by psychohistorian Hari Seldon as it faces attack by an Imperial general, and then the menace of the mysterious mutant known only as ‘the Mule’
1953 Second Foundation by Isaac Asimov – concluding part of the ‘trilogy’ describing the attempt to preserve civilisation after the collapse of the Galactic Empire
1953 Earthman, Come Home by James Blish – the adventures of New York City, a self-contained space city which wanders the galaxy 2,000 years hence powered by spindizzy technology
1953 Fahrenheit 451 by Ray Bradbury – a masterpiece, a terrifying anticipation of a future when books are banned and professional firemen are paid to track down stashes of forbidden books and burn them
1953 Childhood’s End by Arthur C. Clarke a thrilling narrative involving the ‘Overlords’ who arrive from space to supervise mankind’s transition to the next stage in its evolution
1954 The Caves of Steel by Isaac Asimov – set 3,000 years in the future when humans have separated into ‘Spacers’ who have colonised 50 other planets, and the overpopulated earth whose inhabitants live in enclosed cities or ‘caves of steel’, and introducing detective Elijah Baley to solve a murder mystery
1956 The Naked Sun by Isaac Asimov – 3,000 years in the future detective Elijah Baley returns, with his robot sidekick, R. Daneel Olivaw, to solve a murder mystery on the remote planet of Solaria
1956 They Shall Have Stars by James Blish – explains the invention – in the near future – of the anti-death drugs and the spindizzy technology which allow the human race to colonise the galaxy
1957 The Black Cloud by Fred Hoyle – a vast cloud of gas heads into the solar system, blocking out heat and light from the sun with cataclysmic consequences on Earth, until a small band of maverick astronomers discovers that the cloud contains intelligence and can be communicated with
1959 The Triumph of Time by James Blish – concluding story of Blish’s Okie tetralogy in which Amalfi and his friends are present at the end of the universe

1961 A Fall of Moondust by Arthur C. Clarke a pleasure tourbus on the moon is sucked down into a sink of moondust, sparking a race against time to rescue the trapped crew and passengers
1962 A Life For The Stars by James Blish – third in the Okie series about cities which can fly through space, focusing on the coming of age of kidnapped earther, young Crispin DeFord, aboard New York
1962 The Man in the High Castle by Philip K. Dick In an alternative future America lost the Second World War and has been partitioned between Japan and Nazi Germany. The narrative follows a motley crew of characters including a dealer in antique Americana, a German spy who warns a Japanese official about a looming surprise German attack, and a woman determined to track down the reclusive author of a hit book which describes an alternative future in which America won the Second World War
1963 Planet of the Apes by Pierre Boulle French journalist Ulysse Mérou accompanies Professor Antelle on a two-year space flight to the star Betelgeuse, where they land on an earth-like plane to discover that humans and apes have evolved here, but the apes are the intelligent, technology-controlling species while the humans are mute beasts
1968 2001: A Space Odyssey a panoramic narrative which starts with aliens stimulating evolution among the first ape-men and ends with a spaceman being transformed into galactic consciousness
1968 Do Androids Dream of Electric Sheep? by Philip K. Dick In 1992 androids are almost indistinguishable from humans except by trained bounty hunters like Rick Deckard who is paid to track down and ‘retire’ escaped andys
1969 Ubik by Philip K. Dick In 1992 the world is threatened by mutants with psionic powers who are combated by ‘inertials’. The novel focuses on the weird alternative world experienced by a group of inertials after a catastrophe on the moon

1970 Tau Zero by Poul Anderson – spaceship Leonora Christine leaves earth with a crew of fifty to discover if humans can colonise any of the planets orbiting the star Beta Virginis, but when its deceleration engines are damaged, the crew realise they need to exit the galaxy altogether in order to find space with low enough radiation to fix the engines, and then a series of unfortunate events mean they find themselves forced to accelerate faster and faster, effectively travelling through time as well as space until they witness the end of the entire universe
1971 Mutant 59: The Plastic Eater by Kit Pedler and Gerry Davis – a genetically engineered bacterium starts eating the world’s plastic
1973 Rendezvous With Rama by Arthur C. Clarke – in 2031 a 50-kilometre long object of alien origin enters the solar system, so the crew of the spaceship Endeavour are sent to explore it
1974 Flow My Tears, The Policeman Said by Philip K. Dick – America after the Second World War has become an authoritarian state. The story concerns popular TV host Jason Taverner who is plunged into an alternative version of this world in which he is no longer a rich entertainer but down on the streets among the ‘ordinaries’ and on the run from the police. Why? And how can he get back to his storyline?
1974 The Forever War by Joe Haldeman The story of William Mandella who is recruited into special forces fighting the Taurans, a hostile species who attack Earth outposts, successive tours of duty requiring interstellar journeys during which centuries pass on Earth, so that each of his return visits to the home planet show us society’s massive transformations over the course of the thousand years the war lasts.

1981 The Golden Age of Science Fiction edited by Kingsley Amis – 17 classic sci-fi stories from what Amis considers the Golden Era of the genre, namely the 1950s
1982 2010: Odyssey Two by Arthur C. Clarke – Heywood Floyd joins a Russian spaceship on a two-year journey to Jupiter to a) reclaim the abandoned Discovery and b) investigate the monolith on Japetus
1984 Neuromancer by William Gibson – burnt-out cyberspace cowboy Case is lured by ex-hooker Molly into a mission led by ex-army colonel Armitage to penetrate the secretive corporation, Tessier-Ashpool at the bidding of the vast and powerful artificial intelligence, Wintermute
1986 Burning Chrome by William Gibson – ten short stories, three or four set in Gibson’s ‘Sprawl’ universe, the others ranging across sci-fi possibilities, from a kind of horror story to one about a failing Russian space station
1986 Count Zero by William Gibson
1987 2061: Odyssey Three by Arthur C. Clarke – Spaceship Galaxy is hijacked and forced to land on Europa, moon of the former Jupiter, in a ‘thriller’ notable for Clarke’s descriptions of the bizarre landscapes of Halley’s Comet and Europa
1988 Mona Lisa Overdrive by William Gibson – third of Gibson’s ‘Sprawl’ trilogy in which street-kid Mona is sold by her pimp to crooks who give her plastic surgery to make her look like global simstim star Angie Marshall who they plan to kidnap but is herself on a quest to find her missing boyfriend, Bobby Newmark, one-time Count Zero, while the daughter of a Japanese ganster who’s sent her to London for safekeeping is abducted by Molly Millions, a lead character in Neuromancer

1990 The Difference Engine by William Gibson and Bruce Sterling – in an alternative history Charles Babbage’s early computer, instead of being left as a paper theory, was actually built, drastically changing British society, so that by 1855 it is led by a party of industrialists and scientists who use databases and secret police to keep the population under control

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