Nuclear war is still probably the greatest threat to humanity at the present time. It is a danger we have rather forgotten. Russia and the United States are no longer so trigger-happy, but suppose there’s an accident, or terrorists get hold of the weapons these countries still have. And the risk increases the more countries obtain nuclear weapons. Even after the end of the Cold War, there are still enough nuclear weapons stockpiled to kill us all, several times over, and new nuclear nations will add to the instability. With time, the nuclear threat may decrease, but other threats will develop, so we must remain on our guard.
One way or another, I regard it as almost inevitable that either a nuclear confrontation or environmental catastrophe will cripple the Earth at some point in the next 1,000 years which, as geological time goes, is the mere blink of an eye. By then I hope and believe that our ingenious race will have found a way to slip the surly bonds of Earth and will therefore survive the disaster. The same of course may not be possible for the millions of other species that inhabit the Earth, and that will be on our conscience as a race.
I think we are acting with reckless indifference to our future on planet Earth. At the moment, we have nowhere else to go, but in the long run the human race shouldn’t have all its eggs in one basket, or on one planet. I just hope we can avoid dropping the basket before we learn how to escape from Earth. But we are, by nature, explorers. Motivated by curiosity. This is a uniquely human quality. It is this driven curiosity that sent explorers to prove the Earth is not flat and it is the same instinct that sends us to the stars at the speed of thought, urging us to go there in reality. And whenever we make a great new leap, such as the Moon landings, we elevate humanity, bring people and nations together, usher in new discoveries and new technologies. To leave Earth demands a concerted global approach—everyone should join in. We need to rekindle the excitement of the early days of space travel in the 1960s. The technology is almost within our grasp. It is time to explore other solar systems. Spreading out may be the only thing that saves us from ourselves. I am convinced that humans need to leave Earth. If we stay, we risk being annihilated.
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So, beyond my hope for space exploration, what will the future look like and how might science help us?
The popular picture of science in the future is shown in science-fiction series like Star Trek. The producers of Star Trek even persuaded me to take part, not that it was difficult.
That appearance was great fun, but I mention it to make a serious point. Nearly all the visions of the future that we have been shown from H. G. Wells onwards have been essentially static. They show a society that is in most cases far in advance of ours, in science, in technology and in political organisation. (The last might not be difficult.) In the period between now and then there must have been great changes, with their accompanying tensions and upsets. But, by the time we are shown the future, science, technology and the organisation of society are supposed to have achieved a level of near-perfection.
I question this picture and ask if we will ever reach a final steady state of science and technology. At no time in the 10,000 years or so since the last Ice Age has the human race been in a state of constant knowledge and fixed technology. There have been a few setbacks, like what we used to call the Dark Ages after the fall of the Roman Empire. But the world’s population, which is a measure of our technological ability to preserve life and feed ourselves, has risen steadily, with a few hiccups like the Black Death. In the last 200 years the growth has at times been exponential—and the world population has jumped from 1 billion to about 7.6 billion. Other measures of technological development in recent times are electricity consumption, or the number of scientific articles. They too show near-exponential growth. Indeed, we now have such heightened expectations that some people feel cheated by politicians and scientists because we have not already achieved the Utopian visions of the future. For example, the film 2001: A Space Odyssey showed us with a base on the Moon and launching a manned, or should I say personned, flight to Jupiter.
There is no sign that scientific and technological development will dramatically slow down and stop in the near future. Certainly not by the time of Star Trek, which is only about 350 years away. But the present rate of growth cannot continue for the next millennium. By the year 2600 the world’s population would be standing shoulder to shoulder and the electricity consumption would make the Earth glow red hot. If you stacked the new books being published next to each other, at the present rate of production you would have to move at ninety miles an hour just to keep up with the end of the line. Of course, by 2600 new artistic and scientific work will come in electronic forms rather than as physical books and papers. Nevertheless, if the exponential growth continued, there would be ten papers a second in my kind of theoretical physics, and no time to read them.
Clearly the present exponential growth cannot continue indefinitely. So what will happen? One possibility is that we will wipe ourselves out through some disaster such as a nuclear war. Even if we don’t destroy ourselves completely there is the possibility that we might descend into a state of brutalism and barbarity, like the opening scene of Terminator.
How will we develop in science and technology over the next millennium? This is very difficult to answer. But let me stick my neck out and offer my predictions for the future. I will have some chance of being right about the next hundred years, but the rest of the millennium will be wild speculation.
Our modern understanding of science began about the same time as the European settlement of North America, and by the end of the nineteenth century it seemed that we were about to achieve a complete understanding of the universe in terms of what are now known as classical laws. But, as we have seen, in the twentieth century observations began to show that energy came in discrete packets called quanta and a new kind of theory called quantum mechanics was formulated by Max Planck and others. This presented a completely different picture of reality in which things don’t have a single unique history, but have every possible history each with its own probability. When one goes down to the individual particles, the possible particle histories have to include paths that travel faster than light and even paths that go back in time. However, these paths that go back in time are not just like angels dancing on a pin. They have real observational consequences. Even what we think of as empty space is full of particles moving in closed loops in space and time. That is, they move forwards in time on one side of the loop and backwards in time on the other side.
The awkward thing is that because there’s an infinite number of points in space and time, there’s an infinite number of possible closed loops of particles. And an infinite number of closed loops of particles would have an infinite amount of energy and would curl space and time up to a single point. Even science fiction did not think of anything as odd as this. Dealing with this infinite energy requires some really creative accounting, and much of the work in theoretical physics in the last twenty years has been looking for a theory in which the infinite number of closed loops in space and time cancel each other completely. Only then will we be able to unify quantum theory with Einstein’s general relativity and achieve a complete theory of the basic laws of the universe.
What are the prospects that we will discover this complete theory in the next millennium? I would say they were very good, but then I’m an optimist. In 1980 I said I thought there was a 50–50 chance that we would discover a complete unified theory in the next twenty years. We have made some remarkable progress in the period since then, but the final theory seems about the same distance away. Will the Holy Grail of physics be always just beyond our reach? I think not.
At the beginning of the twentieth century we understood the workings of nature on the scales of classical physics that are good down to about a hundredth of a millimetre. The work on atomic physics in the first thirty years of the century took our understanding down to lengths of a millionth of a millimetre. Since then, research on nuclear
and high-energy physics has taken us to length scales that are smaller by a further factor of a billion. It might seem that we could go on forever discovering structures on smaller and smaller length scales. However, there is a limit to this series as with a series of nested Russian dolls. Eventually one gets down to a smallest doll, which can’t be taken apart any more. In physics the smallest doll is called the Planck length and is a millimetre divided by a 100,000 billion billion billion. We are not about to build particle accelerators that can probe to distances that small. They would have to be larger than the solar system and they are not likely to be approved in the present financial climate. However, there are consequences of our theories that can be tested by much more modest machines.
It won’t be possible to probe down to the Planck length in the laboratory, though we can study the Big Bang to get observational evidence at higher energies and shorter length scales than we can achieve on Earth. However, to a large extent we shall have to rely on mathematical beauty and consistency to find the ultimate theory of everything.
The Star Trek vision of the future in which we achieve an advanced but essentially static level may come true in respect of our knowledge of the basic laws that govern the universe. But I don’t think we will ever reach a steady state in the uses we make of these laws. The ultimate theory will place no limit on the complexity of systems that we can produce, and it is in this complexity that I think the most important developments of the next millennium will be.
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By far the most complex systems that we have are our own bodies. Life seems to have originated in the primordial oceans that covered the Earth four billion years ago. How this happened we don’t know. It may be that random collisions between atoms built up macromolecules that could reproduce themselves and assemble themselves into more complicated structures. What we do know is that by three and a half billion years ago the highly complicated molecule DNA had emerged. DNA is the basis for all life on Earth. It has a double-helix structure, like a spiral staircase, which was discovered by Francis Crick and James Watson in the Cavendish lab at Cambridge in 1953. The two strands of the double helix are linked by pairs of nitrogenous bases like the treads in a spiral staircase. There are four kinds of nitrogenous bases: cytosine, guanine, adenine and thymine. The order in which the different nitrogenous bases occur along the spiral staircase carries the genetic information that enables the DNA molecule to assemble an organism around it and reproduce itself. As the DNA made copies of itself there would have been occasional errors in the order of the nitrogenous bases along the spiral. In most cases the mistakes in copying would have made the DNA unable to reproduce itself. Such genetic errors, or mutations as they are called, would die out. But in a few cases the error or mutation would increase the chances of the DNA surviving and reproducing. Thus the information content in the sequence of nitrogenous bases would gradually evolve and increase in complexity. This natural selection of mutations was first proposed by another Cambridge man, Charles Darwin, in 1858, though he didn’t know the mechanism for it.
Because biological evolution is basically a random walk in the space of all genetic possibilities, it has been very slow. The complexity, or number of bits of information that are coded in DNA, is given roughly by the number of nitrogenous bases in the molecule. Each bit of information can be thought of as the answer to a yes/no question. For the first two billion years or so the rate of increase in complexity must have been of the order of one bit of information every hundred years. The rate of increase of DNA complexity gradually rose to about one bit a year over the last few million years. But now we are at the beginning of a new era in which we will be able to increase the complexity of our DNA without having to wait for the slow process of biological evolution. There has been relatively little change in human DNA in the last 10,000 years. But it is likely that we will be able to redesign it completely in the next thousand. Of course, many people will say that genetic engineering on humans should be banned. But I rather doubt that they will be able to prevent it. Genetic engineering on plants and animals will be allowed for economic reasons, and someone is bound to try it on humans. Unless we have a totalitarian world order, someone will design improved humans somewhere.
Clearly developing improved humans will create great social and political problems with respect to unimproved humans. I’m not advocating human genetic engineering as a good thing, I’m just saying that it is likely to happen in the next millennium, whether we want it or not. This is why I don’t believe science fiction like Star Trek where people are essentially the same 350 years in the future. I think the human race, and its DNA, will increase its complexity quite rapidly.
In a way, the human race needs to improve its mental and physical qualities if it is to deal with the increasingly complex world around it and meet new challenges like space travel. And it also needs to increase its complexity if biological systems are to keep ahead of electronic ones. At the moment computers have an advantage of speed, but they show no sign of intelligence. This is not surprising because our present computers are less complex than the brain of an earthworm, a species not noted for its intellectual powers. But computers roughly obey a version of Moore’s Law, which says that their speed and complexity double every eighteen months. It is one of these exponential growths that clearly cannot continue indefinitely, and indeed it has already begun to slow. However, the rapid pace of improvement will probably continue until computers have a similar complexity to the human brain. Some people say that computers can never show true intelligence, whatever that may be. But it seems to me that if very complicated chemical molecules can operate in humans to make them intelligent, then equally complicated electronic circuits can also make computers act in an intelligent way. And if they are intelligent they can presumably design computers that have even greater complexity and intelligence.
This is why I don’t believe the science-fiction picture of an advanced but constant future. Instead, I expect complexity to increase at a rapid rate, in both the biological and the electronic spheres. Not much of this will happen in the next hundred years, which is all we can reliably predict. But by the end of the next millennium, if we get there, the change will be fundamental.
Lincoln Steffens once said, “I have seen the future and it works.” He was actually talking about the Soviet Union, which we now know didn’t work very well. Nevertheless, I think the present world order has a future, but it will be very different.
What is the biggest threat to the future of this planet?
An asteroid collision would be—a threat against which we have no defence. But the last big such asteroid collision was about sixty-six million years ago and killed the dinosaurs. A more immediate danger is runaway climate change. A rise in ocean temperature would melt the ice caps and cause the release of large amounts of carbon dioxide. Both effects could make our climate like that of Venus with a temperature of 250 degrees centigrade (482 degrees Fahrenheit).
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SHOULD WE COLONISE SPACE?
Why should we go into space? What is the justification for spending all that effort and money on getting a few lumps of moon rock? Aren’t there better causes here on Earth? The obvious answer is because it’s there, all around us. Not to leave planet Earth would be like castaways on a desert island not trying to escape. We need to explore the solar system to find out where humans could live.
In a way, the situation is like that in Europe before 1492. People might well have argued that it was a waste of money to send Columbus on a wild goose chase. Yet the discovery of the New World made a profound difference to the Old. Just think, we wouldn’t have had the Big Mac or KFC. Spreading out into space will have an even greater effect. It will completely change the future of the human race, and maybe determine whether we have any future at all. It won’t solve any of our immediate problems on planet Earth, but it will give us a new perspective on them and cause us to look outwards rather than inwards. Hopefully, it will unite us to face the
common challenge.
This would be a long-term strategy, and by long term I mean hundreds or even thousands of years. We could have a base on the Moon within thirty years, reach Mars in fifty years and explore the moons of the outer planets in 200 years. By reach, I mean in spacecraft with humans aboard. We have already driven rovers on Mars and landed a probe on Titan, a moon of Saturn, but if we are considering the future of the human race we have to go there ourselves.
Going into space won’t be cheap, but it would take only a small proportion of world resources. NASA’s budget has remained roughly constant in real terms since the time of the Apollo landings, but it has decreased from 0.3 per cent of US GDP in 1970 to about 0.1 per cent in 2017. Even if we were to increase the international budget twenty times, to make a serious effort to go into space, it would only be a small fraction of world GDP.
There will be those who argue that it would be better to spend our money solving the problems of this planet, like climate change and pollution, rather than wasting it on a possibly fruitless search for a new planet. I’m not denying the importance of fighting climate change and global warming, but we can do that and still spare a quarter of a per cent of world GDP for space. Isn’t our future worth a quarter of a per cent?
We thought space was worth a big effort in the 1960s. In 1962, President Kennedy committed the US to landing a man on the Moon by the end of the decade. On July 20, 1969, Buzz Aldrin and Neil Armstrong landed on the surface of the Moon. It changed the future of the human race. I was twenty-seven at the time, a researcher at Cambridge, and I missed it. I was at a meeting on singularities in Liverpool and listening to a lecture by René Thom on catastrophe theory when the landing took place. There was no catch-up TV in those days, and we didn’t have a television, but my son aged two described it to me.
Brief Answers to the Big Questions Page 11
