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Seven Will We Survive on Earth?

In January 2018, the Bulletin of the Atomic Scientists, a journal founded by some of the physicists who had worked on the Manhattan Project to produce the first atomic weapons, moved the Doomsday Clock, their measurement of the imminence of catastrophe—military or environmental—facing our planet, forward to two minutes to midnight.

The clock has an interesting history. It was started in 1947, at a time when the atomic age had only just begun. Robert Oppenheimer, the chief scientist for the Manhattan Project, said later of the first explosion of an atomic bomb two years earlier in July 1945, “We knew the world would not be the same. A few people laughed, a few people cried, most people were silent. I remembered the line from the Hindu scripture, the Bhagavad-Gita, ‘Now, I am become Death, the destroyer of worlds.’ ” In 1947, the clock was originally set at seven minutes to midnight. It is now closer to Doomsday than at any time since then, save in the early 1950s at the start of the Cold War. The clock and its movements are, of course, entirely symbolic but I feel compelled to point out that such an alarming warning from other scientists, prompted at least in part by the election of Donald Trump, must be taken seriously. Is the clock, and the idea that time is ticking or even running out for the human race, realistic or alarmist? Is its warning timely or time-wasting?

I have a very personal interest in time. Firstly, my bestselling book, and the main reason that I am known beyond the confines of the scientific community, was called A Brief History of Time. So some might imagine that I am an expert on time, although of course these days an expert is not necessarily a good thing to be. Secondly, as someone who at the age of twenty-one was told by their doctors that they had only five years to live, and who turned seventy-six in 2018, I am an expert on time in another sense, a much more personal one. I am uncomfortably, acutely aware of the passage of time, and have lived much of my life with a sense that the time that I have been granted is, as they say, borrowed.

It is without doubt the case that our world is more politically unstable than at any time in my memory. Large numbers of people feel left behind both economically and socially. As a result, they are turning to populist—or at least popular—politicians who have limited experience of government and whose ability to take calm decisions in a crisis has yet to be tested. So that would imply that a Doomsday Clock should be moved closer to a critical point, as the prospect of careless or malicious forces precipitating Armageddon grows.

The Earth is under threat from so many areas that it is difficult for me to be positive. The threats are too big and too numerous.

First, the Earth is becoming too small for us. Our physical resources are being drained at an alarming rate. We have presented our planet with the disastrous gift of climate change. Rising temperatures, reduction of the polar ice caps, deforestation, over-population, disease, war, famine, lack of water and decimation of animal species; these are all solvable but so far have not been solved.

Global warming is caused by all of us. We want cars, travel and a better standard of living. The trouble is, by the time people realise what is happening, it may be too late. As we stand on the brink of a Second Nuclear Age and a period of unprecedented climate change, scientists have a special responsibility, once again, to inform the public and to advise leaders about the perils that humanity faces. As scientists, we understand the dangers of nuclear weapons, and their devastating effects, and we are learning how human activities and technologies are affecting climate systems in ways that may forever change life on Earth. As citizens of the world, we have a duty to share that knowledge, and to alert the public to the unnecessary risks that we live with every day. We foresee great peril if governments and societies do not take action now, to render nuclear weapons obsolete and to prevent further climate change.

At the same time, many of those same politicians are denying the reality of man-made climate change, or at least the ability of man to reverse it, just at the moment that our world is facing a series of critical environmental crises. The danger is that global warming may become self-sustaining, if it has not become so already. The melting of the Arctic and Antarctic ice caps reduces the fraction of solar energy reflected back into space, and so increases the temperature further. Climate change may kill off the Amazon and other rainforests and so eliminate one of the main ways in which carbon dioxide is removed from the atmosphere. The rise in sea temperature may trigger the release of large quantities of carbon dioxide. Both these phenomena would increase the greenhouse effect, and so exacerbate global warming. Both effects could make our climate like that of Venus: boiling hot and raining sulphuric acid, with a temperature of 250 degrees centigrade (482 degrees Fahrenheit). Human life would be unsustainable. We need to go beyond the Kyoto Protocol, the international agreement adopted in 1997, and cut carbon emissions now. We have the technology. We just need the political will.

We can be an ignorant, unthinking lot. When we have reached similar crises in our history, there has usually been somewhere else to colonise. Columbus did it in 1492 when he discovered the New World. But now there is no new world. No Utopia around the corner. We are running out of space and the only places to go to are other worlds.

The universe is a violent place. Stars engulf planets, supernovae fire lethal rays across space, black holes bump into each other and asteroids hurtle around at hundreds of miles a second. Granted, these phenomena do not make space sound very inviting, but these are the very reasons why we should venture into space instead of staying put. An asteroid collision would be something against which we have no defence. The last big such collision with us was about sixty-six million years ago and that is thought to have killed the dinosaurs, and it will happen again. This is not science fiction; it is guaranteed by the laws of physics and probability.

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 macro-molecules 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).