Brief Answers to the Big Questions

by Stephen Hawking

When we see the Earth from space, we see ourselves as a whole. We see the unity, and not the divisions. It is such a simple image with a compelling message; one planet, one human race.

Nowadays, science provides better and more consistent answers, but people will always cling to religion, because it gives comfort, and they do not trust or understand science.

Now suppose we try to predict the future. Because we only know some combination of position and speed of a particle, we cannot make precise predictions about the future positions and speeds of particles. We can only assign a probability to particular combinations of positions and speeds. Thus there is a certain probability to a particular future of the universe. But now suppose we try to understand the past in the same way. Given the nature of the observations we can make now, all we can do is assign a probability to a particular history of the universe. Thus the universe must have many possible histories, each with its own probability. There is a history of the universe in which England win the World Cup again, though maybe the probability is low. This idea that the universe has multiple histories may sound like science fiction, but it is now accepted as science fact.

Einstein showed that the time and position at which one thought an event occurred depended on how one was moving. This meant that time and space were inextricably bound up with each other. The times that different observers would assign to events would agree if the observers were not moving relative to each other. But they would disagree more the faster their relative speed. So one can ask how fast does one need to go in order that the time for one observer should go backwards relative to the time of another observer. The answer is given in the following limerick: There was a young lady of Wight Who travelled much faster than light She departed one day In a relative way And arrived on the previous night. So all we need for time travel is a spaceship that will go faster than light. Unfortunately in the same paper Einstein showed that the rocket power needed to accelerate a spaceship got greater and greater the nearer it got to the speed of light. So it would take an infinite amount of power to accelerate past the speed of light.

In conclusion, rapid space travel and travel back in time can’t be ruled out according to our present understanding. They would cause great logical problems, so let’s hope there’s a Chronology Protection Law to prevent people going back and killing their parents. But science-fiction fans need not lose heart. There’s hope in M-theory.

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.

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, but with a temperature of 250 degrees Celsius. 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.

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.

In fact, the distance to Alpha Centauri is so great that to reach it in a human lifetime a spacecraft would have to carry fuel with roughly the mass of all the stars in the galaxy.

Used as a toolkit, AI can augment our existing intelligence to open up advances in every area of science and society. However, it will also bring dangers. While primitive forms of artificial intelligence developed so far have proved very useful, I fear the consequences of creating something that can match or surpass humans. The concern is that AI would take off on its own and redesign itself at an ever-increasing rate. Humans, who are limited by slow biological evolution, couldn’t compete and would be superseded. And in the future AI could develop a will of its own, a will that is in conflict with ours. Others believe that humans can command the rate of technology for a decently long time, and that the potential of AI to solve many of the world’s problems will be realised. Although I am well known as an optimist regarding the human race, I am not so sure.

In the near term, for example, world militaries are considering starting an arms race in autonomous-weapon systems that can choose and eliminate their own targets.

Whereas the short-term impact of AI depends on who controls it, the long-term impact depends on whether it can be controlled at all.

Our future is a race between the growing power of our technology and the wisdom with which we use it. Let’s make sure that wisdom wins.

When I think about ingenuity, Einstein springs to mind. Where did his ingenious ideas come from? A blend of qualities, perhaps: intuition, originality, brilliance. Einstein had the ability to look beyond the surface to reveal the underlying structure. He was undaunted by common sense, the idea that things must be the way they seemed. He had the courage to pursue ideas that seemed absurd to others. And this set him free to be ingenious, a genius of his time and every other.

when a civilisation reaches our stage of development it becomes unstable and destroys itself. We now have the technological power to destroy every living creature on Earth.

When I was growing up it was still acceptable – not to me but in social terms – to say that one was not interested in science and did not see the point in bothering with it. This is no longer the case. Let me be clear. I am not promoting the idea that all young people should grow up to be scientists. I do not see that as an ideal situation, as the world needs people with a wide variety of skills. But I am advocating that all young people should be familiar with and confident around scientific subjects, whatever they choose to do. They need to be scientifically literate, and inspired to engage with developments in science and technology in order to learn more.

A world where only a tiny super-elite are capable of understanding advanced science and technology and its applications would be, to my mind, a dangerous and limited one. I seriously doubt whether long-range beneficial projects such as cleaning up the oceans or curing diseases in the developing world would be given priority. Worse, we could find that technology is used against us and that we might have no power to stop it.

So remember to look up at the stars and not down at your feet. Try to make sense of what you see and wonder about what makes the universe exist. Be curious. And however difficult life may seem, there is always something you can do and succeed at. It matters that you don’t just give up. Unleash your imagination. Shape the future.