Brief Answers To The Big Questions Quotes

We have finally found something that doesn’t have a cause, because there was no time for a cause to exist in. For me this means that there is no possibility of a creator, because there is no time for a creator to have existed in.

Be brave, be curious, be determined, overcome the odds. It can be done

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.

The human race does not have a very good record of intelligent behaviour.

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.

While there’s life, there is hope.

I have spent my life travelling across the universe, inside my mind.

No matter how powerful a computer you have, if you put lousy data in you will get lousy predictions out.

Let us fight for every woman and every man to have the opportunity to live healthy, secure lives, full of opportunity and love. We are all time travellers, journeying together into the future. But let us work together to make that future a place we want to visit.

I am very aware of the preciousness of time. Seize the moment. Act now.

there are lots of things you want to do before your life is over.

As a father, I would try to instill the importance of asking questions, always.

Why are we so worried about artificial intelligence? Surely humans are always able to pull the plug? People asked a computer, ‘Is there a God?’ And the computer said, ‘There is now,’ and fused the plug.

When you are faced with the possibility of an early death, it makes you realise that there are lots of things you want to do before your life is over.

Be brave, be curious, be determined, overcome the odds. It can be done.

If you believe in science, like I do, you believe that there are certain laws that are always obeyed. If you like, you can say the laws are the work of God, but that is more a definition of God than a proof of his existence.

I think that when we die we return to dust. But there’s a sense in which we live on, in our influence, and in our genes that we pass on to our children. We have this one life to appreciate the grand design of the universe, and for that I am extremely grateful.

I will never be as brave as him—I’m not by nature a particularly courageous person—but he showed me that I could try. And that trying might turn out to be the most important part of courage.

And one final point—we never really know where the next great scientific discovery will come from, nor who will make it. Opening up the thrill and wonder of scientific discovery, creating innovative and accessible ways to reach out to the widest young audience possible, greatly increases the chances of finding and inspiring the new Einstein. Wherever she might be.

So Hamlet was quite right. We could be bounded in a nutshell and count ourselves kings of infinite space.

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 may life 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.

Let us fight for every woman and every man to have the opportunity to live healthy, secure lives, full of opportunity and love. We are all time travellers, journeying together into the future. But let us work together to make that future a place we want to visit. Be brave, be curious, be determined, overcome the odds. It can be done.

People want answers to the big questions, like why we are here. They don’t expect the answers to be easy, so they are prepared to struggle a bit. When people ask me if a God created the universe, I tell them that the question itself makes no sense. Time didn’t exist before the Big Bang so there is no time for God to make the universe in. It’s like asking for directions to the edge of the Earth—the Earth is a sphere that doesn’t have an edge, so looking for it is a futile exercise. Do I have faith? We are each free to believe what we want, and it’s my view that the simplest explanation is that there is no God. No one created the universe and no one directs our fate. This leads me to a profound realisation: there is probably no heaven and afterlife either. I think belief in an afterlife is just wishful thinking. There is no reliable evidence for it, and it flies in the face of everything we know in science. I think that when we die we return to dust. But there’s a sense in which we live on, in our influence, and in our genes that we pass on to our children. We have this one life to appreciate the grand design of the universe, and for that I am extremely grateful.

You can’t get to a time before the Big Bang because there was no time before the Big Bang. We have finally found something that doesn’t have a cause, because there was no time for a cause to exist in. For me this means that there is no possibility of a creator, because there is no time for a creator to have existed in.

The universe is a machine governed by principles or laws – laws that can be understood by the human mind.

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.

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.

I hope for the best. I have to. We have no other option.

intelligent life exists somewhere else than on Earth, would it be similar to the forms we know, or different? Is there intelligent life on Earth?

famous equation, E = mc2. So, if there’s

Not only is it important to ask questions and find the answers, as a scientist I felt obligated to communicate with the world what we were learning.

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.

When you look at the vast size of the universe, and how insignificant and accidental human life is in it, that seems most implausible.

I told him never to be afraid to come up with an idea or a hypothesis no matter how daft (his words not mine) it might seem.

Maybe it says something about human nature that the only form of life we have created so far is purely destructive.

In short, the advent of super-intelligent AI would be either the best or the worst thing ever to happen to humanity. The real risk with AI isn’t malice but competence. A super-intelligent AI will be extremely good at accomplishing its goals, and if those goals aren’t aligned with ours we’re in trouble.

The human mind is an incredible thing. It can conceive of the magnificence of the heavens and the intricacies of the basic components of matter. Yet for each mind to achieve its full potential, it needs a spark. The spark of enquiry and wonder.

I have led an extraordinary life on this planet, while at the same time travelling across the universe by using my mind and the laws of physics. I have been to the furthest reaches of our galaxy, travelled into a black hole and gone back to the beginning of time. On Earth, I have experienced highs and lows, turbulence and peace, success and suffering. I have been rich and poor, I have been able-bodied and disabled. I have been praised and criticised, but never ignored. I have been enormously privileged, through my work, in being able to contribute to our understanding of the universe. But it would be an empty universe indeed if it were not for the people I love, and who love me. Without them, the wonder of it all would be lost on me.

Science is increasingly answering questions that used to be the province of religion. Religion was an early attempt to answer the questions we all ask: why are we here, where did we come from? Long ago, the answer was almost always the same: gods made everything. The world was a scary place, so even people as tough as the Vikings believed in supernatural beings to make sense of natural phenomena like lightning, storms or eclipses. 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.

I have led an extraordinary life on this planet, while at the same time travelling across the universe by using my mind and the laws of physics. I have been to the furthest reaches of our galaxy, travelled into a black hole and gone back to the beginning of time.

In Britain, people don’t seem too worried about a possible end twenty billion years in the future. You can do quite a lot of eating, drinking and being merry before that.

real science can be far stranger than science fiction, and much more satisfying.

If you look behind every exceptional person there is an exceptional teacher. When each of us thinks about what we can do in life, chances are we can do it because of a teacher.

One could define God as the embodiment of the laws of nature.

I think it is legitimate to take a broader view and include externally transmitted information, as well as DNA, in the evolution of the human race.

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.

We see the unity, and not the divisions. It is such a simple image with a compelling message; one planet, one human race.

Therefore, a human is equivalent to about fifty Harry Potter books, and a major national library can contain about five million books – or about ten trillion bits.

To do research on the fundamental laws that govern the universe would require a commitment of time that most people don’t have; the

After my expectations had been reduced to zero, every new day became a bonus, and I began to appreciate everything I did have. While there’s life, there is hope.

We foresee great peril if governments and societies do not take action now, to render nuclear weapons obsolete and to prevent further climate change.

One of the great revelations of the space age has been the perspective it has given humanity on ourselves. 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.

according to the laws of nature concerning gravity and motion – laws that are among the oldest in science – space itself is a vast store of negative energy. Enough to ensure that everything adds up to zero.

I would like to speculate a little on the development of life in the universe, and in particular on the development of intelligent life. I shall take this to include the human race, even though much of its behaviour throughout history has been pretty stupid and not calculated to aid the survival of the species.

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.

If one believed that the universe had a beginning, the obvious question was what happened before the beginning? What was God doing before He made the world? Was He preparing Hell for people who asked such questions?

The problem is, most people believe that real science is too difficult and complicated for them to understand. But I don’t think this is the case. To do research on the fundamental laws that govern the universe would require a commitment of time that most people don’t have; the world would soon grind to a halt if we all tried to do theoretical physics. But most people can understand and appreciate the basic ideas if they are presented in a clear way without equations, which I believe is possible and which is something I have enjoyed trying to do throughout my life.

You were supposed to be brilliant without effort, or to accept your limitations and get a fourth-class degree. I took this as an invitation to very little. I'm not proud of this, I'm just describing my attitude at that time, shared by most of my fellow students.

I don’t believe in boundaries, either for what we can do in our personal lives or for what life and intelligence can accomplish in our universe. We stand at a threshold of important discoveries in all areas of science. Without doubt, our world will change enormously in the next fifty years. We will find out what happened at the Big Bang. We will come to understand how life began on Earth. We may even discover whether life exists elsewhere in the universe. While the chances of communicating with an intelligent extra-terrestrial species may be slim, the importance of such a discovery means we must not give up trying. We will continue to explore our cosmic habitat, sending robots and humans into space. We cannot continue to look inwards at ourselves on a small and increasingly polluted and overcrowded planet. Through scientific endeavour and technological innovation, we must look outwards to the wider universe, while also striving to fix the problems on Earth. And I am optimistic that we will ultimately create viable habitats for the human race on other planets. We will transcend the Earth and learn to exist in space. This is not the end of the story, but just the beginning of what I hope will be billions of years of life flourishing in the cosmos. And one final point—we never really know where the next great scientific discovery will come from, nor who will make it. Opening up the thrill and wonder of scientific discovery, creating innovative and accessible ways to reach out to the widest young audience possible, greatly increases the chances of finding and inspiring the new Einstein. Wherever she might be. 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.

The assertion that religion is a tool for preserving social order and for organising large-scale cooperation may vex many people for whom it represents first and foremost a spiritual path. However, just as the gap between religion and science is smaller than we commonly think, so the gap between religion and spirituality is much bigger. Religion is a deal, whereas spirituality is a journey. Religion gives a complete description of the world, and offers us a well-defined contract with predetermined goals. ‘God exists. He told us to behave in certain ways. If you obey God, you’ll be admitted to heaven. If you disobey Him, you’ll burn in hell.’ The very clarity of this deal allows society to define common norms and values that regulate human behaviour. Spiritual journeys are nothing like that. They usually take people in mysterious ways towards unknown destinations. The quest usually begins with some big question, such as who am I? What is the meaning of life? What is good? Whereas many people just accept the ready-made answers provided by the powers that be, spiritual seekers are not so easily satisfied. They are determined to follow the big question wherever it leads, and not just to places you know well or wish to visit. Thus for most people, academic studies are a deal rather than a spiritual journey, because they take us to a predetermined goal approved by our elders, governments and banks.

My investigations revealed a deep and previously unsuspected relationship between gravity and thermodynamics, the science of heat, and resolved a paradox that had been argued over for thirty years without much progress: how could the radiation left over from a shrinking black hole carry all of the information about what made the black hole? I discovered that information is not lost, but it is not returned in a useful way—like burning an encyclopedia but retaining the smoke and ashes.

DNA passes the blueprints of life between generations. Ever more complex life forms input information from sensors such as eyes and ears and process the information in brains or other systems to figure out how to act and then act on the world, by outputting information to muscles, for example. As some point during our 13.8 billion years of cosmic history, something beautiful happened. This information processing got so intelligent that life forms became conscious. Our universe has now awoken, becoming aware of itself. I regard it a triumph that we, who are ourselves mere stardust, have come to such a detailed understanding of the universe in which we live.

How will we feed an ever-growing population? Provide clean water, generate renewable energy, prevent and cure disease and slow down global climate change? I hope that science and technology will provide the answers to these questions, but it will take people, human beings with knowledge and understanding, to implement these solutions.

When I was in the Far East, I was asked not to mention the Big Crunch, because of the effect it might have on the market. But the markets crashed, so maybe the story got out somehow. In Britain, people don't seem too worried about a possible end twenty billion years in the future. You can do quite a lot of eating, drinking and being merry before that.

from ourselves. I am convinced that humans need to leave Earth. If we stay, we risk being annihilated.

By contrast, there are about 50,000 new books published in the English language each year, containing of the order of a hundred billion bits of information. Of course, the great majority of this information is garbage and no use to any form of life. But, even so, the rate at which useful information can be added is millions, if not billions, higher than with DNA.

Is there any point in hosting a party for time travellers? Would you hope anyone would turn up? In 2009 I held a party for time travellers in my college, Gonville and Caius in Cambridge, for a film about time travel. To ensure that only genuine time travellers came, I didn't sent out the invitations until after the party. On the day of the party, I sat in college hoping, but no one came.

Is there any point in hosting a party for time travellers? Would you hope anyone would turn up? In 2009 I held a party for time travellers in my college, Gonville and Caius in Cambridge, for a film about time travel. To ensure that only genuine time travellers came, I didn’t send out the invitations until after the party. On the day of the party, I sat in college hoping, but no one came. I was disappointed, but not surprised, because I had shown that if general relativity is correct and energy density is positive, time travel is not possible. I would have been delighted if one of my assumptions had turned out to be wrong.

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.

Since we know the universe itself was once very small—perhaps smaller than a proton—this means something quite remarkable. It means the universe itself, in all its mind-boggling vastness and complexity, could simply have popped into existence without violating the known laws of nature. From that moment on, vast amounts of energy were released as space itself expanded—a place to store all the negative energy needed to balance the books.

When we invented fire, we messed up repeatedly, then invented the fire extinguisher. With more powerful technologies such as nuclear weapons, synthetic biology and strong artificial intelligence, we should instead plan ahead and aim to get things right the first time, because it may be the only chance we will get. 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.

As I was growing up in England after the Second World War, it was a time of austerity. We were told that you never get something for nothing. But now, after a lifetime of work, I think that actually you can get a whole universe for free.

The human mind is an incredible thing. It can conceive of the magnificence of the heavens and the intricacies of the basic components of matter. Yet for each mind to achieve its full potential, it needs a spark. The spark of enquiry and wonder. Often that spark comes from a teacher. Allow me to explain. I wasn’t the easiest person to teach, I was slow to learn to read and my handwriting was untidy. But when I was fourteen my teacher at my school in St Albans, Dikran Tahta, showed me how to harness my energy and encouraged me to think creatively about mathematics. He opened my eyes to maths as the blueprint of the universe itself. If you look behind every exceptional person there is an exceptional teacher. When each of us thinks about what we can do in life, chances are we can do it because of a teacher. [...] The basis for the future of education must lie in schools and inspiring teachers. But schools can only offer an elementary framework where sometimes rote-learning, equations and examinations can alienate children from science. Most people respond to a qualitative, rather than a quantitative, understanding, without the need for complicated equations. Popular science books and articles can also put across ideas about the way we live. However, only a small percentage of the population read even the most successful books. Science documentaries and films reach a mass audience, but it is only one-way communication.

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.

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.

The laws of nature are a description of how things actually work in the past, present and future. In tennis, the ball always goes exactly where they say it will. And there are many other laws at work here too. They govern everything that is going on, from how the energy of the shot is produced in the players’ muscles to the speed at which the grass grows beneath their feet. But what’s really important is that these physical laws, as well as being unchangeable, are universal. They apply not just to the flight of a ball, but to the motion of a planet, and everything else in the universe. Unlike laws made by humans, the laws of nature cannot be broken—that’s why they are so powerful and, when seen from a religious standpoint, controversial too. If you accept, as I do, that the laws of nature are fixed, then it doesn’t take long to ask: what role is there for God? This is a big part of the contradiction between science and religion, and although my views have made headlines, it is actually an ancient conflict. One could define God as the embodiment of the laws of nature. However, this is not what most people would think of as God. They mean a human-like being, with whom one can have a personal relationship. When you look at the vast size of the universe, and how insignificant and accidental human life is in it, that seems most implausible.

I use the word “God” in an impersonal sense, like Einstein did, for the laws of nature, so knowing the mind of God is knowing the laws of nature. My prediction is that we will know the mind of God by the end of this century. The one remaining area that religion can now lay claim to is the origin of the universe, but even here science is making progress and should soon provide a definitive answer to how the universe began. I published a book that asked if God created the universe, and that caused something of a stir. People got upset that a scientist should have anything to say on the matter of religion. I have no desire to tell anyone what to believe, but for me asking if God exists is a valid question for science. After all, it is hard to think of a more important, or fundamental, mystery than what, or who, created and controls the universe. I think the universe was spontaneously created out of nothing, according to the laws of science. The basic assumption of science is scientific determinism. The laws of science determine the evolution of the universe, given its state at one time. These laws may, or may not, have been decreed by God, but he cannot intervene to break the laws, or they would not be laws. That leaves God with the freedom to choose the initial state of the universe, but even here it seems there may be laws. So God would have no freedom at all.

And one final point—we never really know where the next great scientific discovery will come from, nor who will make it. Opening up the thrill and wonder of scientific discovery, creating innovative and accessible ways to reach out to the widest young audience possible, greatly increases the chances of finding and inspiring the new Einstein. Wherever she might be. 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

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.

This “Hawking temperature” of a black hole and its “Hawking radiation” (as they came to be called) were truly radical—perhaps the most radical theoretical physics discovery in the second half of the twentieth century. They opened our eyes to profound connections between general relativity (black holes), thermodynamics (the physics of heat) and quantum physics (the creation of particles where before there were none). For example, they led Stephen to prove that a black hole has entropy, which means that somewhere inside or around the black hole there is enormous randomness. He deduced that the amount of entropy (the logarithm of the hole’s amount of randomness) is proportional to the hole’s surface area. His formula for the entropy is engraved on Stephen’s memorial stone at Gonville and Caius College in Cambridge, where he worked. For the past forty-five years, Stephen and hundreds of other physicists have struggled to understand the precise nature of a black hole’s randomness. It is a question that keeps on generating new insights about the marriage of quantum theory with general relativity—that is, about the ill-understood laws of quantum gravity.

As we travel back in time towards the moment of the Big Bang, the universe gets smaller and smaller and smaller, until it finally comes to a point where the whole universe is a space so small that it is in effect a single infinitesimally small, infinitesimally dense black hole. And just as with modern-day black holes, floating around in space, the laws of nature dictate something quite extraordinary. They tell us that here too time itself must come to a stop. You can’t get to a time before the Big Bang because there was no time before the Big Bang. We have finally found something that doesn’t have a cause, because there was no time for a cause to exist in. For me this means that there is no possibility of a creator, because there is no time for a creator to have existed in.

The human mind is an incredible thing. It can conceive of the magnificence of the heavens and the intricacies of the basic components of matter. Yet for each mind to achieve its full potential, it needs a spark. The spark of enquiry and wonder. Often that spark comes from a teacher. Allow me to explain. I wasn’t the easiest person to teach, I was slow to learn to read and my handwriting was untidy. But when I was fourteen my teacher at my school in St Albans, Dikran Tahta, showed me how to harness my energy and encouraged me to think creatively about mathematics. He opened my eyes to maths as the blueprint of the universe itself. If you look behind every exceptional person there is an exceptional teacher. When each of us thinks about what we can do in life, chances are we can do it because of a teacher.

At the moment of the Big Bang, an entire universe came into existence, and with it space. It all inflated, just like a balloon being blown up. So where did all this energy and space come from? How does an entire universe full of energy, the awesome vastness of space and everything in it, simply appear out of nothing? For some, this is where God comes back into the picture. It was God who created the energy and space. The Big Bang was the moment of creation. But science tells a different story. At the risk of getting myself into trouble, I think we can understand much more the natural phenomena that terrified the Vikings. We can even go beyond the beautiful symmetry of energy and matter discovered by Einstein. We can use the laws of nature to address the very origins of the universe, and discover if the existence of God is the only way to explain it.

But what lies ahead for those who are young now? I can say with confidence that their future will depend more on science and technology than any previous generation’s has done. They need to know about science more than any before them because it is part of their daily lives in an unprecedented way. Without speculating too wildly, there are trends we can see and emerging problems that we know must be dealt with, now and into the future. Among the problems I count global warming, finding space and resources for the massive increase in the Earth’s human population, rapid extinction of other species, the need to develop renewable energy sources, the degradation of the oceans, deforestation and epidemic diseases—just to name a few. There are also the great inventions of the future, which will revolutionise the ways we live, work, eat, communicate and travel. There is such enormous scope for innovation in every area of life. This is exciting. We could be mining rare metals on the Moon, establishing a human outpost on Mars and finding cures and treatments for conditions which currently offer no hope. The huge questions of existence still remain unanswered—how did life begin on Earth? What is consciousness? Is there anyone out there or are we alone in the universe? These are questions for the next generation to work on.

The world has been changing even faster as people, devices and information are increasingly connected to each other. Computational power is growing and quantum computing is quickly being realised. This will revolutionise artificial intelligence with exponentially faster speeds. It will advance encryption. Quantum computers will change everything, even human biology. There is already one technique to edit DNA precisely, called CRISPR. The basis of this genome-editing technology is a bacterial defence system. It can accurately target and edit stretches of genetic code. The best intention of genetic manipulation is that modifying genes would allow scientists to treat genetic causes of disease by correcting gene mutations. There are, however, less noble possibilities for manipulating DNA. How far we can go with genetic engineering will become an increasingly urgent question. We can’t see the possibilities of curing motor neurone diseases—like my ALS—without also glimpsing its dangers. Intelligence is characterised as the ability to adapt to change. Human intelligence is the result of generations of natural selection of those with the ability to adapt to changed circumstances. We must not fear change. We need to make it work to our advantage. We all have a role to play in making sure that we, and the next generation, have not just the opportunity but the determination to engage fully with the study of science at an early level, so that we can go on to fulfil our potential and create a better world for the whole human race. We need to take learning beyond a theoretical discussion of how AI should be and to make sure we plan for how it can be. We all have the potential to push the boundaries of what is accepted, or expected, and to think big. We stand on the threshold of a brave new world. It is an exciting, if precarious, place to be, and we are the pioneers. When we invented fire, we messed up repeatedly, then invented the fire extinguisher. With more powerful technologies such as nuclear weapons, synthetic biology and strong artificial intelligence, we should instead plan ahead and aim to get things right the first time, because it may be the only chance we will get. 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.

On September 14, 2015, the LIGO gravitational-wave detectors (built by a 1,000-person project that Rai and I and Ronald Drever co-founded, and Barry Barish organised, assembled and led) registered their first gravitational waves. By comparing the wave patterns with predictions from computer simulations, our team concluded that the waves were produced when two heavy black holes, 1.3 billion light years from Earth, collided. This was the beginning of gravitational-wave astronomy. Our team had achieved, for gravitational waves, what Galileo achieved for electromagnetic waves. I am confident that, over the coming several decades, the next generation of gravitational-wave astronomers will use these waves not only to test Stephen’s laws of black hole physics, but also to detect and monitor gravitational waves from the singular birth of our universe, and thereby test Stephen’s and others’ ideas about how our universe came to be.

One day, I hope we will know the answers to all these questions. But there are other challenges, other big questions on the planet which must be answered, and these will also need a new generation who are interested and engaged, and have an understanding of science. How will we feed an ever-growing population? Provide clean water, generate renewable energy, prevent and cure disease and slow down global climate change? I hope that science and technology will provide the answers to these questions, but it will take people, human beings with knowledge and understanding, to implement these solutions. Let us fight for every woman and every man to have the opportunity to live healthy, secure lives, full of opportunity and love. We are all time travellers, journeying together into the future. But let us work together to make that future a place we want to visit. Be brave, be curious, be determined, overcome the odds. It can be done.

I have led an extraordinary life on this planet, while at the same time travelling across the universe by using my mind and the laws of physics. I have been to the furthest reaches of our galaxy, travelled into a black hole and gone back to the beginning of time. On Earth, I have experienced highs and lows, turbulence and peace, success and suffering. I have been rich and poor, I have been able-bodied and disabled. I have been praised and criticised, but never ignored. I have been enormously privileged, through my work, in being able to contribute to our understanding of the universe. But it would be an empty universe indeed if it were not for the people I love, and who love me. Without them, the wonder of it all would be lost on me. And at the end of all this, the fact that we humans, who are ourselves mere collections of fundamental particles of nature, have been able to come to an understanding of the laws governing us, and our universe, is a great triumph. I want to share my excitement about these big questions and my enthusiasm about this quest.

People have always wanted answers to the big questions. Where did we come from? How did the universe begin? What is the meaning and design behind it all? Is there anyone out there? The creation accounts of the past now seem less relevant and credible. They have been replaced by a variety of what can only be called superstitions, ranging from New Age to Star Trek. But real science can be far stranger than science fiction, and much more satisfying. I am a scientist. And a scientist with a deep fascination with physics, cosmology, the universe and the future of humanity. I was brought up by my parents to have an unwavering curiosity and, like my father, to research and try to answer the many questions that science asks us. I have spent my life travelling across the universe, inside my mind. Through theoretical physics, I have sought to answer some of the great questions. At one point, I thought I would see the end of physics as we know it, but now I think the wonder of discovery will continue long after I am gone. We are close to some of these answers, but we are not there yet.

In conclusion, I return to Einstein. If we find a planet in the Alpha Centauri system, its image, captured by a camera travelling at a fifth of light speed, will be slightly distorted due to the effects of special relativity. It would be the first time a spacecraft has flown fast enough to see such effects. In fact, Einstein’s theory is central to the whole mission. Without it we would have neither lasers nor the ability to perform the calculations necessary for guidance, imaging and data transmission over twenty-five trillion miles at a fifth of light speed. We can see a pathway between that sixteen-year-old boy dreaming of riding on a light beam and our own dream, which we are planning to turn into a reality, of riding our own light beam to the stars. We are standing at the threshold of a new era. Human colonisation on other planets is no longer science fiction. It can be science fact. The human race has existed as a separate species for about two million years. Civilisation began about 10,000 years ago, and the rate of development has been steadily increasing. If humanity is to continue for another million years, our future lies in boldly going where no one else has gone before. I hope for the best. I have to. We have no other option.

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.

During our glorious year of 1974–5, while I was dithering over gravitational waves, and Stephen was leading our merged group in black hole research, Stephen himself had an insight even more radical than his discovery of Hawking radiation. He gave a compelling, almost airtight proof that, when a black hole forms and then subsequently evaporates away completely by emitting radiation, the information that went into the black hole cannot come back out. Information is inevitably lost. This is radical because the laws of quantum physics insist unequivocally that information can never get totally lost. So, if Stephen was right, black holes violate a most fundamental quantum mechanical law. How could this be? The black hole’s evaporation is governed by the combined laws of quantum mechanics and general relativity—the ill-understood laws of quantum gravity; and so, Stephen reasoned, the fiery marriage of relativity and quantum physics must lead to information destruction. The great majority of theoretical physicists find this conclusion abhorrent. They are highly sceptical. And so, for forty-four years they have struggled with this so-called information-loss paradox. It is a struggle well worth the effort and anguish that have gone into it, since this paradox is a powerful key for understanding the quantum gravity laws. Stephen himself, in 2003, found a way that information might escape during the hole’s evaporation, but that did not quell theorists’ struggles. Stephen did not prove that the information escapes, so the struggle continues. In my eulogy for Stephen, at the interment of his ashes at Westminster Abbey, I memorialised that struggle with these words: “Newton gave us answers. Hawking gave us questions. And Hawking’s questions themselves keep on giving, generating breakthroughs decades later. When ultimately we master the quantum gravity laws, and comprehend fully the birth of our universe, it may largely be by standing on the shoulders of Hawking.

Despite the complexity and variety of the universe, it turns out that to make one you need just three ingredients. Let’s imagine that we could list them in some kind of cosmic cookbook. So what are the three ingredients we need to cook up a universe? The first is matter—stuff that has mass. Matter is all around us, in the ground beneath our feet and out in space. Dust, rock, ice, liquids. Vast clouds of gas, massive spirals of stars, each containing billions of suns, stretching away for incredible distances. The second thing you need is energy. Even if you’ve never thought about it, we all know what energy is. Something we encounter every day. Look up at the Sun and you can feel it on your face: energy produced by a star ninety-three million miles away. Energy permeates the universe, driving the processes that keep it a dynamic, endlessly changing place. So we have matter and we have energy. The third thing we need to build a universe is space. Lots of space. You can call the universe many things—awesome, beautiful, violent—but one thing you can’t call it is cramped. Wherever we look we see space, more space and even more space. Stretching in all directions. It’s enough to make your head spin. So where could all this matter, energy and space come from? We had no idea until the twentieth century. The answer came from the insights of one man, probably the most remarkable scientist who has ever lived. His name was Albert Einstein. Sadly I never got to meet him, since I was only thirteen when he died. Einstein realised something quite extraordinary: that two of the main ingredients needed to make a universe—mass and energy—are basically the same thing, two sides of the same coin if you like. His famous equation E = mc2 simply means that mass can be thought of as a kind of energy, and vice versa. So instead of three ingredients, we can now say that the universe has just two: energy and space. So where did all this energy and space come from? The answer was found after decades of work by scientists: space and energy were spontaneously invented in an event we now call the Big Bang.

This was a golden age, in which we solved most of the major problems in black hole theory even before there was any observational evidence for black holes. In fact, we were so successful with the classical general theory of relativity that I was at a bit of a loose end in 1973 after the publication with George Ellis of our book The Large Scale Structure of Space–Time. My work with Penrose had shown that general relativity broke down at singularities, so the obvious next step would be to combine general relativity—the theory of the very large—with quantum theory—the theory of the very small. In particular, I wondered, can one have atoms in which the nucleus is a tiny primordial black hole, formed in the early universe? My investigations revealed a deep and previously unsuspected relationship between gravity and thermodynamics, the science of heat, and resolved a paradox that had been argued over for thirty years without much progress: how could the radiation left over from a shrinking black hole carry all of the information about what made the black hole? I discovered that information is not lost, but it is not returned in a useful way—like burning an encyclopedia but retaining the smoke and ashes. To answer this, I studied how quantum fields or particles would scatter off a black hole. I was expecting that part of an incident wave would be absorbed, and the remainder scattered. But to my great surprise I found there seemed to be emission from the black hole itself. At first, I thought this must be a mistake in my calculation. But what persuaded me that it was real was that the emission was exactly what was required to identify the area of the horizon with the entropy of a black hole. This entropy, a measure of the disorder of a system, is summed up in this simple formula which expresses the entropy in terms of the area of the horizon, and the three fundamental constants of nature, c, the speed of light, G, Newton’s constant of gravitation, and ħ, Planck’s constant. The emission of this thermal radiation from the black hole is now called Hawking radiation and I’m proud to have discovered it.

On September 14, 2015, the LIGO gravitational-wave detectors (built by a 1,000-person project that Rai and I and Ronald Drever co-founded, and Barry Barish organised, assembled and led) registered their first gravitational waves. By comparing the wave patterns with predictions from computer simulations, our team concluded that the waves were produced when two heavy black holes, 1.3 billion light years from Earth, collided. This was the beginning of gravitational-wave astronomy. Our team had achieved, for gravitational waves, what Galileo achieved for electromagnetic waves. I am confident that, over the coming several decades, the next generation of gravitational-wave astronomers will use these waves not only to test Stephen’s laws of black hole physics, but also to detect and monitor gravitational waves from the singular birth of our universe, and thereby test Stephen’s and others’ ideas about how our universe came to be. During our glorious year of 1974–5, while I was dithering over gravitational waves, and Stephen was leading our merged group in black hole research, Stephen himself had an insight even more radical than his discovery of Hawking radiation. He gave a compelling, almost airtight proof that, when a black hole forms and “and then subsequently evaporates away completely by emitting radiation, the information that went into the black hole cannot come back out. Information is inevitably lost.

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. I don’t believe in boundaries, either for what we can do in our personal lives or for what life and intelligence can accomplish in our universe. We stand at a threshold of important discoveries in all areas of science. Without doubt, our world will change enormously in the next fifty years. We will find out what happened at the Big Bang. We will come to understand how life began on Earth. We may even discover whether life exists elsewhere in the universe. While the chances of communicating with an intelligent extra-terrestrial species may be slim, the importance of such a discovery means we must not give up trying. We will continue to explore our cosmic habitat, sending robots and humans into space. We cannot continue to look inwards at ourselves on a small and increasingly polluted and overcrowded planet. Through scientific endeavour and technological innovation, we must look outwards to the wider universe, while also striving to fix the problems on Earth. And I am optimistic that we will ultimately create viable habitats for the human race on other planets. We will transcend the Earth and learn to exist in space. This is not the end of the story, but just the beginning of what I hope will be billions of years of life flourishing in the cosmos. And one final point—we never really know where the next great scientific discovery will come from, nor who will make it. Opening up the thrill and wonder of scientific discovery, creating innovative and accessible ways to reach out to the widest young audience possible, greatly increases the chances of finding and inspiring the new Einstein. Wherever she might be. 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.

A century ago, Albert Einstein revolutionised our understanding of space, time, energy and matter. We are still finding awesome confirmations of his predictions, like the gravitational waves observed in 2016 by the LIGO experiment. 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. A key element for Einstein was imagination. Many of his discoveries came from his ability to reimagine the universe through thought experiments. At the age of sixteen, when he visualised riding on a beam of light, he realised that from this vantage light would appear as a frozen wave. That image ultimately led to the theory of special relativity. One hundred years later, physicists know far more about the universe than Einstein did. Now we have greater tools for discovery, such as particle accelerators, supercomputers, space telescopes and experiments such as the LIGO lab’s work on gravitational waves. Yet imagination remains our most powerful attribute. With it, we can roam anywhere in space and time. We can witness nature’s most exotic phenomena while driving in a car, snoozing in bed or pretending to listen to someone boring at a party.

There are only two types of waves that can travel across the universe bringing us information about things far away: electromagnetic waves (which include light, X-rays, gamma rays, microwaves, radio waves…); and gravitational waves. Electromagnetic waves consist of oscillating electric and magnetic forces that travel at light speed. When they impinge on charged particles, such as the electrons in a radio or TV antenna, they shake the particles back and forth, depositing in the particles the information the waves carry. That information can then be amplified and fed into a loudspeaker or on to a TV screen for humans to comprehend. Gravitational waves, according to Einstein, consist of an oscillatory space warp: an oscillating stretch and squeeze of space. In 1972 Rainer (Rai) Weiss at the Massachusetts Institute of Technology had invented a gravitational-wave detector, in which mirrors hanging inside the corner and ends of an L-shaped vacuum pipe are pushed apart along one leg of the L by the stretch of space, and pushed together along the other leg by the squeeze of space. Rai proposed using laser beams to measure the oscillating pattern of this stretch and squeeze. The laser light could extract a gravitational wave’s information, and the signal could then be amplified and fed into a computer for human comprehension. The study of the universe with electromagnetic telescopes (electromagnetic astronomy) was initiated by Galileo, when he built a small optical telescope, pointed it at Jupiter and discovered Jupiter’s four largest moons. During the 400 years since then, electromagnetic astronomy has completely revolutionised our understanding of the universe.

The big question in cosmology in the early 1960s was did the universe have a beginning? Many scientists were instinctively opposed to the idea, because they felt that a point of creation would be a place where science broke down. One would have to appeal to religion and the hand of God to determine how the universe would start off. This was clearly a fundamental question, and it was just what I needed to complete my PhD thesis. Roger Penrose had shown that once a dying star had contracted to a certain radius, there would inevitably be a singularity, that is a point where space and time came to an end. Surely, I thought, we already knew that nothing could prevent a massive cold star from collapsing under its own gravity until it reached a singularity of infinite density. I realised that similar arguments could be applied to the expansion of the universe. In this case, I could prove there were singularities where space–time had a beginning. A eureka moment came in 1970, a few days after the birth of my daughter, Lucy. While getting into bed one evening, which my disability made a slow process, I realised that I could apply to black holes the casual structure theory I had developed for singularity theorems. If general relativity is correct and the energy density is positive, the surface area of the event horizon—the boundary of a black hole—has the property that it always increases when additional matter or radiation falls into it. Moreover, if two black holes collide and merge to form a single black hole, the area of the event horizon around the resulting black hole is greater than the sum of the areas of the event horizons around the original black holes.

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. I don’t believe in boundaries, either for what we can do in our personal lives or for what life and intelligence can accomplish in our universe. We stand at a threshold of important discoveries in all areas of science. Without doubt, our world will change enormously in the next fifty years. We will find out what happened at the Big Bang. We will come to understand how life began on Earth. We may even discover whether life exists elsewhere in the universe. While the chances of communicating with an intelligent extra-terrestrial species may be slim, the importance of such a discovery means we must not give up trying. We will continue to explore our cosmic habitat, sending robots and humans into space. We cannot continue to look inwards at ourselves on a small and increasingly polluted and overcrowded planet. Through scientific endeavour and technological innovation, we must look outwards to the wider universe, while also striving to fix the problems on Earth. And I am optimistic that we will ultimately create viable habitats for the human race on other planets. We will transcend the Earth and learn to exist in space. This is not the end of the story, but just the beginning of what I hope will be billions of years of life flourishing in the cosmos. And one final point—we never really know where the next great scientific discovery will come from, nor who will make it. Opening up the thrill and wonder of scientific discovery, creating innovative and accessible ways to reach out to the widest young audience possible, greatly increases the chances of finding and inspiring the new Einstein. Wherever she might be. 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.