Brief Answers to the Big Questions

by Stephen Hawking

Stephen said he had enjoyed the film. He was moved by it, but famously he also stated that he thought there should have been more physics and fewer feelings. This is impossible to argue with.

(Over the next decade, Stephen and Roger, combining forces, would go on to prove, ever more convincingly, this singular beginning of time, and also prove ever more convincingly that the core of every black hole is inhabited by a singularity where time ends.)

When an object has energy of motion, nature usually finds a way to extract it.

The heavier the hole, the lower its temperature. A hole that weighs as much as the Sun has a temperature of 0.00000006 Kelvin, 0.06 millionths of a degree above absolute zero. The formula for calculating this temperature is now engraved on Stephen’s headstone in Westminster Abbey in London, where his ashes reside between those of Isaac Newton and Charles Darwin.

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.

“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.”

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

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

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.

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.

I hope that going forward, even when I am no longer here, people with power can show creativity, courage and leadership.

I was born exactly 300 years after the death of Galileo, and I would like to think that this coincidence has had a bearing on how my scientific life has turned out.

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.

Intense curiosity about the world can put one in harm’s way, but for me this was probably the only time in my life that this was true.

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.

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.

there would inevitably be a singularity, that is a point where space and time came to an end.

In particular, I wondered, can one have atoms in which the nucleus is a tiny primordial black hole, formed in the early universe?

Appropriately enough, A Brief History of Time was first published on April Fool’s Day in 1988.

This is partly because scientists, apart from Einstein, are not widely known rock stars, and partly because I fit the stereotype of a disabled genius.

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.

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.

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

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.

knowing the mind of God is knowing the laws of nature.

I think the universe was spontaneously created out of nothing, according to the laws of science.

How does an entire universe full of energy, the awesome vastness of space and everything in it, simply appear out of nothing?

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.

When the Big Bang produced a massive amount of positive energy, it simultaneously produced the same amount of negative energy. In this way, the positive and the negative add up to zero, always. It’s another law of nature.

The endless web of billions upon billions of galaxies, each pulling on each other by the force of gravity, acts like a giant storage device. The universe is like an enormous battery storing negative energy.

Something very wonderful happened to time at the instant of the Big Bang. Time itself began.

There is a chain of causality, stretching back into the past. But suppose this chain has a beginning, suppose there was a first event. What caused it?

the boundary condition of the universe is that it has no boundary in imaginary time, it won’t have just a single history.

The Anthropic Principle says that the universe has to be more or less as we see it, because if it were different there wouldn’t be anyone here to observe it.

Thus although the multiple-histories idea would allow any number of nearly flat directions, only histories with three flat directions will contain intelligent beings. Only in such histories will the question be asked, “Why does space have three dimensions?”

The irregularities you see are predicted by inflation, and they mean that some regions of the universe had a slightly higher density than others. The gravitational attraction of the extra density slows the expansion of that region, and can eventually cause it to collapse to form galaxies and stars. So look carefully at the map of the microwave sky. It is the blueprint for all the structure in the universe. We are the product of quantum fluctuations in the very early universe.

Different theories leave behind different fingerprints in the current structure of the universe, so astrophysical data can give us clues about the unification of all the forces of nature.

According to the no-boundary proposal, asking what came before the Big Bang is meaningless—like asking what is south of the South Pole—because there is no notion of time available to refer to. The concept of time only exists within our universe.

second law of thermodynamics. This law says that the total amount of disorder, or entropy, in the universe always increases with time. However, the law refers only to the total amount of disorder. The order in one body can increase provided that the amount of disorder in its surroundings increases by a greater amount.

But then most forms of life, ourselves included, are parasites, in that they feed off and depend for their survival on other forms of life. I think computer viruses should count as life. Maybe it says something about human nature that the only form of life we have created so far is purely destructive. Talk about creating life in our own image.

For the Strong Anthropic Principle, one supposes that there are many different universes, each with different values of the physical constants. In a small number, the values will allow the existence of objects like carbon atoms, which can act as the building blocks of living systems. Since we must live in one of these universes, we should not be surprised that the physical constants are finely tuned. If they weren’t, we wouldn’t be here.

But no heavier elements, like carbon or oxygen, would have been formed in the early universe. It is difficult to imagine that one could build a living system out of just hydrogen and helium—and anyway the early universe was still far too hot for atoms to combine into molecules.

It is estimated that one star in five has an Earth-like planet orbiting it at a distance from the star to be compatible with life as we know it.

we do not know how DNA molecules first appeared.

This was the development of language, and particularly written language. It meant that information could be passed on from generation to generation, other than genetically through DNA.

The amount of information handed down in books or via the internet is 100,000 times as much as there is in DNA.

At first, evolution proceeded by natural selection—from random mutations. This Darwinian phase lasted about three and a half billion years and produced us, beings who developed language to exchange information.

the internal record of information, handed down to succeeding generations in DNA, has changed somewhat. But the external record—in books and other long-lasting forms of storage—has grown enormously.

We are more than just our genes. We may be no stronger or inherently more intelligent than our caveman ancestors. But what distinguishes us from them is the knowledge that we have accumulated over the last 10,000 years, and particularly over the last 300. 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.

This has meant that no one person can be the master of more than a small corner of human knowledge.