Quotes from Stephen Hawking

As Nathan Myhrvold of Microsoft (a former post-doc of mine) remarked: I have sold more books on physics than Madonna has on sex.

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.

The fundamental postulate of the theory of relativity, as it was called, was that the laws of science should be the same for all freely moving observers, no matter what their speed.

Only time (whatever that may be) will tell.

Our very existence imposes rules determining from where and at what time it is possible for us to observe the universe. That is, the fact of our being restricts the characteristics of the kind of environment in which we find ourselves. That principle is called the weak anthropic principle.

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

Thus the possibility of time travel remains open.

So the total energy of the universe is zero.

why we should be in the expanding phase rather than the contracting phase? One can answer this on the basis of the weak anthropic principle. Conditions in the contracting phase would not be suitable for the existence of intelligent beings who could ask the question: why is disorder increasing in the same direction of time as that in which the universe is expanding?

events before the big bang can have no consequences, so they should not form part of a scientific model of the universe.

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.

Our universe and its laws appear to have a design that both is tailor-made to support us and, if we are to exist, leaves little room for alteration. That is not easily explained, and raises the natural question of why it is that way.

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.

Our population and our use of the finite resources of planet Earth are growing exponentially, along with our technical ability to change the environment for good or ill.

Nature and Nature's laws lay hid in night: God said, Let Newton be! and all was light.

Among the heresies was the idea that nature follows laws, because this conflicts with God's omnipotence. Interestingly, Pope John was killed by the effects of the law of gravity a few months later when the roof of his palace fell in on him.

an­ti­quarks? Why are there not equal num­bers of each? It is cer­tain­ly for­tu­nate for us that the num­bers are un­equal be ear­ly uni­verse and left a uni­verse filled with ra­di­ation but hard­ly any mat­ter. There would then have been no galax­ies, stars, or plan­ets on which hu­man life could have de­vel­oped.

In physics a system is said to have a symmetry if its properties are unaffected by a certain transformation such as rotating it in space or taking its mirror image. For example, if you flip a donut over, it looks exactly the same (unless it has a chocolate topping, in which case it is better just to eat it).

If the theory is confirmed by observation, it will be the successful conclusion of a search going back more than 3,000 years. We will have found the grand design.

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.

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.

Why is there something rather than nothing? Why do we exist? Why this particular set of laws and not some other? This is the Ultimate Question of Life, the Universe, and Everything. We shall attempt to answer it in this book. Unlike the answer given in The Hitchhiker's Guide to the Galaxy, ours won't be simply "42."  

There is no picture- or theory-independent concept of reality.

redefining the goal of science: our aim is to formulate a set of laws that enables us to predict events only up to the limit set by the uncertainty principle.