Stephen Hawking - A Brief History of Time (1988)

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Most sets of values would give rise to universes that, although they might be very beautiful, would contain no one able to wonder at that beauty.

Stephen Hawking
Each equation, I was told, would halve the sales of the book. But that was okay. Equations are necessary if you are doing accountancy, but they are the boring part of mathematics. Most of the interesting ideas can be conveyed by words or pictures.

Stephen Hawking
In an infinite number universe, every point can be regarded as the center, because every point has an infinity of stars on each side of it.

Stephen Hawking
The light that we see from distant galaxies left them millions of years ago, and in the case of the most distant object we have seen, the light left some eight billions years ago. Thus, when we look at the universe, we are seeing it as it was in the past.

Stephen Hawking
Or in other words, why does disorder increase in the same direction of time as that in which the universe expands?

Stephen Hawking
We see the universe the way it is because we exist.

Stephen Hawking
But a machine that was powerful enough to accelerate particles to the grand unification energy would have to be as big as the Solar System - and would be unlikely to be funded in the present economic climate.

Stephen Hawking
It is impossible to imagine a four-dimensional space. I personally find it hard enough to visualize a three-dimensional space!

Stephen Hawking
The theory of relativity does, however, force us to change fundamentally our ideas of space and time. We must accept that time is not completely separate from and independent of space, but is combined with it to form an object called space-time.

Stephen Hawking
I have sold more books on physics than Madonna has on sex.
[Hawking adopted this statement from a remark made to him by his former post-doc, Nathan Myhrvold.]

Stephen Hawking
Gravity is so strong that space is bent round onto itself, making it rather like the surface of the earth. If one keeps traveling in a certain direction on the surface of the earth, one never comes up against an impassable barrier or falls over the edge, but eventually comes back to where one started.

Stephen Hawking
The laws of science, as we know them at present, contain many fundamental numbers, like the size of the electric charge of the electron and the ratio of the masses of the proton and the electron.... The remarkable fact is that the values of these numbers seem to have been finely adjusted to make possible the development of life.

Stephen Hawking
But if he [God] had started it [the universe] off in such an incomprehensible way, why did he choose to let it evolve according to laws that we could understand?

Stephen Hawking
The rate of progress is so rapid that what one learns at school or university is always a bit out of date. Only a few people can keep up with the rapidly advancing frontier of knowledge, and they have to devote their whole time to it and specialize in a small area. The rest of the population has little idea of the advances that are being made or the excitement they are generating.

Stephen Hawking
Someone told me that each equation I included in the book would halve the sales. I therefore resolved not to have any equations at all. In the end, however, I did put in one equation, Einstein's famous equation, E = mc squared. I hope that this will not scare off half of my potential readers.

Stephen Hawking
Each time new experiments are observed to agree with the predictions the theory survives, and our confidence in it is increased; but if ever a new observation is found to disagree, we have to abandon or modify the theory.

Stephen Hawking
In this way, Edwin Hubble worked out the distances to nine different galaxies. We now know that our galaxy is only one of some hundred thousand million that can be seen using modern telescopes, each galaxy itself containing some hundred thousand million stars.

Stephen Hawking
Maybe that is our mistake: maybe there are no particle positions and velocities, but only waves. It is just that we try to fit the waves to our preconceived ideas of positions and velocities. The resulting mismatch is the cause of the apparent unpredictability.

Stephen Hawking
One could say: "The boundary condition of the universe is that it has no boundary." The universe would be completely self-contained and not affected by anything outside itself. It would neither be created nor destroyed. It would just BE.

Stephen Hawking
As philosopher of science Karl Popper has emphasized, a good theory is characterized by the fact that it makes a number of predictions that could in principle be disproved or falsified by observation.

Stephen Hawking
Bodies like the earth are not made to move on curved orbits by a force called gravity; instead, they follow the nearest thing to a straight path in a curved space, which is called a geodesic. A geodesic is the shortest (or longest) path between two nearby points.

Stephen Hawking
Just like a computer, we must remember things in the order in which entropy increases. This makes the second law of thermodynamics almost trivial. Disorder increases with time because we measure time in the direction in which disorder increases. You can't have a safer bet than that!

Stephen Hawking
As we shall see, the concept of time has no meaning before the beginning of the universe. This was first pointed out by St. Augustine. When asked: What did God do before he created the universe? Augustine didn't reply: He was preparing Hell for people who asked such questions. Instead, he said that time was a property of the universe that God created, and that time did not exist before the beginning of the universe.

Stephen Hawking
If there really is a complete unified theory that governs everything, it presumably also determines your actions. But it does so in a way that is impossible to calculate for an organism that is as complicated as a human being. The reason we say that humans have free will is because we can't predict what they will do.

Stephen Hawking
Galileo, perhaps more than any other single person, was responsible for the birth of modern science.

Stephen Hawking