A Brief History of Time

A Brief History of Time

by

Stephen Hawking

Teachers and parents! Struggling with distance learning? Our Teacher Edition on A Brief History of Time can help.
Note: all page numbers and citation info for the quotes below refer to the Bantam edition of A Brief History of Time published in 1988.
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Chapter 1 Quotes

“You’re very clever, young man, very clever,” said the old lady. “But it’s turtles all the way down.”

Most people would find the picture of our universe as an infinite tower of tortoises rather ridiculous, but why do we think we know better?

Page Number: 1
Explanation and Analysis:

The Greeks even had a third argument that the earth must be round, for why else does one first see the sails of a ship coming over the horizon, and only later see the hull?

Related Characters: Lay People , Aristotle
Page Number: 2
Explanation and Analysis:

Aristotle thought the earth was stationary and that the sun, the moon, the planets, and the stars moved in circular orbits about the earth. He believed this because he felt, for mystical reasons, that the earth was the center of the universe, and that circular motion was the most perfect.

Related Characters: Aristotle
Page Number: 2
Explanation and Analysis:

As far as Kepler was concerned, elliptical orbits were merely an ad hoc hypothesis, and a rather repugnant one at that, because ellipses were clearly less perfect than circles. […] he could not reconcile them with his idea that the planets were made to orbit the sun by magnetic forces.

Related Characters: Nicolas Copernicus (speaker), Sir Isaac Newton
Page Number: 4
Explanation and Analysis:

It is an interesting reflection on the general climate of thought before the twentieth century that no one had suggested that the universe was expanding or contracting. [...] this may have been due to people’s tendency to believe in eternal truths, as well as the comfort they found in the thought that even though they may grow old and die, the universe is eternal and unchanging.

Page Number: 6
Explanation and Analysis:
Chapter 2 Quotes

The Aristotelian tradition also held that one could work out all the laws that govern the universe by pure thought: it was not necessary to check by observation. So no one until Galileo bothered to see whether bodies of different weight did in fact fall at different speeds.

Page Number: 15
Explanation and Analysis:

Newton was very worried by this lack of absolute position, or absolute space, as it was called, because it did not accord with his idea of an absolute God. In fact, he refused to accept lack of absolute space, even though it was implied by his laws.

Related Characters: Sir Isaac Newton
Page Number: 18
Explanation and Analysis:
Chapter 3 Quotes

Our sun is just an ordinary, average-sized, yellow star, near the inner edge of one of the spiral arms [of a galaxy that is 100,000 light-years across]. We have certainly come a long way since Aristotle and Ptolemy, when we thought that the earth was the center of the universe!

Related Characters: Aristotle
Page Number: 39
Explanation and Analysis:

Many people do not like the idea that time has a beginning, probably because it smacks of divine intervention. (The Catholic Church, on the other hand, seized on the big bang model and in 1951 officially pronounced it to be in accordance with the Bible.)

Related Characters: God , Alexander Friedmann
Page Number: 49
Explanation and Analysis:
Chapter 4 Quotes

The success of scientific theories […] led the French scientist the Marquis de Laplace […] to argue that the universe was completely deterministic. Laplace suggested that there should be a set of scientific laws that would allow us to predict everything that would happen in the universe.

Related Characters: Werner Heisenberg, Marquis de Laplace
Page Number: 55
Explanation and Analysis:
Chapter 5 Quotes

We now know that neither the atoms nor the protons and neutrons within them are indivisible. So the question is: what are the truly elementary particles, the basic building blocks from which everything is made?

Page Number: 68
Explanation and Analysis:
Chapter 6 Quotes

The hostility of other scientists, particularly Eddington, his former teacher and the leading authority on the structure of stars, persuaded Chandrasekhar to abandon this line of work […] However, when he was awarded the Nobel Prize in 1983, it was […] for his early work on the limiting mass of cold stars.

Related Symbols: Nobel Prize
Page Number: 87
Explanation and Analysis:
Chapter 7 Quotes

[…] one evening in November that year, shortly after the birth of my daughter, Lucy, I started to think about black holes as I was getting into bed. My disability makes this rather a slow process, so I had plenty of time.

Related Characters: Stephen Hawking
Page Number: 103
Explanation and Analysis:
Chapter 8 Quotes

The Catholic Church had made a bad mistake with Galileo when it tried to lay down the law on a question of science, declaring that the sun went round the earth. Now, centuries later, it had decided to invite a number of experts to advise it on cosmology.

Related Characters: Galileo Galilei, Nicolas Copernicus
Page Number: 120
Explanation and Analysis:

The whole history of science has been the gradual realization that events do not happen in an arbitrary manner […] they reflect a certain underlying order, which may or may not be divinely inspired. […] There ought to be some principle that picks out […] one model, to represent our universe.

Related Characters: God
Page Number: 127
Explanation and Analysis:

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.

Related Characters: God
Page Number: 130
Explanation and Analysis:

Must we turn to the anthropic principle for an explanation? Was it all just a lucky chance? That would seem a counsel of despair, a negation of all our hopes of understanding the underlying order of the universe.

Page Number: 137
Explanation and Analysis:

We don’t yet have a complete and consistent theory that combines quantum mechanics and gravity. However, we are fairly certain of some features that such a unified theory should have.

Page Number: 138
Explanation and Analysis:

So long as the universe had a beginning, we could suppose it had a creator. But if the universe is really completely self-contained, having no boundary or edge, it would have neither beginning nor end: it would simply be. What place, then, for a creator?

Related Characters: God
Page Number: 146
Explanation and Analysis:
Chapter 9 Quotes

The progress of the human race in understanding the universe has established a small corner of order in an increasingly disordered universe.

Page Number: 156
Explanation and Analysis:
Chapter 11 Quotes

A complete, consistent, unified theory is only the first step: our goal is a complete understanding of the events around us, and of our own existence.

Page Number: 186
Explanation and Analysis:
Chapter 12 Quotes

Even if there is only one possible unified theory, it is just a set of rules and equations. What is it that breathes fire into the equations and makes a universe for them to describe? […] Why does the universe go to all the bother of existing?

Related Characters: God
Page Number: 190
Explanation and Analysis:

[…] if we do discover a complete theory […] Then we shall all […] be able to [discuss] why it is that we and the universe exist. If we find the answer to that, it would be the ultimate triumph of human reason—for then we would know the mind of God.

Related Characters: God , Lay People
Page Number: 191
Explanation and Analysis:
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