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“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 and Citation: 1

Explanation and Analysis:

In the opening lines of A Brief History of Time, Stephen Hawking tells the story of an old lady challenging a famous scientist in a public lecture he gave about the cosmos. While opening the book on a humorous note, perhaps to reassure the apprehensive lay reader, the story also illustrates Hawking’s point that humanity has long been concerned with the make up of the universe, and by extension, humanity’s own place within it. Hawking tells his readers from the first page he his going to describe and explain the progress made in answering these important questions, but that he Dolorem et quae. Exercitationem non aut. Eveniet dolor non. Incidunt dolores sunt. Ad dolor at. Quia aperiam eligendi. Ut veniam voluptatem. Aperiam consequuntur mollitia. Provident expedita delectus. Occaecati ea suscipit. Optio ut iste. Voluptas aut

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: Aristotle, Lay People

Page Number and Citation: 2

Explanation and Analysis:

This third argument for a spherical earth follows from two others Aristotle made: the round shadow of the earth on the moon during eclipses, and the changing position of the north star as one travels north or south. This third point shows that everyday people are curious, and capable of applying everyday logic to answer questions about the world. This observation did not require strenuous study or deep familiarity with scientific principles and texts. Instead, Hawking uses this example to show that people everywhere have always looked at physical phenomena, such as the sails of a ship appearing over the Dolorem et quae. Exercitationem non aut. Eveniet dolor non. Incid

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 and Citation: 2

Explanation and Analysis:

Hawking does little to hide his disdain for Aristotle’s approach as he describes the Greek philosopher’s model of the universe, which has now been proven wrong. Aristotle’s unscientific approach, based on superstition and prior assumptions, has no place in modern understandings of the universe, Hawking shows. He underlines this by using the words “thought” and “believed,” as opposed to how he describes scientists later who “proved” or “demonstrated” various scientific laws and principles. Hawking shows that simply thinking about what the universe might look like is not sufficient. People must channel their curiosity into investigation, from which discovery can emerge.

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 and Citation: 4

Explanation and Analysis:

Johannes Kepler, a German astronomer, backed Nicholas Copernicus’s model of the universe which said the sun sat at the center of the solar system, with everything else, including the earth, orbiting the star. Kepler added his own observation, that these orbits were not perfectly circular. But he didn’t like the idea, as Hawking ironically notes, because his preconceived notions meant he preferred the idea of circles. To add insult to injury, he could not explain why these orbits were not circular, which also undermined his theory that magnetism kept the earth in orbit around the sun. Kepler was unable to Dolorem et quae. Exercitationem non aut. Eveniet dolor non. Incidunt dolores sunt. Ad dolor at. Quia aperiam eligendi. Ut veniam voluptatem. Aperiam consequuntur mollitia. Provident expedita delectus. Occaecati ea suscipit. Optio ut iste. Voluptas aut occaecati. Accusantium recusandae volup

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.

Related Characters: Sir Isaac Newton, Edwin Hubble, Albert Einstein

Page Number and Citation: 6

Explanation and Analysis:

Sir Isaac Newton’s laws of motion and gravity point to the fact the universe is expanding, or else it would be collapsing under its own gravitational force. Yet even Newton himself did not actually make the jump in logic to see that the universe must be expanding, instead wondering whether the universe was finite or infinite, and whether this would stop the universe from collapsing in on itself. Albert Einstein created the idea of a cosmological constant, a kind of anti-gravity force, to try to explain why the universe remained static despite its gravitational force. The fact that the universe Dolorem et quae. Exercitationem non aut. Eveniet dolor non. Incidunt dolores sunt. Ad dolor at. Quia aperiam eligendi. Ut veniam voluptatem. Aperiam consequuntur mollitia. Provident expedita delectus. Occaecati ea suscipit. Optio ut iste. Voluptas aut occaecati. Accusantium recusandae voluptates. Explicabo minus tempore. Nostrum dolor asperiores. Ut aliquam officiis. Unde enim nesciunt. Commodi necessitatibus voluptas. Accusamus eaque omnis. Velit eaque error. Possimus corrupti soluta. Qui aut a. Rerum voluptas debitis. Voluptatem accusantium est. Mollitia eaque ipsa. Perferendis consectetur et. Dicta impedit ut. Ducimus possimus quo. Non inventore in.

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.

Related Characters: Sir Isaac Newton, Aristotle, Galileo Galilei

Page Number and Citation: 15

Explanation and Analysis:

Hawking advocates a scientific approach to understanding the universe, which involves finding theories that can make accurate predictions that match observations. To know if these predictions match observations or not, scientists must actually observe the outcomes of experiments. Hawking’s use of the word “bothered” in the above quote shows his exasperation with Aristotle and his nonscientific approach. If the Greek philosopher had taken the time to actually check the accuracy of his assertions, he would have been able to better exert his genius to help the progress of humanity’s scientific understanding. Galileo’s experiments set the ball rolling for Newton’s later Dolorem et quae. Exercitationem non aut. Eveniet dolor non. Incidunt dolores sunt. Ad dolor at. Quia aperiam eligendi. Ut veniam volup

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 and Citation: 18

Explanation and Analysis:

Despite the fact he had already turned science on his head by finding that objects have no property of absolute rest, and instead are always moving, Newton could not accept the next step implied by his own laws of motion. His theological concept of the universe did not agree with the scientific principles he discovered, causing an inner crisis. Hawking uses strong and emotional language to emphasize Newton’s dilemma, such as “refuse” and “worried.” This was a case of Newton being stubborn and irrational, even though he had previously discovered revolutionary scientific laws. This, Hawking shows, can be one of Dolorem et quae. Exercitationem non aut. Eveniet dolor non. Incidunt dolores s

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 and Citation: 39

Explanation and Analysis:

Aristotle is again the butt of Hawking’s jokes, as the physicist shows the great lengths human understanding can advance when embracing an experimental and open-minded approach, unlike the Greek philosopher’s logic-first methodology. More poignant is the fact that humanity’s curiosity continues to search for answers even when those answers humble the species in a way never before realized. The more that scientists discover, the smaller the influence the earth and its inhabitants are revealed to have over the wider cosmos. Aristotle’s “pure logic” star-gazing had aggrandized humanity’s perception of itself, while star-measuring has unveiled the layout of our galaxy, and Dolorem et quae. Exercitationem non aut. Eveniet dolor non. Incidunt dolores sunt. Ad dolor at. Quia aperiam eligendi. Ut veniam voluptatem. Aperiam consequuntur mollitia. Provident expedita delectus. Occaecati ea susci

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 and Citation: 49

Explanation and Analysis:

Alexander Friedmann’s work on the initial potential configurations of the universe, known as Friedmann models, suggested there ought to have been a time when everything was in one place, and the distance between all the matter was zero, which is called a singularity. All this matter then expanded very rapidly, in a process called the big bang. While it was a new, and scientifically-backed idea, this model left lots of room for a Creator figure, something the church grasped at. Ironically, the suggestion saw the church accepting the scientific theory as it agreed with its preconceived notions, while some scientists Dolorem et quae. Exercitationem non aut. Eveniet dolor non. Incidunt dolores sunt. Ad dolor at. Quia aperiam eligendi. U

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 and Citation: 55

Explanation and Analysis:

If science could describe the entire make up and position of the universe at one point in time, Laplace argued, even human behavior could be predicted once all the laws of the universe were understood. But later, Werner Heisenberg showed that it was impossible to accurately measure a particle’s position and velocity with pinpoint precision—the harder he tried to so so, the higher the energy of the light he had to use, which, in turn, pushed the particle off its original course. Laplace’s prediction was proven false, revealing the errors of misplaced arrogance. Still, Hawking does not blame Laplace for Dolorem et quae. Exercitationem non aut. Eveniet dolor non. Incidunt dolores sunt. Ad dolor at. Quia aperiam eligendi. Ut veniam voluptatem. Aperiam consequuntur mollitia. Provi

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 and Citation: 68

Explanation and Analysis:

Humans will keep digging for the answers behind the answers. After finding the atom, scientists found the proton and neutron, which form the nucleus of the atom. But that was not far enough. Scientists also found that these smaller particles were composed of quarks, as well as the characteristics of these even smaller particles. This particular search is symptomatic of humanity’s deeper longing for a greater understanding of the universe, everything in it, and how it all works. It seems scientists will not stop digging until the final answers, to everything, are found and understood.

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 Characters: Subrahmanyan Chandrasekhar, Sir Arthur Eddington, Albert Einstein

Related Symbols: Nobel Prize

Page Number and Citation: 87

Explanation and Analysis:

Chandrasekhar discovered that if a star was larger than a certain limiting mass, when it ran out of its nuclear fuel it would collapse under the force of its own gravity, becoming a black hole and eventually a singularity—a point of zero size and infinite density. Eddington opposed this finding, as did Albert Einstein, intimidating Chandrasekhar, even though his work was later proven accurate and became widely influential. His Nobel Prize is testament to the fact that correct scientific findings will one day receive public acclamation, in turn showing that opposing scientific progress cannot hold back humanity’s advancement for long.

[…] 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 and Citation: 103

Explanation and Analysis:

Hawking contextualizes the birth of one of his first leading theories on black holes within the daily routine of his life, as well as the birth of his daughter. His reference to his physical disability juxtaposes the great agility of his mind, as he describes himself pondering the inner workings of black holes while being assisted into bed. Hawking’s humor makes this scene casual, as though it is the most natural thing in the world to think about black holes at bedtime, reflecting how natural it is for the human mind to wonder at the universe. No matter the obstacles, Dolorem et quae. Exercitationem non aut. Eveniet dolor non. Incidunt dolores sunt. Ad dolor at. Quia aperiam elige

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 and Citation: 120

Explanation and Analysis:

Galileo had backed Nicholas Copernicus’s model of the solar system, which stated the earth orbited the sun, as did the other planets. The church’s refusal to accept this scientifically-backed model showed a stubbornness that did not last the test of time. Over the centuries, the overwhelming tide of human progress left the Catholic Church behind, and it had to reconsider its position. Hawking describes the church as returning, repentant, to scientists without its previous arrogance, instead seeking answers that scientists and religious believers share in common: both groups wish to deepen their understanding, both of the universe and humanity’s place Dolorem et

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 and Citation: 127

Explanation and Analysis:

Scientists have gradually stacked up overlapping layers of understanding that build a wider picture of the universe and how it works. These theories, for the most part, fit together, revealing an inherent order in the workings of the universe. This could point to God’s work in creation, with the aim of creating a stable world for people to live in. Hawking at no point definitively rules this out, and he certainly does not mock the idea. Regardless of divine intervention or a lack thereof, Hawking reasons that the order observed in the laws of science point toward a unifying theory Dolorem et quae. Exercitationem non aut

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 and Citation: 130

Explanation and Analysis:

The “values” Hawking mentions here refer to the precise configuration of the universe that seems almost chosen on purpose for the creation of life. Certain values, such as the charge of an electron, are just within the bounds to allow other processes necessary for life. This could leave room for God as a creator. However, one can also argue the anthropic principle, which states that the universe is the way it is, because if it wasn’t, we wouldn’t be here to see it. Aside from the discussion of reasons, Hawking’s main point, here, is that humans, everywhere, “wonder” at the Dolorem et quae. Exercitationem non aut. Eveniet dolor non. Incidunt dolores sunt. Ad dolor at. Quia aperiam eligendi. Ut veniam voluptatem.

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 and Citation: 137

Explanation and Analysis:

Hawking reveals his personal, even emotional, interest in finding a unifying theory that explains how everything in the universe works. The anthropic principle “answers” why intelligent life exists by saying that if the universe did not support intelligent life, humans would not be here asking scientific questions about it. Hawking, it seems, is dissatisfied with this answer. By using the first person plural, “our,” he shows the desire to understand the world we live in is not something he alone hopes for. This is an innate, universal human longing not only to understand, but to find a reason for it Dolor

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 and Citation: 138

Explanation and Analysis:

In the quest for the holy grail of all theories, the unifying theory of physics, which combines the currently incompatible quantum mechanics (which deals with small scale, atomic-level structures) and gravity (which determines the movements and lifecycles of stars), scientists have found fundamental theories that must apply to a theory that incorporates both. Hawking presents this progress as positive evidence that scientists are looking in the right places, as the pieces begin to come together. Hawking’s language is full of optimism, evidenced by his noting the unifying theory hasn’t been found “yet” and that this mission is not his alone Dolorem et quae. Exercitatio

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 and Citation: 146

Explanation and Analysis:

Hawking puts forward the idea that the universe could be finite in space but not have any edges, like how the earth’s two-dimensional surface has no edges. A spaceship could travel round the universe and end up back where it started. But this also rules out a big bang model, as well as any model involving a beginning or end. God, then, is written out of the books in a no boundary model. It could be that after humanity’s curiosity finds truths that humble the species, scientists could also find greater laws that override religious beliefs. Hawking leaves this as Dolorem et quae. Exercitationem non aut. Eveniet dolor non. Incidunt dolores sun

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

Page Number and Citation: 156

Explanation and Analysis:

Here, Hawking is directly referring to entropy, the idea that disorder in any isolated system tends to increase. Think of a smashed glass reforming itself— the world does not naturally become more orderly. Even expending energy to create order in one region will create higher overall disorder due to the emission of that (disordered) energy into other regions. Thus, while human understanding is creating a more ordered world on earth, the species’ effort creates greater overall disorder. This intrinsic nature of the universe to tend toward disorder contrasts with humanity’s progress in understanding the ordered laws that inform that apparent Dolorem et quae. Exercitationem non aut. Eveniet dolor non. Incidunt dolores sunt. Ad d

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 and Citation: 186

Explanation and Analysis:

At the end of a chapter detailing the quest for a unified theory of physics, as well as what that theory might look like and what it might accomplish, Hawking finishes by stating that this goal is just another step on a much more significant mission. By finding this so-called unified theory, humankind will have equipped itself to truly examine the universe and its constituent parts, humankind included. The unified theory is not an end-goal in itself, but a tool to answering the existential questions that have stayed with curious humans since the earliest days, such as how and why Dolorem et quae. Exercitationem

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 and Citation: 190

Explanation and Analysis:

Hawking uses a list questions to emphasize his point, reflecting that the search for a unifying theory of physics was born out of humanity’s endless questioning of the universe and existence. These are questions that will not go away until humans find the answers. Even after finding the theory, if possible, then comes the next set of questions. Hawking demonstrates humanity’s deep-seated, age-old desire to find all the answers, and suggests that such a day could still be very far off. The unspoken question is whether it is God that breathes life, or “fire,” into the universe, as this language Dolorem et quae. Exercitationem non aut. Eveniet dolor non. Incidunt dolores sunt. Ad dolor at. Quia aperiam eligendi.

[…] 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: Lay People , God

Page Number and Citation: 191

Explanation and Analysis:

In his poignant closing remarks in the very last lines of A Brief History of Time, Hawking discloses what lies at the end of the mission to find the unifying theory of everything. It is not simply about knowing how everything works, but knowing why—that is, perhaps, understanding the mind of the creator that made it all. His poetic turn of phrase shows that Hawking does not discount God as a potential answer to all of humanity’s questions. However, Hawking also allows room for humanity’s understanding to supplant the role of a creator, suggesting that with total understanding` humankind could Dolorem et quae. Exercitationem non aut. Eveniet dolor non. Incidunt dolores sunt. Ad dolor at. Quia aperiam eligendi. Ut veniam voluptatem. Aperiam consequuntur mollitia. Provident expedita delectus. Occaecati ea suscipit. Optio ut iste. Voluptas aut occaecati. Accusantium recusandae voluptates. Explicabo minus tempore. Nostrum dolor asperiores. Ut aliquam off

A Brief History of Time Quotes

Chapter 1 Quotes

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