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A Brief History of Time: from The Big Bang To Black Holes
- GenresScience
Paperback
Published December 23, 1989
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8 people want to read
About the author
Stephen W. Hawking
242 books12.8k followersStephen William Hawking was an English theoretical physicist, cosmologist, and author who was director of research at the Centre for Theoretical Cosmology at the University of Cambridge. Between 1979 and 2009, he was the Lucasian Professor of Mathematics at Cambridge, widely viewed as one of the most prestigious academic posts in the world.
Hawking was born in Oxford into a family of physicians. In October 1959, at the age of 17, he began his university education at University College, Oxford, where he received a first-class BA degree in physics. In October 1962, he began his graduate work at Trinity Hall, Cambridge, where, in March 1966, he obtained his PhD degree in applied mathematics and theoretical physics, specialising in general relativity and cosmology. In 1963, at age 21, Hawking was diagnosed with an early-onset slow-progressing form of motor neurone disease that gradually, over decades, paralysed him. After the loss of his speech, he communicated through a speech-generating device initially through use of a handheld switch, and eventually by using a single cheek muscle.
Hawking's scientific works included a collaboration with Roger Penrose on gravitational singularity theorems in the framework of general relativity, and the theoretical prediction that black holes emit radiation, often called Hawking radiation. Initially, Hawking radiation was controversial. By the late 1970s, and following the publication of further research, the discovery was widely accepted as a major breakthrough in theoretical physics. Hawking was the first to set out a theory of cosmology explained by a union of the general theory of relativity and quantum mechanics. He was a vigorous supporter of the many-worlds interpretation of quantum mechanics.
Hawking achieved commercial success with several works of popular science in which he discussed his theories and cosmology in general. His book A Brief History of Time appeared on the Sunday Times bestseller list for a record-breaking 237 weeks. Hawking was a Fellow of the Royal Society, a lifetime member of the Pontifical Academy of Sciences, and a recipient of the Presidential Medal of Freedom, the highest civilian award in the United States. In 2002, Hawking was ranked number 25 in the BBC's poll of the 100 Greatest Britons. He died in 2018 at the age of 76, having lived more than 50 years following his diagnosis of motor neurone disease.
Hawking was born in Oxford into a family of physicians. In October 1959, at the age of 17, he began his university education at University College, Oxford, where he received a first-class BA degree in physics. In October 1962, he began his graduate work at Trinity Hall, Cambridge, where, in March 1966, he obtained his PhD degree in applied mathematics and theoretical physics, specialising in general relativity and cosmology. In 1963, at age 21, Hawking was diagnosed with an early-onset slow-progressing form of motor neurone disease that gradually, over decades, paralysed him. After the loss of his speech, he communicated through a speech-generating device initially through use of a handheld switch, and eventually by using a single cheek muscle.
Hawking's scientific works included a collaboration with Roger Penrose on gravitational singularity theorems in the framework of general relativity, and the theoretical prediction that black holes emit radiation, often called Hawking radiation. Initially, Hawking radiation was controversial. By the late 1970s, and following the publication of further research, the discovery was widely accepted as a major breakthrough in theoretical physics. Hawking was the first to set out a theory of cosmology explained by a union of the general theory of relativity and quantum mechanics. He was a vigorous supporter of the many-worlds interpretation of quantum mechanics.
Hawking achieved commercial success with several works of popular science in which he discussed his theories and cosmology in general. His book A Brief History of Time appeared on the Sunday Times bestseller list for a record-breaking 237 weeks. Hawking was a Fellow of the Royal Society, a lifetime member of the Pontifical Academy of Sciences, and a recipient of the Presidential Medal of Freedom, the highest civilian award in the United States. In 2002, Hawking was ranked number 25 in the BBC's poll of the 100 Greatest Britons. He died in 2018 at the age of 76, having lived more than 50 years following his diagnosis of motor neurone disease.
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July 10, 2024
Stephen Hawking is incredibly famous of course and I’ve always meant to read his book “A brif history of time” but the best I’ve managed so far is this Blinkist summary of the book. And this current review is based on that. Yes a cheap way to assess a book and I undoubtedly miss a great deal. Though, on the other hand, I also pick up a fair bit of what the book is about. And not sure that I will be rushing off to buy the full book.....Hmm, just checked and I already have two versions of the full book. So maybe I will do a comparison. Anyway here are a few selections from the Blinkist review that stood out for me:
Theories based on what you’ve seen in the past can help predict the future. A theory, in its most basic terms, is a model that accurately explains large groups of observations. Scientists collect data from observations they see in, for example, experiments, and use it to develop explanations of how and why phenomena happen. [I must admit, the writing is admirably clear ...not sure if that is Hawking or the Blinkist writer]
Theories have two great benefits:
1. First, they allow scientists to make definite predictions about future events.
2. Second, theories are always disprovable, meaning they’re open to reform if new evidence that doesn’t fit the theory is found.
So in effect, a single future observation can always invalidate a theory,
In the 1600s, Isaac Newton revolutionized the way we think about how objects move. It was long thought that objects didn’t move ..they were stationary unless pushed. In the 1600s, Newton thoroughly disproved this long-held belief. In its place, he introduced a theory which stated that all objects in the universe, instead of being still, were in fact in constant motion.
To describe how all objects in the universe move, Newton developed three laws:
1. The first of Newton’s laws states that all objects will continue moving in a straight line if not acted on by another force.
2. Newton’s second law states that an object will speed up at a rate proportional to the force acting on it.
3. Newton’s third law describes gravity. It states that all bodies in the universe attract other bodies with a force proportional to the mass of each object.
The fact that the speed of light is constant shows that you can’t always measure something’s speed relative to something else’s......We have seen how Newton’s theory did away with absolute rest and replaced it with the idea that the movement of an object is relative to the movement of something else. Yet, the theory also suggested the speed of an object is relative. But, one major hole developed in Newton’s theory: the speed of light. The speed of light is constant, not relative. It is always 186,000 miles per second. It doesn’t matter how fast something else is going, the speed of light remains the same......doesn’t matter who is viewing the light or how quickly they are traveling, its speed will always be the same.
How can the speed of something be constant regardless of the state of the observer?
The theory of relativity states that time itself is not fixed......The theory of relativity states that the laws of science are the same for all freely moving observers. This means that no matter what someone’s speed might be, they would observe the same speed of light. One of its central suggestions is actually very difficult for many to comprehend; it states that time is relative.......What this means is that because the speed of light doesn’t change for observers moving at different speeds, observers traveling relative to one another would actually measure different times for the same event.......this would mean that they each experience the flash event [eg. With trains passing and observers on platform] as if it happened at two different times. This is because time is determined by the distance something has travelled divided by its speed. The speed of light is the same for both observers, but as the distance is different, time is relative to each observer. [Again beautifully explained with great economy of words].....If both observers carried clocks to record when the pulse of light was emitted, these would confirm two different times for the same event.
So who’s right? Neither observer; time is relative and unique to both observers’ perspectives!.....Since one can’t make exact measurements of particles, scientists use something called quantum state to make predictions.
Bizarrely, the more precisely you try to measure the position of a particle, the more uncertain its speed becomes; and the more exactly its speed is measured, the less certain its position becomes! This phenomenon, first discovered in the 1920s, is called the uncertainty principle.
Because of the uncertainty principle, scientists had to use other ways of looking at particles, so they began to look at a particle’s quantum state instead. Quantum state combines many likely possible positions and speeds of a particle.
Since scientists cannot pinpoint a particle’s definite position or velocity, they look at the many likely positions particles might occupy and velocities they might have....To help them determine this, scientists treat particles as if they are waves.....The multitude of different positions that a particle can be in means that they appear like a series of continuous, oscillating waves......Looking at particles like this helps scientists figure out where a particle is most likely to be. The likeliest positions of the particle occur where the arcs and dips on the many waves correspond with each other, and the least likely positions are where they don't. This is called interference,
Gravity is the result of massive objects curving the universe.....when calculating an event’s position along with the three-dimensional coordinates, scientists add a fourth coordinate to indicate time.....Scientists have to take time into consideration when determining the position of an event because the theory of relativity states that time is relative. It is therefore an important factor in describing the nature of an event.....An amazing consequence of the combination of space and time is how it changed our conception of gravity. Gravity is the result of massive objects curving space-time. A huge mass, like that of our sun, curves and actually alters space-time.....Other objects then follow these curves in space-time.
When a star with a very high mass dies, it collapses into a singularity called a black hole.
A black hole occurs because the gravitational field of most massive stars is so strong. While the star is alive, it is able to use its energy to keep itself from collapsing. But when the star runs out of energy, it can no longer overcome the gravity and its decaying body collapses in on itself. Everything is pulled inwards toward an infinitely dense, spherical point called a singularity.
When a black hole forms, space-time is curved so steeply by its gravity that even light bends along it.....This raises a question: if a black hole absorbs light and anything else that crosses its event horizon, how can we know they are there?......Scientists look for stars orbiting dark and massive objects that could be black holes. They also look for the X-rays and other waves that are commonly produced by matter when it is being sucked in and torn up by a black hole.....Black holes emit radiation, which can lead to their demise through evaporation.
The universal second law of thermodynamics states that entropy, the tendency toward greater disorder, always increases. And as entropy increases, so must temperature. An example of this is the way a fire-poker, after being in a fire, glows red-hot and releases radiation as heat.......According to the second law, since black holes suck in disordered energy from the universe, the entropy of the black hole should also increase. And with this increase in entropy, black holes should have to let heat escape........Virtual pairs of particles and antiparticles near the event horizon conserve the second law of thermodynamics. Virtual particles are particles that cannot be detected but whose effects can be measured. One of the partners in the pair has positive energy and the other has negative energy.....In a black hole, gravitation is so strong it can suck the negative particle into the black hole and in doing so give its particle partner enough energy to possibly escape into the universe and be emitted as heat. This allows the black hole to emit radiation, and thus follow the second law of thermodynamics.....The amount of positive radiation emitted is balanced by the negative particles being sucked into the black hole. If its mass becomes small enough, the black hole will most likely end in a massive final explosion, as large as millions of H-bombs.
Although we can’t be sure, there are strong indicators that suggest that time can only move forwards.....There are three strong indicators that suggest time only moves forward.
1. The first indicator showing that the passage of time goes from past to future is the thermodynamic arrow of time.
2. The second indicator of forward time: the psychological arrow of time, which is dictated by memory. After that cup has broken, you can remember it being on the table; but before this, when it was still on the table, you can’t “recall” it’s future position on the floor.
3. The third indicator, the cosmological arrow of time, refers to the expansion of the universe, and this also follows along our perception of the thermodynamic arrow of time. This is because as the universe expands, entropy increases.
Intelligent beings can only exist as disorder increases.....Therefore, as long as we’re around, we will observe the cosmological arrow of time as going forward.
In addition to gravity, there are three fundamental forces in the universe.
What kinds of forces are at work in the universe?....Most people will have heard about only one: gravity. But there are three additional forces
1. The first is electromagnetic force,...This force is much stronger than gravity and dominates at the small level of the atom. For example, electromagnetic force causes an electron to orbit around the atom’s nucleus.
2. The second is weak nuclear force, which acts on all the particles that make up matter and causes radioactivity.....At higher energies, the strength of weak nuclear force increases until it matches that of electromagnetic force.
3. The third is strong nuclear force, which binds protons and neutrons in the nucleus of an atom, and binds the smaller quarks within protons and neutrons.....the strong nuclear force gets weaker at higher energies.
At a very high energy called grand unification energy, electromagnetic force and weak nuclear force get stronger and strong nuclear force gets weaker. At that point, all three forces reach equal strength and become different aspects of a single force: a force that might have played a role in the creation the universe.
Although scientists believe that the universe started with the big bang, they are unsure of exactly how this happened......Scientists, however, don’t exactly know how this big bang occurred......The most widely accepted theory of the universe's beginning is the hot big bang model......In this model, the universe started with zero size and was infinitely hot and dense. During the big bang, it expanded, and as it grew its temperature cooled as its heat was spread.......Its not the only model. Another model is the inflationary model. This model proposes that the energy of the early universe was so enormously high that the strengths of the strong nuclear force, weak nuclear force and electromagnetic force were equal. As the universe expanded, however, the three forces took on different strengths very quickly.
Physicists haven’t been able to unify general relativity and quantum physics.
In their desire to understand and describe the universe, scientists have developed two major theories. The first is general relativity, which concentrates on a very large phenomenon in the universe: gravity. The second is quantum physics, which describes some of the smallest known objects in the universe: particles smaller than atoms.
Currently there is no way of combining them together to make one complete unified theory of everything.......Many of the equations scientists use in quantum physics result in seemingly impossible infinite values......instead of using the equations from quantum physics to predict events, the events themselves have to be added and the equations tweaked to make them fit!
A second, similar problem is that quantum theory suggests that all the empty space in the universe is made up of virtual pairs of particles and antiparticles.....However, the existence of these virtual pairs causes difficulties for general relativity. Since there is an infinite amount of empty space in the universe, the energy of these pairs would have to have infinite energy.
This is problematic because Einstein’s famous equation E=mc2 suggests that the mass of an object is equal to its energy. So the infinite energy of these virtual particles would mean that they would also have infinite mass. And if there were infinite mass, then the whole universe would collapse under the intense gravitational pull and become a single black hole. [I notice that there is no mention here of dark matter nor dark energy despite them apparently dominating the universe.....I wonder if they are mentioned in the full book?]
The main message in this book: Many people are put off physics because they see it as an impenetrable world of lengthy equations and complex theories. And, to a certain extent, this is true. But the complexity of physics shouldn’t stop us non-experts from learning how and why the universe works. There are a number of rules and laws that help us understand the mysteries of the universe around us. Rules and laws that most of us can comprehend. And once we understand them, we can begin to see the universe in a new light.
My take on the book? I thought that it would be difficult to understand but it is remarkably clear....though doesn't mention dark matter or dark energy....and apparently, Hawking was unhappy with it because he wrote a later book with Hertog with a rather different slant on the universe. (More like a holograph). But five stars from me.
Theories based on what you’ve seen in the past can help predict the future. A theory, in its most basic terms, is a model that accurately explains large groups of observations. Scientists collect data from observations they see in, for example, experiments, and use it to develop explanations of how and why phenomena happen. [I must admit, the writing is admirably clear ...not sure if that is Hawking or the Blinkist writer]
Theories have two great benefits:
1. First, they allow scientists to make definite predictions about future events.
2. Second, theories are always disprovable, meaning they’re open to reform if new evidence that doesn’t fit the theory is found.
So in effect, a single future observation can always invalidate a theory,
In the 1600s, Isaac Newton revolutionized the way we think about how objects move. It was long thought that objects didn’t move ..they were stationary unless pushed. In the 1600s, Newton thoroughly disproved this long-held belief. In its place, he introduced a theory which stated that all objects in the universe, instead of being still, were in fact in constant motion.
To describe how all objects in the universe move, Newton developed three laws:
1. The first of Newton’s laws states that all objects will continue moving in a straight line if not acted on by another force.
2. Newton’s second law states that an object will speed up at a rate proportional to the force acting on it.
3. Newton’s third law describes gravity. It states that all bodies in the universe attract other bodies with a force proportional to the mass of each object.
The fact that the speed of light is constant shows that you can’t always measure something’s speed relative to something else’s......We have seen how Newton’s theory did away with absolute rest and replaced it with the idea that the movement of an object is relative to the movement of something else. Yet, the theory also suggested the speed of an object is relative. But, one major hole developed in Newton’s theory: the speed of light. The speed of light is constant, not relative. It is always 186,000 miles per second. It doesn’t matter how fast something else is going, the speed of light remains the same......doesn’t matter who is viewing the light or how quickly they are traveling, its speed will always be the same.
How can the speed of something be constant regardless of the state of the observer?
The theory of relativity states that time itself is not fixed......The theory of relativity states that the laws of science are the same for all freely moving observers. This means that no matter what someone’s speed might be, they would observe the same speed of light. One of its central suggestions is actually very difficult for many to comprehend; it states that time is relative.......What this means is that because the speed of light doesn’t change for observers moving at different speeds, observers traveling relative to one another would actually measure different times for the same event.......this would mean that they each experience the flash event [eg. With trains passing and observers on platform] as if it happened at two different times. This is because time is determined by the distance something has travelled divided by its speed. The speed of light is the same for both observers, but as the distance is different, time is relative to each observer. [Again beautifully explained with great economy of words].....If both observers carried clocks to record when the pulse of light was emitted, these would confirm two different times for the same event.
So who’s right? Neither observer; time is relative and unique to both observers’ perspectives!.....Since one can’t make exact measurements of particles, scientists use something called quantum state to make predictions.
Bizarrely, the more precisely you try to measure the position of a particle, the more uncertain its speed becomes; and the more exactly its speed is measured, the less certain its position becomes! This phenomenon, first discovered in the 1920s, is called the uncertainty principle.
Because of the uncertainty principle, scientists had to use other ways of looking at particles, so they began to look at a particle’s quantum state instead. Quantum state combines many likely possible positions and speeds of a particle.
Since scientists cannot pinpoint a particle’s definite position or velocity, they look at the many likely positions particles might occupy and velocities they might have....To help them determine this, scientists treat particles as if they are waves.....The multitude of different positions that a particle can be in means that they appear like a series of continuous, oscillating waves......Looking at particles like this helps scientists figure out where a particle is most likely to be. The likeliest positions of the particle occur where the arcs and dips on the many waves correspond with each other, and the least likely positions are where they don't. This is called interference,
Gravity is the result of massive objects curving the universe.....when calculating an event’s position along with the three-dimensional coordinates, scientists add a fourth coordinate to indicate time.....Scientists have to take time into consideration when determining the position of an event because the theory of relativity states that time is relative. It is therefore an important factor in describing the nature of an event.....An amazing consequence of the combination of space and time is how it changed our conception of gravity. Gravity is the result of massive objects curving space-time. A huge mass, like that of our sun, curves and actually alters space-time.....Other objects then follow these curves in space-time.
When a star with a very high mass dies, it collapses into a singularity called a black hole.
A black hole occurs because the gravitational field of most massive stars is so strong. While the star is alive, it is able to use its energy to keep itself from collapsing. But when the star runs out of energy, it can no longer overcome the gravity and its decaying body collapses in on itself. Everything is pulled inwards toward an infinitely dense, spherical point called a singularity.
When a black hole forms, space-time is curved so steeply by its gravity that even light bends along it.....This raises a question: if a black hole absorbs light and anything else that crosses its event horizon, how can we know they are there?......Scientists look for stars orbiting dark and massive objects that could be black holes. They also look for the X-rays and other waves that are commonly produced by matter when it is being sucked in and torn up by a black hole.....Black holes emit radiation, which can lead to their demise through evaporation.
The universal second law of thermodynamics states that entropy, the tendency toward greater disorder, always increases. And as entropy increases, so must temperature. An example of this is the way a fire-poker, after being in a fire, glows red-hot and releases radiation as heat.......According to the second law, since black holes suck in disordered energy from the universe, the entropy of the black hole should also increase. And with this increase in entropy, black holes should have to let heat escape........Virtual pairs of particles and antiparticles near the event horizon conserve the second law of thermodynamics. Virtual particles are particles that cannot be detected but whose effects can be measured. One of the partners in the pair has positive energy and the other has negative energy.....In a black hole, gravitation is so strong it can suck the negative particle into the black hole and in doing so give its particle partner enough energy to possibly escape into the universe and be emitted as heat. This allows the black hole to emit radiation, and thus follow the second law of thermodynamics.....The amount of positive radiation emitted is balanced by the negative particles being sucked into the black hole. If its mass becomes small enough, the black hole will most likely end in a massive final explosion, as large as millions of H-bombs.
Although we can’t be sure, there are strong indicators that suggest that time can only move forwards.....There are three strong indicators that suggest time only moves forward.
1. The first indicator showing that the passage of time goes from past to future is the thermodynamic arrow of time.
2. The second indicator of forward time: the psychological arrow of time, which is dictated by memory. After that cup has broken, you can remember it being on the table; but before this, when it was still on the table, you can’t “recall” it’s future position on the floor.
3. The third indicator, the cosmological arrow of time, refers to the expansion of the universe, and this also follows along our perception of the thermodynamic arrow of time. This is because as the universe expands, entropy increases.
Intelligent beings can only exist as disorder increases.....Therefore, as long as we’re around, we will observe the cosmological arrow of time as going forward.
In addition to gravity, there are three fundamental forces in the universe.
What kinds of forces are at work in the universe?....Most people will have heard about only one: gravity. But there are three additional forces
1. The first is electromagnetic force,...This force is much stronger than gravity and dominates at the small level of the atom. For example, electromagnetic force causes an electron to orbit around the atom’s nucleus.
2. The second is weak nuclear force, which acts on all the particles that make up matter and causes radioactivity.....At higher energies, the strength of weak nuclear force increases until it matches that of electromagnetic force.
3. The third is strong nuclear force, which binds protons and neutrons in the nucleus of an atom, and binds the smaller quarks within protons and neutrons.....the strong nuclear force gets weaker at higher energies.
At a very high energy called grand unification energy, electromagnetic force and weak nuclear force get stronger and strong nuclear force gets weaker. At that point, all three forces reach equal strength and become different aspects of a single force: a force that might have played a role in the creation the universe.
Although scientists believe that the universe started with the big bang, they are unsure of exactly how this happened......Scientists, however, don’t exactly know how this big bang occurred......The most widely accepted theory of the universe's beginning is the hot big bang model......In this model, the universe started with zero size and was infinitely hot and dense. During the big bang, it expanded, and as it grew its temperature cooled as its heat was spread.......Its not the only model. Another model is the inflationary model. This model proposes that the energy of the early universe was so enormously high that the strengths of the strong nuclear force, weak nuclear force and electromagnetic force were equal. As the universe expanded, however, the three forces took on different strengths very quickly.
Physicists haven’t been able to unify general relativity and quantum physics.
In their desire to understand and describe the universe, scientists have developed two major theories. The first is general relativity, which concentrates on a very large phenomenon in the universe: gravity. The second is quantum physics, which describes some of the smallest known objects in the universe: particles smaller than atoms.
Currently there is no way of combining them together to make one complete unified theory of everything.......Many of the equations scientists use in quantum physics result in seemingly impossible infinite values......instead of using the equations from quantum physics to predict events, the events themselves have to be added and the equations tweaked to make them fit!
A second, similar problem is that quantum theory suggests that all the empty space in the universe is made up of virtual pairs of particles and antiparticles.....However, the existence of these virtual pairs causes difficulties for general relativity. Since there is an infinite amount of empty space in the universe, the energy of these pairs would have to have infinite energy.
This is problematic because Einstein’s famous equation E=mc2 suggests that the mass of an object is equal to its energy. So the infinite energy of these virtual particles would mean that they would also have infinite mass. And if there were infinite mass, then the whole universe would collapse under the intense gravitational pull and become a single black hole. [I notice that there is no mention here of dark matter nor dark energy despite them apparently dominating the universe.....I wonder if they are mentioned in the full book?]
The main message in this book: Many people are put off physics because they see it as an impenetrable world of lengthy equations and complex theories. And, to a certain extent, this is true. But the complexity of physics shouldn’t stop us non-experts from learning how and why the universe works. There are a number of rules and laws that help us understand the mysteries of the universe around us. Rules and laws that most of us can comprehend. And once we understand them, we can begin to see the universe in a new light.
My take on the book? I thought that it would be difficult to understand but it is remarkably clear....though doesn't mention dark matter or dark energy....and apparently, Hawking was unhappy with it because he wrote a later book with Hertog with a rather different slant on the universe. (More like a holograph). But five stars from me.
January 4, 2026
Stephen Hawking was undoubtedly a brilliant man with a brilliant mind. I don't profess to be able to debate the content of the book in the slightest. What I would argue with though is the concept that this book is geared towards the lay person understanding the basic aspects of space time, as appears to be the purpose laid out in the introduction.
As a work for study purposes I think this would be a fantastic tool, I can't say however that I've come away with a significantly improved understanding of the universe because the book is just too complicated and moves too quickly from theory to theory.
I suspect you would need to either have a much better foundation knowledge than my maths and physics A-levels, or read this multiple times in order to develop a significantly deeper understanding of the subject matter.
As a work for study purposes I think this would be a fantastic tool, I can't say however that I've come away with a significantly improved understanding of the universe because the book is just too complicated and moves too quickly from theory to theory.
I suspect you would need to either have a much better foundation knowledge than my maths and physics A-levels, or read this multiple times in order to develop a significantly deeper understanding of the subject matter.
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