Customer Rating: 
Summary: Highly recommended to everybody interested in Astronomy and Nuclear Physics
Comment: Stephen Hawking, one of the greatest contemporary physicists explores in a very interesting and informative way the unresolved riddles about the universe and the structure of particles, energy, time, gravity, various forces in the universe, god and their relationship with one another. His approach is both scientific and philosophical raising questions about the meaning of human existence in the universe. Although quite detailed the questions raised and alternative explanations offered are appealing both to the amateur and the professional. Stephen Hawking approaches the fundamental issues from many aspects including Newtonian physics, Special and General Relativity of Einstein, Quantum physics, string theory etc. He compares the different approaches, explains how they arose historically and the quest for a unified theory of the universe. Of course he devotes a lot of time to the primary issue of the creation and possible end of the universe. His treatment of matter and antimatter are especially interesting. I had read the book many years ago, recently I listened to the audio CD. I recommend both as a rich source of knowledge about these topics from a leading scientist on these issues.
I also recommend The Fabric of the Cosmos by Brian Green which is also a very interesting exploration of the same issues.
Customer Rating:
Summary: A bit too brief
Comment: I felt like there wasn't enough information in Hawking's explanations to really understand the concepts. So many times the fragments of information provided left me with a vague idea and a lot of questions.
For instance, Hawking writes "a matter particle, such as an electron or a quark, emits a force-carrying particle. The recoil from this emission changes the velocity of the matter particle. The force-carrying particle then collides with another matter particle and is absorbed. This collision changes the velocity of the second particle, just as if there had been a force between the two matter particles." I thought this was fascinating, and I can understand how that would cause a repulsive force in terms of classical Newtonian physics as long as the force-carrying particle has mass. But he goes on to say that some force-carrying particles "have no mass of their own". So I'm left with several questions:
1. How do force-carrying particles with no mass transmit a force? How can the ejection of a massless particle cause a recoil?
2. How do force-carrying particles generate attractive forces?
3. Does an electron in isolation, for instance, continually fire out force-carrying particles in all directions all the time to generate its electric field? Does it just have an infinite number of force particles to eject? If not, how does it "know" to emit force-carrying particles towards another electron when it comes near so as to repel it? It's no good to postulate that the other electrons' electric field compels the electron to eject a force-carrying particle because the exchange of particles is supposed to constitute the electric field.
At every turn, I'm left with these vague concepts and unanswered questions. I took three university physics courses and touched on relativity and briefly on quantum mechanics. In school, often one starts by learning equations and only later does a qualitative understanding really develop. I had hoped to better learn that second half of the puzzle by reading some qualitative descriptions with perhaps some analogies or illustrative anthropomorphisms about what an electron "wants" to do. In Hawking's defense, perhaps the difficulty in giving an intuitive description is inherent to the material which is counterintuitive by its nature.
Also, there were a lot of pronouncements of "X is true" without any explanation of how we know it's true. What experimental results attest to the truth of this proposition? Perhaps such explanations are beyond the scope of this book but they would have been interesting I think.
These difficulties aside, I did learn some interesting concepts and I still felt like the book was a worthwhile read.
Customer Rating:
Summary: Good, but hard
Comment: Well, it's very nice for those who want to understand the universe better, but it's VERY hard at the first time you read it. I decided to read it all at once, not understanding a lot of it, and going back again to try to get the idea.
Customer Rating:
Summary: unintelligible
Comment: History will look back at this best selling book and here is what it should say: This book is very lucid to those who have not read it, but it is quite unintelligible to those who have. Buy this book, it doesn't cost that much, to see how a supposedly great scientist cannot put together a coherent thought on paper. It you want to read clear scientific writing, read Lev Landau and then compare to this tripe by Hawking.
Customer Rating:
Summary: Informative, fascinating, highly readable
Comment: A fascinating, non-technical explanation of the modern concepts of theoretical physics. Full of wonder and surprise...makes us look at the world and universe with a fresh pair of eyes. A modern classic.
Summary: Highly recommended to everybody interested in Astronomy and Nuclear Physics
Comment: Stephen Hawking, one of the greatest contemporary physicists explores in a very interesting and informative way the unresolved riddles about the universe and the structure of particles, energy, time, gravity, various forces in the universe, god and their relationship with one another. His approach is both scientific and philosophical raising questions about the meaning of human existence in the universe. Although quite detailed the questions raised and alternative explanations offered are appealing both to the amateur and the professional. Stephen Hawking approaches the fundamental issues from many aspects including Newtonian physics, Special and General Relativity of Einstein, Quantum physics, string theory etc. He compares the different approaches, explains how they arose historically and the quest for a unified theory of the universe. Of course he devotes a lot of time to the primary issue of the creation and possible end of the universe. His treatment of matter and antimatter are especially interesting. I had read the book many years ago, recently I listened to the audio CD. I recommend both as a rich source of knowledge about these topics from a leading scientist on these issues.
I also recommend The Fabric of the Cosmos by Brian Green which is also a very interesting exploration of the same issues.
Customer Rating:
Summary: A bit too brief
Comment: I felt like there wasn't enough information in Hawking's explanations to really understand the concepts. So many times the fragments of information provided left me with a vague idea and a lot of questions.
For instance, Hawking writes "a matter particle, such as an electron or a quark, emits a force-carrying particle. The recoil from this emission changes the velocity of the matter particle. The force-carrying particle then collides with another matter particle and is absorbed. This collision changes the velocity of the second particle, just as if there had been a force between the two matter particles." I thought this was fascinating, and I can understand how that would cause a repulsive force in terms of classical Newtonian physics as long as the force-carrying particle has mass. But he goes on to say that some force-carrying particles "have no mass of their own". So I'm left with several questions:
1. How do force-carrying particles with no mass transmit a force? How can the ejection of a massless particle cause a recoil?
2. How do force-carrying particles generate attractive forces?
3. Does an electron in isolation, for instance, continually fire out force-carrying particles in all directions all the time to generate its electric field? Does it just have an infinite number of force particles to eject? If not, how does it "know" to emit force-carrying particles towards another electron when it comes near so as to repel it? It's no good to postulate that the other electrons' electric field compels the electron to eject a force-carrying particle because the exchange of particles is supposed to constitute the electric field.
At every turn, I'm left with these vague concepts and unanswered questions. I took three university physics courses and touched on relativity and briefly on quantum mechanics. In school, often one starts by learning equations and only later does a qualitative understanding really develop. I had hoped to better learn that second half of the puzzle by reading some qualitative descriptions with perhaps some analogies or illustrative anthropomorphisms about what an electron "wants" to do. In Hawking's defense, perhaps the difficulty in giving an intuitive description is inherent to the material which is counterintuitive by its nature.
Also, there were a lot of pronouncements of "X is true" without any explanation of how we know it's true. What experimental results attest to the truth of this proposition? Perhaps such explanations are beyond the scope of this book but they would have been interesting I think.
These difficulties aside, I did learn some interesting concepts and I still felt like the book was a worthwhile read.
Customer Rating:
Summary: Good, but hard
Comment: Well, it's very nice for those who want to understand the universe better, but it's VERY hard at the first time you read it. I decided to read it all at once, not understanding a lot of it, and going back again to try to get the idea.
Customer Rating:
Summary: unintelligible
Comment: History will look back at this best selling book and here is what it should say: This book is very lucid to those who have not read it, but it is quite unintelligible to those who have. Buy this book, it doesn't cost that much, to see how a supposedly great scientist cannot put together a coherent thought on paper. It you want to read clear scientific writing, read Lev Landau and then compare to this tripe by Hawking.
Customer Rating:
Summary: Informative, fascinating, highly readable
Comment: A fascinating, non-technical explanation of the modern concepts of theoretical physics. Full of wonder and surprise...makes us look at the world and universe with a fresh pair of eyes. A modern classic.