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on June 8, 2002
First of all, If you have already read some books on black holes and worm holes/time travel, you probably won't learn much from the book as it is non-mathematical (the only equation is E=mc^2) and introduces only the fundamental aspects of time, space and time travel. Otherwise you might want to take a moment and read on before buying it.
I understand that most authors spend a lot of time on their books, even though the books themselves might not stand out in the end. As such, I am really reluctant to give their books any low grade. But this book really has little to deserve my praise, so I give it a 3.
The book is rather short. English is not my native language, but I still finished it in 3 hours in a bookstore.
I feel the book is divided into 3 parts: first part introduces relativity (including things like light and gravity) and black holes; second part discusses how to construct (at least in theory) a worm hole that can be used as a time machine; and the last part deals with the paradoxes and implications of time travel.
I think the author was not sure what level of audience he's targeting. The first part is easy to understand for everyone. But that is not what audience want to learn from the book--they want to know about time machines. So they turn to the last two parts, which may be a bit hard for them. For instance, the author mentioned rotating black holes, but nowhere in the book he explained what they are. He also mentioned their ring-like singularity but he didn't even put a drawing to help readers to understand. I am quite serious about science and I read a few books on the subject so I know what rotating black holes are like. But I really don't think everyone knows about them and the author shouldn't assume thate either because the first part limits the book to general audience. There are many more examples like this in the book.
This actually is embedded in a more serious problem: the book is generally lacking much needed information and explanation. When I read about black hole I expect to find the words "event horizon" and "singularity". Actually I found the latter, but the first is only vaguely described and never stated directly. When the book talks about gravitational lensing, it would be really helpful to include a drawing to show how it works, but you can't find that either. How about the Casimir Effect that creates negative energy? (negative energy is explained in the book.)The author says it relates to virtual photons, but what are those? And honestly I don't think the author clearly explains the Casimir Effect either. He simply states the things he needs and expect you to take them for granted. But if you give a little thought on the subject, I am sure that you will have tons of questions unanswered. So after reading it you might not have a firm grasp on the subject.
Also around page 15 (might be 13 or 17), I believe the author made a mistake. The book says if you half the diameter of the earth the gravitational force on the surface of the earth is 2 times as strong. This is NOT true. It should be 4 times as strong because force F is inversely proportional to the square of the distance. [F=GMm/(R^2), where G is the gravitational constant and M's are the attracting masses, R is the distance between the masses, which in this case is halved] I am sure the author overlooked this, but since it is such a fundamental thing and he highlighted the paragraph in the book, there is no excuse for the mistake.
The reason that I am giving it 3 stars and not less is because the last two sections of the book are interesting to me and I learned something (although not much) from reading them. I am not saying that you will not like it, in fact many reviews before mine gave it a 5 star. But I strongly recommend that you first take a look at it, in a bookstore perhaps. Maybe you can finish the book like I did if you have the time.
Because I didn't read that many books on the subject, I can't tell you which ones are the best. But for a better description on the subject (black holes/worm holes/time travel) you might find Clifford Pickover's "Black holes: a Traveler�s Guide" interesting.(New York: John Wiley & Sons, Inc. 1996.) It has some equations but they are not that hard to understand, the book introduces probably everything you ever need to know about black holes. You can find more about black holes from Stephen Hawking's "A Brief History of Time", and from the time travel authority: Kip Thorne's "Black Holes & Time Warps" (but this one is a bit harder). I also liked Brian Greene's sections on general relativity and quantum mechanics in his "The Elegant Universe", he explains the subject so clearly and provides so many insights. (If you have a question then you can be sure to find the answer in the next paragraph. A perfect 5 star if I were to rate it) John D. Hawley & Katherine A. Holcomb's "Foundations of Modern Cosmology" (New York: Oxford UP, 1998.) is also an excellent book, but I suggest you borrow it from library since it is rather expensive ($50 I believe, it has a section on black holes, probably like 30 pages, it also has a chapter on relativity).
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on March 2, 2002
Paul Davies is a great author. But some readers may find some of his books long as books usually are. This one not. It is short, but clear cut goal-oriented and conceptually deep. You will understand some concepts that seemed so confusing too you. Most of all, you will see things under a different light. Physics at its best. Just a warning: you can read it in an afternoon, but you will probably become so interested that you will want to spend a lot more time with wonderful books and subjects like these. The fun will last only about 150 pages.
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on May 29, 2003
Davies has attempted a very difficult task: how to write a brief and easily understood account of the physics and mathematics underpinning the idea of time travel.
In the main part Davies succeeds admirably. It is clearly not that simple to condense highly complex mathematical equations, and concepts of and about quantum physics to a level that the ordinary person will not only grasp but perhaps think about.
The book is effectively divided into two parts. The first is a synopsis of the theories underpinning time travel. In this section Davies provides a speedy overview of the history of thinking about time travel, the development of the theories, and he attempts to at least conceptually work through the possibilities and problems associated with the main theories that hold currency.
In the second part, Davies sets out the mechanics of how to build a time machine. The content contained in is part, not matter how hard Davies tries, and despite its brevity, was very difficult for this reader to understand. Having no background in pure physics, I became a bit lost in places. But struggling through out, it is still informative and challenging.
Overall, the book is a valuable starting point for the general person to get a grip on this though provoking topic.
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on December 31, 2015
I purchased this book for my 12 year. He's taken an interest in Quantum physics. He has kept such an interest in this book I am beyond amazed. He keeps it with him with his notebook and dictionary handy. There are some words he comes across that he's not familiar with which is completely understandable. This isn't a book for a 12 year old. It truly explains the concept of time travel not as a fantasy but as what you would have to do in order to achieve such a goal.
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on February 2, 2015
I prefer this book slightly more than Brian Clegg's book by the same title. It introduces an essentially scientific view of time travel, and in that respect is easily imitated, and not entirely without merit. I found the content, because of the scientific view, somewhat boring and familiar.
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on March 17, 2002
Those with a theoretical interest in time travel will appreciate Davies' attention to explaining in detail the intricate theory behind the components of time travel. I think the real winner though will be the engineer with a slant toward the practical application side. Davies' presents a potential design (complete with flow diagram!) of the process steps needed to construct a time machine. Theories of black holes, worm holes, gravity, anti-gravity, causality etc. are presented in crisp yet coherent detail.
As a literary style, I at first didn't care for the many cartoon type drawings which decorate nearly a quarter of the book, but as it went on I realized that not only where they illustrative to the the book's finer details, but also a symbol for the fanciful possiblity of time travel. Reader's with further interest will also appreciate the detailed bibliography.
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VINE VOICEon June 30, 2004
Well, I hate to ruin it for you, but Davies isn't really telling the reader "how to build a time machine" so much as he is taking advantage of a gee-whiz slice of science fiction fun to build a quick tour of the fundamental theories of modern physics.
"So can it really be done?" asks Davies, one of the most frequently cited mathematical physicists of our day. And away we go, flying through the ideas of Newton, Einstein, Gödel, Hawking, and Penrose, and leaping into wormholes in space-time. As we go, the great modern physical theories come into play one after another. Davies is good at this. Quickly treated are singularities, entropy and the arrow of time, the special and general theories of relativity, exotic matter, antigravity, the topology of space-time, quantum uncertainty, and other stuff including a bevy of time-travel paradoxes.
To be sure, the author describes time machines that 'might' work. "So can it really be done?" Again, I don't want to ruin it for you. But some reviewers seem to have come up with the wrong answer. Here's a hint, "The purpose of science is to provide a consistent picture of reality, so if a scientific theory produces genuinely paradoxical (rather that merely weird or counterintuitive) predictions, that is a very good reason for rejecting the theory" (p 123). This isn't going to be remembered as one of Davies more important books (I recommend 'The Mind of God' and 'The Matter Myth'), but this is aimed at a different audience/readership.
A fun little book.
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on June 3, 2002
Paul Davies book "How to Build a Time Machine" is a good book with an entertaining thesis: he is of the opinion that it is theoretically possible to build both a forward and backward time machine. The engineering problems, however, are of an aboslutely staggering scale, and the project is not, by current standards, a practical one. Nevertheless, Davies has fun with the concepts.
Davies also gives a good overview of the various theories of how time travel might be accomplished, and the book is very useful in showing the layperson that time is, indeed, relative.
My only complaint with the book is that it is somewhat derivative of his earlier work, About Time. Part of this is not Davies' fault -- the concept of the flexibility of time is usually so shocking for people that he feels the need to explain this first, and so both books discuss some similar ideas, such as the Paradox of the Twins, etc.
I recommend About Time to people (usually who don't believe me when I explain that time is relative), and those who read it come away stunned; the book is a marvelous explanation, in layman's terms, of how Einstein's theories work with regard to time. If you have not read About Time, read this one first as it will familiarize you with the concepts Davies' discusses here. This book is a good follow up to About Time in that it turns to the "engineering" problems involved in building a time machine.
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on August 22, 2002
This book was a very interesting look at what it would take to build a time machine, but it's only 128 pages. Don't expect to go build one after reading this, but at least when you finish you can poke fun at star-trek. It's a quick read, but it's worthwhile.
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on April 10, 2002
I am almost done reading How To Build A Time Machine and so far it is remarkably easy to understand. This book is perfect for people wanting to get a general idea of the physical possibilities of time travel. Davies does a great job of putting the physics of time travel into lamens terms. I think anyone remotely interested in time physics should start here.
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