| A BRIEFER HISTORY OF TIME Stephen W. Hawking Leonard Mlodinow New York: Bantam Books, 2005 |
Rating: 5.0 High |
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| ISBN-13 978-0-553-80436-2 | ||||
| ISBN 0-553-80436-7 | 162p. | HC/GSI | $25.00 | |
There are plenty of books on the abstruse concepts of astrophysics and cosmology. Some are written for students of those fields, some for the layman, a few for juvenile readers. There are plenty, but not enough. Many people will not read those books, because they do not go to libraries to seek them out. It takes a popular name to catch their attention and induce them to buy the book — perhaps for themselves, perhaps as a gift. The late Carl Sagan had such a name, but his forté was planetary science and he wrote most of his books about his other interests, anthropology and the politics of nuclear weapons. His best-known work is the PBS television series Cosmos.
Before Sagan, Isaac Asimov was the best-known and most prolific popularizer of science. But Asimov died in 1992, Sagan in 1996. The mantle of best-known scientist, at least in astronomy, now falls on theoretical physicist Stephen Hawking, whose work on black holes revolutionized our understanding of those singular phenomena. He wrote his first book, A Brief History of Time, in 1988. It became an instant best-seller and made Hawking a household name.
Many requests from readers led to a rewrite of that work. This time around, Hawking teamed up with writer and Caltech physicist Leonard Mlodinow. The result of their collaboration is this book. Shorn of much of the technical material found in its predecessor, it leads the reader through the discovery of cosmology: the shape of the Earth and the layout of the solar system; Einstein's Theory of Relativity; the fact that the universe is expanding and the nature of that expansion; black holes; quantum theory; superstrings. The historical information — brief profiles of Albert Einstein, Galileo Galilei, and Isaac Newton — have been preserved in the back of the book.
The explanations of these topics are, for the most part, accurate and coherent. However, there are a few passages I found unclear or ambiguous. I discuss these below. In general, the authors have done an excellent job of explaining the current state of cosmology to the lay reader. Color illustrations complement the text well1, and it has a good glossary and index.2 I found it a bit oversimplified, and I wished I had been able to give it an editing pass to straighten out the omissions and ambiguities, tighten up the writing, and remove a few exclamation points, say. But it's a competent job, and no one will regret reading it or buying it.
Speaking of Aristotle's arguments for the world being a sphere, the text states on page 6, "If the earth were a flat disk, its shadow would be round only if the eclipse happened at a time when the sun was directly under the center of the disk." How, at this early stage of investigation, could Aristotle know that was not the permanent earth-sun arrangement? I presume he watched a large number of solar eclipses and never saw the moon cast an elliptical shadow. But the text does not explain this. FIX THIS.
The second argument for a spherical earth is that the tops of approaching ships are seen first. Ptolemy's elegant experiments in Egypt with poles and their shadows is not mentioned. I feel this is a serious lack.
On page 8, in a discussion of Ptolemy's eight "crystal spheres", there is this: "Each sphere was larger than the one before it, something like a Russian nesting doll." Can most readers be expected to know what a Russian nesting doll is? Or a Fabergé egg? or a Matriocha sphere? A bit of extra exposition would expedite understanding.
Further to the crystal spheres, "The inner spheres carried the planets. These were not fixed to their respective spheres as the stars were, but moved upon their spheres in small circles called epicycles." I read this as saying that the planets moved on the surfaces of the spheres. Thus they must have described circles normal to the lines connecting their centers with the observer. Were the five known planets, then, seen to move above and below the plane of the ecliptic, as this implies? Or was retrograde motion the only visible result? (The accompanying picture shows the epicycles projecting in front of and behind the spheres, which would fit the actual observations better.)
Page 11 Tells how Newton explained the motions of the known planets. Then it says, "Without the concept of Ptolemy's spheres, there was no longer any reason to assume the universe had a natural boundary, the outermost sphere. Moreover, since stars did not appear to change their positions apart from a rotation across the sky caused by the earth spinning on its axis, it became natural to suppose the stars were objects like our sun but very much farther away." This is quite a leap of imagination, so I suspect the authors left some details out.
Page 14: "Any physical theory is always provisional, in the sense that it is only a hypothesis; you can never prove it." This is perfectly true; but, technically, a hypothesis is weaker than a scientific theory. Making them equivalent in this way not only risks confusing the reader, it potentially strengthens the Creationists' case against the theory of evolution. Also, it attempts to explain one technical term by means of another, perhaps even less familiar one.3
Anent the "Theory of Everything", pages 16 and 17 contain these two sentences: a) "Unfortunately, however, these theories are known to be inconsistent with each other—they cannot both be correct." b) "Now, if you believe that the universe is not arbitrary but is governed by definite laws, you ultimately have to combine the partial theories..." There are excellent scientific reasons why both GR and QM are inadequate, and good ones for supposing that any new theory which explains what they cannot may supersede them. But readers for whom this book is intended may not know that, and may well wonder where it is written that there has to be just one all-encompassing law of nature. This explanation strikes me as too dogmatic. (See pp. 133-5.)
Page 23: "...the two bounces would seem to take place about forty meters apart..." The speed of the train is never specified. From a quick calculation. I assume they mean 90 mph. [40m/s = 131fps = 1.49*(88fps) = 1.49*(60mph) ≅ 90mph]
Page 38: "Technically speaking, a geodesic is defined as the shortest (or longest) path between two nearby points." Why the apparent contradiction? And why limit it to nearby points? And, if you're going to get technical, putting a value to "nearby" would be helpful.
Page 41: "...the mass of the sun curves space-time in such a way that although the earth follows a straight path in four-dimensional space-time, it appears to us to move along a nearly circular orbit in three-dimensional space." Wow: a straight path in spacetime. Who knew?
Page 46: "Finally, suppose there is an observer at the ceiling of the rocket ship and another at the floor, each with identical clocks that tick once each second." Wow — a rocket ship one light-second long with a very high ceiling. As Eleanor Arroway once almost said, "It seems like a terrible waste of space."
Pages 48-9: "Just as we cannot talk about events in the universe without the notions of space and time, so in general relativity it became meaningless to talk about space and time outside the limits of the universe." I can't quite see how this relates to previous discussion, and can only suggest that it did not make it into print exactly as the authors intended. (Later, I realized this relates to page 103, where it is pointed out that quantum gravity removes the singularity at the Big Bang, the "lower limit" of the universe. It's still more obscure than it needs to be.)
To contact Chris Winter, send email to this address.