Customer Reviews

Relativity and Common Sense: A New Approach to Einstein

5 star:		(3)
4 star:		(2)
3 star:		(1)
2 star:		(1)
1 star:		(3)

 

 

After several chapters reviewing concepts, many of which are quite irrelevant to the subsequent discussion, Bondi gives one of the most original derivation of Special Relativity that I have ever seen.

Unfortunately, Bondi does make some serious mistakes. For example, he conflates "time" and "elapsed time", which is analogous to conflating "position" and "distance". Second, by claiming that the laws of physics only apply to inertial reference frames, I think the author impedes the understanding of general relativity.

The author does deserve credit for using the correct formula for time dilation, not the naive gamma factor.

For an introduction to special relativity from the K-calculus standpoint, this book has no peer. The K-calculus approach is, arguably, the soundest approach for conceptual clarity all the way to the composition of velocities and twin paradoxes. You won't feel you are being snowed by math tricks. In paperback, this book is high value for the money. Don't look for recent stuff like superluminal physics or details on relativity experiments.

Although this book doesn't dive deep into the equations for Einstein's Theory of Relativity, it is an *excellent* book to learn the ideas behind it. Relativity is a complex idea and this book will explain well to anybody who takes the time to read it and think about things.

One must give Hermann Bondi credit for his unique presentation of the concepts from Einstein's Theory of Relativity. To well-educated (at least in physics and mathematics) readers who are familiar with Einstein's Theory, Bondi's approach is insightful. However, for those looking for an alternative way to understand the Theory, prepare to be disappointed by Bondi's presentation. The book continuously uses mathematical jargon which is of course unstandable to those familiar with university mathematics, but that is not at all familiar to everyday folk (example: describing the origin of a graph as the point where the coordinate values "vanish" would confuse those who don't realize that "vanishing" is somewhat of a math slang for the values equaling zero.) At times Bondi trivializes sequential math steps in order to simplify his presentation, but then offers every detail in describing the order of events he offers for his characters; in effect, he loses touch with less familiar readers and creates a loathesome Abbott-and-Costello-type dialogue for familiar readers. For the typical reader that wants a general familiarity with Relativity, I would recommend Einstein's own offering for such readers, RELATIVITY: THE SPECIAL AND GENERAL THEORY.

Previous reviewers who rated this book less than four stars have simply misunderstood the purpose of this book. It uses a novel approach to present the special theory of relativity to an audience of non-physicists who are not afraid of a few - very few - equations, as in the proverbial "educated high school graduate." Hence Bondi uses numerical examples to avoid many equations. The book is not meant to be a college textbook or complete treatise on relativity!

Bondi's approach makes relativity seem almost obvious. The earlier chapters, which some felt were irrelevant, are designed to contrast sound with light, which may be more familiar, or at least less surprising. There is a lot of physics in this book

Some may be misled by a statement in John Durston's preface: "Professor Bondi derives Relativity from Newtonian ideas." One cannot derive relativity from Newtonian mechanics. But Newtonian concepts can be used to advantage.

My only caveat is that there are several unfortunate typos, especially Eq. (20) on page 123.

I have read several relativity-for-the-layman books, including Einstein's own work, and this one got the points across to me the best. After digesting this book I could convincingly explain the time dialation (and coriolis effect) on a cocktail napkin. I think for the lay person, understanding of this stuff can be highly personal: dependent upon if the teacher "speaks to" you. In my case, Bondi spoke my language.

There's no doubting Bondi's credentials or the potentiality of his thesis on the common-sense derivation of special relativity from Newtonian physics, but Bondi fails on two basic fronts:

1) The bulk of his presentation relies on a cumbersome supposition (graphical and otherwise) involving several characters moving through space and time to prove that time is a route-dependent quantity. If the reader wants to truly understand Bondi's theory, he or she should plan to sit down with a chalk board or a paper and pen in order to keep the character's names and their travels straight.

2) The basis for the presentation is so tedious that eventually one reaches the point of sensory overload and, as a result, ends up accepting the conceptual foundation of Bondi's theory as is -- which is no different than taking Einstein's special theory of relativity at face value. In other words, for this reader, Bondi fails to convincingly derive special relativity from Newtonian physics.

This is one of the first books which use common sense approach to the understanding of special theory of relativity using illustrations, drawings and diagrams. At one time this theory was considered mysterious, which is in fact obvious and clear-cut extension of ordinary ideas to the realm of high velocities. The author first presents Newtonian ideas followed by the concept and characteristic effects of special relativity in a non mathematical language. Then he introduces Lorentz Transformation (LT) in chapter 10, which involves systems of coordinates moving relative to each other and then uses LT to establish the basics of the theory. Readers with very limited mathematical background should have no trouble in understanding the elementary aspects of the relativity. This is a cute little book (177 pages, size 7.92'' x 5.36"), which is classified into three parts. The first part introduces the classical mechanics; concepts of force, momentum, angular momentum, velocity of light and uniqueness of light. The second part deals with the peculiarities of high speeds, relationship of inertial (uniformly moving, constant velocity) and moving observers and the need for theory of relativity to understand high speed situation and a brief introduction to Lorentz Transformation. The final part discusses the consequences of traveling faster than light, acceleration (non-inertial motion) and high velocities on mass. Chapters 8 and 9 are crucial to the common sense approach to the understanding of relativity. The reader may need time and patience to read these two chapters to understand relativity. Chapter 11 discusses some interesting consequences of special relativity; for travels faster than light there is no link between cause and effect, in other words that effect could precede cause. This book is very affordable and useful; I encourage the reader to consider adding this book to his/her personal library.

The basic theme of this book about relativity and common sense is so far stretched that one could call this a con job. Like the editor must have warned Bondi to stay away from equations so as not to turn off the average potential reader thumbing the pages, but we have pages and pages of mental figuring with three characters with individual names to boot.

Where he is really caught is in a diagram that is supposed to indicate the obviousness of a 30 degree rotation around the origin. Here 1/2 and the square root of 3 divided by 2 manage to show up, with absolutely no explanation at all. Apparaently he was afraid to say sin(30) = 1/2. Thus somebody who really did not know that would have absolutely no clue about how this self-evident diagram really worked!

Thus, as I say, it is con job. A preposterous attempt to link relativity and common sense, like everybody should think in microseconds of light, not feet. (Just try to explain to some youngster how a 8.5 x 11 inch paper is in fractions of a microsecond.) Anything else to Bondi being "degenerate" thinking. I guess he manged to fool even himself.

Yet, he does have his own way of looking at it, so if the subject of relativity usually results in drawing a blank sooner or later, well, this approach has a certain merit as a novel way of approaching the subject. It is possible to learn something from him.

Bondi has a very novel and easy to follow approach to deriving time dilation. He uses a handful of travellers / observers moving relative to each other at subluminal speeds sending light pulses to each other. Unfortunately his derivation would just as well work and 'prove' time dilation if subsonic travelers were sending sound signals to each other.

Time dilation at one milionth of the speed of light? That would regarded ludicrous even by the most fervent believer in Einsteins 2nd postulate for Special Relativity (SR).

The author just takes the 2nd postulate for granted without even saying so, much less any justification for that counterintuitive assumption.

The book, like unfortunately many others about SR or GR, requires this leap of faith on the part of the reader, although very well hidden in this case. Not that he intends to deceive, the author apparently never questioned his own leap of faith. In other words, he does not apply the 'common sense' that the title promises.