Customer Reviews

The Meaning of Relativity

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There are numerous books on general relativity currently on the market, and these range in difficulty from those written for the beginner or the layman, those written for graduate students in physics, and research monographs covering specialized topics. It is always refreshing to go back to the originator of the subject, and take part in his special insights on the topic. Philosophers and historians of science can definitely benefit from a perusal of this book.

The author begins this book with a discussion of the origin of the concepts of space-time, the emphasis being partly philosophical and partly psychological, and the reader can see the origin of the author's operationalism in reading this introduction. He is clearly against the philosophers who attempt to remove concepts from experience and put them in his words "in the intangible heights of the a priori". The motion of rigid bodies is used to set up a discussion of Euclidean geometry and linear orthogonal transformations. The author emphasizes the role of the physicist in discerning whether a system of geometry is true or not, contrary to the pure mathematician. Examples of geometrical invariants, such as the Cartesian line element and the volume element are discussed, along with the role of vectors and tensors. Both of these are used as means by which one can give expression to the independence of Cartesian coordinates. Maxwell's equations are put in tensor notation as an example of covariance with respect to Cartesian coordinate transformations. All of this is done to motivate the theories of special and general relativity.

The theory of spectial relativity is treated in chapter 2, the author introducing his famous principle of special relativity. The author poses the problem of calculating the coordinates and time in an inertial system moving with uniform translation relative to another. He shows how this problem is solved by assuming that time and space are absolute, and if the coordinate axes of the systems are parallel to one another, the Galilean transformations result. Newton's equations of motion are covariant under these transformations, but Maxwell equations are not (but the author chooses not to show this explicitly). He then gives an in-depth discussion of how the Lorentz transformations arise as being those that guarantee the covariance of the Maxwell equations. The author also discusses the signature of the Lorentz metric and how it is related to the light cone. He ends the chapter by developing the energy tensor of the electromagnetic field and matter.

The author's rejection of inertial frames as being priveleged leads him in the beginning of the next chapter to a short philosophical critique of the principle of inertia. This leads to a discussion of the principle of equivalence and to the origin of the general theory of relativity, a theory which the author developed, amazingly, single-handedly, and which he clearly believes is very much superior to classical mechanics. The intuition to be gained by reading this chapter is invaluable for serious students of general relativity. One can see the simplicity and power of the author's arguments, relying on keen physical intuition and sound use of mathematics. In particular, the author's heuristic derivation of the gravitational field equations from Poisson's equation is briliant. In addition, he is not ashamed to interject philosophical argumentation into his writing, particularly in his discussion of Mach's principle. Such discussions are becoming more rare among physicists at the present time.

The first half (special relativity) is an exelent resource for beginners on relativity who heve a confident handle of real variable and vector differetial calculus. The seconth half is an introductory text on Generla Relativity which is good. For this part is necesary to have also handle of differential geometry, and I recomend you to read before the article "Space and Time" by H. Minkowski in which some how the conection between the mathematical background (diff. geom.) and the physical theory is set. --- Enrique Castro Student of Physics (National University of México)---

The Meaning of Relativity is an advanced book. The title should have made it clear. Einstein delves here into what his theory
actually MEANS. That is, what must we change (if anything...) in our world conception, in the way we think, as a consequence of his immense discovery. Just think that he meddled with time, a concept static since so long that it is registered deep in our DNA: our concept of time goes back to the epoch where our main purpose was to survive the day
(sounds familiar? No, no, it was different! It was permanent. What you experience now is transient...)
So what? Read it! It is a marvellous book. Perhaps you will have to reach for other, more elementary, books, in this enterprise. All right! That almost characterizes a book worth reading. So... go on! It will repay your efforts. It IS doable. You will come out, for instance, with a precise CONSTRUCTION OF SPACE! Your brains will be enriched.You deserve that!

Laymen, such as myself, are familiar with the equation e=mc2; yet how many of us non-scientists actually know what this means? Einstein explains this in a series of four lectures. While the explaination is clear, the mathematics behind it (and the implications of relativity theory) are far from easy for the layperson to understand.

The first section on space and time in pre-relativity physics provides the foundation for exactly why his theories are so revolutionary. I was able to digest this without much difficulty. The real challenges (for me at least) began with his explaination of special and general relativity - that space, time and light are dependent on each other, and in fact are (hence the name) all relative ... a real mind-bender. Sadly, I was unable to make it through the second half of the lecture on general relativity - too abstract for one who is not a scientist by training or vocation.

Nonetheless it is a worthwhile (if difficult) read. For those who are weak in mathematics (Euclidian geometry or below) much of the details will be incomprehensable; don't let this dissuade you - part of the genius of Einstein is his ability to explain what the mathematics proves. A seminal work in science, and highly recommended for those with the patience, training or deeply committed interest in the subject.

This is not a plain English explanation of relativity to the layman. (For that, check out "Relativity: The Special and the General Theory") It is a short and sweet summary of the thinking behind and derivation of relativity in a little over 100 short pages. The target audience is physicists and mathematicians. Actually, it is probably best if you have studied relativity and differential geometry in a textbook first before tackling this one. I don't think you can learn the basics of relativity or differential geometry from this book if it's your first encounter with the subjects.

However, if you have the mathematical maturity, you will really find the "essence" of relativity in this book. As the originator of the relativity theory, Einstein can explain it like no other. After his explanation, you will wonder why no one else thought about it in this fashion, as he shows you why physics has to work this way. The key philosophical underpinnings are: (a) invariance of physics under coordinate transformations, as physical laws have to be the same no matter where/when the observations are made; and the Euclidean coordinate transformation as an simple result from classical geometry. This establishes relativity as a theory of invariants which makes the development philosophically sound and much more accessible; (b) the equivalence of all inertial reference frames (Galilean principle) and why the constancy of the speed of light occupies a central place in special relativity (the impossibility of instant communication); the results of special relativity are then derived with ease from the invariance of line segments in 4-space time; (c) the equivalence principle (the absolute equivalence of the gravitational mass and inertial mass) as the tool to remove the non-inertial reference frame as a special case. Frankly, one of the biggest confusions in special relativity was the fact that inertial reference frames are singled out as special, and yet there is no concrete proof of any kind that certain reference frames are inertial as we all know that the earth is not an inertial reference frame. In Einstein's own words: "...the general theory of relativity, ...such a superiority of conception over classical mechanics, that all the difficulties encountered must be considered as small in comparison with this progress."

With that, the mathematics (while not easy) fills in the blanks on how to get there. And Einstein's derivation was elegant and insightful. However, it is still the value of his insights and incisive understanding of the fundamental problems stand make it such a book to read. It is like comparing his derivation of length contraction and time dilation with that of Lorentz's. After reading this book, you will "understand" relativity.

This is an almost complete description of Einstein thoughts and motivations into special and general relativity along with some extra material about tensors and finally Einstein's thoughts on grand unification...
My opinion is that the book has large historical value along with some deep philosophical insights
The only minus is that mathematical formalism is out of date(along with some ideas) and surely this is not the best book to learn relativity,but can serve as an exceptional supplement for deep understanding of the subject

This book is an excellent collection of 'lectures' by Einstein himself and present the 'eventual' form of the Special & General Theories of Relativity (as in the 1950s). A handy accompaniment to undergraduate study in relativity, the book is a *mathematical* exposition into its broad features - and is NOT by any means a popular/lay account of what the theories mean. The title of the book may be a little dis-orienting in this regard - but the subtitle should lay to rest any doubts!

Einstein starts with pre-relativity physics formulated in the language of tensors and moves on to present the Special Theory using the same apparatus. The next two chapters delve really deep into the philosophy of the General Theory (GR) complete with equations. The Appendices are further advanced topics in GR - and may be of interest only to graduate students.

For a non-physicist like me, with a sufficent background in the requisite mathematics and some prior exposure to the topic, this book was a real treat. It is a classic well worth its place in a personal library. This book is, however, not recommended for those who are looking for something along the lines of Hawkings' A Brief History of Time.

If you want to understand this book, you had better understand tensor calculus or you will be lost. I had to purchase a book on tensor calculus to get through it. Be ready to struggle through the math, but it will be worth it since you will learn new ideas . Tensor calculus is not easy, but worth it. Relativity math is not easy.

Other reviews didn't mention that the Appendix contains the only generally accessible details of Einstein's last attempt at a "unified field theory," by which he hoped that the gravitational and electromagnetic (and possibly other) fields would be shown to be aspects of a single fundamental entity. This book, along with Schroedinger's "Space-Time Structure," inspired my own technical work leading eventually to my 1977 Master's thesis. (At that time, indulging in such work was very much frowned upon by the physics establishment.)
This book is not suitable for use as a textbook in these areas, but as a supplement it can provide valuable insight into what Einstein's was thinking.

Albert Einstein deserves as much credit for popularization of science
as he does for his great theories and their effect on thought for his whole century.
In this book he doesn't spare the equations for the timid.
Yet it is still one of the most loved classic of modern physics by
everyone. He challenges us all to come up to his level of thought.
But at the same times gives us the means and logic to do it with.
Although small and Jewish, he was a giant among scientists.
This book like Newton's Principia will be read by generations of the far future.