Sidelights on Relativity

This is the first book of I have read in which Einstein wrote directly rather than the many reiterations of his works. Sidelights on Relativity is a two part book of lectures in which he gave in 1920 and 1921. The first titled "Ether and the Theory of Relativity." Einstein explores the concepts given by Newton, Maxwell and Lorentz of the ether arguing the universe is not mechanical in nature. The other argument is the purely physical aspect in which the mechanical perspective seems to propose what is seen is that exists, and/or can be measured and proven to exist. That "space without ether is unthinkable," that is, the effects of spce/time gives credence to ethers existence just as "the undulatory surface forming the boundary between water and air alters the course of time." This, then, creates the contradiction. The second lecture is titled "Geometry and Experience" in which Einstein argues Euclidean geometry by noting the difference of experiencing and proposing laws of earth-measurement. He demonstrates this through the plane and the globe asking the reader to imagine the globe and a plane. While the plane is infinite in all directions, similarly one can fill the plane up infinately. This is not an all together accurate picture of our universe. Rather if we imagine a sphere and fill that up, we realize only a finite amount can fill up the space.

At this point, I will say that my understanding stands at a finite point in which it would be only arrogant for me to claim I understood the entirety of the book. Nonetheless, I found this book completely readable, mostly due to the fact that there are no formulas to follow. My knowledge of relativity is limited and I have given you what I believe I understand. Its a short book with the writing clear and concise and logical; which surprised me hearing stories about Einsteins genius in which he is unable to explain in laymans terms. Highly reccomended!

This 56-page Dover edition offers two lectures by Albert Einstein, "Ether and the Theory of Relativity" and "Geometry and Experience". The lectures are described as "devoid of complicated equations and abstruse terminology". Nonetheless, while the reader does benefit from Einstein's clarity of thought, these lectures do require careful attention. The first lecture presumes familiarity with physics; the second is largely a discussion of non-Euclidian geometry and is easier reading.

Ether and the Theory of Relativity, an address delivered on May 5, 1920 at University of Leyden:

Einstein recounts how the concept of ether originated and subsequently evolved. After some discussion of work by Hertz, Maxwell, Lorentz, and Mach, he notes that it became possible to take a position that ether does not exist. However, using an analogy of water waves, he explains that although the special theory of relativity does forbid us to assume ether consists of particles observable through time, the hypothesis of ether in itself is not in conflict with the special theory of relativity. Only we must give up ascribing a motion to it.

While it may seem superfluous to postulate a homogeneous, isotropic, ether-medium, Einstein contends that to deny the ether is ultimately to assume that empty space has no physical qualities at all. He then argues that according to his General Theory of Relativity "empty space" in its physical relation is neither homogeneous nor isotropic, compelling us to describe its state by ten functions (the gravitational potentials). There can be no space or part of space without gravitational potentials.

After noting that elementary particles may be considered condensations of electromagnetic fields, he concludes that our current view of the universe presents two realties which are completely separated from each other conceptually, although connected casually, namely gravitational ether and electromagnetic field, or as they might be called, space and matter.

Geometry and Experience - an expanded form of an address to the Prussian Academy of Sciences in Berlin on January 27, 1921:

Einstein begins by posing and answering why mathematics, a product of human thought, is so admirably appropriate to describing reality. In exploring limitations associated with applying Euclidian geometry to relations between rigid bodies, Einstein introduces other axiomatic systems, including Riemann's geometry. He argues that there are difficulties in applying geometry on the sub-molecular level, but it is less problematical to extend the ideas of geometry to cosmic orders of magnitude.

After some clarification of the meaning of a finite universe and an infinite universe, he devotes several pages to illustrating how to visualize a finite, three dimensional universe that is unbounded. Einstein concludes this lecture with an enthusiastic comment: "My only aim today has to show that the human faculty of visualization is by no means bound to capitulate to non-Euclidian geometry."

Clear and important essay on the relationship between geometry and physics and our prejudices about it. Similar essay on the history of the ether and how it evolved to fit data. An unmatched depth of understanding presented succinctly and clearly. Good read for both those with passing understanding of relativity and those with deeper understanding who want to see Einstein's clear thinking on paper.

I read This book and I would like to buy it. However I do not use Credit cards, only Debit cards, Best Regards, Professor Gerardo Paredes F