Cosmology View

My views on Cosmology and Physics

site navigation menu


Review of Einstein's 1920 Book on His Theories of Relativity

My initial motivation for this exercise was to learn Einstein's justification for his famous energy equation of E=mc^2.

This simple equation, which is always associated with him in academia and is part of his celebrity status in the general public, never occurs in his 1920 book, let alone its explanation.  It is only implied in his explanation of a proposed change in inertial mass of a moving body. However, the book's first use of mc^2 suggests this term was described earlier. As it wasn't, Einstein might have recalled an earlier reference but which was not within this book as published.

Despite that surprise,I analyzed the entire book, but excluding tis references. Einstein published his book  in 1920, so all references are before that year. Finding them now would be very difficult (if not impossible), so I reviewed only his content, not that of others.

Einstein's impact is not just the simple equation. The review reveals more of his impact, though limited to only topics in this book.

Since this book was published in 1920, he cites the results of the 1919 Eddington Experiment.

He also mentions redshifts which arose in 1912.

He describes the impact of relativity on cosmology.
According to the translator, that appendix related to cosmology  was added for the 1920 edition of the book.

I could not find an English translation of his original 1905 papers.

I can only hope the translation of Einstein's book accurately presents Einstein's reasoning when he had published them in 1905. This book presents his descriptions of his theories in 1920 .

I cannot know why his famous equation was not part of his 1920 book, which was written after the famous confirmation in  1919 of his prediction of starlight bending during a solar eclipse.

My review did not require an analysis of the equations for space-time curvature. Therefore, the reader is not confronted with reading Einstein's complex math. The review is about the basis for that complex math.

This review presents the public domain text by Einstein. That pdf format spanned 186 pages, covering 33 distinct sections of material. This is a very long review of a book by someone who had a significant impact on physics..

Einstein used coordinate systems and their transformations. These terms are described by me, rather than just a link to another site, in a background section I added, to accompany the sections of the book.

This review becomes one of his understanding of  Newton's gravitational field, compared to Newton's force, measuring events in space and time. Some readers will know of his story of observers who are on or off a moving train, including one who is walking on the moving train.  This walking person could carry a light source.  These different observers can report their observations of lightning strikes outside of the train. That story involving different observers is the basis of several of his important conclusions about motion.

As the book is over 100 years old, I present the original content, translated to English, for the reader to decide both whether I am fair in my analysis of his descriptions of his theories, and whether my conclusions are justified.

It is important to read his words, without expecting to read what you were taught, which was someone's interpretation of Einstein's words, from their context.
I expect that few have read a book by Einstein.

Some might know of his thought experiments.

I have the link to the original text, in a pdf, at the start of my review.

You can read the original before reading or skipping my remarks on the original content,

Einstein cannot be given a pass or be immune to criticism, just because of his name.

If someone feels I am too harsh on Einstein, the problem remains the naive acceptance of Einstein's theories, not Einstein, who seemed to be part of a clique, including his professor Minkowski. No peer review was needed in the clique.

Review of Einstein's Book on Relativity

date posted 05/07/2022