Science is a powerful potion whose consumption converts a dogmatic to a sceptic, and like travel, is fatal to prejudice and pride. But much of science is not popularized and it's depth and concepts are accessible to only unkempt haired, bespectacled, equation-wielding, greek alphabet ace stereotypes whom we brand as scientists. Bertrand Russell, a thinker, philosopher and mathematician, in this book attempts to explain the mysteries of Einstein's theory of Relativity to the common man, a person who has the thirst for this knowledge, but doesn't have the depth or expertise to understand the mathematical intricacies behind it. The 200 pager ABC of Relativity is one of a series of books written by Russell on different topics in science. This 1925 book, written 7 years after Einstein's General theory of relativity, is a credit to Russell's open-mindedness and foresight, personal attributes that are far ahead of his times.
Russell starts off the book by urging the reader to give up thinking in terms of Euclidean geometry and Newtonian physics that we are so used to on earth, a pre-requisite for understanding the theory of relativity. He moves on to explain the misconceptions about the theory of relativity and to describe the properties of light, particularly it's velocity. Russell introduces the Michelson-Morley experiment to measure the velocity of light, whose results called for a new theory, the special theory of relativity. In the middle chapters of the book, the author introduces concepts like the constancy of the velocity of light, time dilation, object length alteration in the direction of motion, Lorentz contraction and space-time, essential concepts behind the Einstein's special theory of relativity.
Russell's explanation of concepts is neither rhetorical nor mathematical, making it very powerful as it can be understood by anyone. His examples are very "earthly", involving objects that we see everyday. After explaining the special theory of relativity, Russell moves to harder concepts like gravitation, formed by space-time hills leading to the general theory of relativity. Personally, I felt concepts around accelaration and gravity a little harder to understand. Perhaps the concepts here are a little more abstract and hard to visualize and imagine. The author also explains the vastness of our expanding universe, sowing seeds of humility in the reader. The book concludes with some philosophical insights.
Overall, a fantastic attempt at popularizing the theory of relativity. After reading the book, I did some research on the web for more attempts at simplified explanation of the theory and here is an article that attempts to explain the theory in 4-letter words or less.