By 1916, Albert Einstein was a world-famous professor of physics at the University of Berlin, and he had seen several scientists and popularizers write books about his special theory of relativity, which he had first published in 1905. Other such books, published between 1913 and 1916, even included some of his preliminary ideas on the general theory of relativity. With the success of several of these popularizations, he knew that a large and willing audience was available to learn about the theories of relativity from the man who created them. Having spent the majority of his scientific career communicating with colleagues via journal articles that made heavy use of advanced mathematics, Einstein realized that he would need a different way to convey his discoveries to a lay readership. When, in the fall of 1915, he started thinking about how to make his ideas understandable to nonscientists, his work on the general theory of relativity was effectively complete, but his personal life was in turmoil, and all of this would play a role in the book’s composition.

In 1914, Einstein had separated, not amicably, from his first wife Mileva and their two sons, but he was not formally divorced until 1919. During the interim, he formed an intimate relationship with his cousin Elsa Löwenthal, who had been married and had two teenaged daughters, Margot and Ilse. Einstein became friendly with the young girls, and in papers kept secret for many years scholars would later discover correspondence from Ilse in which she wrote that Einstein loved her “very much, perhaps more than any other man ever will,” and that he was “prepared to marry” either her or her mother. After Einstein’s marriage to Elsa in 1919, Margot and Ilse became his stepdaughters.

As Einstein wrote Relativity, he read aloud the completed pages to Margot, in the hope that if a teenager could understand his book then other nonscientists would as well. Scholars have compared surviving fragments of this manuscript with corrections in later editions and have detected the handwriting of Ilse. Einstein experienced some difficulty in getting started, but, driven by a desire to make his ideas widely understandable, he completed the manuscript by December, 1916. At the time, he told a friend that his presentation was so simple that a high school student could understand it, though he was unhappy with the book’s style, which he characterized as “wooden.” Nevertheless, German publishing house Vieweg in Braunschweig published Relativity in the spring of 1917, and it enjoyed rapid success. Several other German editions and many translations followed. Einstein sometimes added new prefaces to these translations, and he also made corrections and additions to both the German and the foreign versions. The book passed through fifteen German editions during Einstein’s lifetime (though there was no fifteenth, and the last one, labeled the sixteenth, was published in 1954).

Einstein structured his book in three parts: The first part, comprising seventeen chapters, is on the special theory of relativity; the second, comprising twelve chapters, is on the general theory; the third, comprising three chapters, is titled “Considerations on the Universe as a Whole.” Einstein warns readers that, despite the book’s brevity, patience and willpower will be required to grasp the main ideas and their justifications. He first reviews the basic concepts of Euclidean geometry and Newtonian mechanics before beginning his treatment of special relativity in the sixth chapter, “The Apparent Incompatibility of the Law of Propagation of Light with the Principle of Relativity.” Einstein had become aware of this incompatibility as a teenager, when he wondered what he would experience if he could travel as fast as a light wave. This thought experiment led to a dilemma that necessitated the abandonment of either the classical principle of relativity, which was based on the laws of motion discovered by Galileo and Sir Isaac Newton, or the classical laws of the propagation of light, based on the work of James Clerk Maxwell and others. Einstein discovered a way out of the dilemma by reasoning from two postulates of invariance: the constancy of light’s speed in uniformly moving systems and the...

(The entire section is 1748 words.)