Relativity: The Special and the General Theory began as a short paper and was eventually published as a book written by Albert Einstein with the aim of giving:
. . . an exact insight into the theory of relativity to those readers who, from a general scientific and philosophical point of view, are interested in the theory, but who are not conversant with the mathematical apparatus of theoretical physics.
- from the Preface
It was first published in German in 1916 and later translated into English in 1920. It is divided into 3 parts, the first dealing with special relativity, the second dealing with general relativity and the third dealing with considerations on the universe as a whole. There have been many versions published since the original in 1916, the latest in December, 2011. The work has been labeled by whom?] unique in that it gives readers an insight into the thought processes of one of the greatest minds of the 20th century.

To quote Einstein himself, this slim volume was "intended, as far as possible, to give an exact insight into the theory of Relativity to those readers who, from a general scientific and philosophical point of view, are interested in the theory, but who are not conversant with the mathematical apparatus of theoretical physics." Despite his formidable intellect, Einstein writes in a clear and engaging style, using familiar examples to illustrate his theories and their surprising conclusions. Anyone with a curiosity about the man, and his often misquoted theories, would do well to settle down with this book in a comfortable chair, and shut the door - you will need to think and imagine hard to keep up with Einstein Delve into the world of the infitinely small, infinitely large, and lightning fast, and at least scrape the surface of these two great concepts which laid the foundations for atomic, nuclear and quantum physics in the following decades, and made space flight and modern astronomy possible.

World-renowned theoretical physicist Albert Einstein was interested in explaining the theory of Relativity to people who were not especially well-versed in higher mathematic concepts and theoretical physics. His solution to this was to write the ground-breaking work, "Relativity: The Special and General Theory." In the paper, Einstein lays out two contradictory principles: a principle of relativity and a principle of light. Einstein proposed that, rather than discarding these two principles for being conflicting, the rules of time and space should be completely revamped and rethought in order to find a way to make these two principles work in harmony. Rather than just explaining his new proposal, though, Einstein writes exactly why these rules need to be changed by explaining the inaccuracies and inadequacies located within each of the current theories. Albert Einstein is best known for his work on the theory of Relativity, gaining him the title of "Father of Modern Physics." He also received the 1921 Nobel Prize in Physics, and his work is attributed as an inspiration for the quantum theory within the field of physics. After immigrating to America following Adolf Hitler's rise to power in Germany, Einstein famously warned the government that Hitler was planning on creating a weapon based on nuclear fission, and voiced his strong opinion against the creation of the atom bomb. His hundreds of papers and books are highly original and intelligent, making him one of the most famous and respected intellectual minds of the twentieth century.

The present book is intended, as far as possible, to give an exact insight into the theory of Relativity to those readers who, from a general scientific and philosophical point of view, are interested in the theory, but who are not conversant with the mathematical apparatus of theoretical physics. The work presumes a standard of education corresponding to that of a university matriculation examination, and, despite the shortness of the book, a fair amount of patience and force of will on the part of the reader. The author has spared himself no pains in his endeavour to present the main ideas in the simplest and most intelligible form, and on the whole, in the sequence and connection in which they actually originated. In the interest of clearness, it appeared to me inevitable that I should repeat myself frequently, without paying the slightest attention to the elegance of the presentation. I adhered scrupulously to the precept of that brilliant theoretical physicist L. Boltzmann, according to whom matters of elegance ought to be left to the tailor and to the cobbler. I make no pretence of having withheld from the reader difficulties which are inherent to the subject. On the other hand, I have purposely treated the empirical physical foundations of the theory in a "step-motherly" fashion, so that readers unfamiliar with physics may not feel like the wanderer who was unable to see the forest for the trees. May the book bring some one a few happy hours of suggestive thought

General relativity or the general theory of relativity is the geometric theory of gravitation published by Albert Einstein in 1915. It is the current description of gravitation in modern physics. General relativity generalises special relativity and Newton's law of universal gravitation, providing a unified description of gravity as a geometric property of space and time, or spacetime. In particular, the curvature of spacetime is directly related to the four-momentum (mass-energy and linear momentum) of whatever matter and radiation are present. The relation is specified by the Einstein field equations, a system of partial differential equations. Einstein's theory has important astrophysical implications. For example, it implies the existence of black holes-regions of space in which space and time are distorted in such a way that nothing, not even light, can escape-as an end-state for massive stars. There is evidence that such stellar black holes as well as more massive varieties of black hole are responsible for the intense radiation emitted by certain types of astronomical objects such as active galactic nuclei or microquasars.