Special Section: the Legacy of Albert Einstein

Unification of the theory of gravitation, as given by Einstein’s general theory of relativity, and the theory of electromagnetism, as formulated by Maxwell, had been Einstein’s dream during the later part of his life. String theory, which is the subject of this article, is an attempt to realize this dream. However in many ways string theory attempts to go beyond Einstein’s dream. String theory attempts to bring all known forces of nature – not just gravity and electromagnetism – under one umbrella. It also tries to do so in a manner that is consistent with the principles of quantum mechanics – the theory that is necessary for describing the laws of nature at very small distance. Thus string theory is an attempt to provide an all-encompassing description of nature that works at large distances where gravity becomes important as well as small distances where quantum mechanics is important.