Robert Anson Heinlein (July 7, 1907 – May 8, 1988) was an American novelist an science fiction writer. Often called "the dean of science fiction writers", he is one of the most popular, influential, and controversial authors of "hard science fiction". He set a high standard for science and engineering plausibility and helped to raise the genre's standards of literary quality. He was the first writer to break into mainstream, general magazines such as The Saturday Evening Post, in the late 1940s, with unvarnished science fiction. He was among the first authors of bestselling, novel-length science fiction in the modern, mass-market era. For many years, Heinlein, Isaac Asimov, and Arthur C. Clarke were known as the "Big Three" of science fiction.