Einstein's theory of general relativity unites his theory of special relativity with the concept of gravity conceived of by Sir Isaac Newton. Einstein's key insight was that gravitation is not the result of a force. It is rather a manifestation of curved space and time. Einstein's theory of general relativity can be understood by considering the following scenario. An astronaut sitting in a space capsule waiting to launch at Cape Canaveral feels his normal weight. While in space, free from gravitational pull, the astronaut feels weightless. However, if the space capsule were to accelerate upwards in space at exactly the acceleration of gravity back on earth, the astronaut would be pushed into his seat with a force exactly equivalent to his own weight. The astronaut would be unable to distinguish between the sensation of sitting in the space capsule prior to launch in Cape Canaveral, and the sensation of sitting in the space capsule as it accelerates upwards in space at exactly the acceleration of gravity. He could only distinguish between the two by looking out the window.
Einstein is perhaps most well-known by the public for his Theory of Relativity. In his introduction of Einstein at the Medal Day ceremony, Dr. Frederick Palmer, Jr. alluded to Einstein's popularity with the following remarks:
"Through more than a hundred scientific papers characterized by keen analysis and brilliant imagination, Doctor Einstein has exerted a profound and lasting influence upon the scientific thought of the world. The romance of his achievement has been such that mathematical physics has become popular with the public."
You can read the full text of Palmer's introductory speech by clicking on the thumbnail at right.