Einstein+had+a+rather+large+idea+I+presume.

Einstein's big ol' idea was relativity and its own theories. Basically it is the idea of the space-time fabric relative to everyone in uniform motion. The laws of physics are the same for everyone. The speed of light in a vacuum is the same to any observer. It also encompasses the theory of gravitation. This in turn led to Einstein's idea of time travel through the mathematical possibility of wormholes. This all being based off the existence of black holes.