And his third great work for 1905 was his Special Theory of Relativity. His Special Theory of Relativity dealt with the very small microscopic world. It dealt with electric and magnetic phenomena. This was pretty amazing stuff, and in 1916, he followed up with his General Theory of Relativity. His General Theory of Relativity was really a Theory of Gravitation.
Gravity is a strange force.
It is the weakest of all the four forces that we know of, and yet it reaches all the way to the edge of the Universe. His General Theory of Relativity made quite a few predictions. In the three-quarters of a century since his General Theory of Relativity was published, it has passed every single test that has been put to it. His General Theory of Relativity successfully explained the odd orbit of Mercury. It indirectly explained why, after the Big Bang, the Universe would have cooled down to its current temperature.