Einstein was born in Germany in 1879. His mother died when he was five years old and his father, a professor of physics, took him to Zurich to live with his brother Eduard. Einstein was fascinated by the work of Faraday and Maxwell, and the work of Maxwell’s assistant, James Clerk Maxwell. He was also fascinated by the work of Heinrich Hertz, who had proved that light was a form of electromagnetic radiation.
In 1905, Einstein published a paper in which he showed that Maxwell’s equations could be derived from a set of four postulates, including the principle of relativity. Einstein’s theory was in complete agreement with the experimental results of Heinrich Hertz, who had shown that the speed of light was the same in all directions and that the speed of light in a vacuum was the same as the speed of light in a medium.
Einstein’s theory was also in complete agreement with the results of Heinrich Hertz’s assistant, Philipp Lenard, who had shown that the energy of light was equal to the product of the frequency of the light and the speed of light.
Einstein’s theory was also in complete agreement with the experimental results of Max Planck, who had shown that the energy of a single photon of light, or of any other kind of light, is quantized and equal to the product of the frequency of the light and the value of h, Planck’s constant.
So, by 1905, Einstein had shown that Maxwell’s equations and three of the four postulates of his theory of special relativity could be derived from a set of four postulates, all of which were in agreement with the experimental results of Heinrich Hertz, Philipp Lenard, and Max Planck.
Einstein’s theory of special relativity is often abbreviated to “the theory of relativity” and this is the form in which it is best known. This is because the theory has many experimental consequences, and this was the first time that this had been possible for any theory of physics.
He later extended this to a theory of general relativity, the generalization of the theory of relativity. Although the theory of general relativity is a much more complex theory than that of special relativity, Einstein made significant progress on it during the First World War, and also from 1927.
Einstein’s work on the theory of relativity had led to important technological and practical consequences. For example, it has been important for the development of electronics, telecommunications, and the global positioning system (GPS).