At the patent office, Albert Einstein evaluated patent applications for electromagnetic devices. He quickly mastered the job, leaving him time to ponder on the transmission of electrical signals and electrical-mechanical synchronization, an interest he had been cultivating for several years. While at the polytechnic school he had studied Scottish physicist James Maxwell's electromagnetic theories which describe the nature of light, and discovered a fact unknown to Maxwell himself, that the speed of light remained constant. However, this violated Isaac Newton's laws of motion because there is no absolute velocity in Newton's theory. This insight led Einstein to formulate the principle of relativity.