Google’s Doodle is honouring Max Born, the German physicist and mathematician who discovered one of the most important rules in quantum mechanics, on his 135th birthday on Monday.He is famous for the Born Rule, a theory that uses probability to predict the location of a particle in a quantum system, says Forbes. That’s important for understanding and using quantum mechanics, the principles that govern physics at subatomic scales. Physicists assumed, before Born helped them out, that if you wanted to know the location of a quantum particle, you had to measure it exactly using a series of physical experiments and calculation. Born said that all you really needed was a matrix (a group of numbers lined up in columns and rows) and the rules of probability.Born rule provides a link between the mathematical formalism of quantum theory and experiment, and as such is almost single-handedly responsible for practically all predictions of quantum physics, according to N P Landsman, Institute for Mathematics, Astrophysics, and Particle Physics, Radboud University Nijmegen, according to an article on The Hindu.Born, along with fellow German scientist Fritz Haber, formulated the Born–Haber cycle, that calculates lattice energy or the energy needed to form a crystal from infinitely-separated ions. His other notable works include Born–Oppenheimer approximation, the assumption that the motion of atomic nuclei and electrons in a molecule can be separated, and Born-von Karman boundary condition which imposes the restriction that a wave function must be periodic on a certain Bravais lattice.Born won the 1954 Nobel Prize in Physics for his work on quantum mechanics. During the Nazi rule, Born was rendered stateless since he was a Jew. He was forced to flee Germany for England, where he served as the Tait Professor of Natural Philosophy at the University of Edinburgh for nearly two decades until his retirement in 1954 when he returned home to Göttingen.