While the roots of quantum mechanics can be traced to experiments performed in the 19th century, the theory began to emerge when [[Max Planck]] proposed a "quantum hypothesis" to explain the energy spectrum of [[black body]] radiation in 1900. In 1905, [[Albert Einstein]] suggested that light is composed of discrete packets (''quanta'') in order to explain the [[photoelectric effect]]. A decade later, [[
Neils Bohr]] proposed a model of the atom in which [[angular momentum is quantized]]. Eventually, the mathematical formalism that became known as quantum mechanics was developed in the 1920s and 1930s, with [[Erwin Schrodinger]]'s discovery of wave mechanics and [[Werner Heisenberg]]'s discovery of matrix mechanics.
==The uncertainty principle==