The history of quantum mechanics is a fundamental part of the history of modern physics. Quantum mechanics' history, as it interlaces with the history of quantum chemistry, began essentially with a number of different scientific discoveries: the 1838 discovery of cathode rays by Michael Faraday; the 1859–60 winter statement of the black-body radiation problem by Gustav Kirchhoff; the 1877 suggestion by Ludwig Boltzmann that the energy states of a physical system could be discrete; the discovery of the photoelectric effect by Heinrich Hertz in 1887; and the 1900 quantum hypothesis by Max Planck that any energy-radiating atomic system can theoretically be divided into a number of discrete "energy elements" ε (Greek letter epsilon) such that each of these energy elements is proportional to the frequency ν with which each of them individually radiate energy, as defined by the following formula:

� = ℎ � ,

Isaac Newton worked on optics throughout his research career, conducting various experiments and developing hypotheses to explain his results.[5] He dismissed Descartes' theory of light because he rejected Descartes’ understanding of space, which derived from it.[6] With the publication of Opticks in 1704, Newton for the first time took a clear position supporting a corpuscular interpretation, though it would fall on his followers to systemise the theory.[7] In the book, Newton argued that the geometric nature of reflection and refraction of light could only be explained if light were made of particles because waves do not tend to travel in straight lines.

Newton's corpuscular theory was an elaboration of his view of reality as interactions of material points through forces. Note Albert Einstein's description of Newton's conception of physical reality:

[Newton's] physical reality is characterised by concepts of space, time, the material point and force (interaction between material points). Physical events are to be thought of as movements according to the law of material points in space. The material point is the only representative of reality in so far as it is subject to change. The concept of the material point is obviously due to observable bodies; one conceived of the material point on the analogy of movable bodies by omitting characteristics of extension, form, spatial locality, and all their 'inner' qualities, retaining only inertia, translation, and the additional concept of force.[8][9]

Every source of light emits large numbers of tiny particles known as corpuscles in a medium surrounding the source. These corpuscles are perfectly elastic, rigid, and weightless.[10]