Editing Quantization (physics) (section)

== Historical overview == 
In 1901, when [[Max Planck]] was developing the [[distribution function (physics)|distribution function]] of [[statistical mechanics]] to solve the [[ultraviolet catastrophe]] problem, he realized that the properties of [[blackbody radiation]] can be explained by the assumption that the amount of energy must be in countable fundamental units, i.e. amount of energy is not continuous but [[quantum|discrete]]. That is, a minimum unit of energy exists and the following relationship holds  <math>E = h \nu</math>
for the frequency  <math>\nu</math>. Here,  <math>h</math> is called the [[Planck constant]], which represents the amount of the quantum mechanical effect. It means a fundamental change of mathematical model of physical quantities.

In 1905, [[Albert Einstein]] published a paper, "On a heuristic viewpoint concerning the emission and transformation of light", which explained the [[photoelectric effect]] on quantized [[electromagnetic wave|electromagnetic waves]].<ref>{{citation|first=Albrecht|last=Folsing|title=Albert Einstein: A Biography |publisher=trans. Ewald Osers, Viking|year=1997}}</ref> The ''energy quantum'' referred to in this paper was later called "[[photon]]".  In July 1913, [[Niels Bohr]] used quantization to describe the spectrum of a hydrogen atom in his paper "On the constitution of atoms and molecules". 

The preceding theories have been successful, but they are very phenomenological theories.  However, the French mathematician [[Henri Poincaré]] first gave a systematic and rigorous definition of what quantization is in his 1912 paper "Sur la théorie des quanta".<ref>
{{cite journal
 |last=McCormmach |first=Russell
 |title=Henri Poincaré and the Quantum Theory |journal=Isis |volume=58 |issue=1 |pages=37–55 |date=Spring 1967
 |doi=10.1086/350182 |s2cid=120934561
}}</ref><ref>{{cite journal|last=Irons|first=F.E.|title=Poincaré's 1911–12 proof of quantum discontinuity interpreted as applying to atoms|journal=American Journal of Physics|volume=69|issue=8|pages=879–84|date=August 2001|doi=10.1119/1.1356056|bibcode=2001AmJPh..69..879I }}</ref> 

The term "quantum physics" was first used in Johnston's ''Planck's Universe in Light of Modern Physics''.  (1931).