Quantum#Quantization in antiquity

{{Short description|Minimum amount of a physical entity involved in an interaction}}

In physics, a quantum ({{plural form}}: quanta) is the minimum amount of any physical entity (physical property) involved in an interaction. The fundamental notion that a property can be "quantized" is referred to as "the hypothesis of quantization".Wiener, N. (1966). Differential Space, Quantum Systems, and Prediction. Cambridge, Massachusetts: The Massachusetts Institute of Technology Press This means that the magnitude of the physical property can take on only discrete values consisting of integer multiples of one quantum. For example, a photon is a single quantum of light of a specific frequency (or of any other form of electromagnetic radiation). Similarly, the energy of an electron bound within an atom is quantized and can exist only in certain discrete values.{{Cite book |last=Rovelli |first=Carlo |title=Reality is not what it seems: the elementary structure of things |date=January 2017 |publisher=Riverhead Books |isbn=978-0-7352-1392-0 |edition=1st American |location=New York, New York |pages=109–130 |translator-last=Carnell |translator-first=Simon |translator-last2=Segre |translator-first2=Erica}} Atoms and matter in general are stable because electrons can exist only at discrete energy levels within an atom. Quantization is one of the foundations of the much broader physics of quantum mechanics. Quantization of energy and its influence on how energy and matter interact (quantum electrodynamics) is part of the fundamental framework for understanding and describing nature.

Origin

File:Max Planck (1858-1947).jpg and 1918 Nobel Prize for Physics recipient Max Planck (1858–1947)]]

The modern concept of the quantum in physics originates from December 14, 1900, when Max Planck reported his findings to the German Physical Society. He showed that modelling harmonic oscillators with discrete energy levels resolved a longstanding problem in the theory of blackbody radiation.{{Cite book |last=Baggott |first=J. E. |title=The quantum story: a history in 40 moments |date=2013 |publisher=Oxford University Press |isbn=978-0-19-965597-7 |edition=Pbk |location=Oxford [England]}}{{rp|15}}{{cite journal |last = Planck |first = M. |author-link = Max Planck |year = 1901 |title = Ueber die Elementarquanta der Materie und der Elektricität |journal = Annalen der Physik |volume = 309 |pages = 564–566 |doi = 10.1002/andp.19013090311 |bibcode = 1901AnP...309..564P |issue = 3 |language = de |url = https://zenodo.org/record/1423997 |via=Zenodo |access-date = 2019-09-16 |archive-date = 2023-06-24 |archive-url = https://web.archive.org/web/20230624230014/https://zenodo.org/record/1423997 |url-status = live }} In his report, Planck did not use the term quantum in the modern sense. Instead, he used the term {{Lang|de|Elementarquantum}} to refer to the "quantum of electricity", now known as the elementary charge. For the smallest unit of energy, he employed the term {{Lang|de|Energieelement}}, "energy element", rather than calling it a quantum.{{Oed|term=Quantum|id=1164299139|access-date=6 May 2025|date=2007}}

Shortly afterwards, in a paper published in Annalen der Physik,{{citation |last=Planck |first=Max |title=Ueber das Gesetz der Energieverteilung im Normalspectrum |journal=Annalen der Physik |volume=309 |issue=3 |pages=553–63 |year=1901 |url=http://www.physik.uni-augsburg.de/annalen/history/historic-papers/1901_309_553-563.pdf |access-date=2008-12-15 |archive-url=https://web.archive.org/web/20120610124128/http://www.physik.uni-augsburg.de/annalen/history/historic-papers/1901_309_553-563.pdf |archive-date=2012-06-10 |url-status=live |language=de |bibcode=1901AnP...309..553P |doi=10.1002/andp.19013090310 |author-link=Max Planck |doi-access=free}}. English translations:

{{Cite web |title=On the Law of Distribution of Energy in the Normal Spectrum |url=http://dbhs.wvusd.k12.ca.us/webdocs/Chem-History/Planck-1901/Planck-1901.html |url-status=dead |archive-url=https://web.archive.org/web/20080418002757/http://dbhs.wvusd.k12.ca.us/webdocs/Chem-History/Planck-1901/Planck-1901.html |archive-date=2008-04-18}}
{{cite web |title=On the Law of Distribution of Energy in the Normal Spectrum |url=http://theochem.kuchem.kyoto-u.ac.jp/Ando/planck1901.pdf |url-status=dead |archive-url=https://web.archive.org/web/20111006162543/http://theochem.kuchem.kyoto-u.ac.jp/Ando/planck1901.pdf |archive-date=2011-10-06 |access-date=2011-10-13}} Planck introduced the constant h, which he termed the "quantum of action" ({{Lang|de|elementares Wirkungsquantum}}) in 1906. In this paper, Planck also reported more precise values for the elementary charge and the Avogadro–Loschmidt number, the number of molecules in one mole of substance.{{cite journal |last1=Klein |first1=Martin J. |year=1961 |title=Max Planck and the beginnings of the quantum theory |journal=Archive for History of Exact Sciences |volume=1 |issue=5 |pages=459–479 |doi=10.1007/BF00327765 |s2cid=121189755}} The constant h is now known as the Planck constant. After his theory was validated, Planck was awarded the Nobel Prize in Physics for his discovery in 1918.{{Cite web |title=Max Planck Nobel Lecture |url=https://www.nobelprize.org/prizes/physics/1918/planck/lecture/ |url-status=live |archive-url=https://web.archive.org/web/20230714164215/https://www.nobelprize.org/prizes/physics/1918/planck/lecture/ |archive-date=2023-07-14 |access-date=2023-07-14}}

In 1905 Albert Einstein suggested that electromagnetic radiation exists in spatially localized packets which he called "quanta of light" (Lichtquanta).{{cite journal |last = Einstein |first = A. |author-link = Albert Einstein |year = 1905 |title = Über einen die Erzeugung und Verwandlung des Lichtes betreffenden heuristischen Gesichtspunkt |url = http://www.physik.uni-augsburg.de/annalen/history/einstein-papers/1905_17_132-148.pdf |journal = Annalen der Physik |volume = 17 |pages = 132–148 |doi = 10.1002/andp.19053220607 |bibcode = 1905AnP...322..132E |issue = 6 |language = de |doi-access = free |access-date = 2010-08-26 |archive-date = 2015-09-24 |archive-url = https://web.archive.org/web/20150924072915/http://www.physik.uni-augsburg.de/annalen/history/einstein-papers/1905_17_132-148.pdf |url-status = live }}. A partial [https://en.wikisource.org/?curid=59468 English translation] {{Webarchive |url=https://web.archive.org/web/20210121022128/https://en.wikisource.org/?curid=59468 |date=2021-01-21 }} is available from Wikisource.

Einstein was able to use this hypothesis to recast Planck's treatment of the blackbody problem in a form that also explained the voltages observed in Philipp Lenard's experiments on the photoelectric effect.{{rp|23}} Shortly thereafter, the term "energy quantum" was introduced for the quantity Planck relation.{{Cite book |last=Kuhn |first=Thomas S. |url=https://archive.org/details/blackbodytheoryq0000kuhn/mode/1up |title=Black-body theory and the quantum discontinuity, 1894-1912 |date=1978 |publisher=Clarendon Press |others= |isbn=978-0-19-502383-1 |location=Oxford |pages=201}}

Quantization

While quantization was first discovered in electromagnetic radiation, it describes a fundamental aspect of energy not just restricted to photons.{{Cite web |last=Parker |first=Will |date=2005-02-11 |title=Real-World Quantum Effects Demonstrated |url=http://www.scienceagogo.com/news/20050110221715data_trunc_sys.shtml |access-date=2023-08-20 |website=ScienceAGoGo |language=en-US}}

In the attempt to bring theory into agreement with experiment, Max Planck postulated that electromagnetic energy is absorbed or emitted in discrete packets, or quanta.Modern Applied Physics-Tippens third edition; McGraw-Hill.

Quantum#Quantization in antiquity

Origin

Quantization

See also

References

Further reading