User:Johnjbarton/sandbox/introduction to quantum mechanics: Difference between revisions

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In 1922 [[Otto Stern]] and [[Walther Gerlach]] [[Stern-Gerlach experiment |demonstrated]] that the magnetic properties of silver atoms do not take a continuous range of values: the magnetic values are quantized and limited to only two possibilities.<ref name="cigar">{{Cite journal |last=Friedrich |first=Bretislav |last2=Herschbach |first2=Dudley |date=December 2003 |title=Stern and Gerlach: How a Bad Cigar Helped Reorient Atomic Physics |url=http://physicstoday.scitation.org/doi/10.1063/1.1650229 |journal=Physics Today |language=en |volume=56 |issue=12 |pages=53–59 |doi=10.1063/1.1650229 |issn=0031-9228}}</ref> Unlike the other then known quantum effects, this striking result involves the state of a single atom.<ref name=Whittaker/>{{rp|v2:130}}

In 1924 [[Louis de Broglie]] proposed<ref name=Broglie>{{cite web |last1=de Broglie |first1=Louis Victor |title=On the Theory of Quanta |url=https://fondationlouisdebroglie.org/LDB-oeuvres/De_Broglie_Kracklauer.pdf |access-date=25 February 2023 |website=Foundation of Louis de Broglie |edition=English translation by A.F. Kracklauer, 2004.}}</ref> that electrons in an atom are constrained not in "orbits" but as standing waves. In detail his solution did not work, but his hypothesis – that the electron "corpuscle" moves in the atom as a wave – spurred [[Edwin Schrodinger]] to develop a [[Schrodinger equation | wave equation]] for electrons; when applied to hydrogen the Rydberg formula was accurately reproduced.<ref In 1928 [[Paul Dirac]] published his [[Dirac equation name=baggott/>{{rp| relativistic wave equation]] simultaneously incorporating [[Theory of relativity| relativity]], predicting [[anti-matter]], and providing a complete theory for the Stern-Gerlach result (that there are only two directions that can be measured for silver atoms and for electrons themselves) . These successes launched a new fundamental understanding of our world at small scale: quantum mechanics.65}}

[[Max Born]]'s 1924 paper ''"Zur Quantenmechanik"'' was the first use of the words "quantum mechanics" in print.<ref>Max Born, ''My Life: Recollections of a Nobel Laureate'', Taylor & Francis, London, 1978. ("We became more and more convinced that a radical change of the foundations of physics was necessary, i.e., a new kind of mechanics for which we used the term quantum mechanics. This word appears for the first time in physical literature in a paper of mine...")</ref><ref>{{Cite journal |last=Fedak |first=William A. |last2=Prentis |first2=Jeffrey J. |date=2009-02-01 |title=The 1925 Born and Jordan paper “On quantum mechanics” |url=https://people.isy.liu.se/icg/jalar/kurser/QF/references/onBornJordan1925.pdf |journal=American Journal of Physics |language=en |volume=77 |issue=2 |pages=128–139 |doi=10.1119/1.3009634 |issn=0002-9505}}</ref> His later work included developing quantum collision models; in a footnote to a 1926 paper he proposed the [[Born rule]] connecting theoretical models to experiment.<ref name=Zeitschrift>

{{cite book

|last=Born

|first=Max

|author-link=Max Born

|editor1-last=Wheeler

|editor1-first=J. A.

|editor1-link=John Archibald Wheeler

|editor2-last=Zurek

|editor2-first=W. H.

|editor2-link=Wojciech H. Zurek

|title=Zur Quantenmechanik der Stoßvorgänge

|journal=Zeitschrift für Physik

|volume=37

|issue=12

|trans-title=On the quantum mechanics of collisions

|date=1926

|publisher=Princeton University Press

|publication-date=1983

|doi=10.1007/BF01397477

|isbn=978-0-691-08316-2

|section=I.2

|pages=863–867

|bibcode = 1926ZPhy...37..863B |s2cid=119896026

}}

</ref>

In 1928 [[Paul Dirac]] published his [[Dirac equation | relativistic wave equation]] simultaneously incorporating [[Theory of relativity| relativity]], predicting [[anti-matter]], and providing a complete theory for the Stern-Gerlach result (that there are only two directions that can be measured for silver atoms and for electrons themselves).<ref name=baggott/>{{rp|131}} These successes launched a new fundamental understanding of our world at small scale: quantum mechanics.

Planck and Einstein started the revolution with quanta that broke down the continuous models of matter and light. Twenty years later "corpuscles" like electrons came to be modeled as continuous waves. This result came to be called wave-particle duality, one iconic idea along with the uncertainty principle that sets quantum mechanics apart from older models of physics.