Editing Albert Einstein (section)

==== Einstein–de Haas experiment ====
{{Main|Einstein–de Haas effect}}
In 1908, [[Owen Willans Richardson]] predicted that a change in the [[magnetic moment]] of a free body will cause this body to rotate. This effect is a consequence of the [[conservation of angular momentum]] and is strong enough to be observable in [[ferromagnetic materials]].<ref name="Richardson-1908">
{{cite journal
 |last1=Richardson |first1=O. W.
 |year=1908
 |journal=Physical Review
 |title=A Mechanical Effect Accompanying Magnetization
 |url=https://zenodo.org/record/1997325
 |series=Series I
 |volume=26 |issue=3 |pages=248–253
 |bibcode=1908PhRvI..26..248R
 |doi=10.1103/PhysRevSeriesI.26.248
}}</ref> Einstein and [[Wander Johannes de Haas]] published two papers in 1915 claiming the first experimental observation of the effect.<ref name="EdH-1-1915">
{{cite journal
 |last1=Einstein |first1=A.
 |last2=de Haas |first2=W. J.
 |year=1915
 |title=Experimenteller Nachweis der Ampereschen Molekularströme
 |trans-title=Experimental Proof of Ampère's Molecular Currents
 |language=German
 |journal=Deutsche Physikalische Gesellschaft, Verhandlungen
 |volume=17 |pages=152–170
|bibcode=1915DPhyG..17..152E
 }}</ref><ref name="EdH-2-1915">
{{cite journal
 |last1=Einstein |first1=A.
 |last2=de Haas |first2=W. J.
 |year=1915
 |title=Experimental proof of the existence of Ampère's molecular currents
 |journal=Koninklijke Akademie van Wetenschappen te Amsterdam, Proceedings
 |volume=18 |pages=696–711
 |bibcode=1915KNAB...18..696E
 |url=http://www.dwc.knaw.nl/DL/publications/PU00012546.pdf
}}</ref> Measurements of this kind demonstrate that the phenomenon of [[magnetization]] is caused by the alignment ([[Spin polarization|polarization]]) of the [[angular momenta]] of the [[electron]]s in the material along the axis of magnetization. These measurements also allow the separation of the two contributions to the magnetization: that which is associated with the [[Spin (physics)|spin]] and with the orbital motion of the electrons. The Einstein-de Haas experiment is the only experiment concived, realized and published by Albert Einstein himself.

A complete original version of the Einstein-de Haas experimental equipment was donated by [[Geertruida de Haas-Lorentz]], wife of de Haas and daughter of Lorentz, to the [[Ampère Museum]] in Lyon France in 1961 where it is currently on display. It was lost among the museum's holdings and was rediscovered in 2023.<ref>{{Cite journal |last1=San Miguel |first1=Alfonso |last2=Pallandre |first2=Bernard |date=13 March 2024 |title=Revisiting the Einstein-de Haas experiment: the Ampère Museum's hidden treasure |url=https://www.europhysicsnews.org/images/stories/news/epn_Einstein-de_Haas.pdf |journal=Europhysics News |volume=55 |issue=4 |pages=12–14|doi=10.1051/epn/2024409 |bibcode=2024ENews..55...28S }}</ref><ref>{{Cite web |last=Johnston |first=Hamish |date=17 March 2024 |title=Einstein's only experiment is found in French museum |url=https://physicsworld.com/einsteins-only-experiment-is-found-in-french-museum/ |access-date=24 March 2024 |website=Physics World |language=en-GB}}</ref>