Editing Magnetism (section)

== History ==
{{main|History of electromagnetic theory}}
{{More citations needed section|reason=history requires secondary sources to avoid being original research|date=October 2024}}
[[File:Lodestone attracting nails.png|thumb|upright|[[Lodestone]], a natural [[magnet]], attracting iron nails. Ancient humans discovered the property of magnetism from lodestone.]]
[[File:Blacksmith at the anvil. Wellcome L0005875.jpg|thumb|An illustration from Gilbert's 1600 ''De Magnete'' showing one of the earliest methods of making a magnet. A blacksmith holds a piece of red-hot iron in a north–south direction and hammers it as it cools. The magnetic field of the Earth aligns the domains, leaving the iron a weak magnet.]]
[[File:A man is violently rubbed with magnets. Coloured lithograph Wellcome V0011767.jpg|thumb|upright|Drawing of a medical treatment using magnetic brushes. [[Charles Jacque]] 1843, France.]]
Magnetism was first discovered in the ancient world when people noticed that [[lodestone]]s, naturally magnetized pieces of the mineral [[magnetite]], could attract iron.<ref name="Tremolet">{{cite book | last = Du Trémolet de Lacheisserie | first = Étienne |author2=Damien Gignoux |author3=Michel Schlenker  | title = Magnetism: Fundamentals | publisher = Springer | year = 2005 | pages = 3–6 | url = https://books.google.com/books?id=MgCExarQD08C&pg=PA3 | isbn = 978-0-387-22967-6}}</ref> The word ''magnet'' comes from the [[Ancient Greek|Greek]] term μαγνῆτις λίθος ''magnētis lithos'',<ref>[https://archive.org/details/bub_gb_BkS2KW7u76MC ''Platonis Opera''], Meyer and Zeller, 1839, p. 989.</ref> "the Magnesian stone, lodestone".<ref>The location of Magnesia is debated; it could be [[Magnesia (regional unit)|the region in mainland Greece]] or [[Magnesia ad Sipylum]]. See, for example, {{cite web|url=http://www.languagehat.com/archives/001914.php |title=Magnet |work=Language Hat blog |date=28 May 2005 |access-date = 22 March 2013}}</ref> In ancient Greece, [[Aristotle]] attributed the first of what could be called a scientific discussion of magnetism to the philosopher [[Thales]] of [[Miletus]], who lived from about 625&nbsp;BCE to about 545&nbsp;BCE.<ref>{{cite web |url= http://galileoandeinstein.physics.virginia.edu/more_stuff/E&M_Hist.html|title= Historical Beginnings of Theories of Electricity and Magnetism|access-date=2008-04-02 |last= Fowler|first= Michael|year= 1997}}</ref> The [[History of India|ancient Indian]] medical text ''[[Sushruta Samhita]]'' describes using magnetite to remove arrows embedded in a person's body.<ref>{{Cite book|title=Nanomaterials and Nanocomposites: Synthesis, Properties, Characterization Techniques, and Applications|page=171|year=2017|publisher=CRC Press|first1=Rajendra|last1=Kumar Goyal|isbn=9781498761673}}</ref>

<!-- The following is partly identical to [[Lodestone#History]] -->
In [[History of China#Ancient China|ancient China]], the earliest literary reference to magnetism lies in a 4th-century BCE book named after its author, ''[[Guiguzi]]''.<ref>The section "Fanying 2" ([[:s:鬼谷子|反應第二]]) of ''The [[Guiguzi]]'': "{{lang|zh|其察言也，不失若磁石之取鍼，舌之取燔骨}}".</ref>
The 2nd-century BCE annals, ''[[Lüshi Chunqiu]]'', also notes:
"The [[lodestone]] makes iron approach; some (force) is attracting it."<ref name=Li54>{{cite journal |last=Li |first=Shu-hua |title=Origine de la Boussole II. Aimant et Boussole |journal=Isis |volume=45 |number=2 |year=1954 |pages=175–196|jstor=227361|doi=10.1086/348315|s2cid=143585290 | quote = un passage dans le ''[[Lüshi Chunqiu|Liu-che-tch'ouen-ts'ieou]]'' [...]: "La pierre d'aimant fait venir le fer ou elle l'attire." | language = fr}}<br /> From the section "''Jingtong''" ({{lang|zh|精通}}) of the "Almanac of the Last Autumn Month" ({{lang|zh|季秋紀}}): "{{lang|zh|慈石召鐵，或引之也}}]"</ref> 
The earliest mention of the attraction of a needle is in a 1st-century work ''[[Lunheng]]'' (''Balanced Inquiries''): "A lodestone attracts a needle."<ref>In the section "[https://archive.org/stream/lunheng02wang#page/350/mode/1up A Last Word on Dragons]" ({{lang|zh|亂龍篇}} ''Luanlong'') of the ''[[Lunheng]]'': "[[Amber]] takes up straws, and a load-stone attracts needles" ({{lang|zh|頓牟掇芥，磁石引針}}).</ref> 
The 11th-century [[History of science and technology in China|Chinese scientist]] [[Shen Kuo]] was the first person to write—in the ''[[Dream Pool Essays]]''—of the magnetic needle compass and that it improved the accuracy of navigation by employing the [[astronomical]] concept of [[true north]].
By the 12th century, the Chinese were known to use the lodestone [[compass#China|compass]] for navigation. They sculpted a directional spoon from lodestone in such a way that the handle of the spoon always pointed south.

[[Alexander Neckam]], by 1187, was the first in Europe to describe the compass and its use for navigation. In 1269, [[Peter of Maricourt|Peter Peregrinus de Maricourt]] wrote the ''Epistola de magnete'', the first extant treatise describing the properties of magnets. In 1282, the properties of magnets and the dry compasses were discussed by [[Al-Ashraf Umar II]], a [[Islamic physics|Yemeni physicist]], [[Islamic astronomy|astronomer]], and [[Islamic geography|geographer]].<ref>{{Cite journal|title=Two Early Arabic Sources On The Magnetic Compass|first=Petra G.|last=Schmidl|journal=Journal of Arabic and Islamic Studies|year=1996–1997|volume=1|pages=81–132}}</ref>

[[Leonardo Garzoni]]'s only extant work, the ''Due trattati sopra la natura, e le qualità della calamita'' (''Two treatises on the nature and qualities of the magnet''), is the first known example of a modern treatment of magnetic phenomena. Written in years near 1580 and never published, the treatise had a wide diffusion. In particular, Garzoni is referred to as an expert in magnetism by Niccolò Cabeo, whose Philosophia Magnetica (1629) is just a re-adjustment of Garzoni's work. Garzoni's treatise was known also to [[Giovanni Battista Della Porta]].

In 1600, [[William Gilbert (astronomer)|William Gilbert]] published his ''[[De Magnete|De Magnete, Magneticisque Corporibus, et de Magno Magnete Tellure]]'' (''On the Magnet and Magnetic Bodies, and on the Great Magnet the Earth''). In this work he describes many of his experiments with his model earth called the [[terrella]]. From his experiments, he concluded that the [[Earth's magnetic field|Earth]] was itself magnetic and that this was the reason compasses pointed north whereas, previously, some believed that it was the pole star [[Polaris]] or a large magnetic island on the north pole that attracted the compass.

An understanding of the relationship between [[electricity]] and magnetism began in 1819 with work by [[Hans Christian Ørsted]], a professor at the University of Copenhagen, who discovered, by the accidental twitching of a compass needle near a wire, that an electric current could create a magnetic field. This landmark experiment is known as Ørsted's Experiment. [[Jean-Baptiste Biot]] and [[Félix Savart]], both of whom in 1820 came up with the [[Biot–Savart law]] giving an equation for the magnetic field from a current-carrying wire. Around the same time, [[André-Marie Ampère]] carried out numerous systematic experiments and discovered that the magnetic force between two DC current loops of any shape is equal to the sum of the individual forces that each current element of one circuit exerts on each other current element of the other circuit.

In 1831, [[Michael Faraday]] discovered that a time-varying magnetic flux induces a voltage through a wire loop. In 1835, [[Carl Friedrich Gauss]] hypothesized, based on [[Ampère's force law]] in its original form, that all forms of magnetism arise as a result of elementary point charges moving relative to each other.<ref name="Gauss1835"></ref> [[Wilhelm Eduard Weber]] advanced Gauss's theory to [[Weber electrodynamics]]. 

From around 1861, [[James Clerk Maxwell]] synthesized and expanded many of these insights into [[Maxwell's equations]], unifying electricity, magnetism, and [[optics]] into the field of [[electromagnetism]]. However, Gauss's interpretation of magnetism is not fully compatible with Maxwell's electrodynamics. In 1905, [[Albert Einstein]] used Maxwell's equations in motivating his theory of [[special relativity]],<ref name="Moving">[http://www.fourmilab.ch/etexts/einstein/specrel/www/ A. Einstein: "On the Electrodynamics of Moving Bodies"], June 30, 1905.</ref> requiring that the laws held true in all [[inertial reference frame]]s. Gauss's approach of interpreting the magnetic force as a mere effect of relative velocities thus found its way back into electrodynamics to some extent.

Electromagnetism has continued to develop into the 21st century, being incorporated into the more fundamental theories of [[gauge theory]], [[quantum electrodynamics]], [[electroweak theory]], and finally the [[standard model]].