Editing Newton's laws of motion (section)

=== Force and the second law ===
[[File:Christiaan Huygens-painting (cropped).jpeg|thumb|Christiaan Huygens <br />(1629–1695)|155x155px]]
Christiaan Huygens, in his ''[[Horologium Oscillatorium]]'' (1673), put forth the hypothesis that "By the action of gravity, whatever its sources, it happens that bodies are moved by a motion composed both of a uniform motion in one direction or another and of a motion downward due to gravity." Newton's second law generalized this hypothesis from gravity to all forces.<ref>{{Cite journal |last=Pourciau |first=Bruce |date=October 2011 |title=Is Newton's second law really Newton's? |url=http://aapt.scitation.org/doi/10.1119/1.3607433 |journal=[[American Journal of Physics]] |language=en |volume=79 |issue=10 |pages=1015–1022 |doi=10.1119/1.3607433 |bibcode=2011AmJPh..79.1015P |issn=0002-9505}}</ref>

One important characteristic of Newtonian physics is that forces can [[action at a distance|act at a distance]] without requiring physical contact.{{refn|group=note|Newton himself was an enthusiastic [[alchemy|alchemist]]. [[John Maynard Keynes]] called him "the last of the magicians" to describe his place in the transition between [[protoscience]] and modern science.<ref>{{Cite journal|last=Fara|first=Patricia|author-link=Patricia Fara|date=2003-08-15|title=Was Newton a Newtonian?|url=https://www.science.org/doi/10.1126/science.1088786|journal=[[Science (journal)|Science]]|language=en|volume=301|issue=5635|pages=920|doi=10.1126/science.1088786|s2cid=170120455 |issn=0036-8075}}</ref><ref>{{Cite book|last=Higgitt|first=Rebekah|url=https://www.worldcat.org/oclc/934741893|title=Science and Culture in the Nineteenth Century: Recreating Newton |date=2015|publisher=Taylor & Francis|isbn=978-1-317-31495-0|location=New York|oclc=934741893 |page=147}}</ref> The suggestion has been made that alchemy inspired Newton's notion of "action at a distance", i.e., one body exerting a force upon another without being in direct contact.<ref>{{cite book|title=The Foundations of Newton's Alchemy: Or, "the Hunting of the Greene Lyon" |first=Betty Jo Teeter |last=Dobbs |author-link=Betty Jo Teeter Dobbs |year=1975 |publisher=Cambridge University Press |isbn=9780521273817 |oclc=1058581988 |pages=211–212}}</ref> This suggestion enjoyed considerable support among historians of science<ref>{{cite book|first=Richard |last=West |title=Never at Rest |year=1980 |publisher=Cambridge University Press |isbn=9780521231435 |oclc=5677169 |page=390}}</ref> until a more extensive study of Newton's papers became possible, after which it fell out of favor. However, it does appear that Newton's alchemy influenced his [[optics]], in particular, how he thought about the combination of colors.<ref name="Newman2016">{{cite book|first=William R. |last=Newman |author-link=William R. Newman |chapter=A preliminary reassessment of Newton's alchemy |title=The Cambridge Companion to Newton |edition=2nd |year=2016 |publisher=Cambridge University Press |isbn=978-1-107-01546-3 |pages=454–484 |oclc=953450997}}</ref><ref>{{Cite journal|last=Nummedal|first=Tara|author-link=Tara Nummedal|date=2020-06-01|title=William R. Newman. Newton the Alchemist: Science, Enigma, and the Quest for Nature's "Secret Fire"|url=https://www.journals.uchicago.edu/doi/10.1086/709344|journal=[[Isis (journal)|Isis]]|language=en|volume=111|issue=2|pages=395–396|doi=10.1086/709344|s2cid=243203703 |issn=0021-1753}}</ref>}} For example, the Sun and the Earth pull on each other gravitationally, despite being separated by millions of kilometres. This contrasts with the idea, championed by Descartes among others, that the Sun's gravity held planets in orbit by swirling them in a vortex of transparent matter, ''[[Aether theories|aether]]''.<ref>{{Cite book |last=Aldersey-Williams |first=Hugh |url=https://www.worldcat.org/oclc/1144105192 |title=Dutch Light: Christiaan Huygens and the Making of Science in Europe |date=2020 |publisher=Picador |isbn=978-1-5098-9333-1 |location=London |oclc=1144105192}}</ref> Newton considered aetherial explanations of force but ultimately rejected them.<ref name="Newman2016"/> The study of magnetism by [[William Gilbert (physician)|William Gilbert]] and others created a precedent for thinking of ''immaterial'' forces,<ref name="Newman2016" /> and unable to find a quantitatively satisfactory explanation of his law of gravity in terms of an aetherial model, Newton eventually declared, "[[Hypotheses non fingo|I feign no hypotheses]]": whether or not a model like Descartes's vortices could be found to underlie the ''Principia''<nowiki/>'s theories of motion and gravity, the first grounds for judging them must be the successful predictions they made.<ref>{{Cite journal |last=Cohen |first=I. Bernard |author-link=I. Bernard Cohen |date=1962 |title=The First English Version of Newton's Hypotheses non fingo |url=https://www.jstor.org/stable/227788 |journal=[[Isis (journal)|Isis]] |volume=53 |issue=3 |pages=379–388 |doi=10.1086/349598 |jstor=227788 |s2cid=144575106 |issn=0021-1753}}</ref> And indeed, since Newton's time [[Mechanical explanations of gravitation|every attempt at such a model has failed]].