Editing Newton's laws of motion (section)

=== Inertia and the first law ===
{{See also|Galileo Galilei#Inertia}}
The French philosopher [[René Descartes]] introduced the concept of inertia by way of his "laws of nature" in ''[[The World (book)|The World]]'' (''Traité du monde et de la lumière'') written 1629–33. However, ''The World'' purported a [[Heliocentrism|heliocentric]] worldview, and in 1633 this view had given rise a great conflict between [[Galileo Galilei]] and the [[Roman Inquisition|Roman Catholic Inquisition]]. Descartes knew about this controversy and did not wish to get involved. ''The World'' was not published until 1664, ten years after his death.<ref name=":8">{{Cite journal |last=Blackwell |first=Richard J. |date=1966 |title=Descartes' Laws of Motion |url=https://www.jstor.org/stable/227961 |journal=Isis |volume=57 |issue=2 |pages=220–234|doi=10.1086/350115 |jstor=227961 |s2cid=144278075 }}</ref>
[[File:Galileo.arp.300pix.jpg|alt=Justus Sustermans - Portrait of Galileo Galilei|thumb|184x184px|Galileo Galilei <br/>(1564–1642)]]
 
The modern concept of inertia is credited to Galileo. Based on his experiments, Galileo concluded that the "natural" behavior of a moving body was to keep moving, until something else interfered with it. In ''Two New Sciences'' (1638) Galileo wrote:<ref>{{Cite book |last=Galilei |first=G. |url=http://galileoandeinstein.physics.virginia.edu/tns_draft/tns_244to279.html |title=Dialogues Concerning Two New Sciences |publisher=Dover Publications Inc |year=1954 |editor1=Crew, H. |editor2=De Salvio, A. |pages=268 |orig-date=1638, 1914}}</ref><ref>{{Cite book |last=Galilei |first=G. |url=http://archive.org/details/twonewsciencesin0000gali |title=Two new sciences, including centers of gravity & force of percussion |date=1974 |publisher=University of Wisconsin Press |pages=217 [268] |translator-last=Drake |translator-first=S. |orig-date=1638}}</ref>{{Blockquote|text=Imagine any particle projected along a horizontal plane without friction; then we know, from what has been more fully explained in the preceding pages, that this particle will move along this same plane with a motion which is uniform and perpetual, provided the plane has no limits.}}[[File:Frans_Hals_-_Portret_van_René_Descartes_(cropped)2.jpg|alt=Portrait of René Descartes|thumb|153x153px|René Descartes <br/>(1596–1650)]]Galileo recognized that in projectile motion, the Earth's gravity affects vertical but not horizontal motion.<ref>{{Cite journal |last=Hellman |first=C. Doris |author-link=C. Doris Hellman |date=1955 |title=Science in the Renaissance: A Survey |url=https://www.cambridge.org/core/product/identifier/S0277903X00013281/type/journal_article |journal=[[The Renaissance Society of America|Renaissance News]] |language=en |volume=8 |issue=4 |pages=186–200 |doi=10.2307/2858681 |issn=0277-903X |jstor=2858681}}</ref> However, Galileo's idea of inertia was not exactly the one that would be codified into Newton's first law. Galileo thought that a body moving a long distance inertially would follow the curve of the Earth. This idea was corrected by [[Isaac Beeckman]], Descartes, and [[Pierre Gassendi]], who recognized that inertial motion should be motion in a straight line.<ref>{{Cite book|last=LoLordo|first=Antonia|url=https://www.worldcat.org/oclc/182818133|title=Pierre Gassendi and the Birth of Early Modern Philosophy|date=2007|publisher=Cambridge University Press|isbn=978-0-511-34982-9|location=New York|pages=175–180|oclc=182818133}}</ref> Descartes published his laws of nature (laws of motion) with this correction in ''[[Principles of Philosophy]]'' (''Principia Philosophiae'') in 1644, with the heliocentric part toned down.<ref name=":02">{{Cite book |last=Descartes |first=R. |url=https://www.earlymoderntexts.com/assets/pdfs/descartes1644part2.pdf |title=Principles of philosophy |year=2008 |editor-last=Bennett |editor-first=J. |at=Part II, § 37, 39. |orig-date=1644}}</ref><ref name=":8" />
[[File:Breaking_String.PNG|thumb|Ball in circular motion has string cut and flies off tangentially.]]
{{Blockquote|text=First Law of Nature: Each thing when left to itself continues in the same state; so any moving body goes on moving until something stops it.}}{{Blockquote|text=Second Law of Nature: Each moving thing if left to itself moves in a straight line; so any body moving in a circle always tends to move away from the centre of the circle.}}

According to American philosopher [[Richard J. Blackwell]], Dutch scientist [[Christiaan Huygens]] had worked out his own, concise version of the law in 1656.<ref name=":9">{{Cite journal |last1=Blackwell |first1=Richard J. |last2=Huygens |first2=Christiaan |date=1977 |title=Christiaan Huygens' The Motion of Colliding Bodies |url=https://www.jstor.org/stable/230011 |journal=Isis |volume=68 |issue=4 |pages=574–597|doi=10.1086/351876 |jstor=230011 |s2cid=144406041 }}</ref> It was not published until 1703, eight years after his death, in the opening paragraph of ''De Motu Corporum ex Percussione''.

{{Blockquote|text=Hypothesis I: Any body already in motion will continue to move perpetually with the same speed and in a straight line unless it is impeded.}}

According to Huygens, this law was already known by Galileo and Descartes among others.<ref name=":9" />