Editing Isaac Newton (section)

=== Apple incident ===
{{Main|Isaac Newton's apple tree}}
{{Multiple image|direction=vertical|align=right|image1=Sapling of newton apple tree (cropped).jpg|image2=Newton's tree, Botanic Gardens, Cambridge (sign).jpg|image3=Newtons apple.jpg|width=220|caption3=Reputed descendants of Newton's apple tree at (from top to bottom): [[Trinity College, Cambridge]], the [[Cambridge University Botanic Garden]], and the [[Instituto Balseiro]] library garden in Argentina}}
Newton himself often told the story that he was inspired to formulate his theory of gravitation by watching the fall of an apple from a tree.{{sfn|White|1997|p=86}}{{sfn|Numbers|2015|pp=48–56}} The story is believed to have passed into popular knowledge after being related by [[Catherine Barton]], Newton's niece, to [[Voltaire]].<ref>{{Cite book |last=Malament |first=David B. |url=https://archive.org/details/isbn_9780812695076/page/118 |title=Reading Natural Philosophy: Essays in the History and Philosophy of Science and Mathematics |date=2002 |publisher=Open Court Publishing |isbn=978-0-8126-9507-6 |pages=118–119}}</ref> Voltaire then wrote in his ''Essay on Epic Poetry'' (1727), "Sir Isaac Newton walking in his gardens, had the first thought of his system of gravitation, upon seeing an apple falling from a tree."<ref>{{Cite book |last=Voltaire |url=https://books.google.com/books?id=0o5bAAAAQAAJ&pg=PA104 |title=An Essay upon the Civil Wars of France, extracted from curious Manuscripts and also upon the Epick Poetry of the European Nations, from Homer down to Milton |date=1727 |publisher=Samuel Jallasson |location=London, England |page=104}} From p. 104: 'In the like Manner ''Pythagoras'' ow'd the Invention of Musik to the noise of the Hammer of a Blacksmith. And thus in our Days Sir ''Isaak Newton'' walking in his Garden had the first Thought of his System of Gravitation, upon seeing an apple falling from a Tree.'</ref><ref>Voltaire (1786) heard the story of Newton and the apple tree from Newton's niece, Catherine Conduit (née Barton) (1679–1740): {{Cite book |last=Voltaire |url=https://books.google.com/books?id=NKWTGHiZSm4C&pg=PA175 |title=Oeuvres completes de Voltaire |date=1786 |publisher=Jean-Jacques Tourneisen |volume=31 |location=Basel, Switzerland |page=175 |language=French |trans-title=The complete works of Voltaire |access-date=15 June 2021 |archive-url=https://web.archive.org/web/20210709192112/https://books.google.com/books?id=NKWTGHiZSm4C&pg=PA175 |archive-date=9 July 2021 |url-status=live}} From p. 175: ''"Un jour en l'année 1666, ''Newton'' retiré à la campagne, et voyant tomber des fruits d'un arbre, à ce que m'a conté sa nièce, (Mme ''Conduit'') se laissa aller à une méditation profonde sur la cause qui entraine ainsi tous les corps dans une ligne, qui, si elle était prolongée, passerait à peu près par le centre de la terre."'' (One day in the year 1666 ''Newton'' withdrew to the country, and seeing the fruits of a tree fall, according to what his niece (Madame ''Conduit'') told me, he entered into a deep meditation on the cause that draws all bodies in a [straight] line, which, if it were extended, would pass very near to the center of the Earth.)</ref>

Although it has been said that the apple story is a myth and that he did not arrive at his theory of gravity at any single moment,<ref name="Berkun2010" /> acquaintances of Newton (such as [[William Stukeley]], whose manuscript account of 1752 has been made available by the Royal Society) do in fact confirm the incident, though not the apocryphal version that the apple actually hit Newton's head. Stukeley recorded in his ''Memoirs of Sir Isaac Newton's Life'' a conversation with Newton in Kensington on 15 April 1726:<ref name="Newton's apple: The real story" /><ref name="NP">{{Cite web |title=Revised Memoir of Newton (Normalized Version) |url=http://www.newtonproject.ox.ac.uk/view/texts/normalized/OTHE00001 |url-status=live |archive-url=https://web.archive.org/web/20170314064817/http://www.newtonproject.ox.ac.uk/view/texts/normalized/OTHE00001 |archive-date=14 March 2017 |access-date=13 March 2017 |website=The Newton Project}}</ref>

{{Blockquote|we went into the garden, & drank thea under the shade of some appletrees, only he, & myself. amidst other discourse, he told me, he was just in the same situation, as when formerly, the notion of gravitation came into his mind. "why should that apple always descend perpendicularly to the ground," thought he to him self: occasion'd by the fall of an apple, as he sat in a comtemplative mood: "why should it not go sideways, or upwards? but constantly to the earths centre? assuredly, the reason is, that the earth draws it. there must be a drawing power in matter. & the sum of the drawing power in the matter of the earth must be in the earths center, not in any side of the earth. therefore dos this apple fall perpendicularly, or toward the center. if matter thus draws matter; it must be in proportion of its quantity. therefore the apple draws the earth, as well as the earth draws the apple."<!-- Please do not correct the spelling in this quotation, which is as per the cited source. -->}}

[[John Conduitt]], Newton's assistant at the Royal Mint and husband of Newton's niece, also described the event when he wrote about Newton's life:<ref name="Keynes Ms. 130.4:Conduitt's account of Newton's life at Cambridge" />

{{Blockquote|In the year 1666 he retired again from Cambridge to his mother in Lincolnshire. Whilst he was pensively meandering in a garden it came into his thought that the power of gravity (which brought an apple from a tree to the ground) was not limited to a certain distance from earth, but that this power must extend much further than was usually thought. Why not as high as the Moon said he to himself & if so, that must influence her motion & perhaps retain her in her orbit, whereupon he fell a calculating what would be the effect of that supposition.}}
It is known from his notebooks that Newton was grappling in the late 1660s with the idea that terrestrial gravity extends, in an inverse-square proportion, to the Moon; however, it took him two decades to develop the full-fledged theory.<ref>I. Bernard Cohen and George E. Smith, eds. ''The Cambridge Companion to Newton'' (2002) p. 6</ref> The question was not whether gravity existed, but whether it extended far enough to hold the Moon in orbit. Newton demonstrated that if the force decreased with the inverse square of the distance, one could calculate the Moon's orbital period with good accuracy. He guessed the same force was responsible for other orbital motions, and hence named it "universal gravitation".

Various trees are claimed to be "the" apple tree described by Newton. For one, [[The King's School, Grantham]] claims that the tree was purchased by the school and transplated to the headmaster's garden years later. On the other hand, the staff at [[Woolsthorpe Manor]], now owned by the [[National Trust for Places of Historic Interest or Natural Beauty|National Trust]], contend that the tree in their garden is the true one referenced by Newton. A descendant of the original tree<ref>{{Cite book |last=Mart́ínez |first=Alberto A. |url=https://books.google.com/books?id=BOTTBAAAQBAJ&pg=PA69 |title=Science Secrets: The Truth about Darwin's Finches, Einstein's Wife, and Other Myths |date=2011 |publisher=University of Pittsburgh Press |isbn=978-0-8229-4407-2 |location= |pages=69 |oclc=682895134}}</ref> can be seen growing outside the main gate of Trinity College, Cambridge, below the room Newton lived in when he studied there. The [[National Fruit Collection]] at [[Brogdale]] in Kent<ref name="Brogdale—Home of the National Fruit Collection" /> can supply grafts from their tree, which appears identical to [[Flower of Kent]], a coarse-fleshed cooking variety.<ref name="From the National Fruit Collection: Isaac Newton's Tree" />