Editing Gravity (section)

===Scientific revolution===
{{main|Scientific Revolution}}
In the mid-16th century, various European scientists experimentally disproved the [[Aristotelian physics|Aristotelian]] notion that heavier objects [[Free fall|fall]] at a faster rate.<ref name="Wallace-2018">{{Cite book|last=Wallace|first=William A.|url=https://books.google.com/books?id=8GxQDwAAQBAJ&pg=PR21|title=Domingo de Soto and the Early Galileo: Essays on Intellectual History|publisher=[[Routledge]]|year=2018|isbn=978-1-351-15959-3|location=Abingdon, UK|pages=119, 121–22|language=en|orig-year=2004|access-date=4 August 2021|archive-date=16 June 2021|archive-url=https://web.archive.org/web/20210616043300/https://books.google.com/books?id=8GxQDwAAQBAJ&pg=PR21|url-status=live}}</ref> In particular, the [[Spanish people|Spanish]] Dominican priest [[Domingo de Soto]] wrote in 1551 that bodies in [[free fall]] uniformly accelerate.<ref name="Wallace-2018"/> De Soto may have been influenced by earlier experiments conducted by other [[Dominican Order|Dominican]] priests in Italy, including those by [[Benedetto Varchi]], Francesco Beato, [[Luca Ghini]], and [[Giovan Battista Bellaso|Giovan Bellaso]] which contradicted Aristotle's teachings on the fall of bodies.<ref name="Wallace-2018"/>

The mid-16th century Italian physicist [[Giambattista Benedetti]] published papers claiming that, due to [[relative density|specific gravity]], objects made of the same material but with different masses would fall at the same speed.<ref name="Drabkin">{{Cite journal| doi = 10.1086/349706| issn = 0021-1753| volume = 54| issue = 2| pages = 259–262| last = Drabkin| first = I. E.| title = Two Versions of G. B. Benedetti's Demonstratio Proportionum Motuum Localium| journal = Isis| year = 1963| jstor = 228543| s2cid = 144883728}}</ref> With the 1586 [[Delft tower experiment]], the [[Flanders|Flemish]] physicist [[Simon Stevin]] observed that two cannonballs of differing sizes and weights fell at the same rate when dropped from a tower.<ref name="Stevin">{{Cite book|url=https://books.google.com/books?id=YicuDwAAQBAJ&dq=delft+tower+experiment&pg=PA26|title=Ripples in Spacetime: Einstein, Gravitational Waves, and the Future of Astronomy|last=Schilling|first=Govert|date=31 July 2017|publisher=Harvard University Press|isbn=9780674971660|page=26|language=en|access-date=16 December 2021|archive-date=16 December 2021|archive-url=https://web.archive.org/web/20211216025328/https://books.google.com/books?id=YicuDwAAQBAJ&dq=delft+tower+experiment&pg=PA26|url-status=live}}</ref> 

In the late 16th century, [[Galileo Galilei]]'s careful measurements of balls rolling down [[Inclined plane|inclines]] allowed him to firmly establish that gravitational acceleration is the same for all objects.<ref>[[Galileo]] (1638), ''[[Two New Sciences]]'', First Day Salviati speaks: "If this were what Aristotle meant you would burden him with another error which would amount to a falsehood; because, since there is no such sheer height available on earth, it is clear that Aristotle could not have made the experiment; yet he wishes to give us the impression of his having performed it when he speaks of such an effect as one which we see."</ref><ref>{{Cite book |last=Sobel |first=Dava |title=Galileo's daughter: a historical memoir of science, faith, and love |date=1993 |publisher=Walker |isbn=978-0-8027-1343-8 |location=New York}}</ref>{{rp|334}} Galileo postulated that [[air resistance]] is the reason that objects with a low density and high [[surface area]] fall more slowly in an atmosphere. In his 1638 work ''[[Two New Sciences]]'' Galileo proved that that the distance traveled by a falling object is proportional to the [[Square (algebra)|square]] of the time elapsed. His method was a form of graphical numerical integration since concepts of algebra and calculus were unknown at the time.<ref>{{cite book|last=Gillispie|first=Charles Coulston|url=https://archive.org/details/edgeofobjectivit00char/page/n13/mode/2up|title=The Edge of Objectivity: An Essay in the History of Scientific Ideas|publisher=Princeton University Press|year=1960|isbn=0-691-02350-6|pages=3–6|authorlink=Charles Coulston Gillispie}}</ref>{{rp|4}} This was later confirmed by Italian scientists [[Jesuits]] [[Francesco Maria Grimaldi|Grimaldi]] and [[Giovanni Battista Riccioli|Riccioli]] between 1640 and 1650. They also calculated the magnitude of [[Earth's gravity|the Earth's gravity]] by measuring the oscillations of a pendulum.<ref>J. L. Heilbron, ''Electricity in the 17th and 18th Centuries: A Study of Early Modern Physics'' (Berkeley, California: University of California Press, 1979), p. 180.</ref>

Galileo also broke with incorrect ideas of Aristotelian philosophy by regarding [[inertia]] as persistence of motion, not a tendency to come to rest. By considering that the laws of physics appear identical on a moving ship to those on land, Galileo developed the concepts of [[reference frame]] and the [[principle of relativity]].<ref>{{Cite book |last=Ferraro |first=Rafael |url=https://www.worldcat.org/title/141385334 |title=Einstein's space-time: an introduction to special and general relativity |date=2007 |publisher=Springer |isbn=978-0-387-69946-2 |location=New York |oclc=141385334}}</ref>{{rp|5}} These concepts would become central to Newton's mechanics, only to be transformed in Einstein's theory of gravity, the general theory of relativity.<ref name=Weinberg-1972>{{cite book |last=Weinberg |first=Steven |url=https://archive.org/details/gravitationcosmo00stev_0 |title=Gravitation and cosmology |date=1972 |publisher=John Wiley & Sons |isbn=9780471925675 |author-link=Steven Weinberg |url-access=registration}}</ref>{{rp|17}}

[[Johannes Kepler]], in his 1609 book [[Astronomia nova]] described gravity as a mutual attraction, claiming that if the Earth and Moon were not held apart by some force they would come together. He recognized that mechanical forces cause action, creating a kind of celestial machine. On the other hand Kepler viewed the force of the Sun on the planets as magnetic and acting tangential to their orbits and he assumed with Aristotle that inertia meant objects tend to come to rest.<ref>{{Cite journal |last=Holton |first=Gerald |date=1956-05-01 |title=Johannes Kepler's Universe: Its Physics and Metaphysics |url=https://pubs.aip.org/ajp/article/24/5/340/1036024/Johannes-Kepler-s-Universe-Its-Physics-and |journal=American Journal of Physics |language=en |volume=24 |issue=5 |pages=340–351 |doi=10.1119/1.1934225 |bibcode=1956AmJPh..24..340H |issn=0002-9505}}</ref><ref name=Dijksterhuss-1954>Dijksterhuis, E. J. (1954). History of Gravity and Attraction before Newton. Cahiers d'Histoire Mondiale. Journal of World History. Cuadernos de Historia Mundial, 1(4), 839.</ref>{{rp|846}}

In 1666, [[Giovanni Alfonso Borelli]] avoided the key problems that limited Kepler. By Borelli's time the concept of inertia had its modern meaning as the tendency of objects to remain in uniform motion and he viewed the Sun as just another heavenly body. Borelli developed the idea of mechanical equilibrium, a balance between inertia and gravity. Newton cited Borelli's influence on his theory.<ref name=Dijksterhuss-1954/>{{rp|848}}

In 1657, [[Robert Hooke]] published his ''[[Micrographia]]'', in which he hypothesized that the Moon must have its own gravity.<ref name=Gribbin-2017>{{Cite book |title=Out of the shadow of a giant: Hooke, Halley and the birth of British science |last1=Gribbin |last2=Gribbin |first1= John |first2=Mary |isbn=978-0-00-822059-4 |location=London |oclc=966239842 |year=2017 |publisher=William Collins |author-link=John Gribbin}}</ref>{{rp|57}} In a communication to the Royal Society in 1666 and his 1674 Gresham lecture, ''An Attempt to prove the Annual Motion of the Earth'', Hooke took the important step of combining related hypothesis and then forming predictions based on the hypothesis.<ref>{{cite book |last=Stewart |first=Dugald |date=1816 |author-link=Dugald Stewart |title=Elements of the Philosophy of the Human Mind |volume= 2 |url=https://archive.org/details/b28041604/page/n5/mode/2up |page=[https://archive.org/details/b28041604/page/434/mode/2up 434] |publisher=Constable & Co; Cadell & Davies |location=Edinburgh; London }}</ref> He wrote:
{{blockquote|I will explain a system of the world very different from any yet received. It is founded on the following positions. 1. That all the heavenly bodies have not only a gravitation of their parts to their own proper centre, but that they also mutually attract each other within their spheres of action. 2. That all bodies having a simple motion, will continue to move in a straight line, unless continually deflected from it by some extraneous force, causing them to describe a circle, an ellipse, or some other curve. 3. That this attraction is so much the greater as the bodies are nearer. As to the proportion in which those forces diminish by an increase of distance, I own I have not discovered it....<ref>{{cite book |last=Hooke |first=Robert |date=1679 |title=Lectiones Cutlerianae, or A collection of lectures, physical, mechanical, geographical & astronomical : made before the Royal Society on several occasions at Gresham Colledge [i.e. College] : to which are added divers miscellaneous discourses |url=https://archive.org/details/LectionesCutler00Hook/page/n23/mode/2up}}</ref>{{sfnp|Hooke|1679|loc='' An Attempt to prove the Annual Motion of the Earth'', [https://archive.org/details/LectionesCutler00Hook/page/n23/mode/2up page 2, 3]}}}} 
Hooke was an important communicator who helped reformulate the scientific enterprise.<ref name=Guicciardini>{{Cite journal |last=Guicciardini |first=Niccolò |date=2020-01-01 |title=On the invisibility and impact of Robert Hooke's theory of gravitation |url=https://www.degruyterbrill.com:443/document/doi/10.1515/opphil-2020-0131/html |journal=Open Philosophy |language=en |volume=3 |issue=1 |pages=266–282 |doi=10.1515/opphil-2020-0131 |issn=2543-8875|hdl=2434/746528 |hdl-access=free }}</ref> He was one of the first professional scientists and worked as the then-new [[Royal Society]]'s curator of experiments for 40 years.<ref>{{Cite book |last=Purrington |first=Robert D. |title=The first professional scientist: Robert Hooke and the Royal Society of London |date=2009 |publisher=Birkhäuser |isbn=978-3-0346-0037-8 |series=Science networks. Historical studies |location=Basel, Switzerland Boston}}</ref> However his valuable insights remained hypotheses since he was unable to convert them in to a mathematical theory of gravity and work out the consequences.<ref name=Dijksterhuss-1954/>{{rp|853}} For this he turned to Newton, writing him a letter in 1679, outlining a model of planetary motion in a void or vacuum due to attractive action at a distance. This letter likely turned Newton's thinking in a new direction leading to his revolutionary work on gravity.<ref name=Guicciardini/> When Newton reported his results in 1686, Hooke claimed the [[Newton–Hooke priority controversy for the inverse square law |inverse square law portion was his "notion"]].