Editing Extraterrestrial life (section)

===Early modern period===
[[File:Galileo before the Holy Office - Joseph-Nicolas Robert-Fleury, 1847.png|upright=1.35|thumb|''Galileo before the Holy Office'', a 19th-century painting by [[Joseph-Nicolas Robert-Fleury]]]]
By the time of the [[late Middle Ages]] there were many known inaccuracies in the geocentric model, but it was kept in use because [[naked eye]] observations provided limited data. [[Nicolaus Copernicus]] started the [[Copernican Revolution]] by proposing that the planets revolve around the sun rather than Earth. His proposal had little acceptance at first because, as he kept the assumption that orbits were perfect circles, his model led to as many inaccuracies as the geocentric one. [[Tycho Brahe]] improved the available data with naked-eye observatories, which worked with highly complex [[sextant]]s and [[Quadrant (instrument)|quadrants]]. Tycho could not make sense of his observations, but [[Johannes Kepler]] did: orbits were not perfect circles, but ellipses. This knowledge benefited the Copernican model, which worked now almost perfectly. The invention of the [[telescope]] a short time later, perfected by [[Galileo Galilei]], clarified the final doubts, and the [[paradigm shift]] was completed.<ref>Bennet, pp. 24-27</ref> Under this new understanding, the notion of extraterrestrial life became feasible: if Earth is but just a planet orbiting around a star, there may be planets similar to Earth elsewhere. The astronomical study of distant bodies also proved that physical laws are the same elsewhere in the universe as on Earth, with nothing making the planet truly special.<ref>Bennet, p. 5</ref>

The new ideas were met with resistance from the Catholic church. Galileo was [[Galileo affair|tried]] for the heliocentric model, which was considered heretical, and forced to recant it.<ref>Bennett, p. 29</ref> The best-known early-modern proponent of ideas of extraterrestrial life was the Italian philosopher [[Giordano Bruno]], who argued in the 16th century for an infinite universe in which every star is surrounded by its own [[planetary system]]. Bruno wrote that other worlds "have no less virtue nor a nature different to that of our earth" and, like Earth, "contain animals and inhabitants".<ref>{{cite web |url=http://www.positiveatheism.org/hist/brunoiuw0.htm#IUW0III |title=Giordano Bruno: On the Infinite Universe and Worlds (De l'Infinito Universo et Mondi) Introductory Epistle: Argument of the Third Dialogue |access-date=4 October 2014 |url-status=dead |archive-url=https://web.archive.org/web/20141013120648/http://www.positiveatheism.org/hist/brunoiuw0.htm#IUW0III |archive-date=13 October 2014 }}</ref> Bruno's belief in the plurality of worlds was one of the charges leveled against him by the [[Venetian Holy Inquisition]], which tried and executed him.<ref name="AM8">Aguilera Mochon, p. 8</ref>

The heliocentric model was further strengthened by the postulation of the [[theory of gravity]] by Sir [[Isaac Newton]]. This theory provided the mathematics that explains the motions of all things in the universe, including planetary orbits. By this point, the geocentric model was definitely discarded. By this time, the use of the scientific method had become a standard, and new discoveries were expected to provide evidence and rigorous mathematical explanations. Science also took a deeper interest in the mechanics of natural phenomena, trying to explain not just the way nature works but also the reasons for working that way.<ref>Bennet, p. 30</ref>

There was very little actual discussion about extraterrestrial life before this point, as the Aristotelian ideas remained influential while geocentrism was still accepted. When it was finally proved wrong, it not only meant that Earth was not the center of the universe, but also that the lights seen in the sky were not just lights, but physical objects. The notion that life may exist in them as well soon became an ongoing topic of discussion, although one with no practical ways to investigate.<ref>Bennet, pp. 30-32</ref>

The possibility of extraterrestrials remained a widespread speculation as scientific discovery accelerated. [[William Herschel]], the discoverer of [[Uranus]], was one of many 18th–19th-century astronomers who believed that the [[Solar System]] is populated by alien life. Other scholars of the period who championed "cosmic pluralism" included [[Immanuel Kant]] and [[Benjamin Franklin]]. At the height of the [[Age of Enlightenment|Enlightenment]], even the [[Sun]] and Moon were considered candidates for extraterrestrial inhabitants.<ref>{{Cite web |title=Peoples & Creatures of the Moon {{!}} Life on Other Worlds {{!}} Articles and Essays {{!}} Finding Our Place in the Cosmos: From Galileo to Sagan and Beyond {{!}} Digital Collections {{!}} Library of Congress |url=https://www.loc.gov/collections/finding-our-place-in-the-cosmos-with-carl-sagan/articles-and-essays/life-on-other-worlds/peoples-and-creatures-of-the-moon |access-date=2024-05-10 |website=Library of Congress, Washington, D.C. 20540 USA}}</ref><ref>{{Cite web |last=Parkyn |first=Joel L. |date=April 2019 |title=The Devine Pedagogy: Theological Explorations of Intelligent Extraterrestrial Life |url=https://ore.exeter.ac.uk/repository/bitstream/handle/10871/120770/ParkynJ.pdf?sequence=2 |access-date=May 10, 2024 |website=ore.exeter.ac.uk}}</ref>