Editing Venus (section)

===Venus and early modern astronomy===
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|footer=In 1610 [[Galileo Galilei]] observed with his telescope that [[Phases of Venus|Venus showed phases]], despite remaining near the Sun in Earth's sky (first image). This proved that it orbits the [[Sun]] and not Earth, as predicted by [[Copernicus]]'s [[heliocentric model]] and disproved Ptolemy's [[geocentric model]] (second image).
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|image1 = Phases-of-Venus2.svg|
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When the Italian physicist [[Galileo Galilei]] first observed the planet with a telescope in the early 17th century, he found it showed [[planetary phase|phases]] like the Moon, varying from crescent to gibbous to full and vice versa. When Venus is furthest from the Sun in the sky, it shows a [[Elongation (astronomy)|half-lit phase]], and when it is closest to the Sun in the sky, it shows as a crescent or full phase. This could be possible only if Venus orbited the Sun, and this was among the first observations to clearly contradict the Ptolemaic [[geocentric model]] that the Solar System was concentric and centred on Earth.<ref name="palmieri"/><ref name="Fegley"/>

The 1631 [[transit of Venus]], while not recorded, was the first one successfully predicted, by [[Johannes Kepler]] and his calculations, which he published in 1629. The following [[1639 transit of Venus]] was accurately predicted by [[Jeremiah Horrocks]] and observed by him and his friend, [[William Crabtree]], at each of their respective homes, on 4{{spaces}}December 1639 (24 November under the [[Julian calendar]] in use at that time).<ref name="Kollerstrom"/>

[[File:Lavender - Jeremiah Horrocks (1618–1641).jpg|thumb|Twentieth century painting of [[Jeremiah Horrocks]] observing the [[1639 transit of Venus]].]]

The [[atmosphere of Venus]] was discovered in 1761 by Russian polymath [[Mikhail Lomonosov]].<ref name="Marov2004"/><ref name=Britannica/> Venus's atmosphere was observed in 1790 by German astronomer [[Johann Schröter]]. Schröter found when the planet was a thin crescent, the cusps extended through more than 180°. He correctly surmised this was due to [[scattering]] of sunlight in a dense atmosphere. Later, American astronomer [[Chester Smith Lyman]] observed a complete ring around the dark side of the planet when it was at [[inferior conjunction]], providing further evidence for an atmosphere.<ref name=Russell_1899/> The atmosphere complicated efforts to determine a rotation period for the planet, and observers such as Italian-born astronomer [[Giovanni Cassini]] and Schröter incorrectly estimated periods of about {{val|24|u=hours}} from the motions of markings on the planet's apparent surface.<ref name=Hussey_1832/>

[[File:Venus Drawing.jpg|thumb|left|upright=0.9|The "[[black drop effect]]" as recorded during the 1769 transit|alt=A hand-drawn sequence of images showing Venus passing over the edge of the Sun's disk, leaving an illusory drop of shadow behind]]