Editing Stellar parallax (section)

=== Early theory and attempts ===
[[File:Dollond Heliometer 1790.jpg|thumb|The Dollond heliometer of the late 1700s]]
Stellar parallax is so small that it was unobservable until the 19th century, and its apparent absence was used as a scientific argument against [[heliocentrism]] during the [[early modern age]]. It is clear from [[Euclid]]'s [[geometry]] that the effect would be undetectable if the stars were far enough away, but for various reasons, such gigantic distances involved seemed entirely implausible: it was one of [[Tycho Brahe]]'s principal objections to [[Copernican heliocentrism]] that for it to be compatible with the lack of observable stellar parallax, there would have to be an enormous and unlikely void between the orbit of Saturn and the eighth sphere (the fixed stars).<ref>See p.51 in ''The reception of Copernicus' heliocentric theory: proceedings of a symposium organized by the Nicolas Copernicus Committee of the International Union of the History and Philosophy of Science'', Torun, Poland, 1973, ed. Jerzy Dobrzycki, International Union of the History and Philosophy of Science. Nicolas Copernicus Committee; {{ISBN|90-277-0311-6}}, {{ISBN|978-90-277-0311-8}}</ref>

[[James Bradley]] first tried to measure stellar parallaxes in 1729. The stellar movement proved too insignificant for his [[telescope]], but he instead discovered the [[aberration of light]]<ref>{{cite book|url=https://books.google.com/books?id=JARaN7Jmm9cC&pg=PA184|title=The Sky is Your Laboratory|isbn=978-0-387-73995-3|last1=Buchheim|first1=Robert|date=4 October 2007|publisher=Springer }} Page 184.</ref> and the [[astronomical nutation|nutation]] of Earth's axis, and catalogued 3,222 stars.