1645 in science

The year 1645 in science and technology involved some significant events.

Astronomy

The Solar cycle enters the 70-year Maunder Minimum.{{cite journal|authorlink=John A. Eddy|last=Eddy|first=John A.|title=The Maunder Minimum|journal=Science|volume=192|issue=4245|pages=1189–1202|date=June 1976|pmid=17771739|doi=10.1126/science.192.4245.1189|jstor=17425839|bibcode=1976Sci...192.1189E|s2cid=33896851 }}
First published map of the Moon produced by Michael van Langren.{{cite web|url=http://galileo.rice.edu/sci/observations/Moon.html|title=The Galileo Project|accessdate=September 14, 2007|archiveurl = https://web.archive.org/web/20040623085326/http://galileo.rice.edu/sci/observations/Moon.html |archivedate = June 23, 2004|url-status=dead}}
A version of the law of gravitation is suggested by Ismaël Bullialdus in his {{lang|la|Astronomia philolaica}}.

October 18 – English physician Daniel Whistler presents the first printed pediatric text on rickets, {{lang|la|De Morbo puerili Anglorum, quern patrio idiomate indigense vocant "The Rickets"}}, as his MD thesis at Leiden University.{{cite ODNB|first=Robert L.|last=Martensen|title=Whistler, Daniel (1618/19–1684)|year=2004|url=http://www.oxforddnb.com/view/article/29215|accessdate=January 26, 2012|doi=10.1093/ref:odnb/29215}}

A magic lantern is invented by Althanasius Kircher; like a slide projector, it could project enlarged drawings onto a wall.

Publication of Robert Dudley's Dell'Arcano del Mare begins in Italian at Florence. A comprehensive work on navigation, shipbuilding and astronomy, it includes an original maritime atlas of the entire world, which is the first such in print, the first made by an Englishman, and the first to use the Mercator projection.{{cite encyclopedia|url=http://www.britannica.com/EBchecked/topic/173043/Sir-Robert-Dudley|title=Sir Robert Dudley|year=2009|encyclopedia=Encyclopædia Britannica|accessdate=October 15, 2009}}