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The year 1639 in science and technology involved some significant events.
thumb|left|Jeremah Horrock's observation of Venus transit across the Sun in 1639. From his work Venus in sole visa, printed 1662
Astronomy
- Giovanni Battista Zupi observes that the planet Mercury has orbital phases.
- December 4 (November 24 in Julian calendar) – English astronomers Jeremiah Horrocks and William Crabtree are the first and only scientific observers of a transit of Venus, predicted by Horrocks.
Exploration
- The Casiquiare canal, a river forming a natural canal between the Amazon River and Orinoco River basins, is first encountered by Europeans
Mathematics
- Girard Desargues introduces the concept of infinity into geometry.
Births
- April 12 – Martin Lister, English naturalist and physician (died 1712)
- December 18 – Gottfried Kirch, German astronomer (died 1710)
- approx. date – Daniel Greysolon, Sieur du Lhut, French explorer (died 1710)
Deaths
- June 6 – Peter Crüger, German polymath (born 1580)
- August 7 – Martin van den Hove, Dutch astronomer (born 1605)
- Mutio Oddi, Italian mathematician (born 1569)