1638 in science
- December 21 – Total eclipse of the moon falls on the same day as the winter solstice, for the first time in the Common Era.
- March 27 earthquake in Calabria (it) (Italia).
- June 8 earthquake in Calabria (it). The epicentre was in Crotone.
- The final book of the now-blind Galileo, Discorsi e dimostrazioni matematiche, intorno à due nuove scienze is published in Leiden, dealing with the strength of materials and the motion of objects. In it, he discusses the square-cube law, the law of falling bodies and infinity. He also discusses his experimental method for measuring the speed of light; he has been unable to determine it over a short distance.
- Publication of The Man in the Moone, or the Discovrse of a Voyage thither "by Domingo Gonsales" (actually by Francis Godwin, Bishop of Hereford (died 1633)), an early example of science fiction.
- January 1 (NS January 11) – Nicolas Steno, Danish pioneer of geology (died 1686)
- March 28 – Frederik Ruysch, Dutch physician and anatomist (died 1731)
- April 19 - Niccolao Manucci, Italian physician, writer and traveller (died 1717)
- May 11 – Guy-Crescent Fagon, French physician and botanist (died 1718)
- June 8 – Pierre Magnol, French botanist (died 1715)
- June 29 - Heinrich Meibom, German physician and scholar (died 1700)
- July 22 - Theodor Kerckring, Dutch anatomist and chemical physician (died 1693)
- November 21 - Luca Tozzi (it), Italian physician (died 1717)
- November – James Gregory, Scottish mathematician and astronomer (died 1675)
- Paolo Falconieri, Florentine polymath (died 1704)
- February 26 – Claude Gaspard Bachet de Méziriac, French mathematician (born 1581)
- April 15/16 – John Tradescant the elder, English botanist (born c. 1570s)
- October 21 – Willem Blaeu, Dutch cartographer (born 1571)
- October 29 – Adrian von Mynsicht, German alchemist (born 1603)
- December 7 - Epifanio Ferdinando (it), Italian physician and philosoph (born 1569)
- Galileo Galilei (1974). Two New Sciences. Madison: University of Wisconsin Press. ISBN 0-299-06404-2.
- Poole, William (2010). "Kepler's Somnium and Francis Godwin's The Man in the Moone: Births of Science-Fiction 1593–1638". In Houston, Chloë. New Worlds Reflected: Travel and Utopia in the Early Modern Period. Farnham: Ashgate. pp. 57–70. ISBN 978-0-7546-6647-9.