December 7 – Danish astronomer Ole Rømer measures the speed of light by observing the eclipses of Jupiter's moons, obtaining a speed of 140,000 miles per second (approximately 25% too slow).
^Sarjeant, William A.S. (1997). "The earliest discoveries". In Farlow, James O.; Brett-Surman, Michael K. (eds.). The Complete Dinosaur. Bloomington: Indiana University Press. pp. 3–11. ISBN0-253-33349-0.