Birthday of Galileo (1564) — 'The Book of Nature is Written in Mathematics'

Galileo Galilei was born in Pisa on February 15, 1564. He discovered that falling bodies accelerate uniformly — the distance fallen is proportional to the square of time elapsed, not to velocity as Aristotle claimed. He demonstrated this experimentally with inclined planes and water clocks, without calculus (which Newton would invent 80 years later). He also discovered Jupiter's four largest moons, the phases of Venus, and sunspots. But his greatest legacy was methodological: he insisted that nature obeys mathematical laws, and that those laws must be tested by experiment. He wrote: 'The book of nature is written in the language of mathematics.'