Galileo is lesser known for, yet still credited with, being one of the first to understand sound frequency. By scraping a chisel at different speed, and by scratching the metal part of knife blade at different spacing scheme, Galileo linked the pitch of the sound produced to the spacing of the chisel’s skips, a measure of frequency.

In 1638, Galileo described an experimental method to measure the speed of light by arranging that two observers, each having a  lantern (lamp) equipped with shutters, observe each other’s lanterns at some distance. The first observer opens the shutter of his lamp, and, the second, upon seeing the light, immediately opens the shutter of his own lantern. The time between the first observer’s opening his shutter and seeing the light from the second observer’s lamp indicates the time it takes light to travel back and forth between the two observers. Galileo reported that when he tried this at a distance of less than a mile, he was unable to determine whether or not the light appeared instantaneously.

Today we know that the reason why Galileo was not able to observe the speed of light over such a short distance is that light travels way too fast for such an experiment. Light travels at 186,282 miles per second; hence it takes only 0.00001073 of a second to traverse these two miles.