Galileo Galilei (1564–1642)
Birthday: 15 February
Famous story of dropping things off the tower of Pisa, probably apocryphal; didn't do it in reality, only talked about it as a thought experiment. 350 years later, astronauts replicated Galileo's experiment on the Moon (they brought two balls to drop them on the lunar ground), you can see it on YouTube.
Rolled balls of varying mass down inclined planes. Noted that the distance travelled grows with time squared (acceleration). These experiments took him many years for some reason.
There were no stopwatches in that time, so how did Galileo time it? With his lute as an incline, he put bells as gates for the ball to break through. Then spacing the bells increasingly distant so that the chiming sounds became equidistant.
Measuring the acceleration: differences in length increased according to some constant.
| time | 0 | 1 | 2 | 3 | 4 | |||||
| length | 5 | 20 | 45 | 80 | 125 | |||||
| diff | 15 | 25 | 35 | 45 | ||||||
| constant | 10 | 10 | 10 |
The constant varied, it wasn't always 10 as you see above. Galileo couldn't understand it, but we know it was measuring error.
Aristotelian idea: All objects have a natural state that they want to reach. Heavy objects want to go down, heavier objects even more so.
Galileo thought experiment: basket containing ten stones, and a single stone separate. Which of these two objects falls faster? The basket, if heavier, supposedly falls faster. What happens if you tie the eleventh stone to the basket? He arrived to the conclusion that all objects must fall at the same speed.