Law of the Pendulum
At age twenty, Galileo noticed a lamp swinging overhead while he was in a cathedral. Curious to find out how long it took the lamp to swing back and forth, he used his pulse to time large and small swings. Galileo discovered something that no one else had ever realized: the period of each swing was exactly the same. The law of the pendulum, which would eventually be used to regulate clocks , made Galileo Galilei instantly famous.
Except for mathematics, Galileo Galilei was bored with university. Galileos family was informed that their son was in danger of flunking out. A compromise was worked out, where Galileo would be tutored fulltime in mathematics by the mathematician of the Tuscan court. Galileos father was hardly overjoyed about this turn of events, since a mathematicians earning power was roughly around that of a musician, but it seemed that this might yet allow Galileo to successfully complete his college education. However, Galileo soon left the University of Pisa without a degree.