Galileo is by many regarded as the father of modern science, not because he was the first scientist. But because he started to use mathematics as a tool to measure and quantize his research.
As a boy he sometimes got bored listening to the Sunday sermon, and as he let his eyes wander he noticed that the chandeliers were swinging slightly back and forth because the church servant had set them into motion while lighting them.
He timed the pendular motion against his own pulse and found that the chandeliers spent exactly the same time moving from one side to the other, even if the distance between the two points varied.
Galileo had made his first discovery: The harmonic oscillator!