What physical law did Newton discover after an apple fell on his head?

In fact, the fact that an apple fell on Newton’s head is a legend. In fact, Newton watched as objects of different shapes and masses fall from a certain height to the ground. Accumulating the results of observations, and having carried out the necessary measurements, he proved that all bodies, regardless of their mass (subject to the same volume), fall to the ground in the same time. This allowed him to discover the law of universal gravitation. In scientific circles, this joke went: that an apple fell on Newton’s head, after which he discovered the force of gravity.