 Calculus. The mathematical study of how things change. It includes differential calculus, rate of change using slope as a function, and integral calculus, determining quantities like areas and volumes under changing conditions. Two people responsible for calculus. Isaac Newton, the guy behind the laws of cartoons, the guy who hypothesized light is made up of particles called karpus gills which allow us to see color when they enter our eyes, or just the apple guy. And Godfrey Leibniz. Both Newton and Leibniz are independently responsible for the foundations of calculus that we see today. Now, did calculus start with them? Of course it didn't. Let's go back in time.