What is Isaac Newton famous for?

Isaac Newton, a towering figure in scientific history, lived in England during the 17th and 18th centuries. While he made contributions to optics, mathematics (inventing calculus!), and physics, he's most famously associated with gravity. The popular story, though likely embellished, involves an apple falling from a tree, prompting Newton to ponder why it fell straight down rather than sideways or upwards. This led him to formulate his law of universal gravitation, explaining that every particle attracts every other particle with a force proportional to their masses and inversely proportional to the square of the distance between them. So, while insulin, penicillin, and steam power are all important discoveries, they weren't Newton's doing. He's the gravity guy!