On Christmas Day, December 25, 1642, a baby boy was born so small and weak in a farmhouse in Woolsthorpe, England, that his mother said he could fit inside a quart mug. Nobody expected him to survive the night. But baby Isaac Newton hung on. His father had died three months before he was born, and his mother soon remarried, leaving little Isaac to be raised by his grandmother on the family farm. He was a lonely, scribbling, curious kid who built little windmills, sundials, and a tiny water clock instead of doing chores.
Isaac eventually went to Cambridge University, but in 1665 a deadly plague swept through England and the school closed. Isaac went home to Woolsthorpe and spent the next 18 months alone, thinking. During that time, sitting in the orchard, he watched an apple fall from a tree. The story goes that he wondered why the apple always fell straight down - and realized the same force pulling the apple was holding the Moon in its orbit. He had discovered gravity. He also figured out the three laws of motion and used a glass prism to prove that white sunlight was made of all the colors of the rainbow.
Isaac kept his discoveries secret for years before finally publishing the Principia Mathematica in 1687, considered the most important science book ever written. He explained how planets move, how tides happen, how to build telescopes, and why apples fall. He died in 1727 and was buried in Westminster Abbey alongside kings. Every rocket, every satellite, every roller coaster on Earth still uses the rules Isaac Newton worked out under that apple tree.
