Sir Isaac Newton was born on January 4, 1643, in Lincolnshire, England. He was born prematurely, so small that no one expected him to live more than a few hours. Amazingly, he did survive, and grew up to change our understanding of the world in ways that no one could have predicted. His astonishing survival was just a hint of the incredible things to come.

Sir Isaac didn’t have an easy childhood. He was deeply lonely and got into fights with other boys at school. His mother hoped that her son would become a farmer, but he neglected his chores and got into even more trouble. All the while, young Isaac was keenly observing the world, preparing himself to answer questions that few people dared to even ask. His lifelong search for those answers led him to create the reflecting telescope, discover gravity, and develop the three laws of motion—scientific advancements that still benefit us today.

Not all of Sir Isaac’s endeavors were successful, though. In his later years, he spent a tremendous amount of time on the study of alchemy, or how to turn ordinary substances into gold. After he died in 1727, his fellow scientists were embarrassed to find Sir Isaac’s extensive notes on alchemy, and his writings were kept hidden for centuries. But scientific advancement depends on the desire to investigate new ideas, take risks, make mistakes, and believe in the impossible. We owe Sir Isaac Newton a great debt for his willingness to do just that.

Amelia Earhart was born on July 24, 1897, in Atchison, Kansas. Even as a child, her daring and love of adventure were on full display. Amelia was born in a time when very strict rules dictated what women should and should not do. She challenged those rules at every turn, making it possible not just for herself to live her dreams, but for other women as well.

During World War I, Amelia was so moved by the suffering of wounded soldiers that she left college to work as a nurse’s aide. After the war, she had her first airplane ride in 1920. Amelia was immediately captivated by the thrilling freedom of flight. She knew at once that becoming a pilot was what she wanted more than anything in the world. Amelia worked tirelessly to achieve her dream, even when others tried to stand in her way. She proved them all wrong by setting or breaking several records, including being the first woman to fly solo across the country.

Amelia’s final flight, in 1937, was an attempt to fly around the entire world. Somewhere over the Pacific Ocean, though, something went terribly wrong, and Amelia and her copilot, Fred Noonan, vanished without a trace. To this day, no one knows what really happened, though new theories—and perhaps even new evidence—arise from time to time. The mystery behind Amelia’s disappearance may never be solved, but her world-changing legacy lives on.