Ulugh Beg’s curiosity burned as bright as the stars. He yearned to count every star in the sky, every day in a year, and to know why the seasons change. Fueled by his deep faith, Ulugh Beg’s quest for knowledge led to the creation of new schools, the world’s largest observatory and star catalog, and innovative tools to better chart the secrets of the skies. Although some doubted him, he never stopped searching for answers. And because of his determination, our understanding of the world has changed—forever.