Ibn al-Haytham, also known in the West as Alhazen, who lived from approximately 950 to 1040, was a pioneer in several scientific and mathematical fields, including physics, optics, astronomy, and analytical geometry. His experiments on how light is refracted by the atmosphere were later developed by Isaac Newton, and he discovered the first law of motion centuries before Galileo. Most importantly, Ibn al-Haytham, a devout Muslim, was committed to a scientific method based on observation, hypothesis and testing, and he helped keep alive the classical spirit of inquiry first developed in ancient Greece. Ibn al-Haytham's groundbreaking work reflects a life of travel and adventure, and this biography introduces this fascinating scientist to a new generation of readers.