During the early 1800s, a scientific revolution was underway in Britain and France as physicists fiercely debated the truth or falsity of two optical theories: that light is composed of either waves or particles. Many famous scientists, including Sir David Brewster, conducted independent research in an attempt to ascertain the true nature of light. Out of this research came the basis of modern optical study, but what made Brewster remarkable was his ability to apply his research toward practical ends, inventing such devices as the kaleidoscope and the improved stereoscope.

Brewster entered the University of Edinburgh in 1794 as a divinity student, and although he completed his studies in 1800 and was licensed to preach in 1804, he never was ordained a minister. Instead, he developed a knack for building precise scientific instruments while at college and performed some fledgling experiments with light.

His curiosity about light and the new controversy...