We are visual beings, and qualities such as “insight” and “vision” describe our understanding well beyond sensory inputs. The ability to extend our sight beyond our eyes gives deeper meaning to the observation of Yogi Berra, the great American philosopher of the 20th century: “You see a lot by just watching.”

Visible light is a small sliver of a huge spectrum that includes radio waves with energies as low as 2 × 10-13 eV (48 Hz) used to communicate with submarines, to cosmic gamma rays with energies in excess of 300 GeV (7 × 1025 Hz). Maxwell's equations, written in 1862, predicted that radio waves, infrared radiation, and visible light are different forms of electromagnetic waves. In the ensuing 150 years, we discovered X-rays and gamma rays, and subsequently realized that these forms of energy are also part of the electromagnetic spectrum.

With the development of Quantum Mechanics in the 1920s, we discovered that the energy of these waves cannot be dialed down arbitrarily, but there exists a fundamental “graininess” to light: the photon. An electromagnetic wave of frequency ν is composed of particles of light with energy Emin = ℏν, where Planck's constant h is a universal constant of Nature. Light can display both particle and wave properties. Remarkably, Maxwell's equations predicted that photons with energies less than 10-13 eV to greater than 3 × 10+11 eV all move at the same speed in vacuum. This prediction, yet to be contradicted by experiment, is one of the wonders of light.

Marta García-Matos' and Lluís Torner's Wonders of Light presents a delightful smorgasbord that illustrates how light continues to redefine our daily lives. The chapter “Lighting” reminds us how artificial light liberated us from darkness (and boredom) and protected us from predators; rapidly advancing technology is allowing us to create light that mimics the changing hues of sunlight during the day.