Chapter 6
Natural Wonders » Odd Coupling

ombine hydrogen peroxide and chlorine to make a glowing (and poisonous) mixture that's a window into the weird world of quantum physics. Before the discovery in the 1920s of quantum mechanics-laws that explain the way the world works on the very small scale of atoms and electrons-the fact that bleach and peroxide glow when mixed would have seemed like just another chemical reaction that gives off light, like fire or fireflies. But it's actually a glimpse into the impossible.

Hydrogen peroxide decomposes when it meets chlorine, releasing molecules of oxygen, each of which has one electron in a high-energy state. When the electrons inevitably return to a low-energy state, the excess energy comes off as a photon of light, creating a glow. Simple- but there are two problems.