A light curve is a graph of an object's brightness over time, one of astronomy's most powerful tools. The periodic dip as a planet transits its star reveals the planet's size and orbit; the rise and fall of a supernova traces the physics of the explosion; and irregular dimming, as seen in Tabby's Star, can flag something genuinely unexplained. Surveys now record billions of light curves, which machine learning sifts for the rare and the strange.