Through the tail of Halley’s Comet and 15 other notable mass freakouts

On this date 110 years ago, the Earth passed through the tail of Halley’s comet. A French astronomer noticed that a spectroanalysis of the comet suggested the presence of cyanogen, a toxic gas. So, naturally, he announced the gas would “impregnate the atmosphere and possibly snuff out all life on the planet.”