Halley’s Comet’s 1910 return was an astronomical gala: the first passage since photography and spectroscopy had come of age, and an unusually close one — so close that calculations showed the Earth would pass directly through the comet’s tail on 18-19 May.
Spectroscopes then found, among the tail’s gases, cyanogen — chemically kin to cyanide, and genuinely lethal in a laboratory. The French astronomer Camille Flammarion — brilliant populariser, incorrigible speculator — was quoted suggesting the gas might impregnate the atmosphere and “possibly snuff out all life on the planet.” Nearly every working astronomer said plainly what the arithmetic showed: a comet’s tail is a vacuum by earthly standards, and diffusing it through the atmosphere would add poison at the scale of a drop in an ocean. The New York Times and its peers printed both the reassurance and the apocalypse; the apocalypse ran on page one.
Comet-proofing
What followed was a carnival of profitable dread. Hucksters — Chicago and points south were famous for it — sold “comet pills” (sugar, mostly), anti-comet umbrellas, and bottled oxygen; churches filled; some families in cities from the American South to Eastern Europe sealed their windows and keyholes against the gas; a scattering of suicides and heart failures was blamed on comet fear; and observatories fielded letters asking whether cyanide of the sky could be survived in a cellar. Rooftop “comet parties,” meanwhile, toasted the end of the world in champagne — panic and festivity drawing on the same electric sky.
On the night itself, the Earth slid through the tail’s outer streamers and registered — nothing. Not an unusual glow, barely a spectroscopic trace. The comet, which had put on a superb naked-eye show for weeks (upstaged, connoisseurs noted, by the unrelated Great January Comet earlier that year), receded on schedule, leaving the pill-sellers rich and the species intact.
Twain’s appointment
The passage kept one famous appointment. Mark Twain, born two weeks after the comet’s 1835 perihelion, had written in 1909: “I came in with Halley’s Comet… It is coming again next year, and I expect to go out with it. It will be the greatest disappointment of my life if I don’t.” He died on 21 April 1910, one day after the comet’s perihelion — the cosmos, for once, honouring a humorist’s deadline.
The 1910 panic became the textbook case of media-amplified science scare — studied again, with feeling, when the comet’s tame 1986 return met a public raised on its legend.