2. Halley’s Comet led to widespread panic in 1910
The 1910 appearance was the first in which spectroscopic analysis was applied to the comet’s tail, and a review revealed cyanogen to be a component. Cyanogen is a toxic gas. It was also discovered that the Earth would pass directly through the tail during the third week of May. As areas around the globe struggled with the effects of floods, avalanches, and other disasters of the preceding winter, a French astronomer and writer of science fiction, Camille Flammarion, predicted disaster. According to Flammarion, when the earth passed through the tail toxic cyanogen would infuse the atmosphere, and all life on earth was subject to annihilation.
Panic ensued, though it was widely accepted that no where on Earth was safe. More qualified astronomers and scientists tried to convince the public that Flammarion’s hypothesis was scientifically unsound, but to no avail among the poor and superstitious. Flammarion gained support from religious leaders who demanded penance tithes to prevent divine retribution. Anti-comet pills appeared in shops and stores, though they were little more than a scam. An umbrella, designed to protect its users from exposure to the gas sold well. So did gas masks, which were totally unnecessary. In the end, earth passed through the tail and the comet continued on its way. It returned in 1986, to find the earth still well populated, having failed create the apocalypse 76 years earlier.