Earth passes through the tail of Halley's Comet
On this day · 19 May 1910
As the comet swept its closest in centuries, Earth glided through its diffuse tail and a global panic followed.
On 19 May 1910, Earth drifted through the gauzy outer tail of Halley’s Comet as the visitor made one of its closest passes in recorded history, sweeping within about 0.15 astronomical units (roughly 22 million kilometers) of our planet. The University of Alaska’s Geophysical Institute notes this approach was far nearer than the comet’s distant 1986 return.
This was a landmark apparition for science: the first Halley return ever photographed and the first studied with a spectroscope. That spectroscope was also the trouble.
Analysts detected cyanogen, a toxic gas, in the tail, and the press promptly imagined Earth poisoned.
Despite calm assurances that the tail was far too thin to harm anyone, hucksters hawked “comet pills” and gas masks to a jittery public. Earth slipped through unscathed. President Taft himself took in the spectacle from the U.S. Naval Observatory.
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