Here's why Mark Twain was linked to Halley's comet

American writer and humorist Samuel Langhorne Clemens, better known by his pen name Mark Twain, made several surprising connections during his long and well-lived life, including friendships with great thinkers of his era such as Helen Keller and Frederick Douglass. Perhaps even more surprising is the connection he had from birth with a very famous and rare natural phenomenon, Halley's Comet.

Per Space, Halley's Comet is possibly the most well-known comet of all time. The first recorded observation of Halley's dates back to 239 B.C.E., although it wasn't officially named until English astronomer Edmond Halley "examined reports of a comet approaching Earth in 1531, 1607 and 1682," deduced it was the same comet, and predicted it would return in 1758. It did, although Halley did not live to see it. It continues to swing by earth about every 75 years, and did so just as Twain was born in 1835. (Pronunciation guide: "Halley" rhymes with "valley.") As the Washington Post reported in 1985, it was the first time that a periodic pattern was determined for a comet — that the same comet made regular, predictable trips past Earth.

'I came in with Halley's Comet ... and I expect to go out with it'

Twain was aware of his connection with Halley's Comet, wrote the Washington Post. In 1909, Twain told his biographer, Albert Bigelow Paine, "I came in with Halley's Comet ... It is coming again ... and I expect to go out with it ... The Almighty has said, no doubt: 'Now here are these two unaccountable freaks; they came in together, they must go out together.'" Sure enough, when Twain died of a heart attack on April 21, 1910, Halley's was back, making its way past the earth for the first time in 75 years — the first time since Twain's birth.

In 1985, right before the comet made its return to earth for the first time since Twain's death (as pictured above), the United States Postal Service honored Twain, Halley's Comet, and their connection to each other with a memorial aerogramme. As reported by The New York Times, the aerogramme had its first day of issue in Twain's hometown of Hannibal, Missouri, and featured portraits of the writer and the comet. The aerogrammes went for 36 cents in 1985; today, according to an ad on Astromart, you can get one for $4.