It was on this day in 1682 that an English astronomer, Edmund Halley, observed a particular comet in the sky. He didn’t discover it, but he did figure out when it was going to come back – only by then, he wasn’t around to see it again. Plus: in the old days comets were believed to be a sign of bad news coming. In one case, that may have actually been right.

Halley’s Comet: Facts About the Most Famous Comet (Space.com)

Comets Breed Fear, Fascination and Web Sites (New York Times)

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Do people still say “look, it’s Halley’s Comet” as a distraction, or is that over for the next 40 years or so?

It was on this day in 1682 that an English astronomer, Edmund Halley, observed a particular comet in the sky.

He didn’t discover the comet. There are recorded observations going back to at least 239 BC, and the word “comet” itself is derived from a Greek word.

Nor was he the first to suggest that comets revisited Earth as they orbited the sun.

What Halley did do was use the theory of gravity as outlined by his personal friend Sir Isaac Newton to calculate out the details of the orbits of comets.

In doing so, he figured out that the comet he’d seen in 1682 was the same one that had been observed in 1607 AND in 1531.

By his calculation, Halley expected the comet to reappear at the end of the year 1758 or the beginning of 1759.

By then, Halley had passed on. Even if he’d been wrong, he would’ve left a pretty good legacy.

He’d personally published Newton’s landmark work known as the Principia, developed a way to measure the distance between Earth and the sun, invented the diving bell, the list goes on and on.

But he was right. The comet reappeared on Christmas Day 1758, right on schedule, and a French astronomer proposed naming it after Halley.

In case you’re wondering, the comet’s next visit will be in 2061.

I mentioned this to my eight year old one night, noting that when Halley’s Comet comes back he’ll be about 50 years old.

To which he replied, extremely ominously, “and you’ll be dead.”

In the old days, before we knew what they really were, comets were usually thought of as a sign of very bad news. Yes, sometimes comets coincidentally showed up before something bad happened, but in at least one case a comet was sort of responsible.

In 1222, a comet appeared in the sky over Mongolia – a comet that Genghis Khan considered his own personal star. He decided this was a sign to go forth and conquer, and that’s what he did, moving all the way across Asia and invading into southeastern Europe.

And the comet that was in the sky back then? Yep – Halley’s.