Halley also personally funded the publication of Newton’s three-volume Principia because England’s leading scientific institution, the Royal Society, “rashly spent all its publishing budget on a history of fish,” according to historian Julie Wakefield. Halley immediately understood the significance of the Principia, which is considered among the most important books in the history of science.* “Now we are truly admitted as table-guests of the Gods,” Halley said of the book. “No longer does error oppress doubtful mankind with its darkness.”

Of course, Halley’s ideas didn’t always hold up. Error still oppressed doubtful humankind (and still does). For example, partly based on Newton’s incorrect calculations of the moon’s density, Halley argued there was a second Earth inside of our Earth, with its own atmosphere and possibly its own inhabitants.

By the time Halley’s comet showed up in 1986, the scientific revolution’s approach to knowledge-building had proven so successful that even third graders like me knew about the layers of the earth. That day in the Ocala National Forest, my dad and I made a bench by nailing two-by-fours to sections of tree trunk. It wasn’t particularly challenging carpentry, but in my memory, at least, it took us most of the day. Then we started a fire, cooked some hot dogs, and waited for it to get properly dark—or as dark as Central Florida got in 1986.

I don’t know how to explain to you how important that bench was to me, how much it mattered that my dad and I had made something together. But that night, we sat next to each other on our bench, which just barely fit the two of us, and we passed the binoculars back and forth, looking at Halley’s comet, a white smudge in the blue-black sky.

My parents sold the cabin almost twenty years ago, but not long before they did, I spent a weekend there with Sarah. We’d just started dating. I walked her down to the bench, which was still there. Its fat legs were termite-ridden, and the two-by-fours were warped, but it still held our weight.

Halley’s comet is not a monolithic spherical miniplanet flying through space, as I imagined it to be. Instead, it is many rocks that have coalesced into a peanut-shaped mass—a “dirty snowball,” as the astronomer Fred Whipple put it. In total, Halley’s dirty snowball of a nucleus is nine miles long and five miles wide, but its tail of ionized gas and dust particles can extend more than sixty million miles through space. In 837 CE, when the comet was much closer to Earth than usual, its tail stretched across more than half of our sky. In 1910, as Mark Twain lay dying, Earth actually passed through the comet’s tail. People bought gas masks and anti-comet umbrellas to protect against the comet’s gases.

In fact, though, Halley poses no threat to us. It’s approximately the same size as the object that struck Earth sixty-six million years ago leading to the extinction of dinosaurs and many other species, but it’s not on a collision course with Earth. That noted, Halley’s comet will be more than five times closer to Earth in 2061 than it was in 1986. It’ll be brighter in the night sky than Jupiter, or any star. I’ll be eighty-three—if I’m lucky.