Psychologists at the University of California recognized a lack of sleep “as a social repellent” and its effect contagious: “People who come in contact with a sleep-deprived individual, even through a brief one-minute interaction, feel lonelier themselves as a result.”

Asked whether it was night or day that first emerged when the universe came into existence, sixth-century-bc Greek philosopher Thales of Miletus replied, “Night, earlier by a day.”

“When the white man landed on the moon, my father cried,” a young Oklahoma Indian told psychologist Robert Coles in the 1970s. “He was sure Indians were crying up there, and trying to hide, and hoping that soon they’d go back to their earth, the white men.” The boy also spoke to his aunt. “The moon is yours to look at and talk to,” she told him, “so don’t worry.”

A study of sixty-two mammalian species found that animals around the world have shifted into more nocturnal lives. “Humans are now this ubiquitous, terrifying force on the planet,” said lead author Kaitlyn Gaynor, “and we are driving all the other mammals back into the night-time.” The Southeast Asian sun bear, formerly diurnal, now spends as much as 70 percent more time awake at night to avoid humans.

Emily and Charlotte Brontë, insomniacs both, would walk together in circles around the dining room table until they were tired enough to sleep. When Emily died and Charlotte suffered alone, her insomnia worsened; she added to her route, often wandering down neighborhood streets and into the cemetery until daybreak.

When a boat of carousing European sailors on the Bosporus awoke the sleeping Sultan Selim III one night in 1790, the Ottoman leader issued an emergency order to his administration against night revelers: “Warn all ambassadors and Europeans never to perform this shameless act again. I will mercilessly kill whoever does it.”

According to his nephew, Pliny the Elder liked to rise in the middle of the night and study by lamplight. “Admittedly, he fell asleep very easily,” Pliny the Younger wrote, “and would often doze and wake up again during his work.”

In Japanese tradition, ghosts and spirits are more likely to appear at dusk or dawn than in the middle of the night. “In order for people to see them and be frightened by them,” wrote folklorist Kunio Yanagita, “emerging in the pitch-dark after even the plants have fallen asleep is, to say the least, just not good business practice.”

Setting grim tales during nighttime was critiqued as a cliché in 1594 by Thomas Nashe. “When any poet would describe a horrible tragical accident,” he wrote, “to add the more probability and credence unto it, he dismally begins to tell how it was dark night when it was done.”