Why is the night sky dark?
Edgar Allan Poe, the enigmatic poet and literary critic who created short stories combining human horror and science fiction, may have been the first person to suggest a possible solution to Olbers’ paradox, an astronomical riddle that perplexed scientists for centuries.
Anthony Aguirre, a physics professor at the University of California—Santa Cruz, says when we find a paradox and explore it and study it, the effort may lead us on a beguiling path that gets close to the truth. In a short essay in John Brockman’s book “This Will Make You Smarter,” Aguirre says Olbers’ paradox is one of his favorites. It was named for German astronomer Heinrich Wilhelm Olbers, who recognized that the darkness of the night sky conflicted with the idea of an infinite, eternal and static universe, which was dominant scholarly view during his lifetime (1758-1840). If the universe were fixed and static and filled with an infinite number of stars and galaxies, he figured, any sight line from earth would end on a very bright star. So the night sky would have to be as bright as day.
Why is the sky dark at night? Why don’t we see light from all those stars? Aguirre writes that scientists grappled with this puzzle for centuries, coming up with all sorts of unworkable solutions. Could there be a dynamic, expanding and evolving universe? Poe thought so, Aguirre observes, and the scientific world took a long time to catch up.
Poe was no scientist, but he had a restless imagination and a mind full of esoteric knowledge. Contemporary literary critics didn’t much like “Eureka,” his lengthy 1848 prose poem on the nature and origins of the universe. But many scholars say he came up with a rudimentary version of how modern science explains the universe. In a New York Times story, Emily Eakin explains Poe’s “uncanny display of prescience.” Rather than static and eternal, Poe envisioned universe exploding in “one instantaneous flash” from a “single primordial particle.” Eighty years before scientists hammered out the math, she writes, Poe had envisioned a crude description of the Big Bang theory, which became a mainstream idea in the 1960s. She notes Poe also imagined an expanding universe that might eventually collapse, and something like black holes. And she explains that Poe’s thoughts on the Olbers paradox have turned out to be right: he imagined that the universe, while inexpressibly and unimaginably great, was finite in time and space, and if the speed of light is also finite, the light from some of those stars would be eons away and not visible from earth. Watch a scientific explanation of the Olbers paradox here.
Aguirre is wrestling with a number of paradoxes, and he considers them a gift. “Nature appears to contradict itself with the utmost rarity,” he writes, “so a paradox can be an opportunity for us to lay bare our cherished assumptions and discover which of them must be let go….and reveal…that the very model of thinking we used to create the paradox must be replaced.”