In Isaac Asimov's story NIGHTFALL, enlightened scientists try to figure out why chaos breaks out on their planet (called Lagash in the short story, Kalgash in the novel) every 2000 years or so. (Interesting timespan that he chose, I always thought!) Archaeologists have determined that several civilizations have been lost this way; in fact, all history, learning, and science is totally destroyed during these mysterious periods of planetary chaos. Why? And so, scientists, astronomers, smart big shots of all kinds, descend on the problem. They discover that a planetary alignment occurs every 2049 years. Could this be it?
Asimov, diehard atheist, was attending Columbia University at the time he authored this amazing tale, an ode to our human and uniquely self-centered ignorance. He perfectly describes the arrogance of scientists and imitates their voices, which are often just so jolly pleased with themselves. The scientists discover an ancient holy book by a group called the Apostles of Flame, counseling them to GO INSIDE and STAY THERE during the period of said alignment, in which the world will be destroyed by darkness and an accompanying torrent of fire. The scientists snort derisively. Right! And miss the big celestial event? Ha! The scientists study the alignment from every which-way, they calculate and re-calculate. They think they know what will happen, perhaps a deviation in Kalgash's moon. What else could it POSSIBLY be? They can't imagine what they don't know, what they haven't seen.
It's right there, in the title of the story. And yet, as you read, and you read what hour of the day it is and which star is visible--orange, pink, yellow... you take note of it like the people who live on the planet, who have fond feelings for each of their planet's six stars. It doesn't occur to you, on first reading... wait? There is always a star. It is always light. Of course they don't understand what will happen; they've never seen it.
We can't know, what we can't know.
And then, it happens:
[On Kalgash] eclipse on one-sun days (Dovim) occurs every 2049 years. Therefore, "nightfall" occurs once every 2,049 years, when the sole sun on one side of the planet is eclipsed for half a day.
Since the population of Kalgash has never experienced universal darkness, the event would be devastating and the population, with even short exposure (15 minutes), can be susceptible to major trauma and possibly death from shock. When nightfall occurs and the stars appear for the first time in millennia on Kalgash, most people became mentally damaged in the process (at least temporarily) and civil disorder breaks out. Cities are destroyed in massive fires and civilization - as previously known - collapses.
The stars come out, the torrent of fire. They have never seen them. They seem to be falling on them. They go insane with terror.
The last line of the short story was simply: Nightfall.
Black swan theory
In Nassim Nicholas Taleb's definition, a black swan is a large-impact, hard-to-predict, and rare event beyond the realm of normal expectations. Taleb regards many scientific discoveries as black swans—"undirected" and unpredicted. He gives the September 11, 2001 attacks as an example of a Black Swan event.
The term black swan comes from the ancient Western conception that all swans were white. In that context, a black swan was a metaphor for something that could not exist. The 17th Century discovery of black swans in Australia metamorphosed the term to connote that the perceived impossibility actually came to pass.
Taleb notes that John Stuart Mill first used the black swan narrative to discuss falsification.
The high impact of the unexpected
Before Taleb, those who dealt with the notion of improbable, like Hume, Mill and Popper, focused on a problem in logic, specifically that of drawing general conclusions from specific observations. Taleb's Black Swan has a central and unique attribute: the high impact. His claim is that almost all consequential events in history come from the unexpected—while humans convince themselves that these events are explainable in hindsight.
NSFW, unless you work some cool place on the coasts. (Lyrics include F-word. Video artsy and nonoffensive.)
Black Swan - Thom Yorke