In Isaac Asimov’s "Nightfall", the people of another world are driven mad because they see how many stars are in the sky when all six suns are hidden. This happens every two thousand years, and civilization falls apart.

Two of the scientists construct a makeshift planetarium that is covered in black velvet and shows a couple dozen holes in the roof to simulate the stars. They thought they might find a way to immunize themselves to the effect, if in fact seeing these “stars” is what drives you mad.

The psychologist of the group figures out why the experiment fails, and begins to explain it a couple of times, but is interrupted. Did the author ever explain why the experiment fails? The psychologist couldn’t possibly know there were tens of thousands of bright stars visible, and that is what causes the madness.

  • Seems to me he did, but an answer would require a quote from the story, which I don't have access to at the moment.
    – Zeiss Ikon
    Commented Jun 12, 2019 at 12:26
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    I always thought that the description of the experimental planetarium was supposed to invoke amused pity in the reader, who has seen the actual stars and would know what a pathetic substitute the described apparatus would be. Especially because the planet in the story is nearer to the galactic center and would have a night sky even more dramatic than our own, when finally revealed. So no explanation from the psychologist should even be necessary.
    – tbrookside
    Commented Jun 12, 2019 at 13:04

3 Answers 3


In the story Faro 24 and Yimot 70, who constructed the makeshift planetarium, say that when they opened the holes in the roof, what they saw was just a dimly lit roof:

...The caps fell away and the roof glittered all over with little dots of light-"


"Well--nothing. That was the whacky part of it. Nothing happened. It was just a roof with holes in it, and that's just what it looked like.

So part of the problem is that their illusion was not convincing enough, but we don't ever actually find out if the psychologist, Sheerin 501, had the right idea.

The author does explain why it fails. The astronomers are imagining a relative few stars being visible:

Say that there were a lot of suns that far off; a dozen or two, maybe.

Whereas at the end of the story we find out there are far more visible stars than in Earth's night sky:

Not Earth's feeble thirty-six hundred Stars visible to the eye -- Lagash was in the center of a giant cluster. Thirty thousand mighty suns shown[sic] down in a soul-searing splendor that was more frightening in its awful indifference than the bitter wind that shivered across the cold, horribly bleak world.

So yes, the author explains why the experiment failed, but never makes it clear if the psychologist might have correctly guessed it. (My suspicion is that he did not.)

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    I just listened to the story on audiobook, that’s why I was wondering. At least twice the psychologist seems to have had a revelation, but is interrupted and doesn’t finish his thought.
    – CigarDoug
    Commented Jun 12, 2019 at 14:21
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    You're right, there are 2 times he starts to explain - once just before the Cultist is heard trying to sabotage the cameras, and again just before the eclipse when he is interrupted by one of the scientists (Aton) suffering from the effects of the darkness. But we never get to hear what he thinks the problem is.
    – DavidW
    Commented Jun 12, 2019 at 14:25
  • I'm going to accept this as the answer, your reasoning was the same as mine as to WHY it didn't drive them mad. My real question was what did the psychologist think, because even he thought there were only a dozen stars tops in the Universe. But I don't think we will ever know for sure.
    – CigarDoug
    Commented Jun 18, 2019 at 13:17

My understanding was always that it wasn't the stars themselves which caused the problem, it was the knowledge of just how large the universe was. Even had they put all 30,000 dots, that would have done nothing, because the point of the star is the knowledge that it is a star, the same as one of your six suns, but a distance away so incomprehensible that the star has the appearance of a single point. And this isn't one star, it is thousands upon thousands of stars.

The book itself it based on a quote of Ralph Waldo Emmerson, given to Asimov by his editor John Campbell.

If the stars should appear one night in a thousand years, how would men believe and adore, and preserve for many generations the remembrance of the city of God!

Campbell believed, which he told Asimov, that in fact this wouldn't be the case, and that men would go mad, because these men wouldn't know of the universe, and it would the knowledge of the universe that breaks them. Ultimately, it's one of the core concepts of science fiction that's expressed in this book - the world is far, far larger and more complex than what we think it is. And that knowledge is dangerous, but also perhaps worth knowing despite its danger. Nightfall is beautiful in that sense, and thus had its well deserved place amongst Asimov's greatest works.

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    Interesting POV, but the story is introduced by talking about a fair ride that was just a brief travel through a dark tunnel having some important psychological effects on the population. And those in that ride would not get any feeling that the universe was bigger than what they assumed it to be.
    – SJuan76
    Commented Jun 12, 2019 at 23:11
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    It's been a while since I read the story, but I'm pretty sure that even in story, they say that while that does have seriously bad effects, that doesn't explain the level of destruction caused by each nightfall.
    – Halfthawed
    Commented Jun 12, 2019 at 23:16
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    This should be the accepted answer. It is quite obvious in the story that it is the shock of realization that drives people mad - the fact that they feel (some more, some less) uncomfortable during darkness might contribute to that, but it is clearly not the cause. The story also has someone mention that at previous eclipses, some people were not affected: young children, people who were drunk at that time and people with low intelligence - in short: people who were not (fully) able to comprehend the significance of what they were seeing. Commented Jun 13, 2019 at 10:59
  • @VolkerLandgraf On the other hand, in a human population, I wouldn't expect anywhere close to a majority to "comprehend the significance of what they were seeing". If anything, human myths about the stars make the universe seem smaller. You really need a notion of "hmm, maybe there are other stars in the universe, with planets and possibly other peoples" before you'd get much impact on the scale, I'd think - and then you use a telescope and realize that between each of the naked-sight visible stars, there's so many more, and then the Hubble comes in "and it's really full of stars!".
    – Luaan
    Commented Jan 4, 2021 at 14:52

I always thought that the issue with the experiment was that the psychologist knew beforehand what to expect, and they did control the situation.

They were the ones who designed the experiment, who implemented, who put it in motion, and they always were in control and could turn on the light or open a window if they wished to.

They were trying to check if darkness or "the stars" were responsible by itself of the breakdown of people, as a kind of "physical trigger". But they were losing the "strange situation out of my control" factor.

Think for example that the people in the fair ride that was riding through a dark tunnel didn't become mad, either; the problems they developed were far milder than that (claustrophobia and the like). They also knew beforehand what was ahead of them and that it would last only a brief time, which would have helped them avoid the worst effects of darkness.

Also, probably "mad" is a bit too strong here; a better term would be panicked. Yes, the common people became a savage horde bent on punishing the "heretics", but they were sane enough to be able to find them (in the darkness!) and were being pushed by some demagogues. Maybe the scientists, who knew what was coming and that it was a natural phenomenon that would last a limited amount of time would have been able to keep calm enough to pass through the night.

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