A colleague told me he read a pre-1970s science fiction short story or novel involving a male astronaut who approached a planet or small moon. When the space traveler landed, he discovered that the world was a hemisphere: one side flat, the rest curved. I am not sure if the flat surface was made up of a maze of structures.

This was not "The Men and the Mirror", in which a huge surface turns out to be perfectly concave. And this was not the Arthur C. Clarke story in which a satellite of one of the Gas Giants in our solar system turns out to be a roughly spherical alien artifact.

A note about physics: above a certain size, such a shape would, as a practical matter, be impossible. Reason: hydrostatic equilibrium. Unless it is an extraterrestrial-produced artifact. Perhaps the story or novel explains how the half-sphere came to be.

  • Just to be clear, was it a perfect solid half sphere and was not a shell filled with bracing on the back side? (That is a question.)
    – DavidW
    Jul 31, 2019 at 22:13
  • It's not "Ideas Die Hard" (link to text online) by Asimov, which involves astronauts orbiting around a fake (hollow) moon?
    – DavidW
    Jul 31, 2019 at 22:21
  • 1
    This almost sounds familiar. I might have read it. Incidentally, just the other day I was remembering a scene in Rocket Ship Galileo where Heinlein has a physicist deliberately play devil's advocate by asking some teenage boys if they can prove the assertion that the moon is a solid sphere instead of the side that faces the Earth just being something insubstantial like a rainbow or hologram. (They were on a ship heading for the moon, but in that timeline nobody had ever gone up there to see the far side of Luna -- or not that the main characters knew about at that moment, anyway.)
    – Lorendiac
    Aug 1, 2019 at 2:08
  • I think that in Niven's Protector there are some planetoids with odd shapes. One's a toroid but there might have been others, the protector had been experimenting with things. Just a thought.
    – moopet
    Aug 1, 2019 at 11:57

1 Answer 1


The story might possibly be Theodore Sturgeon's "The Comedian's Children".

For centuries Iapetus, a moon of Saturn, has appeared several times as bright on one side of Saturn than the other side of Saturn, as seen from Earth.

Once it was discovered that the majority of solar system moons are tidally locked so that one side always faces their primary, it was deduced that Iapetus would probably be the same and thus one side of Iapetus should be many times brighter than the other side. But generations of astronomers wondered what makes one side much brighter than the other, until space probes finally revealed the answer.

So naturally there have been some fictional depictions of Iapetus:


The list is not complete. For example, I remember a visit to Iapetus in the comic strip Space Conquerors:


And I remember that in either the visit to Iapetus in Space Conquerors, or else in Theodore Sturgeon's "The Comedian's Children", Iapetus was a hemisphere.


So I suggest that you look up "The Comedian's Children" and see if it has a hemispherical Iapetus and also is the story you heard of.

And if "The Comedian's Children" isn't it isn't try finding some of the other older Iapetus stories in the Wikipedia list.

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    Iapetus isn't hemispherical in "The Comedian's Children", just half light and half dark. I was tempted to downvote your answer because it seems silly to tell the questioner to go look the story up themselves! A story ID answer should ID the story! But I didn't because it seems you wrote this in good faith. Aug 1, 2019 at 15:50
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    "The Comedian's Children" says: "Iapetus is not a moon like most, round or oblate, but a rock, a drifting mountain some 500 miles in diameter. And before them was the solution to the mystery of the changing moonlight. Some unknown cataclysm has cloven Iapetus, so that it has one sheer face, nearly four hundred square miles of flat plain (or cliff, depending on how you look at it) made of pale basaltic material." So, not a hemisphere. From the Internet Archive.
    – DavidW
    Aug 1, 2019 at 17:21
  • The visit to Iapetus in Space Conquerors finds a plain of glass with higher albedo, not an asymmetrical shape.
    – DavidW
    Aug 1, 2019 at 18:00

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