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Another question based off of this one here. Let's say on a cube styled Earth-like planet, there was a similar race to humans. If the differences in the planets were minimal (besides, you know, the whole cube part), how would the two civilizations change and grow (compared to each other)?

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    $\begingroup$ Is this a social question, or are you interesting in weather and environmental effects as well. You would have 6 sides, but only 4 sides would be feasibly inhabitable...North and south facing sides would have interesting sunlight patterns. I'm unsure if a cube world would have a seasonal tilt either $\endgroup$ – Twelfth Jan 16 '15 at 18:40
  • $\begingroup$ You've not described the cube (the prior question has a wide variety of answers). Completely cubical? How big? How deep is the atmosphere? Are the edges perfect, or are there some passes in your mountain ranges? Magnetosphere? Etc. $\endgroup$ – user3082 Jan 16 '15 at 18:45
  • $\begingroup$ All of them as normal as the Ancients could make them (to the cube Earth), except I think i like the idea of no passes so there could be as close as 6 different worlds in 1. And, @Twelfth, I am intersted in as many effects possible. I am trying to make a cube like planet for either a scenario or a story. $\endgroup$ – Shadow Z. Jan 16 '15 at 18:47
  • $\begingroup$ That depends on what it means to have a cubic planet. I assume gravity is (somehow) perpendicular to the surface? Does it have days/nights/seasons like earth? $\endgroup$ – frodoskywalker Jan 16 '15 at 19:45
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    $\begingroup$ @ShadowZ The edges will also be outside of the habitable atmosphere, there wouldn't likely be any weather between the faces and any passes will need to be underground. $\endgroup$ – Samuel Jan 16 '15 at 23:40
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Assuming the cube world is the same as from your previous question things would be very different.

The edges of the cube are mountains so high that they are literally impossible without the magic you added to keep them there. This would create six realms that are, essentially, totally isolated from one another.

Six worlds, one planet. A sentient race living on one of the faces would need to develop mountaineering-space-suits or have some incredible mining abilities before they could get to another face of the cube.

It's possible that life could make it to all the faces via single celled organisms through groundwater fissures. After that you would have six faces that take possibly very different paths of evolution. To view another face would be to view something quite alien.

According to Karen Masters, an astronomer at Cornell, the oceans would be in the center of each face, not flowing over any of the edges. She further describes the weather differences depending on which axis your cube is spinning on.

enter image description here

The gravity of such a planet would make walking around on it strange indeed. Each face would seem like a massive bowl, surrounded by mountains. The edges would be so high in fact that they would be sticking out of the habitable atmosphere.

From Jesse Berezovsky, Professor of Physics, Case Western Reserve University:

Interestingly, we see that the large majority of the cube's surface is outside the atmosphere. Since humans can survive only at about 10km above the earth's surface, this means that the habitable land on the cube would be a narrow ring around the oceans, about 10km wide.

enter image description here

And from "The Physicist" at http://www.askamathematician.com/

enter image description here

The vast majority of the Earth would take the form of vast, barren expanses of rock, directly exposed to space. If you were standing on the edge of a face, and looked back toward the center, you’d be able to clearly see the round bubble of air and water extending above the flat surface. I strongly suspect that it would be pretty.

So, our two civilizations would be very different indeed. Though the cube-worlders would probably have something like the phrase "all the corners of the Earth" though it would mean something quite different.

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  • $\begingroup$ So I could possibly make 6 mini planets on 1 planet, having them each follow their own paths until they get the tech to travel to the other sides? And then, each side would be different and original compared to the others? $\endgroup$ – Shadow Z. Jan 16 '15 at 18:32
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    $\begingroup$ This is a good answer, but I think it's actually misinformed. Based on the article you linked in your answer to the other question, only the corners stick up above the atmosphere. The center of each side ought to be survivable, although I haven't done the math to see how it compares to Everest and other real-world mountains. $\endgroup$ – Bobson Jan 16 '15 at 19:03
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    $\begingroup$ @Bobson You're right, the corners are sticking completely out the atmosphere. You can picture this as a sphere superimposed onto a cube (the sphere would take on a little of the cube shape). The edges of the cube may be covered with a thin atmosphere. Quite enough isolation for divergent evolution (just look at the galapagos). $\endgroup$ – Samuel Jan 16 '15 at 19:20
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    $\begingroup$ @Bobson Please see included link supporting the idea that the edges would also not be in habitable atmosphere. $\endgroup$ – Samuel Jan 16 '15 at 23:29
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    $\begingroup$ Your link to AskAstro is dead. Try curious.astro.cornell.edu/40-our-solar-system/the-earth/… $\endgroup$ – user53364 Nov 30 '18 at 0:57
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Assuming you can build those huge mountains on a planet without melted mantle. (Because it would not be possible on a planet with melted mantle - mountain material would melt under own weight, and sunk into crust). Planet needs to be manufactured that way.

My assumption for "Earth-like" is: planet has enough water to cover about 70% of the livable surface. There will be some irregularities (not a perfectly laser-manufactured cube), but irregularities will be small - hills here, islands there, to make planet more interesting.

Edit: Apparently it would take a bit more water than I expected to submerge the ridges. If you add enough water to submerge ridges, my answer is correct. If not, then it is not. Pick what you want.

it will still make little difference. Yes, your planet would have 8 huge peaks, out into stratosphere, or even out into space. Yes, there would be huge long ridges, affecting the winds.

But that ridge will have also deep valley between peaks, and people can walk around from one "side" of the cube to another in the middle between peaks. Over high ridge, or over sea - depending of how much water your planet has.

Gravity will be weird, because even if surface is straight, gravity rounds down. So walking toward the corner peak, it will gradually become steeper and steeper, becoming 45% close to ridge.

With enough water, these ridges would be partially submerged and allow travel between sides. With less water, they would be just tall mountains (but not as tall and corners of the cube). I don't have time to calculate, but my gut feeling is that middle of the ridge would be below average distance to planet's center ("sea level").

Yes, some parts of science will be easier to research. Rocket sled launcher would be easier to build, so space exploration will be bit easier. But if you ignore difference in climate caused by huge mountains, and different topography of the ocean currents, there would be very little difference, if cube was made with earth proportion of lands and waters on the surface.

To get more different climate you may tweak rotation axis, and tilt relative to ecliptic.

  • If axis goes through mountain peak (corners), all sides have exactly same climate, with another mountain ridge around equator (best site for rocked sled launch).
  • If axis goes through center of sides (faces), you have two "polar sides" and 4 sides with same climate.

Sides still could have climate changes, depending on the tilt. But those differences in climate would be cause by tilt, not by planet having the shape of a cube.

So result will depend on how much water you have on such planet. Add enough water, and you can travel easily from side to side. Make planet dry, and travel between sides is over stratospheric mountain ranges. They will be smooth, no glaciers to scar them.

Seems that planet shaped as cube creates very little livable area. Seems that ringworld gives you more living space for same material. And if you want to divide civilizations, you can always add a ridge.

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  • $\begingroup$ A cube's edges are the same altitude as its corners. Why do you say there would be a "deep valley between the peaks"? $\endgroup$ – Samuel Jan 16 '15 at 19:14
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    $\begingroup$ Altitude of a peak is distance from cube center (center of gravity). Peaks are obviously much farther from center than middle of the edge, which is still farther from center than middle of the side (where deep ocean would be). $\endgroup$ – Peter M. - stands for Monica Jan 16 '15 at 19:19
  • $\begingroup$ Yeah, I suppose that's close to the definition of altitude we use on a spherical Earth. The peak itself is 1.4 times further from the center than the middle of the edge, my point is there is a straight line from peak to peak. It'd be a strange landscape to traverse. $\endgroup$ – Samuel Jan 16 '15 at 19:25
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    $\begingroup$ @PeterMasiar the distance to the core at the edges would be over 40 percent higher. Even if we assume the builders cut some corners, I totally would, the edges would have to be too high to survive. Also nobody would build a cube planet with melted mantle. The reasons Earth has a molten core are because of heat from radioactive decay and the energy trapped when the planet "fell together". Neither of those applies to artificial constructs. Higher pressure would still make the core hotter, but the same pressure would also increase the melting point in, I think, roughly the same ratio. $\endgroup$ – Ville Niemi Jan 16 '15 at 21:16
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    $\begingroup$ @PeterMasiar "because material would melt under own weight, and sunk into crust, which is just 20-50 km thick layer over melted mantle" $\endgroup$ – Ville Niemi Jan 16 '15 at 21:46
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The answers to date presume this is a cube of (roughly) uniform composition.

But it's clearly an engineered world, so it will be built to work more effectively.

Imagine it's hollow. Six huge squares. But, need gravity. You can have hyperdense material in a thick circle inscribed on each face. The corners are left light and mostly decorated without living geological processes.

The dense plates require less total mass than a solid sphere for the same surface gravity since you are very near to all of it. It will fall off rapidly as you rise off the surface since the distance squared is measured from 100 km underground, not 4000 km to the center.

And it's hollow!

The amazing stuff it's made of is seemimgly indestructible and hyperdense. The skin forming the corners is very thin, like a couple meters tapering to 1 cm at the point, plus some thicker ribs. The face features a lens shaped gravatus plate a couple hundred km in thickness, somewhat concave (deeper at the circumference) to keep the gravity normal to the flat face.

Leaving the edge of the gravatas plate to continue to the edge of the face will look flat, but feel like a rise that quickly goes to near vertical, since all the gravity is behind you.

There are access hatches and maintainance corridors beneith that some residents may find, even corridors to connect the faces. In the rock below the topsoil but above the gravatas plates would be machines. It "gardens" from time to time to undo erosion and just to randomly rework the habitat. Stores of normal matter and a moon's worth of minerals are stored in the hollow, so it can throw up mountains and add bedrock.


Let's get crazy now: the sun does not follow a constant axis, which keeps some faces as arctic. The sun track shifts to give everyone daylight. It would be hard to podehole the cube and move the axis of rotation around, so make the orbit interesting instead. Put the cube in orbit around a neutron star, and that has a companion star (the sun) with the orbital plane 90° relative to that. And the cube rotation axis (through the corners) is orthogonal to both of those. Hmm, that doesn't work at short enough time scales (weeks, not years). So, give it 2 suns, 90° apart as seen from the cube. One is centered on the northern 3 faces and invisible to the southern, and vice versa. I'll see about drawing some sketches later. (See followup question exploring this idea)

The K-II civilization that built it would stock it with interesting life, just as we would fill a garden pond or terrarium. If that civilization still exists, they would be watching.

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  • $\begingroup$ "It will fall off rapidly as you rise off the surface since the distance squared is measured from 100 km underground, not 4000 km to the center." Maybe my schooling was assuming a round planet, but center of gravity doesn't change just because the planet is hollow. $\endgroup$ – Wazoople Nov 30 '18 at 1:32
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It is doubtful whether life 'as we know it' could develop on such a planet. To start with there could be no erosion of the surface, because this would destroy the integrity of the cube. Therefore no soil. Or if gravity was (as suggested) perpendicular to the surface, the pull of gravity on the corners would be in two directions at once, both parallel with the surface. A new Newton would need to be invented for this. If indeed the gravity was 'normal' ie towards the cube centre, then four, or six, different worlds might develop, starting at different times and going in quite different directions, evolutionarily speaking. Alternatively, each face of the cube could have its own God (or Gods) who arranged things to his, her, or their wishes. Whether each of the Gods would be omniscient or omnipresent is a question for later.

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Simple answer? Any way you want it to.

There've been a wide variety of civilizations on Earth. Any of those, for example. And that's not even getting into whether or not you've evolved humans. You could evolve any type of plant or animal, and get a wide variety of civilizations.

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