h a l f b a k e r y"Not baked goods, Professor; baked bads!" -- The Tick
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A metal planet constructed in the form of a dodecahedron. Each of the twelve faces is isolated from the others by gravity. Each can have a different atmosphere—oxygen rich on one, ammonia rich on the next, etcetera. Primitive societies from across the galaxy are kept there, one to a face. Cities spring
up the in centers, which are covered with sufficient soil and water to support millions. The idea that the world is flat is common, for it is true. It is impossible for primitive beings to get from one face to the next, because the slope of each face becomes very steep near the edges, where the soil disappears, revealing slick metal at a steep incline. It is steep even though it is flat. And as the atmosphere dribbles to a near vacuum near the edges, it is impossible for anyone without a space suit to ever get there.
Dodecahedron
http://www.enchante...fs/Dodecahedron.GIF
[ldischler, Nov 21 2005]
3D and rotatable
http://jcrystal.com...POLYHEDRA/p_02.html
[2 fries shy of a happy meal, Nov 22 2005, last modified Nov 23 2005]
Flyby
http://bz.pair.com/fun/dodec.html
[~20K image] [bristolz, Nov 22 2005]
A strangely shaped world--
http://photojournal...v/jpeg/PIA07740.jpg
[ldischler, Nov 23 2005]
The Thwarted Pinapple
The_20Thwarted_20Pineapple
has been awarded to you. [dbmag9, Nov 26 2005]
//Yes, I just googled for dodecahedron shaped planet images and poof! there were dozens to choose from.//
http://phoenix.akas...iEarthPsychedel.gif
You say that bris, but look what I found on an unrelated search after looking at this idea... [Loris, Jan 25 2006]
[link]
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An exercise in space magic. Yeah, if we could do that, we could do that. But we can't. Not any of it. |
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Phillip Jose Farmer and Piers Anthony have both mined rich veins of science fiction with stories about such artificial worlds. I can only suggest you do the same. |
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Cute idea. I've played with the concept
of a disk-shaped planet. The disk would
be
thick enough to provide a reasonable
gravity at the centre and broad enough
that a creature able to exist comfortably
in the middle would be unlikely to be
abel to make it to the edge. |
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This idea, like that, might run into the
problem of finding materials with which
to build the planet that will not liquefy
at the points at which the crust is
thickest. |
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I don't have any problem with thought
experiments (providing that they're no
scientific theories). If Freeman Dyson
had
invented his sphere on the halfbakery I,
for one, would have had no problem
with that. This, assuming no SF writer
has come up with the concept of
atmospheric partition by shaping the
planet, I'd put in the same caregory. [+] |
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On a flat faced planet like this, how would the primitive forms of the laws of gravitation be described by the people living there? Would you feel like you're 'climbing up' a flat plane? |
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[ldischler], baring the number of zones, this is a direct copy of one of the Man/Kzin novelettes, spawned out of the Larry Niven universe. You're either unlucky or a plagarist. [-] |
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[Rayford] Yeah, I was thinking it might be like an unnoticible grade "up" a very high mountain. You only notice as the air pressure drops. |
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I am also wondering what the horizon would look like in a plane without the earth curve? |
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[normzone] What story? I've never heard of that. |
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That depends on where you are. In most places, the horizon would be entirely flat, but in five different views per plane it would appear to have a flat horizon and then suddenly drop off into a 72 degree angle. |
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It would be interesting to simulate coriolis effects within the oases of atmosphere on each face; whether there would be "leakage" into neighbouring regions etc.. |
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Even if metal, I think solar winds & debris would still rub the thing down to a ball over time. |
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[btw, nice image bristolz]
If it didn't crash into the planet, I'm thinking the moon would likely wobble orbit around the planet--with hilarious results. i.e. as water tides etc slosh towards the pointy parts. |
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//btw, nice image bristolz//
Yes! She does those so quickly and professionally that I’m always wondering if she found them somewhere. In reality though, the thickness of the atmosphere would be only about 1% of the diameter of the planet, so it would be barely visible in cross section. And, although I used the dodecahedron because it’s easy to visualize, there could be a vast number of these flatlands with the atmosphere still tapering away to zero at the edges. The planet would then look more like a golf ball, with the dimples flat and a bit larger than usual. You could have fourteen of them around the equator, and probably more than a hundred in all—circular rather than pentagonal.
The apparent slope at the edges would be a gentle 12 degrees, so the isolation would be mainly by the lack of atmosphere.
As for the solar wind rubbing the thing down, you only have to look at the primordial images of potato shaped asteroids and comets to know that it won't happen anytime soon! |
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I thought that mass was the determining factor for planets becoming round, and that an asteroid could be strangely shaped only because there is not a strong enough gravitational pull to make it spherical. |
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Yes, I just googled for dodecahedron shaped planet images and poof! there were dozens to choose from. |
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Everest is, I believe, reaching the peak height available given our crust rigidity and gravity. Higher mountains simply subsume more mantle and end up the same height.
Mars, at I think 0.6g, and with no tectonics, can support much taller mounts.
I think this is the main objection to such a plan. |
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This is true. The problems are subsidence and tectonics. So what you want is a very old planet, one circling a red dwarf star, a planet at least twice the age of the earth. So old that all of its radioactive elements have decayed, and the crust has grown all the way down to the core. So there aren’t any volcanoes or moving plates. You might as well use it for a zoo, because a planet that isn’t tectonically active can’t support life on its on for very long, since there are no volcanoes to recycle sedimentary rock into CO2. |
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We award you the Thwarted Pinapple. |
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and THAT...is what we know. |
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ID - have you read "Flatterland" by Ian Stewart? Think you
would enjoy it. I liked the idea and description of the
slick metal edges, tapering to a near vacuum + |
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//apparent slope at the edges would be a gentle 12 degrees// Would local mass concentrations at the vertices diminish that? It would depend on internal construction details. |
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The parts for which I think you would be up on mental cruelty charges are the fact that it would be easy to construct devices allowing water to run "uphill" (gravitational equipotentials at the edges of the faces would be above the surface as you approached the center), and likewise, a lake could only be round, at the center of the face, and would have a spherical surface. Imagine: the skyline of a town built around a 100-meter tall lake; the view of a sailboat on top of the lake; the view from the boat. That's bun-sufficient for me. The fact that all trees, buildings, and people would be leaning away from center is just extra glee. |
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One possible problem I see with this idea is the isolation of the different cultures becaus of the "icreasing steepness" near the edges. If the planetoid actualy had flat sides the gravity would be less near the edges, thereby making it easier for a person to fight against the steepness of the ground. Also the isolation of gasses depending on sides would dificult because unless each side was incredibly large the independent atmospheres would touch because of their thickness and curvature around the central gravitational point. |
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Also sounds reminicent Paul Hogan's Well of Souls novels |
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I've heard oa Cube-shaped planet discussion before. |
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It brought up most of your things you are discussing, oceans and whatnot. |
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I think it was in the appendix of a Pohl or Niven novel. |
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It's gravity that makes planets round, not plate tectonics, subsidence (although these are caused by gravity) solar wind, or impacts. There simply isn't Stuff hard enough to resist that mighty force. |
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I always thought gravity was perhaps the weakest force in our universe. Like the rest of nature, humans could defeat it...for a while. |
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I missed this the first time round, sorry for churning. Dodecahedra are the closest platonic polyhedra to spheres, so the biggest possible platonic polyhedron made of solid matter like metal or silica would be a dodecahedron. Granite can form a pyramid up to thirteen kilometres high under Earth gravity. This could be thought of as a spherical body with twenty such mountains on its surface, so in other words the maximum size of each edge, assuming Earth gravity, is equal to two times the square root of the sum of the squares of the height of the vertex above a sphere (one hundred and thirty-four hectometres) and the distance of the "base" of the pyramid formed by the vertex of the face of the dodecahedron from the midpoint of the edge. This can be worked out from the angle of the vertex, which in terms of the pentagonal face is one hundred and eight degrees, but the angle at which the three faces meet is the issue, and so far i don't know how to work that out. Also, the lower gravity means it could be higher anyway, and there's a meeting point where a near-dode becomes possible. There's also the question of materials available in sufficient quantity in this solar system, which probably amounts to iron, silicaceous stuff and carbonaceous stuff, i.e. asteroids. |
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The gravity would be low, but the atmosphere could be kept under domes on each face, meeting at the midpoints of the edges. |
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This can be done and each edge would be well over twenty-seven kilometres long. |
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//Dodecahedra are the closest platonic polyhedra to spheres// |
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I don't think the atmosphere would be spherical, due to the
non-spherical gravitational field. [Twist] says // If the
planetoid actualy had flat sides the gravity would be less
near the edges //, but my intuition says the opposite.
Anybody know how to computationally analyze the shape of
the gravitational field of an arbitrarily shaped mass? |
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"One thing I've found out, over the years, is that, anytime you think that you were the originator of some new idea, ' I was the first to do that, ' you'll find some old fellow who did it around 1895. Every darn time. " Edward Hamilton, 1904 - 1977, in "The Space Opera Renaissance", TOR Books, 2006 |
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Interesting idea for a SF world. Using the numbers from
wikipedia, the ratio between the midradius (midpoint of
the edges to the center) and the inscribed radius (mid-
side to center) is 1.1756. So if it's roughly earth-sized, say
inscribed radius of 3500 miles, the midradius is 4114
miles, 614 miles higher than the inscribed radius. That's
plenty of room for a mid-ocean depth (assuming you put a
puddle of water in the center) of several miles, plus
plenty of atmosphere on top which dwindles to vacuum
far short of the edge. (Not considering here the fact that,
as others have noted, the weird shape distorts the effects
of gravity, pulling ocean and atmosphere somewhat closer
to the edges and peaks). |
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Curious idea, but hell to build and keep stable. Reminds
me of another thought I once had, of a SF story where
someone is taken to an alien planet, which he quickly
determines to be no more than 1000 miles in radius but
with normal earth gravity, concluding with a question to
his hosts: so do you have artificial gravity, or did you
actually scour hundreds of solar systems to accumulate a
solid hunk of iridium and osmium just to do this? Nowhere
to go from there, since I can't think of any good reason
for anyone to make such a tiny planet (which actually
wouldn't hold its air as well as earth, as the gravity
strength diminishes much more rapidly as one goes up).
Yours at least has the point of accommodating multiple
ecologies in close proximity. |
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