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Torus-Earth
- _quasimodo 13y ago"perhaps due to an advanced civilization with more aesthetics than sanity" :)
- throwaway_yy2Di 13y agoOf course. An advanced civilization with engineering sense wouldn't waste precious building materials on thousands of kilometers of planetary bedrock. (And that's to say nothing of that area/volume ratio, what that implies for radiative heat rejection!)
- sharpneli 13y agoAnd a termite might think that an advanced civilization would never spend tons of valuable vegetable matter for purely aesthetic reasons. It's all about the relative abilities. It's not completely unconcievable that some might transform planets the way we build funny houses, even if they are 'waste of precious building materials'.
- arethuza 13y agoI seem to recall that the Culture does regard planets as being rather wasteful of mass - much more efficient to build an O. NB I'm sure some Culture ships have probably built planets in idle moments - just for the hell of it.
- vidarh 13y agoIain M. Banks last Culture book has a "advanced civilization with more aesthetics than sanity" that had polished a moon much like a marble, that'd then been lowered down towards the planet it orbited while adjusting the orbital speed accordingly. They'd cut a trench around the entire planet, so that said moon were eventually orbiting below the surrounding planet surface.... One of the main civilizations in the book had then "inherited it" and used the moon as the headquarters of one of their military branches. It's fun to speculate just how bizarre results you could get if you had a civilization with enough resources to do planetary scale arts projects just for the heck of it...
- nitrogen 13y agoWouldn't the planet's atmosphere and oceans fall into the trench?
- CanSpice 13y agoYes, which is why you dig the trench deep enough to cover it over again, make it airtight, and pump out all of the atmosphere to make a vacuum torus inside the planet.
- drakeandrews 13y agoThere were either walls on either side of the trench, or the planet was a barren rock to begin with.
- josh-wrale 13y ago“Welcome to Magrathea, where we construct planets made to order.” (Source: The Hitchhiker’s Guide to the Galaxy)
- TehCorwiz 13y agoLarry Niven posited that a ring-shaped world would be roughly equivalent to a partial Dyson sphere. Although I seem to recall that his were only habitable on the inner surface. Suddenly I'm wondering how much of this applies to toroidal space stations.
- arethuza 13y agoI think Culture Orbitals are more elegant than Niven Rings as you don't need the shadow squares and wouldn't have the stability problems that a Ring has: http://en.wikipedia.org/wiki/Orbital_%28The_Culture%29 http://en.wikipedia.org/wiki/Orbital_%28The_Culture%29 For another take on mega-scale artificial worlds there is Alderson disk: http://en.wikipedia.org/wiki/Alderson_disk http://en.wikipedia.org/wiki/Alderson_disk
- utoku 13y agoUnfortunately they are not roughly equivalent. A solid shell or a ring around a star is not a Dyson sphere. The correct Dyson sphere is composed of many separate orbiting elements. A solid shell or semi-shell is unstable and is bound to collide with the star or just wander away. Yes, the Ringworld is unstable. This was one of Niven's mistakes and misunderstanding of Dyson spheres.
- anon4 13y agoLooking at the orbit of the moon which does figure-8s through the hole in the middle, isn't it conceivable that a sun can orbit that same way? Or rather, the two will orbit each other in a strange non-trivial way.
- iliis 13y agoIt would have to be a very small sun tough in order to fit trough the hole and not burn the planet to a crisp. So we arrived at the Discworld, where the elephants carrying the world sometimes have to lift their legs to let the sun pass. Such a small star would probably have to be kept burning artificially, as the smallest mass still allowing nuclear fusion is around 80 times the mass of Jupiter.
- dzuc 13y agoA few years ago I was wondering what this would look like and (less accurately) modeled it in 3d: http://farm3.staticflickr.com/2630/4085959963_8dc8217283_o.jpg http://farm3.staticflickr.com/2630/4085959963_8dc8217283_o.j...
- disputin 13y agoUseful for launches - a space cable car instead of a space elevator.
- dnautics 13y agoto be more specific, a funicular. A cable car would take energy to counteract the lift on one side; a funicular would be very nicely counterbalanced.
- cossatot 13y agoThis is cool! But the important question of what mantle convection, and therefore tectonics, looks like on a toroidal earth is not addressed... for the 'donut' earth where surface gravity varies by a factor of 3 on the surface, one could envision subductions systems, possibly double (two-slab) types, setting up at the northern and southern polar rings, while spreading systems would set up at the inner and outer equators. I have no idea what would happen to lighter, more differentiated arc rocks... would they gather in the middle of a two-sided subduction system, even though that is a gravitational high? Given the instability of these planets to perturbations, it's possible that sufficient redistribution of mass due to tectonics and crustal differentiation would be enough to rip them apart. Also, setting up a geodynamo would be tough...
- gliese1337 13y agoIt seems more likely that subduction would happen at the inner equator, and spreading systems at the outer. This is addressed briefly in the article- when plates move around the torus, they must compress to fit into the smaller diameter of the inner equator, and stretch out when moving towards the larger outer equator.
- deleted 13y ago[deleted]
- srl 13y ago(Lest I come across as a complete ass: this is a cool piece, of course.) At least the discussion of gravitation is wrong. Somewhat unintuitively, the gravitational force on the inner part of the torus (the surface closest to the center, on the plane of the axes) is 0. The pathological example is a hollow sphere of dense material. Outside the sphere, it "looks like" (if you just measure g) a solid planet. Inside the sphere, there is no gravitational field whatsoever, no matter how close you come to the surface. Surprisingly, this holds no matter how large the sphere is. Suppose you're sitting on the inside of the surface of the sphere, and you decrease the radius a bit. Now the gravitational pull /away/ from this surface decreases like r^-2, so you would expect the gravity towards the surface (which is essentially unchanged) to increase. The issue is that the amount of material opposite you - the surface area of a sphere, really - also increases like r^2. (This is informal, but the best I can do for an intuitive explanation.) Tough to find a good explanation of this online. http://physics.stackexchange.com/questions/364/gravity-on-a-doughnut-shaped-mobius-planet http://physics.stackexchange.com/questions/364/gravity-on-a-...
- Kutta 13y agoAre you taking into account the correction from centripetal force, though? Even in the case of the hollow sphere, if we spin it fast enough it'll work just like your standard spinning space station, on the inside surface (or at least on a band-like area of the inside). I find it difficult to believe that the author made such a glaring mistake, even after doing the simulations and all. Also, he says " the surface is an equipotential surface, so gravity (plus the centrifugal correction) is always perpendicular to it. " The spinning is the reason this ridiculous configuration is at least theoretically stable.
- srl 13y agoI'm not taking into account centripetal acceleration, but it is small in ordinary planets. In order for the planet to actually be a torus, it needs to be spinning extraordinarily quickly, precisely because gravity does not help maintain the torus shape. From my reading, the author's simulations presupposed what s/he believed the gravitational field is. (This is actually a reasonable thing to do, and I don't fault him for it.)
- aruggirello 13y agoIMHO the surface of such a planet should be nothing more than molten lava, as the outer parts of the torus are probably going to rotate much slower than the inner parts (much like the rings of Saturn do). This would not allow for any solid crust to form. I agree with srl: gravitation must get gradually closer to zero in the inner part, where the molten lava, not being pulled down by any gravity, continually explodes due to the pressure of the internal gases, forming a fuzzy ring of (cooling?) debris, a gradually spreading chaotic mix of rocks, the greater part going towards the torus' real centre of gravity, leaving underlying molten rock exposed to follow their fate later on - in short a crumbling effect that cannot be arrested. This rocky chaos may later start collapsing in the middle of the hole, forming the seed of the future planet. BTW any large enough asteroid impact would also spell doom to the whole torus planet and either wreak havoc, rip it apart (in interesting ways, depending on location and direction of the impact) or cause the central "hole" to collapse sooner, finally reducing the planet into a more spherical shape - enter the Torusmageddon :) Just my two cents.
- rcthompson 13y agoA torus is not a hollow sphere. The OP's article stated that the computed surface of the torus was an equipotential surface, meaning that the apparent gravitational force (a combination of actual gravity and centrifugal force) at every point on that surface is straight down into the ground. OP even calculates the strength of the apparent gravity at every point on and around the torus. Assuming the planet started out in this toroidal shape, it would be stable since the net force at every location is "straight down", so there would not be anywhere where pieces would just fly off into space.
- moron4hire 13y agoI think it is funny to note that the old style of video game map, a square area where walking over one edge makes you appear at the opposite edge, more closely maps to a toroid than a sphere.
- quarterto 13y ago> more closely maps to a toroid than a sphere It's the very definition of a torus, at least when we're talking about fundamental polygons[0]. [0]: http://en.wikipedia.org/wiki/Fundamental_polygon http://en.wikipedia.org/wiki/Fundamental_polygon
- moron4hire 13y agoYes, I just meant that, if you did wrap a square video game map into a torus, it would look kind of funny as the middle would get stretched and the top and bottom edges squashed. But it would certainly all be there, unlike a sphere that would need parts of the map cut out.
- johnwatson11218 13y agoNot sure if it was in the article or not but I think the Hairy Ball theorem from Topology would be important. Since earth is a sphere the wind can't blow all in the same direction. Some currents must oppose others. In a torus the wind could start blowing in one direction and stay that way forever.
- rtkwe 13y agoThat's not what the Hairy Ball Theorem (HBT) says, the HBT says that there must be a point on a sphere where a continuous vector field is zero. It doesn't say they can't be pointing in the same direction except that point.
- johnwatson11218 13y agothis link http://uncyclopedia.wikia.com/wiki/Hairy_ball_theorem http://uncyclopedia.wikia.com/wiki/Hairy_ball_theorem talks about the application to the torus. It states that it is possible to completely comb the hair on a doughnut. That is the point I was trying to make earlier. I think it does imply that the wind could start blowing in the same direction if we lived on a torus. I think it would be the same if we lived inside like in science fiction movies or if we lived on the surface with a normal atmosphere.
- valtron 13y agoI can't tell if you're being sarcastic... but if not, this is the first legitimate use of uncyclopedia as a source I've seen.
- pndmnm 13y agoIn fact, it does -- to demonstrate, assume otherwise and use the definition of continuity.
- rtkwe 13y agosigh To quote because topology is a pain: > "there is no nonvanishing continuous tangent vector field on even dimensional n-spheres. For the ordinary sphere, or 2‑sphere, if f is a continuous function that assigns a vector in R3 to every point p on a sphere such that f(p) is always tangent to the sphere at p, then there is at least one p such that f(p) = 0" Which means they can all blow in a continuous path except for at least one point, so the wind at every point but 2 could be blowing east on a sphere. http://en.wikipedia.org/wiki/Hairy_ball_theorem http://en.wikipedia.org/wiki/Hairy_ball_theorem
- NAFV_P 13y agoSounds more plausible than this tripe: http://en.wikipedia.org/wiki/Hollow_Earth http://en.wikipedia.org/wiki/Hollow_Earth Some idiots still believe it.
- roywiggins 13y agoThat was fun. If you like this sort of thing, "Heavy Planet"[1] is a good hard scifi book set on Mesklin, a fictional super-Earth which spins fast enough to make gravity significantly less at the equator. It's also a good adventure story, if you like 1950s scifi. [1] http://en.wikipedia.org/wiki/Mesklin http://en.wikipedia.org/wiki/Mesklin
- AlanSE 13y agoHow does this compare to Mission of Gravity? I've had that on my shelf and haven't got around to it yet. It's a very cool setting, and the author was writing it before we had all the research on the subject we have today. And he was correct thankfully!
- gliese1337 13y agoHe actually wasn't 100% correct. If you get the omnibus "Heavy Planet" edition (including a sequel novel "Starlight" and some short stories), it is explained in an appendix that Hal Clement's estimation of the gravitational field was somewhat off, resulting in erroneous values for the maximum field strength at the poles. Still, Hal Clement did a bang-up good job, and the error (or correction there of) doesn't negatively affect the story at all.
- debt 13y agoThis reminds of something I've seen earlier: what if the Earth had rings like Saturn? I'm more curious as to how this would affect us culturally; the effect a toroidal earth would have on our collective consciousness, how we treat each other, and our evolution. https://www.youtube.com/watch?v=UT2sQ7KIQ-E https://www.youtube.com/watch?v=UT2sQ7KIQ-E
- GhotiFish 13y agoif planets are effectively amorphous liquids with no surface tensions at planetary scales, then why would you see areas on the surface that experience different amounts of gravitation. The rock of the planet experiences that gravitation all the same as the surface of the rock, mass experiencing low gravitation must equilibrate with mass experiencing high gravitation. So what stops mass experiencing 0.65 units of gravity from displacing mass experiencing 0.3 units? You would think this would result in somewhat consistent gravity around the planet. This result is unexpected to me.
- AlanSE 13y agoI'm not sure if I understand entirely what you're asking, but I think it comes down to "planetary differentiation". It's the same process by which water floats on top of oil because of density. The heavy stuff floats to the bottom and the light stuff floats to the top. That process isn't 100% complete obviously, but that's because near the surface material strength matters a great deal. We still have mountains on Earth, which are clearly not behaving like a liquid. If it was behaving like a liquid, then you're right that the heavier parts would upturn the lighter parts and sink. But Earth still has density variations because the process isn't complete, and tectonic movement keeps rearranging it all.
- dredmorbius 13y agoFriction and timescales also matter. The Earth is highly plastic ... on geological timescales. The continents move, the Himalaya are rising at the rate of about 5 mm per year, and one theory of the post-Messinian flooding of the Mediterranean basin (https://en.wikipedia.org/wiki/Post-Messinian_flood_of_the_Mediterranean https://en.wikipedia.org/wiki/Post-Messinian_flood_of_the_Me...) is that a fragment of one of the colliding plates in the region broke off and sank into the lithosphere. The whole system is dynamic, and driven by both latent gravitational heat of formation and by radioactive decay (including postulated naturally occurring fission reactors within the outer core / inner mantel: http://www.nature.com/news/2008/080515/full/news.2008.822.html http://www.nature.com/news/2008/080515/full/news.2008.822.ht... -- a fission reactor near the surface was found in Gabon, within Africa, active about 1.7 billion years ago: https://en.wikipedia.org/wiki/Natural_nuclear_fission_reactor https://en.wikipedia.org/wiki/Natural_nuclear_fission_reacto...). But it's an interesting rock we crawl about.
- deleted 13y ago[deleted]
- dognotdog 13y agoI do wonder if something like this exists, now. I'm familiar with the Dyson ring and sphere, but I never thought of a torus. Even though after the sphere, it seems the most plausible 'mode.'