Yes, I know the Earth isn’t flat. The question is whether a celestial body with a mass and density approaching that of Earth can have a shape like that of a stereotypical flat Earth, basically a large planet sized coin.
There are some celestial bodies with weird shapes, like ʻOumuamua (the extra solar asteroid from a few years ago) and some minor/dwarf planets have weird non spherical shapes, like Hebe. Beyond a certain size are all celestial bodies bound to be round?
(Although I have read some really large stars aren’t really sphere either).
If different shapes can be had, would a coin style Flat Earth even be possible?
Naturally forming, no. Beyond a certain mass, gravity overcomes any structure. And stars and planets are not perfect spheres, they are oblate spheroids, bulging at the equator. But close enough to a sphere for any practical purpose.
With a bunch of advanced technology and a desire to waste tons of resources in order to pull it off, maybe.
If someone made an Earth sized (mass) discworld and spun it on its axis (like an LP record) would it still collapse into a sphere? If so, are we talking a few years or a few million years or a few billion years?
Typically, any Earth-y type thing (i.e. made of rock) tends to compress itself into a sphere once it gets above roughly 600km in diameter. To put it in perspective, the Earth is about 12,000km in diameter, so that’s pretty far above the limit.
It is possible to have something above the 600km limit and not be spherical. For example, there is a trans-Neptunian dwarf planet called Haumea in our own solar system that appears to be an ellipsoid. The non-spherical shape is caused by Haumea’s rotation.
A very quickly rotating “Earth” of sorts could be spun out into a pizza shape, but it would have to spin very quickly. I’m not sure how you could get such a thing to form though. It wouldn’t hold an atmosphere over its surface so it would be more like a pizza-shaped rock ball and would definitely not resemble a flat water-covered Earth.
If you spun it up enough, it would become more and more oblate, but it would never be flat. I’m not sure how fast you’d have to spin it to make it more approximate a disc than a sphere, and it seems as though on the edges, it’s actually going to have more outward force from the spin than inward from gravity, and start falling apart.
In any case, it would not be habitable.
Isaac Arthur has a video on how you could make a flat Earth, if you really cared enough. Basically lots of active support.
An Earth-sized mass compressed into a flat disc would not have Earth’s surface gravity nor would be able to maintain a flat shape with extraordinary (supernatural) reinforcement. If spun to maintain a disc shape it would fly apart unless again restrained by some beyond material physics reinforcement. And of course, anyone on the spinning disc would experience rotation and the accompanying centrifugal, Coriolis, and Euler forces as they stood or moved, assuming they weren’t just bodily flung off of it. The sky would appear to be spinning as well, and all of this notwithstanding that things would continually be falling off the edge.
If you assume incredibly stiff materials reinforced by some kind of ‘force field’ to hold shape and keep air from spilling off the edges along with artificial gravity and nobody noticing that when the Sun goes below the horizon it just suddenly disappears instead of a gentle dimming in sinusoidal proportion, then you could conceive of a ‘Flat Earth.’ But at that point, why bother? If you have all of those technologies at your disposal, why not make a Möbius Earth, ora Klein Bottle Earth, or even an Escher Earth?
Still not as dumb as the Ringworld, though. At least it wouldn’t be a giant, indefensible structure visible from many parsecs, requiring reaction jets for stability and a defense system that turns the central star into an unstable flare emitter, exposing the surface to lethal charged particle radiation.
Ringworld would have worked if Niven had a bit more imagination, using stuff that already exists in Known Space.
Forget Scrith/Twing. Make the thing out of Stasis field-reinforced paper. Use reactionless thrusters for stability. Use conventional weapons for defense. As you note, using a weapon that vaporized thousands of acres of your own land when it fires is stupid.
It’s not like anyone can take it over or anything.
Other than being totally impossible in any electrochemical-bonded material, scrith isn’t really the problem. The ‘stasis field’ is actually a bigger problem insofar as it violates special relativity. The real problem is that the structure was build by Pak Protectors (presumably ones that left before Phssthpok but in a group different from those who settled the Earth) who surveyed all of the habitable worlds of Known Space and collected samples of their species (but for some reason didn’t genocide them despite their normal xenophobia), built the ring using some kind of technomagical transmutation technology that converted all matter in that star system into scrith, managed to spin it to a phenomenal speed using…something, then populate it with breeders but not bother to have any corrective mechanism to prevent them from mutating and adapting into ecological niches (the less said about Niven’s grasp on evolutionary science, the better), and all of this done with subluminal propulsion technology. It makes bible stories look plausible by comparison.
Sure they can. You create a bacteria that consumes all of the superconducting material, causing technological civilizations to collapse, then show up in the guise of an Arch Builder. Presto instant religion. Or just find the control center and use it to flare the star to sterilized whatever sections of the surface you want to occupy. Or take a chunk of neutronium and dump it on the surface to roll around, consuming everything. Or us a gravity polarizer to destabilize it. Or hug a quantum singularity (established to exist) up against the floor material until it eats its way through, venting all of the atmosphere to space. Or use a Slaver disintegrator to suppress the charge on the protons that make up scrith and cause it to break apart, flinging itself apart with phenomenal impulse. There are so many potentially world-destroying technologies and weapons in the Known Space narrative universe that an object like the Ringworld is hopelessly vulnerable to attack, and is something that the congenitally paranoid Pak Protectors would never consider building to house their breeder population. Smaller, more mobile rings, sure, or enclosed worldlets, or pretty much anything else besides a megastructure that can be seen from vast distance, accelerates at the pace of a starseed, and for protection only has a giant plasma weapon that is as much of a hazard to the Ring population as it is to the ostensible target.
Just to note that flat earthers don’t believe in gravity either. Our apparent gravity is due to some sort of density thing or they think the earth is accelerating at 1 g.
Yes I know how stupid this is. And before anyone says that no one believes this, and that they are all trolling, I know someone who does believe it because it is in the Bible.
They don’t claim that the earth is spinning - the problems you note are well above their level of comprehension.
Celestial objects which rotate very fast don’t turn into pizza-like flat disks; instead they start to deform and elongate, becoming rugby-ball shaped prolate spheroids like the planetoid Haumea. Pizza-like planets are just about impossible.
If Haumea was somehow accelerated even faster, it would split into two (or more) objects, which would orbit around each other as a planet/moon system.
You know, just because I chose not to write long posts, I am aware of these issues. In universe, stasis fields make more sense that Scrith. Scrith is supposed to be matter, and it just won’t work without blowing away hundreds of years of understanding of physics. A stasis field is a form of “subspace” as it were. It’s a boundary, not a thing in and of itself. In the hierarchy of impossible materials, GP hulls make more sense than scrith - they at least give lip service to the fact that the ordinary matter needs help to meet the strength requirements. (though the method of “reinforcing bonds” without affecting nearby matter and apparently with a power source that never needs a new battery, and is so small you can’t see it in a transparent hull is left as a fan wank for the reader.)
As for the actual use of stasis fields, Niven really never gave it enough thought. You definitely can’t have an off button that sticks through the field. That’s incredibly stupid, and impossible given the definition of what a stasis field actually is. And using a field as a shield is all well and good - until it comes time to know when to turn it off. How can the ship sense when the threat is gone, without removing the field? And if the threat has not been removed? Then you’re dead in the time it takes to remove and reestablish the field.
I said “take over” (invade and conquer). Obviously you can destroy the ring in any number of ways. In fact, any of your methods of destruction apply to every planet in Known Space as well. So what? Species (even Puppeteers, and Protectors) still live on planets.
And for the record, I’ve always said Protectors never build the ring. It makes no sense. The only way Niven could make it fit is by saying “you know that whole book about Protectors? It was a lie.” I have even asked if an author can be wrong about his own creation, and the answer has to be yes.
It isn’t’ the that the surface gravity is lower; in fact, for a thin disk of the mass and equatorial diameter of the Earth, the acceleration due to gravity would be higher because the mass is all essentially at the surface rather than being distributed through a sphere. What pulls large masses into a spheroid shape is just the fact that all of the mass above it is pushing down and will exceed the compressive stress. A thin disc of planetary size, which is structurally unstable under high edge loads anyway (tends to buckle like a long narrow column under load) will naturally collapse under its own mass.
Yeah, I know these people don’t really have a coherent grasp of physic but it is so easy to debunk these claims even ad a grade school science level of understanding before you ever get into calculations. Then again, a lot of people did and still do believe in ‘trickle-down economics’ which is basically the Tooth Fairy theory of macroecon, so Flat Earth theory isn’t quite as far from the mean belief system as it might seem.
No. I have been to Ringworld in the Celestia application, and it is a very long way from being visible from even a couple Pm, much less 15 and more times that far. And scrith and the shadow squares are made of radiation-absorbing material, so how you could say that it is visible from way the hell off, where its 2 AU diameter loses it completely in the light of the host star is baffling.
The implications of stasis fields as a structural material are way underexplored in Niven’s works. Personally, if I were writing the books, I’d have established from the outset that stasis fields are always convex and frictionless, which would make it very difficult to use them as tension members: That’d prevent most of the structural applications.
You may not be able to image the ring directly (although the presumably space-based telescopes of Known Space should be able to image to the limits of astrophysical noise and fundamental wavelength limits of whatever spectrum you are using) but at 1.6 million kilometers wide you’ll definitely see the star dim where the ring crosses it (if viewing edge on), and even if you aren’t in the ecliptic aspect, the reflected light from the approximately half of the inner ring surface that would be reflecting light toward the astronomer would create an aberration that would look like nothing but a large cosmic structure. We’ve actually identified planets at a distance of over 8000 pc from Sol using the transit method, and a Ringworld-sized structure certainly way more surface area occluding or reflecting visible light than even the largest super-Jovian planet.
You still have a substance of infinite stiffness. Unless it has infinite inertia, you can just built a communications device that can easily break special relativity. And if it does have infinite inertia…it gets even more interesting. Yeah, the statis field makes no sense. And that is really the problem with a lot of really high technology in science fiction; either it breaks physics as we know it, or you have to come up with some convoluted restrictions and qualifications for why it is still allowable within a physically sensible world. Since most technology artifacts and devices really just exist to create or solve a plot complication, it is best to not explain them in any detail at all.
I would suggest a rapid-spinning body would not look like a rugby ball so much as, perhaps better description, a jelly-filled donut without a hole or a hamburger bun.
Newton’s main accomplishment was to prove that a body’s gravitational pull was the integral of the matter and equal to the same matter densely concentrated at the center of gravity. If you are closer than some of that matter then the matter above you exerts negative force of gravity (pulls you away from the center). So basically, any matter that is further away from the center of gravity will tend to move closer to occupy any empty space (or if it can compress what’s below).
The exceptions
if the body is rigid enough to withstand the pressure of all the weight above it. There’s a reason most mountains are mostly pyramidal. And why they don’t get much higher than they do; beyond a certain height, weight and pressure, even on rock, will help lower them. Celestial bodies beyond a certain size tend to turn to spheres.
-if the body is spinning, the force of gravity can be offset by centrifugal force. hence rapidly spinning bodies could bulge at the equator. The trick is to acquire enough angular momentum, which would be a rarity in nature.
Think of a flat earth as a giant collection of landslides waiting to happen as the edges give way and settle over the center of gravity point, so first it looks like the Milky Way, a disk with a center bulge. Or the near-center parts bulge and flow under pressure.
Walking on the disk would be tricky too. Remember, you are attracted to the center of gravity, by the integral of the mass closer to the center of gravity than to you (minus the integral of the mass further from the center of gravity than from you) integrated over inverse square of distance of each particle. Thus, near the center you would walk upright; the further “up” the disk you get, the “steeper” it would seem, and near the extreme edge it would be like climbing a cliff (which is why this stuff would crumble into the center.
Now, maybe you could solve this issue by strategically planting neutronium in he disk so as to balance gravity so it’s “down” toward the disk under your feet all over. But whether that’s possible, and what magic material you come up with to stop the total neutronium from still collapsing into a ball by force of gravity…
I would guess that anything moving fast enough to want to flatten into a disk would fly apart, but I don’t know enough off the top of my head to do the maths.
