5
$\begingroup$

The city of Evermill

Tens of millennia ago, a magician tried to reverse gravity in a 10km radius sphere around him for a dare. He succeeded, but unfortunately, the effect was permanent - earth, houses and hapless cows were suddenly inverted, eventually coming to rest as a lumpy dome floating in the air with a hemispherical depression beneath. The floating dome is buoyant, like an iceberg, and likewise free to rotate.

Of particular interest to the city's eventual inhabitants was the edge - the local flip in gravity means that a flywheel placed on the edge would rotate forever, getting energy for free (see the blue bar in the diagram): Evermill

The presence of free energy is noticed and exploited by the inhabitants, leading to a build-up of heavy industry: mills, blacksmiths, the like. Technology advances much more rapidly than it would otherwise. However, an industrial revolution - adjacent event has not yet occurred.

The inhabitants of this city would likely think up a way to get through the middle of the sphere. Just jumping into the anti-gravity field would make you fall a kilometer up and likely perish, but it would be possible to carefully 'float' along the edge if you balanced the up/down pull carefully. You could build a tower arbitrarily high there, since higher stories would not need to support the lower ones.

  • The inhabitants have not discovered steam power.
  • Among the general population, knowledge of magic is limited to very simple spells - conjuring flame, altering oneself to look like a donkey etc. The fact that gravity has been inverted is no more remarkable/artificial-looking than the existence of a mountain.
  • Pretty much the entire edge of the sphere is populated, though some parts (near water, etc.) are denser than others. Transporting people and goods through the middle would be an obvious thing for the inhabitants to want to do.
$\endgroup$
10
  • 1
    $\begingroup$ Why do they need to circle around to get from one side to another? Don't they have roads / streets crossing the city from north to south and east to west? This urban planning feature dates back to the Roman Empire $\endgroup$ Jul 8 at 11:45
  • 1
    $\begingroup$ I don't understand the question: What do the inhabitants need to do? Have fast transportation at the edge or do they need to travel in and out of the sphere? Also do they live in or outside of the sphere, or both? Is 10km the radius or the diameter of the sphere? $\endgroup$
    – Mr Puh
    Jul 8 at 11:55
  • $\begingroup$ See edits. There are normal roads and streets, but I want to ask specifically about how they deal with the boundary - it seems unlikely that people would just stop there if it was a densely populated place $\endgroup$ Jul 8 at 12:05
  • 1
    $\begingroup$ Since you have both magic and perpetual motion, normally-impossible solutions are merely mildly implausible...and selling plausibility is the job of the writer. Human-powered wings, edge-skimming cable-cars, crazy-upside-down rope bridges, magic-crystal-tubes, teleportation, etc. $\endgroup$
    – user535733
    Jul 8 at 14:11
  • 1
    $\begingroup$ Uhm, why do they need to go in sideways? They could just, you know, dig down from above and close the sideway entrances with walls. You would even have a self defense mechanism: just drop something at the edge, it will go up and fall down in front of the sphere as long as you can push it juuuuust slightly forward / propell it. $\endgroup$
    – clockw0rk
    Jul 8 at 22:50

10 Answers 10

5
$\begingroup$

We can choose to assume the earth-dome above is stable. It's not clear to me that it would be, but we can take it as given. Actually, we could also pretend it isn't stable and slides/spins/crumbles away. In either case, a possible solution for several problems is to

build a geodesic dome along the boundary

Geodesic dome

(or whatever part of the boundary is not taken up by the earth-dome, anyway.)

Let's break this into two parts. First, we'll ask what it would take to build this. Then we'll ask what it gives us.

What would it take to make it?

Not much.

Normally, a geodesic dome needs to support its own weight all the way down, and would require all the engineering that would go with that. But Evermill's gravity-boundary gives us a unique situation: if the dome would begin to collapse, the parts of it that are pulled into the sphere of inverted gravity are immediately being pushed back up by their own weight.

If it were built of rigid members, each of them that lies along the boundary would be pulled down and pulled up simultaneously--applying the torsional effect that will drive your free-energy flywheels--but also effectively giving each such member neutral buoyancy. And, in absence of external forces, they would tend to find that balance--in falling, more of their weight would lie in the inverse-gravity zone; in rising, the opposite.

But we don't even need rigid members. We can build the dome out of rope.

  1. Consider a circular rope, running all the way around the boundary, at about 45 degrees up from the ground. If it can't stretch itself wider, then it can't simply fall down on the outside--it's not wide enough. Maybe it would fall down one side, pulling the other side up?
  2. Well, then, anchor it with vertical ropes all the way around. If one side would come down, the other side must come up; but it can't because it's anchored. But wait...isn't the horizontal loop now bearing the weight of all the vertical ropes?
  3. Nope. Or not for long, anyway. If the ropes were cut properly, to fit the distance along the edge of the boundary, they'll also get pushed up as soon as they begin to sag, and find a position of neutral buoyancy.
  4. Since every part of this construction is supporting its own weight by straddling the boundary, you can add as many loops and verticals as you want...and the more mass you add, the more stable it becomes against the addition of the extra mass of (say) a person climbing up or down it, or any system of pulleys, or slides, or zip lines, or whatever transportation we'll eventually affix to it.
  5. What we have now isn't really even a "geodesic" dome...it's just lines of longitude and latitude. Normally, this would be problematic, even for a stucture with rigid members...without triangles in the structure, the dome would be vulnerable to collapse by twisting sideways one way or they other. But, as we've already established, this dome simply can't collapse. And having horizontal ropes (or rigid members, up to you) will be advantageous, as we'll soon see...

But there you have it. Technology required: Rope. Or wooden beams. And the ability to cut them at specified lengths. Method of construction is left as an exercise to the reader, but once you've got one rope to the earth dome, the second should be easier, etc.

What does it give us?

  • First and foremost, it gives us easy access to the underside of the earth dome. You can imagine any kind of stairs, slides, firepoles, flywheel-powered elevators you like: the dome gives you a place to anchor them. If rope is too flimsy to hold your transport system rigid, upgrade the required parts of the dome to use rigid members. To go up, passengers take the inside of the dome. To go down, they take the outside.
  • It also gives us a place to anchor more free-energy flywheels. If you build a circle of mills around the base of the gravity-boundary, that's a fair start...but there's so much more free energy to gain from utilizing as much of the open boundary area as possible. With your pseudo-geodesic dome in place, you can install spinning flywheels on every horizontal member that isn't occupied with transport systems or other usage. Chains or ropes can be routed up the vertical members to transmit power. (Mechanical transmission of power isn't the most efficient, but whatever you get is still free energy...)
  • Finally, this gives us a way to anchor the earth-dome, if we'd rather it not rotate freely. I don't know what your plans are for it and what aesthetics you envisioned for Evermill, but at least on the practical side of things, maybe your commuters would like to have a reliable way to get to the same underdome-address every day.
$\endgroup$
7
$\begingroup$

Scale up the infinite-power flywheel into a Ferris wheel that spans the gap; passengers now provide power to the city when they enter or exit. Passengers should be lying down and buckled in, for safety during the flip; carriages should be well-padded. If the gap is too large for a Ferris wheel, build ramps up to the boarding-height on both sides, keeping in mind that counterweights crossing the border can reduce strain on the support structures for the ramp.

$\endgroup$
2
  • $\begingroup$ Very nice first post on worldbuilding Vivian. I'm glad you thought of that, in retrospect a Ferris wheel seems the obvious choice - "commute to work in the upside-down city - it's fun". $\endgroup$ Jul 8 at 23:11
  • $\begingroup$ The Ferris wheel doesn't even need to be a wheel. A long chain with cabins or seats spaced at regular intervals will do nicely. Now, you probably do want a smaller wheel at each end that meshes with the mainline and then slows down near the surface, or at least one that reconnects to the mainline in the opposite direction. Not that a 1km ride at paternoster speeds would be too slow (do provide seats), but if someone misses their exit, they'd have to take two more trips. Inside the ticketed area, so no triple fare either. $\endgroup$ Jul 10 at 5:13
4
$\begingroup$

First problem is lava. After 10 km of the continental plate has been removed, lava appears at the bottom. This molten rock moves up and up in a field of reverse gravity with standard acceleration until it reaches normal gravity 20 km later. You can get a nice sub orbital fire fountain. In short - how is it possible that someone on this planet is still alive in the constant rain of lava?

OK. lets say that there is much thicker continental plate or core of planet is not molten(need find how to generate magnetic field to not be burned by sun, but...magic?) Possible travel solutions:

  • gliders - can drop glider to sphere and glide to other side of sphere (and with right trajectory even to other side of planet)
  • big flying creatures like dragons can fly there.
  • magic - fly or levitation
  • magically enchanted ropes to make bridge (10km ropes are hard to make)

Sphere shall be not static. It will be nice if it shrunk a little with any energy taken out of it. Maybe it take 500 years to drop from 10km to 9km radius but then "War of Sphere" can start and so another one and another...

$\endgroup$
2
  • 1
    $\begingroup$ "need find how to generate magnetic field to not be burned by sun, but...magic?" – this is a fantasy setting, the solar wind doesn't have to be a thing. $\endgroup$
    – Vivian
    Jul 8 at 22:23
  • $\begingroup$ Rock is molten 10km below Earth's surface, but if you chucked out a 10km sphere from the ground, the remaining rock wouldn't stay molten for long - though it is a good idea for the wizard to stay really far away from the sphere (or better, don some powerful fire resistance magic) while it's still stabilizing. I would be worried about some juicy weather though, if the magical gravity includes air and fog - cold air falls, spills into the sphere, falls up again, spills out, repeat. Permanent tornado, sideways. Maybe faster. A 1km drop is just tall enough to fit a proper cloud in the middle. $\endgroup$ Jul 10 at 5:44
3
$\begingroup$

Pulley systems / Cable cars

If they have mills, they know about pulleys and gears. They have a flywheel that generates infinite energy and is perpetually moving. They can connect this flywheel to a pulley and gear system to continuously transfer material (and even people) to outside the boundary

It would be a significant engineering project to construct the first stations both at the boundary and off the boundary, but once this is sorted, additional stations could be constructed with more ease

$\endgroup$
3
$\begingroup$

Travel along the edge

They could travel along the edge. E.g. like so: Assuming they have wheels they could create vehicles that carry a large fan, similar to a windmill. This windmill the could lower to a 90° angle towards the sphere and use the propulsion to move forwards. Its a risky business and you would need to drive carefully to not fall into the sphere. Boundaries need to be static for this and well marked with streets e.g.

enter image description here

Travel in and out of the sphere

You could travel in and out of the sphere by using artificial mountains where "Ground" and "Ceiling" come close naturally already (left). Or they could put long "bridges" (right) that balance out and allow to drive in an outside.

enter image description here

$\endgroup$
1
$\begingroup$

Stay in the sphere

There is no reason given why Evermill would have to extend beyond the sphere. While there would be problems, they should be solvable with the technology available:

Water could be obtained through a canal, which would empty out into the sphere, and flow down in a waterfall into a reservoir

Light could be provided by candles and all the other ways that people used to make light. Or, more exotically, the people of Evermill could have learned to live without light and vision

Leaving the sphere could be a challenge. One simple yet poor solution could be cushioned tunnels, so that people could simply walk out of the sphere and fall onto the roof of the tunnel. A more magical solution could be a room hanging on a hinge, where a magic user could slowly flip around, allowing the users to safely turn their gravity around, before entering/leaving the sphere with a bit of extra magic to keep them grounded. Both methods could be used, with the room being a service accessible only to those with money to spare, and the tunnels being used by the average guy

$\endgroup$
0
$\begingroup$

To enter the sphere, you can use the same principle that powers your flywheel. Have a nice comfy chair inside a rotating cylinder centered on the boundary. When a passenger sits in the chair, release some kind of locking mechanism (I'm imagining a cotter-pin, but you could potentially have a bar that slides into place on the opposite side when pushed out of the first side) and the weight of the person will rotate the otherwise empty chamber so that the chair moves downward -- and toward the transition point. Once the chair crosses the boundary, momentum will make it want to continue in that direction, and then the flipped gravity will make it want to continue rotating until the passenger is right-side-up in the inverted gravity. Just put a stopper and/or brake in there, maybe a hand-crank so they can add some torque themselves if needed, maybe some comfort & safety features like seatbelts, shock absorbers, etc...

enter image description here

Note that this doesn't resolve altitude difference (unless it's really big), but if stairs don't work for you then you could take advantage of the fact that the border of your anti-gravity sphere is curved. There should be an equilibrium point along the border (yellow), so you could build towers (purple) on either side, and have pulleys (green) mounted on blocks (blue) that can slide up and down between them. As you pull the passenger car left and right, it will travel up and down along the equilibrium boundary. If your people are particularly good with geometry, then it would be more efficient to do this along two axes simultaneously.

enter image description here

$\endgroup$
0
$\begingroup$

you are missing the point of gravity, gravity is a geometrical property, there is gravity only because we are in a sphere, gravity would behave differently in the photo you describe I suppose, just ignore physics and make up weird rules of your own, if you try to not ignore physics you will end up doing it wrong most likely. Don't mean to be rude, I meant to say: you have a lot of leeway to creating your own idea of how they commute without incorporating the need for the villagers to use magic. Saying something like: "they commute like: ..., because that's how it works in this gravitational field", should be fine

$\endgroup$
1
  • 2
    $\begingroup$ Welcome to the site Daniel. Perhaps you didn't notice the magic tag, and you would be correct in saying at this point "but it didn't have a magic tag". The question should probably be re-tagged to reflect the magic context in fairness. We invite you to take our tour, and refer to the help center as and when you have time for guidance as to our ways. Enjoy the site. When you have enough reputation you'll then be able to comment under the OP's post to suggest edits (50), or edit other's posts yourself (100). $\endgroup$ Jul 8 at 21:46
0
$\begingroup$

Man-lifting kites

In ancient China and Japan, these often seemed more a means of execution than travel; nonetheless, the technology was progressively refined. Given the motivation for travel here, and the mechanical advantage of being able to lower the convicted "explorer" to the ground inside, it seems like this could work quite well. Provided you have a few times more prisoners outside the dome than you need to have inside it.

Never mind -- just JUMP already!

There was too much rope in the last answer unless you have really good weavers. So forget the parachute! For a 10 km radius sphere, maybe 25 degree arc, there's maybe (1 - cos 25 degrees)*10 km = 0.9 km horizontal displacement between the place you enter and the place you leave. If you run into that at 10 km per hour, it's going to take (60 min/1 h)(1 h/10 km)(0.9 km) = 5.4 minutes to move, horizontally, to any point where you can touch the ground. Vertically, you know where you'll be - the sphere. Vertically you'll move at (sin 25 degrees)*10 km = 4.2 km in that 5 minutes, so your overall speed will be 52 miles an hour. But that's fastest at the start, where you're falling straight down, and slower near the end, as your horizontal momentum has been lost to some amount of air resistance. You'll definitely be rolling when you hit and hopefully you won't break anything important. Or you can skip the run shot and hope you eventually drift far enough to reach the ground, without getting torn apart by the spinning effect of the edge gravity in the meanwhile.

$\endgroup$
0
$\begingroup$

It would seem to me that the solution is not to go down, but to go UP (which would be 'down' for them).

If the residents dug down, according to their gravity, they would dig through their 'land' and end up on the TOP of the sphere, relative to the rest of the world. Given that they are industrialized, and technologically literate, surely they would have developed an airplane that would fly them in regular gravity and 'normal' atmosphere down to the surface of the earth. Wen they wanted to return, they would fly back up to their 'hole' and then climb back up to their surface.

I suppose eventually they would put an elevator in the hole, to make life easier for them. Going DOWN, err, rather, UP.

$\endgroup$
2
  • $\begingroup$ nice idea, but we're talking 5km of rock here. I wouldn't be the one to touch the ladder. $\endgroup$ Jul 11 at 9:13
  • $\begingroup$ @John Dvorak If magic can reverse gravity, 5 km. of rock should be no problem. Going DOWN the ladder should be easy. $\endgroup$ Jul 11 at 9:15

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.