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I'm inspired by this question and was thinking that it is nigh impossible for sun, moon and star to exist in this world and even if they do, there is no way to sun and moon to orbit and create day-night cycles.

So i came upon a solution, how about a infinite tube world like this : Rendition of a tube world with alternating transparent and opaque sections

Here is my world :

  1. There is no end either side of the tube. It is infinite.

  2. Tube's surrounding walls are 6371 km thick and their geographical structure is just like earth.

If you started to dig at one point inside the tube first you will go through a solid crust, then a liquid mantle layer, then a solid outermost layer. if you go beyond this layer (beyond 6371 km) you will come out of the other side of the tube's wall travelling in reverse order of the layers.

  1. I have not decided the radius of the tube but it should be huge so that a large portion of the center remain empty like space and with negligible gravitation force.

  2. In this empty space are moon, stars, even planets, asteroid and lots of other stuff just floating around in either directions of the tube.

  3. When a star go supernova it destroy a large area of tube and hurled the debris in either direction. Some of these matter fall down on the surface again and rest create a debris cloud in the center.

  4. When this debris cloud gets enough matters either by other supernovas or some other ways they form stars and stuff.

  5. These stars and other material in the center space keeps running in either direction of the tube. (This can not be stationery otherwise they will just fall down to nearest surface of the tube due to gravity).

  6. These chaotic events could leads to a configuration of two binary stars revolving around one another with parallel to the tube.

  7. Thus above configuration can create a stable day night cycle on a small portion of the tube. When a sun comes near the surface it is day and whens it go away it is night until the other one comes around.

What are the possible flaws in this world if i wanted to follow real world physics (as close possibly) ? Could it work to create a possible earth like environment ?

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  • $\begingroup$ The tube world seems like a good solution until you modify it so that it's not a tube. You've made it so, once again, there can be no orbiting moon, no sun with day/night, and no stars. Why? $\endgroup$
    – Samuel
    Dec 5, 2015 at 19:10
  • $\begingroup$ @Samuel, Pardon me i don't understand. what you mean ? $\endgroup$
    – Deepak
    Dec 5, 2015 at 19:36
  • $\begingroup$ I think you may just be doing a coordinate system transform. You mention digging right through the core. What happens if, instead, you intentionally dig at an angle that misses the core. Where do you end up? $\endgroup$
    – Cort Ammon
    Dec 5, 2015 at 20:09
  • $\begingroup$ . . . I can't prove this, but I have to say, this sounds improbable. $\endgroup$
    – HDE 226868 ♦
    Dec 5, 2015 at 22:04
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    $\begingroup$ @JDługosz. For the sake of convenience lets assume that an advance alien race or an omnipotence entity created this universe as it is. Right now i want to focus on the question if this universe is stable in it current form or not. $\endgroup$
    – Deepak
    Dec 6, 2015 at 15:22

7 Answers 7

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It's not stable in its current form.

If you picture a cross section, it's a wrap-around video game screen and you can pan anywhere and make anything the center. The position of the hollow part and layers is arbitrary. That's interesting but not the point to follow.

There is no gravity holding it all together like the Earth's core. A hollow sphere will have no self-gravity felt inside it. So, digging out a rock it will not stick to the walls but float around.

So you describe a structure that's stratified in the manner caused by gravity with changing pressure and heat! But there's no pressure so your faux core will not have the right conditions, there is no mechanism to cause the stratification, so the material will get dug up and mix more uniformly over time.

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  • $\begingroup$ You are right. What if i abandon the idea of wraparound and make the tube outer layer fixed at a certain radius. An impregnable boundary with nothing outside of it. $\endgroup$
    – Deepak
    Dec 6, 2015 at 17:52
  • $\begingroup$ If you want to concentrate on the "inside" that makes sense. But boundaries cause problems. $\endgroup$
    – JDługosz
    Dec 6, 2015 at 20:10
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    $\begingroup$ Story-wise, having a "crystalline sphere" that's a tube can avoid the details of the hard border as something unknown to the characters. $\endgroup$
    – JDługosz
    Dec 6, 2015 at 20:13
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    $\begingroup$ Interesting, and exactly contrary to the matter arrangement that causes it. So it's unstable and the ground will fall up. $\endgroup$
    – JDługosz
    Dec 7, 2015 at 15:39
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    $\begingroup$ @PyRulez That only applies in a 3 dimensionally flat spacetime, the topology of the spacetime would make this all screwy. In order to figure out what is going on, you probably need to define a metric space too. $\endgroup$
    – Lex
    Jan 25, 2018 at 5:51
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I think you are going to end up with something sufficiently convoluted that you would be better off dropping "normal physics" entirely. There will be myriad problems... pretty much everything will stop working. Our physics is really not designed to handle infinite structures like you describe.

Let's talk diameter. You started with the suggestion of $6,371\;\text{km}$, the diameter of the Earth. In your edit, you clarified that you are not picky about the diameter, so let's fix it to something that works. You need supernovas right? A supernova emits $1.5\;\text{foe}$ ($=1.5 \cdot ( 10^{51}\;\text{erg}$ or $10^{44}\;\text{J})$) of energy. That's a lot of energy. Let's do a comparison. A supernova emits most of its radiation in about 1 second, so there's no time for cooling. We'll have to treat it as virtually instantaneous radiation energy. Let's see just how big the ring is if we want to see $100\;\frac{\text{W}}{\text{cm}^{2}}$ at the surface. With a little math we see the diameter of the tube needs to be about $7 \cdot 10^{18}\;\text{m}$ in diameter. That's right, not $6,371\;\text{km}$ in diameter, but $7,000,000,000,000,000\;\text{km}$ in diameter! So we don't have to write all those zeros, we'll call it $730\;\text{ly}$.

Why do I pick $100\;\frac{\text{W}}{\text{cm}^{2}}$? It wasn't an arbitrary number. As it turns out, that's right on par with the irradiance used by military lasers to shoot missiles out of the sky. That's right. If you were 730 light years away from the supernova, you'd feel like you were shot with a military anti-balistic missile defense laser!

Supernovae are bright!

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  • $\begingroup$ Thanx for the answer cort. 6371 is not diameter of the tube. It is the thickness of the tube. I have to edit my question and clarify it a little more. $\endgroup$
    – Deepak
    Dec 5, 2015 at 21:16
  • $\begingroup$ Ahh. I was making assumptions from the picture. However, does the idea of a tube thousands of light years in diameter cause you any grief for world building? Those sizes change a lot. For one thing, any 1m wide strip of land contains about 100 Jupiters worth of mass! $\endgroup$
    – Cort Ammon
    Dec 5, 2015 at 21:19
  • $\begingroup$ Not at all. I want it to be massive :D, go wild ! $\endgroup$
    – Deepak
    Dec 5, 2015 at 21:27
  • $\begingroup$ In that case, can you clarify my question on the original post: I'm trying to figure out the topology of your construction, especially when you don't dig at a perfectly right angle to the ground. $\endgroup$
    – Cort Ammon
    Dec 5, 2015 at 21:38
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    $\begingroup$ You are going to hit the core no matter at what angle you dig, because geographic layers like crust, mantle, and the core are concentric to the axis of tube like layer of onion. Ohh, I think you are again misunderstanding me due to the second image. That is not of the tube but of the earth. $\endgroup$
    – Deepak
    Dec 5, 2015 at 21:47
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As previously mentioned in both the comments and other answers, in our Universe this configuration is not stable and will collapse. However, if you're already world building, there's absolutely no reason you can't start with Universe Building.

I already answered a similar question to yours with this answer.

The results is something called a Khex Class Cosmos

enter image description here

It includes an energy source, energy sink, and materials in between the two.

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  • $\begingroup$ Thanx for the answer jim2B but i don't want to use any magic. $\endgroup$
    – Deepak
    Dec 7, 2015 at 10:57
  • $\begingroup$ "Any sufficiently advanced technology is indistinguishable from magic." Arthur C. Clarke And the set up that you want is not possible in our Universe regardless of technology levels. Since humans are finite creatures, by definition they can not build a structure that is infinite in any dimension. $\endgroup$
    – Jim2B
    Dec 7, 2015 at 12:50
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    $\begingroup$ @Deepak magic? If this configuration is taken, it would be nature of the proposed universe. It would be as magical as quarks. $\endgroup$
    – Theraot
    Aug 30, 2016 at 9:23
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Actually, I think I see a way it might work. You'll want to ask on physics.se to make sure.

Make the tube rotating. Fast. The centrifugal force will both stabilize the tube against, uhm, itself (geometry is weird in this universe) and will keep the people from falling off of it.

Now, the tube's gravity is actually inward towards the center (an infinite cylinder has gravity pointing towards the center). Suns and such can simply orbit this axis, and even move along it at constant z-axis velocity. From the tube, the stars will look like they're rotating really fast, but really they will be orbiting the central axis quite slowly; it is the tube that is spinning fastest.

This will probably only work with Newtonian Physics, since you would get frame dragging from the tube.

Again, you will want to ask on Physics to make sure I didn't mess something up.

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  • $\begingroup$ How can the tube rotate, as I noted on sdwawlcabdear's answer? $\endgroup$
    – JDługosz
    Dec 9, 2015 at 0:13
  • $\begingroup$ Could you explain the issue? If the entire tube is rotating, points opposite each other will stay opposite each other (so no rubbing). Basically, anything on the tube would be "attracted" to this outer circle, (if you hollowed a region around it, you could orbit it). $\endgroup$
    – PyRulez
    Dec 9, 2015 at 1:23
  • $\begingroup$ What's the distance from a point to the center of rotation? If you pass the point and keep going you reach it again! Go the other way, likewise. So what's the angular velocity and centripetal force? There is no self-consistent answer other than zero. $\endgroup$
    – JDługosz
    Dec 9, 2015 at 1:37
  • $\begingroup$ Imagine that you are on the world, and suddenly all the dirt disappears. You will continue moving towards the circle. When you hit the boundary, imagine that the entire circle is translated. You will be on the other side, aiming for another point on the circle. $\endgroup$
    – PyRulez
    Dec 9, 2015 at 1:40
  • $\begingroup$ What circle? What boundary are you referring to? $\endgroup$
    – JDługosz
    Dec 9, 2015 at 11:55
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Okay, so all gravity is pointed at the center of cylinder, I think. Therefore, people can't live on it. They would fall into the center.

If I'm wrong, and gravity goes towards the tube, that means that the moons and stuff can't "float around". They would fall into tube immediately.

One way around this is if the tube is completely filled with fluid in which humans float (so they float towards the tube). The other way is if the tube is charged attracting either humans or repelling stars and planets.

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  • $\begingroup$ Thanx for the answer PyRulez, you are right too but JDługosz explanation is better. $\endgroup$
    – Deepak
    Dec 7, 2015 at 11:00
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For day-night cycles : why not making your tube orbit and at a distance of it, place a wall of light, or just another infinite tube of light replacing the circle sun !

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  • $\begingroup$ Thanx Aiman but apparently my model have bigger problems then day-night cycles. $\endgroup$
    – Deepak
    Dec 7, 2015 at 11:01
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Make a wide Ring world.

See the book Ring World for a more full description. A very high strength outer shell is set spinning very quickly around a star, the centripetal force mimics gravity and keeps the shell taunt away from the sun, all pulls people along the inner surface toward the shell away from the sun. The shell must be mounted with thrusters to keep it centered. A cylinder is just an extended ring.

Some caveats a supper nova is huge and would obliterate the surface of the ring if it were close enough to receive sun light.

The ring world uses huge squares close to the sun to produce shadows and a day night cycle.

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  • $\begingroup$ But with the edges identified, what would the centripetal force end up doing? Is it even possible to rotate the walls or will it end up trying to go both directions at the same time? Remember this isn't a tube in space--it's a wrap-around closed dimension. $\endgroup$
    – JDługosz
    Dec 8, 2015 at 21:14
  • $\begingroup$ What do you mean an wrap-around closed dimension? How does having defined edges to the tube change what centripetal force does? $\endgroup$
    – sdrawkcabdear
    Dec 8, 2015 at 22:41
  • $\begingroup$ The position on the wall will be distance d from the axis, and also distance 2d+2w at the same time, and also -(d+2w) at the same time, etc. So how can it move with a velocity that depends on the distance from the axis? $\endgroup$
    – JDługosz
    Dec 9, 2015 at 0:10
  • $\begingroup$ What do I ean wrap-around? Reas the OP: if you dig through the wall you come out on the other side. Think classic video-game screen like Asteroids or PacMan. $\endgroup$
    – JDługosz
    Dec 9, 2015 at 0:11
  • $\begingroup$ please join at chat.stackexchange.com/rooms/32765/… $\endgroup$
    – JDługosz
    Dec 10, 2015 at 0:04

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