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I am making a weird space that can not exist in the real world. It is made up of bubbles made from an indestructible material. The material is smooth as steel plate on the inside. One can go from one bubble to the next wherever they touch through a rounded hole of 40m in diameter. Those that go to bubbles on the same level and those going down are at the same level as each other. So water can flow throughout each level without having to go down. They are arranged as seen in the image. The large bubbles are 10km in diameter and the smaller ones have a 6km diameter. The colours in the image show a gradient in the arrangement. The red ones are at the highest elevation at 200m above the purple ones below. The lowest(purple) and the highest(red) are connected. Similar to an unfolded cylinder. Only gravity is kinda weird in that you keep walking downward if you walk from the 'lowest' directly to the 'highest'. It is like an infinite slope where you can keep walking down (or up) while passing by the same exact position every ~70km.

The inside surface of the bubbles is cooled to $4^0C$. A lighting installation is fitted in each of them to provide a normal earth day night cycle. And at every point it feels like you are just in a massive dome on earth. The Hoh river flows into this structure at the in sign and out of it at the out sign. These in and outlets are located around the Hoh Oxbow Campground: Forks, WA 98331, United States.

For my question.

If left alone for millennia and assuming that the in and outlet remain at least partially in the river. Would a forest develop inside of my structure? With beaver ponds filling up with sediment. Being abandoned by those beavers and develop a forest. Then later erode away again for a new century of beaver occupation. even if they start out empty.

random extra information

I have based the size of the holes on the with of ecological viaducts in the netherlands. There are 10 levels in total with each level dropping 20m. The Hoh river has an existing 60m drop over a linear distance of 13km. measured from the Hoh ox bow campground to 200' upstream. The structure is this large to be able to house the minimal viable breeding population of cougars. Seasons won't exist inside the structure. There will be a constant downward wind. It shouldn't be that strong due to the limited connectivity between the bubbles.

  • $\begingroup$ How would the rain get in to produce the rain forest? Are these bubbles air and water permeable? $\endgroup$
    – Willk
    Dec 19, 2021 at 20:52
  • $\begingroup$ @Willk no it would have to come from evaporation from the water carried in by the river. i can put in a sprinkler system if the evaporation is insufficient. to transform it from a forest to a rain-forest. $\endgroup$ Dec 19, 2021 at 21:09
  • $\begingroup$ I think we need more information. For instance: what do the connections between bubbles look like? Are they may tens of meters wide, even larger or tiny? If the bubbles are spherical and smooth it would be very hard for people or non-flying animals to climb to the openings, especially to those leading to higher bubbles. The sizes of the openings presumably also affect how much water vapour and other gases would spread between bubbles, which would affect the climate. $\endgroup$
    – EdvinW
    Dec 20, 2021 at 9:43
  • $\begingroup$ @EdvinW going up could be difficult so long as debris has not piled up on the sides. but one can always go down to reach the place where you wanted to go. and the holes have been specified now. $\endgroup$ Dec 20, 2021 at 13:16

1 Answer 1


You have a problem with floods

In your other question, you show a single river in a similar space, which runs downhill and does a loop. The river here (as well at the one from the other question) will likely scrub out large parts of your structure in a downright dangerous way.

Assuming that the river will periodically silt up and erode in idfferent ways through your structure, it will eventually open a channel blue-purple-red-orange-green-blue which leads back to itself. This channel is under the same effect as the eternal wind, and will accelerate. Less water leaves this loop than the river pours in, and the stream will build to a torrent, eventually dwarfing the supply. This will scrub out most of the inside of the relevant spheres, before spreading to those nearby and finding more routes (as the original river keeps supplying more water).

Having torn up the land in here (the river is now a torrent of thin mud), your river is constantly being heated by friction with the walls, but you have handwavium coolers attached.

Ultimately, you will reach equilibrium. This may be silt accumulating enough to stem the flow (until next time) or merely the water finding an exit. The latter would amke the space into a nightmarish thrill-ride.

Assuming the more peaceful version, you have a river which makes its way through a well-lit cave with intentionally surface-like conditions, and possibly a compressed-mud plug in each passage along a wall, stopping your breeze.

At that point, this is a straightforward cave with oddly bright lighting and cool temperatures ... until the next flood.

  • $\begingroup$ "At that point, this is a straightforward cave with oddly bright lighting and cool temperatures ... until the next flood." do you think that between these floods enough sediment (dry land) remains to allow for trees to sprout. There is enough light at least to let them grow. $\endgroup$ Dec 21, 2021 at 8:10
  • $\begingroup$ I have no idea. It depends on a complicated pattern of sediment deposition. But I think if the floods did jam things up, it's likely since you have a fairly conventional river. For extra fun, you could have some of your spheres (probably the 6km blue ones near the ends) fill with mud to above the exit-level, leaving you with tiny microbiomes. They'd probably be slightly pressurised and water-sealed. $\endgroup$
    – Anon
    Dec 22, 2021 at 5:11

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