2D beings with full digestive tract

Ideas about how a world with more than three spatial dimensions would work - what laws of physics would be needed, how things would be built, how people would do things and so on.

2D beings with full digestive tract

Postby quickfur » Fri Dec 16, 2011 5:24 am

I just realized today that actually 2D beings with a full digestive tract are possible. The creature will not fall apart because of its disconnectedness.

Yes, you heard me right. Here's how this is possible: just because two 2D objects are topologically disconnected, doesn't necessarily mean they can be physically separated. For example, two concentric circles are topologically separate, but the inner circle can never escape the outer circle. Now, connect the inner circle to the outer circle with a narrow joint, then cut the outer circle on either side of the joint. Now you have a circular arc with two small gaps leading into the space between the outer circle and the inner circle. Assuming the circles are rigid enough, the inner circle will never escape the outer circle, so the space between them serves as a food pipe with an entrance and an exit. Behold! A 2D being with a complete digestive tract!

Image

And yes, the 2D being is topologically two, but it's physically one since the two pieces are inseparable. Its two pieces can communicate with each other via signalling chemicals sent into the digestive tract where they can diffuse to the other piece. Of course, a pure circular layout introduces nitpicky problems such as the inner piece rotating relative to the outer piece, but that's not a problem if you pinch the digestive tract in the middle so that instead of a circular curve, you have a wavy-shape that keeps the inner piece always in the same relative orientation to the outer piece.

Image

Furthermore, there's no reason to stop with just two pieces. Once can easily imagine a network of interlocking pieces, that communicate with each other by sending/receiving signalling chemicals into/from the gaps in between. In fact, this kind of interlocking structure is probably required to have an organism at all, since in order to have cells with a porous membrane for communication, the membrane would have to be a similar kind of interlocking surface, otherwise it would just fall apart.

The nice thing about this kind of interlocking is that the shapes of the various pieces can be adjusted to control the maximum width of the gaps between them, thus allowing only particles of limited size to enter the channel. You can even have a shape-recognition mechanism: imagine a wall with a circular gap in the middle with a rotating disk trapped inside. A certain section of the disk is cut out with a jagged outline. Only when something of the right shape comes along can it mate with the cut disk to form a full disk, which can then rotate to the other side and then detach, releasing the shape to the other side of the wall. If the wrong shape comes along, it won't fit and the thing won't rotate, so the wrong shapes are blocked from crossing the barrier.

Image

This kind of mechanism can be used to form semi-permeable membranes, which are important to build a functional organism.
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Re: 2D beings with full digestive tract

Postby Secret » Sat Dec 17, 2011 1:21 pm

quickfur wrote:Image
Image

Although it won't fall apart, if we consider gravity, wouldn't the inner piece fall to the bottom of the empty space and clog up part of the passages (It still maintain its relative orientation with the outer piece)?

quickfur wrote:The nice thing about this kind of interlocking is that the shapes of the various pieces can be adjusted to control the maximum width of the gaps between them, thus allowing only particles of limited size to enter the channel. You can even have a shape-recognition mechanism: imagine a wall with a circular gap in the middle with a rotating disk trapped inside. A certain section of the disk is cut out with a jagged outline. Only when something of the right shape comes along can it mate with the cut disk to form a full disk, which can then rotate to the other side and then detach, releasing the shape to the other side of the wall. If the wrong shape comes along, it won't fit and the thing won't rotate, so the wrong shapes are blocked from crossing the barrier.

Image

This kind of mechanism can be used to form semi-permeable membranes, which are important to build a functional organism.

The issue of gravity also applies here, which will cause the disk to stay at the bottom of the slot.

In order for it to work as you describe, either there is something that lift the piece against gravity so that it won't get clogged in the empty space, or that gravity cannot exist along the direction of the 2D plane

Or did I mistaken something?
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Re: 2D beings with full digestive tract

Postby quickfur » Sat Dec 17, 2011 3:20 pm

Secret wrote:[...]
Although it won't fall apart, if we consider gravity, wouldn't the inner piece fall to the bottom of the empty space and clog up part of the passages (It still maintain its relative orientation with the outer piece)?

Hmm, you're right. If there's gravity, then this may not work so well. I guess I was thinking more in terms of Edwin A. Abbott's Flatland, where there's no real gravity in the sense of circular planets, but the plane is "horizontal".

As for a 2D world with gravity towards the center of a circular planet, the only way I can think of is that these 2D creatures would have to live in water, where the buoyancy will allow the pieces to counteract gravity to some extent. The water molecules in the gaps would exert some pressure to keep the pieces separate.

In any case, the presence of water molecules (or molecules of something) is necessary to prevent stagnation: there must be some brownian motion to keep the pieces moving relative to each other so that things like the shape-recognition "gates" will rotate, since if they are at rest, then nothing will happen even if the right shape came along.
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Re: 2D beings with full digestive tract

Postby Keiji » Sat Dec 17, 2011 3:52 pm

The body can carry their own water ;)
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Re: 2D beings with full digestive tract

Postby quickfur » Sat Dec 17, 2011 5:45 pm

Keiji wrote:The body can carry their own water ;)

Yes, but it wouldn't help with their digestive tract, though, 'cos as soon as they open their mouth all the fluid will be expelled due to the weight of the upper piece being pulled downwards by gravity. :( The only practical solution I can see is for them to be submerged in water.
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Re: 2D beings with full digestive tract

Postby Mrrl » Sat Dec 17, 2011 6:10 pm

Solution is fractal structure of parts that are glued together (probably by electrostatic) and can temporarily unglue to get pass to particles of food, blood and so on. Neural system should allow temporary disconnect of some nerves that cross digestive tract and blood vessels.
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Re: 2D beings with full digestive tract

Postby quickfur » Sat Dec 17, 2011 6:59 pm

Mrrl wrote:Solution is fractal structure of parts that are glued together (probably by electrostatic) and can temporarily unglue to get pass to particles of food, blood and so on. Neural system should allow temporary disconnect of some nerves that cross digestive tract and blood vessels.

Hmm, actually, I like this idea.

If we think of the 2D creature as a conglomeration of a very large number of units, perhaps large protein-like molecules with a star shape (a centroid region with long hair-like strands reaching outwards), connected to each other at the tips of the strands; then they can be "permeable" by allowing isolated particles to pass between them by temporarily opening up some of the strands and then closing them back, engulfing the particle in the process. The inner strands then open up and perhaps even pull the particle further into the structure, closing up again after the particle passes, like a zipper. So the 2D creature is sponge-like, and can soak up particles from outside without disintegrating. There will be some control mechanism to maintain a minimum number of connected strands, of course, so that the molecules are never completely "unzipped" from each other.

With this kind of structure, we can build quite complex organisms.

In terms of 2D itself, quite complex computational structures can be formed, for example, 2D block-shuffling puzzles are known to be at least NP-hard, which means you can encode a lot of complexity even just with static block shapes. With our sponge-like structure, even more complexity is representable. So complex life is definitely possible in 2D. The same can't be said of 1D, unless you're willing to stretch things by using interpenetrating harmonics of waves (I think Edwin A. Abbott implied this in his description of the square's dream). Besides, interaction in 1D is really boring, you only have two neighbours, max.
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Re: 2D beings with full digestive tract

Postby Pentoon » Sun Jan 01, 2012 10:29 am

I think of living material as being "sticky." Saliva, phlegm, blood, etc. have an adhesive quality. On the molecular level, 2D beings would exhibit this kind of molecular interlocking which we call "adhesion." And yes, they are gooshy, like flesh. I don't think of them as hard little blocks of material at all, except for bones, if they have them. But even the bones would be adhesively permeable to allow for growth and atrophy. Particles of food would pass through fleshly material by going through slightly less adhesive regions which would open for them, and then close up again after they went by.
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