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Really big constructs/creatures
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You are currently reading a thread in /sci/ - Science & Math

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Is the main limit on these not the energy that can be delivered (since hydraulics and muscles seem volumetric rather than cross-sectional in terms of power) but the cross-sectional structural strength?

In which case, is there any way to make something that actually gains the strength necessary to move and support itself as it increases in size?
For example: It seems that putting holes in things is seen as a way of reducing the weight of things without interfering with its structural integrity. Would something simular to a Kleinan fractal (but with finite iterations) be able to work as a building block for supermassive structures under gravity on that basis?
Or am I misunderstanding the purpose of putting holes in things?
Bones need to be flexible to an extent.

But the actual limit, on Earth anyway, is due to the surface area to volume ratio problem.

Volume of blood/gases increases substantially compared to surface area of cardiovascular tissue when size increases.

Whales which are buoyant and don't need to support themselves are the upper limit because of this.
I dunno, getting oxygen into blood seems like it'd be the lesser issue than structural strength.
If one could survive having air mix directly into their blood, it'd go away altogether.
Although there's probably much more reasonable ways of handling it.
You misunderstand, it's the surface area that limits the amount of oxygen that can transfer from the blood into the rest of the body.

This pic should clarify what's going on.
Another thing you probably already know, but needs a mention, is that bone is actually living tissue and needs free flow of blood through it too.

Maybe there's a better whacky alien design to support weight and transport gasses and chemicals, but who the hell knows.
But arteries are inherently fractal.
If one only looks at the capillaries, the surfacearea/volume ratio doesn't change with size, because there's a roughly even distribution of capillaries throughout the volume and I see no reason why the capillaries would have to become larger as the creature becomes larger.
Although unless the arteries became four rather than two times as wide with each doubling in size, then the speed at which the blood was pumped would have to quadruple because the capillaries would be twice as far away and the volume of the capillaries would double in relation to the cross-sectional area of the arteries.
Makes me wonder how fast a whale's blood travels in comparison to a mouse's.
Yeah true, and definitely part of it.
The limitations of muscle in the heart as a pump is part of the upper limit as well.

I could see some gigantic alien creature with multiple hearts and lungs all through its body making sense.
The question is though, to quadruple the speed at which the blood travels, how much stronger does the heart have to be?
Maybe for a doubling in size and a quadrupling in blood speed each muscle cell has to work twice as hard, which would be four times as taxing on the structural integrity of the muscles.

As for lungs, I'm not sure whether they'd need the same strength increase that a heart does, which could mean one pair of lungs which distributes to all the hearts could be enough.
Having multiple hearts and lungs increases the chance of one of them failing and the whole system dying.
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Your attention please.


That is all, carry on.
Actually, unless they're as sparse as possible, multiple hearts would provide redundancy.
One could either have it so that half the capillaries in an area would belong to one heart and half would belong to another, or it could be (with some more complex plumbing) that each capillary is pumped by two hearts.

In that case, feel free to contribute to the discussion with how mechanical limitations in scaling can be overcome.
Simple, you don't go big, you go small and many.

Well there's Kleibers law as a guideline, scaling animal's metabolic rate to 0.75 power of the animal's mass.

The heart rate of animals decreases along that scale as size increases.

How this can all be put together with blood flow and everything else would take longer than i'm willing to look into it today.

Hopefully someone who has done the work will chime in.
I think it'd be pretty neat though if one could have something giant which didn't move slower than something small.

But does mass vs wattage become disproportionate if a scaled up human dances at the same pace as a regular human? I'm not sure, because one would expect the two would multiply by 8 per doubling in size, but I'm not sure if that takes torque into account.

I'm just not exactly sure what it means for a creature to not move slower as it becomes larger.
Its to retain max symmetry with min effort.

symmetric alignments are stable but also flexible static wise

but bones are built with decay and recycling in mind so they only shine over time.

however crystals are very symmetrical without having holes in them, making them extremely stable but also completely static too.

what you would want is to grow a more or less flexible crystal which I'm not sure is possible yet.

but I think pic related is a step towards there.
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We can build both types of structure. You be surprised with the material engineering we can do, albeit it often at $$$$.

The reason bone is so amazing is it optimized for things like flexibility and strength without trying to deal with things like fracture toughness or crack propagation that you really want in most things.

So then why does bone not fail given how poorly it preforms in those other categorizes which we often consider vital?

I mean cells constantly repairing the damage so the structures performance is not strictly dictated by the material itself, but by the system as a whole.
I'm not quite sure what you're talking about, but are you pretty much saying that you get a massive strength increase by having everything on the smallest scale of the material lined up correctly?
In which case, I'm not sure what putting holes in things has to do with symmetry.

Either way I suppose that still only gives a finite boost to strength, unless somehow a more spongey structure does not have each horizontal cross-section supporting the full weight of everything above it.
Another important limitation, in the case of living things, is waste heat dissipation, because of the square-cube law.
Waste heat dissipation is only a minor issue though if really crazy genetic engineering is possible, because entropy doesn't work normally in Everett Interpretation QM.
So you're basically saying that the organism wouldn't be cooked alive by waste heat, because there would be no waste heat? How could you achieve that on a macro scale?
If you radiate a negative amount of energy, it will presumably interact with and annihilate ambient energy, and concentrated energy must be created in equal quantity to the negative radiation.
In other words, an inversion of Hawking Radiation.
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