Disclaimer: I did see a previous question touching on something like this but what I’m confused about was NOT addressed so hopefully this is allowed.
They say that the surface area volume ratio limits how big things can grow because surface area scales as a square while volume scales as a cube, so the ratio of volume to surface area goes up as you get bigger. Fair enough. BUT: how is this not just a matter of what units you’re using?
For example, a 1x1x1 ft cube has a surface area to volume ratio of 6sq. Ft to 1 cubic foot, so 6:1. A 1x1x1 meter cube has a ratio of 6:1 too but the units are meters. Couldn’t you always define your units so that you have a 6:1 ratio with any size of cube?
To bring it back to the actual question, wouldn’t your ratio be essentially the same no matter how big your object is? Imagine you expanded everything in the universe by the same amount but kept your unit of measurement the same, you wouldn’t suddenly hit some limit where it stops working right? Does it have something to do with the size of molecules and proteins etc? Please help I am so confused
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This is all independent of units.
To simplify the whole thing imagine a weight suspended from a rope. The rope is just strong enough to not snap under the weight.
How much weight a rope can carry is largely depended on its diameter.
If you get a rope that is twice as thick in diameter it might carry about four times the weight.
However if you double the size of a weight it will weigh 8 times as much.
For living things that means that if you for example want to scale a human body up to twice its height the bones would be twice as long and have cross section four times as large but their weight would be eight times as much.
A giant human would need much thicker legs than a simple scaled up normal size human.
You also run into problem in other areas like all that stuff about lungs and the heart and the blood and heat dissipation.
There is a reason why large animals look different than small animals would if you scaled them up.
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