ClaecElric4God wrote:So...uh....I...um...what? Why don't we believe in giants again?
They are mathematically impossible.
Galileo begins “Two New Sciences” with the striking observation that if two ships, one large and one small, have identical proportions and are constructed of the same materials, so that one is purely a scaled up version of the other in every respect, nevertheless the larger one will require proportionately more scaffolding and support on launching to prevent its breaking apart under its own weight.
This is because of how mathematics works, and scaling.
"Who does not know that a horse falling from a height of three or four cubits will break his bones, while a dog falling from the same height or a cat from a height of eight or ten cubits will suffer no injury? ... and just as smaller animals are proportionately stronger and more robust than the larger, so also smaller plants are able to stand up better than the larger. I am certain you both know that an oak two hundred cubits high would not be able to sustain its own branches if they were distributed as in a tree of ordinary size; and that nature cannot produce a horse as large as twenty ordinary horses or a giant ten times taller than an ordinary man unless by miracle or by greatly altering the proportions of his limbs and especially his bones, which would have to be considerably enlarged over the ordinary."
Basically the cross-sectional area of a material determines how much weight it can support. Let's say I have a stone pillar that is just enough to support the weight of a particular statue. Now let's say I want a statue twice as big. I can't just double the size of the pillar, because it will be too weak to hold the bigger statute; because of how physics works, a statue twice as big will weigh eight times as much (because you are doubling the width, the height, and the length, and 2 x 2 x 2 = 8).
However if you double the size of the stone pillar, you are only increasing the weight it can hold by 4, because a cross sectional area is only two dimensions...2 x 2 = 4. This kind of stuff is important in, say, architecture, because you can't just take a blueprint of a building and just scale it up by multiplying everything by a number.
Galileo understood that you cannot have a creature looking a lot like an ordinary gorilla except that it’s sixty feet high. Likewise, you can't have a human that looks like an ordinary human that's sixty feet high. The cross-sectional area of the leg bones wouldn't be able to support its weight.
There is a famous essay on this point by the biologist J. B. S. Haldane, in which he talks of the more venerable giants in Pilgrim’s Progress, who were ten times bigger than humans in every dimension, so their weight would have been a thousand times larger, say eighty tons or so. As Haldane says, their thighbones would only have a hundred times the cross section of a human thighbone, which is known to break if stressed by ten times the weight it normally carries. So these giants would break their thighbones on their first step.
There's two ways around this problem, both involving changing the skeleton. The first is for the bones to change in size by a factor greater than the enlargement. So if you have someone ten times the size of a human, the bones would need to be more than 10 times larger than a human's bones. I don't know what the exact number would have to be, but for the sake of simplicity, let's say that they'd need to be 50 times larger than a human bone.
So now, you have someone 10 times the size of a normal human...with bones 50 times larger. As you can imagine, they wouldn't look very human at all. They would look like grotesque monsters. So, we still can't have human-looking giants in this solution.
The second involves the skeleton being made out of a much stronger and entirely different material than our human skeletons. If their skeletons were made out of say, steel, or some other material as strong as steel, then it would be able to support much more weight, and they could keep the same proportions as a human.
However, since humans obviously do not have skeletons made of material like that, this would mean that the giants would also not be human, even if they looked human. So unless you want to go with the theory that God miracled up adamantium coated skeletons for these human giants, then we still can't have human-looking giants in this situation either.