How durable would a kaiju-sized human be?

Question

I am writing a story that centres around a person who slowly grows larger and larger overtime, to the point of kaiju-size and beyond. They grow due to magic, so other than their vastly increased size I can say that they are at least physically exactly the same (same proportional skin thickness, bone density, etc). What I want to know is what it would take to hurt or even kill a giant human of varying sizes. What weapons would be effective and what wouldn't be? The three sizes I have in mind for this question are: 100 feet tall, 100 metres tall, and 500 metres tall. The story is set in a modern day setting, in an unspecified generic Western country. Thank you in advance!

Edit: For the sake of having this scenario work, the square cube law is ignored. The giant can carry themselves just as well as they would if they were normal sized. I am purely interested in how attacks against her by human forces would fare.

Answer 1

For the sake of having this scenario work, the square cube law is ignored.

I don't care, you can't silence me :p

Let's go over each size. For the sake of simplicity, I am going to assume normal humans are approximately Shakira sized, or about 150cm / 5" tall.

100 feet tall

This would mean the giant has the size of ~33 Shakiras stacked on top of each other.

Regular human skin is about 2mm (0.07 inches) thick. At 33x regular thickness, the human kaiju's skin would be around 66mm thick. For comparison, elephant skin is around 25mm thick.

So if you want to fight these giants, small handguns won't do. Even the hunting rifles one would use on elephants wouldn't be as effective. Consider bringing a Howitzer.

100 meters tall

That is about 3.3x larger than the previous giant. So we are talking about skin almost 200mm thick. For comparison a regular can of coke is usually around 115mm tall.

Human skin is not as strong as metal, but this is just too thick. Consider anti-vehicle weaponry at this point. If you wish to go melee, consider that male sperm whale skin can reach up to 350mm in thickness - the thickest of any animal - so maybe bring some harpoon launchers to the fight as well.

500 meters tall

Now the skin is about a whole meter thick. That is two thirds of a Shakira. You could slash this guy with a lightsaber, many hits wouldn't make it past the skin - and the ones that did would just be very shallow cuts.

At this point you need very powerful explosives - since cutting through the skin will be hard, shake the innards into a soup instead. If you do wish for open wounds, bring in missiles fired from vehicles, as a shoulder mounted bazooka might just tickle the giant.

Answer 2

Or do NOT ignore the Cube law, just make the skin/bones/etc. cubicly tougher. So, at 100 feet versus original 5 feet tall they're 20 times larger and the skin, bones, and Everything has to be 20x20x20 times as tough. Therefore getting a wound on them would be 8000 times as difficult. 100 meters (~3 x as big as 100 feet) would be 216,000 times tougher and 500 meters would be around 27,000,000 times as tough.

For that last guy, you're gonna want a wee bit more than a +1 sword. :P

Answer 3

I want to post an answer just to point out that Ant Man was done inconsistently, and to suggest that you try to avoid the same inconsistency.

The idea was that he was the same density but just smaller… but this was not always true. [Trying to avoid a spoiler] there is a large object in the movie that was shrunk using the same technology, and its density and weight were obviously those of a normal object of that size.

I can not remember all the instances offhand, but the point is that an object that weighs 75kg and is an inch tall is going to behave very differently from a normal 1cm tall object that is otherwise similar… and conversely an object that behaves physics-wise like a human being, but is only 1cm tall, can not possibly also happen to have the effect of a 75kg object whenever it suits the plot. (Ants are impressive, but a 75kg weight on top of one will surely squash it, regardless of whether it is 1cm tall or 170cm tall.)

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As for the person in question… . It sounds is though the scenario is just suspension-of-disbelief — that you want something that looks and acts like a human being, but happens (incoherently) to be 100m tall [or whatever].

In this case, just go with it. A normal sword will do almost nothing to it, but a normal sword scaled up will have the same effect as if both were normal scale. Etcetera.

The issue you do have is how it goes with something that is coherent, such as a large… whatever that interacts with this person. Suppose, for instance, that this person is sprinting — which would be in the order of 1000km/hr for the 100m version. Does this create a serious wind storm, or is it like a normal person running? Suppose this person… I dunno, punches a very large tree. Is it like a normal person punching a tree — which would break their hand — or is it like a normal person punching a stick — which would break the stick?

I suppose that, like with Ant Man, the audience will mostly not notice (hopefully).