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I loved Godzilla movies when I was a kid (still do), but ever since Pacific Rim came out, I have been pondering just how implausible really large humanoids would be given the laws of physics.

For the sake of this question lets say we have the following:

  • Humanoid figure, proportional to an average human male
  • 30 meters tall
  • Movements have similar timing to average human male
  • Everything takes place on Earth

How strong would its body have to be to withstand the force of simply moving around? Is there any physical material we know of that could accomplish this?

What would happen to the environment around such an entity exerting such forces? Would the ground simply give too much to make quick movements like running impossible?

I am very interested in the math behind all of this.

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closed as too broad by ACuriousMind, Brandon Enright, John Rennie, JamalS, Pranav Hosangadi Jan 31 '15 at 17:05

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  • $\begingroup$ This isn't a troll by the way... I am genuinely curious about this, but am no mathematician. I know it is all very implausible, but would like to understand why. $\endgroup$ – Josh Jan 29 '15 at 22:08
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    $\begingroup$ For comparison, its weight would be between one and two blue whales. So it's not an implausibly large creature, just ill-suited to land-dwelling bipedalism. $\endgroup$ – Charles Jan 29 '15 at 22:16
  • $\begingroup$ @Charles - That's a good point. 100-150 tons would be a heck of a lot of force if it were pushing off a relatively small foot on the ground. $\endgroup$ – Josh Jan 29 '15 at 22:22
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    $\begingroup$ 100 tons scales to 60 pounds (optimistically assuming 2m height) which seems very light for an average adult male. 250-350 tons is more reasonable depending on what you assume for height. $\endgroup$ – Charles Jan 29 '15 at 22:29
  • $\begingroup$ I don't know enough to give a full answer but this page has some useful guidance on scaling laws, and this page has a table of ultimate tensile strength for various materials (possibly the best bet would be to have bones made of graphene, but maybe even better materials will come along) $\endgroup$ – Hypnosifl Jan 29 '15 at 22:39
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This is the line I have been working on, but using Male African Elephants, and Dinosaurs with " n " Elephant Volumes , where the surface gravity of the Earth is inversely proportional to the cube root of the n E.V. ( Elephant Volumes ). n is limited to less than or equal to 13.0 E.V. The number has been getting smaller over the last 252 million years, which mean that the maximum allowable size of animals is gradually getting less and less as time passes.

There are still some conundrums.

Why does a Dinosaur of 8 Elephant Volumes in a surface gravity of 0.5 g ( now ) only have twice the surface area of the bottom of its four feet ?

The downward force is 8 x 0.5 = 4, but the force per unit area ( pressure ) is 4 / 2 = 2 times the unit force of an Elephant. So why did they not get stuck in the Mud?

Any way, to answer your questions, Humans are no where near the maximum allowable limits of animal sizes in the current surface gravity, but there are some limits.

Limits: The size of the Pump ( heart ) , and the hydraulic pressure required to pump blood to the brain, without bursting blood vessels in the legs and feet.

Structural Limits: The Elephant is at the Maximum allowed ( 40 % muscle mass ) and ( 27 % bone mass ). The upper limit is 67 %. The other 33% is for all the other non structural stuff ( all the organs, fluids, brain, nerves, connective tissues and lots of other stuff ).

There is a tendency to maximize size in some animals, but this comes with a price. The price is it takes lots of food to keep big animals big. If the food becomes scarce, the biggest animals in a species die off, while some smaller individual animals still survive.

When you look at the pictures of the skeletons of large extinct humans, look for telltale signs. The relative dimension will change, the leg bones will be abnormally long and robust, and the ends of the leg bones will be larger in comparison to the cross-section at the mid height of the leg bones. The spine and head will be more robust, and the arm bones also longer and more robust.

If the picture looks too skinny, or slender, it is a fake. The overall proportions need to look more like long cow legs, or bison legs, with large joints, especially the Knee joints, and hip joints.

If you double the Height of a Human to 12 feet, then it will weight more like 8 times the weight of a current big human ( 250 lbs to 300 lbs ) becomes 2000 lbs to 2400 lbs. This is not impossible, but the structural requirements of the bones, muscles, ligaments, and tendons have to be reflected in an appropriately robust skeleton that would support this kind of weight.

You might also find spinal problems ( curved spines ). Short life spans ? Low Population numbers ? This would be an interesting thing to study. They may have been quite possible before we hunted out the largest food source animals around 8,000 to 10,000 years ago, and the climate changed dramatically.

Food for thought.

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