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as the title say my question is: What planet composition is need to have giant human that make earth human similar in comparison to ant size to them?

i know realistically and probably its imposible but i just want to know the composition.

the giant human breath oxygen and pretty much similar like earth human except they are so massive compare to earth human.

they can do normal activity and their organs work fine just like earth human.

with minimum two people and maximum to earth population 7.7 billion population

feel free to edit the tag because i dont know which tag is more apropriate for my question.

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You have a few issues that the planet and its residents need to confront

Size of ant: average 10mm

Size of human: average 1650mm

Ratio: 1:165

For your giant to be same ratio from a human, your giant's size: 272.5m high

Due to the Square Cube Law (volume / weight and surface area increase at different rates as size enlarges) you run into issues when you have giants. This is why elephant look so ponderous, heavy and flabby. They aren't simply 'scaled up' versions of smaller creatures.

The reason is for elephants as they grow larger, their weight increases at a much greater ratio. More weight = more blood flow pressure required to service it, more food, more stretchy skin, more force required to move it. Hence slow and heavy.

It also affects our skeletons. Bones would break under such force as your giant would endure.

So we need to eliminate the effect of weight - let's just say we need then a much lower gravity planet, weak enough such that weight is not so much of an issue.

The other factors are now more physiological. Blue whales are 30m in length, the largest currently on the planet: why aren't they larger? The answer: energy. Mammals use a lot of energy to maintain various systems in our bodies, 10 times more than a reptile. Your giant, if like us, would have massive metabolic issues to maintain the services required to keep body temperature, heart rate and flow, muscle tone and oxygenation, constant. So I would imagine you would need a high level of oxygen in the air, perhaps a higher air pressure, a fairly constant warm temperature planet to reduce warmth required for our giant, and not much in the way of mountains for the giant to climb.

Food.

You need heaps of it, and this is a major determinant of size. This planet needs to be completely filled with low energy consuming food. Blue whales eat krill, basically they don't need to chew, they just swallow and the krill turn into easily absorbable food for their bodies, your giants would likely be shovelling food down constantly and the food needs to not require to many resources to convert into essential fats, vitamins, proteins and other essentials.

And gestation. To get to maturity, your giant needs to grow from a single cell, to a full size adult. This severely limits the size of animals on our planet - your giant would not just take decades to get to maturity, but likely centuries. The planet would need to have been there for a very long time to enable a lifecycle where this size and length of lifespan is beneficial for the giants species.

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    $\begingroup$ I think you also have an issue with the differences in air pressure of the atmosphere from the surface to the giant's nose/mouth when standing. I don't know what it would take to reduce that difference, so the giant didn't pass out whenever he stood up or sat down. $\endgroup$ – workerjoe Nov 20 '19 at 14:57
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    $\begingroup$ If anything a cold planet would be better - the giant will generate a lot of metabolic heat and have a smaller surface area to radiate it (see Elephant's ears) $\endgroup$ – Tim B Nov 21 '19 at 10:22
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    $\begingroup$ Some of these problems could be improved by making the giants cold(er) blooded with a slower metabolism and similar optimizations. $\endgroup$ – Tim B Nov 21 '19 at 10:24
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    $\begingroup$ @workerjoe such a giant would almost certainly not look anything like a human. Even on a suitable planet, the kinds of issues mentioned would drive evolution down different genetic pathways. Rather than standing tall, a creature of that size would likely be bulky and long. If 270m height were needed then it would likely have long thin neck. It would likely live in a body of water to support much of its mass. You might find a way to allow a creature of that size but it wouldn't look anything like a scaled up human. If anything, more like a supergiant sauropod. $\endgroup$ – SO failed us all... Bye... Nov 21 '19 at 10:56
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Humans exist at a certain size because of the structure of their bones, muscles and their metabolism. Humans cannot exist too far beyond their normal size for many reasons. One issue is the fact that bone strength increases with the square of the bone size whereas weight increases with the cube of size, another issue is the ability to retain heat. Too large and the body will not be able to cool itself sufficiently, to small and all of the heat will rapidly drain away.

So what you propose is not possible within a science based answer.

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Two factors could make it possible (if extremely unlikely):

1: The planet has very low gravity. The weight of the giant is so small that its muscles can hold it up and move it around, even with a very small muscle cross section to mass ratio (square-cube law). The mass itself, however, will be a major issue, since intertia will be great. The giant would only be able to change speed or move limbs at an exceedingly low pace.

2: The planet has a very thick atmosphere. The specific gravity of the atmosphere is very close to that of the giant, so the giant almost floats in it. Whales on Earth can get very big because they float in water. Your giant will be far larger than this, however.

In neither case would it make much case for humanoid giants to evolve. On the low-gravity planet, smaller beings could maneuver much more quickly than the giant, basically being able to eat it alive. On the heavy-atmosphere planet, it would make more sense to have exactly the same specific gravity as the atmosphere, allowing beings to swim in it.

Another issue is the speed of neural signals. The speed of nerve impulses is roughly between 1 and 100 m/s. It will hence take as much as three seconds for a nerve impulse from the brain to reach the feet. Brain activity will also be far slower than for an ordinary-sized human, by more than a factor of one hundred.

Because of these factors, I believe that such giants would have to be made, rather than evolved, perhaps as an experiment, and they would likely not last long in an evolutionary timescale.

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    $\begingroup$ Distributed processing or specialist nerve fibers could help with the neural signals issue. $\endgroup$ – Tim B Nov 21 '19 at 10:27

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