# Worlds that could not exist

## Main Question or Discussion Point

Winged humanoids are popular in scifi, but due to the square cube principle (weight increases faster than strength), it's a nonstarter.

I have seen people say... but what if their world is lower gravity with a thick atmosphere?

A few challenges there that I am not sure can be overcome.

1. The moon Titan is such a place, yet I have read that the reason it's dense gases do not boil off and evaporate into space is because it is so far away from the sun. So sure, people could fly there... and get frost bite in minutes or less... even if air was breathable there.

2. Moving a Titan-like world closer to the sun to improve the frigid temperatures I have read would make the gases evaporate away into vacuum, since the gravity of Titan is rather low anyway. I do not know if this is true, but I suspect it is, since our moon is larger than Titan and is not holding an atmosphere, likely because it could'nt, unless the gases in question were the heaviest you could find so they would hold more readily to the surface

That's one planet type that likely could not host Earth life and exist. Anymore you got? Or wanna discuss?

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Winged humanoids are popular in scifi, but due to the square cube principle (weight increases faster than strength), it's a nonstarter.

I have seen people say... but what if their world is lower gravity with a thick atmosphere?

A few challenges there that I am not sure can be overcome.

1. The moon Titan is such a place, yet I have read that the reason it's dense gases do not boil off and evaporate into space is because it is so far away from the sun. So sure, people could fly there... and get frost bite in minutes or less... even if air was breathable there.

2. Moving a Titan-like world closer to the sun to improve the frigid temperatures I have read would make the gases evaporate away into vacuum, since the gravity of Titan is rather low anyway. I do not know if this is true, but I suspect it is, since our moon is larger than Titan and is not holding an atmosphere, likely because it could'nt, unless the gases in question were the heaviest you could find so they would hold more readily to the surface

That's one planet type that likely could not host Earth life and exist. Anymore you got? Or wanna discuss?
You could search for solutions containing sulfur dioxide near critical point. Heavy and viscous. World like mini-Venus in binary system which preferentially lost carbon dioxide during red giant phase of one of stars. Still too toxic for human proper, although room temperatures are plausible.

In more controlled environment, you can try fly humans in sulfur hexafluoride atmosphere. It may be used to terraform some small and and very cold planets - down to size of Moon orbiting at asteroid belt-like insolation..

You could search for solutions containing sulfur dioxide near critical point. Heavy and viscous. World like mini-Venus in binary system which preferentially lost carbon dioxide during red giant phase of one of stars. Still too toxic for human proper, although room temperatures are plausible.

In more controlled environment, you can try fly humans in sulfur hexafluoride atmosphere. It may be used to terraform some small and and very cold planets - down to size of Moon orbiting at asteroid belt-like insolation..

What you get lifeform wise would likely breath stuff that we cannot breath, and eat plants and lifeforms we would also find toxic.

You know what the subtle truth about terraforming is?

Destroy the natural surroundings to make it livable for a lifeform. Since something must be substituted otherwise the lifeform cannot live, so it cannibilizes resources of the host world and bends them to host it's life, at the expense of the natural order.

Ethics come into play if someone is actually living there.

Since alien terraforming on an inhabited world is lethal to natives. One thing this movie was accurate on via science.

I read a story a couple years ago that featured winged humanoids on several worlds of our Solar System. The best example I can remember is Ceres, the characters in the story had constructed a shell around Ceres and thawed it out over time. The result was a mostly water-covered core with a few islands. Some of these islands were inhabited, the rest of the population lived on the inside of the sphere. Since the thicker atmosphere was protected by the shell, the humanoids (who were genetically engineered specifically for life on Ceres) could easily fly around from place to place. Here's a link for anyone that is curious:
https://www.amazon.com/dp/B074SZVSMY/?tag=pfamazon01-20

Mars now has a thin atmosphere. But look at the river valleys. Mars had enough warmth and dense air for flowing rivers for hundreds of millions of years. Imagine a planet like young Mars, or only slightly more massive, and you could have atmosphere denser than Earth.
What is "humanoid"? Pterosaurs are bigger than humans, but quadrupeds.
Does a flying "humanoid" have to be a hexapod, with four limbs attached to shoulder girdle?
How are bones, joints, muscles and tendons arranged in angel shoulders? Like, transmitting the downstroke forces?

A planet the size of Mars could have a thicker atmosphere than Earth's.
If you want it to last longer, give it a protective magnetic field by adding more uranium to keep the core liquid.

What is "humanoid"? Pterosaurs are bigger than humans, but quadrupeds.
Does a flying "humanoid" have to be a hexapod, with four limbs attached to shoulder girdle?
How are bones, joints, muscles and tendons arranged in angel shoulders? Like, transmitting the downstroke forces?
Well, humanoid is what you get after a few generations of people have lived and bred on another world. They would adapt over time to the new gravity, atmospheric pressure, etc until they were no longer an Earthly human. Once adapted to a low gravity environment it's doubtful they could even safely return to Earth. The story I referenced gets around the slow process of evolution by genetically engineering people for a specific environment like Ceres.
The inhabitants in the story do indeed have six limbs but they still walk upright. The description sounded more like bat wings than "angel" or bird-like wings. As I remember, the author didn't go into fine detail on the exact physics of how they flew, (it's been a while since I read it, so I could be wrong) but that's sci fi for you. :)

I'm confused why you think such a thing is a nonstarter because of the square cube principal. There have been animals on this planet that were much much bigger than humans. Quetzalcoatlus is thought to have weighed close to a thousand pounds. The air density at the time was likely very similar to todays, the difference was that there was way more oxygen in the air. Oxygen is energy rich, so it was the extra energy that allowed muscles to get so big and strong.

It's possible to have a much denser atmosphere and still be close to the sun. Venus' atmosphere is 90 times as dense as Earths and it's both a smaller planet (slightly) and closer to the sun.

You also have to remember that most animals to not do the majority of their flying by flapping their wings, or are even capable of taking off vertically. I'm 100% sure that a swan can not just take off, it has to have a running start. Their wings are aerofoils, 99% of most birds "flight" is actually a glide. Lots of birds can lock their wings in place and ride updrafts. That's how they're able to fly thousands of miles without stopping to each every five minutes.

I'm confused why you think such a thing is a nonstarter because of the square cube principal. There have been animals on this planet that were much much bigger than humans. Quetzalcoatlus is thought to have weighed close to a thousand pounds. The air density at the time was likely very similar to todays, the difference was that there was way more oxygen in the air. Oxygen is energy rich, so it was the extra energy that allowed muscles to get so big and strong.

It's possible to have a much denser atmosphere and still be close to the sun. Venus' atmosphere is 90 times as dense as Earths and it's both a smaller planet (slightly) and closer to the sun.

You also have to remember that most animals to not do the majority of their flying by flapping their wings, or are even capable of taking off vertically. I'm 100% sure that a swan can not just take off, it has to have a running start. Their wings are aerofoils, 99% of most birds "flight" is actually a glide. Lots of birds can lock their wings in place and ride updrafts. That's how they're able to fly thousands of miles without stopping to each every five minutes.
Venus worlds is too hot for anything winged to survive... that's wh happes with dense gases near the sun.

Titan is too cold for anything winged to live, and were it closer, the vape effect, which Venus avoids with dense gases and greater gravity than Titan yields.

Greater oxygen in the air creates a whole bunch of things all at once (easier to blow up and combust stuff) as will as easier for metals and other items to oxidize (rust).

Besides that, great wingspan is required based on hunanoid mass or greater, it woukd dwarf theperson so much that they would not fit the stereotupe fantasy that people want.

You can still do it, but don't expect them to fly for long if at all looming like s stereotype