5 ms·

The problem of “flying” in the sense you describe is fundamentally limited by the square cube law. Even birds, whose anatomies are literally evolved for flight,

The problem of “flying” in the sense you describe is fundamentally limited by the square cube law. Even birds, whose anatomies are literally evolved for flight, will have a tough time staying in the air if they are scaled up to have a similar mass to us humans.

centixel 4y ago
Wikipedia says a Pteranodon[0] might have weighed up to 200kg. I wonder if the different mix of gases in the atmosphere during the Cretaceous period made any difference to how much weight could be supported while flying. 0: https://en.m.wikipedia.org/wiki/Pteranodon https://en.m.wikipedia.org/wiki/Pteranodon
- hoseja 4y ago
  In the sense that more oxygen was available to muscles, maybe. In any buoyancy or aerodynamics sense, the effect would be miniscule at best.
- thejohnconway 4y ago
  Annoyingly, the wikipedia article was wrong, and mistakenly gave the figures for Quetzalcoatlus in that paragraph. Pteranodon weighed more like 20-30kg (I've edited it). The constraint on the size of flying animals is launch, not flight. Pterosaurs could get bigger than birds because they used quadrupedal launch, meaning they could use their flight muscles during the initial leap.
  - agentwiggles 4y ago
    I never cease to be amazed how damn _big_ dinosaurs were. The size comparison on the page for Quetzalcoatlus is seriously mind boggling - the thing was almost the size of a small plane!
aaaaaaaaaaab 4y ago
There were pterosaurs much larger than humans.
- adrian_b 4y ago
  While there were pterosaurs as large as a giraffe (having similar proportions when on ground), they were very light for their size, probably no more than 2 to 4 times heavier than a human.
leobg 4y ago
Lilienthal himself didn't, as far as I know, address your precise argument (the water strider bug scaling issue). But your comment reminded me of this snippet from his 1889 book: The bodies of flying creatures are not so materially lighter than those of other animals, as to justify us in considering this difference in weight an essential condition of flight. It is often asserted that the hollow bones of birds facilitate their flight, especially since the hollows are filled with heated air, but it does not require much thought to come to the conclusion that this diminution of weight is barely worth mentioning. Also, we have not been able as yet to prove that the muscle and bone substance, as well as other parts of the bird's body, are specifically light. [...] After a bird is plucked, no one will assert that it is propor tionally lighter than other animals, and our housewives are certainly not under the impression that a pound of bird's flesh, even with the hollow bone included, is more bulky than an equal weight of flesh from another animal. [0] [0] Otto Lilienthal, Birdflight As the Basis of Aviation, pages 2-3, https://s3-eu-west-1.amazonaws.com/bga-sg-archive/Books/BIRDFLIGHT%20AS%20THE%20BASIS%20OF%20AVIATION.pdf https://s3-eu-west-1.amazonaws.com/bga-sg-archive/Books/BIRD...
thejohnconway 4y ago
Some birds and several pterosaurs got to human masses and more. Staying in the air is not much of a problem, but launching is. Pterosaurs have a massive advantage here in that they launched with all four limbs, meaning they could use their flight muscles to launch. Birds can't do this and have to rely on their legs (which are useless in the air).

centixel 4y ago

Wikipedia says a Pteranodon[0] might have weighed up to 200kg. I wonder if the different mix of gases in the atmosphere during the Cretaceous period made any difference to how much weight could be supported while flying. 0: https://en.m.wikipedia.org/wiki/Pteranodon https://en.m.wikipedia.org/wiki/Pteranodon

hoseja 4y ago
In the sense that more oxygen was available to muscles, maybe. In any buoyancy or aerodynamics sense, the effect would be miniscule at best.
thejohnconway 4y ago
Annoyingly, the wikipedia article was wrong, and mistakenly gave the figures for Quetzalcoatlus in that paragraph. Pteranodon weighed more like 20-30kg (I've edited it). The constraint on the size of flying animals is launch, not flight. Pterosaurs could get bigger than birds because they used quadrupedal launch, meaning they could use their flight muscles during the initial leap.
- agentwiggles 4y ago
  I never cease to be amazed how damn _big_ dinosaurs were. The size comparison on the page for Quetzalcoatlus is seriously mind boggling - the thing was almost the size of a small plane!

aaaaaaaaaaab 4y ago

There were pterosaurs much larger than humans.

adrian_b 4y ago
While there were pterosaurs as large as a giraffe (having similar proportions when on ground), they were very light for their size, probably no more than 2 to 4 times heavier than a human.

leobg 4y ago

Lilienthal himself didn't, as far as I know, address your precise argument (the water strider bug scaling issue). But your comment reminded me of this snippet from his 1889 book: The bodies of flying creatures are not so materially lighter than those of other animals, as to justify us in considering this difference in weight an essential condition of flight. It is often asserted that the hollow bones of birds facilitate their flight, especially since the hollows are filled with heated air, but it does not require much thought to come to the conclusion that this diminution of weight is barely worth mentioning. Also, we have not been able as yet to prove that the muscle and bone substance, as well as other parts of the bird's body, are specifically light. [...] After a bird is plucked, no one will assert that it is propor tionally lighter than other animals, and our housewives are certainly not under the impression that a pound of bird's flesh, even with the hollow bone included, is more bulky than an equal weight of flesh from another animal. [0] [0] Otto Lilienthal, Birdflight As the Basis of Aviation, pages 2-3, https://s3-eu-west-1.amazonaws.com/bga-sg-archive/Books/BIRDFLIGHT%20AS%20THE%20BASIS%20OF%20AVIATION.pdf https://s3-eu-west-1.amazonaws.com/bga-sg-archive/Books/BIRD...

thejohnconway 4y ago

Some birds and several pterosaurs got to human masses and more. Staying in the air is not much of a problem, but launching is. Pterosaurs have a massive advantage here in that they launched with all four limbs, meaning they could use their flight muscles to launch. Birds can't do this and have to rely on their legs (which are useless in the air).