DE version is available. Content is displayed in original English for accuracy.
Advertisement
Advertisement
⚡ Community Insights
Discussion Sentiment
79% Positive
Analyzed from 1601 words in the discussion.
Trending Topics
#giant#dinosaurs#more#weight#big#bones#argument#exist#human#strength
Discussion (27 Comments)Read Original on HackerNews
again i’m guessing, but if the conclusion is something like “if giant humans existed, X, Y and Z wouldn’t work”. then a “giant humans” would have to be something decidedly non-human.
https://tvtropes.org/pmwiki/pmwiki.php/Main/SquareCubeLaw
It's the reason why giant robots probably couldn't be as agile or powerful as in something like Transformers or Gundam, and why kaiju like King Kong or Godzilla couldn't exist in the real world.
https://en.wikipedia.org/wiki/On_Being_the_Right_Size
I'd also note that it does not take a lot for someone to be a "giant". When average height was 1.6m, someone 2.2m tall was certainly a "giant" (they are even today, but it means they'd frequently be asked if they are playing basketball :)).
But even if they were 4m tall, they'd certainly be called a giant and certainly regular human bones could handle weight up to say 450 kg. Heck, someone brought up horses and cows, and horses certainly jump off two hind legs and land on two front ones, putting a lot more than 600kg of their standing weight on them.
So in short, Scientific American is right to bring up the fact that someone like Galileo would put his genius to folk topics back in the day, we do have a bit more to lean on today to come up with even stronger conclusions — so they'd better highlight how his thinking compares to what was known back in the day.
> scaled-up wooden houses would not support their own roofs
Hmmm this argument fails to mention giraffes, elephants or dinosaurs. (Edit: ooops it does mention elephants and dinosaurs) But clearly, land animals with bones can be quite a bit larger than humans. Similarly the houses comment ignores that large multi-story wooden buildings that support their own roofs exist, and already existed in Galileo’s time.
There might be reasons today’s evolution of human anatomy can’t get any larger than 9 feet tall, but this argument about physics and bones and square vs cube growth rates is pretty unconvincing. The argument skips right past the idea of “giants” that are only 1.5x or 2x or 3x taller, rather than 10x or 100x taller. Sure animals cannot be “inordinately” bigger, but that does not explain why they can’t be twice as big.
Arguments around bone scaling ignores the impact forces of running. Scaling often means trading margins not just keeping all constraints the same.
True for Scientific American today, not true for Galileo.
“Dinosaur” wasn’t a thing we started knowing about until the early 1800s. Benjamin Franklin died not knowing Dinosaurs were a thing.
But Galileo would have certainly known about elephants though.
Right, that’s what I was implying. However, I looked again and the article does mention elephants and dinosaurs.
Hopefully no cheese eating space mold gets up there or we're done !
Note that if you disable JavaScript you can read this without the nag wall.
2. That would be assuming that human legs are sized at the max capacity they can carry, which is not true.
On 2, I believe that's the GP's point too — human leg bones (or horses') can obviously take a lot more than their standing/walking/running weight.
They can take more stress than standing, but the scaling law is still there.
If you scale linearly height/section the max stress won't scale linearly because the weight will scale cubically.
The practical limit for bipeds is probably ability to survive a fall to the ground. It's not super common, but enough people die simply from falling from standing.
Also we know in the past there were dargonflys with wingspans greater than 2 feet and centipedes that grew as long as a car.
It's also possible that for larger creatures a less dense and more flexible skeleton material (in general) might be ideal. Especially for animals that are not warm blooded (larger volume to mass ratio might resist temperature changes better?)
Nonetheless, the biggest dinosaurs were several times heavier than the heaviest terrestrial mammals that have ever lived, which in turn were several times heavier than the biggest elephants of today.
So probably dinosaurs were close to the size limit that is imposed by the mechanical properties of vertebrate tissues like bones, tendons and muscles, while in the present terrestrial mammals the size is limited by the availability of food and by the humans who have always hunted preferentially the biggest animals they encountered, and not by the strength of their bones.
What IS true though is that pterosaurs and later birds and bats came onto the scene, and that's just game over for giant dragonflies.
An efficient circulatory system and myelinated nerves.
At small sizes, the circulatory and respiratory systems of insects work better, but at big sizes those of vertebrates work better.
The myelinated nerves have the same speed for propagating nervous signals as non-myelinated nerves that are much thicker, so thick that an insect could not have many such nerves. At small sizes this does not matter, but at big sizes if the nerves are not fast enough the reaction times of an animal can become too slow, e.g. the head might need a big fraction of a second until noticing that something bites the tail.
The combined results are that an insect as big as a typical vertebrate would react mostly sluggishly and it would be able of only very short bursts of intense activity, before becoming tired. This would put it at a serious disadvantage.