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388 years ago, Galileo worked out why human giants can't exist
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Re: 388 years ago, Galileo worked out why human giants can't exist
#12I don't know how convinced I am. First there were dinosaurs in the past, the brachiosaurus was 4 x as big as an elephant and there are probably yet undiscovered dinosaurs that were even bigger given discovery of partial fossils like the Sauroposeidon. Also we know in the past there were dargonflys with wingspans greater than 2 feet and centipedes that grew as long as a car.
They were larger but not as dense as mammals, we know had adaptations like less denser bones and different respiratory systems that allow for more efficiency and much more rapid growth into maturity. Modern birds show evidence of all these traits. When the Chicxulub extinction event happened it reset things so mammals got the upper hand on large sizes and eventully won out for the most part. Highly recommend The Rise and Fall of Dinosaurs, which I thought was going to be mostly stuff we learned as kids but was educational for me.
Re: 388 years ago, Galileo worked out why human giants can't exist
#13This seems like a flawed argument. By the logic in this article, wouldn't horses or cows, which weigh multiple times what a human does, have to have stocky rather than slender legs?
How big is big?
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.
Re: 388 years ago, Galileo worked out why human giants can't exist
#14In general, the argument holds some water, but it ignores the fact that human bones can take a lot more than their own weight today — depending, obviously, on how they are stressed (they can probably take maximum force along their lengthwise axis, but depends on the bone too — femur is said to take 30x the body weight, and we've got 2). Also, their structures — just like bending an edge on thin metal sheet — can significantly increase their carrying strength without changing the weight.
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.
Re: 388 years ago, Galileo worked out why human giants can't exist
#15This seems like a flawed argument. By the logic in this article, wouldn't horses or cows, which weigh multiple times what a human does, have to have stocky rather than slender legs?
How big is big? 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.
On the other hand, people can learn to fall more safely (like in gymnastics and martial arts). Maybe some version of those skills could somehow become instinctual, as maybe the corresponding thing is in cats?
Re: 388 years ago, Galileo worked out why human giants can't exist
#16This seems like a flawed argument. By the logic in this article, wouldn't horses or cows, which weigh multiple times what a human does, have to have stocky rather than slender legs?
1. They stand on 4 limbs, rather than 2. 2. That would be assuming that human legs are sized at the max capacity they can carry, which is not true.
Regarding 1, horses in particular are known to jump off two hind legs and land on their two forelegs, putting a lot more force on them than their stationary weight.
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.
Re: 388 years ago, Galileo worked out why human giants can't exist
#17I remember as a kid reading Lucifer's Hammer novel by Larry Nivel and J Pournelle, where at some point they discuss the theory that Earth was in a very different orbit and under different gravitational conditions that allowed giant dinosaurs to exist. It didn't make much sense to me at the time, but the description of muscle and bone cross-section as the core factor in their performance stayed with me.
Re: 388 years ago, Galileo worked out why human giants can't exist
#18Earlier quoted context omitted.
How big is big? 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.
On the other hand, people can learn to fall more safely (like in gymnastics and martial arts). Maybe some version of those skills could somehow become instinctual, as maybe the corresponding thing is in cats?
I guess if there were resources that were much more available to these agile tall people that might happen.
Re: 388 years ago, Galileo worked out why human giants can't exist
#19Important to keep in mind that the earth was smaller back then with lower gravity. The earth grows like all other living organisms.
Re: 388 years ago, Galileo worked out why human giants can't exist
#20About the argument that a beam's strength:weight ratio worsens as it grows: do the artificial structures humans use, like house frames or bridges' trusses, recover strength:weight ratio? Would a theoretical giant with a skeletal structure like a bridge or a house's frame be better off than one with a human-like skeleton of the same material? (And, related to another comment here, guessing the actual structure of bone produces some improvement relative to something solid?)