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If we wish to colonize another world, finding a planet with a gravitational field that humans can survive and thrive under will be crucial. If its gravity is too strong our blood will be pulled down into our legs, our bones might break, and we could even be pinned helplessly to the ground.
Finding the gravitational limit of the human body is something that's better done before we land on a massive new planet. Now, in a paper published on the pre-print server arXiv, three physicists, claim that the maximum gravitational field humans could survive long-term is four-and-a-half times the gravity on Earth.
Or, at least you could if you are an Icelandic strongman – and Game of Thrones monster – who can walk with more than half a metric ton on your back. For mere mortals, the researchers say, it would need to be a little weaker.
[...] For the maximum gravity at which we could take a step, the team turned to Hafþór Júlíus Björnsson, an Icelandic strongman who once walked five steps with a 1430 pound log on his back, smashing a 1,000-year-old record[*].
[*] YouTube video.
What's the Maximum Gravity We Could Survive?
(Score: 3, Interesting) by VLM on Saturday September 22 2018, @05:46PM (4 children)
I wouldn't worry too much about bones, we have four legged dogs running around from cat sized to pony sized, not to mention comparing "people of walmart" scooter drivers to marathon runners, I think we're all good over a 4G range. Bone isn't smart, it doesn't know the difference between 1 and 4 G planet anymore than it knows the difference between 400 pound vs 100 pound person.
The real problem is likely fluid dynamics. Like whats the NPSH of a human heart, could the vascular pressure required result in pulling a vacuum on leg veins? Could your brain blood vessels survive even the weakest tap if they had to run at 30 PSI blood pressure for high-G? Would it be expected that everyone who lays down for awhile automatically faints when they stand suddenly? Tensile strength of skin and stuff? Most importantly, I would guess boobs would be droopy to an unimaginable level, just tuck em in your belts, ladies.
Strange thought: Sweat "works" because it evaporates slowly on skin; does it work as an adaptive measure if 4G are pulling every droplet of sweat off like a salad spinner centrifuge dries lettuce? People might evolve to stop sweating since all it does is make your shoes wet and slippery, and evolve toward panting like a dog with long tongues, or maybe we'd evolve floppy ears.
Even something like chewing... imagine something pulling your jaw down with 3x the weight of your jaw every time you chew food, might be weird.
(Score: 2) by Immerman on Saturday September 22 2018, @05:55PM (3 children)
>Bone isn't smart, it doesn't know the difference between 1 and 4 G planet anymore than it knows the difference between 400 pound vs 100 pound person.
Umm, bone *absolutely* knows the difference between a 100 and 400 pound person. It doesn't need to be smart for that, it just needs to be subjected to the constant microfractures inflicted upon it by normal life, and the associated repair and reinforcement mechanisms. A 400lb person is going to either inflict more and larger microfractures in the course of performing the same activity.
(Score: 2) by VLM on Tuesday September 25 2018, @11:35AM (2 children)
Not under varying gravity. A femur can't tell the difference between the force applied from the body above of 100 Kg at 1G or 50 Kg at 2G, its the same number of newtons of force.
(Score: 2) by Immerman on Tuesday September 25 2018, @02:03PM (1 child)
Well not too much at least, there's probably still some differences in stress profiles just due to the sort of activity you'd engage in.
But that wasn't the assertion I was refuting - which was that bone didn't know the difference between 1 and 4g, OR between 100 and 400lb. It absolutely "notices" that sort of stress difference, regardless of whether the cause is a difference in gravity or mass.
(Score: 2) by VLM on Tuesday September 25 2018, @06:25PM
Ah I think I see the confusion. I'm implying the euler buckling column strength of a femur is affected the same from 400 pounds of potbelly at 1G as 100 pounds of potbelly at 4G, it can't "know" where the identical number of newtons of force come from. From your point of view yes separately a bone experiences different forces at 100 vs 400 pounds or 1 vs 4 G