(Machine translation by DeepL translate)We've been experimenting with gravity that is 10 times stronger than the Earth's (=10G).
I wonder how much gravity we can actually withstand.
Gravity (strong)
Gravity (Stronger)
First, let's examine the strength of bones.
Let's assume that the entire body weight is supported by a single leg.
The tibia bone has a cross-sectional area of 1 cm2 and can withstand up to 1730 kg.
Even if the gravity increases 10 times, the bone will not break.
If the gravity becomes strong enough for a 50kg person to reach 4680kg
In other words, if gravity becomes 94G, your shins will shatter under your own weight.
This is for a stationary person.
But if you run, the stress on your bones will only be doubled at most
If you don't get knocked down, the problem is weakness of the muscles, not fractures.
Let's think about standing up from a sitting position.
You use your knee joint as a fulcrum to lift yourself up with your quadriceps muscles.
The magnitude of the torque "r1×F" (×2) must be greater than the torque "r2×Mg" that gravity pulls the body to stand.
If we substitute the average value, gravity must be less than 1.1G
In other words, the earth's gravity is the limit for standing by muscle strength alone.
Force F is proportional to the cross-sectional area of the muscle, so if you stand up at 10G
the cross-sectional area must be at least 9 times larger.
In reality, you can't train that much, and even a top athlete can only lift four times the weight of an average person in a squat
Also, if we take into account the fact that you have to bend over, and if the gravity you can withstand is increased by 20%.
Realistically, the limit for a trained person to stand up would be 5.3G.
Next is the limit of gravity when walking.
Let's consider the following model of walking
An inverted pendulum moves forward with the feet as its fulcrum.
The center of gravity moves up and down. The pendulum moves efficiently by exchanging kinetic energy and potential energy.
Here, we refer to the world record of a powerful Icelandic man (179 kg). He can walk 5 steps with a 649kg log on his back.
This is the limit of a person's strength, calculated by a walking model.
When you don't carry a log, you know what the limit of gravity is.
If you increase the gravity, you will not be able to walk at 4.6G
Reference: The world record for weightlifting 62kg class shows that 4.0G is the limit.
The limits of humanity as we know it
Other than that, it is said that if you exceed the 5G experienced by fighter pilots, you will faint because not enough blood can be pumped to your head.
"If we assume that it is safe to go below 5G", then out of the 594 exoplanets with known gravitational acceleration,
469 planets seem to be safe for human bones and muscles. But some planets will break your bones when you arrive.