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(Machine translation by DeepL translate)We've been experimenting with gravity that is 10 times stronger than the Earth's (=10G).

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I wonder how much gravity we can actually withstand.

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Gravity (strong)

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Gravity (Stronger)

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First, let's examine the strength of bones.

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Let's assume that the entire body weight is supported by a single leg.

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The tibia bone has a cross-sectional area of 1 cm2 and can withstand up to 1730 kg.

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Even if the gravity increases 10 times, the bone will not break.

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If the gravity becomes strong enough for a 50kg person to reach 4680kg

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In other words, if gravity becomes 94G, your shins will shatter under your own weight.

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This is for a stationary person.

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But if you run, the stress on your bones will only be doubled at most

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If you don't get knocked down, the problem is weakness of the muscles, not fractures.

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Let's think about standing up from a sitting position.

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You use your knee joint as a fulcrum to lift yourself up with your quadriceps muscles.

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The magnitude of the torque "r1×F" (×2) must be greater than the torque "r2×Mg" that gravity pulls the body to stand.

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If we substitute the average value, gravity must be less than 1.1G

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In other words, the earth's gravity is the limit for standing by muscle strength alone.

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Force F is proportional to the cross-sectional area of the muscle, so if you stand up at 10G

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the cross-sectional area must be at least 9 times larger.

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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

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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%.

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Realistically, the limit for a trained person to stand up would be 5.3G.

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Next is the limit of gravity when walking.

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Let's consider the following model of walking

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An inverted pendulum moves forward with the feet as its fulcrum.

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The center of gravity moves up and down. The pendulum moves efficiently by exchanging kinetic energy and potential energy.

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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.

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This is the limit of a person's strength, calculated by a walking model.

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When you don't carry a log, you know what the limit of gravity is.

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If you increase the gravity, you will not be able to walk at 4.6G

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Reference: The world record for weightlifting 62kg class shows that 4.0G is the limit.

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The limits of humanity as we know it

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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.

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"If we assume that it is safe to go below 5G", then out of the 594 exoplanets with known gravitational acceleration,

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469 planets seem to be safe for human bones and muscles. But some planets will break your bones when you arrive.