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My colony on Mars is built within lava tubes (for the most part) below the surface. I am assuming that doesn't change the gravity which is at 38% of Earth's.

Let's say this is a well established colony - call it 50 years old. Structures are well built and extensive, many levels below the surface. So there's been time to build whatever infrastructure needed to make things as close to livable as possible.

With gravity at a bit over 1/3 of Earth, it seems normal things like walking/running, maybe even sitting/sleeping become tricky. How might humans compensate to make this easier?

One thing I have seen in both the Expanse and in other stories is magnetic boots that help you stick to floor/ship deck surfaces, giving you a solid push off and landing. Are there other things that might be done? Are there issues with magnetic footwear? Aside from "hand waving" I don't know that there is a way to increase gravity. (I sort of want to avoid that. Interestingly, once again on the Expanse, they seem to move around normally on Mars without any explanation - at least in the show.)

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    $\begingroup$ Mars gravity isn't that drastically dissimilar to our experience of gravity on Earth. It certainly isn't microgravity. We would be able to jump a couple feet higher. Things would take a little longer to fall, over twice as long. I think with humans being the endurance builders that we are, we could adapt to it easily enough. That's is if Mars gravity turns out not to be unhealthy for other reasons. $\endgroup$
    – BMF
    Dec 21, 2020 at 20:48
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    $\begingroup$ If you want simulated Earth gravity, there's no reason you couldn't have all the living quarters mounted on something like a circular maglev track to provide a centrifugal force in addition to Mars' own gravity, could have all the floors be sloped so they are orthogonal to the sum of the centrifugal force vector and the gravitational force vector. $\endgroup$
    – Hypnosifl
    Dec 21, 2020 at 21:49

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Mostly life will be perfectly normal.

At .38g normal day-to-day activities would proceed normally. It is enough gravity to not bother sleeping (it should be more comfortable!), standing, sitting at a desk, eating.
Your paperwork will behave and sit on your desk, your food likewise.
Liquids in open containers will be a bit more unruly (2.5x wave height for same disturbance), but that simply means don't fill your glass of juice to the brim.

Walking at a normal pace should be similar, although you will have a bit of a tendency to bounce more than wanted. Also, due to having the same mass but only 38% the weight, traction will be less than expected. Walking would be something like walking on a linoleum floor with socks on. A bit slippery, but nothing unmanageable. And ignorable if you wear the right shoes.

However, once you start getting energetic, the lower gravity will be bothersome. On Earth, a vigorous standing jump might lift your feet 1 meter. On Mars, that same jump(same starting velocity), will take your feet up to 2.63m Which is a problem, unless you make your ceiling 4.7m above the floor!!

Also, traction for running will be a big problem, unless you prepare for it with suitably grippy shoes, at all times. Even then, expect people to tip over running around a corner much more, and use their hands to stabilize when turning or stopping in a hurry.

With everything having the same mass, but only .38 gravity, you will be able to lift quite a bit more. Pure "lifting strength" will appear to be more than twice as great.

Unfortunately, .38g is not quite low enough to make human-wing flying possible. Sorry.

Stairs: Stairs will be interesting.
The lower gravity makes going up stairs very easy, and they could be quite steep indeed.
But, the reduced gravity will make going down the same steep stairs very problematic.
We already experience a bit of this on Earth, where it is immensely easier to trip going down steep stairs than up. Reduced gravity will make the pain of falling less, but the likelyhood much greater.

Possible alternatives: (speculation, really)
Moderately steep rampways, instead of the terraced stairways we are used to?
Possibly with the "down" lane being just a slidespace?

Or the extreme version of this: Up stairway is a ladder, you ascend on arm power.
Down stairway is an oldfashioned fireman's pole, possibly with a friction-controlled hand strap?

Health impact:

Due to the lower gravity, your muscles and cardiovascular system will not get the routine exercise it needs. The problem is not nearly as bad as on a zero-g station, but you will still need to adhere to a strict exercise regiment to maintain good health. There should not be any real long-term debilitating problems, but frankly at this time we just do not know, it is one of the things that can only truly be tested by doing, not studying the problem.

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  • $\begingroup$ Wow, I had no idea - this is helpful. It sort of sounds like some kind of special shoe is needed. My colony is designed with wide stairways. My idea was not only to not overly rely on mechanical lifts, but to provide exercise while moving around the colony. Lifts would be for longer trips. But it sounds like going up and down might be a little tricky. $\endgroup$
    – MajorTom
    Dec 21, 2020 at 20:58
  • $\begingroup$ Interesting stairway ideas. I need to think about that. It's a primary thoroughfare and needs to allow for crowds as a factor. The pole is a fun idea, not sure how practical. I think you are on to something having a different down lane. $\endgroup$
    – MajorTom
    Dec 21, 2020 at 22:20
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    $\begingroup$ Resistance training wouldn't be impacted that much (you just user heavier weights). Stationary cardiovascular like recumbent bikes and rowing machines wouldn't need to change, but upright bikes, steppers, ellipticals, and treadmills would have more problems. $\endgroup$
    – Keith Morrison
    Dec 22, 2020 at 0:03
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As the Moon landing has shown, using the words of Aldrin and Armstrong, hopping is a much more efficient way of moving than walking. I guess the same work also on Mars, which is halfway between Moon and Earth in terms of gravity.

For short distances the astronauts found they could walk fairly normally. As soon as they sped up, they were unable to sustain a walking motion. "It's not like an earth run here, because you are taking advantage of the low gravity," said Apollo 11 commander Neil Armstrong [Reports11b, 77]. Apollo 11 lunar module pilot Buzz Aldrin added, "You can't move your feet any more rapidly than the next time you come in contact with the surface. In general you have to wait for that to occur" [Ibid.].

NASA originally proposed a "kangaroo hop" whereby the astronauts would hop with both feet and then land with both feet. Aldrin found this to be very awkward and unnatural. The "lope" (as Armstrong named it) turned out to be a good compromise. This is the characteristic Apollo stride whereby the astronaut puts one foot in front of the other, pushing off with one foot and landing on the other foot, but not separating the feet as in a normal walking stride.

Magnetic boots won't do much for simulating gravity: they might give a stronger adherence to a suitable surface, but won't hold the rest of the body any stronger. I guess they would feel like walking with boots stuck in the mood: the feet are heavy to lift, but the rest of the body is as light as normal; therefore I guess they would actually make it easier to trip and fall.

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    $\begingroup$ The main reason why hopping works so well on the Moon is that walking in those suits does NOT work well at all. It required several times less muscle power to flex the knees and hop, than to scissor the thighs and attempt a normal walk... Later studies/simulations show that absent the spacesuit resistance and mass, the more efficient locomotion on the moon would be a partially hunched over(to reduce center of mass) shuffle, with minimal foot lift and loooong strides. The sort of movement that one does when in a pool, that is just shallower than your own body length. $\endgroup$
    – PcMan
    Dec 21, 2020 at 20:59
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    $\begingroup$ Just put on your bunny ears, and hop-hop-hop! :) $\endgroup$
    – Alexander
    Dec 21, 2020 at 22:22
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    $\begingroup$ Aldrin makes a good point, and it's also relevant to superhero speedsters. When you run, you can't go any faster while you're in the air and waiting for gravity to get you back in contact with the ground, which isn't going to happen any faster than a normal runner. The fastest superspeeders are going to be speedwalkers, who are always in contact with the ground. Moving in low gravity will be the same thing. $\endgroup$
    – Keith Morrison
    Dec 22, 2020 at 0:07

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