Non-Earth gravity

efreysson

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I just realised I haven't given enough thought to gravity on different planets in my space opera setting. I figure that people will mostly settle on worlds with gravity very close to the circumstances mankind evolved in, but I also want some variety.

If Earth-gravity is considered the baseline, (1), then how much more would it need to be on another planet for a person to feel it significantly? 1,1? 1,2? And how much lighter does it need to be for the opposite effect, and for people to move more freely and jump higher?
 

PVick

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Well, for some perspective the moon’s gravity is about 85% that of Earth, which is low enough astronauts can’t really walk normally. Seems like 120% Earth's gravity would feel pretty heavy, even 110% would definitely be noticeable.
 

Myrealana

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Actually, the moon's gravity is about 16% of Earth's.

A gravitation of 120% or so of Earth's wouldn't be too bad. Kind of like perpetually riding up in a fast elevator - that was always going up and never stopped accelerating.
 
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Calder

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You can always try doing some quick and simple maths:

If a planet has 1.25 Earth Gravity, a person who weighs 150 pounds on Earth would feel as if s/he weighed 187.5 pounds. Try walking around wearing a 35 pound backpack. Things would fall faster - at 41.25 feet per sec/per sec. If you could jump 3 feet into the air on Earth, the same effort would only enable you to jump about 2 feet 5 inches.
On a world which has 0.75 Earth gravity, the 150 pound person would feel that s/he weighs only 112.5 pounds, things would fall at a rate of about 25 feet per sec/per sec and the effort needed to jump 3 feet on Earth would lift you 4 feet into the air.

The most important thing I think you'd need to bear in mind that the human body has evolved to work in 1 gee, so prolonged exposure to a different gravitational norm, either greater, or lesser, would be likely to have adverse physiological effects, especially on the heart, which would either be working harder in increased gravity, or "overworking" in lesser gravity. As we know, prolonged exposure to zero-gee (freefall) results in a rapid loss of bone mass and blood volume. The corollary is that the same effects would occur, but over a longer period of time, to those exposed to a permanently lower force of gravity than 1 gee. As yet, the effects of long-term exposure to gravity higher than 1 gee are largely unknown, but, at the least, moving and working in a 1 gee plus environment would be very uncomfortable, with possible cardio-vascular, repiratory and circulatory problems ensuing.

In "The Biology of Human Survival: Life and Death in Extreme Environments", Claude A. Piantadosi says: "Human volunteers have tolerated 1.5g for seven days with no apparent ill effects. However, after just twenty-four hours at 2g, evidence of significant fluid imbalance is detectable. At 3g to 4g fatigue is limiting, and above 4g cardiovascular factors limit g tolerance."
 

Alsikepike

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Inner ears are very sensitive to changes in pressure and gravity since they're filled with fluid. Small changes are easily noticeable if the change isn't incredibly gradual. (i.e.: walking or driving to different altitudes) Especially if you're looking for the change. But, the human body adapts to these changes eventually. At some point people would see it as the new normal. Just like how it's hard to smell your own breath or body odor. When exposed to a constant stimuli, the brain eventually decides it's not worth investigating anymore and shuts it out to help it focus on more important things.

The human body itself reacts in a similar way. Low-gravity environments lead to muscle atrophy and a loss of bone density because the human body doesn't see a reason to spend nutrients maintaining things it isn't using. In the same way, more gravity should result in the opposite, with the body dedicating time to develop more muscles, increasing blood-pressure, and so on. I know I've been rambling, but the point is, people most likely would adapt to their environment rather quickly.

I'm not sure when people would start take advantage of the low gravity, but I found an interesting article by NASA that discusses how all of the lunar astronaut's gait changed as they adapted to the gravity of the moon. Some chose to take long, loping steps, while others used a kind of skipping gait, and some attempted a sort of kangaroo hop, with both feet on the ground at the same time. (Maybe there's a clever idea for some kind of dance routine there?) It might be close to what you're looking for.

https://www.hq.nasa.gov/alsj/a11/a11.gaits.html

There's another one here that's much more complicated, but if you want to know more, it'll certainly help.

https://www.hindawi.com/journals/bmri/2014/547242/