Specifically if you never go back to regular gravity. Ex: you go to live on another planet with say 3/4 Earth’s gravity and never return to Earth.
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Your neuromuscular system is calibrated for gravity on earth so till it calibrates you would likely be more accident prone than on earth. Some type of calibration take place during critical phases of development and recalibration may not always be possible.
If the gravity is greater than earth your can expect extra wear / tear on your body. Falling even walking in high gravity may be both difficult and dangerous and we may need some way to support our bodies (whales on earth would likely struggle outside water due to gravity vs in water buoyancy supports them).
Your neuromuscular system is calibrated for gravity on earth so till it calibrates you would likely be more accident prone than on earth. Some type of calibration take place during critical phases of development and recalibration may not always be possible.
If the gravity is greater than earth your can expect extra wear / tear on your body. Falling even walking in high gravity may be both difficult and dangerous and we may need some way to support our bodies (whales on earth would likely struggle outside water due to gravity vs in water buoyancy supports them).
The short answer is we don’t know.
The other answers here are mostly talking about microgravity, which is what most people would call “zero gravity” (there are technical reasons for the different name that aren’t relevant here). I.e. floating around, not particularly affected by gravity at all. That’s what they have on the ISS, and there are people who have stayed there for many months at a time, so that gives us decent data on that. Though even then we still don’t know what it’d be like to live there permanently.
We have next to no data about the health effects of lower gravity (that is, still noticeable gravity, but less than 1 g, like you’d have on the Moon or on Mars). We just don’t have a good way to test it. The longest Apollo missions only stayed on the Moon for a few days, and that just wasn’t enough to test it.
We can’t just assume that the health affects would be the same as what you get in microgravity. Lunar gravity and microgravity are not the same thing and there’s no reason to assume the health impacts would be the same.
It’s generally assumed that really low gravity isn’t healthy for long periods, but we currently have no way of knowing where the threshold is and for how long you could stay. Maybe you could be fine in conditions as low as 0.5g, maybe anything below 0.9g is dangerous in the long term. We can’t tell.
This is actually one of the motivations for setting up a Lunar colony–it would give us a way to test this in a way that’s not as high risk as a Mars mission. On a Mars mission, if you found out some serious health issue that would require an astronaut to return to Earth, they’re months away from getting back. On the Moon, it’ll only be a few days before they can get back to 1g. Much less risky.
The short answer is we don’t know.
The other answers here are mostly talking about microgravity, which is what most people would call “zero gravity” (there are technical reasons for the different name that aren’t relevant here). I.e. floating around, not particularly affected by gravity at all. That’s what they have on the ISS, and there are people who have stayed there for many months at a time, so that gives us decent data on that. Though even then we still don’t know what it’d be like to live there permanently.
We have next to no data about the health effects of lower gravity (that is, still noticeable gravity, but less than 1 g, like you’d have on the Moon or on Mars). We just don’t have a good way to test it. The longest Apollo missions only stayed on the Moon for a few days, and that just wasn’t enough to test it.
We can’t just assume that the health affects would be the same as what you get in microgravity. Lunar gravity and microgravity are not the same thing and there’s no reason to assume the health impacts would be the same.
It’s generally assumed that really low gravity isn’t healthy for long periods, but we currently have no way of knowing where the threshold is and for how long you could stay. Maybe you could be fine in conditions as low as 0.5g, maybe anything below 0.9g is dangerous in the long term. We can’t tell.
This is actually one of the motivations for setting up a Lunar colony–it would give us a way to test this in a way that’s not as high risk as a Mars mission. On a Mars mission, if you found out some serious health issue that would require an astronaut to return to Earth, they’re months away from getting back. On the Moon, it’ll only be a few days before they can get back to 1g. Much less risky.
We don’t know, fully. Everything we know about this comes from studying astronauts living in space. Those astronauts, among other things, lost bone density and muscle mass; astronauts have to exercise heavily while in space to be able to even stand when they get back to Earth months later.
More generally, the human body is adapted in *very* precise ways to Earth’s environment. It has no reason, for example, to be adapted to *not* putting stress on your bones and muscles, because a living human will always do that regardless under anything resembling normal conditions.
My favorite example of this is that heavy water (using hydrogen-2 rather than hydrogen-1 in the water molecules) has very very slightly different chemical properties than regular water does. The differences are tiny, and barely noticeable in the lab. But if you drank nothing but heavy water, your cells would malfunction and die because they are tuned to the extremely precise details of exactly how water’s physics play out.
We don’t know, fully. Everything we know about this comes from studying astronauts living in space. Those astronauts, among other things, lost bone density and muscle mass; astronauts have to exercise heavily while in space to be able to even stand when they get back to Earth months later.
More generally, the human body is adapted in *very* precise ways to Earth’s environment. It has no reason, for example, to be adapted to *not* putting stress on your bones and muscles, because a living human will always do that regardless under anything resembling normal conditions.
My favorite example of this is that heavy water (using hydrogen-2 rather than hydrogen-1 in the water molecules) has very very slightly different chemical properties than regular water does. The differences are tiny, and barely noticeable in the lab. But if you drank nothing but heavy water, your cells would malfunction and die because they are tuned to the extremely precise details of exactly how water’s physics play out.
A few examples:
Your heart has evolved to pump your blut up to your Head against gravity. With lower gravity, the blood pressure in some parts of your body will be to high and in others (the legs for example) to low.
Your bones loose density. This leads to them breaking more easily.
Your muscles will reduce, wich further increases risk of injury and this might also increase risk of heart failure or breathing problems.
Your eyes probably will get worse, because they would have higher internal pressure (because of point 1)
Your body will react to the high blood pressure by reducing the total amount of blood cells beeing produced, but this won’t fix the blood pressure problem, but will cause more problems.
In short: people in low gravity will get sick more often, will be weaker (in strength and impunity to sickness) and thus probably won’t get as old.
A few examples:
Your heart has evolved to pump your blut up to your Head against gravity. With lower gravity, the blood pressure in some parts of your body will be to high and in others (the legs for example) to low.
Your bones loose density. This leads to them breaking more easily.
Your muscles will reduce, wich further increases risk of injury and this might also increase risk of heart failure or breathing problems.
Your eyes probably will get worse, because they would have higher internal pressure (because of point 1)
Your body will react to the high blood pressure by reducing the total amount of blood cells beeing produced, but this won’t fix the blood pressure problem, but will cause more problems.
In short: people in low gravity will get sick more often, will be weaker (in strength and impunity to sickness) and thus probably won’t get as old.
A lot of these answers only concern microgravity in space. If we could colonize Mars, it would be a lot different. There would be gravity and I don’t *think* your bones and heart would waste away. You would be lighter and your muscles and bones wouldn’t need the strength they do on earth. I think the Expanse did it pretty good, although I’m not counting the Belters, that’s a bit more extreme. Again that is just my theory so feel free to knock it down.
A lot of these answers only concern microgravity in space. If we could colonize Mars, it would be a lot different. There would be gravity and I don’t *think* your bones and heart would waste away. You would be lighter and your muscles and bones wouldn’t need the strength they do on earth. I think the Expanse did it pretty good, although I’m not counting the Belters, that’s a bit more extreme. Again that is just my theory so feel free to knock it down.
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