So, let’s imagine someone built a generation ship - or a magic teleporter, or whatever - and sent a bunch of people toGliese 581 c . Happily, it turns out that there is in fact a breathable atmosphere, and water, and all that good life-sustaining stuff. However, it turns out scientists were absolutely right about the planet’s mass - at the surface, gravity is roughly twice Earth’s.
How long could people endure two gravities? I know people take higher g-loads in fighter planes and rollercoasters and such, so it certainly wouldn’t be quickly fatal. But what would the long-term health consequences be like? For that matter, would people even be able to operate normally? Walk, run, and so forth?
Well, There’s really no hard answer for this because we have no good ways of testing it. It would put a lot of stress ont he boyd but we simply don’t know how effectively we can compensate for it. IIRC, bones should get denser in higher G, but the age of the subject would affec this a lot. And the heart may simply not be able to grow strong enough to continously fight the effects of gravity - or the heart might be fine but the veins can’t take the additional pressure.
I find it hard to believe that it’s cause no long-term problems, but the severity of those problems are far beyond the abilit of science to predict with certainty.
Of course people here on Earth manage a doubling of their body weight all the time, granted not all at once. So I imagine given enough time to adapt, we’d be able to at least develop muscles to physically move around and the like without being in a constant struggle.
But yea, I can’t really think of any RL situation that would’ve allowed us to see longterm effects of higher G. The only thing I can think of that would be somewhat analogous is astronauts that have spent long periods on the Mir readjusting to 1g after being weightless for so long.
Not necessarily. In some ways the situation would parallel obesity in loading down the body, though without the internal effects of layering fat on the organs. For example, I weighed ~ 230 lbs. in high school, and I now weigh ~ 370 pounds (yeah, I know ). So I am effectively living with 1.6 times the body weight I had, or as if I were in a place with 1.6 G. And while I can’t say it’s fun, just carrying the weight is not killing me either. I can still walk around and function normally, though I certainly can’t run like I used to.
Of course, 1.6G is not the same as 2.0G, and were my weight to go to 460 pounds, I might have some really serious issues. But I am sure I would still be able to move around. I suspect large, strong people like myself would in general have fewer problems carrying the extra load.
But probably a bigger problem would be atmosphere. A planet with twice the gravity of Earth would tend to compress air, making it very hard to build an enclosed space and pressurize it.
I’m not sure it would be the same as becoming morbidly obese on Earth. If you double your weight on earth your heart still requires something similar to the same effort to get blood from your feet to your brain. If you double the force due to gravity then your heart would require substantially more effort to get blood to your brain (I assume double the effort, but I’ll let someone that knows the relevant physics better than I do confirm that). I also wonder what it would do to your lymphatic system over the long term since it doesn’t have the benefit of the heart to move the lymph around.
Has anyone ever stuck animals in a centrifuge for very extended periods of time? That’s the only way I can think of to test what would happen (and even there I would remain a little dubious if four footed critters were used for testing - there’s less lift required if you’re essentially horizontal then if you’re vertical).
So if the people sent to Gliese 581 c adapted to the increased gravity and started having babies that developed muscles, hearts, bones, etc. that were efficient in the doubled gravity, what would those people be like if they visited earth? Would they be able to jump really high, say, leap a tall building in a single bound? Would they be viewed as super men and women?
Would they have a hard time walking in earth’s gravity, like astronauts on the moon?
Some googling reveals that NASA does indeed have a centrifuge that they use for exactly that purpose. They’ve apparently kept rats at 2g for up to a year.
So far as I can find, the main effect was that the rats ate less leading to weight loss, but they apparently did survive for the length of the experiment. I couldn’t find much more then short little blurbs though, so perhaps someone can dig up more info.
Astronauts on the moon don’t have a hard time walking. They have a very easy time walking. It’s just that the easiest way to walk on the moon looks different than what we’re used to.
The Glieseians would have somewhat of an advantage over us, but not a huge one. That planet is 1.6G, not even 2G. You could imagine them doing 60% greater feats than the average earth person, but we already have athletes who can do 60% greater feats than the average earth person. A really trained Glieseian could do 60% greater feats than that, which would be impressive, but hardly super.
It’s worth noting here that all we know about this planet is its mass. Assumptions about surface gravity are tied to assumptions about diameter which are tied to assumptions about composition. The 2 g value is if it is a rocky planet.
That said, I agree with Lizard that, in terms of just walking around, the effect on your joints would be comparable to being severely overweight. You can build up your muscles over time but your knees and ankles can only support so much force.
Another consideration would be the increased likelihood that a simple trip/fall would result in broken bones. It might be different in subsequent generations (assuming we colonized). I remember reading Clarke’s passages in 2001 about children born in lunar colonies growing up under 0.17 g and passing 6’ in their pre-teens…
Man, someone coming from that planet to Earth would be at half gravity. Combine that with the fact that they had a red sun and …wait a minute! I have heard this before!
Canadjun correctly points out the heart of the problem. Gravity would put an extra strain on the circulatory system all by itself, an effect not equivalently mimicked in obese people.
I suspect we’d see a lot of folks develop hypertrophic cardiomyopathy as the heart built up extra muscle mass (not a good thing, due to the structure of the heart) trying to always pump against a heavier load everytime one raises their head higher than their heart.
Heart failure would be more common and far more debilitating, heart attacks that are minor and only damage a small bit of muscle in our own gravity field would be more devastating in a setting where the heart had to continue to pump so much harder, there’d be more problems with episodic loss of consciousness due to sudden drops in blood pressure from rapid standing up or mild dehydration.
The cardiovascular system is designed to function in a 1 g environment, and lengthy time in a 2 g environment would lead to a myriad of systems failures, IMHO.
You’re assuming an equivalent oxygen percentage in the air (which seems reasonable). But at 1.6g, the atmosphere would be at a higher pressure, and might contain more oxygen per cubic meter – the same phenomenon experienced by Denver athletes in Miami, for example. If the air has more oxygen, then the blood doesn’t have to move as quickly to accomplish its mission, and the heart can continue pumping at its accustomed volume & speed. Think this would offset the effects any?
On a related ntoe, I considered my previous post. I think the veins and arteries would have one heck of a time managing this. Bloodflow will tend to get pulled down to the feet but pumping up the brain will take a heckalaciously strong heartbeat. Even if the heart doesn’t fail, the pressure waves would be murder on your cardiovascular system. Average pressure might not increase, (gravity pulls it down more easily) but I think the highs and lows of the system would be much greater, leading to blown veins during any increase of heartrate.
What if the travelers wore G-suits, or even just G-suit pants, for a fraction of the day? I’m thinking of doctrine changes here, where explorers with desk jobs are given beds instead of desks, tilted at 30 degrees or so to approximate 1G. Maybe rotate duties between who has to walk around, so that for the first few months the astronauts are only standing and walking when absolutely necessary, and the one or two people who spend lots of time walking get G-suits to alleviate the bloodflow issues.
If they can bring their ship with them planetside, they could pressurize its atmosphere and achieve the high-O[sub]2[/sub] atmosphere I mentioned above, too. I’m sure there are other equipment and doctrine changes you could add to stack the deck in our travelers’ favor.
I’m not sure about this. How much of the effort of the heart goes to fighting gravity, and how much is just pumping the blood through the resistance of the whole system?
As for air pressure, that would also depend on how much air there is. There could possibly be more gravity, a smaller atmosphere and the same pressure as Earth.
If memory serves, one of the major causes of fatal car accidents is tearing of the aorta due to sudden deceleration. It seems to me that this would be a major problem in a higher g environment than what we’re used to. Am I right?
). So I am effectively living with 1.6 times the body weight I had, or as if I were in a place with 1.6 G. And while I can’t say it’s fun, just carrying the weight is not killing me either. I can still walk around and function normally, though I certainly can’t run like I used to.