What are the effects of a sudden reduction of gravity ?

[bilateralrope]

Take a group of humans on a moonbase, which includes an artificial gravity system that brings the internal gravity up to that of Earth. What would they experience if it suddenly failed, causing the gravity to instantly drop to that of the lunar surface ?

Are there any other complications they might have until they get used to moving around in the lower gravity ?

[Cykeisme]

What sort of effects are we discussing, in what timeframe? 3 seconds, 30 minutes or 3 weeks?

In the span of a few seconds, there shouldn't be much of a problem unless someone happened to be juuust about to jump or lift a heavy object when the gravity suddenly drops to a sixth of its previous magnitude.

Assuming the moonbase is pressurized (thus people won't be needing to wear cumbersome and bulky spacesuits), in a matter of minutes, I believe most people would figure out how to move around. Inside an "indoor" base, the presence of walls and ceilings would assist with movement.
Within days or weeks most people would get used to moving around and learn to avoid floating out of bed at night etc.

In a matter of months I believe there may be issues with reduction of bone density and skeletal muscle strength, and specialized fitness regiments may need to be instituted.
Someone with better knowledge can probably expound on this.

[Broomstick]

Initially, there may be awkwardness for those in mid-motion such as walking, lifting, dropping, or otherwise performing maneuvers or vertical manipulations. There may be a few bumps and bruises from mis-steps and the like but nothing serious.

A few susceptible people may get a motion sickness-like effect, but it should be very brief and pass quickly. Most folks will most likely not get this. In fact, most folks will probably feel good and "light on their feet" as many things will take less effort. Think of the Apollo astronauts filmed skipping around on the moon singing despite wearing bulky, uncomfortable suits and inhaling a week's worth of BO with each breath, not to mention the unpleasantness of their sanitary facilities and having to eat goo for two weeks and you'll get the idea - this sort of thing will be seen as FUN by the vast majority, especially in a shirt-sleeve environment.

In reduced gravity there is a tendency to "overshoot" when reaching for objects in the environment, but people get past that within minutes. The mind adjusts pretty quickly. Likewise, walking and getting about may be a tad awkward for a bit, but within a day I'd expect folks to adjust, if it even takes that long.

Mid-term, you could get into problems with people forgetting that weight does not equal mass - so someone might lift/move something quite massive (since it doesn't weigh much) but get into trouble because they don't have the strength to control the mass once it gets moving. You could also get accidents due to overconfident people skipping about singing and not paying enough attention to what's going on around them.

As mentioned, long term there will likely be reduction of muscle strength and skeleton weakening, but not as bad as in zero g and vigorous, weight-bearing exercise will help to counteract that.

One sixth Earth gravity, however, is more than adequate to provide up and down references, keep stuff from floating away, and so on so really there won't be that much change in how things are done.

[Simon_Jester]

I have been told that astronauts familiar with trying to do work on Earth, on the Moon, and in free fall (microgravity, like in orbit) prefer the Moon. As Broomstick says, enough gravity that you can put things down and have them stay put, to keep the mind and body oriented in terms of up/down, and so on... but also light enough to make activity enormously easier.

[lance]

Won't something like the bends occur?

[Isolder74]

Won't something like the bends occur?

No. The Bends is caused by a change in pressure on the body letting dissolved gasses turn back into gas inside the blood. A change in gravity would have no effect on the air pressure inside the facility.

[bilateralrope]

Thanks for the quick replies.

[Cykeisme]

I'd definitely enjoy the novelty of bench pressing 500 kilos

[someone_else]

In the long term, low gravity may be a pain for reproduction.
If that is a colony, they may be in deep trouble.
Here an article

[Broomstick]

OK, you do realize there is a significant difference between "microgravity" and "1/6 g", yes? You can't say that because microgravity causes infertility 1/6 g will also do so.

Second, stress alone will cause infertility. In high-stress situations most organisms go into survival mode, and shutting down reproduction is a very common strategy. Space travel and microgravity are both very stressful. Even when humans perceive it as fun, it's still a stress on the body.

The fact that human astronauts have gotten their spouses pregnant shortly after return to Earth, a matter of a day or two, indicates that the human reproductive system may not be as adversely affect as those of rodent. Possibly because, given the humans understand why they've suddenly gone floaty, they don't get as stressed by it.

[Drooling Iguana]

Take a group of humans on a moonbase, which includes an artificial gravity system that brings the internal gravity up to that of Earth. What would they experience if it suddenly failed, causing the gravity to instantly drop to that of the lunar surface ?

The same effects they'd experience if they were on a platform on Earth that suddenly began accelerating downward at a relatively high rate (but not high enough to be in free-fall.)

[Broomstick]

Yes, you get a sense of what it would be like if you're in an elevator that starts going down - that little sort of "lift" sensation? There you go. Not as intense as what you get in the down drop on a roller coaster or those carnival rides involving a drop.

[Gil Hamilton]

I imagine if they were standing up at the time, they might bounce upward slightly, since their leg muscles are tensed to press against Earth gravity and suddenly there is less force to counteract. You've probably experienced this if you taken an elevator from the top floor of a building to the bottom floor.

1/6th gravity is actually a really good gravity to be in for extended periods, if you aren't returning to Earth. I understand it provides enough force to counteract the worse effects of microgravity, like loss of bone mass and circulatory problems. The Lunar environment itself has alot of hard radiation, so your moon colony has to be somewhat buried under the regolith, but the effects of gravity alone aren't that terrible. If you were somewhat elderly on Earth, they'd be fantastic.

[someone_else]

You can't say that because microgravity causes infertility 1/6 g will also do so.

That area isn't a clearly understood one, regardless from what you like to believe.
We need more studies on that to claim anything as "true". Note how I used "may" twice in that tiny post.

And anyway, mice learn how to live and maneuver in freefall just like other animals. I don't see why they should be so "stressed". Plants have much worse problems afaik.

On the other hand, mice don't work exactly the same as us (like the aging mechanism for example), so low gravity may screw up only them.

Still, there is another problem to look on. Gestation may be hampered since the fetus's muscles contraction allows the development of articulations in the right place and with the right shape. If the muscle development is hampered by the low gravity, then articulation and bone development will be screwed up too (ignoring the limited bone mass problem that is a problem only if you want to go on Earth again).

They plan to do tests on smaller stuff like guinea pigs and mice, but I think that if the mass of the species examined increases, the problem should worsen as well.

[Broomstick]

You can't say that because microgravity causes infertility 1/6 g will also do so.

That area isn't a clearly understood one, regardless from what you like to believe.
We need more studies on that to claim anything as "true". Note how I used "may" twice in that tiny post.

Apparently you leapt from my statement to somehow concluding I'm asserting 1/6 g has no effect on fertility. I did not. I stated that you can draw no conclusions of the effect of 1/6 from the effect of 0 g on fertility. We just don't know.

And anyway, mice learn how to live and maneuver in freefall just like other animals. I don't see why they should be so "stressed". Plants have much worse problems afaik.

Mice can learn to swim, too, but they still find it frightening and stressful no matter how good they get at it. Just because they can adapt doesn't mean the circumstances aren't stressful.

Humans can rationalize things, and understand a changed environment, in a way mice can not. You also have to consider that we're primates and may have more capacity to deal with movement in three dimensions than mice do. Do we? I don't know. But if we do it might make zero g less stressful for us.

For that matter, quite a few humans find free fall distressing. Some can't get over it. Needless to say, you won't find such people among the astronauts. The selection process weeds out anyone who can't adapt, and strongly favors those who don't find it stressful. You have to be careful extrapolating from the small sample of astronauts to the other 6 billion or so people alive today.

On the other hand, mice don't work exactly the same as us (like the aging mechanism for example), so low gravity may screw up only them.

Or the way thalidomide causes horrific birth defects in humans but not in rodents. In fact, one of the reason thalidomide was considered safe for pregnant humans is because it was tested on rodents and had no ill effect (actually, it slightly decreases litter size, but you have to track a bunch of pregnant rats or mice to spot the trend). That's why we no longer use animal testing as a model for determining safety of medications in pregnancy - it's not reliable enough.

Still, there is another problem to look on. Gestation may be hampered since the fetus's muscles contraction allows the development of articulations in the right place and with the right shape. If the muscle development is hampered by the low gravity, then articulation and bone development will be screwed up too (ignoring the limited bone mass problem that is a problem only if you want to go on Earth again).

The fetus is suspended in amniotic fluid through most of gestation, essentially neutral bouancy which in some ways is similar to free fall. When the fetus gets big enough that's no longer the case it's pushing against the walls of the womb. So microgravity may or may not be a problem during gestation. It is, I think, very likely to be a problem during childhood. Limbs needs exercise or they don't grow properly. As an example, even though my spouse grew up under 1 g he didn't learn to walk until 9 years old and as a result of lack of use his legs are stunted from that. Walking after the age of 9 was not sufficient to allow him to catch up. This is seen in other children unable to use limbs for one reason or another. Of course, it may not be the only factor. Lack of use isn't quite the same as microgravity.

We just won't know until someone has a pregnancy in orbit or on the moon. I think there is considerable squeamishness to explore these areas with human beings, not the least of reasons being that you could seriously fuck up a living human being along the way.

But if we can't reproduce successfully in 1/6 g - and by that I mean not only conception and successful pregnancy but also childhood development - then we will never have permanent colonies in space. At least not until we have some means to get to another star system within the window of a human woman's fertility. We will remain Earth-bound with only the occasional excursion into space, or colonies that man be permanently manned but will never be independent and self-sustaining.

Well, sure, you could build rotating habitats in space, but then you're dealing with a lot of radiation. The advantage of building on space rocks is that you can easily burrow for protection from that.

[someone_else]

Apparently you leapt from my statement to somehow concluding I'm asserting 1/6 g has no effect on fertility.

Considering how you missed two "may" in a two short sentence post...

The fetus is suspended in amniotic fluid through most of gestation,

What about reading the link I provided? Up to the 21-22nd gestation week the fetus is in conditions similar to neutral floating, while after the 26th gestation week the apparent weight of the fetus is 60-80% of the actual weight.

The point is that womb's walls don't extert same force as gravity, so from 5th-6th month onwards it will feel the lack of gravity.

We just won't know until someone has a pregnancy in orbit or on the moon.

And noone with a brain is willing to try unless we know more. Catch 22.
As usual, we'll wait random unlucky people to fuck up on their own and die/suffer horribly, then learn from their mistakes. It's painful and slow .

Well, sure, you could build rotating habitats in space, but then you're dealing with a lot of radiation. The advantage of building on space rocks is that you can easily burrow for protection from that.

Such radiation can be stopped with a meter or so of packed asteroid dirt. And such weight is also useful to keep the rotation stable while people move about.
Har Har Har! Rotating habitats win over space rocks.

[Darth Tedious]

Did anyone notice this in the microgravity-fertility article?

Tash's research suggests that the reproductive system is at serious risk during spaceflight.

He has studied the effects of weightlessness on earthbound male rats by using a harness to keep their hind legs elevated above the cage floor.

Scientists consider this technique a valid simulation of microgravity.

Are they kidding? I wouldn't think that raising your arse in a harness would be a very accurate simulation...
Will this be a new method of microgravity training? It would deal with few budget constraints!

[Simon_Jester]

You can't say that because microgravity causes infertility 1/6 g will also do so.

That area isn't a clearly understood one, regardless from what you like to believe.
We need more studies on that to claim anything as "true". Note how I used "may" twice in that tiny post.

Apparently you leapt from my statement to somehow concluding I'm asserting 1/6 g has no effect on fertility. I did not. I stated that you can draw no conclusions of the effect of 1/6 from the effect of 0 g on fertility. We just don't know.

Impulsive "She must be wrong, so that I can prove her wrong!" silliness aside...

Broomstick has a good point about all this.

But if we can't reproduce successfully in 1/6 g - and by that I mean not only conception and successful pregnancy but also childhood development - then we will never have permanent colonies in space. At least not until we have some means to get to another star system within the window of a human woman's fertility. We will remain Earth-bound with only the occasional excursion into space, or colonies that man be permanently manned but will never be independent and self-sustaining.

Well, sure, you could build rotating habitats in space, but then you're dealing with a lot of radiation. The advantage of building on space rocks is that you can easily burrow for protection from that.

The radiation is broadly manageable from what I'm given to understand. Even leaving possible solutions alone entirely- not choosing to argue about them- I've heard an interesting idea for cracking the problem from Larry Niven. His hypothetical "Belter" civilization was improbable in a number of respects, but there's at least one thing of interest.

At some point, they hollowed out an actual asteroid, one a few miles across, and put a spin on it. You can do that if you're motivated enough, and they were, because that gave them a 1g environment for women to bear children in and raise them for a few years. The walls were more than thick enough to stop radiation (anything that can penetrate twenty meters, or fifty, or a hundred, of rock would laugh at the Earth's atmosphere anyway), and the spin was (laboriously) built up enough to make the thing an acceptable simulation of Earth conditions, at least along the main floor of the habitat.

"Confinement Asteroid," they called it.

[Lusankya]

Did anyone notice this in the microgravity-fertility article?

Tash's research suggests that the reproductive system is at serious risk during spaceflight.

He has studied the effects of weightlessness on earthbound male rats by using a harness to keep their hind legs elevated above the cage floor.

Scientists consider this technique a valid simulation of microgravity.

Are they kidding? I wouldn't think that raising your arse in a harness would be a very accurate simulation...
Will this be a new method of microgravity training? It would deal with few budget constraints!

My guess is that it would simulate how not having gravity to assist the flow of blood to the testicles would affect fertility.

[Simon_Jester]

Question then is, how accurate a simulation will that give you? Is it common practice to put a mouse's ass in a sling as a substitute for launching them into space? Does this normally produce similar physiological responses?

If not, the experimental results are cast into doubt.

[Lusankya]

Well, it's unlikely to have the same effect on muscle and bone development as actual microgravity, but it seems likely that it would be a reasonable simulation for issues related primarily to the cardiovascular system. Our cardiovascular system is much less good at pumping blood to the lower part of our bodies than it is to the top half of our bodies, since it can rely on gravity to help the blood to get where it needs to go. This assistance is not available in both microgravity and arse-in-a-harness environments.

It seems to me that it's unlikely enough that the non cardiovascular-related effects on fertility from being in microgravity would counteract the cardiovascular-related effect that one could say with reasonable confidence that there is a fertility risk during space flight. Sure, we won't know for sure until we start actually going out and trying to make human babies in microgravity, but the fact that using long-term human data is better than using mice in harnesses is hardly evidence that using mice in harnesses is not an acceptable simulation for some things, when there is no way to get the long-term human data.

[Darth Tedious]

But mice don't stand upright like we do- blood is usually pumped laterally along their body to get to the testes. It's not like blood has a considerable uphill/downhill travel within their body. Unless, of course, they're being held vertically with their tails in the air.
Wouldn't the stress of being trapped in a harness stress them enough to mess with their balls? Particularly if they're hanging, arse-up, from the ceiling...

[Simon_Jester]

Right.

First you'd have to take mice launched into microgravity and compare them with mice trapped with their ass in a sling, to see if putting a mouse's ass in a sling really does have similar effects when it comes to things like cardiovascular health.

Only then could you test the effects on fertility by a cheap substitute methods like putting the mouse's ass in a sling.

...

So help me, I enjoy saying "ass in a sling" in this context. Does that make me a bad person?

[Darth Tedious]

So help me, I enjoy saying "ass in a sling" in this context. Does that make me a bad person?

I don't think it does. But I'm probably biased, seeing as I'm the one who brought up the arses in slings (that sounds great).
But seriously, under gravity (no matter which way your posterior is facing), there are still 'uphill' and 'downhill' directions for blood to flow. In microgravity, there is not. I really fail to see how it's an acceptable simulation.

Getting back on topic for a moment, I couldn't help but picture various amusing accidents while reading this thread.

[Lusankya]

But mice don't stand upright like we do- blood is usually pumped laterally along their body to get to the testes.

That wouldn't necessarily make much of a difference. We've been into space, so in theory we should know the difference between a man's testicular blood pressure in microgravity and and his testicular blood pressure on the Earth. We also know what a rat's testicular blood pressure is. It should really only be a matter of running a bit of maths to determine what angle the rats' arses have to be in order to create the same testicle blood pressure ratio.

Wouldn't the stress of being trapped in a harness stress them enough to mess with their balls? Particularly if they're hanging, arse-up, from the ceiling...

I like to imagine them running happily around in something resembling those carts that you get for dogs with no hind legs, except less ergonomic.