Artificial gravity -- consequences for the human body

[Daniel Travis]

Hey all,
*this is my first post on this forum*
I've read a lot about the different ways of artificial gravity on this forum, and we've discussed everything from realistic ideas that can be accomplished with today's tech, all the way to fictitious situations in sci fi books.

BASICALLY, I would like to discuss the consequences of artificial gravity on the Human Body...

What's the difference between regular (earth) gravity VS. a spaceship using, say, Centripical force (ship is big enough where a person does not change the CF) ON THE HUMAN BODY? (or any other forms of AG)
* I apologize if this thread has already been created. I haven't read ALL the threads on this forum...yet :) *

 

[Bandersnatch]

What's the difference between regular (earth) gravity VS. a spaceship using, say, Centripical force (ship is big enough where a person does not change the CF) ON THE HUMAN BODY?

Providing the magnitudes are the same, i.e. 1g, then there shouldn't be any difference. There's nothing inherently special about one as compared to the other - in both cases they're merely causing the floor to push on the soles or your feet (or your bum, or whatever), and that's all biology cares about as far as gravity is concerned.
There do exist some subtle differences (e.g. the appearance of the Coriolis force), but I don't see how that could affect anything in the human body.

Now, if the magnitude of artificial gravity is different than Earth's 1g, then it's another matter, and we can talk about either microgravity or high-gravity environments. Although in the latter case it would have to be mostly speculative.

 

[Daniel Travis]

Right on Bandersnatch. I thought they were inherently the same , but I had this feeling like I was missing something important. I guess I was thinking too hard about it. But you made perfect sense, if both types of gravity are 1g, then there shouldn't be a difference.

As micro gravity goes, aren't the effects mainly muscle atrophy and internal organs/systems would slowly fail due to the difference in pressure? or am I thinking too hard about that too.haha

 

[GTOM]

The ship should have a large enough radius (100m for start) so humans wouldn't feel serious tidal forces, motion sickness.

Is there any little bit based speculation, what Mars like gravity could do to human body? It is far from microgravity.
What if people became really tall and thin?

https://hu.wikipedia.org/wiki/Robert_Pershing_Wadlow

I guess they could suffer like him on Earth gravity, unless they artificially enhance heart and legs.

 

[rkolter]

As micro gravity goes, aren't the effects mainly muscle atrophy and internal organs/systems would slowly fail due to the difference in pressure? or am I thinking too hard about that too.haha

They get puffy. They lose bone mass. Reduced red blood cell count, difficulty recognizing up from down and identifying where their limbs are at any given time. On return, difficulty maintaining balance and stability, blurry vision and low blood pressure upon returning to Earth.

There are a lot of articles out there. I just took three at random from the first results page on Google:

https://www.scientificamerican.com/article/how-does-spending-prolong/
http://sen.com/news/spaceflight-health-issues-being-studied
http://www.space.com/23017-weightlessness.html

 

[jackwhirl]

...difficulty recognizing up from down...

According to some reference frame? Or is it an inner ear thing?

 

[jim mcnamara]

Cochlea problem and proprioception to a lesser degree.
Study on mice (pdf attached)

Edit: oops you might not know proprioception - https://en.wikipedia.org/wiki/Proprioception

The study was done in reduced gravity, I believe. The ISS has approximately 89% G (acceleration due to "pseudo-gravity")- as an example.

 

[berkeman]

The ISS has approximately 89% G

But because it's free-falling with that acceleration, the net effect is weightlessness, right? Except for during the occasional orbital adjustment maneuvers.

 

[mfb]

Is there any little bit based speculation, what Mars like gravity could do to human body? It is far from microgravity.

Just speculation. Animals (including humans) would probably get taller there, with a lower bone density and potentially weaker muscles. How much? No one knows. Somewhere between the effects of zero-g and 1g, but we don't even have good data of mammals growing up in zero-g.

 

[jim mcnamara]

@berkeman
NASA claims 90% - see https://www.nasa.gov/audience/forstudents/5-8/features/nasa-knows/what-is-microgravity-58.htm
Maybe I am reading wrong - but the example given is: a 100lb human on the space station weighs 90lbs. It is called reduced gravity or microgravity.
I do not know any more than what studies and articles have said.

 

[mfb]

The force between a human and Earth is m*0.9g. But that force is irrelevant. The human accelerates towards Earth at nearly the same rate as the station does. As a result, you don't notice this force at all. You feel weightless on the ISS. It is called "microgravity" because it is not exactly zero - friction leads to a tiny backwards acceleration of the station but not the astronauts inside, and the different center of mass of the station and the astronauts leads to a tiny effect of tidal gravity. All these things are negligible for humans - less than 0.001 g, and that is the number that matters.

 

[jackwhirl]

Just speculation. Animals (including humans) would probably get taller there, with a lower bone density and potentially weaker muscles. How much? No one knows.

Do animals grown completely in microgravity end up permanently longer than Earth-bound control specimens?

 

[mfb]

I'm not sure about longer, but cockroaches seem to be fine - they grow faster and they even profit from the zero-g environment.

 

[.Scott]

The ship should have a large enough radius (100m for start) so humans wouldn't feel serious tidal forces, motion sickness.

I believe that works out to a period of about 20 seconds. Better stay away from outside views.

 

[mfb]

20 seconds should be fine. Cars make faster turns than that.

 

[.Scott]

20 seconds should be fine. Cars make faster turns than that.

But cars don't challenge the notion of what is down or stationary. Some people are more sensitive than others. There's a restaurant about half an hour from me that rotates 360 degrees per hour. That's too much for some people.

Looking out a window at a planet and stars that are tracking circles at 3 times per minute will be a problem for a lot of people - perhaps at least until they become acclimated.