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View Full Version : What human adaptations would be needed in high, low, or zero gravity?



Noclevername
2011-Oct-05, 03:08 PM
Eventually, as humanity starts colonizing space, the majority of worlds we'll encounter or build will be unlike our own. We know that there are many Super-Earths, low gravity moons/dwarf planets, and microgravity asteroids and nonspinning structures. We can also assume that humanity will start to tweak its own design. What specific biological changes to the human body would be needed to adapt to any one of these three types of gravitational environments? What systems would need to be altered, and how?

As a follow-up question, could a human body be redesigned to thrive in two or more, or all three, of these gravity levels?

IsaacKuo
2011-Oct-05, 03:49 PM
We simply do not know. Life on Earth has evolved to live in 1 gee of gravity. While temperatures, pressures, and atmospheric composition have varied, gravity level has not.

At this stage, we know some physiological problems with living in zero gee, and have some limited data on effects of high gravity...but not nearly enough to know long term effects and what to do about them. We have practically no data on the effects of low gravity.

BioSci
2011-Oct-05, 04:03 PM
Eventually, as humanity starts colonizing space, the majority of worlds we'll encounter or build will be unlike our own. We know that there are many Super-Earths, low gravity moons/dwarf planets, and microgravity asteroids and nonspinning structures. We can also assume that humanity will start to tweak its own design. What specific biological changes to the human body would be needed to adapt to any one of these three types of gravitational environments? What systems would need to be altered, and how?

As a follow-up question, could a human body be redesigned to thrive in two or more, or all three, of these gravity levels?

Other than Sci-Fi, hand-waving, pseudo-scientific, or "just-so" descriptions, we do not have any realistic idea how humans could be re-designed to cope well with altered gravity conditions. This is unlikely to change in the foreseeable future.
The genetics and regulation of bodily structure and function is highly complex. To actually solve such complex design issues would require a great deal of experimentation - much of which would be unethical!

Swift
2011-Oct-05, 04:49 PM
Other than Sci-Fi, hand-waving, pseudo-scientific, or "just-so" descriptions,
Even science fiction is pretty inconsistent with regard to this. There have been numerous authors who have speculated that humans born in lower gravity environments (such as on the Moon or Mars) would not be able to survive on Earth (or would do so with great difficulty), whereas other ones have assumed it would be no problem at all.

KhashayarShatti
2011-Oct-05, 06:31 PM
Eventually, as humanity starts colonizing space, the majority of worlds we'll encounter or build will be unlike our own. We know that there are many Super-Earths, low gravity moons/dwarf planets, and microgravity asteroids and nonspinning structures. We can also assume that humanity will start to tweak its own design. What specific biological changes to the human body would be needed to adapt to any one of these three types of gravitational environments? What systems would need to be altered, and how?

As a follow-up question, could a human body be redesigned to thrive in two or more, or all three, of these gravity levels?
Yes. Your question is scientific but my answer is not with mainstream. I don't know how to discuss about it. However your very nice question is similar to migration that will end up with evolution. Harsh conditions both on earth and outerspace may one day force us into a process of survival that may end up with a kind of variable physiology. I think it is similar to a kind of teaching process in which body and brain learn how to be or become an adaptive control system. The only thing we need is a rapid kind of teaching and learning process between body and environment equivalent to a slow evolution process similar to a rapid process from babyhood to adulthood the theory of which already exists in body(slow process).

SkepticJ
2011-Oct-05, 07:46 PM
By the time "humans" do any sort of serious colonization of space, I don't think biology is going to be much of a concern, having been left behind for bodies made of carbon allotropes, ceramics, metals and polymers.

Noclevername
2011-Oct-05, 09:20 PM
By the time "humans" do any sort of serious colonization of space, I don't think biology is going to be much of a concern, having been left behind for bodies made of carbon allotropes, ceramics, metals and polymers.

Perhaps some will, assuming that it's even possible. But all? No, there's going to be some old fashioned H.Sapes around for a good long time-- and expansion is a biological imperative, so why would post-bios be interested in it?

swampyankee
2011-Oct-05, 09:35 PM
I suspect that reasonably close to 10 m⋅s -- probably 10% or so -- no special adaptations will be needed. Other regimes? Time to get some animal models up there: a few generations of lab animals on ISS should give some hints. For higher accelerations, there's always Great Mambo Chicken (http://www.amazon.com/Great-Mambo-Chicken-Transhuman-Condition/dp/0201567512).

SkepticJ
2011-Oct-06, 02:32 PM
Perhaps some will, assuming that it's even possible. But all? No, there's going to be some old fashioned H.Sapes around for a good long time-- and expansion is a biological imperative, so why would post-bios be interested in it?

Maybe not all, but I suspect most will, since the bodies could be better in every way.

Probably because post-biological entities would still be physical, and have physical needs like energy, space, and would be susceptible to dying if they are destroyed by an energetic environment (asteroid impact, expanding red giant star . . .)

IsaacKuo
2011-Oct-06, 02:44 PM
Non-biological entities would be more interested in expansion, I would think. The costs for space expansion are lower due to the reduced infrastructure and transit mass requirements, and the benefits are greater due to the greater population that can be supported for a given amount of matter or energy. In other words, non-biological entities would get more bang for their buck.

Also, biological entities may still have limited lifespans, so the time requirements for space travel may be a serious barrier to space expansion. Non-biological entities with no aging limitations would not suffer from this barrier.

OrionTheory
2011-Oct-06, 02:57 PM
According to a conference I just attended, even artificial gravity by spinning a ship wouldn't overcome the effects of low gravity on our bodies enough to keep us alive on a long distance mission.

IsaacKuo
2011-Oct-06, 03:20 PM
That's utterly ludicrous. According to Einstein's theory of relativity, it would be impossible for our bodies to tell the difference. While it's certainly plausible that less than 9.8m/s/s spin gravity may not be enough, 9.8m/s/s is definitely enough.

The only question is what minimum spin radius is necessary to prevent undesired effects from spin.

KhashayarShatti
2011-Oct-06, 03:48 PM
What happens to a stone or a piece of iron at low g or high g? Nothing. What happens to a spring at low g or high g? Nothing. So the best way is to increase tensile strength of body or flexibility. Blood can circulate at high pressures. If someone weighing 80Kg can withstand 10g the total force on him at 10g is 800kg. I think If the operating point is moved to 5g with a tolerance of+/-5g(10g to 0g) then reducing it to 0g won't harm body structure. I wonder what will happen if we make body tough in comparison with a rotating device?

Hornblower
2011-Oct-06, 04:28 PM
According to a conference I just attended, even artificial gravity by spinning a ship wouldn't overcome the effects of low gravity on our bodies enough to keep us alive on a long distance mission.

Let me expand on Isaac's remarks. Whoever said that clearly does not know or understand the principle of equivalence. It does not matter whether the body is subjected to gravitation while bearing against a stationary surface or is being pushed centripetally by a rotating enclosure in the absence of significant gravitation. The mechanical loading of the various body parts is the same either way.

OrionTheory
2011-Oct-06, 04:45 PM
That's utterly ludicrous. According to Einstein's theory of relativity, it would be impossible for our bodies to tell the difference. While it's certainly plausible that less than 9.8m/s/s spin gravity may not be enough, 9.8m/s/s is definitely enough.

The only question is what minimum spin radius is necessary to prevent undesired effects from spin.

According to the speaker I heard (and I don't remember the name of the scientist, I apologize), he quoted that even at very fast speeds all that would happen is we would get sick from the spinning even if it DID serve it's purpose and were spun fast enough.

SkepticJ
2011-Oct-06, 08:12 PM
According to the speaker I heard (and I don't remember the name of the scientist, I apologize), he quoted that even at very fast speeds all that would happen is we would get sick from the spinning even if it DID serve it's purpose and were spun fast enough.

Depends on the diameter of the rotating vessel. The smaller the diameter, the worse the Coriolis is, which is what would make you sick by screwing with your inner ear.

IsaacKuo
2011-Oct-06, 10:01 PM
According to the speaker I heard (and I don't remember the name of the scientist, I apologize), he quoted that even at very fast speeds all that would happen is we would get sick from the spinning even if it DID serve it's purpose and were spun fast enough.
It doesn't matter who the speaker was--either he is wrong or you heard him wrong (or both). There is nothing about very fast speeds which would make any difference whatsoever.

The only issue is spin radius, because a large spin radius allows for a slow spin rate.

baskerbosse
2011-Oct-07, 12:24 AM
Perhaps liquid immersion could be used in high-G places?
Combined with a perflourocarbon breathing apparatus, you should be alright?
Unless the perflourocarbon is too dense..?
-Living in a fish tank. ;-)

Don't know about long term effects though.

Peter

KhashayarShatti
2011-Oct-07, 09:25 AM
.... What specific biological changes to the human body would be needed to adapt to any one of these three types of gravitational environments? What systems would need to be altered, and how?.....
One possibility could be to develop hard and flexible bones with high modulous of elasticity with tough and flexible tissues surrounding them. For a hundred year life duration creep will not be so crucial at low g if we allow the height of a person to change by 5cm. Also a kind of white skin with compounds of silver and glass similar to a mirror can protect skin from low and high heat conditions. Obviously a variable blood pressure and blood flow control system would be highly effective.
To some extent fish tank at high pressure resolves creep at low g but i don't like this kind of development.

HenrikOlsen
2011-Oct-07, 09:39 AM
It doesn't matter who the speaker was--either he is wrong or you heard him wrong (or both). There is nothing about very fast speeds which would make any difference whatsoever.

The only issue is spin radius, because a large spin radius allows for a slow spin rate.
From what I've read other places, it looks like we'd be OK balance wise if we spin it at less than about 1 rpm, which, if we want 1G and solve for r, gives a radius of about 90m (300 feet). If G is enough, 45 m would be enough. If we want to be certain and go for rpm 369m radius will be needed.
For practical building it looks like the rotation speed tolerable rather is a hard design constraint, as the radius needed starts to grow very fast after the 1 minutes per rotation level.

HenrikOlsen
2011-Oct-07, 09:41 AM
One possibility could be to develop hard and flexible bones with high modulous of elasticity with tough and flexible tissues surrounding them. For a hundred year life duration creep will not be so crucial at low g if we allow the height of a person to change by 5cm. Also a kind of white skin with compounds of silver and glass similar to a mirror can protect skin from low and high heat conditions. Obviously a variable blood pressure and blood flow control system would be highly effective.
To some extent fish tank at high pressure resolves creep at low g but i don't like this kind of development.
Creep? What do you mean with creep?

And your proposed skin has higher heat conductivity so it wouldn't protect at all against extreme temperatures.

Trebuchet
2011-Oct-07, 03:16 PM
For a sci-fi speculation on the topic, see Larry Niven's The Integral Trees (http://en.wikipedia.org/wiki/The_Integral_Trees). One of my favorites.

Noclevername
2011-Oct-07, 05:14 PM
The only problem with Niven's solution for low/zero g is that it required centuries of natural selection and a very high rate of infant mortality and deformities. (I still agree that the book and its sequel are great science fiction)

Niven also created the Jinxians in his Known Space universe, adapted to a high-g planet. "Doc" Smith did it first. In fact heavy-worlders are fairly common in scifi, either naturally adapted or genetically engineered.

swampyankee
2011-Oct-07, 10:26 PM
All the SF tends to make high-g humans shorter. This probably makes sense, from a static point of view, but since when we're walking or standing still, we are essentially inverse pendulums, the combination of being shorter and higher gravity will increase our natural frequency, which may, at some point, make bipedalism impossible.

In other words, there are two competing tendencies here: shorter improves the static stresses on the heart and skeleton, but it also worsens the dynamic control issues involved in standing and walking.

Noclevername
2011-Oct-08, 01:32 AM
All the SF tends to make high-g humans shorter. This probably makes sense, from a static point of view, but since when we're walking or standing still, we are essentially inverse pendulums, the combination of being shorter and higher gravity will increase our natural frequency, which may, at some point, make bipedalism impossible.

In other words, there are two competing tendencies here: shorter improves the static stresses on the heart and skeleton, but it also worsens the dynamic control issues involved in standing and walking.

Some SF heavyworlders are portrayed as large hulking figures-- including Smith's Valerians and the genetically-enhanced Diplo heavyworlders from Anne McCaffrey's Planet Pirates universe. On the TV show Andromeda, Kevin "Hercules" Sorbo was a heavyworlder.

It seems likely that heightened balance and fall reflexes would be traits needed for high-G adapted humans.

IsaacKuo
2011-Oct-08, 08:02 AM
Remember that no one was born six feet tall. The balance problem needs to be solved for toddler heights anyway.

Noclevername
2011-Oct-08, 02:00 PM
Remember that no one was born six feet tall. The balance problem needs to be solved for toddler heights anyway.

Thicker legs, larger feet and stronger bones (more rapidly increasing skeletal strength and density at a younger age), perhaps some form of subcutaneous padding, and a broader stance would all help.

swampyankee
2011-Oct-08, 02:44 PM
Remember that no one was born six feet tall. The balance problem needs to be solved for toddler heights anyway.

Toddlers do fall down a lot. This does not tend to be a real problem (although it most certainly does upset parents) as toddlers very rarely break anything when they fall down from standing up or from a modest height (indeed, it's rare enough so that a toddler brought into a US emergency room with a broken bone will almost always trigger a call to the agency responsible for dealing with child abuse). This may not be the case for a toddler in a high-g environment.

KhashayarShatti
2011-Oct-08, 04:37 PM
Could this be a possibility?
http://www.newscientist.com/article/mg21128324.400-improve-your-vision-with-an-app.html
Perhaps a kind of closed loop feedback control system where the command is "teaching" and feedback is "learning.
Brain has got everything. It is ready to accept your algorithms to change as you like. How rapid can you make it?
Which way is the most efficient?

Sorry HenrikOlsen. Creep is a terminology in metallurgy engineering.

Noclevername
2011-Oct-12, 02:11 AM
Short humans would minimize the force needed to pump blood to the brain, thus lessening the stress on the cardiovascular system under high G.

hlanus
2014-Jan-04, 12:06 AM
To survive in high-gravity, we would need a skeleton and musculature that would be strong enough to counteract its pull.
We would also need a differently designed circulatory system. A giraffe is an excellent example: it has an asymmetric heart in that the left side's wall are much thicker than the right, enabling it to produce very high blood pressure while not being much larger than a horse's heart. It also has valves in its blood vessels that stop blood from back-flowing. To protect the brain when they bend down, the blood vessels branch out into a "bush" of arteries to reduce the pressure before they reach the brain (very relevant if you want to pick something up in high gravity). Finally, to prevent blood from pooling in their legs, they have VERY thick skin to keep the arteries and veins under a set pressure. (I watched a documentary called Inside Nature's Giants, where some people dissect large animal specimens for study and a giraffe was one of them.)

Noclevername
2014-Jan-04, 02:22 AM
Welcome, hlanus. You're certainly dusting off an old thread here!