How High A Gravity Can Men Survive In

[SaxonViolence]

This seems more a Biology Question than a Space Problem.

 

First though, let us spend a few moments contemplating the life of the Grossly Obese.

 

Here's a man who ought to weigh maybe 205 pounds--maybe 215 pounds at very most--yet he weighs 480, maybe 500 pounds.

 

Now while many folks this Obese aren't, our test case is still fairly mobile. He's walking several miles daily, trying to lose weight. He can get up from a chair without assistance. He cooks his own meals; plays with his Dogs; and maintains a fairly large Garden.

 

Granted, his joints will begin to fail eventually. He's likely to die young, from a Heart Attack, Stroke, Cancer--something.....

 

But not before he passes his Genes on to a half-dozen children.

 

Lets call him "Abel". Abel had an identical twin named "Cain".

 

While Abel stayed on Earth and got Fat, Cain embarked on a mission to Colonize a New World. Only there was a glitch, and they don't find out until too late that the Gravity is like 2.14 Gees.

 

Like Abel, Cain also weighs about 500 pounds on his Bathroom Scale--But he has a very minimal 8% Body-fat; a Physique many Bodybuilders would envy; and would weigh about 215 on that same scale on Earth.

 

Isn't Cain abusing his body less than Abel?

 

Cain's heart doesn't have to pump blood to 260 pounds of Surplus flesh. Cain's weight is always well-centered, none of it hangs in a huge sack around his waist, constantly pulling him off balance. Cain has no trouble tying his own shoes.

 

Cain's blood isn't chock-full of Fats, Triglycerides and Excess Sugar and whatever.

 

It just so happens that the atmosphere on Cain's World is noticeably thicker than the atmosphere of Earth--and also a bit richer in Oxygen too--percentage wise.

 

The Pioneers never intended togo back to Daniel Boone days. As new homes are built, chest deep pools become a fixture in even the poorest homes. When the day's work is done, Cain's people take the load off by spending much of their home hours seated while partially submerged.

 

They learn to make excellent beds too.

 

They call Earth, and give them the Low-Down. All future Colonists will be selected from men and women who could have been champion Power Lifters, Strong Man contestants or Pro NFL Linemen.

 

If Abel and his equally Obese Spouse could both live into their late 50's and get around reasonably well to the very end--and have five children (and believe me, it happens); Why shouldn't Cain, who is living so much healthier, last at least that long, and have as many children?

 

And given the very Tough Screening, and Harsh Natural Selection--It would be interesting to come back after five generations; fifty generations; five hundred generations.....

 

But the real questions I want to pose are:

 

Just exactly how high can we push the Gravity, and suspect mankind to be able to cope and survive?

 

And what kind of adaptations, Biological and Social, would you expect?

 

Saxon Violence

Edited March 28, 2012 by SaxonViolence

[Turtle]

...

But the real questions I want to pose are:

 

Just exactly how high can we push the Gravity, and suspect mankind to be able to cope and survive?

 

 

 

All About G Forces

[CraigD]

This seems more a Biology Question than a Space Problem.

...

While Abel stayed on Earth and got Fat, Cain embarked on a mission to colonize a New World. Only there was a glitch, and they don't find out until too late that the gravity is like 2.14 Gees.

...

Just exactly how high can we push the Gravity, and suspect mankind to be able to cope and survive?

I agree, this is a biology, specifically an anatomy and physiology, question, and a hard one. :thumbs_up Modeling this sort of thing based on theory is daunting, and doing it experimentally unethical for folk opposed to torturing wee animals to gain answers that provide no clear benefit to man nor beast, and I can’t imagine will until we’re actually faces with a scenario like Cain’s high-G colony world.

 

Sensibly enough, in your post, you focus on the effects of added weight on Cain’s musculoskeletal system and heart. This is not, however, from where I think the most critical trouble would come.

 

My main worry is that the constant increased G force would overwhelm the ability of gas exchange membranes in Cain’s lung alveoli and other capillary blood vessels, allowing fluid to accumulate in many body cavities, critically the lungs interior and the lung and hear cavities, a condition that, if not relieved by drugs and surgical drains, leads to death. Even with constant drugs and had permanently implanted drains, I worry that infection and constant slight trauma to these capillaries and cavities would kill him before he’d lived very long on his high-G world.

 

Physical strength can’t solve this problem, nor can the pseudo weightlessness of whole body immersion in liquid, because the liquid supports only Cain’s gross anatomy, not individual molecules in his blood.

 

I’d also worry that the increased G force would interfere with the release, fertilization, implantation, and development of ova into babies, making it impossible for the women on Cain’s world to conceive and give live birth.

 

I’m wildly speculating here, so my worries may be unfounded. Short of something like stuffing unfortunate mice in lab centrifuges, running them at various speeds, and microscopically examining their dead bodies, I can’t think of an easy way to know if they are or not. I’m not gonna do that, even for hypography – I like mice!

 

And what kind of adaptations, Biological and Social, would you expect?

Biologically, I’d expect selecting for stronger muscles, sturdier load bearing joints, and perhaps stronger vascular membranes to overcome to trouble I describe above.

 

Socially, if reproduction is possible, but its success rate very low, I’d expect a social emphasis on it, and stronger valuing and protection of children.

 

Since the speed reached in a fall of a given distance increases with the square root of the increased G factor, I’d expect the folk of Cain’s world to have more of an aversion to high places without sturdy railings, recreational climbing, jumping and flying – in short, I’d expect them to be literally more “down to earth” than we are, and for acrophobia to be more widespread.

 

Combining these, I’d expect it to be a world where a kid could get in really deep trouble for climbing trees. ;)

[SaxonViolence]

I love this Forum. B)

 

 

All I have to do is put out a well-formed Question, and pretty soon all sorts of mind-expanding stuff comes in.....

 

Factors that I never considered. :blink:

 

Saxon Violence.

[maddog]

CragD makes a good point on limitations. One I could comment on is the data from NASA. In their centrifuge tests they found that for a short time astronauts could sustain about 8-9 g's before passing out (some only up 5 or so). For longer term studies I not know anything above simulating about 2 g's (even that was only for a week or so).

 

On the flip side, would living in a world of a 1/3 of Earth's gravity lengthen one life span? The heart would not be as stressed.

 

On Skylab, Mir and the International Space Station, it has been discovered that even an extreme ritual of exercise does not completely equalize anatomical breakdown of tissues due to a micro-gravity or zero-gravity environment. So what is not know is if a third might be good for you, then how low done does it begin to not be good? A 1/10 maybe?

 

Lastly are there other life forms on earth that can sustain higher or lower gravitic forces than human beings. I do not know if this has been studied.

 

maddog

Edited April 10, 2012 by maddog

[CraigD]

Lastly are there other life forms on earth that can sustain higher or lower gravitic forces than human beings. I do not know if this has been studied.

Animals without differentiated, organized tissues– organs, circulatory and musculoskeletal systems, etc. – are able to withstand much higher gravity-like forces than more organized ones, including ones like humans. Labs routinely separate bacteria and other microorganism in body fluids with lab centrifuges that produce one the order of 10,000 g for 5 or more minutes, without noticeably hurting the bacteria.

 

I don’t know if anyone has ever experimented to find the force and/or duration of force that will hurt various microorganisms, as it’s hard to imagine how this would be very useful – once you’ve gotten them out of the body, killing microorganisms is easy using heat or simple chemicals, and clearly you can’t use such high forces to kill them in vivo without killing the big, fragile animal they’re in.

 

I’ve never heard of anybody testing it, but I’d guess that fish and other animals that live in and are suffused with liquid similar in density to their tissues are more g-force tolerant than air-breathers.

[SaxonViolence]

CragD makes a good point on limitations. One I could comment on is the data from NASA. In their centrifuge tests they found that for a short time astronauts could sustain about 8-9 g's before passing out (some only up 5 or so). For longer term studies I not know anything above simulating about 2 g's (even that was only for a week or so).

 

On the flip side, would living in a world of a 1/3 of Earth's gravity lengthen one life span? The heart would not be as stressed.

 

On Skylab, Mir and the International Space Station, it has been discovered that even an extreme ritual of exercise does not completely equalize anatomical breakdown of tissues due to a micro-gravity or zero-gravity environment. So what is not know is if a third might be good for you, then how low done does it begin to not be good? A 1/10 maybe?

 

Lastly are there other life forms on earth that can sustain higher or lower gravitic forces than human beings. I do not know if this has been studied.

 

maddog

 

I read in an article about O'Neal Colonies, that the consensus was that 1/5th or 20% of One Gee, would allow one to live healthy without undue tissue deterioration (assuming healthy amounts of exercise) indefinately.

 

Don't remember the source, nor how they could possibly determine such a thing.

 

I've also read that some scientists still hope for a drug, or combination of drugs, that would simply tell the body to halt its de-conditioning in low gravity.

 

I've heard that sleeping in low gravity might be extremely restful.

 

Suppose for a moment, that I'm a hard working manual laborer, or hard--very hard--training athlete--on Earth.

 

Artificial Gravity has been invented, and is even cheap--go with me on this.....

 

Every night I go into my sleeping chamber and turn my Gravity down to 20%, and sleep 7.5 to 9 hours--depending on how tired that I am.

 

What is everyone's best guess what this will do to my body long-term?

 

Saxon Violence

[maddog]

Suppose for a moment, that I'm a hard working manual laborer, or hard--very hard--training athlete--on Earth.

Artificial Gravity has been invented, and is even cheap--go with me on this.....

Every night I go into my sleeping chamber and turn my Gravity down to 20%, and sleep 7.5 to 9 hours--depending on how tired that I am.

What is everyone's best guess what this will do to my body long-term?

I will make a guess, if you saying this individual will be basically day-to-day existence in two gravities...

In MHO, I think this could cause long term side effects. Not so much because of two gravities.

It would be specifically the transition each morning from low gravity back to normal. I think

you be getting up "unrefreshed".

 

Maybe if the differential in gravities was smaller; say at night was 1/3 or 1/2, day was 2/3 or 3/4, such that

the difference was less than a 1/2 g. This may be adaptable.

 

maddog

[CraigD]

I've heard that sleeping in low gravity might be extremely restful.

 

Suppose for a moment, that I'm a hard working manual laborer, or hard--very hard--training athlete--on Earth.

 

Artificial Gravity has been invented, and is even cheap--go with me on this.....

Despite being trained from an early age (STTOS, etc) to accept it as a future fait accompli, I’ve gotta draw the no-go line on artificial gravity – not the routine pseudo-gravity of centrifuges small and large, but the kind that can decrease the force of gravity in a stationary room.

 

This pseudo-technology is a space opera film staple, driven mostly by practical production considerations – it’s hard, technically, to simulate low or micro-gravity on even a major movie, let alone a TV series, budget. Trying and doing a bad job of it (obvious wires, etc) kills realism far worse than not attempting it at all.

 

However, to the best of my knowledge – and, though an amateur, I’m a fan of the subject – there’s no legitimate scientific justification for expecting to be able to either “shield” against gravity to reduce it, or create it other than the usual way, with huge masses.

 

Unlike increasing gravity-like force with a centrifuge, there’s no way to “pseudo” reduce gravity in a reasonable small space near Earth’s surface. The only way to do it is have some sort of vehicle descend at around the rate of a falling body. Roller coasters with vertical drops of 60 m or so can manage something like this for around 3 sec. Airplanes like NASA’s famous “vomit comet” DC-9 can give about 25 sec, but need 2500 m of altitude and essentially a sky full of maneuvering space to do it – beyond what I’d call a “small space”.

 

So, if you want a true reduced gravity sleeping space, the only feasible scheme looks to me to be to have it in space – orbiting a big body, or sitting on a small one.

 

Because we have fairly lone, flat bodies, to a large practical extent, simply lying on a horizontal surface grants most of the benefits of sleeping in reduced gravity, by relieving the heart of the burden of moving as much blood vertically. Though, personally, I can’t tell much difference between them and a good ordinary mattress, waterbeds are pretty close to the completely even pressure you’d get sleeping submerged in water.

 

How much, if any, benefit sleeping in true reduced gravity would offer over simply a good bed, I don’t know. ISS astronauts do it a lot, reporting mixed positive and negative effects vs. ordinary earth-bound sleep. They tend to have a harder time falling asleep, and difficulty sleeping as long as they’d like. However, it’s possible the shortened sleep duration is due to their sleeping better, or “faster”, possibly because of reduced force on their lungs, resulting in fewer breathing irregularities, resulting in turn in a faster “recharge time”. Breathing irregularities, from full-blown sleep apnea to snoring, are believed to account for many problems in sleep quality, and are almost completely eliminated in the ISS’s microgravity.

 

(Source: Sleep in Space Flight: Breath Easy—Sleep Less?, 2001, David F. Dinges, American Journal of Respiratory and Clinical Care Medicine)

 

I’ve personal, anecdotal (not properly controlled scientific experimental, but from a variation on the old folk hangover remedy) experience sleeping while breathing with a trickle of pure oxygen, that reminds me a bit of the shortened sleep experience Dinges reports for the ISC astronauts.

 

The ISS nominally maintains Earth surface normal O₂ and other air gas levels at sea level pressure, so the reported shorter sleep durations shouldn’t be due to increased O₂, but, as Dinges’s paper explains, due to reduced gravitational force on the lungs.