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Can the mass of a planet or any object affect the growth of a living thing?

  1. Oct 9, 2008 #1
    Would there be subtle differences or large differences on how a human or any other living creature grows up from childhood to adulthood into old age if that person were raised on a planet like earth vs. a place like Jupiter or the moon? In other words , would the transitions from childhood to adulthood be relatively the same if three different humans grew up on three different planets where there was large mass variation between those planets.
     
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  3. Oct 9, 2008 #2

    Mentallic

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    Certainly.

    The biological structure of the human body is designed for withstanding the force of Earth's gravity. If a human from Earth were thrown onto a higher-gravitational planet, their body would only have the chance to adapt, rather than evolve.
    Noticeably, an adult on Jupiter would be much shorter than the adult on Earth or the moon (assuming the human on Jupiter would survive the intensity). However, if the person on Jupiter just lay down all day and was fed in bed etc. he would be much taller instead.
    The need for muscle-use would be much higher on Jupiter than on the moon since it would be a challenge just to move around. resulting in higher muscle-mass growth, testosterone levels and bone density. The opposite happens in lower-gravity situations.
    Fluid in the body becomes heavier, causing strain on the heart so not only do muscles grow, but the organs strengthen too. I would suspect that passing out would be much more common on Jupiter since it would be more difficult to pump blood to the brain, possibly and commonly causing minor brain damage.

    There are probably more effects on growth which I can't think of right now.
     
  4. Oct 9, 2008 #3
    Well, what if a person was strictly raised on a body with a lower gravitational field like the moon? Certainly their would be less strain of muscle mass ; however , now that the muscles of the human body are more loose, would the rate of growth be slower now that there is less pressure of the heart to pump blood into the directed organs?
     
  5. Oct 9, 2008 #4
    There's a problem with bone demineralization in zero-gravity that we haven't solved yet which might also be present under lunar gravity. Here's a generic NASA page about the physiological effects of zero-g, and here's a page on an ongoing experiment on the International Space Station that's examining the development of chicks in zero-g.

    Also, for high gravity environments, it occurs to me that it might be interesting to compare to giraffes, which have unusual vascular systems because they're so tall. Your school library might give you access to this article: An electrocardiographic study of the giraffe
     
  6. Oct 9, 2008 #5

    Mentallic

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    What about human behaviour here on Earth? Compare an athlete to someone that sits all day. The strain on the athlete's heart is obviously more severe, since the muscles are used much more, but this doesn't necessarily mean that the athlete will have a shorter life-span; quite the contrary actually.
    I'm unsure how the lifespan of the humans in each of these gravitational fields will vary, but it is quite easy to imagine the short-term physical effects.

    If these new planets were oxygenated (we could live without breathing apparatus'), the pressure difference due to the altered gravity would have profound effects also.
     
  7. Oct 10, 2008 #6
    Unforgivably poor choice of words! The human body is adapted for Earth gravity.
     
  8. Oct 10, 2008 #7

    Mentallic

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    I have read quite an array of sources that suggest that the 0-g felt in space travel, accompanied by the change in their physical structure are not detrimental until these astronauts return to the 1-g on Earth; so even though I understand that it is an adaption, I still manage to make this error :biggrin:
     
  9. Oct 10, 2008 #8

    Andy Resnick

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    Probably, but we have very limited ways to examine this question. Yes, astronauts lose 1-2% of their bone mass monthly, but there is also decreased cardiovascular performance, immune system performance, and surprisingly, differential gene expression (in plants, IIRC). I haven't seen a clean experiment performed either on embryos or developing animals, so making conclusions is tough. My go-to reference for all this is "Space Physiology" by Jay Buckey.

    OTOH, the lack of radiation shielding on the moon or space station will likely lead to all manner of birth defects (assuming a live birth occurs) which will likely predominate over graviational effects.
     
  10. Oct 10, 2008 #9

    Mentallic

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    Living on a planet like Jupiter would also cause problems due to the fact that there is no solid ground to step on and the toxic atmosphere, constant storms etc.
    I think this question is more of a "imagine if Earth's gravitational pull suddenly changed" type of question.
     
  11. Oct 24, 2008 #10
    It depends. On the moon, that person would be comparatively weaker than the person on earth, because their muscles don't need to work as hard to move about. As for growing up, I'm not sure, but the lower gravity setting might stunt growth or life expectancy in a prolonged state. Living on jupiter would kill you. So yes, mass of the planet matters.
     
  12. Feb 1, 2011 #11
    Does, and/or can, gravity affect the direction muscles grow?.... Here is a silly but relative example to my question: if you exercised your chest and you slept upside down would you develope more upper chest then in normal circumstances?
     
  13. Feb 1, 2011 #12
    Could be. From the point of view of physics, you could get stratification of, say, growth hormones in the intercellular space that changes with gravity. For example, if you have one growth hormone that has an unusually high Svedberg coefficient, you would find more of it in the legs than in the upper body. This should become more and more apparent as you increase gravity.
    On one hand, a human body is usually in motion and that mixes up the fluid in the intercellular space, reducing the concentration gradient. On the other, hormones work in such small concentrations that even if there is one less molecule of the hormone in the region, the effect could be noticeable. This could also explain the decrease in immune performance in 0g Andy Resnick mentioned.
     
  14. Feb 1, 2011 #13

    Pythagorean

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    Even biologists sometimes personify evolution. Physics professors talk about electrons "wanting" to go towards protons. It's convenient to describe behavior in terms of human motivation as long as we don't get too caught up in the analogy.
     
  15. Feb 1, 2011 #14

    epenguin

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    Walking and crawling would get towards the prohibitively difficult. You would have to fly. I think I worked out once that flying would be about as easy as on Earth. You would be heavier but that would be exactly compensated by the increased density of atmosphere giving you more lift. Also I suppose the increased oxygen density would enable a more powerful motor for the same weight.

    That also reminds me that although life in independent evolutions exploited aerodynamics I cannot recall offhand (though something nags me) it ever having invented the balloon or airship, which is odd.
     
  16. Feb 1, 2011 #15

    Andy Resnick

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    Maybe not aerodynamics, but these adaptions occur in hydrodynamics:

    http://www.springerlink.com/content/w50653q02t143271/
     
  17. Feb 5, 2011 #16
    I wonder how digestive tract would change as well, and other features that make use of high gravity or low gravity to minimize energy expenditure. Cappilary action could be even more effective, leading to spindly fibrous plant/fungal life. On the other hand, if you're dealing with 3 or so g's, then swallowing makes the most sense to do upright: always. Squat, nearly sessile vertically arranged life seems very useful in such a scheme, but I doubt we'll know until or unless we see it. Maybe in another life.
     
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