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I heard that some scientists placed chickens under 2.5g for 6 months, and they survived.

A normal human would black out at 5g.
A trained astronaut could take up to 8g before blacking out.
20g would kill anyone in a few seconds.

I also heard that an increase in the strength of gravity can result in a partial or total loss of vision. At how many g do these occur?

At how many g would we be incapable of walking? At how many g would we collapse on the ground helplessly without being able to get up?

And at how many g would our body be quickly crushed and flattened like a pancake?

BuildingBetterWorlds
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    Although you ask specific questions, this topic has already been discussed here: http://worldbuilding.stackexchange.com/questions/3291/if-earths-gravity-suddenly-became-stronger-how-would-we-cope – Vincent Nov 14 '14 at 04:29
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    and this: http://worldbuilding.stackexchange.com/questions/158/would-the-human-body-support-living-on-planets-with-a-greater-gravity-than-earth/171#171 – Vincent Nov 14 '14 at 04:30
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    If the question is focussed on what G's humans hit their limits at, I think it's not a duplicate. I really gotta lookup them 2.5g chickens though...sounds like a new KFC product. – Twelfth Nov 14 '14 at 05:31

1 Answers1

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It's late, so this is a partial answer. Let's first consider the effects of long term low gravity, which are better known, and see if we can work backwards.

Low gravity has lots of subtle, nasty effects on humans, including loss of bone density, leading to brittle bones, and loss of muscle mass. Additionally, there are negative effects on the cardiovascular system and, at least while weightless, digestion.

Even slightly higher gravity would probably lead to a large increase in muscle, and a consequently higher calorie intake. The subject would also have a dense skeletal structure, as is seen in high-impact martial artists. Some negative consequences might be early-onset arthritis, as with people who wear weight belts and jackets improperly.

Another thing to consider is that small accidents would have more serious outcomes, especially in industry and agriculture. Having a 100 lb bale of hay land on you is no picnic, but having a 150 lb bale hit you is much worse, no matter how dense your bones are. And that's just considering a "mere" .5g increase.

People would probably wear lighter and fewer clothes to avoid encumbering themselves, or overheating. They would likely be more comfortable in colder climates, due to the extra work their bodies have to do just to lift their ribcage. Dehydration would also come up more often, due to people being more prone to sweating. There would potentially be a lower fertility rate, due to the extra strain during pregnancy, a time when the ligaments and joints loosen up in preparation for childbirth.

This is really a short list. Changing gravity long term, even by .1g, would have innumerable little effects on daily life. Hopefully this answer at least gets you pondering.

Emmett R.
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  • As the musclemass grows, the volumen/surface ratio gets bigger and this leads to less energy loss due head-loss. Therefore look at any polar animal and their non-polar friends. (Polabear - any kind of black bear, emporer penguin - Southern rockhopper penguin) The warmer it get's the less they are fat. – jawo Nov 14 '14 at 07:57