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PostPosted: Tue Oct 13, 2015 7:50 am 
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Hi all - I need to pick your brains again.

SF games tend to ignore differing gravity on other planets (as does most SF telly like Star Trek and Doctor Who). Or they have a minor penalty imposed – say folk from microgravity habitats are at -20% to physical skills when in Earth’s gravity. However I was always struck by the part of Kim Stanley Robinson’s Blue Mars, when the Mars born character Nirgal comes to Earth and has all sorts of health problems because he’s not used to the gravity and air pressure. I know that wouldn’t be terribly fun to play out in a game, but I’m still interested in finding out gravity-related science.

So, can anyone answer the stuff below? Or point me at answers? Or speculate wildly?

MEN ARE FROM MARS, WOMEN ARE FROM VENUS
Or to be more specific – here are my questions about sexual dimorphism in size and strength.

Men are physically stronger than women. IIRC men have 13% more lean body mass (muscle and bone) than women. That’s genetic. Possession of a functioning Y chromosome and production of androgens (testosterone etc) for use as actual androgens (instead of for use as the building blocks for oestrogens) gives you that extra oomph in your muscles. Particularly in upper body strength.

So, logically if we colonise Mars, Venus or the planet Bob, the men born and raised there will be physically stronger than the women born and raised there. However, Earth is 1g, Mars 0.37g and – as you all know :D – the planet Bob is 1.25g. Has anyone ever seen any solid scientific speculation about how those differing gravities will scale body strength for men and women?

For instance, it is obvious that if men from Earth, Mars and Planet Bob enter the interplanetary arm-wrestling competition, then Mr Bob will beat Mr Earth who will beat Mr Mars. Ditto Ms Bob beats Ms Earth who beats Ms Mars. But if the Interplanetary Olympic Committee decides that arm-wrestling is a unisex sport, how do things play out? Does Ms Bob beat Mr Earth?

Rabid speculation about any other sports appreciated. Javelin throwing, judo, cross-country skiing, tennis, curling, etc etc.

GENES VERSUS PRACTICE
Also have you seen any speculation on training versus everyday life? Does the buffest beefcake on the Moon (0.16g) who lifts weights every day have a chance in the arm-wrestling? Or will he go home crying because he was beaten by a 7 year old from Earth? The 7 year old, of course just lifts school books and only practices arm-wrestling with other 7 year olds.

I’ve seen it stated in palaeontology stuff that since Neanderthal skeletons are more robust than Homo sapiens skeletons, then the following logically applies: bigger bones = more attachment area for muscles = bigger muscles = they were stronger than us. (And by ‘us’ they include big, butch Cro Magnons who arm-wrestled mammoths for a laugh, not just modern folks who sit in offices all day). I’ve never managed to track down anything that guesstimated how much stronger they were, or if Ms. Neanderthal could beat up Mr Cro-Magnon when he called her ugly and doomed to extinction.

So anyone ever seen anything with actual numbers in it on Neanderthal versus Homo sapiens physical strength?

And wild speculation time… do we need to splice in a few Neanderthal genes to help people live on Planet Bob?

EARTH MEN CAN’T JUMP (or SAFETY FACTORS IN BONE DESIGN)
If you’ve ever seen elephants at the zoo, then you may have noticed that instead of a fence around the elephant enclosure, there is often a concrete moat (with or without water in it). This is because elephants can’t jump. Or trot. Or gallop. They are so big and heavy that if they tried to do any of those feats, the forces as their feet hit the ground would break their bones. Charging elephants don’t run – they just speed walk really, really fast. (Play any of the ‘galloping mammoths’ scenes from the 10000 BC movie to a biologist. Listen to them laugh hysterically).

Plus, elephants are big, heavy and strong – they are very good at pushing trees over, so fences aren’t going to last long… (Note to Tokyo: to keep Godzilla from smashing your city, you just have to dig a moat around it that’s wider than Godzilla’s stride length, and deeper than he can step down into).

Anyway, bones have built in safety factors. You or I can safely take a run up and jump over the elephant moat without smashing our bones. However, nature can only do so much, and the poor old elephants have pushed the limit and had running and jumping eliminated from their repertoire.

Sooo… has anyone ever seen calculations involving gravity and bone safety factors for humans? Would we be able to jump in Planet Bob’s 1.25g? Or IIRC 2300AD had a planet called King with 3.0g – what about there?

Stephen Baxter’s Icebones novel has mammoths on Mars. Can they take up jumping again? :o


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PostPosted: Wed Oct 14, 2015 1:37 pm 
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I am not a biologist (but I play one on TV)... but here goes:


strontygirl wrote:
Hi all - I need to pick your brains again.

SF games tend to ignore differing gravity on other planets (as does most SF telly like Star Trek and Doctor Who). Or they have a minor penalty imposed – say folk from microgravity habitats are at -20% to physical skills when in Earth’s gravity. However I was always struck by the part of Kim Stanley Robinson’s Blue Mars, when the Mars born character Nirgal comes to Earth and has all sorts of health problems because he’s not used to the gravity and air pressure. I know that wouldn’t be terribly fun to play out in a game, but I’m still interested in finding out gravity-related science.

So, can anyone answer the stuff below? Or point me at answers? Or speculate wildly?

MEN ARE FROM MARS, WOMEN ARE FROM VENUS
Or to be more specific – here are my questions about sexual dimorphism in size and strength.

Men are physically stronger than women. IIRC men have 13% more lean body mass (muscle and bone) than women. That’s genetic. Possession of a functioning Y chromosome and production of androgens (testosterone etc) for use as actual androgens (instead of for use as the building blocks for oestrogens) gives you that extra oomph in your muscles. Particularly in upper body strength.

So, logically if we colonise Mars, Venus or the planet Bob, the men born and raised there will be physically stronger than the women born and raised there. However, Earth is 1g, Mars 0.37g and – as you all know :D – the planet Bob is 1.25g. Has anyone ever seen any solid scientific speculation about how those differing gravities will scale body strength for men and women?

For instance, it is obvious that if men from Earth, Mars and Planet Bob enter the interplanetary arm-wrestling competition, then Mr Bob will beat Mr Earth who will beat Mr Mars. Ditto Ms Bob beats Ms Earth who beats Ms Mars. But if the Interplanetary Olympic Committee decides that arm-wrestling is a unisex sport, how do things play out? Does Ms Bob beat Mr Earth?

Rabid speculation about any other sports appreciated. Javelin throwing, judo, cross-country skiing, tennis, curling, etc etc.

GENES VERSUS PRACTICE
Also have you seen any speculation on training versus everyday life? Does the buffest beefcake on the Moon (0.16g) who lifts weights every day have a chance in the arm-wrestling? Or will he go home crying because he was beaten by a 7 year old from Earth? The 7 year old, of course just lifts school books and only practices arm-wrestling with other 7 year olds.

I’ve seen it stated in palaeontology stuff that since Neanderthal skeletons are more robust than Homo sapiens skeletons, then the following logically applies: bigger bones = more attachment area for muscles = bigger muscles = they were stronger than us. (And by ‘us’ they include big, butch Cro Magnons who arm-wrestled mammoths for a laugh, not just modern folks who sit in offices all day). I’ve never managed to track down anything that guesstimated how much stronger they were, or if Ms. Neanderthal could beat up Mr Cro-Magnon when he called her ugly and doomed to extinction.

So anyone ever seen anything with actual numbers in it on Neanderthal versus Homo sapiens physical strength?

And wild speculation time… do we need to splice in a few Neanderthal genes to help people live on Planet Bob?


Well, right off the bat, you have a problem. The physical difference between men and women is NOT has great as was previously thought. It is now believed that NUTRITION has more to do with the physical size and strength differences between men and women. In modern Western society, the physical differences are getting smaller and smaller with every generation. Early hunter/gatherers tended to feed men better than women so they became bigger and stronger. Compare a modern American or European woman to a "traditional" asian man. She will likely be physically larger and stronger, mostly due to diet.

In addition to diet, there are the social pressures of body image. Men are expected to be "big and strong" where the ideal of female beauty in most countries is still a slender frame. Women in professional sports fight this problem all the time. The Williams sisters in Tennis have often been criticised for being "too buff" and "not pretty". As a result, most female athletes don't push their bodies to the limit the way many men do.

So, on a light or heavy gravity world, if the nutrition is about the same for men and women, then the effects should be about the same.

It might be an interesting SciFi culture where the female ideal of beauty is buff and muscular and the male ideal of handsome is slender and thin...

Quote:
EARTH MEN CAN’T JUMP (or SAFETY FACTORS IN BONE DESIGN)
If you’ve ever seen elephants at the zoo, then you may have noticed that instead of a fence around the elephant enclosure, there is often a concrete moat (with or without water in it). This is because elephants can’t jump. Or trot. Or gallop. They are so big and heavy that if they tried to do any of those feats, the forces as their feet hit the ground would break their bones. Charging elephants don’t run – they just speed walk really, really fast. (Play any of the ‘galloping mammoths’ scenes from the 10000 BC movie to a biologist. Listen to them laugh hysterically).

Plus, elephants are big, heavy and strong – they are very good at pushing trees over, so fences aren’t going to last long… (Note to Tokyo: to keep Godzilla from smashing your city, you just have to dig a moat around it that’s wider than Godzilla’s stride length, and deeper than he can step down into).

Anyway, bones have built in safety factors. You or I can safely take a run up and jump over the elephant moat without smashing our bones. However, nature can only do so much, and the poor old elephants have pushed the limit and had running and jumping eliminated from their repertoire.

Sooo… has anyone ever seen calculations involving gravity and bone safety factors for humans? Would we be able to jump in Planet Bob’s 1.25g? Or IIRC 2300AD had a planet called King with 3.0g – what about there?

Stephen Baxter’s Icebones novel has mammoths on Mars. Can they take up jumping again? :o


On this one you got me. I don't know of anything like that. HOWEVER, you obviously have not been keeping up on your Monster Movie lore - Godzilla can jump. Quite far actually. He does flying drop kicks against several monsters (horizontally flying too, not in an arc like everyone else). :)

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PostPosted: Fri Oct 16, 2015 3:50 pm 
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Thanks Cyborg IM1 - didn't know that about the nutrition. Read an archaeology paper once that ascribed the drop in human male body size from 'brick outhouse' to 'normal' in the Gravettian (late Palaeolithic) as a switch from hunting big animals with your spear (risky, requires lots of physical strength) to hunting small animals with nets (low risk, clubbing bunnies to death is easy). They found bits of net IIRC. But that drop could also be due to the bunny meat being shared out more fairly!

Have also seen various documentaries about African tribal people where the guys take part in dancing contests to impress the women. They plaster on make-up and look very slender and 'effeminate' compared to the Western 'Greek statue' image of male beauty. Maybe I could use those as my visual image for light-worlders?

I'm still interested in anything anyone has seen on relative strengths of folk raised in differing gravities. Could those 7 year olds really beat the man from the Moon?


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PostPosted: Fri Mar 18, 2016 12:15 pm 
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Another gravity question... can anyone think of any settings (books especially, but RPGs as well) where artificial gravity exists BUT varying gravity on planets is still important to the plot? The kind of thing where you have artificial gravity on your ship, your space station or possibly even your house. But as soon as you nip down the road to the shops or take the dog for a walk you have to cope with the normal planetary gravity.

I'm asking, 'cos I'm coming to realise that many of the books I'm reading seem to think that "We have artificial gravity" seems to mean "We can rock up to Mars and change THE WHOLE PLANET'S gravity to 1g"!!! WTF?

Seriously if you have that kind of technology, why haven't you weaponised it?! Defeat the enemy by turning the gravity of their homeworld up to 11... :-)


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PostPosted: Fri Mar 18, 2016 4:22 pm 
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Bone strength follows a square-cube relationship. The weight increases with the cube of size but the strength only increases with the square of size. So a human can barely get around at about 600 lbs and has a greatly shortened lifespan. Setting average 'Space Marine' man at 200 lbs means that he can walk like an elephant (or 600 lb man) on a 3g world. (His bones will be the same strength for many generations.)

Your elephants cannot do ballet on Mars, but only because their feet and joints are not adapted for that movement. You could, however, breed some 2 ton moose up to 5 ton elephant size so they could leap and prance around Mars.

An interesting Darwinism from heavy worlds: When falling down carries greater risk of death, the population becomes more dexterous. So Heavy Worlders are thick boned and sure footed acrobats ... think Bull Riding Rodeo Stars. :)

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PostPosted: Fri Mar 18, 2016 4:57 pm 
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I think honestly we don't know what the effects of being born in, growing up in, and/or living in higher or lower gravities would be on the human body. The only long-term experience we've had are Earth gravity, and microgravity (for around a year or so) in the space station. I'd imagine that there would be a host of other effects to consider (hormone production, blood circulation, etc) that we just don't know about.

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PostPosted: Sun Mar 20, 2016 1:12 am 
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I'd think there'd be other factors to consider than just an idealized comparison between gravity on muscle mass. As EDG said, our knowledge of what low gravity does to human bodies and when it happens is limited. We don't even have an experience of what might happen if a child is conceived, carried, born, and raised on a world with significantly lower gravity than Earth - or for that matter, if it's even possible.

Like in the arm-wrestling competition, the issue might not even who wins or who loses, but from the theoretical contestant breaking his arm because his bones are so weak due to very low bone density.


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PostPosted: Mon Mar 21, 2016 6:30 pm 
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atpollard wrote:
Bone strength follows a square-cube relationship. The weight increases with the cube of size but the strength only increases with the square of size.


That's interesting. Especially since force output from a muscle is proportional to its cross-sectional area.
I can see a graph in my future... :-)


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PostPosted: Mon Mar 21, 2016 6:37 pm 
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EDG wrote:
I think honestly we don't know what the effects of being born in, growing up in, and/or living in higher or lower gravities would be on the human body. The only long-term experience we've had are Earth gravity, and microgravity (for around a year or so) in the space station. I'd imagine that there would be a host of other effects to consider (hormone production, blood circulation, etc) that we just don't know about.


Yeah, I suspect it is going to get messy.

Gravity is definitely one of the major cues the foetus uses to orient itself head down in preparation for birth. That's going to cause problems in zero-g. And we really want to re-engineer the human spine before we try and live on a high-g world. Quite frankly I could do with mine being re-engineered now! :-)


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PostPosted: Wed Apr 20, 2016 4:56 pm 
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Another low gravity question (not that I’m obsessed or anything). :D

It is a science fiction trope that people from low gravity places (planets like Mars or asteroid colonies) are tall and skinny. Now I totally get the skinny bit. Their muscles will be smaller, their bones will be thinner*. So they will be skinnier than their identical twin who was raised on Earth.

Does anyone know where the ‘taller’ bit comes from? Why would low-g people’s legs and arms suddenly decide to grow longer? Anyone got any ideas?

The only ones I could think of are:
1. Someone decided that each bone has a “quota” of bone to form, and it will transfer “spare” thickness into length as you grow up. I can think of no biological reason why this would be the case - there are probably better ways of storing spare phosphate and calcium.
2. Someone (correctly) thought that you can model weaker muscles by changing the lever length and mechanical advantage of the system. Physics makes a long arm weaker than a short arm, even if they have the same muscle mass powering them. So this version of tall low-g folks has been added to the skinny ones to make tall-and-skinny. Anyone know if this is the case?

Neither of these sound very plausible. Anyone know the history of the trope of tall low-g folks?


*Their body fat will however laugh in the face of gravity. Fat doesn’t have to do any physical work, so it will be working to different rules to muscles and bones. So those Martians and Belters might actually look FAT to outsiders, since they’ll have Earth levels of fat (14% for a healthy Western male, 24% for a healthy Western woman) over skinny low-g levels of bone and muscle.

I’m currently RPing a low-g guy who has body image issues ‘cos Earth men all look so ripped compared to him! Even the ones who sit around in an office all day. :D


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