Super-Earths' powerful gravity could preclude alien civilizations from leaving their planets

The biggest problems would be biological as the decreased/increased gravity took its toll on every system in the body. We humans would likely be dead within a decade of just being in orbit. Thus an artificial gravity space station makes more sense than planetary colonization.

 

I read some estimates on humans surviving on larger planet I can't recall the exact figures for human survival with a earth+ gravity...I believe it was two weeks at 1.25% earth mass, death from massive internal organ failure...

 

Yeah I have read that as well, I cannot remember where...but the same article stated that limited exposure (4 hours per day) could push the survival rate to 25%. So there would need to be a space station. Also it was inferred that young children that were in development stages would have a survival rate of possibly 40%.

This is all conjecture on scientist part, they are estimating from the loss of muscle and bone density of astronaughts that are on the space station for any length of time.

 

and this is there home and they're helpless with the return to gravity that their bodies evolved in...imagine being on a carnival ride with constant G force for two weeks, the effect on the brain would be devastating, our brain evolved with our gravity so it's neutral here, an increase of weight would be lethal in a short period from the compression(I can't imagine the headaches that would accompany it)...then there is the circulatory system, the extra effort required by our heart to pump the extra weight of the blood constantly would be of limited duration...

 

LOL an where did this estimate come from and had there been even short term studies as in week or so with large centrifuges?

Some people carry very large amount of weight around in fat in fact more the 25 percent over ideal body weight for decades.

25 percent increase G killing someone in a matter of weeks seem nonsense on it face.

 

Let see the mass of a sphere and therefore it Gravity at any given distant from it center would go up with the cube of it diameter and it surface area go up with the square of it diameter.

Then assuming no change in density you would need to factor in the square of the surface distant from the center also.

Not all that simple of a problem and I would need a few hours to figure the relationships out at least.

 

The gravitational acceleration constant on the surface of a planet is roughly proportional to the two-thirds exponent of its mass, assuming equal density.
(that's basically the cubed root of the square)

That's because gravity is proportional to mass, but the increase in radius is the cubed root of the increase in mass, and the gravitational force is inversely proportional to the square of the radius.

Estimated mass of the planet Mars: 6.39 × 10^23 kg
Estimated mass of the planet Earth: 59.72 × 10^23 kg
Gravitational acceleration surface of Earth: 9.807 m/s²
Gravitational acceleration surface of Mars: 3.711 m/s²

This isn't exactly a perfect example, since Earth has a slightly higher density than Mars.

Estimated density of Earth: 5.514 g/cm3
Estimated density of Mars: 3.93 g/cm³

Wikipedia states it even more simply and says the surface gravity of a planet will be approximately inversely proportional to the square of its radius.
https://en.wikipedia.org/wiki/Surface_gravity#Mass,_radius_and_surface_gravity

Thus, a planet that has a radius 50% larger will have a surface gravity 2.25 times greater. ( 1.5 squared equals 2.25 )
Or a planet with a radius twice as large will have a surface gravity 4 times greater.​

 

Not taking into account any increase in distant between the surface of the planet and the center an increase of ten times the diameter would increase the mass by not ten times and not a hundred times but a thousand times repeat a thousand times.

Let see distant from center to surface would go up by five decrease the G force by 25 times so the surface G should be around one thousand/25 or 40 Gs or forty times the earth weight of a human.

 

No you would still need to take into account the distant between the center of the planet and the surface and that would be a square relationship.

 

Any one interested in the subject of super size planets and the possible life on such planets might find a hard science novel by Hal Clement by the title of Mission of Gravity interesting.

 

not up on biology are you laughing boy....carrying 25% extra weight or more of fat isn't the same as those parts like the brain weighing more due to the constant pull of gravity... it doesn't matter how fat you are your brain and organs aren't bigger or heavier our gravity has no effect on our organs.... it can be difficult to comprehend but take a year or two and think about it...or spend a couple days on centrifuge and let us now how you feel...

 

I suggest thinking on a wholeistic scale in this, as in the entire system referred to as a human body. Consider just the eye and what happens to an astronaut in low G.
https://www.nasa.gov/mission_pages/station/research/experiments/1038.html

Imagine high G effects on the heart.

 

Well my friend the human brain is floating or at least supported to a large degree in a liquid call the Cerebrospinal fluid so a steady g increase force is far less likely to harm the brain then other parts of the body.

Once more a 25 percent increase in weight ie g forces is hardly likely to do serous harm over a short time period to a health person.

Laughing boy indeed and I am indeed laughing thanks to your last post.

 

Twenty five percent should not be consider high at least in my opinion.

Hell the maximum g force a human body had survive without harm was over 42 g for a few seconds at least

https://www.medicaldaily.com/breaking-point-whats-strongest-g-force-humans-can-to

As for myself I had cheerfully survive around 7 G when a chute open fast on me.

Yes I know all this is for very short periods of time but once more a 25 percent increase seem very very small to do any real harm to a human in normal health in a few weeks time.

 

A minute, second, or weeks are irrelevant when considering long term effects, which is what is in discussion. You may have enjoyed the 5 seconds of G force exhilaration but would have likely died after an hour of it as your heart began to fail and blood no longer reached your brain. Your body has evolved in one G and does well there, ANY change in this has effects and these compound over time...the result is inevitable failure and damage.

 

OK no human study had been done to date but rats had survive for two rat generations under 2.5 repeat 2.5 G not 1.25 G.

Once more a 25 percent increase seem far far too small to harm any human in normal health in a few weeks time.

http://www.descsite.nl/Publications/Papers/vanloon_jgp-2001-8-1-139-142.pdf

footnote the time period on a few weeks for human harm up to death was given in a post that I was responding to but given that I had found that rats had breed and live their lives for two rat generations under 2.5 G I can not see a reason why humans are not likely to survive for very long periods indeed at 1.25 g without meaningful harm.

 

Neat...rats dont get fat in high G's after a couple months....I stand corrected.

 

rats aren't on the same scale as humans and the experiment doesn't scale up...would you crawl around like a rat or stand and walk like a human and rats are pound for pound much stronger than we are and being prone is a considerable advantage...the heart will have increased stress pumping blood to the head an upper extremities, standing up could cause you to pass out...breathing will be more difficult as lungs will have extra stress and then add the extra air pressure...additional gravity isn't as simple as adding additional body weight on earth, adding 20, 50 or 75% additional weight with a backpack doesn't simulate extra gravity, with additional gravity everything inside you is heavier, heart, lungs, brain, eyes, and the stress/load is directly on them unlike carrying a backpack...

 

That was a sarcastic dismissal.

 

I wasn't wearing my sarcasm hat, too subtle for me