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Tau Ceti e is possibly a good candidate for colonisation as it has a yellow dwarf sun like earth. But it's mass is estimated as >4.30 ± 2.1 of earth. (See Wiki) I remember from a documentary that the people building the foundations for the Manhattan bridge suffered delirium and bleeding from ears an nose due to being subjected to high atmospheric pressure. Atmospheric pressure aside, I'm wondering if there are more symptoms associated with high gravity alone. The problem I am having with this research is that when Googling it, all the hits are related to Fighter jet piolets who are subjected to high G's for a few seconds during a manoeuvre. I'm wondering about exposure for hours, days or even years.

I'm imagining that the colonists would have high tech exosuits that provide extra strength and support by actively following the wearers movements, as well as extra external pressure like the G-suits that todays fighter piolets wear. Use of these suits may also cause side effects.

Besides symptoms and diseases caused by high G's, I also wondering if there are earth diseases that are cured by high G's.

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    $\begingroup$ The most you are going to get out of a Earth Like Planet in terms of Gravity is about 2x Earth Gravity. The Mass of "Super Earth" all pretty much top out at around 2G even when you make it extremely dense. Any ways, the reason you don't see studies for that is because Multiple G environments isn't something we generally do contiuously, but if you are looking for accurate information for sustained 2G environments which seems to be what you're really asking, the best place to look is for Data on how the body reacts to cars at speeds above 30mph and below 120mph I think... $\endgroup$ – Durakken Feb 16 '17 at 3:51
  • $\begingroup$ The Wiki says that 'Tau Ceti e' is about 4.3 earth masses and 'Tau Ceti f' is about 6.6 earth masses. Both of them are classified as super earths. Gravity is exactly proportionate to mass, correct? Am I misunderstanding something? $\endgroup$ – Lorry Laurence mcLarry Feb 16 '17 at 4:57
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    $\begingroup$ Mass is proportionate, not the same as. A planet with the mass of 1 earth mass (em) 1 earth radii (er) will produce 1G. A planet with 2em with 1er will produce >1G while a planet with 2em with 2er will produce around closer to 1G. Mass is only part of the equation and just about every realistic radius and mass combination of a Terrestrial planet falls no higher than about 2G. You can get higher with unrealistic densities produced from over abundance of heavier elements, but those are pretty much garenteed not to exist. $\endgroup$ – Durakken Feb 16 '17 at 5:07
  • $\begingroup$ @Durakken "How the body reacts to cars at speeds above 30mph and below 120mph" -- Why can that provide data for a higher-g environment? I thought gravity can be simulated by acceleration, not by driving at the same velocity? $\endgroup$ – subrunner Feb 16 '17 at 6:38
  • $\begingroup$ @subrunner true... I was just trying to think of the best set of data we have, but I guess that's obviously wrong... i wonder if we could get a sustained accelleration experiment... Perhaps create a loop that has enough fuel for a day to a week. $\endgroup$ – Durakken Feb 16 '17 at 8:20
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I think, the most prevalent earth disease that can be cured by a 2G gravity, is called "human life".

We do not have any data on sustained high-g environments, but there are several extrapolations that can be made from current earth issues dealing with / caused by gravity.

Skeleton

In higher gravity, breaking bones becomes a lot easier since everything exerts more force. It is not recommended for someone with Brittle Bone Disease to experience such an environment as their bones already break easily when in normal gravity. And I expect that stress fractures will become more common.

On the other hand, Osteoporosis might be slowed down by this. Current pervention / treatment mechanisms already consist of working out to put the bones under pressure so that more bone mass is built / current bone mass is not lost due to age. Higher gravity would help quite a lot with this.

However, 2G will definitely be Not Good for joints. Knee joints especially, since they will have to carry twice the load. The cartilage inside will get worn down even quicker, so you won't have 60-year-olds getting new knee joints regularly, but maybe already 30-40 year-olds.

Spine

Back problems should also become a lot more prevalent than is already the case nowadays.

Since the disks get compressed by twice the weight, they will wear down more quickly, and slip easier. All common current malformation (hunchback, hollow-back, misaligned spine) will cause very severe issues right from the beginning, with things escalating to slipped disks very quickly.

If you want to have any chance at preventing back problems in 15-year-olds already, you will need a very heavy exercise regimen targeting the back muscles specifically.

Cardio-vascular system

This is the primary reason why 2G will probably cure the disease of "human life". Our heart and veins are not built to sustain a pressure necessary to fight 2G until the blood goes up to the brain. Even with compression suits preventing the blood from pooling in the feet (that the colonists would have to wear 24/7 -- and do you have any idea how annoying it is trying to get into compression socks even nowadays, those against varicose veins?) the blood pressure itself will have to rise to give the brain all the oxygen it needs when standing upright.

And high blood pressure comes with its own problems, all of which are already known nowadays.

Sleeping will also become quite a bit less restorative, especially if you are sleeping on your back. Gravity will compress your chest more, and you will probably need a muscle tonus close to being awake just so that you can breathe. Snoring should also become more common in such positions... and Sudden Infant Death too (caused by small babies lying on their stomach and just stopping breathing)

Bed sores (and sores in general) will become more common. They are caused by the body's weight pressing down so hard that some of the skin at the bottom (where the most pressure is) doesn't have circulation flowing for long enough to have cells die off.

Biochemistry

Probably the second factor contributing to the disease cure.

This is what I know the least about, but potentially one of the most insurmountable fatal cause.

I don't think that at 2G there is enough atmospheric pressure for the issue of different absorbtion of oxygen / nitrogen mixes to occur (look at breathing mixes for divers having to dive very low). As far as I know, most of the Brooklyn Bridge Worker issues came from breathing sea-level atmospheric pressure air while working under at least 2 atmospheres of pressure. This you can prevent by giving your colonists the appropriately pressured air.

However, the absorbtion rate of membranes of all kinds will be changed. Maybe not by a lot, maybe by just enough to make sustained life in 2G impossible.

Where are membranes in the body?

  • lungs: absorb oxygen, release carbon dioxide
  • cells: absorb oxygen and glucose from blood, remove cellular waste products
  • nerves: nerve impulses jump from one nerve cell to another by one cell releasing calcium / potassium / ... ions into the gap between nerve cells. Those ions need to diffuse across the synaptic gap to be absorbed by the next nerve cell in the line
  • intestines: absorb glucose, fats, etc. from digested food
  • kidneys: remove waste products from blood

Of course, none of those systems will be destroyed completely by 2G (otherwise, humans would not enjoy rollercosters that much or survive fighter planes or being shot into space). But it would be enough to have them functioning at only 95% efficiency to make life suddenly a lot harder when trying it long-term.

Required Fitness-Level

To be able to live somewhat practically in 2G gravity, every single person requires a fitness-level quite a lot higher than what we have today.

Overweight will become pretty much a non-issue - for one, just moving around and doing nothing will already be quite exhausting. For another, every single pound of weight on you will make life harder. And you will constantly have to keep your muscles in shape if you do not want to have severe back problems 2 years down the line.

If you want to be active in a 2G environment, you can compare the requirements most closely to soldiers carrying a heavy backpack on long marches. But even they can just take off the pack and rest for a couple of minutes, not to mention that they do not sleep with it lying on their chests...

Moving Colonists from Earth to Planet High-g

If you nevertheless want to send your colonists to this planet, you should do one of the following:

  • have the space ship slowly increase its acceleration from Earth-G to High-G during the course of the voyage so that the colonists can give their bodies weeks or months to gradually get used to higher gravity. (since braking also counts as acceleration, negative acceleration, you can keep up the higher gravity until just minutes before landing). Just dropping them on the planet from 0G in space and then hoping everything will be fine and dandy -- doesn't work
  • build a rotating space station in orbit above the planet that can simulate all gravities you need, from High-G at the end of the arm, to Earth-G somewhere in the middle of the arm, to weightlessness in the center. Gives your colonists time to recover from the 2G strain, or to train to take it in the first place

Even so, I am pretty sure that such a high-G environment will heavily stunt children's growth, and raise infant mortality incredibly high (due to the adverse conditions).

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  • $\begingroup$ I'd expect the biggest problem to be for a pregnant mother ( if high g does not cause foetal developmengal abnormality , which is unknown). I would expect infant development after birth to be adaptive, so children would grow shorter and stockier than they would in 1g. $\endgroup$ – nigel222 Feb 17 '17 at 15:47
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Sustained permanence in high gravity would result, after many generations, in stronger leg bones (to support the increased load), lighter and maybe shorter bodies (to decrease the suspended mass) and different vascular system, to pump the blood against the gravity potential and yet don't get a stroke when laying flat in bed.

In a single individual over rather short times it's hard to tell. I have no knowledge of humans being centrifuged for more than minutes or hours.

I have the feeling that, if the acceleration is not so strong that prevents oxygenation of the brain, the body can develop some adaptment like increased blood pressure and stronger muscles like it does when anybody works out in a gym.

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  • $\begingroup$ You can quantify the blood pressure issue. Heart to head is about 60cm. 60cm of water pressure is about 40 mmHg. Double g and blood pressure in your heart will have to rise that much to keep you conscious whenever standing. Survivable but life-shortening. Meanwhile your legs suffer three or four times worse. Can arteries and veins take it? My guess, most folks will die of heart attacks and haemorrages in their 50s if not earlier, much as 200kg obese people do on Earth. $\endgroup$ – nigel222 Feb 17 '17 at 15:57
  • $\begingroup$ By the way if you are selecting your settlers, you want dwarfs. Thick-set, muscular dwarfs. $\endgroup$ – nigel222 Feb 17 '17 at 16:04

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