[Space] What is the 'Gaia' type of garden worlds like? ('Habitability 9').

[Varyon]

Originally Posted by Flyndaran

Name literally any other natural environmental aspect of earth that can be made harsher by a full 25% that somehow makes human lives better?

I'm not certain I follow this line of argument. There's apparently a study showing that making things 150% "harsher" (in the form of 2.5 G) in a certain Earth species is actually better for them. Is it entirely outlandish that humans might also have a higher gravity at which they will do better?

Consider also what variable gravity is comparable to. Lower gravity means doing things are less strenuous - that is, every day tasks result in less exercise. I don't think anyone is going to argue that exercise is bad for you. To maintain the fitness level of an Earth couch potato, a Mars couch potato will have to add in a workout regimen. To maintain the fitness level of an average Earth man, someone living on a Mars colony would have to walk, jog, and possibly lift weights more often. And so forth. Those who behave just like their Earth counterparts are going to have lower overall fitness.

Higher gravity means doing things are more strenuous - that is, every day tasks result in more exercise. To maintain the fitness level of an Earth couch potato, a Hope* couch potato will have to move around less. To maintain the fitness level of an average Earth man, someone living on a Hope colony would have to walk, jog, etc less often. And so forth. Those who behave just like their Earth counterparts are going to have higher overall fitness.

Now, that isn't saying that lower gravity is necessarily bad for you, nor that higher gravity is necessarily good for you. There are going to be other factors augmenting or competing with the above. For example, a Mars colonist's heart doesn't have to work as hard pumping blood through his body, which means it might not wear out as quickly. A Hope colonist's heart, on the other hand, has to work harder to pump blood through his body, which means it might wear out a bit faster. I don't know for certain which direction variable gravity will skew things, and it's even possible we already live on "the best of possible worlds," at least in terms of gravity (that is, 1G is optimal for humans).

All that said, from what I understand, gravity is an overall negative when it comes to crop growth. If you can get a planet with similar characteristics to the one in the paper (little variation in altitude, denser atmosphere) but at lower gravity, it might be better for plants - the higher gravity of that world was just to get the necessary physical characteristics. And better for plants will mean higher habitability, even if the colonists end up having shorter lifespans.

*I've opted to have Hope in my space opera setting indeed be a planet with twice Earth's mass (and 1.25G). I haven't yet decided if I'll have it orbiting a K-dwarf like in the paper, a yellow dwarf, or something else entirely, however.