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

[Ulzgoroth]

Originally Posted by Phantasm

If you're looking for maximum human population effectiveness, maybe a 'Gaia' world is a multi-level ecumenopolis?

That's not really an ecology. The Gaia type worlds have superior carrying capacity (and sometimes other advantages) before you build them up.

[Daigoro]

Originally Posted by Fred Brackin

Anyone analyzing habitability of a binary containing an A0 star has to be looking for a capture situation where that A0 gains a smaller companion that's much older than itself. A A0 spends far too short a time on the Main Sequence for the evolution of Earth-like worlds. The biggest star that might live long enough is something like an F8.

It's hard to say how rare capture situations might be.

I don't think that study was concerned with planetary evolution itself, just whether there were stable planetary orbits inside a habitable zone.

But what's the typical age of a K2? Isn't this a capture situation anyway?

[Daigoro]

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?
A few experiments with much different and much smaller chickens doesn't even come close to saying humans living in high gravities would somehow do better.
Just not buying it as anything realistic. But with all these extraterrestrial hypotheticals, most such suggestions will triggers someone's disbelief.

It doesn't have to make life better, it just has to be within the limits of adaptability so that the greater access to arable land can be fully taken advantage of.

But going to the gym 25% more, reducing caloric intake by 25%, drinking 25% less alcohol or increasing muscle mass by 25% would all be beneficial to one's health. Human body mass can change within an individual by more than 25%, and we can live in temperatures over more than a 25% range of variation- 25% isn't that big a deal in the human condition. Heavy worlders might benefit from greater muscle and bone density, but could face other health deficits that would counteract the effect. But as modern medicine has trouble pinning down a lot of the factors in population longevity, it's hard to predict what the sum effect of high G would be.

[Rupert]

Originally Posted by ericthered

T
The way to counter tidal locking is distance, but then you have to worry about the lifespan of the big star. I don't know if a proper balance between the two exists...

The 'big star' can be a G-class main sequence star, like Sol. The 'small star' can be an M-class dwarf like Barnard's Star, and rather tiny.

In such a case the lowest insolation will be when the small star covers part of the larger star. In the case of Sol+Barnard's Star, at the likely distances involved that'd be about a 4% reduction. The highest will be with both in full view, for L = 1.0004 Sol.

This 4% variation is less than the seasonal variation and will be cyclic and predictable. I see no reason why it would be, in itself, a impediment to habitability.

[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.

[Anders]

Originally Posted by Rupert

This 4% variation is less than the seasonal variation and will be cyclic and predictable. I see no reason why it would be, in itself, a impediment to habitability.

Going from "this will be a Gaia world" to "it will not be an impediment to habitability" is quite a step, though.

[Flyndaran]

Originally Posted by Varyon

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?
...

Are you seriously saying that you think it's not only not damaging but beneficial for a 150 pound human to suddenly weigh 425 in all forms including heavy blood and massive edema?
I am at a loss at how to even begin to respond to that.

Humans do better with intermittent exercise and stress. Intense 24/7 stress does not ever do nice things to the majority of humans. Trial by fire may improves some rapidly and excessively, but more often fire burns people.

If you're trying to create a low population of Halo Spartans, I could maybe agree. But we're talking about baseline humans, not a theoretical sister species or heavily modified version.
Or are we? I think one or two posters seem to be going more for sheer biomass than maximal population and comfort for Homo sapiens.

[Daigoro]

Originally Posted by Flyndaran

But we're talking about baseline humans, not a theoretical sister species or heavily modified version.
Or are we? I think one or two posters seem to be going more for sheer biomass than maximal population and comfort for Homo sapiens.

I've already said that we're talking about an established population that has been on the planet for a number of generations- that's the only way they'd be looking at achieving a population cap. Therefore they've adapted or evolved to the local conditions.

And he didn't say that humans at 2.5G would thrive, but that if these chickens do thrive then an unspecified-higher-than-normal-but-maybe-not-as-much-as-2.5G gravity could feasibly be beneficial to humans.

Originally Posted by Varyon

Higher gravity means doing things are more strenuous - that is, every day tasks result in more exercise.

That's one thing to consider though- the gravity tax on the world's economy. The energy required for moving around and doing anything productive is going to increase by 25% (more if there's a square term involved in work), so food and fuel expenditure will similarly increase. The planet would have to be exceptionally productive to make up for this tax.

[Ulzgoroth]

Originally Posted by Flyndaran

Are you seriously saying that you think it's not only not damaging but beneficial for a 150 pound human to suddenly weigh 425 in all forms including heavy blood and massive edema?
I am at a loss at how to even begin to respond to that.

...is there some reason you think the purported health benefits of high gravity would be expected to kick in 'suddenly'?

[Astromancer]

Originally Posted by vicky_molokh

Greetings, all!

Some of you might recognize the term from MoO2. This is a type of garden worlds that is considered to have an extremely high Habitability - in fact higher than the homeworld. Notably, it's meant to represent the kind of condition that (a) allow a higher population cap for a given TL than a homeworld of the same size provides and (b) facilitates even better agricultural yields than our world's.

So I'm curious:
What should a planet be actually like in order to provide such benefits for us Terrans? For the sake of the experiment, assume that the planet's 'wild' ecosystem is loosely derived from and/or fully compatible with ours. It doesn't matter whether such a planet has been terraformed to such a state artificially, made by sufficiently advanced aliens, or just came about through infinitesimally unlikely luckiness.

Thanks in advance!

One simple possibility might be a better arrangement of landmass for improved climate and proportion of arable land.