I just rolled up the most horrendous "habitable" planet ever.

[Johnny1A.2]

Originally Posted by Ulzgoroth

Without technological support is asking a lot..

Yeah, but I use it for a reason.

In principle, a viable human breeding population could endure indefinitely on Earth without any tools or equipment, just as other animals do. Fantastically difficult, yes, but possible. Allow simple TL0 tools and it becomes a very viable, in pure species survival terms. Earth is the only planet in the Solar System of which this is true.

If technological support is allowed, you have to draw a line to make the definition of 'habitable' mean anything. For a human population with access to high end (only modestly ahead of our own) space-flight level technology and a viable economic/industrial base, most planets are 'habitable'. For such a society, Mercury, Luna, Mars, the major asteroids, many of the big satellites of the gas giants, even the KBO worlds, are all 'habitable', in the sense that viable breeding populations could endure indefinitely on them. For slightly more advanced societies, even worlds like Venus and Io are 'habitable'. Advance the tech a bit more and the gas giants become 'habitable'.

Whether a world is classified as habitable or not depends on the metric.

[Ulzgoroth]

Originally Posted by Johnny1A.2

Yeah, but I use it for a reason.

In principle, a viable human breeding population could endure indefinitely on Earth without any tools or equipment, just as other animals do. Fantastically difficult, yes, but possible. Allow simple TL0 tools and it becomes a very viable, in pure species survival terms. Earth is the only planet in the Solar System of which this is true.

If technological support is allowed, you have to draw a line to make the definition of 'habitable' mean anything. For a human population with access to high end (only modestly ahead of our own) space-flight level technology and a viable economic/industrial base, most planets are 'habitable'. For such a society, Mercury, Luna, Mars, the major asteroids, many of the big satellites of the gas giants, even the KBO worlds, are all 'habitable', in the sense that viable breeding populations could endure indefinitely on them. For slightly more advanced societies, even worlds like Venus and Io are 'habitable'. Advance the tech a bit more and the gas giants become 'habitable'.

Whether a world is classified as habitable or not depends on the metric.

Defining a boolean trait which only ever is false seems kind of pointless though.

[doctorevilbrain]

That is sooo true!

[Johnny1A.2]

Originally Posted by Ulzgoroth

Defining a boolean trait which only ever is false seems kind of pointless though.

It isn't only ever false, though. Earth exists. It's the one definite True we know about, but it does exist.

[Varyon]

Originally Posted by Johnny1A.2

It isn't only ever false, though. Earth exists. It's the one definite True we know about, but it does exist.

Having the question "Is this planet habitable?" basically work out to be the same as the question "Is this planet Earth during the Holocene?" doesn't really accomplish much for you. Granted, a better question for the first one is "How habitable is this planet?" so that rather than a "Yes/No" answer you can have a range. A very habitable planet would be one where a person with minimal to no training could be dropped in naked and expected to thrive, this would progress into things being harder (needing more training and/or gear), eventually to the point of being largely indistinguishable from being a space habitat with more reliable gravity (and also progressing even further, with the habitat needing to be more resilient than a space habitat - like one in a gas giant or perhaps on a highly-volcanic planet).

[Johnny1A.2]

Originally Posted by Varyon

Having the question "Is this planet habitable?" basically work out to be the same as the question "Is this planet Earth during the Holocene?" doesn't really accomplish much for you. Granted, a better question for the first one is "How habitable is this planet?" so that rather than a "Yes/No" answer you can have a range. A very habitable planet would be one where a person with minimal to no training could be dropped in naked and expected to thrive, this would progress into things being harder (needing more training and/or gear), eventually to the point of being largely indistinguishable from being a space habitat with more reliable gravity (and also progressing even further, with the habitat needing to be more resilient than a space habitat - like one in a gas giant or perhaps on a highly-volcanic planet).

Yes, it's going to be a range. One reasonable definition of 'habitable' would be something Anne McCaffrey expressed in the intro to one of her Pern novels:

...third planet was enveloped by air Man could breathe, boasted water he could drink, and possessed a gravity that permitted Man to walk confidently erect.

That's a pretty good quick-and-dirty definition of 'habitable planet'. Of course it leaves lots of room for ugly surprises (and that particular planet held one in her story).

[Lancewholelot]

Originally Posted by Johnny1A.2

For a human population with access to high end (only modestly ahead of our own) space-flight level technology and a viable economic/industrial base, most planets are 'habitable'. For such a society, Mercury, Luna, Mars, the major asteroids, many of the big satellites of the gas giants, even the KBO worlds, are all 'habitable', in the sense that viable breeding populations could endure indefinitely on them. For slightly more advanced societies, even worlds like Venus and Io are 'habitable'. Advance the tech a bit more and the gas giants become 'habitable'.

That is speculative and still the stuff of science fiction. No human has ever been born off the Earth's surface. The long term effects of low to no gravity on viable human development are unknown.

[J. Edward Tremlett]

Trying to imagine how life could evolve there. It'd be constantly undergoing boom and burn cycles and have to find a way to cocoon.

[dcarson]

One think that habitable is can a average human produce enough wealth to produce the tech needed to keep an average human alive. We could build a Moon colony today but it would have to be subsidized.

[David Johnston2]

Originally Posted by J. Edward Tremlett

Trying to imagine how life could evolve there. It'd be constantly undergoing boom and burn cycles and have to find a way to cocoon.

I'm thinking migratory animal species predominate, while the plants have very durable seeds. The microflora and fauna would be able to cyclically produce extremophile offspring