Size of 'empires'

[Victor_D]

I do not rule out space hotels, even pretty big ones with O'Neill cylinders and what not. It's just I can't see them as permanent colonies. Manufacturing, tourism, research, defence, these are all viable uses for orbital installations; colonization will always be focused on planets/large moons, because that's human habitat. It's the same reason we are not building huge floating cities in the middle of the ocean to "colonize" it (and mind you, floating cities would still have access to many ocean-based resources, unlike space habitats which float in a vacuum.

[bunnyboy]

A huge amount of crop research would not be done without seed companies, let alone GM. The small company I work for in Hampshire, we work closely with a research company in Yorkshire that's family owned. If you just gave away their crop development and new breed varieties they would be broke.

It's true that even people working on seed companies have to eat.

But It's not solution, that big company like Mosanto can pump seeds to market with low prices until they get monopoly and then lift the prices on sky, making only one type of seeds available. And the one is highly dependable of their own poisons to survive against diseases and weeds. With their army of lawyers they can also seize any harvest, which has traces of their copymarked dna. Throwing seeds on the unguarded fields and mixing the flours from different farmers on only mill at area of state either purposely or accidentally are common rumors, but GM plants are found hundreds of miles away from their legal location.

[bunnyboy]

why people would want to live in space.

#1 medical reasons, lowered strain on heart for instance, could let people live longer.
#2 scenic, the view gotta be awesome.
#3 it's SPACE man! that is another awesome in itself.

probably a few more, can't think of them right now, tired as hell, but get a one way ticket down to 20k US and there will be people that would wanna go up.

Actually
#1 you start losing your bones
#2 it's get soon boring
#3 we too are in SPACE but with less emptyness

[Trantor]

Leaving seeds to the seed companies is effective specialisation. You don't like who your currently buying from, buy from someone else.

Why buying at all?
My grandfather was a farmer, he never "bought" seeds.

[Smithy]

You are all concerned about Genetic use restriction technology, which has never been realised.

Anyway the amount of seed retention is dependent on the laws of the Land so to speak. I think here in the UK we can retain a certain percentage of the seeds legally. It's very rarely done though I might add.

Why buying at all?
My grandfather was a farmer, he never "bought" seeds.

Scale, and specialisation, we don't want to invest in the equipment to harvest, store and manage seeds, we want to concentrate our time and capital on production.

Anyhow in my own personal experience:

With sedum, we don't poses the equipment to viable extract and store the seeds, we would also destroy our product to extract the seeds, nor does sedum ripen at the same time. Sedum is used to create living roofing mats if your wondering what the hell it is.

When I worked with opium, we harvested the whole plant and pulp the head and stem and then use chemicals to extract the opiates for use in morphine excreta. Opium poppies are in their highest "milk" before ripening and the poppy heads explode to seed, thus we harvest the crop before it is viable for seed retention. That be said, again we didn't have the equipment to harvest, process and store poppy seeds (also I think it's illegal for us to retain the seeds, I didn't check the exact legal stuff, I was quite young when working for the Janaways anyway). When we weren't growing opium we were growing wheat. And again we didn't possess the silo capacity/ or radiators to store and maintain seeds. Let alone the expertise/experience in seed storage. We concentrate on growing good crops, and efficient and effective harvesting.

[Smithy]

But It's not solution, that big company like Mosanto can pump seeds to market with low prices until they get monopoly and then lift the prices on sky, making only one type of seeds available. And the one is highly dependable of their own poisons to survive against diseases and weeds. With their army of lawyers they can also seize any harvest, which has traces of their copymarked dna. Throwing seeds on the unguarded fields and mixing the flours from different farmers on only mill at area of state either purposely or accidentally are common rumors, but GM plants are found hundreds of miles away from their legal location.

The reason you can find them hundreds of miles away is because plant's are naturally very good at extending their range either by the wind or in the guts of birds.

As far as I can tell, this Monsanto problem is particular to the USA and it's overly complex legal system, there's a reason half the worlds lawyers are found in the US after-all, though I think Syngenta, BASF, Dow AgrosSciences, Bayer, and DuPont would have a couple of words about Monsanto acquiring a monopoly on market share.

I don't see this being an issue in the UK, not yet at least, so I can't comment with any real commitment.

[bunnyboy]

The reason you can find them hundreds of miles away is because plant's are naturally very good at extending their range either by the wind or in the guts of birds.

And that's why quantity of seeds with low variation is so dangerous for diversity.

As far as I can tell, this Monsanto problem is particular to the USA and it's overly complex legal system, there's a reason half the worlds lawyers are found in the US after-all, though I think Syngenta, BASF, Dow AgrosSciences, Bayer, and DuPont would have a couple of words about Monsanto acquiring a monopoly on market share.

But the local seed market, which has lot of variation thriving in local conditions, is crushed.

[Absalom]

I had to fix some of the quotes for you. Might want to watch out for that in the future.

One of the nice things about space is that you can move the industry. Hence why asteroids are considered good mining choices: they let you move to the next asteroid without much complication.

Doesn't matter if you need to move bulk mass to the industry which needs all these resources. Plus, asteroids have their own challenges (near zero-g, often a serious lack of volatiles and other chemicals needed for metal extractions, etc.).

Let me repeat: you can move the industry. In most current operations, you can't move an e.g. smelter to where your iron ore and coal are sourced from. IN SPACE YOU CAN. Movement in space is cheap because you have effectively 0 friction and drag.

Mars doesn't have an atmosphere that we can breath, nor a biosphere that we can live off of. Since we'll have to construct all of that anyways, it's generally agreed that the orbital-colony ideas are better choices.

Generally agreed by whom?

By most of the people that I've heard talk about it.

Not many in the space community would agree with this, certainly I haven't met many such people. Mars is a planet, a planet has resources (it's actually a huge pile of them).

Logical failure: you assume that the presence of resources is the same as the accessibility of resources. In the case of planets, most resources are buried too deep to access. Far too deep. With asteroids, most or all of the resources are accessible.

Empty space offers no resources except for solar energy.

Nobody cares about empty space, everything would be located next to resource locations. Asteroids are a major example, as are comets.

An orbital settlement colony would essentially has to import *everything* from Earth or some other planet.

Define everything. Food will be done in small low-gee farming cylinders, manufacturing in various locations either within, mounted externally onto, or near by the actual habitats. Plastics will need to be made from organic sources by this point anyways, so access to Earth's petroleum won't be of great benefit. The only thing that I'd expect to get imported is boot-strap supplies and high-value materials (such as patented medicines).

What would it export - how would it justify its existence *economically*?

Do you know why the internal combustion engine is important to the future of hydrogen powered cars? Because the catalyst (platinum as I best recall) is rare. China has ~90% of the Earth's extractable rare-earth minerals, but is slowly reducing the amount that it exports. The list goes on. When in the presence of sufficiently cheap energy, no worries about pollution, and rock that you can use almost all of (or possibly literally all of), refining these things becomes viable.

The fact is that on Mars, you can find everything to build a sustainable independent colony, including all the biogenic elements. You need to build something? Get out, mine stuff, process it, use it. It's probably the case that since Mars has had an active geology for quite some time, it has also developed localized concentrations of resources.

The problem with Mars is that you have to spend lots of energy moving your extracted materials to where you need them. In contrast, the energy involved in moving stuff in space depends entirely on how fast you want to get it to it's destination. Rail travel is more efficient than any truck, but space travel is more efficient than even that.

Asteroids are usually undifferentiated piles of rubble. There are metallic ones, but they usually lack volatiles that are needed to efficiently extract the metals (because I doubt you want to be sending unprocessed rock back to your planet for processing, that would be terribly useless).

In space, you can use magnetic forces to separate out the individual elements when in a plasma state. Don't understand where the energy would come from? In space, you can build in zero-gee. Paper-thin mirrors a mile in diameter are practical. Energy is cheap anywhere that we would send a large population. Volatiles aren't all that important for element extraction, and likely wouldn't be used.

Well, it certainly couldn't be that much less practical than Mars. If nothing else, I believe that Titan has a smaller gravity well.

More importantly, it has an atmosphere and readily available supplies of all kinds of hydrocarbons and other organic compounds.

Why do we care about those? Did you actually take the idea of going into space for petroleum seriously? Space habitats would care about carbon, but only as a base material for soil & non-petroleum materials (e.g. carbon fiber). Oils & plastics would be sourced from plant sources (in fact, it's happening now). And since most of the carbon compounds are likely to be used inside the habitat, there will be almost no carbon loss.

The trick is: why would we want to land? The only possibility that I know of is the combination of solar power and minerals, and for that we can just use reflectors to focus sunlight onto collectors at whatever asteroid we're mining.

Inverse square law. Mercury gets far more sunlight, and I assume we can make photovoltaic panels out of its rocks. With water on the poles, a small human colony can exist to tend the machines.

You didn't read what I said. We can use mirrors to reflect sunlight onto the solar collectors. This allows us to increase the sunlight hitting the collectors. Because the mirrors will be in zero-gee, they can be essentially paper-thin (actually, probably thinner), because they don't have to support their own weight (because, after all, the mirrors are in zero-gee).

For that matter, the intensity of sunlight at Mercury is actually a liability. The only place that you can count on being safe to land at is the actual poles, which eliminates most of the planet from being particularly useful. Mercury is at most valuable as a mining facility for large projects built around it, and even then might be better off just shipping materials in (depends on how well your launch infrastructure deals with the conditions).

Actually, the density of the Venusian atmosphere could make it useful. I don't recall the constituency, but it obviously has volatiles, many of which could be important for space habitats.

You mean the space habitats which make no sense? Venus' atmosphere is mostly nitrogen, co2, with clouds of sulphuric acid. It's very hydrogen-poor, unfortunately. It's not that the volatiles are of no value, but Venus' steep gravity well makes it rather impractical to get them there. Earth is a much better source, much closer to where we want them.

Why would a space habitat care about hydrogen? Space habitats can get plenty of hydrogen with magnetic scoops and patience, the nitrogen and CO2 are what space habitats would care about. Agriculture and breathing.

Incidentally, were the sulfuric acid practical to extract, it would itself be useful. Sulfuric acid contains hydrogen (2 hydrogen, 4 oxygen, 1 sulfur), and is a major industrial chemical.

As for Earth, that depends entirely on atmospheric traits that I'm not going to compare between the two.

They offer basically the same advantages of most of the planets,

No they don't, they're just enclosed bubbles of air in an ocean of nothingness. It's like comparing an island made of solid rock, say, Britain, with an artificial platform, say, Sealand. Even with near 100% effective closed-loop life support, they'll always be dependent on resources from the outside. Again, what economic rationale can you offer for building them?

As I said, they offer the same advantages as planets: an artificial climate free of uncounterable threats from outside. Then again, maybe I'm being too generous to planets. It's like comparing a lifeless lump of rock, with Sealand. Seriously, what economic rationale can you offer for colonizing planets? The only things they offer are mineral concentrates and unbreathable atmosphere (obviously, I'm not talking about Earth).

but traveling between stations is easier than returning to orbit or traveling between distant surface colonies.

So? Martian colonists wouldn't want to travel back and forth; they signed up for colonizing Mars.

You obviously don't understand what I'm talking about. It's easier, cheaper, and faster to travel between two stations that are 25km apart than between two habitats on Mars that are 25km apart. I'm not talking about traveling between Mars and Earth, or even Mars and Phobos, I'm talking about traveling on Mars.

Besides which, most people don't want to get stuck in one place if it turns out bad. With a station you could take the return trip to space. With Mars you have to take an expensive trip to orbit before you can take the trip back.

Meanwhile, everything that we know you can do on a planetary surface we believe we can do on a station as well. You also get easy access to both vacuum and zero-gee, and can physically move your colony if you have a reason (e.g. economics). Space habitats are basically a better option than planetary colonies, Zubrin is just fascinated with the romance.

What you're citing is a case for orbital manufacturing, if we find something that can only be economically manufactured in zero-g (say, special crystals, unique alloys, exotic chemicals/drugs, etc.). But that will hardly require manpower in the millions. An orbital/lagrange point factory wouldn't be a settlement/colony.

Planets like Earth and Mars are places where humans can actually live, work, and develop an independent sustainable culture. Which is kind of the point of colonizing space.

It's just as easy to do in space as on a planet, especially since movement is so much easier in space, and construction can be so much cheaper. The only things that it's easier to do on Mars than in space are:
1) live on a planet, and
2) have gravity.
And gravity isn't likely to be hard.

Stop looking to emotional arguments, and ask yourself this: how nice are the economic arguments for planets? Frankly, they aren't all that nice. Once we get into space in a major way we'll see some people starting to live on other planets, but most will either stay on Earth, or move to space habitats, because they'll only go somewhere if they have an actual reason. Mars would be a good tourist destination after a while, but otherwise it would be the equivalent of North Dakota: sparsely inhabited with little to promote it.

Meanwhile, I don't think the Moon has all that much to suggest itself as a preliminary colony site.

It has water and some metals we might use to tend for our cis-lunar space infrastructure.

Now there you have a point: bootstrapping.

I do not rule out space hotels, even pretty big ones with O'Neill cylinders and what not. It's just I can't see them as permanent colonies.

That's quite a quandary you have there.

Manufacturing, tourism, research, defence, these are all viable uses for orbital installations;

You'll have to convince the people that'll actually be living in these places that their homes are only useful for such purposes.

colonization will always be focused on planets/large moons, because that's human habitat.

No, that's a natural gravity well with an associated surface that might be walkable. Human habitat is anywhere that humans can live without breath masks and similar equipment. The inside of a habitat structure on Mars is human habitat, the outside is not human habitat. The only actual advantage that planets have is a natural gravity well, and once someone builds a rotating station to generate artificial "gravity" that advantage evaporates.

It's the same reason we are not building huge floating cities in the middle of the ocean to "colonize" it

By that logic we won't colonize Mars either: nothing we're likely to get from there is worth enough to establish a colony, because everything that we got back would have to be launched, thereby rendering Mars useless for anything but science. In comparison, a space habitat requires the launch of it's initial equipment, and small amounts of thrust applied to whatever it sends back to pay for itself. And since it's in a zero-gee frictionless environment that thrust can be very small indeed. Thrust that wouldn't move you an inch on Mars can move you across the entire solar system in space. This allows solar sails (which, incidentally, can send something towards the sun when NOT facing the sun: it's an orbital thing) to be used to send whatever you want back to Earth. To use a stereotypical example, gold.

If the economics of trade between the Americas and Europe were the same as between Earth and Mars, the the thirteen colonies would never have come into existence. Instead, the Europeans would have setup trading missions for spices, everyone would have tried to find gold, and everywhere that a high-value product wasn't found the colony would be abandoned. The colonies within the New World weren't established because the land was habitable, they were established because the people who paid for the trip were going to get money out of it back home in Europe. Doing this between Earth and the asteroid belt is easier than between Earth and Mars, because most of the cost is in launching from the surface of planets.

(and mind you, floating cities would still have access to many ocean-based resources, unlike space habitats which float in a vacuum.

Mind you, space habitats would still have low-energy access to many resource locations, unlike planetary habitats which are fixed in place and must deal with irregular terrain, surface friction, and atmospheric drag.

[Victor_D]

It's too late now, so I'll comment just on the things which I consider most wrong about your argument.

Logical failure: you assume that the presence of resources is the same as the accessibility of resources. In the case of planets, most resources are buried too deep to access. Far too deep. With asteroids, most or all of the resources are accessible.

No. Considering that we have to dig in any case, and considering that you can dig pretty deep (let's say 10 km with sufficiently advanced technology), a surface of a decent planet like Earth or Mars probably gives you access to more stuff that the whole of the asteroid belt. With the difference that on planets, resources are often concentrated in deposits, and you have many different kinds of resources on one body instead of spread out over a large volume of empty space.

Do you know why the internal combustion engine is important to the future of hydrogen powered cars? Because the catalyst (platinum as I best recall) is rare. China has ~90% of the Earth's extractable rare-earth minerals, but is slowly reducing the amount that it exports. The list goes on. When in the presence of sufficiently cheap energy, no worries about pollution, and rock that you can use almost all of (or possibly literally all of), refining these things becomes viable.

Hydrogen will hardly ever be used in cars, in combustion engines or in fuel-cell electric cars. Too difficult to store/handle. Rare-Earth minerals are pretty abundant, so it's actually a bit of a misnomer. The present day situation that China controls the supplies is entirely a result of the negligence and unwillingness of the rest of the world to develop their own deposits (mostly because it is an environmental nightmare).

Like it or not, asteroids are not some magical resource piles. They're mostly rock, and they contain the same elements planets do. *Some* asteroids are more metallic, because they are fragments of protoplanetary cores blown to pieces in collisions in the young solar system. They also are dry as hell, they lack volatiles. The asteroids with volatiles on the other hand usually lack any decent concentrations of metals. Mining most asteroids would thus be like mining random mountains on Earth - blow them up, pulverize, and then sift through it to extract useful metals and minerals. It would take a lot of energy and the results would be sub-optimal.

Aside from the environmental concerns, it makes little sense to mine the asteroids or even set up space habitats whose sole purpose is to live off asteroid mining. If it is ever done, it will happen in a relatively small scale, heavily automated fashion.

The problem with Mars is that you have to spend lots of energy moving your extracted materials to where you need them. In contrast, the energy involved in moving stuff in space depends entirely on how fast you want to get it to it's destination. Rail travel is more efficient than any truck, but space travel is more efficient than even that.

No. There is orbital mechanics at play, and moving around the solar system always takes a lot of energy. Mining stuff a 100 kilometres from a domed city on Mars and transporting it there will always be comparably easier than doing the same in the asteroid belt. If only because Mars has more resources, better-concentrated resources, and varied resources in one neat package.

In space, you can use magnetic forces to separate out the individual elements when in a plasma state. Don't understand where the energy would come from? In space, you can build in zero-gee. Paper-thin mirrors a mile in diameter are practical. Energy is cheap anywhere that we would send a large population. Volatiles aren't all that important for element extraction, and likely wouldn't be used.

Because turning bulk matter into plasma for element separation in space is easier than the old fashioned resource extraction on a planet which takes far less energy and can be done with familiar methods Right. Maybe with magic-era technology. I am talking near/medium term.

Why do we care about those? Did you actually take the idea of going into space for petroleum seriously?

No.

Space habitats would care about carbon, but only as a base material for soil & non-petroleum materials (e.g. carbon fiber). Oils & plastics would be sourced from plant sources (in fact, it's happening now). And since most of the carbon compounds are likely to be used inside the habitat, there will be almost no carbon loss.

Oh, I forgot you believe in 100% effective, small-scale, closed-loop life support. Hydrocarbons are valuable because they contain hydrogen and carbon, surprisingly. Often also oxygen, nitrogen, and other useful volatile elements which we, carbon-based lifeforms require.

Of course you will not understand my argument, because in your world, elements are obtained from rocks easily and freely, magically combined into exactly the chemicals you need, and everything is as effortless as child's play. I am actually a bit confused - your argument against planets is that you need to move around on them (which is something we've been doing since forever), but at the same time you're invoking magic-level technology to deal with all the limitations of space habitats. Please, at least be consistent.

You didn't read what I said. We can use mirrors to reflect sunlight onto the solar collectors. This allows us to increase the sunlight hitting the collectors. Because the mirrors will be in zero-gee, they can be essentially paper-thin (actually, probably thinner), because they don't have to support their own weight (because, after all, the mirrors are in zero-gee).

I did, it's called handwaving. Of course you can build giant space mirrors to focus sunlight out in the asteroid belt. My point was that the same surface area can potentially produce far more energy when you're closer to the Sun.

Why would a space habitat care about hydrogen? Space habitats can get plenty of hydrogen with magnetic scoops and patience, the nitrogen and CO2 are what space habitats would care about. Agriculture and breathing.

More handwaving. I am not saying that what you describe is impossible, it's just not easy or practical, and it won't be for a long time to come.

As I said, they offer the same advantages as planets: an artificial climate free of uncounterable threats from outside. Then again, maybe I'm being too generous to planets. It's like comparing a lifeless lump of rock, with Sealand. Seriously, what economic rationale can you offer for colonizing planets? The only things they offer are mineral concentrates and unbreathable atmosphere (obviously, I'm not talking about Earth).

If you want to argue like that, what economic rationale is there to living outside Earth at all? Heck, why did our ancestors leave Africa in the first place?

Planets offer, aside from the aforementioned superior concentrations of *usable* resources, gravity (real gravity), shielding from galactic cosmic radiation, a possibility of practising relatively simple agriculture, and an opportunity to create a new macro-scale biosphere where life can actually develop and evolve on its own, instead of the sterile regulated artificial approximations of a biosphere found in space habitats. It's ultimately a choice between surviving (space habitats), and living (on worlds).

If your vision for humanity is to survive in their tiny metal/plastic bubbles of air in space and move around like locusts, I can't argue with that. It is my opinion that people will always prefer their natural habitat, the one we evolved in, that is, planetary surface; and that in the process they will spread Terran life to new places and marvel at that. Whatever else they'll do in space will be in support of this 'mission'.

No, that's a natural gravity well with an associated surface that might be walkable. Human habitat is anywhere that humans can live without breath masks and similar equipment. The inside of a habitat structure on Mars is human habitat, the outside is not human habitat. The only actual advantage that planets have is a natural gravity well, and once someone builds a rotating station to generate artificial "gravity" that advantage evaporates.

Nope. I'll much rather walk around Mars with my breathing mask and pressure suit than spend my life enclosed in an artificial rotating space habitat. It won't be functionally different from wearing winter clothing on Earth (because most of Earth's surface is not habitable to unclothed humans either). I'll much rather take a trip to see the cliffs of Valles Marineris than to stare into the blackness of space.

As I said, living vs. surviving. The rest of your argument comes down to this, and I see an irreconcilable difference there, so there's no more point in talking about this.

[Absalom]

Like it or not, asteroids are not some magical resource piles. They're mostly rock, and they contain the same elements planets do. *Some* asteroids are more metallic, because they are fragments of protoplanetary cores blown to pieces in collisions in the young solar system. They also are dry as hell, they lack volatiles. The asteroids with volatiles on the other hand usually lack any decent concentrations of metals. Mining most asteroids would thus be like mining random mountains on Earth - blow them up, pulverize, and then sift through it to extract useful metals and minerals. It would take a lot of energy and the results would be sub-optimal.

Actually, the "slag" is useful for radiation shielding, basalt fiber is between carbon fiber and fiberglass in strength, etc. Many of those minerals will have their own value, those that don't will have elements of value, the leftovers will still be useful for radiation-shield mass. Every ton that you mine gets fully used, either for commerce or for station improvement.

Aside from the environmental concerns, it makes little sense to mine the asteroids or even set up space habitats whose sole purpose is to live off asteroid mining. If it is ever done, it will happen in a relatively small scale, heavily automated fashion.

Certainly it'll be automated, but the scale will only be decided by the call for resources. The largest cost of space travel is in launch, and Mars doesn't save you much there (the Moon and Mercury are both much better though).

The problem with Mars is that you have to spend lots of energy moving your extracted materials to where you need them. In contrast, the energy involved in moving stuff in space depends entirely on how fast you want to get it to it's destination. Rail travel is more efficient than any truck, but space travel is more efficient than even that.

No. There is orbital mechanics at play, and moving around the solar system always takes a lot of energy. Mining stuff a 100 kilometres from a domed city on Mars and transporting it there will always be comparably easier than doing the same in the asteroid belt. If only because Mars has more resources, better-concentrated resources, and varied resources in one neat package.

Easier? Depends on your definition, though "with a train" can be construed as easy. Cheaper? All that you need in space is a solar sail and patience... or a mass driver, or any number of other things. Space travel over a given distance is always going to be lower-energy if the comparison is made with reasonably similar circumstances.

In space, you can use magnetic forces to separate out the individual elements when in a plasma state. Don't understand where the energy would come from? In space, you can build in zero-gee. Paper-thin mirrors a mile in diameter are practical. Energy is cheap anywhere that we would send a large population. Volatiles aren't all that important for element extraction, and likely wouldn't be used.

Because turning bulk matter into plasma for element separation in space is easier than the old fashioned resource extraction on a planet which takes far less energy and can be done with familiar methods Right. Maybe with magic-era technology. I am talking near/medium term.

I'm imagining large-scale induction heating, not magic. The scale is notable, the technology exists today. Besides, that was just an example that someone not involved with these industries (like myself) can think of without doing research. Solar radiation outside of Earth's atmosphere is apparently ~4 times as strong as solar radiation at the surface. Mars wouldn't be so bad, but Mars also has much worse dust storms, and both have to deal with night, when no sunlight falls on collectors at all. Both also require structural support for any mirrors used, whereas Mylar coated with a reflective material is enough for a mirror in space. Medium-term, it works, near-term it's just a matter of if we launch anything like it.

And yes, simple-but-brute-force is indeed "easier" than chemistry.

Space habitats would care about carbon, but only as a base material for soil & non-petroleum materials (e.g. carbon fiber). Oils & plastics would be sourced from plant sources (in fact, it's happening now). And since most of the carbon compounds are likely to be used inside the habitat, there will be almost no carbon loss.

Oh, I forgot you believe in 100% effective, small-scale, closed-loop life support. Hydrocarbons are valuable because they contain hydrogen and carbon, surprisingly. Often also oxygen, nitrogen, and other useful volatile elements which we, carbon-based lifeforms require.

Why do you say "small-scale"? For small-scale operations we aren't talking about colonizing Mars or space habitats, because there's too much effort involved in living to actually do anything. I'm not talking about research stations here, I'm talking about population centers.

Of course you will not understand my argument, because in your world, elements are obtained from rocks easily and freely, magically combined into exactly the chemicals you need, and everything is as effortless as child's play. I am actually a bit confused - your argument against planets is that you need to move around on them (which is something we've been doing since forever), but at the same time you're invoking magic-level technology to deal with all the limitations of space habitats. Please, at least be consistent.

Actually, I am consistent. You use raw elements as soil and air supplements, looping the "waste" soil back into the "newest batch", skim off a certain amount (determined by soil analysis) to throw back through your plasma (or whatever) separator to obtain raw elements, which you add to the raw elements that you pulled from your last mining batch. If this doesn't work, then neither do biospheres.

You didn't read what I said. We can use mirrors to reflect sunlight onto the solar collectors. This allows us to increase the sunlight hitting the collectors. Because the mirrors will be in zero-gee, they can be essentially paper-thin (actually, probably thinner), because they don't have to support their own weight (because, after all, the mirrors are in zero-gee).

I did, it's called handwaving. Of course you can build giant space mirrors to focus sunlight out in the asteroid belt. My point was that the same surface area can potentially produce far more energy when you're closer to the Sun.

There may be less need for them, but mirrors work in Mercury's area too. A properly designed ore processing system could even use them to melt ore directly, though I'm not certain what the exact design would be (I assume that it would at least partially be based on ion engines).

As I said, they offer the same advantages as planets: an artificial climate free of uncounterable threats from outside. Then again, maybe I'm being too generous to planets. It's like comparing a lifeless lump of rock, with Sealand. Seriously, what economic rationale can you offer for colonizing planets? The only things they offer are mineral concentrates and unbreathable atmosphere (obviously, I'm not talking about Earth).

If you want to argue like that, what economic rationale is there to living outside Earth at all?

What economic rationale was there for colonizing the New World? What they could send back of course. This is why I've mentioned things like Platinum, Rare-Earth minerals, etc. If extracting it is nasty, but it's really valuable, then do it in space.

Then there's food. We probably don't do well with low gravity, but does anyone really care what gravity the strawberry on their table was grown in? The climate-controlled nature of a space habitat means that you never need to worry about hail storms, frost, or any of a number of other factors. If you need seasons, then you can reduce the sunlight coming in. Mineral depletion? I've already described the basic mechanism that you use to deal with that above, various biological organisms convert "rock" minerals into the forms usable by plants, so as long as you add & sufficiently blend enough raw minerals (of the right composition!) with enough biologically active soil (to act as a source for the soil organisms) you'll be able to keep the system going despite exporting most (or all) of the food produced on the station.

Furthermore, if we assume that we won't avoid the melting of the ice caps, then we're likely to wind up with zoos dedicated to just preserving various animals and plants. Eventually (note: this is far-future here) it'll make more sense to build (or more likely buy) appropriately large habitats to put all of these creatures in so that we only have to maintain the habitat, and the ecosystem does the rest of the work itself (I assume that this would be long-term in what we're talking about, but once you've got the actual processing & construction equipment, something like this becomes likely).

Planets offer, aside from the aforementioned superior concentrations of *usable* resources, gravity (real gravity),

We've never seen any indication that the difference makes a difference.

shielding from galactic cosmic radiation,

The solution is already known: use the stuff that you aren't selling to someone else.

a possibility of practising relatively simple agriculture,

A window garden is simple, but is only sufficient to provide spices. A backyard garden is simple, but won't feed your population. A large garden will feed your family, but involves a lot of effort, so most people won't do it regardless.

A farm field requires dirt (which would require time to "culture" from soil brought from Earth, but WOULD do precisely that), seeds, and equipment to work it with. This is as simple as you can get large-scale agriculture, and if you want to have a long-term population (instead of a few people living there until something breaks) then you require large-scale agriculture so that you can get the specialization that supporting an artificial environment requires. This is just as practical on a low-gee space habitat (which, honestly, is where it would be done) as on a non-Earth planet, since both will require artificial drainage (you don't want your water draining into the loose soil of Mars, since you likely won't get it back), filtered sunlight (and if you're out by Mars, artificial sunlight to supplement the filtered stuff), and equipment to plant, fertilize, and harvest.

and an opportunity to create a new macro-scale biosphere where life can actually develop and evolve on its own,

Hate to break it to you, but any practical attempts at terraforming are likely to require a vast space-based economy to support it, and will still take hundreds of years. Your project would basically guarantee the development of a significant population in space.

instead of the sterile regulated artificial approximations of a biosphere found in space habitats. It's ultimately a choice between surviving (space habitats), and living (on worlds).

Sterile? I can't imagine a space habitat where the plant and animal life is all caged, penned, or potted, since maintaining such a thing wouldn't be practical. Did you mean to be talking about diversity instead? And at any rate, the human population is moving out of the more natural rural and suburban areas that we have been living in, into urban areas. We don't really want "natural", what we want is "nature on our terms". The natural habitat of humans is not "nature", but instead "civilization".

If your vision for humanity is to survive in their tiny metal/plastic bubbles of air in space and move around like locusts, I can't argue with that.

The problem is that unless you're talking about Earth or a terraformed planet that is exactly what you get. And planets would actually suffer from this more than space habitats, since e.g. O'Neill cylinders are miles along their dimensions, while planetary habitats would primarily be domes.

It is my opinion that people will always prefer their natural habitat, the one we evolved in, that is, planetary surface;

That is Earth. And a space habitat is just as good of a replacement for it as a dome on Mars.

and that in the process they will spread Terran life to new places and marvel at that. Whatever else they'll do in space will be in support of this 'mission'.

If they're spreading it beyond Mars then they're doping it in space habitats, and space habitats will be what they're used to. Your far-future terraformers aren't going to be planet dwellers, because the planets that they're terraforming won't be habitable. They'll be space dwellers, because that's where they have their habitats stored.

No, that's a natural gravity well with an associated surface that might be walkable. Human habitat is anywhere that humans can live without breath masks and similar equipment. The inside of a habitat structure on Mars is human habitat, the outside is not human habitat. The only actual advantage that planets have is a natural gravity well, and once someone builds a rotating station to generate artificial "gravity" that advantage evaporates.

Nope. I'll much rather walk around Mars with my breathing mask and pressure suit than spend my life enclosed in an artificial rotating space habitat. It won't be functionally different from wearing winter clothing on Earth (because most of Earth's surface is not habitable to unclothed humans either). I'll much rather take a trip to see the cliffs of Valles Marineris than to stare into the blackness of space.

As I said, living vs. surviving. The rest of your argument comes down to this, and I see an irreconcilable difference there, so there's no more point in talking about this.

And I don't see much hope of much more than surviving on Mars for the first several generations. There's a reason why I compared it to North Dakota.