While we probably aren't near Earth's carrying capacity now, this is a sci-fi after all,
it is indeed sci-fi! but with our current level of technology, we're probably past earth's carrying capacity. it's anywhere from 1 to 10 billion, depending on who you ask.
but since it's sci fi...
i watched this episode of Extreme Engineering on the Discovery Channel. it was about "mega structures" or something like that, covering two project proposals going on in Japan to help with Tokyo's population problem. one's basically the skeleton of a giant pyramid build of subway tubes; from the intersection points hang sky scrapers. the other were these three multi-mile high towers with additional, open-air habitation levels connecting all three every few hundre feet. those super towers would also be connected with other triplets of supertowers, creating a miasma of human habitation reaching miles into the sky. of course, neither is past the blue print stage. it was still a cool episode.
but the real issue of earth's carrying capcity isn't space. the entire 6.5 billion people could fit happily into suburban-track style homes and take up no more space than the area of Texas. the entire populat could stand shoulder-to-shoulder in a space no bigger than Rhode Island. the real issue is food, and the rest of what we consume (which can be collectively called our ecological footprint). Americans currently have an ecological footprint of about 5-10 hectares. the figures for Europe and Japan are similar. IIRC the planet only has about half a hectare per person of usable land for a population of 6 billion.
the real carrying capacity will be subject to technology. we may be able to make more of the land useable, and we can definately extract more from the land we do use now (and maybe even sustainably). i'll have more to say on this later.
Any structure that is built on an already existing mass, like a planet, with its own resources, is bound to be much, much cheaper than a space station, which in addition to being incredibly massive, would still be totally dependent on Earth, and doesn't solve the problem of resources at all.
as i said previously, i don't imagine metal will be our one primary building material. glass is pretty strong, and silicon is pretty common. ploymers and ceramics are also extremely useful, and they're both made maily from carbon. i don't think iron is going to be a major building material because it's so heavy. aluminum and titanium make a lot more sense, at least if you ever need to move the materials (even just into place for final assembly). though, iron could be extracted from a planet and sent into orbit on a space fountain pretty cheaply...
but the bigger point i had is, does a base on mars actually use less resources than a base in orbit? i don't think so. about the only thing the space station would need to deal with that the planetary base wouldn't is generating artificial gravity. the planet, on the other hand, would need to deal with constructing a launch site and generating the resources to get things into space. launching things (big things anyway) from orbit is WAY cheaper than from the surface of a planet. it takes immense amounts of energy, relatively speaking, to escape a gravity well. that's why i've been suggesting the use of
space fountains to shuttle things off a planet and into orbit.
for that same reason i don't believe planets will be our primary source of heavy elemental resources. we can get everything we need from the asteroid belt, without having to deal with gravity (or course, the danger of asteroid collisions is the big trade off).
another issue with colonizing planets first is that we might want to
terraform them. that article is
really interesting, to me anyway. the one thing it leads me to conclude is that: we currently have no idea of whether terraforming will be possible in theory or in practice. at bare minimun it seems like terraforming would take centuries, and it wouldn't always be a process through which surface inhabitants could survive. but given that, it seems to me we'd start building surface structures long before we thought about terraforming. from what i can say, it seems like incompletely terraforming Mars would be possible (because the planet is smaller and its core has cooled down, it has less gravity to retain an atmosphere, and no magnetosphere to deflect solar wind). Mars would need more atmosphere and probably more water (to facilitate a higher greenhouse effect). on the other hand, we'd have to find a way to reduce Venus' atmophere. it'd probably be a much drier planets, since greater amounts of water would contribute to greenhouse effect. but in any case, the ability to do either seems to be reliant first on having an infrastructure capable of supporting frequent space travel.
ultimately it'll all be a matter of cost. after enough time, it's hard for me to imagine us not exploiting all the resources we can in our solar system... except in the event that we destroy ourselves or know ourselves back to the stone age.
How big would a station that holds 100 million people have to be?
absolutely massive; bigger than any single thing humans have ever built before, by a wide margin.
I think the treaty stating that a gonverment cannot lay claim to a celestrial body goes out the window when a civillian colony (not just an outpost) is founded
oh, agreed. treaties don't mean a damn when you've got the power to ignore them. just look at the U.S. history of accused war crimes, our history of nuclear non-proliferation, etc.
2 a ranch
as in meat? meat takes such a huge investment, and with the exception of omega-3 fatty acids in cold-water fish (which we can also get from flax), meat doesn't provide us with nutrition we can't get from other sources. plant protein isn't really inferior to animal protein as a dietary source; it's just less abundant. it's a little less effecient, but not detrementally so. most skinny vegans are skinny because they don't take take the effort to balance their diets. a friend of mine decided to take up body building after he'd been a vegan for 4 years; he doesn't eat meat for spritual reasons. either one of his arms is thicker than my neck. he uses that muscle building powder crap, which is mostly soy protein.
but maybe you meant something else...
BTW, i'm really enjoying this conversation everyone.
