> You need tools, man power, basically you need an industrial complex which currently only exists on Earth. The idea that you can mine raw minerals on an asteroid and somehow turn them into a house with a full life support is not realistic, to put it mildly.
A very good point - which is exactly why we should do it. Depending on our industrial complex on Earth means that in case of a global natural or man-made disaster we could loose everything our civilisation has achieved so far, even if Earth stays perfectly habitable after the dust settles down. Encapsulating and packaging our civilisation also means creating a backup of our knowledge, both in science and arts - something that could become invaluable one day, even back on Earth.
> Encapsulating and packaging our civilisation also means creating a backup of our knowledge,
You don't need to go to space to do that. It is much, much easier to build such "backups" on Earth, in the form of underground bunkers or something. As a matter of fact, such facilities already exist, for instance the Svalbard Global Seed Vault[1], or any of the secret bunkers built during cold war[2]. Survivalism is a terrible reason for colonizing space, for space is a very hostile environment in the first place, so it makes very little sense to consider it as a place to rely on for survival.
Coming from an Engineering background we should all know that building something that actually works as a test case is the only way to know for sure for complex systems. Civilisation being the most complex system we have, I don't think that any group of individuals can account for everything that is needed in order to rebuild it. Lots of the underlying problems will only surface once a working 'civilization 2' is being attempted.
A very good point - which is exactly why we should do it. Depending on our industrial complex on Earth means that in case of a global natural or man-made disaster we could loose everything our civilisation has achieved so far, even if Earth stays perfectly habitable after the dust settles down. Encapsulating and packaging our civilisation also means creating a backup of our knowledge, both in science and arts - something that could become invaluable one day, even back on Earth.