[hgibbs]

Why won't we go to Mars (ever)? You may be sceptical of it happening in the next 100 years but very confident in it happening in the next 500 years, it is a very strong claim to argue that it will never happen in the broader context of increasing global wealth and massive improvements in space/energy technologies.

[earleybird]

We may place humans on Mars for periods of time, perhaps even lengthy periods but the idea of an alternate earth is in fact ludicrous. We seem to have a hard time just managing the planet we're on.

[hgibbs]

Why is it ludicrous - do you have a specific issue that you object too? How is living on Mars very different from e.g. the international space station or conditions in a nuclear sub in terms of human habitats? The other bits seem relatively easier than the problem of getting people to the planet. In general I think arguments of the form "it can't be done soon because of resource constraints" are very weak - there are plenty of examples of people making such arguments and being proven wrong a couple of decades later.