SETI Astronomer Seth Shostak talked to the New York Times about going to other planets, and why we wimpy fleshbags weren't ever going to manage it. Though this attitude may be influenced by a career of holding still and waiting for signals to arrive, he still makes some good points - and when a guy who watches the entire universe the way you'd watch your inbox talks, it's a good idea to listen.
The main obstacle to manned exploration of other planets is the truly mind-melting distances involved - measured in light years, basically "the fastest speed in the universe multiplied by a really long time", meaning that even the closest planets are lifetimes away at any conventional speed.
Shostak's solution is an army of intelligent robots, and we have to say that as solutions go it's hard to find a problem that wouldn't solve. Robots can be accelerated far faster than fussy humans, who are all "I'm hungry" and "I'm thirsty" and "I need oxygen to survive" about interstellar travel. An armada of intelligent probes could map entire worlds for us, perhaps even bootstrapping their own factories and tools on arrival, sending back enormous amounts of data without us ever having to set foot outside our gravity well.
We will anyway, of course, and that's where we and Dr Shostak disagree. He paints a penned-in picture of humanity cut off from the rest of the universe by enormous distances, viewing alien worlds as interactive TV programming at best. But humanity's entire history has been that of moving out as far as they can and living there as well, with little things like "is it possible to survive" taking second place to the need to explore. The only thing that'll could stop us colonising the solar system is if we wipe ourselves out first, and once the eight-or-whatever planets are full (with entire nations in the asteroid belts) we'll set our sights further afield.
Limitations on interstellar exploration tend to say things like "according to current scientific knowledge" or "would require more energy than we can produce", which are reasonable until you realize they could equally apply to any other point in history. Getting to the moon would have required more horses than available to mankind in the 1700s, but that doesn't mean there wasn't another way to propel a craft.
Cryosleep, generational ships, downloading our dinky selves into silicon hooked up to a growth-vat and a sample of skin: whatever it takes to get out of the solar system, some distant day an awesome group of individuals will do it.
Posted by Luke McKinney