I would think twice before labeling Margulis as a 'great biologist.' Her ideas caused quite a stir back in the day, but since then she's descended into quackery and lunacy.

http://scienceblogs.com/aetiology/2011/0…

I'll admit I'm shocked to have gone through an entire post without really disagreeing with you on any scientific point Charles. I'm almost at a loss as to what to say ;-)

Two smallish things to add, one sci, the other sci-fi.

The Goldilocks zone is a good place to look for life-sustaining planets, but I would stress it's not the only place to look. Energy from stars can lead to liquid water, but so can the internal heat of a sufficiently large planet or moon. There is ample evidence that Europa, one of Jupiter's moons, has subsurface oceans that could potentially harbor life.
On a slightly less scientific note, I'm not convinced that we have sufficient imagination when it comes to life. Our assumption that cognitively advanced life would have to consist of oxygen breathers is great when you're talking about the evolutionary path and conditions of Earth, but I'm not convinced that the evidence is in that this is the only real viable path towards evolutionarily advanced life.

Finally on an entirely non-scientific note, I have to step up to defend Star Trek. As any half-assed trekkie knows, the reason crops and animals weren't needed on Star Trek is because of the existence of replicators (I swear I didn't choose the video for its title). At least they have the decency to simply invent a non-existent technology, instead of decidin, ala Sunshine, that you can re-ignite the Sun with, what else, a nuclear device.

You got one thing right Charles: "Sunshine" is indeed a very bad movie...

"To obtain large life as we know it, life that can power the kinds of brains we have, brains that can formulate theories and make machines that are powerful enough to look at distant stars and find other worlds, you need an atmosphere with lots of oxygen."

The most important words there are "as we know it." We have a hard time imagining any other path to intelligence, but it is entirely possible that other intelligences evolve along a path very dissimilar from our own.

Also I liked Sunshine except for the third act. The monster was pointless. Yes, it made no sense to the sun dying like that or being re-ignited like that, but I could suspend my disbelief. I couldn't get around how the movie started as a study of people in extreme stress/boredom and got trapped in some stupid monster bullshit. If they were gonna be stupid, why not at least have Michelle Yeoh kick somebody in the head?

Sunshine was a great movie (with a great soundtrack).

Also, the sensational misreporting of that paper overstates any actual findings: http://arxiv.org/abs/1105.1031

It seems pretty unlikely that humans will ever travel interstellar distances, for the obvious reasons you touch on above. Transhumans, posthumans or our artificial antecedents, maybe, but humans have too much baggage to be cost-effective space travelers.

If - or when - we travel to another world, I just wonder how badly we'll screw it up when we introduce our novel earthean invasives into their (soon to be formerly) virgin biosphere...