Avoiding Aliens

Well, that's a bullet-proof rebuttal Do you think that as soon as we gain the ability to traverse say local inter-stellar distances, our entire nature will change and it will all be STNG love and harmony? Any examples spring to mind?

He's been saying it for at least 20 years - in this case, he's just been asked to comment for this TV documentary, and so the topic has come up again.

You have to remember to split the "we" into ethical, scientific, political, and corporate. Once that is done, the rest is obvious...

Very much depends upon the resource in question - if it is bioshphere for colonisation, then I would say that Terra is somewhat more appealing than Europa and the asteriod belt. And time of travel will not be a consideration for such an endeavour if it is prompted out of necessity.

I think you are substantially over-simplifying this and making a rather large number of assumptions yourself. Difficulties with manufactured habitats will probably scale exponentially with population size, in terms of energy requirements, radiation shielding, impact shielding, etc. A ready-made planet would quite possibly be not just significantly more attractive, but the only viable option. I agree that bio-compatibility would be by no means assured, and probably somewhat of a miracle should it occur, but the Terran bio-sphere offers far far more than just pure biological resources.And when it comes to energy expenditure on combat - that simply depends upon the technological differential. Yes, if combat is expensive, that will weigh heavily against an armed assault. If combat is essentially zero-cost owing to sufficient technological advance, then it is a non-issue.