Crooked Timber makes an excellent point about traveling through the galaxy:
… Why would we bother? By hypothesis, that would require the ability to live in interstellar space for thousands of years. A civilisation with that ability would have no need of planets. [sic]
Via Newmark’s Door.
BTW: I would have found the “why would we bother” sentiment insulting a few years ago … but what was that Keynes said about facts and changing his mind?