The Fermi-paradox was the starting point of the first post on this blog, and while its flattering, I don't think I've solved it - but thanks anyway :) Nevertheless a high EROEI fuel seems to be an indispensable ingredient to reach space and land on the Moon for example. It is funny, but it actually took us less than a century (or 4 generations) to figure out space travel once we had the fuel, but we did not get any further than that in the past five decades. If we continue down the path of worsening energy returns however, we will soon be forced to kiss good-bye to the stars... A Ponzi-scheme being very good insight into this process. This translates to a mere century as a timeframe for an entire species to attempt space travel... Not long enough to learn all the tricks - if it is possible at all. Considering how long it will take for Earth to regenerate the resources we so generously dispersed, a planet might have only a single shot (or two, max three..?) to give birth to such a high-tech civilization... Compare this 1, 2 max 3 windows lasting a century each, to a 5-10 billion years a planet is capable to sustain life... It is such a minuscule timeframe, that it is a wonder in an of itself that we are born right into the middle of it. From the standpoint of curiosity we are extremely lucky on planetary scale...