"If our planet was 50% larger in diameter, we would not be able to venture into space, at least using rockets for transport."

I thought this was quite though-provoking from a Drake Equation standpoint. From what I've gleaned, the earth-like planets we know of seem to be a big bigger than Earth. Perhaps if there's civilization out there, they are hampered by the misfortune of being on a planet that's practically impossible to escape from. If they find it hard to put up a Hubble Telescope, perhaps they'll just not be as likely to bother.

My other remark is to the engineering. There's a quip that you have to be an engineer to make something that only just satisfies the requirements. Plenty of people build houses without much in the way of calculation. Even cars can be built by enthusiasts without degrees. This is what makes the space stuff such amazing engineering.