Re: extraterrestrial life, if we presume life could form anywhere, what are some of the material factors that would prevent technological (as we know it) development? E.g., a planet without atmosphere would maybe prohibit ignition, a planet with an extremely low temperature might affect electrical storage, etc. Or, what are some of the technologies that could conceivably be produced in very different environments, and are there technologies that come to mind that would be physically very improbable to be produced in non-Earth-like environments?