>(1) How long ago approximately did it become possible (feasible) for
>technological civilizations to develop? IOW, how long *have* they had to
>expand? John refers to 5 billion years above. Was it really that long ago?
>Were there heavy element planets around back then?
John, I think, is talking specifically about terrestrial analog societies (which, granted, is easier than looking objectively at _all_ the possibilities). The thing is, we don't really know. The possibilities are staggering, and aren't restricted to "heavy element planets." Creatures composed of dark matter, for example, haven't even been mentioned.
>(2) John states that it would be obvious to anyone with eyes that the night
>sky was engineered. Could he or someone else expand on this a bit or give
>me a reference.
There is no reference other than speculation...at least, none that I'm aware of. John thinks that advanced societies will more or less inevitably use their technologies to create giant artifacts out of stellar raw material, etc. There have been attempts to locate giant cosmological artifacts, but so far no luck. One theory is that the giant black hole at the center of our galaxy is some sort of industrial accident left by an alien civilization (which, by the way, would have been killed off...one of the guiding notions of the nanotech-hypers is that once a nanotech civilization emerges, it's necessarily here to stay. I think this is a particularly premature notion).
...In fact, I'd be willing to argue that _some_ of this mantric insistence on imperishable, galaxy-spanning supercivilizations is representative of a kind of postindustrial God-wish. It has the earmarks of an embryonic religion, composed of absolutes ("galaxy is engineered" vs. "there are no aliens"). This climate is very good at fostering allegiance. I've yet to see any evidence that it can encompass objectivity, as well.