On the 'how to warn people' front, how about a sort of granite comic?|
Show a lot of healthy humans.
Show a radiation symbol next to the humans.
Show a lot of dead humans around the radiation symbol.
Then post the usual radiation symbols further in next to the stash-o-stupid
Ought to work? So long as they aren't so far removed from us that they can't recognise 'alive creatures, then some thing represented by this symbol makes them dead'
Even better would be plowing major time and funding finding a non-retarded way to supply our energy needs, but the how to communicate over 100,000 years problems is interesting.
-- boobs do nothing for me, I want moustaches and chest hair.