If we woke up tomorrow and...
jodrellblank: The last time a similar topic came up at HN, it was the "what if you time travelled back to the past" question.I didn't think of it in time for that thread, but I wanted to turn the question around: Looking back through history, if we wanted to spot a technologically advanced person appearing in the past and trying to create 'future' technology, what markers should we look for? (and ... has this happened?).