Not as glamorous because they could still be seen.....just not by the mines. It was a very important none the less.
No problem.....it helps reading military history first. Except for flight 19 and the Nazca Lines I was reading about history a number of years before getting into anything to do with UFOs.
I would think any interaction at all, no matter how minute, would change the future if someone really traveled to the future of their timeline and came back... ...
I heard a story that someone who had access to time travel went back in time and killed his grandfather to disprove the grandfather paradox. When he returned he was hit and killed by a bus. Maybe people in the future are taught how to deal with time travelers.
Perhaps he just killed the grandfather of his counterpart and did not really travel to our past but went into the past of a parallel universe and was not aware of it...assuming the story is true of course.
Time Enough for Love - great book! One of my favorites. Always wondered if Heinlein had some genuine and disturbing sexual .... I don't know what .......