I think you're right about taking the long view. A historian in the year 3000 CE won't divide our time as finely as others have tried to do on this thread, into segments of just a few years each.

But I do think that they'll be able to agree on the beginning of the Space Age, because it can be defined in very absolute, unequivocal terms: The first time a human artifact achieved orbit. Sputnik, 1957. Before that, theory; after that, space flight.

As momentous as it was that we landed on the Moon, I still hope that it's only the first step in an infinite journey. I actually hope that, someday, it'll be considered small potatoes, just a baby step, alongside whatever marvels our descendants achieve.

One advantage of taking the long view is that the dark times, on a large scale, like Carl's "Dark Ages", shrink to insignificance. Looking back a few centuries from our time, it seems like there was a similar lull, a stalling-out, in the exploration of North America, after Columbus's footsteps-and-flag mission in 1492. Made lots of headlines, but nothing substantial started to happen for another century. So maybe the Y3K historian will forgive us for letting a few decades lapse in the exploration of space.