The Good Old Time Travel Paradoxes

To regular readers of this blog:

Please skip past any posts when you find that their contents have become repetitive. I reiterate points about Poul Anderson's Technic History, about other future histories and about time travel etc, because I find these subjects ever-fresh but I know that not everyone will! The present post is occasioned by discussions of Anderson's Time Patrol series and will as ever be an attempt to make the issues slightly clearer although they never do become clear.

(i) Think about two places, e.g., London and New York, and you think about time passing in both places. While half an hour elapses in New York, the same short interval elapses in London. We have learned that simultaneity can be relative but not between two places on Earth.

Think about two finite periods in a single timeline, e.g., the years 1066 and 2066. Within each year, time passes from the beginning to the end of the year. However, the two years do not coexist in such a way that time passes simultaneously in both of them. We cannot say that, while the Normans are conquering England in 1066, an expedition is landing on Mars in 2066. Although this is obvious when stated, I think that, when people imagine time travel, they do think of different times as different places existing at the same time.

A Danellian tells Everard that his appeal, made in 1944, was considered ages before he was born (in 1924). Do we unreflectingly think that the appeal was considered - ages ago - in the Danellian Era which begins over a million years after the twentieth century? If we forget the significance of "a million years after" and vaguely think of the Danellian Era not as an era but as a place, then, yes, we might think that the appeal was considered ages ago in that "Era."

A friend who read "The Sorrow of Odin the Goth" did not understand why Carl did not remember that he had attended Tharasmund's grave-ale. He was seen there! The event was past for some of those who had attended it so it must be past for everyone who had attended it, right? Wrong. Carl had not attended it yet.