The past is partly known and completely immutable. Our understanding of World War II can change but not the fact that there was a World War II with certain dates, certain major events and turning points and many details, known or unknown. It is conceivable that someone might seem to himself to have been transported from 2020 to 1940, thus to be living among the events of World War II. However, if he makes the events of 1940-1945 different from the way that he remembers they were recorded, then, wherever or whenever he is, he is not in the World War II that is part of our known history. There must be some other explanation of his experiences.
All this has been discussed before, of course, but maybe we can clarify a principle? The proposition that the past cannot be changed applies not only to our familiar experience of time but also to any time travel scenario. Travel through time would involve travel to the past and the past cannot be changed. Anyone who, e.g., assassinates Hitler in 1940 is not in our past, therefore has not time traveled.
5 comments:
Kaor, Paul!
And any assassination of Hitler (or Stalin, for that matter!) in our 1940 would not have changed our history, rather, another and different timeline would have split off from that event.
Ad astra! Sean
Sean,
From the moment of the assassination (at least), the time traveler would not be in our past. But a simpler view is that he was not in our past but in an alternative reality in the first place. Timelines (entire universes) splitting off from each other are a very complicated idea.
Paul.
Kaor, Paul!
The idea of timelines/universes splitting off from each is worse than complicated--it hurts our heads when we try to make sense of such ideas!
But we have strong reason to believe alternate worlds actually do exist, because of the implications and consequences of quantum mechanics. And discussed by Poul Anderson in that fictional preface to THREE HEARTS AND THREE LIONS. And by writers as different from each other as Frank Tipler and Sean Carroll.
Ad astra! Sean
As far as I understand the Copenhagen interpretation of quantum mechanics, all possibilities exist simultaneously and always have.
Kaor, Mr. Stirling!
So "somewhere" Hitler and Stalin WERE assassinated.
Ad astra! Sean
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