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Saturday, May 12, 2007
Time Loop -vwv vvw

After reading SQ's thought experiment on a falling swimming pool, I was reminded of a hypothetical time travel question I posed to friends many years ago.

This is how the story goes. A young man meets an elderly time traveler from the future. The latter teaches the former the formula for time travel. After twenty years of work, the young man, who is now old, completes his time machine. He uses his time machine to travel twenty years back to pass the time travel formula to his younger self. The question was this: how many times did the event where the character learns the formula occur?

I had about ten responses and their answers were divided. Half the people said once. The other half claims infinity. Interestingly, nobody said twice.

In a way, nobody was really wrong. How many times the event occurred depends on whose timeline you are following. If you following the timeline of the majority of the universe, the event happened once. Suppose the story took place in the year 2000. Then the event took place in 2000. Not any other year, only once in 2000.

If however, you choose to follow the timeline of the character of the story, it happened twice. Once when he was the young student and once when he was the old teacher. Like I said, strangely, nobody chose this point of view.

But for the event to happen infinite times, one must have chosen the point of view of an imaginary entity that got caught in the time loop. This entity is also infinitely old since it has experienced the event infinite times and will experience the event infinite times more. If the formula was written on a piece of indestructible paper, then this piece of paper would be such an entity as it has changed hands infinite times. But since I never mentioned any physical object being passed in my story, I find it very peculiar that so many people would rather choose the point of view of an imaginary entity that was never even implied. I never could understand why people would see things this way.

So now I wonder, what if I had modified my story then. What if instead of sending himself into the past, the character merely sends a radio broadcast of the formula into the past so that his younger self would receive it? It is essentially the same story. But would I still have gotten the same results? Equally divided between one and infinity?

-- permalink --
Yiheng made
1:48 PM


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The Future Is Dismal -vwv

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