If a person who can time travel where to read this story today and email these guys before August 2013 as requested would the story automatically change to say they got 1 reply? Would I remember that I had read the story with no reply received or would I now remember that they got 1 reply? Or would I need to re-read the story to see that they got a reply? Does the fact that they’ve had no reply mean they’ll never get a reply or is it possible that a person who can time travel will reply once they read the story?
Isn’t it true that you cannot change something that happened in the past? For example, if you went back to when your dad was a child there is no way you could kill him because that would mean you never existed? So you could try to kill him but you would never succeed?
But it didn’t exist yesterday so it can’t be moved then. What we’d actually need is for someone to tell me yesterday were to post the original post so that I’d know where to put it and there would be no need for it to be moved.
I once read an article that argued that time travel was inherently self-negating. The argument went that you start by supposing that time travel is easy. Say that discovering how to travel in time is no more difficult than invented the steam engine. And once time travel is invented, people use it. They travel into the past and change events. So pretty much every time it’s used, history is being changed. And with time travel being so easy, history is changed millions of times. And eventually with all of those millions of different pasts, the world stumbles into a history where time travel isn’t discovered. It doesn’t matter how easy time travel is, there must be some chain of historical events where it isn’t discovered. And if the world lands in that pattern one time, it stops - because in that history there is no time travel and that means there are no further changes in the past.
Cute idea, but I think you’re wrong. You are confusing time travel being impossible with time travel being discovered.
In other words: As you describe, it is quite likely that with all of those millions of different pasts, the world would stumble into a history where time travel hasn’t been discovered yet. But tomorrow it might get discovered. Or next year. Or eventually. But it will happen - unless it is impossible. And for it to be possible in one sequence of events, but impossible in another, doesn’t make sense to me; you’d need not merely a change to events, but some sort of change to natural law.
By the way, it seems to me that in Little Nemo’s scenario, it doesn’t really matter whether time travel is difficult or easy, as long as it is possible. The only difference between difficult and easy, is how long it takes from the first invention until it is ubiquitous, which does not affect the main logic of the argument.
I suppose if we needed a certain rare element in order to time travel and ppl from the future used the whole supply of that element to travel back in time then needed to use the whole supply of the element in the past to travel forward again then time travel would never be discovered since the complete supply of the element would have been used in the past b4 time travel was possible.
That was a major plot point in several episodes of Seven Days. Headquarters used Element 115 to send the time traveler a week back in time, and that used up the entire supply of Element 115. But the time traveler ends up in a new timeline where – from the perspective of the people at Headquarters – the time-travel device has never been used yet, and so they have what they need.