Hawking tells us that if time travel were possible someone
from the future would have come back by now. Time is fragile. It is so fragile
that whenever anyone from the future does succeed in going back in time all of
history from that moment forward is erased. As soon as the time traveler sets
foot in the past he ceases to exist. He’s never been born. If he has never been
born, however, he can no longer go back in time. And as soon as a history
exists in which he does not go back in time, all history is restored. Does this
create an infinite loop? Not from the point of view of the time traveler. The forward
pressures of time are such that though this all takes place in a millisecond,
at the expiration of that millisecond he is already past the time wherein he
returned to the past. His only experience is that he has failed. He is still
inside his time machine, and he is still in the present. And it does not matter
how often he does this. Thinking he has failed, he may build and rebuild his
machine. Whenever it works it will seem to have failed, because time is self-correcting.
The moment of return and restoration is marked by a pause in memory, the
forgetting and remembering of a word.
What
happens to all those new histories? Nothing is lost. Each of those trips to the
past creates a branch that continues, diverges from the restored time, growing
forever in a new direction.
First, you said "As soon as the time traveller sets foot in the pase, he ceases to exist." I assume you mean "in the paste", implying he gets stuck like a fly on flypaper. Hard to argue with that.
ReplyDeleteBut you also said all future history is erased from the moment the traveller initiates a trip back - and is then restored when his trip fails. This seems like a huge amount of book-keeping, not to mention giving a lot of credit to the random hooligan who happens upon a time machine and decides to take it for a joy ride. He can erase all future history. I'm not really comfortable with granting him that much power.
So you're agreeing with Stevie that time travel can't work, but disagreeing on the details. I think he missed out in a different way. It may well be possible to travel backward, but only back to the point at which the time machine was invented. The traveller is rather like a radio wave, which can be broadcast in any direction, but can only arrive where there is a suitable receiver. Since the first receiving-machine hasn't been built yet, we've seen no travellers.
But this inevitably leads to another dead end for time travel. If someone built a suitable receiving-maching, it would instantaneously recieve ALL future time travellers who would, of course, set their dials for the furthest possible point back. Talk about Brundle-fly.
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ReplyDeletePerhaps I should clarify. Everything I said was exactly the way it really is.
ReplyDeleteI hope that helps.
Not qutie agreeing with Hawkman. Time travel can happen, but the net effect is zero in the time line in which it happens. But whole universes are created as a by product.
It's hard to imagine someone first inventing a "receiver," and only later a transmitter. But I suppose, it's thinkable. You do then have a physics problem of two people arriving at the same time and place from the past to the present, let alone hundreds.
And also, if you want to really think seriousl about this, the problem of where they're getting the molecules from since the matter that their body is made of already exists in the earlier time--not a copy of it, but the exact same molecules. So you're not really bringing from the future to the past something that doesn't exist in the past. You're returning something to a place it already exists. You're into quantum physics at this point: one molacule existing in two places at one time.