Thread: if time travel were possible...

Originally Posted by RedfishBluefish

WRT paradoxes... my hypotheses are:

1.
Quantum mechanics. The unobserved universe/timeline is a superposition of all possible universes, none is more true than the others. When you send the bombs back to kill yourself, you have already observed that you are alive, and were not in fact killed by the bombs. This caused the universe to collapse into a state where all the possible timelines, in which the attempt on your life succeeds, are ruled out. I don't know if I explained that very well at all .

This is still the same argument, you're just dressing it up with quantum super-position. The question is, if I send the bombs back in time to before I had them or even started acquiring them, where do they go? Just their appearance would be sufficient to change the past and hence the future. So any time travel at all, in the universe that you are describing, still creates paradox.

If you want to dance around it with quantum physics, you have to go to the full multiple worlds interpretation where all the states continue to exist even after a measurement and some as of yet unspecified mechanism prevents us from ever seeing more than one of them.

Originally Posted by RedfishBluefish

2.
Another hypothesis (my own, I've never seen it anywhere else yet). There is space-time, which is really like a big 4d block of space that sits there, with our subjective viewpoints moving forward through it. There is also "meta-time" which allows us to move in time. Meta-time is not a dimension, there is no meta-past or meta-future that exists anywhere.

What happens is space-time is like a cellular automaton (but of course not cellular since there aren't any cells ) which runs according to some rules which we do not know about. It is "meta-time" which allows the automaton to run.

Your notion of meta-time sounds a lot like McTaggert's A-Series. Also, the notion of quantized spacetime (i.e. cellular automaton) is all the rage in non-string theoretic attempts to find a theory of quantum gravity. It might even end up coming out of string theory. I don't know the math of string theory though. Quantized spacetime does seem highly intuitive though. A lot of very smart people seem to be coming to it and it seems like it can be related to the holographic principle and entopy but nobody has figured out how to do it yet.

I have to run at the moment, but I'll read the rest of your post later. Good stuff.

Originally Posted by PhilosopherStoned

This is still the same argument, you're just dressing it up with quantum super-position. The question is, if I send the bombs back in time to before I had them or even started acquiring them, where do they go? Just their appearance would be sufficient to change the past and hence the future.

The most elegant solution would be that the person that finds them later sells them to you.

Originally Posted by Licity

The most elegant solution would be that the person that finds them later sells them to you.

Your missing the point. I'm sending them back in time to my precise location at the time. I'm the one that finds them. But I send them back in time to a point where I didn't find them. So there must be a paradox or the time machine must not work.

Originally Posted by PhilosopherStoned

This is still the same argument, you're just dressing it up with quantum super-position. The question is, if I send the bombs back in time to before I had them or even started acquiring them, where do they go? Just their appearance would be sufficient to change the past and hence the future. So any time travel at all, in the universe that you are describing, still creates paradox.

If sending the bombs back at all is a paradox then you cannot send the bombs back. By knowing and having observed the past the waveform of the particles in your brain will have collapsed into a state where whatever superpositions are even there are only of those states that do not cause you to decide to kill yourself. It would work by exactly the same mechanism whereby an electron collapses into one of the possible spin states, because that all the others contradict the observations of your equipment, and are therefore eliminated.

What it might come down to is that by this interpretation time travel becomes impossible, because all time-travel causes paradoxes which eliminate themselves from the universe.

Heh, it seems like the more we learn/think about time travel, the more it looks like something impossible, or something we wouldn't want to do even if it was possible. Under many-worlds, there's the "philosophical problem" that the people people in your new universe are not the people in your own - and of course, there's no way you could go back. Under "paradoxes can't exist" it's looking like that would make useful time-travel impossible anyway. And under "meta-time" there's an unknown chance that you will destroy the earth or the galaxy by accident, or even create an expanding sphere of pure chaos pretty much ending the laws of physics as we know them.