"Science is beautiful and if you don't like it - f*ck off!", R.Dawkins
Once in a while I like to contemplate on highly useless things, 'cause I think that's fun and feeds human curiosity. Oh well, let's roll out sc-fi classics - time traveling!
Talking about time traveling, there are many speculations on the mechanics and physics of the process that lead to certain paradoxes and the problem is, that one can't be sure which way it works - 'cause there are no observable evidences of time travel to the past. What's been troubling my mind recently, is grandfathers paradox (I wonder why it's not simply a "fathers paradox"?), which says that if one travels back in time and slaps his beloved grandpa with a "Quantum physics Vol.I" so hard that poor fellow loses interest in proceeding with his life duties, let alone having children, then... what would happen to the time traveler? Would he still exist? Well, he just broke his heritage line, didn't he?
As a computer science expert I see a problem with this paradox explanation, - there should exist some complex information processing mechanism to remove time traveler from universe (and his father and children if any), once his grandfather has been eliminated. And how would particles forming his body cease to exist? Just simply pop out of existence? But these particles are not special, they just happen to be so lucky to get into one place and build time travelers body.
Alternative explanations, e.g. parallel universes/timelines and Novikov self-consistency principle doesn't look too promising either. Well, they explain the paradox, but then bring serious task to explain how they work at information field level.
So here I come, one more speculation to explain time travel paradoxes. It is often considered that time is a fourth dimension of space-time continuum, however there's one main difference between Euclidean dimensions and time - all known particles are moving only forward in timeline, but they can move in any direction in space. To be very precise, timeline direction points towards increased entropy, which brings us to a finding that traveling backwards in time reduces entropy. Stephen Hawking has kindly explained all this in such a style that even dummy physicists like me could grasp the idea. And I make a conclusion here, that if time traveling to the past is possible, then either information field should memorize life-time of each particle in the universe (that's about 13.6 billion years!) or there exists a mechanism to move particles backwards in time. And again - the first way has problems to store gazillions of information, and the other one has to deal with uncertainty principle somehow. Or maybe when time is moving back, there's a symmetrical "Certainty principle" that can state where and how particles are returning? These are the weakest parts in my theory, but if somehow they survive, I shall continue with my idea.
I find that traversable wormholes are most realistic (but still theoretical!) time traveling "devices", so let's illustrate how it works when time traveler enters mouth of the future wormhole. For simplicity I'll assume that time traveler is an elementary particle.
So, I made an assumption here - what if time traveling particle does not meet itself in the past and how could it happen? To illustrate I need another particle (the red one in the image on the right) that exists alongside time traveler particle, but does not enter the wormhole. Here's what red particle observes: both particles hang out around and then suddenly blue particle "disappears" in the wormhole. And the blue time traveler particle observes that red particle is sticking around, until wormhole approaches. Space-time starts bending and time traveler is seeing how time slows down for red particle (similar effect can be observed close to the massive body, like a black hole). At some point time for red particle stops (when wormhole timeline becomes perpendicular to the main timeline) and then is reversed - red particle starts moving backwards. However, note that unlike when moving forward, now it is moving alone - time traveler is in the wormhole moving forward in local space-time frame. At the end of the journey time traveler exits out of past-wormhole mouth and finds out that only red particle is here. That's it folks, no more clones and paradoxes!
So, that's particles. And how about human time travelers? The more I think of it, the more fun it looks. While time traveler is in wormhole, his absence in main timeline causes effect that looks like some eraser is removing a person from existence. The more he travels in the past, the more of his life is "erased". People are still remembering this person, shaking hands with empty space when greeting and looking at the photos of someone who will be erased soon. Okay, that looks weird, maybe even creepy :)
Post factum. It took me a week to write this post, so now when I look at it in the end, I'm pretty much convinced that traveling via wormholes is not possible at all...