User talk:CaptainTybusen/Time Travel Theories/@comment-47205-20100919084438

No, I don't like Many Worlds (or, in this blog, the "multiverse" theory). But then again, I've never been a fan of the idea of alternate universes, and a lot of the more abstract parts of quantum mechanics just seems like the result of bored and arrogant physicists to me. No offence. :P

I also don't believe that any ontological paradoxes are possible (e.g. somebody goes back in time to investigate something, and causes the event that they went back to investigate). The universe obviously tends towards causeless time travel events not happening, or otherwise all of those people who've planned "if I ever discover the plans for a time machine, I'll visit myself at this time and give them to myself so that I can make my own time machine!" would then find themselves with the plans for a time machine (and possibly the means of aquiring the resources, because presumably the top-secret installations in the 21st century where they keep all of the unobtanium will be easy for somebody with 26th century technology to break into). Since that doesn't happen (and yes, it would happen every time; ontological paradoxes are bad enough when it's not arbitrarily decided which ones happen and which ones don't), we can assume that the universe tends towards inaction as far as these things are concerned.

The "continuum" theory either works by using ontological paradoxes, or it requires some sort of intelligent being monitoring the timeline. Which I suppose is possible, that would require a whole other discussion.

My idea is closest to the "paradox" theory. My ideas about how time travel would work are constantly changing, but I'll try to explain my most recent hypothesis. This would be easier with a diagram, but I don't have one available and don't see the point in making one right now.

Anyway. The best way to imagine this is to think of three timelines. Each "timeline", by the way, should probably be visualised as a "map" of all of the matter in the universe constantly changing as you go down the timeline. One timeline, the longest, is the "true" timeline. The other two are "perceived" timelines. Both "perceived" timelines look mostly identical, going from the start of the universe to the present day, but there's two main differences. The "second" (or "current") perceived timeline changes at one point, where a time machine and time travellera appears and affects the course of history. In the "first" (or "original") perceived timeline, it abruptly ends where the time machine and traveller go back in time. Yes, this is another possibility of time travel in which time machines result in the end of the universe...

As for why the timelines seem to do this, you'd need to look at the "true" timeline. It starts at the beginning of the universe, and looks exactly the same as the first perceived timeline. However, instead of suddenly ending, when the time machine activates the timeline suddenly changes to how it was so many years ago, with the slight difference that there is a time traveller and a time machine in one location. This then leads onto the second perceived timeline; on the true timeline, the second perceived timeline after the point of divergence appears to be attached to the end of the first perceived timeline.

To everybody other than the time traveller, the history of the universe is that of the second perceived timeline. The first perceived timeline - and by extension, the universal timeline - is inaccessable, only existing in the time traveller's memory.

One of the advantages of this "timeline theory" of time travel means that temporal paradoxes do not exist (I've already talked about the ontological paradox earlier on, so I think that mainly leaves grandfather-type paradoxes). A person could go back in time and kill their grandfather before their father was born, but in the true timeline, their grandfather lived and had grandchildren, so the chain of cause and effect was never actually violated.

I'm not sure whether the timeline model used in this description should be considered as being an accurate representation of the theory, or whether it's just an aid to help people visualise what is happening. If the former, it does mean that it is not "real" time travel, but instead more like the rearranging of matter of recreate the universe as it was before. If the latter, then I suppose there's no problem with it.

Either way, there may be the issue that such time travel to the past would require practically infinite energy (I'm not sure; I haven't tried doing any calculations). That shouldn't be a problem, apart from the ideas of using wormholes and cosmic strings for travel into the past. On the subject of wormholes, is that idea based on the one about "dragging" one end of a wormhole across the universe at high speed, thereby subjecting it to extreme time dilation? My solutions to that are either a) Wormholes don't exist (since, as far as I can tell, their possibility requires a fourth spatial dimension that can be warped in such a way as to allow a wormhole, and I'm not sure what theories there are that actually have any extra dimensions that are large enough for that), or b) It's impossible to actually move one end of a wormhole through space. As for cosmic strings, I'll have to do more research on that, but my best guess at the moment is that 21st century physics isn't entirely accurate. But like I said, I'll have to look into it.