Saturday, August 24, 2013

On the impossibility of time travel

I've long believed that time travel is impossible. One of the many reasons I have for it is: it violates the conservation of mass/energy (something disappears from the universe at moment A and something appears in the universe at moment B).

Recently, I've had to reconsider this problem.

I started with an observation: the conservation of mass/energy is not violated when something moves. Formalizing this statement, an object changing its X, Y and/or Z coordinates does not violate the conservation of mass/energy. Now, if I consider that the universe is actually a 4-coordinate system, it can be inferred by analogy that an object changing its X, Y, Z and/or T coordinates is not violating conservation either. (The fact that we don't currently know any such objects is irrelevant; there was a time when we didn't have airplanes or cars.)

Of course, this isn't proof, but I wasn't proving a theorem in the first case; all I had was a thought experiment, an apparent contradiction with the known laws of the universe. That contradiction is now gone.

I guess I'll have to think more about the other 100 reasons for my disbelief in time travel...


garyt said...

though interestingly, someone who shares your surname believes that it is impossible to time travel, because in order to do so, you would have to "rewind" the correlations that make up our perception of the world. i.e. move the system back to a precise configuration it had previously. When you consider the massive number of trajectories you would have to track this, it seems very improbable. You might be able do it with an elementary particle for a very short time span in very defined conditions though.

Marcel said...

Hmm... that's a different worldview. In mine, there are a large number of universes, one for each time slice, all existing together. In the one you describe there is a single universe and going backwards in time requires indeed a "rewinding" of all events.