Re: I think I am from the future, but I can\'t remember
axus,
Reactor made reference, appropriately, to the fact that we can move virtually in any direction in 3D space but only seem to be able to move in one direction, forward, on the time axis.
The evidence seems clear that that is the case, at least today. And there's experimental evidence to back that up.
Let's do a gedanken experiment to see what I mean:
We start from the perspective of posing a theory that all actions, reactions and interactions can be run both forward in time and reversed in time such that we start our experiment with our system in state |A>, have it evolve and at a later time end in state |B>. We then run the experiment in reverse time by starting in state |B>, have the system interact in exactly the same manner with the same "objects" but in reverse order and end up back in state |A>. The question that we ask ourselves is is this true?
Here's the experimental design:
We have a light beam emitter. It sends out a beam of light toward a mirror. The light beam is in state |A>, white light, when we emit it. It strikes the mirror, is reflected back towards the laser emitter and is detected there. Ignoring the effects of the mirror, which in our gedanken doesn't change the lights frequency in a measurable way, we determine that the reverse process is exactly the same as the forward process. It doesn't make any difference whether we run the experiment forward or backward in time. We began and ended in state |A>.
Next we change the experiment somewhat. We insert a blue lens half way between the emitter and mirror. We have the emitter radiate a beam of white light. It arrives at and passes through the blue lens. The red and green frequencies of the white mixed state |A> light are filtered out and the light leaving the lens is in pure state |B>, blue light. It arrives at the mirror, is reflected and reverses course. It arrives at the lens, passes through and leaves the mirror still in state |B>, blue light. It arrives back at the laser in state |B>.
We now think about real mirrors in the first part of the experiment. Real mirrors do affect the frequency of the light. The real world result of part one of the experiment is the same as part two. The light was altered by an intermediate interaction and reversing the time axis can't undo that effect.
Changing the frequency of the light by an intermediary action is irreversible. Running the clock backwards won't undo this irreversible process. This means that there is a difference between forward and backwards in time. It is not symmetric. The entropy of the system seems to increase no matter which direction in proper time the system moves. If the situation was symmetric then on reversing the time and running the system backwards there should be a decrease in entropy, something that non-time traveling observers never observe on the macro scale. Furthermore, if running the system backwards in tme causes an increase in entropy in the past that means that in the future the total entropy of the system was less than it was in the past, again, a situation never observed on the macro scale.
