On the distinction of past and future: could one theoretically reverse direction of particles and cause time to appear to go backwards? Based on my understanding of physics after seeing The Distinction of Past and Future on Project Tuva, there is no distinction between past and future on a fundamental level- all particle interactions can occur in reverse. So my question is whether or not one could theoretically reverse the direction of all particles in the observable universe relative to each other and have time essentially go backwards indefinitely.
If you think about it, things could "fall" upwards because the air resistance would be much lower due to the way the air was moving when it fell, and the velocity from the gravity downwards would be reversed as well as air under the ball pushing up (again due to the way the air was moving previous to the switch). I don't see why this same logic couldn't be applied to a more complex system.
Does this logic make sense? If not, where is the flaw? What other constraints would need to be added to make time essentially go backwards other than reversing direction, if it is possible at all, in theory?
 A: Yes, as you say, there is a built-in time symmetry in the mechanical laws that underlie our universe. At the moment the most accurate statement seems to be CPT symmetry. Under a CPT reversal (particles -> antiparticles, flip space, flip time), mechanics works identically. On a practical level though, even time symmetry alone holds to a good degree.
It is of course very theoretical. Even in a simple classical picture, you would have a lot of trouble getting in there and reversing all the motions of every molecule.
Quantum mechanics adds even more complications to the requirement of reversal -- it's not enough to just reverse the motions of particles, but you actually have to preserve all the complex wave correlations (entanglements) between the particles. But there's the trick: you can't observe those entanglements, so you need some sort of sneaky time-flip operation that does not involve observation. Moreover, once you observed the time-reversed system you would induce decoherence and destroy its reversed-ness.
A: Full reversibility at the elementary level does not imply what you suggest: new qualitative features appear as the scale of the system and its ability to interact with the rest of the world increase, so that dissipation (irreversibility, loss of "useful" energy) at the level of our everyday experience does not contraddict microscopic reversibility. 
If a drop of ink falls into water and diffuses, you still could not (in a sense made accurate in Statistical Mechanics) reverse all the particles' motions and recover the original drop, the rest of the world being left unaffected.
