Why do humans experience time's arrow, even though actions are indestinguishable forward or backward in time?

Answer 1

The equations of motion are time reversible (sort of). However, to solve any problem in physics, you also need to know the initial conditions of the problem. The statistical directionality of time traces its origin to the low entropy of the initial conditions of the universe. No one knows why it was so, but given this, it is more likely for states which subsequently evolve to have an ever increasing entropy. Since entropy is a measure of how many different ways things can be, this means things in the future are more poorly resolved than things in the past. Conciousness is based on the ability of the brain to model the physical world (create a "picture" of it, so to speak). As a result of the temporal asymmetry of the world's resolution, our brain's ability to model things in the past (aka memory) greatly exceeds its ability to model things in the future (aka prediction). This asymmetry creates the perception that the past is more fixed, determined, or "real" than the future.

Answer 2

I believe Brian Greene summed this up in the Fabric of the Cosmos. I read that a while ago but it has something to do with entropy so guy with the other guy's answer who mention that! From a philosophical standpoint does it? Maybe it's circular. Maybe when the universe starts compacting everything will happen in reverse order. Probably not though-we'll just smash all up into nothing.

Answer 3

Time reversal invariance is not the same as time symmetry. Consider a basic thermodynamic engine. It has a certain efficiency <1 (less than 100%). True time symmetry would admit hyperefficiencies >1, related to dS/dt < 0 (time rate of entropy). Put two reservoirs at the same temperature in contact with each other and they would spontaneously retreat to two different temperaures on either side of the initial one.

Answer 4

Actually entropy tends to increase forwards in time (even though it should be symmetric in time, kind of a mystery). That way when you see a video of an glass shattering you can tell which direction time is going, shards of glass are unlikely to assemble spontaneously into a glass.

Answer 5

Maybe there's more to existence once you get past the bag of genetics in which we reside - Who's to say that once you drift out of one roller coaster you wont get sucked into another one going a different way. Is there really such a big difference between plants and animals? - maybe bodies are just a natural progression of some evolving chain reaction and maybe we just pop up in the middle somewhere when it's comfy enough to ride in - do we jump out of our skin before the body dies or after?

Answer 6

causality is your answer.

"actions are indestinguishable forward or backward in time"

Since when? Maybe at a subatomic level, but in the real world, that's an erroneous statement.

Obviously, you've never been in a hostile fire zone.

Answer 7

Actions may be indistinguishable,

but

the SEQUENCE of actions is distinguishable
(maybe even unique.)
.