“Why do I think time moves forward instead of backward?”
Basically, because of entropy.
There are actually two questions here: first, why does time (appear to) flow at all? And second, why does it flow only forwards?
If the whole universe were composed only of a single particle, say a photon, you couldn’t even notice time passing. Every moment would be identical to every other moment. Time wouldn’t even flow.
So first you need multiple entities, in order to have change. So now let’s say you had the same single photon, bouncing forever between two parallel mirrors. Now time would flow (you could watch a movie of the photon, and notice changes from frame to frame). But it wouldn’t particularly flow forwards or backwards. If someone gave you a movie of the bouncing photon, but it wasn’t labeled which side was the start and which the end, you’d have no way to tell. There isn’t really a “forward” or “backward” in time in that situation.
So what it takes is a complex universe, with order and chaos. And then it’s just a matter of probabilities. Eggs are vastly more likely to scramble than to descramble; shattered cups rarely bounce off the floor and spontaneously reassemble; etc. The laws of physics don’t prevent these things. They’re just exceedingly unlikely. So if you had an unlabeled film, you could tell which side was the “past” and which the “future”, since in one direction all the action was extremely probable, while in the other direction every action is exceedingly unlikely.
So, in our normal, macroscopic world, we imagine an arrow of time, a past we can never change, and a future that can be altered by our free will.
Even though relativity tells us that the REAL universe doesn’t have absolutely reference frames, that time passes differently in different frames, that it doesn’t even make sense to ask whether two events apart in space are even simultaneous or not, that time doesn’t really mean anything “before” the big bang or inside a black hole, that really the whole evolution of the universe is a single fixed state vector of space-time, and time never flows at all.
But a (false) concept of linear time with a fixed past and a changable future, helps us quickly make useful decisions in our typical lives.
“Why do I think time moves forward instead of backward?”
Basically, because of entropy.
There are actually two questions here: first, why does time (appear to) flow at all? And second, why does it flow only forwards?
If the whole universe were composed only of a single particle, say a photon, you couldn’t even notice time passing. Every moment would be identical to every other moment. Time wouldn’t even flow.
So first you need multiple entities, in order to have change. So now let’s say you had the same single photon, bouncing forever between two parallel mirrors. Now time would flow (you could watch a movie of the photon, and notice changes from frame to frame). But it wouldn’t particularly flow forwards or backwards. If someone gave you a movie of the bouncing photon, but it wasn’t labeled which side was the start and which the end, you’d have no way to tell. There isn’t really a “forward” or “backward” in time in that situation.
So what it takes is a complex universe, with order and chaos. And then it’s just a matter of probabilities. Eggs are vastly more likely to scramble than to descramble; shattered cups rarely bounce off the floor and spontaneously reassemble; etc. The laws of physics don’t prevent these things. They’re just exceedingly unlikely. So if you had an unlabeled film, you could tell which side was the “past” and which the “future”, since in one direction all the action was extremely probable, while in the other direction every action is exceedingly unlikely.
So, in our normal, macroscopic world, we imagine an arrow of time, a past we can never change, and a future that can be altered by our free will.
Even though relativity tells us that the REAL universe doesn’t have absolutely reference frames, that time passes differently in different frames, that it doesn’t even make sense to ask whether two events apart in space are even simultaneous or not, that time doesn’t really mean anything “before” the big bang or inside a black hole, that really the whole evolution of the universe is a single fixed state vector of space-time, and time never flows at all.
But a (false) concept of linear time with a fixed past and a changable future, helps us quickly make useful decisions in our typical lives.
Not entropy, but rather causation; time does not flow backwards because what I do tomorrow will not affect what I did yesterday.