My question is simple. If anti-matter exists (which it does) is it possible to have anti-time?
I realize that time = entropy, so what reason is there that we can’t have the opposite of entropy?
Is it just something we haven’t discovered yet? Not “Backward” time but something else… Maybe in another dimension…
In the sense that “anti-future” is “past”, sure. If you mean in some other sense, then you’ll have to specify what you mean before we can say if it exists or makes sense.
Matter and time are really two different things. Time is a dimension, like length, width and height. While we might measure matter using length, width and height, the dimensions are not composed of matter or dependent on matter in any way. We’d use the same time, length, width and height to measure antimatter - or even to measure a completely empty region of space.
Anti-matter already is odd with respect to time, in that an anti-matter particle can be modeled as a normal matter particle of the corresponding type going backwards in time. (For example, a positron is just like an electron going backwards in time.) That isn’t what’s ‘actually’ happening (… uh?), but it is a useful model.
How does time = entropy? I think I missed that class. Entropy is a measure of order in a system.
Time has a direction given by the fact entropy tends to increase unless energy is being poured into a system. So, in a closed box universe, the state with more entropy occurs later (forwards in the time dimension) than the state with less entropy.