A Systematic Solution to the Arrow of Time Problem
This century old problem in physics is not fundamentally about why entropy increases. The deeper issue is that two different kinds of reversal have long been treated as the same: reversing temporal direction itself, and reversing a physical history while temporal direction remains fixed. They can look very similar mathematically, but they answer different physical questions.
Once these two kinds of reversal are separated, many problems that were previously mixed together become much clearer. Entropy increase and macroscopic irreversibility can explain why physical processes display a direction, but they cannot by themselves tell us which direction is the future. The various arrows of time in radiation, quantum physics, and cosmology no longer need to explain the same thing. They address different levels of the problem, allowing the arrow of time problem to be solved systematically.
