"Facts are stubborn things, but statistics are pliable"
-Mark Twain
All theories of microscopic physics are governed by laws that are time reversible. Evolution of a system can be traced back into the past by the
same evolution equation that governs the prediction in the future. Then the macroscopic laws arise, and we see that there is indeed something
like an
arrow of time, indicating that the macroscopic phenomena, unlike the microscopic ones, are not invariant under reversal
of time, due to the second law of thermodynamics. In other words, both Figure 1.a and 1.b seem reasonable, whereas Figure 2.b
seems quite
impossible. So the natural question arises, how come the laws that govern two atoms are invariant under time reversal, i.e.,
Figure 1 makes sense in both directions of time, but Figure 2 doesn't?