The hand that stretches the bow must open like a child’s hand opens. What sometimes hinders the precision of the shot is the archers over-active will. He thinks: “What I fail to do will not be done”, and that’s not quite how things work. Man should always act, but he must also let other forces of the universe act in their own due time.
-Eugen Herrigel
There is a list somewhere that contains the ‘unsolved problems’ in physics. One of these problems is trying to understand the distinction between past and future. On the surface it seems kind of trivial, but when you actually try to analyse it and apply some math to it, it becomes more difficult. Much more difficult, or so it seems.
The Arrow of Time is a concept that pertains to the asymmetry of time. In other words, time appears to have a flow or direction; and that flow is nominally in one direction. Using English language words… from the past to the future. Cause precedes effect. Depending upon which branch of physics (or philosophy) you look at or subscribe to depends on how this arrow of time gets interpreted. In thermodynamics they are really big on Entropy. This is a measurement of disorder and it most certainly increases with time. It is indeed the very stuff of the Second Law of Thermodynamics. This Entropy business at a fundamental level is the basis for almost (but not all) discussions about the Arrow of Time.
In quantum mechanics when a wave function collapses (Remember Schrödinger and that hapless cat of his?) it seems that they probably collapse to a state of higher disorder or entropy. But you can argue the toss all day long as to whether the wave function collapses because of the Second Law, or if the Second Law exits because of the collapse of the wave function. However… and there always appears to be a ‘however’ associated with things quantum; quantum evolution is governed by Schrödinger’s equation which is by all accounts is time symmetric.
Those cosmologist fellows point out that the Arrow of Time clearly points (as good arrows should) in the direction of the expansion of the universe. At least for now. If the universe ultimately stops expanding and starts contracting into the so called ‘big crunch’; then the Arrow of Time will reverse direction at least from a cosmological perspective. This means that entropy will actually start decreasing. Will we then begin to see broken eggs reform themselves and the like? Who knows? There are a lot of if’s and ins and outs going on here. One of the big ones will be of course ‘if’ mankind is still going to be around in some form to witness it.