https://aeon.co/essays/the-c-theory-of- ... -direction
Ronnie O’Sullivan is an absurdly talented snooker player. When it suits him, the English five-times world champion can switch from playing right-handed to left-handed, and has even hit competition shots one-handed. But can he play snooker backwards in time? Of course he can’t. Why not? Well, there’s nothing particularly special about O’Sullivan, nor about snooker, in this respect. Think of any familiar process in our ordinary past-to-future direction, then play it backwards, and you’re faced with bizarre, improbable scenarios. With time flipped, we see a world in which shards of glass spontaneously jump off the floor into smooth wineglasses, cars suck carbon dioxide out of the air while moving backwards, and the surface of each Phil Collins LP is slowly smoothed out until no record of his music remains. As desirable as each of these processes might be, they appear not to describe the world in which we live.
When I’m watching snooker, I take for granted that O’Sullivan is playing ‘forwards in time’. But what informs my judgment? When O’Sullivan strikes the cue ball into the black ball, potting it into the corner, I can make sense of the past-to-future description of the process because it better accords with my judgments about the causal processes involved. From past-to-future, we see:
(1) a cue ball being struck by a snooker player towards a motionless black ball;
(2) the cue ball striking the black ball, transferring most of its momentum to the black ball, and resulting in outgoing soundwaves from the collision;
(3) the black ball dropping into the corner pocket and coming to rest.
If we were to run a video of this in reverse, we’d get the future-to-past version:
(1*) the pocket begins to jiggle until it forces the black ball to jump up onto the table, accelerating towards the cue ball;
(2*) the black ball strikes the cue ball at the same time as inwards-radiating soundwaves concentrate on the collision, resulting in the cue ball moving towards the snooker cue with greater momentum than that of the black ball;
(3*) the cue ball collides with the snooker cue causing the snooker player’s arm to move away from the table.
If we think of the past-to-future and future-to-past descriptions as telling us about different possible processes, we run into a problem. Whereas the past-to-future description seems to get the causal facts right, the future-to-past description seems to get them wrong. But why? There are two key things here that stand out. First, the future-to-past description seems not to respect the fact that O’Sullivan is in control of his shot. Rather, from future to past, his actions come after, seemingly as a result of, the balls’ motion. Secondly, the future-to-past description describes a series of inexplicable coincidences: the pocket just happens to jiggle in just the right way to propel the black ball upwards and along the surface of the table, and the inverse soundwaves just happen to coincide with the collision of the black and cue balls. Whereas the future-to-past description is just about intelligible, we have a clear preference for the past-to-future description due to it respecting both our ordinary judgments about O’Sullivan’s control over the snooker balls and their likely movements.
But here’s the key thing: these considerations about control and likeliness apply independently of the direction of time. Regardless of whether I show you the video of O’Sullivan’s shot forwards (past-to-future) or in reverse (future-to-past), I expect you to ultimately make the same causal judgments, namely that the video represents O’Sullivan potting the black ball into the corner, and not the reverse causal process. The key philosophical step made by the C-theory is that these causal judgments play a central role in defining and constituting the direction of time. There is, for the C-theorist, a direction of time only if there exist in nature the right kinds of patterns that make it useful for us to think in terms of an arrow of cause and effect. If we are happy to say that in a world without such patterns there would be no direction of time, then we can get rid of the question Could the world really be running from future to past?
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