The Moving Now

It seems significant that the present moment in time is not known to physics. There is t and there is Δt, but there is no “the present t” in any equation. 

It would be wrong to say that the present moment in time is unknown to all science, however. It must at least be a topic in certain subspecialties of psychology, because human beings are ever aware of, and sometimes obsessed by, the fact that it is no longer last year and not yet next year. 

We acknowledge this central feature of our reality when we use language that evokes an image of the present as a dot moving through the seconds and centuries of an extended calendar.  The motion of the present we take to be fully described in one dimension and to be in one direction.

It is easy to tell a story about what events can have a causal influence on what other events that would naturally be represented two dimensionally. For example, imagine a graph of events in which point a can influence point b only if b is northeast of a. Imagining what it would be like to live in two dimensional time, is, however, a little harder. 

What it would be for the now dot to move backwards on our familiar one dimensional time line is also easy, at least as an initial matter.  Watching a movie running backwards is a great aid. Contra-entropic physics has its challenges, however, and I will readily concede that there may be a perfectly good sense of “physically impossible” in which that is exactly what a backward moving present would be. I would not be willing to concede quite so quickly that there is no defensible sense of “physically impossible” on which it is not. 

What about the possibility that there are two dots representing present moments working their way down the time line?   Perhaps your great great grandmother is drinking a cup of coffee in her now as you read this in yours.  Could we ever have evidence of such a possibility?  Suppose that you wake up one morning with the memory of a long and elaborate dream. In the dream you were 11 years old and went through a normal preteen day. You don’t remember everything that happened, but you remember almost as much detail as you remember of what happened yesterday in your normal life. The way your parents and your kitchen looked in your dream are not exactly the way you remember them, parents younger, kitchen larger, but nothing was flatly in clear contradiction to your memories of that time. The next morning, you report dream memories are of the next 11 year old day, and so on day after day. Eventually you are able to check details. The library archives show that the newspaper cartoons of your dream memories were exactly the cartoons published on the successive days in question. 

You may be tempted to say that this would not be any evidence of two distinct nows marching along the timeline independently but only evidence of some extraordinary ability to tap into information about a thoroughly past past. If you are so tempted, vary the case by waking up with dreams of the life on successive days of a person 100 years in the future. Again there could be suitable checks, e.g. you might know from your dreams the contents of a time capsule, whch contents fixed a week after you dreamed of its opening.   Consider next a symmetric inter-nows commuter who had memories of the day to day life of her future self upon awaking as an 11 year old as well as those of an 11 year old upon awakening as an adult. This would perhaps be even better evidence of the two independent nows, but it raises the possibility of paradoxes of the grandfather homicide class, and so is better skipped for the present. 

You can easily construct a case in which the two moving nows would be progressing along the timeline at different rates, and multiple moving nows would pose no great conceptual leap.  They might, of course, exist without our having any direct evidence of them. It would be the same reality except for the subtraction of the dream memory commuter. Reality gives no guarantee that it will provide evidence of all the features of its anatomy.

As with “physical impossibility” and backward moving time, I will readily concede that multiple nows in distinct positions on the time line may violate our “concept of time” or be a “misuse” of the word “now.” It certainly rips “now” out of our everyday employment of that word in a fashion of which Wittgenstein would strongly disapprove. I decline to take these obections too seriously, however.  Sometimes getting a better theory of the world requires serious conceptual restructuring. If we never used established words in radically new ways, we would never have gotten beyond, “Pass the acorns.”