Friday, November 24, 2006

Is the time dimension optional?

Recently, I woke up to a brief account on National Public Radio on a meeting of theoretical physicists at U.C. Santa Barabara. Some of the string theorists had proposed the idea that there may be certain parallel universes that do not have a time dimension. I found that idea rather disturbing. Perhaps my discomfort was heightened since I had not fully awoken and, at the time, I got the impression that the statement had been to the effect that the majority of parallel universes probably did not have the time dimension. After checking out NPR's web site, I am relieved that the contention did not go quite that far. No agreement was reached that there are actually any such potentially deficient universes around. And, when I think about it, maybe I am letting my earthnocentrism get the best of me. Maybe my thinking of a time dimension as essential results from lack of flexibility in my perspective.

Superstring Theory fascinates me, and I will admit to the reality that it does so in part because I do not understand it. The idea that the universe must have at least nine or ten dimensions for certain mathematical to play out appeals to me. Even if those dimensions have, for all practical purposes, collapsed, having those extra dimensions seems rather cool to me. Wasteful, perhaps, but still rather cool.

The idea of certain universes lacking a time dimension is more disturbing, however. Were they always there, or does that question even make sense? It just does not seem morally wrong--or at least overly stingy--that these universes have not been endowed me a time dimension.

When I reported the idea of members of my family at a recent celebration of my Grandmother's impending birthday, none seemed particularly concerned. In fact, no one even showed any discomfort at all. Maybe they did a good job of hiding it, or maybe the idea needed to sink in before it had any impact, but I was rather disappointed with everyone's apparent lack of empathy for these poor universes.

A number of years ago (on a trip to China, if that has any significance), I discussed the idea of parallel universes with someone who had a background in physics. He suggested that if we would not be able to detect such universes, perhaps they do not really "exist." [The quotes are mine.] That, too, seems rather cold.

Why are these universes known as parallel universes rather than, for example, perpendicular ones? It may be that there can only be a finite number of perpendicular universes, but if other universes may have a different number of dimensions from ours, maybe that is not a relevant question. Also, it is my understanding (admittedly a rather vague one) that in certain forms of non-Euclidian geometry, the term parallel takes on a somewhat different meaning, with all lines meeting at some point in space (presumably because of some relativity like space curvature), so maybe the distinction is not that relevant. If it is, however, could it be that there are both parallel and perpendicular universes? If so, what at there differences between the two kinds?

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