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World Lines

January 25, 2020

In Horizon, Barry Lopez writes:

A species is not so much a permanent thing as a point on the developmental line of that thing through time.

That is: the thing-ness isn’t in the point; it’s in the line.

People, too, are fundamentally four-dimensional, inhabiting both space and time. The path something takes through space and time is called a “world line”: mine starts in Oregon, in 1988, and winds its way through to the here and now. Like species, people are best described not by points, but by lines.

On some level, this is obvious: we’re all aware of a sense of temporal trajectory. But we also tend to feel that we exist now: that our being is located in the present, with only memory and expectation in the past and future. What’s interesting is to think of the four-dimensional self—the world line—as the location of thing-ness, more real than the three-dimensional present.

For an object of n dimensions, you can build a corresponding object of fewer dimensions by projecting the object into a space of lesser dimensionality. (A three-dimensional cube, projected onto a two-dimensional plane, casts a two-dimensional square as its shadow.) You might think of your present self as the three-dimensional projection of your four-dimensional world line. It’s not who you are: it’s just what you experience (projected onto the three-dimensional now). Who you are is in the world line.

What I like about this is that it robs time of some of its sting. The reality of a world line entails the reality of more than just now: in a four-dimensional object, no time slice is more or less real, regardless of where (when) “now” is. The reality of a world line means that the past is not gone: it just looks that way from here. The past is a peer of the present and of the future; far from being vanished, it is meaningful.