Friday, 3 February 2017

Walking Back

I have to disagree with a fictional incident as described in Alan Moore's Jerusalem (London, 2016), pp. 999-1000.

First, imagine that I walk from point A to point B and then return. I depart from A at 1:00, arrive at B at 2:00, immediately turn around and arrive back at A at 3:00. Of course, I neither meet nor briefly converse with myself shortly before arriving at B.

Secondly, imagine that I can walk backwards in time:

depart from A at 1:00;
arrive at B at 2:00;
immediately turn around;
arrive back at A at 1:00.

In the second case, I would be passing myself at every moment of the outward and return journeys.

In Jerusalem, Snowy Vernall walks, carrying the eighteen-month old May on his shoulders. (They are ghosts whose ectoplasmic bodies are permanently the size and shape that their material bodies had when they died.) Snowy and May inhabit a space of at least three dimensions. (Other dimensions are mentioned but we can only visualize three.) Their (at least) three spatial dimensions are, of course, backwards-forwards, left-right and up-down. Snowy walks along a very long corridor. The world lines of the mortal world are below the floor of the corridor and parallel to it. Thus, Snowy's backwards-forwards spatial dimension corresponds to our, not his, temporal dimension. Snowy has a temporal dimension. He perceives, thinks, talks and walks. All of these activities take time. His temporal dimension is at right angles to ours and might (or might not) correspond to one of our three spatial dimensions. He should no more meet himself on his outward and return journeys than I do when walking from A to B and returning to A.

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