Like everything else, time is either abstract or practical. Abstract time is flowing towards us from the future and disappearing into the past. Practical time takes the past and carries it with us into the future: we build the future out of the past.

The present moment is the connection between the past and the future. It is nothing in itself but a maze of connections. Viewed abstractly, it is constantly disappearing and can’t be pinned down. Viewed practically, it is always before us, like a bow wave.

Practical time is measurable, but only by dint of ignoring the abstract problems of the direction of time (that is, the constant disappearance of the present moment, or in fact its non existence). Practical time admits the existence of the present moment, but ignores it in the process of measurement.

The simplest answer is to accept that time flows in both directions, past>future and future>past. Maybe even in a loop. The possibility then arises of collisions or interactions in the putative present moment. One has to ask therefore if time travel is an abstract or a practical possibility.

Time travel depends on the existence of the present moment. Is it in fact the blink of an eye, as imagined by Kierkegaard, or a miniscule chronon, as suggested by some contemporary scientists? Does it have to have a duration in order to exist?

I believe some of us can answer this question, but I don’t know Who.