Have you ever tried to describe time? I tried it last night and found it quite difficult. No doubt different people would attack it from different angles, but every time I came around a corner in my explanation I found out I wanted to use time to define time:
"Time is the passage of. . ." Ooops. No.
"Time means moving. . .um." No.
"Time is a movement. . .forward? Where to? How would you characterize the movement of time as opposed to movement through space? Well, for one thing, time goes on moving whether the creatures in it are moving or not. . ." And then the vague picture in my mind of an endless, merciless river roaring through the quiet room, foaming over Now and carrying the world away, with no chance of anchorage. As soon as you realize it's Now, Now has become Then, and it's behind you, and time. . .well what *is* time, anyway?
Perhaps I had better leave physics alone for a while.