One of my favorite science writers is Bob Berman from Astronomy Magazine. He has a fascinating column in the December issue: "It's About Time."

As Berman writes, there are basically two ways of looking at time. Either it really exists (as a fourth dimension: length, width, depth--and time), or it's a man-made thing (like the real number line).

It's a tough call. One could easily reason: "Of course time exists! Look up at the night sky where we see things as they existed long ago--and where we can predict, with complete accuracy, where they will be in the future. Why, we are literally living inside a Time Machine!"

On the other hand, one could just as easily say: "Of course time does not exist! The past is long gone, the future isn't here yet (the past will always be gone; the future will never be here). The only thing that could possibly exist is the present, or, more specifically, a quantum instant. As for time travel--forget it! There's nothing to travel to."

And that's my position on Monday's, Wednesday's, Friday's, and the weekends. On Tuesday's and Thursday's, though, I have my doubts. Don't events naturally flow from one to the other? And wouldn't they do so whether we were around to witness them or not (which would make time a dimensional entity, not a man-made one)? A world without time is not a world one can live in, either. Or perhaps "living" is itself a misconception.