How is Thornton Wilder's manipulation of time and use of flashback in Our Town effective?

One of the
play's themes is that our lives, which seem long and important and special to us, are mere
blinks of the eye against eternity. As the Stage Manager says, there are the same names on the
tombstones in the cemetery as there are of people living now: no one of us will be around very
long.

Yet, at the same time, the play has another point to make: our lives
might be over in the blink of an eye, but human life is meaningful and important. As the Stage
Manager says,

We all know that something is eternal. And
it ain't houses and it ain't names, and it ain't earth, and it ain't even the stars... everybody
knows in their bones that something is eternal, and that something has to do with human
beings.

What is eternal is the human spirit.

The manipulation of time in the play makes that theme clear. Going from a scene in
which people are vibrantly in the middle of life on earth, pulsing with hopes and dreams and
concerns, to a scene with these same people are dead and in the afterlife packs an intense
emotional punch. It accentuates how brief life is and also causes us to mourn the lives of the
characters that have passed so quickly. It helps reinforce the play's theme that we should try
to appreciate and live the life we are given in the here and now with joy and consciousness, for
there is no going back, even if we try.