In Let the Great World Spin, why do the stories of diferent characters keep weaving in and out, skipping chapters?

Let the Great World Spin, by Colum
McCann is constructed episodically to show time and life in motion. Picture eleven
rivulets slowly pushing further from a source of melting snow. All rivulets are arranged
around one central sphere that they will all reach as more snow melts and pushes their
course forward toward the center. At the center is the event that thrusts them all
together. It will be the central junction where all meet. In this metaphor explaining
McCann's structure, the tightrope walker is the clock that all time moves in accord
with. So the walker, besides being a tightrope walker having a great adventure, is two
things: he is the background for measuring the movement of the rivulets and he is the
measure of the progress of time.

McCann weaves from one
character's story to another and back and forth again so you can see how they are
progressing according to the one clock that unites them--the tightrope walker--and so
you can see how they are all moving toward one central point, the point at which all
their lives, lives of friends, family and strangers, all converge at a central
destination against the same backdrop of the tightrope walker's adventure and at the
central, pivotal event in the story. They progress slowly, as slowly as the tightrope
walker, so you check the progress of one group of rivulets, then another, then another,
then back to the first.

McCann has created a expansive and
extended metaphor in Let the Great World Spin. Even while the
related and unrelated people of New York watch the 110-story-high tightrope walker move
slowly from a starting point to an ultimate destination, the reader watches these eleven
people do the same thing as they move slowly from their starting points to their
ultimate destination where they then collide with each other, metaphorically and
literally. When they arrive, all unrelated lives, like Lara's, flow into other rivulets
until all lives are united, just as the tightrope walker's rope and act unite the Twin
Towers. The final union occurs when Jaslyn, who was raised by Gloria, who knew Corrigan
and Tillie, goes to call on Claire. It is significant that they rest together at the end
because the journey is finished; the last rivulet has joined the center: all are united.
McCann brings a final comfort and ease to disrupted and at some times tragic
lives.