In the video, Carl Sagan demonstrates the way a perfect cube is rendered in two dimensions, in shadow, its equal sides distended, its perfectly square planes skewed. He goes on to describe the "shadow" that a four-dimensional hypercube would cast in three-dimensional space--indeed, he's got a model right there with him (of course, YouTube is two-dimensional--but leave that alone for now).
It occurred to me, walking to work yesterday, that a literary narrative can be conceived as a two-dimensional rendering of three-dimensional reality. That is, with a few notable exceptions, literary narratives are told linearly--you read one word after another, turn all the pages in the same direction, and never go back.
In reality, though, we experience linear time more complexly. When I walk to the bus stop (I told my class), I go out the door, down the steps, across the driveway, through the meadow, and across the parking lot of the school next door, then stop on the shoulder of the road to wait. Linear. But my mind is traveling through time--noticing the chicken shit the birds left yesterday, imagining having to clean it up tomorrow. Noticing the broken taillight on the car from the mishap of last week, picturing myself bringing the car to the mechanic after the weekend. Recalling having mowed the meadow; anticipating its spring return.
When we write a story, we strive not to represent the linearity of time, but to evoke the way memory and the imagination extend themselves forward and back. Flashbacks, foreshadowing, frame stories, back stories--these are all techniques we use to collapse more dimensions into fewer--like Sagan and his cube, to cast the shadow of reality onto the page.