While we teach our youngest children about such notions as Squares and Straight lines, we fail to tell them that these things do not exist in nature. Therefore, Squares and Straight Lines are manmade creations, concepts, tools (and obsessions).
We use straight lines because we do not know (otherwise). Straight lines illustrate our confidence, arrogance and presumed mastery over what we cannot know. We use straight lines because we are projecting; extrapolating, closing gaps or using stereotypes. Straight lines reflect one-dimensional thinking i.e. that nothing else will interfere—i.e. the line can "go on for ever” i.e. even if other things inevitably) interfere. When using straight lines we artificially block out all sorts of realities in order to justify the myth that the straight line “says it all.”
To most of us, light travels in straight lines, except when it doesn't. And it doesn't when it is bent (tipped, modulated and/or influenced) by gravitational fields.
We use straight lines to point. But even if we point to shoot, as with a firearm, most of us do know enough to realize that the trajectory of the projectile, while more or less straight, is influenced (“tugged”) by a second factor namely gravity, which gently "pulls” (“coaxes”) the projectile into a parabolic curve. Of course, as with a bullet, wind currents can also “spoil” our straight line over simplicity.
But straight lines are even more sinister and dangerous when they point to our own ignorance and assumptions. We often point to extrapolate and pretend to know about what we do not know. A straight line is typically evidence of our pretense and egotistical arrogance.
Take for instance a plot or legal description of a parcel of real estate that may have as many as 19 sides and a total perimeter of several thousand feet. When we plot it, we may discover a “closing error” of, say, 67 feet. With this, since the 67 feet may be on the order of 1-2% of the perimeter, we deem it safe, prudent and wise to close the gap” with the straight line that joins the gap, not realizing that there is no evidence whatsoever of the underlying reality reflected in that“cheating maneuver.”
We see some economists with four points posted on the x and y axes that seem to demonstrate some alignment (truism) and we project a line through those points both above and below and, in effect, predict other hypothetical outcomes based upon other x and y variables. This is called prediction, prognostication or extrapolation. And it is nearly always wrong, in large part, because the there are more than two dimensions to reality and thousands of unconsidered variables. The world is hardly as simple or self-deceptive as our minds which, in lazy fashion, attempt to “outsmart” nature and the ways things are. and reduce the world to near comic simplicity.