The world of modern human activity is defined by rectangles. We impose them, it seems, on every surface that we govern. Overwhelmingly, our houses and other buildings are rectangles, or collections of rectangles joined together, as are the rooms within them, the desks at which we sit, the drawers in which we stow our stuff, our books and papers. With an even greater impact sliding into modernity, our devices are rectangles, and the screens through which we perceive all manner of communication are rectangles (so much so that even The Onion observed Americans spend the vast majority of each day staring at, interacting with, and deriving satisfaction from glowing rectangles).

Why not circles, or ovals? Our food and drink, fundaments of our very survival, are so much more likely to be consumed from a circle, so why not circular movie screens and TV screens and cell phone screens as well?

The answer to that one is probably biological. We have two eyes, protruding from our skulls in fixed positions, on a level and parallel to each other. Try this as an experiment. Stare straight ahead and hold both arms out to your sides, moving them back until you can no longer see your hands with your peripheral vision. Move them up and down, see how far back they can go at any particular height. Do the same thing holding your arms above your head, moving along the frontier of your vision above. What you'll notice is, despite the roundness of your eye sockets, your field of vision is a rough rectangle! And so we are attuned to a rectangular display feeding information to us from the moment our eyes adjust to the world.

And so, if your TV screen came with semicircle flaps on the top, bottom, and sides, so the information conveyed was suddenly increased by the addition of information showing on those additional surfaces, making the whole of the screen into a circle within which the original square neatly fit, you'd feel as though you were getting less information. Why? Because your mind wants those missing corners filled in. Those corners represent danger the primordial predator lurking just behind an obstacle obstructing your field of vision!! From your living room TV screen to your cell phone (which, by the way, are probably not that far off in size relative to the range from which we use them), we want those corners for subconscious assurance of our own safety.

Now, the other things are less for biological and more for practical reasons. It's just easier to carve a plot of land, or a long beam of wood, into rectangles; and given a rectangular plot of land to live on, the homeowner is apt to try and first build the simplest structure to occupy it (four walls and a roof), and later to occupy the land most efficiently with shelter (a rectangle in a rectangular plot), leaving equal distances to plotted out from house wall to plot boundary. As with the screens, if you live in an oval, you'd feel subtly cheated out of the additional space in the corners -- even of the oval was made by the expansion of your previous rectangle. And once you've got a rectangular house, rectangular furniture more efficiently fills up that space.

But be at peace with the circle as well; the largest man-made rectangle, a thing called Colorado, is still not much more than a thumbprint on that circular thing on which we live.

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Addendum: moosemanmoo has raised to my awareness the principle that Rectangles with rounded corners are everywhere as well!