The 16:9 rectangle that frames nearly every screen you own did not win by being anyone's favourite. It won by being the shape almost nobody hated. The story belongs to Kerns Powers, an engineer at the Society of Motion Picture and Television Engineers, who set out to find a single aspect ratio that could stand in for the whole messy family of formats already in use.

The range he was working across was wide. At one end sat the old 4:3 television, nearly square by modern eyes. At the other stretched the extreme widths of CinemaScope film, panoramas built for the cinema. No single rectangle could match any of them exactly, so Powers went looking for a compromise instead of a winner. When he laid the competing ratios over one another and measured, the shape that balanced the pain landed at roughly 1.78 to 1, which is 16:9.

What makes the choice elegant is how evenly it spreads the disappointment. Show wide film on a 16:9 screen and you lose some picture to letterbox bars. Show a narrow old broadcast and you lose a similar fraction the other way. The ratio was engineered so that no format was badly served and none was perfectly served either, a rectangle that gave everyone the same modest ache. That is precisely why it swept the world. It was not the ratio filmmakers dreamed in or broadcasters had grown up with; it was the one everybody could live with. Sometimes a standard triumphs not because it is best, but because it is the shape at which all the arguments cancel out.