In a 19-minute YouTube video, Fran Blanche explains how those big screens at Mission Control worked during the Apollo era. Stop and think about it: they were displaying information in ways that computers wouldn’t be able to do for decades. The displays were produced mechanically, by multiple projectors using glass slides to project images on the screen. The projectors could move spaceship icons across the screen like a graphical sprite, or use plotters to scratch a flight path across a slide to represent a flight path, using telemetry data processed in real time by mainframe computers. [Boing Boing]