When Grace Hopper wanted to explain a nanosecond to admirals who kept asking why satellites were slow, she handed each of them a piece of wire 11.8 inches long, the exact distance light travels in a billionth of a second, and told them to keep it in their pocket as a reminder that physics, not laziness, sets the limit. (opens in new tab)

Grace Hopper kept a bundle of wires, each one cut to exactly 11.8 inches. She handed them out at lectures, in Navy briefings, and to anyone who asked why the new satellite links felt sluggish. The wire, she explained, was a nanosecond. That was how far light could travel in one billionth of a second, […]