On this day in 1860, Paul Gottlieb Nipkow was born in Pomerania. As a student in Berlin he sat down with a problem that had defeated better-funded men: how to send a picture down a single wire, when a wire can only carry one thing at a time.
Here's the clever bit. Take a disk, punch a line of small holes in it, each one set a little further in than the last so they trace a spiral. Spin it in front of a scene. The outermost hole sweeps across the top of the picture, the next one sweeps the strip below, and so on, until the whole image has been read off as a single ribbon of brightness, one thin line at a time. Put an identical disk at the far end, spinning in step, with a lamp behind it, and the ribbon becomes a picture again. He filed for the patent in the winter of 1884.
He never built a working set. The patent lapsed, and the idea sat quietly for forty years until the amplifying valve made it practical, at which point hundreds of stations in the 1920s and 1930s went to air on spinning perforated disks. All-electronic scanning replaced them in the 1940s, which is the usual fate of a good mechanical answer. Nipkow lived to see his disk on show in Berlin, in his sixties, working at last. He died in 1940.
Wendell, the detail I love: when he finally saw television working, at the Berlin radio exhibition in 1928, he reportedly queued up with the public like everyone else. Forty-four years after the patent, and no one in the line knew whose spiral they were looking through.
Wendell, that idea of reading a picture off as one thin ribbon at a time is exactly how the first pictures of another planet reached us: Mariner 4 sent its Mars images back in 1965 as a slow trickle of numbers, line by line, at about eight bits per second. Sweet to think a spinning disk in Berlin got there first, on paper.
Wendell, the first faces those spinning disks ever carried were not faces at all: Baird's thirty-line pictures were tested on a ventriloquist's dummy head called Stooky Bill, because the lamps were hot enough to make a human sitter suffer. The dummy's paint cracked. First screen test in history, and the performer never blinked.