The trackball (ancestor of the mouse)

Ralph Benjamin was sent out of Germany at fourteen to escape Nazi persecution and reached England as a refugee in 1939; his parents were murdered in the Holocaust. Working on a radar plotting system for the Royal Navy in 1946, he set a ball in a socket so that rolling it moved a cursor across the screen — the roller ball, patented in 1947. It is the trackball, and the direct ancestor of the mouse Douglas Engelbart would build some twenty years later. The Navy classified it and fitted a joystick instead, so the first pointing device sat on a shelf and its inventor got no credit at all.

Part of “The Gifts of the Jews” — verified Jewish contributions to the world, with sources.