Rear Admiral Grace Hopper, a pioneer in computer science, shows David Letterman how she illustrates nanoseconds in this highly enjoyable interview.
From her Wikipedia page:
Grace Hopper is famous for her nanoseconds visual aid. People (such as generals and admirals) used to ask her why satellite communication took so long. She started handing out pieces of wire which were just under one foot long, which is the distance that light travels in one nanosecond. [...] At many of her talks and visits, she handed out “nanoseconds” to everyone in the audience, contrasting them with a coil of wire nearly a thousand feet long, representing a microsecond. Later [...] she passed out packets of pepper which she called picoseconds.
This must be vintage Letterman. Doing the math with age and dates and looking at Dave’s hair (color and lack of receding) I would say 20 years ago. Vintage, classic Letterman, there is none better.
I meant to put the date in there. In the interview she says she’s just retired and Wikipedia dates that as 1986, 26 years ago. You were close!