Incandescent light bulb development (Edison/Langmuir)

Used to introduce the Langmuir as a unit of contamination time. Edison's carbonized horsehair filaments → tungsten in argon → factor-of-100 longer life from suppressing evaporation.

There's a guy, Irving Langmuir, who won the Nobel Prize working for General Electric. Edison had invented the incandescent light bulb, but they didn't last very long — less than 10 hours, which was getting kind of pricey. Anybody know what material Edison used before tungsten? Carbonized horsehair. He'd carbonize the hair, end up with a graphite filament. The carbonized horsehair might last an hour before it would vaporize. They learned tungsten would last longer.

Brief reference. Edison's horsehair filament was superseded by tungsten; GE spent a hundred years perfecting tungsten light bulbs only to have LEDs come along. Used to make the point that engineering investments can be obsoleted by technology transitions.

We're going to talk about design later, but engineering does design. We talked about creating, making something new or different. There's a creative aspect of engineering. Remember the stinky quote at the beginning — if it works but no one knows why, it's engineering. You create it, but you don't — like Edison didn't know why horsehair worked so well. He later found out tungsten was better, and then General Electric spent billions of dollars over the next hundred years perfecting tungsten light bulbs, only to have LEDs come along.