This is a talk that I gave to an organization of STEM (Science, Technology, Engineering, and Math) teachers in mid 2012. My message was simple: The job of teachers is saving the world. Literally. The world is full of complicated things run by trained, skilled people who don't live forever. Each and every one of these people need to be replaced over time, and if they aren't, the whole place falls apart. Teachers are the only line of defense we have against this outcome.
Here's the video: