If I had to pick the critical technology for the 20th century, the bit of social lubricant without which the wheels would've come off the whole enterprise, I'd say it was the sitcom. Starting with the Second World War a whole series of things happened--rising GDP per capita, rising educational attainment, rising life expectancy and, critically, a rising number of people who were working five-day work weeks. For the first time, society forced onto an enormous number of its citizens the requirement to manage something they had never had to manage before--free time.

And what did we do with that free time? Well, mostly we spent it watching TV.