“Often what the world calls nonsensical, becomes practical,” Alexander Graham Bell observed in reflecting on his early work that would eventually produce the telephone. Yet how nonsensical the notion of a wireless phone must have seemed even to him at the dawn of the 20th century. But a mere seven decades later, in April of 1973, the first cellular phone made its debut. To celebrate the fortieth anniversary of the era-defining technology, filmmaker David Friedman has profiled inventor Martin “Marty” Cooper (b. 1928) in the latest installment of his wonderful series of portraits of inventors.

What’s important about any technology is that the technology is — hopefully — invisible, but at least transparent and maybe intuitive. … The purpose of technology is to make your life better. Most cell phones don’t do that very well — in fact, they force us to become engineers, to learn a bunch of new things. We shouldn’t have to do that. The ideal phone would be one where I would just talk to the phone — or maybe the phone would read my mind — and it would do things to make my life better. … If you try to build a device that does all things for all people, it won’t do any of them very well. So I think that’s where we are with cell phones today.