Fish don't know they're living in water, nor do they stop to wonder where the water came from. Humans? Not much better, as we share a world engulfed by television. And the deeper our immersion becomes, the less likely it seems we'll poke our heads above the surface and see there must have been life before someone invented TV. That invisible someone was Philo T. Farnsworth, who was fated to live and work, then die, in sad obscurity. Now, on the centennial of his birth on Aug. 19, 1906, his invention plays an increasingly powerful role in our lives --...