One of the things we love at Worldchanging is making the invisible visible. The same is true for the people at the Doors of Perception conference. (In fact, the overlap between their interests and ours is basically 100%.) My second-favorite talk from Monday was Usman Haque and his “Sky Ear”, a floating array of sensor-filled balloons which light up to display the electromagnetic fields we’re constantly swimming in. Including flashing to indicate when you call it on your cellphone (whereupon you can hear as well as see the local EM fields.)