Radio feels a little antiquated these days, but I've always held it as one of the keystone technologies of our world. The ability to communicate over great distance without a physical medium that could be intercepted represented a new frontier in how we interact with each other. Without the prohibitive costs of printing, the complications of couriers, or the slowdowns of shipping, information that was important could be communicated almost in real time. It's also when our skies stopped being so silent. While we don't hear it with our ears, our modern sky is abuzz with radio and cell signals, ricocheting around the atmosphere. At any given moment, there are wavy bands of human communication zipping overhead, filling the air with a faint electromagnetic pressure. We've come a long way with wireless communication, but ever since that day, we've been bathed in a radio sky.