The Earth is becoming invisible
The move to digital entertainment, often downloaded for personal consumption, and the fact that we are broadcasting less across the airwaves is having an unexpected consequence. The founder, some fifty years ago, of the Search for Extraterrestrial Intelligence (SETI), Dr. Frank Drake, states that the level of radio transmissions from our planet is making it almost invisible to others who are searching for intelligent life in our galaxy. He states that the earth used to be surrounded by ‘a shell of radiation, some 50 light years wide, made up of our radio and television transmissions from the last half century. With more and more transmissions arriving to us by cable and the web, and with satellites pointing their beams directly at the surface of the planet, very little radiation is escaping in to the cosmos.
Digital signals are weaker than their older analogue counterparts, and it was suggested that the transmission has fallen from about one million watts to about two watts (little more than that from a mobile phone). Meanwhile, all the episodes of Coronation Street are moving at the speed of light towards other civilisations. I hope they are suitably impressed. We have always hoped that any advanced civilisations out there will be benign and ready to share the wealth of their knowledge with us. If it proves not to be the case, we may be grateful that our move to digital is making us invisible.