Thanks for this Michael. What seems a fascinating possibility to me and far more likely, is that radio and microwave communications from elsewhere in our galaxy have streamed past this planet somewhere in the past. Perhaps some alien version of "Days of Our Lives" was crackling past earth whilst T Rex were wandering about. Or maybe even the last communications of collapsing technological civilisations - news reports about oil shortages and climate catastrophe - were streaming past while Roman legions clashed with Francs and Germanic tribes. What I wonder is if there would be any way to tell. Could such organised signals leave any enduring trace?