Speaking of pet theories, here is mine: There exists a sentry system of interstellar buoys that get sucked into star systems passing by. Perhaps with a solar sa

Speaking of pet theories, here is mine: There exists a sentry system of interstellar buoys that get sucked into star systems passing by. Perhaps with a solar sail, so they can control a bit which stars they want to take a closer look at. Our solar system become "recently" a candidate for obvious reasons. The probe made its analysis and plotted a fast escape, sending a tight laser beam to the next closest relay station. A fleet of planet biosphere erasing machine intelligence dispatch is on its way. Probably some ancient left over from AIGs engaged in eternal warfare. Hence a dead silent galaxy, a rather dark forest.