The universe is either totally empty, or it is full of life and good planets are a scarce resource, and worth fighting for. It is illogical to assume that we are somehow in state between those two extremes. In either case it does not make sense to advertise our presence and position in any way. It is quite probable indeed that the invading force has already on the way, as first  radio transmitters started 100 years ago. Ships from 100 light years away will arrive in 100 years, assuming light speed capability.,(reply>), In 1988 Teuvo Kohonen explained us how neural nets work and predicted the future where neural nets are separate boxes with pre-learned skills you can buy from shops. I am still waiting for those bloody boxes ," so not much impressed with the current state of the computer science.  <a href=""https://www.youtube.com/watch?v=Qy3h7kT3P5I&amp;t=2478s"">https://www.youtube.com/watch?v=Qy3h7kT3P5I&amp;t=2478s</a>",(reply>), Indeed I did. I am pretty sure my new neighbor is  a sophon. Does not understand rules of recycling bins for example.