Life on Earth arose about as soon as it was possible for life to arise

[lumberjack_jeff]

66. Even if the galaxy hosts 2 or 3 of them at a time why have they not spread?

Over a billion years, some of those civilizations would have spread. Let's say that every 50,000 years a new technologically advanced species happens somewhere in the galaxy. I would think that at least one of those 20,000 civilizations would have sent probes and spread throughout the galaxy.

Within the next 100 years, we will have sent robotic probes to every planet in our solar system. Within the following 100 years those robots will leave unmistakable evidence of their presence throughout this system. In the next 1000 years autonomous probes will have arrived at the nearest stars.

Someone downthread claimed that this view is "comforting". Hogsnot. Knowing that you are the universe's mechanism for spreading the experiment of life is anything but comforting. What's comforting is belief (in the complete absence of any evidence to support it) that the landlord will take care of the damage we leave to our house and that there's nothing novel or unique about this place despite the fact that there are no other houses to be seen - anywhere.

"Surely", as in "surely we can't be the only planet with intelligent life on it" has an odd meaning. It generally is used to mean "this is a wild conjectural leap that I'm heavily invested in".