I've thought along these lines before, and am writing a hard science fiction novel with this premise. I love thinking about the possibility of other advanced c

I've thought along these lines before, and am writing a hard science fiction novel with this premise. I love thinking about the possibility of other advanced civilizations etc as much as the next guy, but it does seem like the _other_ possibility is less represented in sci-fi and maybe in current thought in general. It's so fun to think about life existing and those implications, less time is given to thinking about life _not_ existing elsewhere and what that would mean. I get that to a degree. I feel like Debbie Downer just saying it, but in order of likelihood based on current observation, I would arrange the scenarios like this: * Intelligent life only exists on Earth. This is what we have observed so far, so in absence of other evidence this is "most likely" with a large margin of error ;) * Intelligent life does exist and is abundant, but we are among the most advanced. Hard limits in physics mean it is impractical to travel out of one's solar system, much less galaxy. * We're among the most advanced because of a "great filter" after our current stage. * We're among the most advanced because of a "great filter" before our current stage. * We are a simulation