Comment by mike_hock

1.) It's definitely a giant leap from current technology to interstellar colonization.

2.) Other civilizations even in the nearest solar system would basically be impossible to detect. Even in our own solar system, there could be millions of undetected spacecraft right now. They're simply too small to see. To be detectable, they'd either have to be massive and massively disruptive, like Dyson spheres, which are and most likely will forever remain pure fiction, or they'd have to happen to use radio for communication.

3.) There are good reasons for them not to be using radio for communication. They might have discovered a different physical phenomenon that allows them to communicate in ways we can't detect. Or they might not be as reckless as humans and don't want to broadcast their presence and activity to completely unknown and potentially hostile other species.