It's been said by others HNers, but I want to stress the point further with a reformulation.
We have great difficulties to find foreign planets. We barely know what's beyond Pluto. Heck, we probably have a couple of surprises waiting for us in the solar system.
One cannot expect us to be able to detect alien probes, operating with engines and communication capabilities beyond our understanding, probably only few meters wide (if not much smaller!) and operating somewhere near our star, probes we don't even attempt to detect in the first place.
Plus there is a bias toward colonization. I agree that an advanced civilization, except if it becomes extremely xenophobic, would probably want to explore the universe, but colonize? If you have the technology, it's possible you don't need to spread physically that much.
We have great difficulties to find foreign planets. We barely know what's beyond Pluto. Heck, we probably have a couple of surprises waiting for us in the solar system.
One cannot expect us to be able to detect alien probes, operating with engines and communication capabilities beyond our understanding, probably only few meters wide (if not much smaller!) and operating somewhere near our star, probes we don't even attempt to detect in the first place.
Plus there is a bias toward colonization. I agree that an advanced civilization, except if it becomes extremely xenophobic, would probably want to explore the universe, but colonize? If you have the technology, it's possible you don't need to spread physically that much.
Just speculations of my own, of course.