My favorite solution is very simple: We're overestimating our ability to detect extraterrestrial live. It might be common and look similar to us. They might eve

My favorite solution is very simple: We're overestimating our ability to detect extraterrestrial live. It might be common and look similar to us. They might even use radio signals. But until somebody demonstrates that you can detect stray telecommunications signals over lightyears I find it hard to believe. I also think it is going to be hard to detect the chemical signature of life e.g. via spectroscopy, if you can't even image the planet next to it's overshining star. Second, and somewhat sobering part: I also think it is practically impossible to do interstellar journeys. You can imagine scaling up existing tech to do so. But I think at some point the complexity and cost (in terms of resources, not money) would diverge. As an analogy, you can build a small robot, but if you try to scale it up to a mech it will not work in reality. Too heavy to move, yet to flimsy to stand.