I'm glad I came across your series on this topic — I really enjoy your writing style, and it’s a pleasure to read. I also appreciated that you mentioned many different theories about alien life, in contrast to other sources that only list the most basic or popular ones. I really appreciate all the effort you put into it!

I completely agree with you regarding the "Rare Earth Hypothesis" and the "Early Bird Theory"; they both seem very logical to me as well. When I thought about this topic before, I just assumed that alien life couldn't exist because of the extremely small chance of evolution from microorganisms to intelligent beings capable of space exploration. And even in the case of other planets that are similar to Earth in terms of habitability, it would take millions of years for life to reach any form of intelligence. Considering the time it took human civilization to gain the ability to analyze space and send or receive intergalactic signals, we may never encounter alien species (if they exist) within thousands of generations.

The "Self-Destruction Theory" seems very plausible to me too, even though it’s a sad thought. Scientific progress has happened "in an instant" compared to the time we exist. We are trying to find life in space, but to be fair, I can’t say with certainty that the human race will exist for the next thousand years. Considering the numerous problems we face - environmental issues, world wars, pandemics, resource depletion, and others - I’m not sure that aliens would even be able to reach Earth in time after receiving our signals (if they do exist). However, this also creates some space for the "Technological Singularity Theory" - given how much VR technologies have advanced in recent years, it seems like a logical continuation for the human race if we are unable to save Earth or colonize other planets.

There is one theory I believe in the most: it’s similar to the "Limited Observability Hypothesis" you mentioned. I didn’t find the exact name, but as far as I am aware, it’s called the "Alternative Biochemistry Hypothesis"/"Shadow Biosphere Hypothesis"/"Not Life As We Know It Theory." In simple terms, it suggests that alien life is too different from the life we understand. The aliens could be some 4-dimensional beings, and the human mind can't possibly comprehend what they even look like.

One argument for this theory that convinces me is the fact that string theory (one of the modern theories for describing fundamental nature of our universe) requires more than three dimensions to be valid (in different variations, it requires 10, 11, and in some cases, even 26 dimensions!). To a 4-dimensional being, our world might be just too simple. We don’t consider ants to be intelligent beings; aliens might think of us in the same way. Even though string theory describes dimensions in a different way compared to the spatial dimensions we percieve, there may exist more than 3 dimensions, and we have no way of checking it.

At the same time, I can relate to your feelings regarding the "Dark Forest Theory." I am a fan of science fiction too, and the possibility of the human race being completely alone in the galaxy is extremely depressing. I want to believe that there are other beings, and that at some point, we will be able to interact with them. Theories like the "Dark Forest Theory" and the "Zoo Theory" always fascinate me. It’s a scary, yet exciting thought.