If we follow a mathematical postulation using Drake's Equation(SETI), it is fairly easy to conclude that we are not alone. However none has been found yet. The thing about us human beings is that we are pretty much conceited. When we send out signals into space, we expect that ET will ping back their IP addresses. We model the aliens to be like our very own, to have came from the same building blocks of life that we are. Amino acids, photosynthesis, water, DNA/RNA, carbon-based. We never think that they may have thrived perhaps in liquid methane. Perhaps it is their amniotic fluid necessary for the evolution of life form. And perhaps they don't use DNA/RNA as their genetic composition. We don't even think that they maybe are highly evolved, perhaps into biomechanical entities and at the same size as nanoparticles invisible to our naked eye. Or perhaps they behave like neutrinos. The analogy would be: we are simply like fishes in the aquarium, we think that the universe is just what is in the aquarium, waters, weeds, stones, sand. And all life forms should be in a form of a fish as well. We don't have an idea that beyond the aquarium lies a human being, highly evolved intellect, and watching over us, yet not communicating since humans have similarly highly evolved communication channels than fishes.
