WHY HAVEN'T WE FOUND ALIEN CIVILIZATIONS?

"Where are they? They should be here, but we don't see them anywhere."

It is said that around 1950, Enrico Fermi, the discoverer of nuclear fission and laureate of the Nobel Prize for Physics in 1938, sitting at a table with his colleagues and watching some alien cartoons, would have asked: "Where are they? They should be here but we don't see them anywhere". He would have had two things in mind:

1) The galaxy is very old a…