Enrico Fermi formulated in the early 1940s that the extraterrestrial civilizations of the past would spread exponentially in the Universe.
This means that the Universe would most likely be full of inhabited planets.
This has been a headache for the scientific community.
Indeed, it totally contradicts the theoretical paradigm of chemical evolution followed by neo-Darwinism because, according to Fermi, the Earth would have been terraformed rather than a planet where natural evolution would have been taking place.
But Fermi's concept is so powerful that the scientific community is trying to find ways around it by calling it a paradox.
Therefore, the paradigm shift that will admit Fermi's concept as the one that has imposed itself in the Universe will be very difficult to make...