Why we did not make contact with extraterrestrials: answers to the Fermi paradox

In the summer of 1950, physicist Enrico Fermi asked his colleagues a simple question during lunch: "Where is everyone?"

Fermi was referring to extraterrestrial life in the universe.

It can be argued, he said, that over the 4.4 billion years necessary for intelligent life to evolve on our planet, the rest of our galaxy should have been invaded by extraterrestrials as smart and technologically advanced. But despite decades of searching for traces of extraterrestrials in the Milky Way, we have not found anything, nor anyone.

This enigma is known as the Fermi Paradox.

Scientists have proposed a myriad of potential answers to the question, especially that aliens hibernate or deliberately hide from us. Some researchers have also suggested that very advanced technological civilizations will destroy themselves before having the opportunity to come into contact with other intelligent lives in the universe.

Read more: Extraterrestrial civilizations may have already explored the galaxy and visited Earth, according to a new study. We have not seen them recently.

In his new book, "End Times," author Bryan Walsh discusses 13 theories about why we have not yet made contact with extraterrestrials and why we could never do it. This is how everyone approaches the Fermi paradox.