In summer 1950, physicist Enrico Fermi asked his colleagues at lunch a simple question: "Where are all?"
Fermi referred to alien life in the universe.
Probably during the 4.4 billion years that intelligent life developed on our planet, the rest of our galaxy would have been overrun by similarly intelligent, technologically advanced aliens. But despite decades of searching the Milky Way for signs of aliens, we have found nothing or nobody.
This puzzle has become known as the Fermi paradox.
Scientists have offered countless potential answers to the question, including that aliens hibernate or consider hiding from us. Some researchers have also suggested that sophisticated technological civilizations destroy themselves before they have the opportunity to connect with other intelligent lives in the universe.
Read More: Foreign civilizations may have already explored the galaxy and visited the Earth, according to a new study. We only recently saw her.
In his new book End Times, author Bryan Walsh discusses 1