Alien life should be everywhere. The sheer abundance of stars in the universe (the number far outstrips the total number of grains of sand on every beach on Earth) suggests that, somewhere, an intelligent lifeform should be warming itself on a distant planet. Even if life evolves rarely, ET should be phoning.
Yet, by all appearances, humanity seems to be flying solo in our galaxy, and perhaps the universe. Many solutions have been proposed to solve this riddle, known as the Fermi Paradox. The aliens are hiding. They’ve entered suspended animation until more propitious conditions arise. A Great Filter makes the leap from “life “to “intelligent life” improbable, if not impossible. They’ve blown themselves up.
Researchers of Oxford University’s Future of Humanity Institute have another answer. It’s likely intelligent life doesn’t exist at all, outside of Earth.