An interesting concept that occupies the minds of many philosophers and scientists alike is the idea of life outside of Earth (and outside of our solar system). Italian-American physicist Enrico Fermi posited that there exists a paradox describing the possibility of life outside of our world: there is no physical evidence to prove (or even suggest) that life exists outside Earth, yet all mathematical calculations suggest that this life must exist somewhere. In other words, aliens have to exist, yet we haven’t seen them (or any evidence of them).
In a manner sort of similar to some science fiction novels, Fermi argued that any population in the universe which had access to specific technologies would be able to easily gain control of large portions of the galaxy (and maybe even beyond). For example, if a population had perfected advanced rocket technology, they could easily and rapidly colonize large groups of planets. Does this mean that we humans are the most advanced population in the galaxy/universe? Does this mean that we are the only population in the galaxy/universe? Or does this mean something else? The beauty of this paradox is that it has yet to be solved–and will remain unsolved until we have physical evidence of life outside of our planet.