Given the burgeoning evidence that there must be billions of Earth-like planets in our galaxy - let alone the observable universe! - why the heck have we never picked up any signals from other intelligent life? Enter the Fermi paradox.

So, are we utterly alone in the universe (or perhaps quite the opposite)? We don't yet have an answer to the question, and considering the matter inevitably involves some speculation and forays into the realm of science fiction. Nevertheless there are many possible resolutions to the Fermi paradox (as discussed in the linked article), and contemplating them turns out to be a deeply humbling and mind-bending experience.