But Ad Astra is not really about aliens in the same way as other sci-fi narratives that focus the search for extraterrestrial life. In its climactic, profound moments, when Pitt's astronaut Roy McBride finds his father Clifford (Tommy Lee Jones), alone and manic after decades aboard a spaceship stuck in the far reaches of our solar system, the two discover something more important than first contact with aliens. Clifford is racked by guilt (for murdering his crewmates when they tried to return home) and shame (at being unable, all these years to find even a hint of any little green men out there amongst the stars). He keeps repeating to Roy, breathlessly, that he failed, he found nothing.
"But you did," Roy says finally, in a blink-and-you-miss-it exchange as they're leaving the space station. "We're all we've got."
What if there isn't any life in the universe but us? What if sentience begins and ends with humanity? Statistically, that sounds impossible. We've recently discovered a few nearby planets that might have water and an atmosphere suitable for Earth-like life, and there seems to be far more water in our own Solar System than we previously thought. The universe is an unthinkably enormous place -- surely, surely there must be others out there. How unfair, the thinking goes, would it be to find out that all this time we were shouting into nothing?
The ending to Ad Astra posits that we've been looking in the wrong direction. Maybe it's inherently irresponsible for us to search the stars for something to save us or to give us meaning, ignoring what's actually happening to humanity in the meantime. That's terrifying, and much less fun to imagine than Vulcans giving us space travel technology or the CIA housing aliens in soon-to-be-stormed Area 51, but it's also a wake-up call. If we're truly alone, that means human life is more precious than we could imagine; that Earth, in its perfectly habitable orbit around the sun, is the most special planet in the universe, and that there won't be anyone or anything left to pick up the pieces if we destroy ourselves. In Ad Astra, our last hope -- to end the wars and suffering and contamination of our planet -- is our only hope. To think any less would be the universe's biggest mistake.