The weirdest thing about Ad Astra may be its title, a trimmed Latin phrase that hints at the movie’s interplanetary scope while also hiding a deeper meaning. That’s because the title, which was originally just a placeholder, is part of a longer song lyric that inspired Ethan Gross (Fringe) when he was writing Ad Astra with director James Gray.

In an interview, Gross tells Inverse that he first heard the words “ad astra” a decade earlier while listening to a song by the progressive rock band The Dear Hunter. (No, not that Deerhunter, but they’re connected too.)

The song, “What It Means to Be Alone,” includes one lyric that Gross was particularly drawn to: “‘Ab ovo,’ the angel sings, ‘Ad astra.’” Literally, this translates to, “The angel sings, ‘From the egg to the stars.” But a more accurate translation of that second line might be, “From the beginning to the end.”

While researching this phrase, Gross stumbled upon a more classic Latin phrase: “ad astra per aspera.” It means “to the stars through hardship.”

“I wrote ‘Ad Astra’ as a temporary placeholder name on the file, but we always liked it,” Gross says. “It has a little bit of mysteriousness to it. The unspoken part of the name, the ‘per aspera’, is really what a lot of the movie is about.”

"The unspoken part of the name, the ‘per aspera’, is really what a lot of the movie is about. — ‘Ad Astra’ screenwriter Ethan Gross

In Ad Astra, Brad Pitt plays Roy McBride, an emotionally distant astronaut who’s tasked with traveling far out into the solar system to find his own father and stop an anti-matter power source that threatens to destroy all of human life. That’s a heavy premise, even without the psychological trauma and baggage that Roy deals with on an epic journey further into space than almost anyone else in human history.

Yeah, the “hardship” part makes a lot of sense.

Gross never thought the studio would run with a Latin name for a deep space sci-fi movie, but they did. Then, one day he came across a song called “Ad Astra” by the similarly named (and better known) band Deerhunter and it solidified the idea.

“To me it was almost a sign that it had to be the name of the movie,” he says.

For even more insights into Gross’ experience writing the movie, like alternate versions of the ending he and Gray considered and what inspired the story, here’s our full interview with some light edits for clarity and brevity.

Inverse: Totally original sci-fi feels like a rarity in 2019. What are the origins of this really unique story?

Ethan Gross: James [Gray] and I are friends. We graduated from USC together years ago. After we graduated, we worked together on a project that almost got made but didn’t. A couple decades went by, and then we wanted to work together on something in science fiction.

‘What would you do with science fiction?’ we thought. Like many people in the world, we love 2001: A Space Odyssey. You can’t top that, but we thought we could make a sci-fi story more personal by examining the inner self. Even though it’s an epic, deep space journey, the further out Roy goes into space, the more the story focuses on his inward journey.

For James, it really came together when we were thinking about an astronaut character that would give up years and years of his life to go very long distances, which nobody has done yet in real life. Many people would go to Mars and spend years away or live there for the rest of their lives. In many ways, that’s heroic, a great character strength — but that strength could also be hiding a flaw, something you’re trying to escape from that you haven’t even noticed was there yet.

Roy isn’t aware of how much his father’s absence has influenced him, and we see that conflict play out in Ad Astra. When we realized that this character also had to be Roy’s father, that was the last piece that really clicked.

What made you develop the idea of this the anti-matter power source as what threatens mankind?

James and I talked about the development of the Atom Bomb. There was some fear, most of it unfounded, that the splitting of the atom would result in a chain reaction that could incinerate the atmosphere above America. We thought, ‘What if there was a bigger sci-fi version of this fear going on in space?’

Our love of some movies and stories also helped develop the plot as you can see. Heart of Darkness, Apocalypse Now, and of course 2001: A Space Odyssey. There’s also a lot of documentaries like For All Mankind about the Apollo program that inspired us. And the general idea of mythic stories like Joseph Campbell talks about [in The Hero with a Thousand Faces].

Director James Gray with star Brad Pitt on the set of 'Ad Astra'. Walt Disney Motion Pictures

I know the production worked with scientific advisors to capture a scope of technology that feels ripped out of our very near future. How important was that to Ad Astra?

We did a lot of research into as much science as we could. We wanted the science to be as accurate and plausible as it could, but we didn’t want that to drive the story. We wanted to story to be epic and mythic and have the science support that.

Was there ever a draft where there was less realistic sci-fi or supernatural elements? Or was it always hyper-realistic?

We considered some deeper science fiction elements in the very beginning, things to do with alien intelligence, faster-than-light technology. But other movies have done that so well, like Interstellar. With aliens, you can’t really beat 2001: A Space Odyssey. That’s my favorite movie of all time, so it’s hard to even attempt doing anything close to that. So we focused more on the personal hardship of Roy’s journey.

We also thought we might have aspects of artificial intelligence at some points. There were a lot of ideas tossed around, but the stuff about the father and how big of an absence a father can be became the predominant, driving force. My dad died when I was around 20. The absence and pain is always there, but you don’t always know it’s there. Sometimes you have to go far away from the Earth, metaphorically, before you can feel that.

The reality of the movie is almost an alternate future where the Apollo program and exploration of the moon would have continued. In the real world, funding and interest died out, but in Ad Astra it never did. The moon and Mars are built up with science, military, consumerism, and gaudiness — and all the problems that come with those things. James probably doesn’t know that I think that, but it strikes me as a cool mix of the past and future.

We resisted naming a year and just called it “near future” for that reason.

Roy's father, Clifford McBride, in 'Ad Astra'. Walt Disney Motion Pictures

The ending of Ad Astra is pretty bleak. Both McBrides are further away from Earth than anyone else in human history, all in the hope of discovering signs of alien life … and there’s nothing. Was this always the ending you planned for?

We talked about a lot of possibilities. Maybe he discovers aliens and they’re too far away. Clifford might build such a powerful technology to reach the aliens, and this technology is so dangerous that it threatens the solar system. He’s the only one willing to take that risk because he wants to see what that life is like. We never went very far with that, because that quickly felt too big.

James wanted a personal, emotional catharsis in the end, so we felt that our ending stayed true to that.

Ad Astra is now in theaters.