Nearly a half-century has passed since the majestic moment when Neil Armstrong stepped carefully onto the lunar landscape, left foot first, taking that giant leap for mankind.

Whether you were alive then and glued to the TV, or relived it later through that iconic, grainy NASA footage, what you probably remember is just that: The majesty.

You’re probably not thinking much about the deafening noise, the claustrophobia, the terror of blasting off in a rickety sardine can that could fail at any moment for any of a thousand reasons. Or the fact that Armstrong and Buzz Aldrin could have ended up stranded, left to die on the moon; President Richard Nixon had a speech ready for that dark scenario.

You will, though, be thinking of these things as you watch “First Man,” the latest installment in director Damien Chazelle’s meteoric career — and sorry for the space pun, but it’s entirely apt. An intimate character study that somehow becomes grand just when it needs to, “First Man,” based on the book by James R. Hansen, is a worthy successor not only to Chazelle’s “Whiplash” and “La La Land,” but to the astronaut films that precede it, like “Apollo 13” and especially “The Right Stuff.”

It’s also, amazingly, the first feature film about Armstrong. Chazelle’s partner here is Ryan Gosling, who dials down his obvious star wattage to give an internalized, fully committed performance as the “reluctant hero,” as Armstrong’s own family described him.

Gosling’s task here is not merely to give dimension to a mythical American hero. He also has to play a man who famously kept his emotions in check. That may not be an asset for a movie character, but sure was an asset for the first human to set foot on another world.

And that’s because this stuff was, well, terrifying! We begin in 1961, during Armstrong’s test pilot days. Taking a hypersonic X-15 up for a spin, he’s suddenly in trouble; he can’t get back down. “Neil, you’re bouncing off the atmosphere,” comes the rather concerned voice from below.

He makes it back, though, barely breaking a sweat. As for us, we’re irretrievably rattled.

From the heavens we go to a small home office, where Armstrong is on the phone, trying to find help for his toddler daughter, ill with cancer. His grief over her fate will remain a theme of the film until the end. But it remains unspoken, even to his stoic wife, Janet, played here with subtlety and grit by the wonderful Claire Foy.

Seeking a fresh start, Armstrong becomes an astronaut in NASA’s Gemini program. On Gemini 8, he successfully docks his spacecraft with another before suffering a harrowing in-flight emergency.

The split-second that separates giddy success from terrifying failure, the tiny, claustrophobic spaces, the flimsy materials, the shaking, the roaring, the positively ancient-looking technology — Chazelle illustrates all of this, indelibly. And we’re forced to wonder: How did they ever make it into space even once?

On the ground, meanwhile, we see what it’s like to be a loved one. During Gemini, Janet explodes at Armstrong’s boss, Deke Slayton (an excellent Kyle Chandler): “You’re a bunch of boys making models out of balsa wood! You don’t have ANYTHING under control.”

Then there’s the devastating launchpad testing disaster that killed Armstrong’s fellow astronauts, Gus Grissom, Roger Chaffee and Ed White. Hearing the news on the phone, Armstrong clutches a wine glass so tightly, he breaks it and gashes his hand.

But if he has qualms about going forward, he doesn’t show it. “Your dad’s going to the moon,” Janet tells their boys. Does that mean he’ll miss the swim meet, one of them asks? Foy’s eyes flare with anger as Janet insists — indeed, commands — that Neil sit down and tell the kids he may never come home.

She’s right: One of the more chilling scenes is a brief look at NASA bosses reviewing the speech Nixon will give if the men can’t get off the moon, and what he’ll say to the “soon-to-be widows.”

And then, the mission. That famous walk to the launchpad, the astronauts waving, the applause. You hold your breath imagining how Chazelle will pull off the landing itself. With a granite quarry in Georgia standing in for the moonscape, it’s as grand and beautiful as you’d want. And yet it’s not a mere recreation of what we’ve seen before.

There’s been a distracting controversy over whether Chazelle “ignores” the precise moment when astronauts planted a flag. It’s silly for many reasons, but especially because this isn’t a movie about symbols, or myths.

It’s about men — especially one man. After the grandeur of the moon landing, an event that still boggles the mind, the movie ends on a note of extreme quiet: just two people staring at each other.

It’s a bold choice, but it feels right. Sometimes a movie feels biggest when it goes small. And this one feels big. Chazelle is only 33. One can only imagine how far he’ll travel.

“FIRST MAN”

*** 1/2

(PG-13, 2:21)

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