Pay attention. Life has a way of reminding us about things that are really important.

Two weeks ago, my wife and I treated ourselves to a cinema night and saw the astonishingly good film “Oppenheimer.” It’s a three-hour biopic about J. Robert Oppenheimer, legendary “Father of the Atomic Bomb,” the young scientific genius who directed the WWII Manhattan Project in developing the world’s first nuclear weapon.

It’s a terrific movie, historically accurate and thought-provoking. The film’s recurring theme is Oppenheimer’s nightmarish internal conflict: his role in stopping the most destructive conflict in history, while simultaneously opening the door to a near-certain world future of even more horrifying ones.

And then just a few days ago, the Associated Press ran a brief oh-by-the-way report of the Russians’ announcement that their RS-28 Sarmat ICBM is now fully operational, a powerful new nuclear weapons delivery system that Vladimir Putin opines will make the rest of us “think twice” before threatening Russia.

With more important news like Trump indictments, Biden speeches, and bad weather everywhere, the AP announcement attracted little attention. That’s no surprise — we have been living in the nuclear age since before most Americans were born. The forever arms race sounds scary, but (so far) Armageddon has not materialized.

But some internet-poking turned up a few more details. Sarmat (also known, appropriately, as “Satan II”) is reportedly a huge silo-based rocket capable of delivering as many as 15 nuclear warheads to targets 11,000 miles away. One Russian politician, Aleksey Zhuravlyov, chairman of the nationalist Rodina party, was quoted as bragging that “one Sarmat missile and the British Isles are no more.” So there.

The nuclear threat is not diminishing, but it’s incomprehensibly ugly, so we look the other way.

Think back. The 1963 Cuban missile crisis is unforgettable for people of my age. A few years later, still in the height of the Cold War, I served as a naval officer aboard a U.S. nuclear submarine — operating in uncomfortably close contact with Soviet submarines, no doubt armed as we were with advanced weaponry and the potential, by intent or mistake, to trigger a catastrophic war.

Since then, I’ve viewed the existence of nuclear weapons — some in the hands of brutes like Vladimir Putin, a man demonstrably willing to lob missiles into apartment buildings full of civilians — as the one true existential threat facing our world.

For almost eight decades, the world’s nuclear powers have been facing one another in an uneasy standoff — an OK Corral where each gunslinger eyes the other warily, ready to draw and fire if the other moves (or seems to) first.

In 1985, Presidents Ronald Reagan and Mikhail Gorbachev together confronted that stark reality, declaring (in the preface to the Strategic Arms Reduction Treaty) that “a nuclear war cannot be won and must never be fought.” Nevertheless, nearly 40 years later, the combined arsenals of these two nations include approximately 11,000 nuclear warheads. Neither side can find a way to put the nuclear genie back in the bottle; and so, the world is condemned to maintain war chests powerful enough to destroy the planet — and hope no one ever uses them.

The Oppenheimer movie captures that dilemma perfectly. Along the way, it provides historic clarity, pointing out that nuclear weapons were inevitable. By the early 1940s, the mysteries of the atom had been solved, and it remained for them to be used, or abused, by mankind. And it retrospectively endorses President Harry Truman’s decision to deploy the frightfully destructive new weapon against a nearly defeated enemy. Japan’s fanatical refusal to back down, demonstrated grimly only months earlier in the Okinawa campaign, had made it clear that continuation of the war would result in far greater casualties, American and Japanese, than use of the bomb.

The film has been the subject of some criticism for underplaying Oppenheimer’s known pro-communist sympathies. That’s irrelevant, in my view. Oppenheimer’s extraordinary contribution to our country’s effort to win (and thus stop) that awful war speaks for itself.

But the movie’s central message is the one that matters most. The closing scene is an imagined post-war conversation between Oppenheimer and the much older Albert Einstein. Through superb script writing, these two real-life counterparts provide a remarkably clear explanation of the fundamental quandary of the dawning nuclear age.

In that scene, Oppenheimer and Einstein reminisce about one of the scientific uncertainties they’d confronted in their quest to build the bomb — the unlikely but hypothetically possible outcome that the nuclear chain reaction would be unquenchable, consuming the earth’s atmosphere and destroying all life on the planet.

“What of it?” Einstein asks, pointing out that it didn’t happen — we did not destroy civilization.

Oppenheimer’s rueful answer: “I think we did.”

Existential threat? No question.