The film surprises you with vast silences.

It is an emptiness that at first seems jarring to sensibilities trained to believe every moment must be crammed. By contrast, this movie takes you into moments of pregnant stillness: no movement on the screen, no dialogue, no swelling music to cue your emotions. At one point, the camera takes what feels like a minute to study Solomon Northup’s face as he absorbs the awfulness of his predicament. He does nothing. He says nothing. He simply is.

It is silence as respite, silence that gives you room to contemplate and feel. You end up grateful for it, even though most of what you contemplate and feel is painful and sad.

“12 Years a Slave” is based on Northup’s 1853 memoir of the same name. In the movie, actor Chiwetel Ejiofor is Northup, a free black man from upstate New York who, in 1841, is kidnapped and sold. The film has received glowing reviews, all of them deserved. But it is more than a masterpiece. It is also the most unsparing, unsentimental depiction of American slavery ever filmed.

And it could not arrive at a more propitious time.

America practiced the buying and selling of human beings for 246 years — from before it was a country until after that country was torn apart and forced back together over the question of whether the practice would continue. The enslavement of Africans and the murder and forced removal of American Indians are the worst things America ever did to Americans. Nothing else even comes close.

The latter, we don’t talk about. The former, we talk around. We make it a cartoon, a two-gun, two-bit fantasy like “Django Unchained.” We make it a political talking point, as in the esteemed black doctor who deemed the Affordable Care Act “the worst thing that has happened in this nation since slavery …” One struggles to imagine the Jewish response if anyone, let alone a Jew, compared health-care reform to the Holocaust.

We do not revere. We do not respect. At some fundamental level, we do not even understand. Or want to.

So it falls to Ejiofor and director Steve McQueen, two Britons, to tell us this most American of stories. Their movie is not an easy one. Often, its vast silences are filled with soft weeping from its audience. The violence is physical. And emotional. And always.

There is a scene where a woman is beaten, the whip cutting skin down to the white meat of her, blood spraying with every blow.

There is a scene where two men are hanged, legs pawing uselessly at empty air until finally, life grants them the mercy of death.

There is a scene where the camera pans up from Northup, a free man screaming for help down in a slave dungeon, to show, in the distance, the Capitol building of the United States. The juxtaposition is eloquent in its wordlessness.

Some will likely cite the hardness of the movie as a reason not to see it. But it can be argued that, unless one understands the crime this film describes — and that means to comprehend in depth, not to skate through the superficial outlines — one cannot truly understand America, either then or now.

Alex Haley once revealed that the original title of the book that became “Roots” was “Before This Anger.” Haley’s research spanned the 1960s, a time when African-American communities were exploding in riot and rage every summer. The working title was meant to alert readers that these things had context and antecedent.

“12 Years a Slave” can be said to serve the same purpose in an era where African-American communities no longer explode, but simmer with poverty, crime, absence, injustice and neglect. In its searing power the movie commands those lost virtues of reverence and respect. In its haunted silences, it testifies to what America was — and is, still.

The film is not just brilliant. It is necessary.

Leonard Pitts Jr. is a columnist for The Miami Herald. Readers may write to him via email at: lpitts@miamiherald.com.