There's a scene somewhere in the middle of a new flat Earth documentary that acts as a metaphor for so much that surrounds it. Two of the central figures of Behind the Curve are visiting a spaceflight museum that pays tribute to NASA, an organization that they believe is foisting a tremendous lie on an indoctrinated and incurious public. One of them, Mark Sargent, sits in a re-entry simulator that suggests he should press "Start" to begin. He dutifully bangs away at the highlighted word "Start" on screen, but nothing happens.

He wanders away muttering even more about how NASA's a giant fraud. Meanwhile, the camera shifts back to the display and zeroes in on the giant green "Start" button next to the seat Sargent was in.

Into the fringes

It's hard not to think back to two earlier scenes in the movie. In the first, Sargent talks about how he started having suspicions about the globe when he spent weeks watching a flight tracker for flights crossing the southern oceans but couldn't find any. This seemed to fit with his favored model of the Earth's disk, one with the North Pole at the center and the continents spread out like spokes from there. This would place the southern continents much farther apart and make air travel prohibitive—just as the lack of flights suggested.

A short while afterward, Behind the Curve shifts focus to a Caltech astronomer who brings up a flight tracker on her laptop and quickly finds planes in the middle of the southern oceans. It's not clear how Sargent missed these or why he didn't skip watching and just check a travel site for nonstop flight offerings (I easily found routes from Auckland to Santiago and Sydney to Johannesburg).

Head-scratching scenes like this abound as the film crew follows a number of flat Earth community members in the build-up to a major convention. The community is tight-knit, supportive, and willing to overlook details like having completely incompatible ideas about how the world is actually structured—as long as it's not spherical, it's OK. They readily swap stories about the ideas that led them to break with physical reality and join the community, and they candidly discuss the losses of family, friendships, and marriages that accompanied that break. It's clear that, for many of the subjects, their beliefs provide them with access to the benefits of being part of a community, something they might struggle to get through by any other means.

The one thing that does seem to cause problems is the community's tendency to see conspiracies behind everything. That tendency eventually gets focused inward toward its own members. At one point, a prominent source of flat Earth YouTube videos accuses two other videomakers of being plants by the nefarious powers behind the spherical conspiracy. But that thread can't be followed further, because the individual making the accusations demanded a large fee and creative control over the documentary in return for appearing in it.

Where do things go wrong?

Behind the Curve isn't all fringe perspectives, though. Sprinkled among these characters is a handful of actual scientists (and one science journalist) who keep the proceedings grounded in physical reality. As in the flight-tracker example, they frequently provide information that raises the question of how a belief system could get so divorced from an easily checked reality.

Fortunately, researchers in social and behavioral sciences have identified various ways in which we selectively filter information based on our cultural identity, how the Dunning-Kruger effect gives us misplaced confidence in mistaken conclusions, and how some people get bogged down in conspiratorial thinking and start seeing everything as a facade hiding the truth. All of that is there in spades—the movie's subjects make a compelling case that behavioral scientists know a lot more than they're often given credit for. And a few of those behavioral scientists get to speak on camera for those who aren't as up to date on the academic literature in this area.

Behind the Curve's editing and source material gets all of this across without being preachy or going out of its way to make its subjects look bad. It's compelling viewing and refreshing to see some of the academic descriptions of human behavior brought to life. For those who aren't as up on this research, it's a fantastic illustrated introduction.

But I'd argue that there's value to Behind the Curve beyond that. To begin with, it's easy to see that a general acceptance of conspiracies is a key factor for many in the flat Earth community; Patricia Steere, one of the other focuses of the film, rolls off a list of other things she's skeptical of, including vaccines, GMOs, chemtrails, and 9-11. So why—out of all those options she's prone to view as the product of a conspiracy—is she putting her efforts into proving the Earth flat?

Hearing so many origin stories over the course of the film provides some hints about common features among people's journeys into the fringes. And that's important to know if we're ever going to catch people before those journeys are complete and things like cultural cognition and Dunning-Kruger issues lock them into their destination.

Not strictly anti-science

There's also a reminder that all the people on the reality-based side of the flat Earth issue may have their own irrational belief: that erroneous beliefs won't survive contact with reality and that the supposedly anti-science attitudes of the people who hold them will crumble in the face of evidence. Behind the Curve makes clear that flat Earth proponents are not anti-science, a point driven home by an astronomer who's given the chance to riff on science communication. The film itself includes at least two experiments meant to show that the Earth is flat, one of them involving the purchase of a $10,000 gyroscope.

The gyroscope naturally shows that the Earth is rotating. Rather than admitting defeat in the face of evidence, the person behind the experiment convinces himself that the gyroscope must be picking up something else that's rotating (maybe the stars above the Earth?). He goes to increasingly ludicrous methods of trying to isolate it from that influence. How to get reality to break through that level of commitment is a serious challenge for people who care about evidence-supported policies.

So even if the subject makes you want to bang your head against the wall, I think there's a lot to recommend in Behind the Curve. It's found a great collection of sources and edited the material provided into some compelling narratives. And there's more here than just the opportunity to laugh at people with silly beliefs, provided you're willing to invest some time in the ideas that aren't always described overtly. In fact, the conspiracy minded might think that's what the filmmakers were hoping you'd do.

Behind the Curve is currently streaming on Amazon, Google Play, and Netflix.