OK, here is the elevator pitch: We are on a beach. The sea just visible on the right-hand side of the frame. Low camera angle. Black and white. Ghostly flickers superimposed over the main image. A synthesiser chord on the soundtrack. Nothing happens for about 12 minutes. Then we see a black dot and a white dot at the far end of the beach. They are people dressed in robes, walking towards us. In slow motion. By about 20 minutes in, they are near us, gathering debris on the beach. Wait – we are at the ground floor already? But we have only just got started!

There are another seven hours to go, in fact. Though not a lot else happens, to be honest. The black-robed person paints some stuff white; the white-robed person paints some stuff black. Roughly an hour and 15 minutes in, they dramatically exit the scene. But 10 minutes later they reappear, and unfurl a banner. On it is painted … Uh-uh. No spoilers here. But the good news is, this is just the trailer. The actual film, titled Ambiancé, is 720 hours long. You ain’t seen nothing yet – almost literally.

“Slow cinema” has become a bona fide movement, advanced by film-makers such as Béla Tarr, Lav Diaz and Ben Rivers, but Ambiancé is something else entirely. It is nearly 100 times longer than Tarr’s famously challenging Sátántango. And it is 15 times longer than 1968’s The Longest Most Meaningless Movie in the World. Or five days longer than the current Longest Video on YouTube (which is just flashing black and white, anyway). You could call it “slower-than-slow cinema” or “almost static cinema”, although Ambiancé’s Swedish director, Anders Weberg, prefers the term “ambient film-making”.

Weberg is not seeking to break records, nor does he realistically imagine anyone will watch his film in its entirety when it premieres on 31 December 2020 (Star Wars Episode IX should be out of the way by then). The film will play simultaneously on every continent, he promises, but only once. Then it will be destroyed. Ephemerality is something of a theme in Weberg’s work. He began his career directing music videos, then became more interested in experimental film. He has produced several films with titles such as Nothingness, Meaninglessness and Absent (some of which are rather beautiful), and in 2009 he uploaded a series of films on to peer-to-peer servers then deleted the originals. He prides himself on being virtually invisible and unknown.

In that respect, Ambiancé might well be an own goal. Someone has created an entry for it on the Internet Movie Database without Weberg’s involvement. The 72-minute trailer he released in 2014 was viewed 1.6m times before he took it down (he will release a 72-hour trailer in 2018, naturally), and the new trailer has already been viewed more than 320,000 times. Someone has even speeded it up, condensing all seven hours into one minute. The statement on ephemerality has taken on an online life of its own. Perhaps that was the point all along. “It’s very easy to create in a digital world,” Weberg says. “It’s harder to delete.”