Tenet explained: Discussing inverted entropy, temporal pincers

Christopher Nolan's Tenet finally landed in India this Friday, and while fans of the filmmaker have been waiting with bated breath to finally be able to experience his vision on the big screen, the response hasn't been unanimously positive. Criticism for the film seems to be focussed on two things: its complicated plot and unclear sound mixing.

Starring John David Washington, Robert Pattinson, Elizabeth Debicki, Dimple Kapadia, Michael Caine, Kenneth Branagh and others, Tenet is Nolan's take on an old-school spy thriller, with his own science-fiction spin.

The film introduces a concept known as 'reverse entropy'. Nolan in an earlier interview to Entertainment Weekly had said, "This film is not a time-travel film. It deals with time and the different ways in which time can function. Not to get into a physics lesson, but inversion is this idea of material that has had its entropy inverted, so it's running backwards through time, relative to us."

Nolan consulted Nobel laureate Kip Thorne on Tenet -- Thorne also worked with the filmmaker on Interstellar -- but ended up relegating some of his suggestions. "I did have Kip Thorne read the script and he helped me out with some of the concepts, though we're not going to make any case for this being scientifically accurate," Nolan said in the film's press notes. "But it is based roughly on actual science."

The Los Angeles Times spoke with Claudia De Rham, a theoretical physicist from Imperial College London, and asked her if the science in the film holds up. "There is some element of physics. There is some element of science. It's trying a little bit. Compared to previous movies, like Interstellar, the gap is maybe bigger. It's far less grounded into physics. There are a lot of times where they use science jargon and it's just jargon with no content," she said.

De Rham also explained the concept of entropy. She said, "Entropy is the measure of the level of order or the level of information. There's a really fundamental law in physics telling us that entropy always increases. On average, things get more and more disorganized. That's why we grow older — our body gets slowly more and more disorganized. That's why it's much easier to destroy something than to construct something. At the physical level, if you have a box and you put some gas in it, the gas will start taking up the whole space. It will spread and get more and more disorganized. When entropy increases, it means things are becoming less and less organized."

Entropy out of the way, Tenet also deals with a concept of 'inversion', which an Empire article explains as: "Inversion is a process whereby an object (or person) has its entropy reversed, essentially flipping its chronology so that from that point on it travels backwards in time instead of forwards."

In the film, the protagonist -- named Protagonist -- is sent on a mission to stop a possible Third World War. At the beginning of the film, an Esquire article attempts to explain, "the Protagonist meets Clémence Poésy's scientist, who informs him that at some point in the future, a technology is invented that can reverse the entropy of people and objects." The tech has been monopolised in the future by a Russian oligarch named Andrei Sator, who has created an 'algorithm' that allows him to 'invert' his 'entropy', via 'turnstiles'.

Sator is dying, and taking a chapter out of the Bond villain playbook, he plans to take the entire world down with him by attempting to 'reverse the arrow of time permanently, which means that rather than simply flowing backwards, the people in the future would be able to overwrite the past.'

The film concludes with a large scale action scene thatunfolds both forwards and backwards, while parallel scenes involving past and future versions of the same characters play out. To stop Sator, several events are put into motion, and a 'temporal pincer' strategy is put into effect. What is a temporal pincer, you ask? According to Empire, "It's a time-bending tactical technique for missions: you approach it moving forward in time, and then also approach it in reverse moving backwards from the future – each side using the knowledge that the other side gained from having already experienced it. Except, both sides are actually experiencing it simultaneously."

The 'heroes' are divided into two teams -- one moving forward in time, and the other backward. "Thus you have inverted and un-inverted Tenet soldiers fighting against Sator's men, while The Protagonist and Ives (played by a near-unrecognisable Aaron Taylor-Johnson), both on the red team, head down into the bunker to nab the Algorithm," Empire continued.

There's also additional information about possible environmental damage and the Earth becoming uninhabitable in the future, but the film doesn't dwell on that too much.

It ends with a revelation. The Protagonist has been the man in charge of Tenet all along. He has already experienced the events of the film, and stuff that happens after it ends. He recruited himself for the mission. His aide, Neil, played by Robert Pattinson, has been moving backwards in time, while the Protagonist has been moving forward.

Esquire explained, "The Protagonist inverted himself in the future, set up the whole mission, then went on to recruit Neil and arm him with the information he needed to help. He also, it would appear recruited himself, setting up the mission which he would recruit his past self into without knowing that the version of him the future is the one pulling all of the strings."

His loop closed, Neil tells The Protagonist, "'What's happened, happened', but instead that in the future the world was always safe because they had already gone into the past to make it so."