What is this article about?

The science behind the movie TENET, which you will soon realize through this article, is a journey of beauty and amazement.

TENET is a 2020 science fiction action-thriller film. Written and directed by Christopher Nolan, this film’s plot revolves around the concept reversing the entropy of things and people, resulting in time reversibility. Nolan took more than five years to write the screenplay after deliberating about TENET’s scientific ideas for over a decade.  In conceptualizing TENET, Nolan took suggestions from physicist and Nobel laureate Kip Thorne, who had also advised him on “Interstellar. The movie beautifully harmonizes imagination with complex physics concepts including the second law of thermodynamics, and Feynman and Wheeler’s notion of a one-electron universe.

Caution: This is a really long and detailed post. So, please skip sections and go to ones relevant to you using the index table.

In this article we will try to simplify these concepts so that a common reader can easily understand the scientific concepts driving this movie.

I will first begin by providing a short summary of the story line. Please note that this part contains “spoilers”. If you have already seen the movie or don’t want to spoil your experience by knowing the entire plot before- hand and if you want to straight move on understand the scientific concepts- click here.

Movie “TENET” Summary (Beware of the spoilers here)

The movie starts with a scene In Kiev, Ukraine. John Washington, playing the lead role called “Protagonist” in this movie, is a CIA operative. His mission at Kiev is to foil an opera siege by terrorists and also retrieve a stolen stock of plutonium. But the events take a nasty turn when the plutonium is found to be fake. In this action packed scene, Protagonist is saved by a masked gunman with a red string on his back. However, the Protagonist ends up getting abducted. He is tortured with teeth being removed with pliers. Somehow he manages to swallow on an apparent suicide pill before revealing any information.

In the next scene, the Protagonist is found waking up to the fact that the suicide pill was fake and the abduction was just a test of his loyalty. His loyalty finds himself recruited into a secret organization and is armed with only two things-  a gesture (two hands with fingers interlaced) and the word “tenet”.

If one observes carefully, the word “tenet” is a palindrome. A palindrome is word, number, phrase, or other sequence of characters which reads the same backward as forward, such as “Hannah” or “Racecar”. This choice of word, as you will soon discover, is not coincidental and matches the scientific theme driving this movie!

Using this word, Protagonist meets a scientist (Clémence Poésy) at a secret facility where he learns that “inverted” objects are being sent from the future. “Inverted” objects are the objects whose entropy is reversed and they move backwards through time. To demonstrate this, the scientist shows him “inverted bullets” that fire in reverse. It is revealed that if the technology for making “inverted” objects is not seized and stopped, it can lead to World War 3 and the destructive power of this technology is worse that of nuclear holocaust.

The whole movie is based on this concept of “inversion” and the associated set paradoxes that follows reversal of entropy. We will simplify this concept and the associated science in this article.

Neil (Robert Pattinson) is a British intelligence agent. The Protagonist takes help of Neil to track the metal from which the reversed bullets are made. During their search, they infiltrate the compound of an Indian billionaire whose wife, Priya (Dimple Kapadia) seems to know what is happening. Priya reveals that that the technology to make “inverted” objects is controlled by a Russian arms dealer, Andrei Sator (Kenneth Branagh).

In order to get close to Sator, the Protagonist reaches out to his estranged wife Kat (Elizabeth Debicki). Sator is a dangerous man and Kat is literally enslaved to Sator’s wishes because she fears her and her son’s safety. Kat reveals the Protagonist that she had cheated Sator by making him buy a forged painting. The painting is located in a safehouse called Freeport which is inside Oslo airport near the tarmac. The Freeport facility is highly secure, designed similar to Pentagon, and is much more than just a storehouse of art collections.

The Protagonist and Neil help Kat retrieve the forged painting by crashing a cargo plane into the Oslo Freeport. During the operation, however, they are attacked by two masked men, one of whom is using a “inverted” gun. The attacker escapes before the Protagonist is able to discover the attacker’s identity.

To return Protagonist’s favour, Kat arranges for the Protagonist to attend a dinner party, hosted by Sator. Here the Protagonist offers to steal weapons-grade plutonium for Sator. The Protagonist, along with Neil and his team succeeds in stealing the plutonium from an armored car at Tallinn. But this operation gets interrupted by an “inverted” vehicle. This is when the Protagonist discovers that Sator and his gang are operating a “temporal pincer movement”. Using this Sator and his operatives are able to move both forwards and backwards in time, by means of entering a chamber called “temporal stile”. While at the “temporal stile”, Sator injures Kat by shooting her using “inverted bullet”. However soon reinforcements arrive to capture the “temporal stile”, forcing Sator to leave Kat behind and escape into past. But now using the same “temporal stile” the Protagonist is able to follow Sator, where he turns out to be the driver of the “inverted” vehicle that had interrupted his operation to steal plutonuim earlier. Eventually the Protagonist succeeds in rescuing Kat but fails to prevent Sator from acquiring the plutonium.

It turns out that Andrei Sator is dying from inoperable pancreatic cancer. And he is obsessed with the idea that if he is to die, he would ensure entire mankind dies with him.

Acquiring plutonium is just a small part towards what actually Sator plans to do, to achieve his goals.

Sator is actually trying to gain hold to “an algorithm created in future” which can cause the “entropy” of the world to reverse. The “algorithm” has been created in the future by a future scientist as a mechanism to reverse time and correct past mistakes, since their future Earth is ruined by decisions made by present-day human beings. Sator grew up in one of Soviet Russia’s Closed Cities called Stalask 12. It is here where Sator finds a note from the future along with gold bars telling him where to find each of the Algorithm pieces. These people from future also send him the means to build a turnstile so he can invert himself and uninvert the gold sent back to him to aid him on his journey.  Sator intends to use this “algorithm” to reverse entropy for the entire Earth, thus killing everything on Earth instantly. Sator’s final implementation plan is to return to a point in time in the past when he was happy with Kat and then link the “algorithm” to his heartbeat such that the “algorithm” gets activated once his heart stops beating.

The Protagonist, Neil and Kat follow Sator backwards in time and discover that he is travelling in a cargo ship container back to Oslo. The trio revisit that segment of past where Neil and the Protagonist had infiltrated the Oslo Freeport. The Protagonist now discovers that the masked assailant who had attacked him during their first operation at the Oslo Freeport was none other that himself! Inside the Freeport they enter another “temporal stile”. This “temporal stile” is now used to move Kat forwards through time again and have her gunshot wound healed.

The algorithm is located to Sator’s hometown ,Stalask-12, in Northern Siberia, where it is heavily guarded. Going further back into past the Protagonist and Neil gather troops to launch a military operation and attempt to retrieve the “algorithm”. They launch a “temporal pincer movement”, with non-inverted red team troops and inverted blue team troops making a simultaneous assault. In the meanwhile, Kat travels to past to the time where she is with her husband on his yacht in Vietnam. Her aim is to prevent Sator from killing himself before the “algorithm” is retrieved. Kat manages to hide from Sator that she has come from future. Eventually Kat kills Sator while the Protagonist and Neil are able to retrieve the “algorithm” in time. It is now when the Protagonist observes that Neil has a red string on his back. Thus, the masked man who saved him during the opera siege at Kiev was none other than Neil.

At the end of the movie, it becomes clear everything that was done to stop Sator was planned by the Protagonist in future- he just didn’t know it because he was in his past. Tenet is the name of the organization that the Protagonist had created to keep the world’s entropy flowing in the right direction. Tenet was created in the future. Its goal was to stop people like Sator  from setting off “the algorithm” that will wipe out both the past and the present.

The interlocking hand gesture, initially described in conjunction with introduction to word “tenet”, indicates backward and forward flowing of time.

Symbolisms with TENET- Science Marrying Art

The Sator Square is a Latin palindrome. The oldest representation of the Sator Square was found in the ruins of Pompeii. It is  made up of five words that can be read backward, forwards, upwards or downwards. Sator Square is believed as perfect expression of a complex palindrome, and Nolan uses it beautifully to craft this movie. Each of the five words with the Sator Square Palindrome is used in this movie. The lead villain is a billionaire Russian called Andrei SATOR. Sator hides a turnstile at the free port operated by ROTAS. Sator’s wife, Kat, presumably had an affair with an art forger named AREPO. Sator attempted to get hold of Algorithm by attacking the OPERA at Kiev and TENET attempted to thwart this attempt.

It’s really a pleasure to watch TENET with palindromes symbolizing the theme of the movie. The word Tenet itself is a palindrome, and so is the movie flow- the movie moves forward in time for the first half, then reverses back to the start. It begins with the mission at Opera House in Kiev, Ukraine where the Protagonist is saved by a mysterious masked man with a red string on his uniform, before he’s recruited and sent on a mission to protect the Algorithm and prevent the end of the world. To achieve this mission, the Protagonist executes two heists before Sator shoots Kat and gets away with the plutonium. Hence the Protagonist goes backwards in time to save Kat and finally try recover the final piece of the Algorithm. At this point when the Protagonist is going backwards in time, the movie goes goes through mirror scenes of what came before – a motorway heist, the airport heist, and finally the military operation at Stalask-12  to retrieve the Algorithm where his life is saved by a mysterious soldier with again with a red string attached to his uniform.

The movie, effectively, is the same forwards as it is backward.

Even the music used in TENET reflects the palindromic theme. Composer Ludwig Göransson ensured that Tenet’s score mirrors the theme. At various scenes in Tenet, for example the interrogation scene, the music is playing backwards. Importantly, Göransson didn’t just reverse the soundtrack — he actually had his musicians play the music backwards. It’s not the only time he played with the music this way. The was music was composed for the final battle was especially intelligent. There are two different scores playing over each other, to match a battlefield featuring inverted and non-inverted soldiers. In the scene where the Protagonist is on a boat with both inverted and non-inverted soldiers following him, Göransson made the music in such a way that it has its rhythm and percussion playing forward, while the orchestra is playing in reverse.

Science of TENET simplified

Basic Thermodynamics for Layman

Before we understand details about entropy and the core science involved in TENET, we need to cover some basics about thermodynamics.

What is thermodynamics?

Like all things in the physical world, energy is subject to the laws of physics. The laws of thermodynamics govern the transfer of energy in and among all systems in the universe. Thermodynamics is the study of energy and energy transfer involving physical matter.

What is system and what are surroundings?

Imagine a scenario of heat exchange between a stove and a bowl of soup on it. This set (the stove, the bowl and the soup) will be called as a system. Everything outside of that system is called the surrounding. Energy is transferred within the system (between the stove, bowl, and soup). So, when you are heating a bowl of soup on the stove, the system includes the stove, the bowl, and the soup, and the air around this stove-bowl-soup system can be regarded as the surrounding.

What are open and closed systems?

As per thermodynamics, there are three types of systems: open, closed and isolated. A closed system does not exchange mass with its surroundings. A closed system capable of exchanging only energy with the surroundings. In comparison, an open system is one which is capable of exchanging both mass and energy with its surroundings. An isolated system is a system that does not exchange mass or energy with its surroundings.

Look at Earth. It only receives sunlight (energy), while its overall mass stays constant, nearly without any exchange from space. Thus, Earth can be considered as a closed system. Another example of a closed system is a frying pan on a stove with a lid over it tightly snugged. In this situation the frying pan receives heat (energy) from the stove, while no mass enters or leaves the frying pan, thus making it a closed system

We are typical examples of open systems. Energy is exchanged between us and our surroundings, as we consume energy-storing molecules and release energy to the environment by doing work.

What is Entropy?

Entropy is a concept that flows directly from the Second Law of Thermodynamics. This law states that for any system – say an auto engine – the entropy measures how much of the system’s energy is lost to friction-like processes. Friction in any engine turns energy into heat. This heat represents loss of energy  can never be recovered for engine’s use. With time this loss of energy (called entropy) keeps grows as the system functions. Thus the direction of the increase in entropy defines the way to the future. Entropy has been poetically called “the arrow of time” because of this one-way property of systems.

Let’s now try to understand entropy in simple language. Entropy can be imagined as a measure that tells you how “disorderly” a system is. More “orderly” the system is, less is the entropy. Imagine a book with all pages well bound and organized as per the table of contents. If you tear off each page and mix the pages randomly, you have introduced “disorderliness”. In other words you have increased “entropy” for that book.

Imagine a balloon that is first filled a little with Gas A. As the gas fills up the balloon, the molecules of the gas spread inside the balloon and keep moving randomly. This makes the system more disorganized, which is referred to as increase in entropy.

Still, in this example it is easy to locate molecules of Gas A in the balloon because there is only Gas A in this balloon. Now, let’s say you fill a little Gas B in this balloon. Gas A and Gas B molecules will mix within each other. It will now be a bit more difficult to accurately locate Gas A molecules. Entropy is now a bit more. Now imagine one more gas- Gas C getting introduced in this balloon. Now the molecules of Gases A, B and C are all mixed and jumbled. Entropy is high.

Let me give another example to drive this concept home. Imagine you have a transparent jar. Now put some rice in this jar. Above this layer, now create another layer with wheat grains. Then, create another layer with grains of millet. If you look at this jar from outside, you can easily see that the grains are well organized with rice grains at the bottom, wheat grains in the middle and millet grains at the top. Now, shake the jar. Shake it hard. Roll it and turn in up and down several times. Now, everything is completely disorganized. All the different grains are mixed up with each other. The entropy of the jar’s contents has shot up due to this shaking.

Its a fundamental law in physics that tells us that entropy of any system always increases with time. On average, things in any system keep getting more and more “disorderly”. With time, any system gathers new elements. These elements can be objects, particles, information- anything. Addition of each element tends to add to the complexity of the system and increases chances of disorderliness. With passage of time, more and more elements enter the system and disorderliness keeps increases. Thus, for any system, entropy increases with time.

In living beings, aging itself is believed to be an outcome of this increasing entropy with time. As we grow, the number of cells keep increasing. Each cell added can be imagined as an element getting introduced into the system. We have so many interactions with millions of viruses and bacteria that roam around in the air we inhale, the water we drink and the food we eat. Each such interaction is again like an additional element getting introduced. In short, each minute we live increases entropy in our body. That’s why as we grow older, our body gets slowly more and more disorganized. Entropy is also the reason why it’s much easier to destroy something than to create something!

The mathematician of world acclaim, James R. Newman, called this direction of entropy as “the general trend of the universe toward death and disorder.“

What are “Inverted” Objects in TENET?

Reversal of entropy has been called as “inversion” in TENET. If you have understood the concept of entropy you would have guessed that time moves in the direction of entropy. As time passes, entropy increases. What simply follows with this understanding is that if an object is “inverted”, it moves backward in time. Such an “inversion” will naturally reverse the sequence of cause and effect. In our world, the cause is followed by effect. But if something is moving backwards in time because it is “inverted”, cause- effect relationship will get reversed in direction. Effect will come first and then the cause. In forward-moving time, a gun shooting a bullet will cause a hole in a wall. If time is in reverse, we will see the hole coming before the bullet is shot from the gun. The bullet will appear moving from the hole into the gun!

Relation of “inversion” with “entropy”

Think of a raw egg being dropped on the ground. So long as time is moving forward- from past to present to future- the egg will hit the ground and then get smashed. In other words, if time moves in forward direction, it will always lead to egg getting smashed. Imagine the fraction of moment when this egg has touched the ground and the egg shell has started cracking. So long as time is moving in forward direction, this egg will never reform as a whole egg- it will always proceed to get completely smashed. Whole egg is the time point when egg’s entropy is low, while the time point where egg got completely smashed is when entropy for this egg is very high.  Once again, this example shows that entropy represents direction of time.

The reason why I am trying to again again emphasize that entropy represents direction of time is that in the fundamental physics equations there is actually nothing that says anything about which way time should flows. In physics, there is no difference between the past and the future- every point in the time-space is equally valid and ‘present’ is, as per physics, nothing special.

So, if you were lost in time and you are clueless regarding which way time was flowing, you could just look at the entropy of any closed system. The direction in which the entropy of that system was increasing would be the direction in which time is moving forward.

However, there is only one equation in the entire physics that defines a specific direction to the movement of time- this equation resides in 2nd law of thermodynamics that deals with entropy.

Its only equation of entropy that ensures that an egg that has started cracking on touching the ground when dropped will always end up getting smashed and not reformed into a whole egg! All the other relevant laws of physics are symmetrical: anything that can happen forwards can also happen backwards.

In our world, we only perceive one direction of time- one that flows from past to present to future. Lights don’t get turned on before its switch is turned on, smoke does flow back into the cigarette and shattered eggs don’t reassemble to become a whole egg. If the bulb- switch system is “inverted”, bulb will glow first and then the switch will get turned on. If the cigarette is “inverted” smoke will not come out of cigarette but will flow into it. An “inverted” smashed raw egg will reassemble into a full egg and rise from the ground to the hand from which it had supposedly fallen.

And one can be seen a bullet with his gun, as it happens in TENET, when the bullet is “inverted”.

Since flow of entropy is inverted, the direction of heat transfer is also reversed. This means an explosion will lead to formation of ice rather than flames. This is exactly why the Protagonist suffers from hypothermia instead of burns when he gets engulfed in flames.

Why do you need oxygen cylinder if you are “inverted?

If you’re inverting is not an object, but a human being, it can mean death for that person. For a person who has gone through the turnstile he/she might be moving backwards, but everything else is still moving forwards. This makes such “inverted” person disoriented and the world becomes a dangerous place for such a person to navigate. Even the air is unbreathable. It would be impossible for an “inverted” person to breathe air that is experiencing an opposite flow of time to him. The functioning of “inverted lungs” will be reversed compared to what happens in the lungs of any normal human being. Normally, air will be inhaled, it will be absorbed by lung membranes, oxygen will be extracted and CO2 will be released and this CO2 will be exhaled.

In “inverted” lungs, you will have CO2 going in and oxygen coming out and its a quick death for such an “inverted” person. Hence, every person that gets inverted via turnstile wears a gas mask connected to cylinder that supplies special type of oxygen.

But then you find yourself wondering about a scene in the end part of the movie where Kat is with Sator on a Yacht at Vietnam again. In this scene Kat knows she is visiting her past. She is able to see the other version of her (who was present naturally at that time) on a separate boat with her son. In this scene it is natural for viewers to assume that this Kat on the Yacht is “inverted”. But, if she is “inverted”, where is her oxygen mask? Is it an error Nolan made? Actually no! If you have been carefully tracking the timeline while watching the movie, you could have understood that this Kat would not need any special oxygen at all.

Remember few scenes back when Kat was inverted and had a gun shot wound? In their attempt to save Kat, the protagonist and Neil take her to the door in the airport and revert her. But this normal “reverted” Kat is still in her past and as time moves forward for Kat she is able to visit that part of timeline where she is in Vietnam on the yacht with Sator. At the final yacht scene where Kat ends up killing Sator, she wasn’t inverted. I repeat, time is moving normally for Kat here. And hence, she did not need any special oxygen supply to survive!

With this scene, Nolan brings out a fantastic possibility from quantum physics that “multiple realities” can co-exist in the same universe. We will explore this in detail very soon!

What is a Turnstile?

In general, a turnstile is a kind of gate which allows one person to pass at a time. In some places such gates are also called a turnpike or baffle gate.

In TENET, turnstile refers to a chamber that acts as the gate between the two directions of entropy. At some point in future, a scientist discovers how to make “inverted” objects using nuclear fission. This technology led to creation of “turnstile”- a chamber that inverts the entropy of anything (including people) placed inside it. Once anything is processed by turnstile that person or object begins to move backwards through time instead of forwards. In the same way, a turnstile can be used to revert the entropy of any “inverted” object.

By inverting objects using the turnstiles, people in the future can wage war on the past. This is how the then young Andrei Sator was contacted by the people from the future by sending gold and instructions to Stalask-12. Use of turnstile gave the benefit of hindsight to the people of the future- hence they had a major tactical advantage over the present day people.

The Concept of Multiple Realities Co-existing

In the movie, Neil tells the Protagonist that positrons could be electrons that are moving backwards in time. This idea actually stems from the proposition made by scientists Richard Feynman and John Wheeler.

For uninitiated readers, let me quickly cover the basics. Everything in this world is composed of small microscopic units called atoms. I, you or anything you see around us are composed of millions of atoms flocking together. Each atom is made of protons, neutrons and electrons. Protons and neutrons are quite heavy and are located in the center of an atom. This center of atom can be called as nucleus. An electron are extremely light compared to a proton or a neutron. Electrons are located in the peripheral zones surrounding the nucleus and they keep constantly moving at a rapid pace around the nucleus.

Electrons are negatively charged while protons are positively charged. Neutrons don’t carry any charge- they are neutral. Thus the nucleus of any atom is positively charged as it is composed of protons and neutrons while the peripheral zones surrounding the nucleus have negative charge due to the electrons. Generally, in an atom the total positive charge carried by the nucleus is always equal to the total negative charge carried by the electrons. This makes an atom (generally) a neutral particle. This is for atoms present in most of the objects that we see around us.

As per quantum mechanics, every particle will have an “anti-particle” with same mass but with opposite electrical charge. As Electrons are particles that hold a negative charge, positrons are antiparticles corresponding to electrons. Positrons have the same mass as electrons, with an equal-but-opposite positive charge. Similarly, there are other antiparticles that are “mirror- images” of other types of particles such as neutrons or protons. These corresponding anti-particles are called antineutrons and antiprotons. Collectively all antiparticles are together known as antimatter.

So, positrons are are the mirror image of electrons. As per Feynman-Wheeler theory, if you were able to force time’s arrow to march backwards for an electron, it would look like a positron. Thus a positron can be imagined as an “alternate self” of its corresponding electron with time direction reversed. And the beauty is that- they co-exist. It is this theory which gets imported straight into TENET.

In the film there are two versions of the Oslo Freeport fight scene. In the first version, the Protagonist fights a mysterious inverted man. In the later version of the same scene it is revealed that this man the Protagonist is fighting is no one but his own “inverted” self.

So, first time around, we think that the Protagonist and the man he’s fighting are two different people. The second time, we realize that we’re seeing two versions of the same person fighting with each other. The scientists Feynman and Wheeler had proposed that what we perceive as a particle and an antiparticle could actually be the same particle moving both forwards and backwards in time. So, the Protagonist and the “inverted self” he is fighting in that scene are actually the same person- one moving forward in time and other backward.

I don’t want to complicate things further- but if the same electron moves backwards and forwards multiple times in time, it will end up creating multiple “self- images” (both “inverted” and “non-inverted) of itself. This was actually suggested by Feynman- he suggested all electrons are the same one and single electron, moving back and forth in time creating the complex world that we live in. This is what I meant when I said earlier.

Nolan brings out a fantastic possibility from quantum physics that “multiple realities” can co-exist in the same universe.

If this “multiple reality of a single self” has really gone bouncer, then please do apologize me. Quantum mechanics really comes up with some weird possibilities which don’t look believable or imaginable. But this is the same science that allows us to send a spaceship accurately into moon and accurately predict where it will land on moon without an inch of deviation.

What are “Temporal Pincer Movements”

In TENET people from future are waging war on the present. To wage this time war there would be battle tactics unique to fighting across time as well as space. One such tactic that’s used several times in this movie is the “temporal pincer movement.” In a temporal pincer movement, an army is split in order to wage attack on the enemy from two directions. But the two directions are temporal in nature and not spatial. One team enters the battle normally, reporting everything that happens to a second team that’s on standby. The second team then gets “inverted” via a turnstile and attacks the enemy from the opposite direction. But since this second has the benefit of the first team’s knowledge in terms of how the battle proceeds, they have a critical advantage over the enemy in predicting the enemy movements.

The movie is full of such temporal pincer movements as the Protagonist tries to find the final piece of the Algorithm. Sator uses a temporal pincer movement at Tallinn. This is why the Protagonist’s attempt to trick Sator with an empty case of plutonium fails. In that scene, when Sator is holding Kat hostage in the car, he is actually  “inverted”. In the meantime, the “non- inverted” Sator is waiting at the turnstile with a radio, getting reports about all that is happening on the highway. That’s why Sator counts using his fingers rather than by speaking as n anything he said would come out reversed. This is how when the Protagonist throws the case towards, Sator already knows that it’s empty and there is no plutonium.

Similarly the Protagonist and the soldiers assisting him use temporal pincer movement during their siege on Stalask-12 at the end of the movie. They are divided into two teams: Red Team, who are moving forwards in time, and Blue Team, who are “inverted”. As explained earlier, both teams have the benefit of the other team’s knowledge of what happens. This is how they are able to synchronize the destruction of a building exactly while the fight is half way through. But even Sator’s men have access to a turnstile, and therefore even they have both normal and inverted soldiers in the field. However, the Protagonist and his soldiers do not actually intend to win the fight. Their idea is to make it look like they’ve failed. And while this cover of losing battle is being created, Ives and the Protagonist secretly remove the Algorithm from its tomb before it’s buried by the explosion. The final idea to ensure Sator will die thinking he’s won, but the enemies from the future won’t get the Algorithm.

What happens if you come in contact with your “inverted” self?

TENET clearly lays out the rule that you may never touch your “inverted” self. The danger of breaking this rule is nothing less that annihilation.

In physics, whenever any particle (like an electron) collides with its antiparticle (a positron) it leads to annihilation of both- the particle and its antiparticle, both, disappear and energy is released. Therefore, an inverted person interacting with their past self could cause both versions of that person to be destroyed. This is why you find agents wearing protective gears when they get “inverted” via turnstile.

At this point it is important to emphasize that several people who have seen this movie have developed an incorrect perception of how Nolan imagined time inversion. When you get processed by turnstile you enter a world where “your” entropy is flowing backwards compared to the world around you. But whose entropy is flowing backwards and whose entropy is flowing forwards is determined by who is making the observation. If you have gone through turnstile and are now visiting past, as per you- you are normal and the world you are in has entropy reversed. But for a person observing you from this world, its you whose entropy is inverted.

This observer point of view is very important to keep in mind while judging what is normal and what is not normal. Imagine a train running at 100 miles/hour speed. Inside this train there is a family of four- the parents and two kids sitting across in their respective seats and watching the world from the window. Through the window they can see a house. Inside that house there is a small girl watching that train speed away.

For the family inside the train, each one of them is sitting and not moving. But from the perspective of the small girl from the house watching this train, each and every member of the family on that train is moving at the speed of 100 miles/hour in forward direction. Infact, from the perspective of the family on this train it is the house which is moving away in backward direction at 100 miles/hour.

Who is correct? As per physics, both are correct from their own point of view!

Another important point one needs to understand is that Turnstile does not individually invert every particle in a person’s body. If it did that, the Protagonist would be converted into antimatter and he get destroyed on coming in contact with the normal particles of the outside world. Expert views indicate that the amount of energy released from such annihilation of one “anti- person” would actually destroy the whole world. This concept of massive destruction via contact of “anti-matter” with normal matter was beautifully captured in the movie Angels & Demons. In that movie the bomb containing just one-eighth of a gram of antimatter was shown to have enough power to blow up the entire Vatican city. Calculations reveal that if a 200 lb man like the Protagonist was converted into antimatter, the result would be a devastating explosion equivalent to around 3800 megatons of TNT.

To help you imagine what this means, let me offer you the example of  the Russian hydrogen bomb Tsar Bomba. Tsar Bomba is the most powerful nuclear weapon ever created and tested. During a test Tsar Bomba’s detonation shattered windows and destroyed roofs hundreds of miles away from the blast zone. The yield of this test detonation was calculated to be at 50 megatons. Now compare this with the 3800 megatons!

So what happens when you get processed by a turnstile? It appears that what a turnstile actually does is it creates a closed system where your body continues to experience normal entropy, but you are able to move backwards through time within the bubble of this closed system. For each object that goes through turnstile, turnstile creating a small, closed universe around that object where time flows in the opposite direction to the larger universe outside. If you went through a turnstile and remained inverted for a very long time, from a normal perspective, you would look like an old man who is getting younger. But within the closed universe that turnstile has created around you, however, you would be ageing normally.

It’s also important that the turnstile’s entrance and exit are in different places. If they were in the same place then a person entering the turnstile could collide with his/her inverted self exiting the turnstile and can cause annihilation.

What is the “algorithm” in TENET?

What if, instead of inverting a few objects or people, you inverted the entire universe’s flow of time and entropy? This is exactly what can be achieved if you have the “Algorithm”. The “algorithm” is a chunky object consisting of 9 different parts. The Algorithm was created by the same scientist who created turnstiles in the future while experimenting various ways of “inverting” objects. When she realized how algorithm can be used to end the world, she divided the Algorithm into nine parts, inverted them and sent them back in time.

If someone is able to gather all these 9 parts and reassemble the Algorithm he/she will have the power to end the world. The Algorithm, on activation, will cause every particle in the world  jump back and forth in time simultaneously. This will start creating anti- particles. Every existing particle in this world will start colliding with its anti- particle. This would cause instant mass annihilation.

Sator is the chosen one for carrying out this devastation because he is willing to sacrifice the world alongside his own death. In the movie Sator is found repeatedly saying- “if I can’t have it, no-one can.” And according to Sator it is more than justified to destroy the past so that future can be saved. It’s a response to decisions made in the past that leads to destruction of the planet beyond the point of redemption. The implication of this is that the “future” earth is dying to such a degree that the only answer is to turn back in time and make corrections. But this leads to grandfather paradox!

What is Grandfather Paradox?

In the movie Neil talks about “grandfather paradox” and claims that its a paradox because it is unsolvable. The grandfather paradox is one of the most famous logical problems associated with time travel. As per grandfather paradox it would be impossible for a man to travel back in time to kill his own grandfather because he would then never have been born to travel back in time. If you travelled to your past killed your own grandfather, you would never be born, and therefore you wouldn’t be able to go back into the past and kill your own grandfather. Due to this paradox it’s impossible to suggest whether the future would cease to be if it wiped out its own present. However, in TENET, the enemies from the future seems to to have solved this paradox. That’s why they planned to annihilate the past world without the fear of ending up destroying them as well.

So, how did these enemies from future solve grandfather paradox. This again leads to the final theme that Nolan was trying to bring via Tenet- the possibility of multiple realities which we discussed in detail earlier. In the world where multiple realities are possible, by travelling into past and killing your grandfather you would create an alternate timeline in which you were never born. However, the version of you that killed the grandfather would continue to exist, because the timeline that you came from would still be intact.

In TENET you also find Neil repeatedly saying “what’s happened happened“. It has a special meaning in the movie in relation to grandfather paradox. The very fact that grandfather is living in the first place means the plan to kill the grandfather must have somehow failed. This means Neil was sure right from the start that Neil and the Protagonist would end up successfully averting the future enemies’ plan to destroy the “past” world.

Why does Neil die?

After the final battle in the movie Neil decides to invert again so that he can go back, unlock the gate for the Protagonist and sacrifice his life to save him. At this point Neil reveals that he’s actually known the Protagonist for years. The Protagonist had created Tenet in the future, recruited Neil, and set up a temporal pincer movement of unimaginable scale, designed to stop the enemies from the future from getting hold of the Algorithm. Neil goes on to explain they haven’t yet reached the end of the war, but they are at the middle of it. Neil explains that the Protagonist now has to use his knowledge of how things played out to implement all the things that enabled them to win.

In the end, Neil chooses to die because he knows that it has already happened and his death is necessary for The Protagonist to stop the Algorithm from being buried. Neil indicates that his death is inevitable simply because “what’s happened, happened”. The logic, which is reinforced throughout the movie is that time really cannot be changed. This is exactly why the Protagonist says early to Neil that the very fact that they are still alive to be able to start their mission suggests the mission was already successful.

Healing of Kat- Explained

Gunshot wounds from an “inverted” bullet have been described in the movie as extremely dangerous. They are particularly more dangerous because of the radiation poisoning that comes with being shot with an “inverted” bullet. Remember- the technology involved to “invert” any object used nuclear energy. So even if one managed to heal Kat’s wound, she would still have died due to radiation toxicity. Hence the Protagonist fights with all his might to take her to a turnstile and enable her “inversion”. The idea was that Kat’s inverted cells would reverse the radiation and lead to complete healing. Kat’s “inversion” effectively pushed the fatal injury out of her cells and she was able to survive.

Final Note

Christopher Nolan used INTERSTELLAR to accurately portray what it would be like for a person to travel through a black hole. Through TENET Nolan helps us imagine what it would be like for a person to travel through time in reverse. For such reverse time travel, the concept to entropy has been central focus in TENET. Just by making entropy reverse, through TENET, Christopher Nolan shows how multiple realities of a single object can exist. This imagination is supported by current models of quantum mechanics.

Because I am at the end of this really long post, let me conclude by giving a glimpse of a theory in physics that makes us believe that there are two universes- both mirror images of each other. This theory is called  the “Janus Cosmological Model (JCM)”. As per JCM, the Universe actually started as two mirrored universes with ordinary matter in one and anti-matter of opposite charge in the other (just like electron and its “mirror” positron). Those two Universes would have been created from the same Big Bang singularity- but one moved forward in time and the other moved backward. Our universe that we live in expands in one direction from the singularity  (this point is known as Janus point- the point where all started when Big Bang took place) while our twin universe expands in the opposite direction.

With this post, I hope I was able to ignite a fire of curiosity that should set ablaze your imagination and make you read more on such topics. Let me know your thoughts in the comments section.