Tenet Film Analysis (2020) | TENET EXPLAINED: Time Inversion, Entropy, and more!

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Today i’m going to be attempting to explain five key concepts from tenet. If it is not obvious already this will be full of spoilers.


Let’s start with the underlying concept of time inversion. We experience and perceive time as moving always in a linear forward direction. Within the tenet universe, there exists a turn-style machine that allows for the opposite for the person using it to experience time moving backward.

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Picture this you are in the red side of the machine normal time. You look at your watch the hands are taking clockwise i.e. forwards. You enter the machine at 10 30 am you exit the machine on the blue side. Time is now inverted so the hands on your watch are now ticking counter clockwise i.e backwards. You stay on the blue side for half an hour which means the time now reads 10 am on your watch you re-enter the machine on the blue side and exit the machine on the red side. Your watch is back to normal ticking clockwise, but it still reads 10 am. In essence you have traveled back in time 30 minutes.

I will get to the grandfather paradox in a bit but let’s first look at the rules of time inversion. One thing the film does make clear is that you need your own supply of oxygen. If the entropy of things is reversed in inverted time then you are essentially breathing out the oxygen your body has and you need to counter against that. The only issue i have with this being a side effect of time inversion is that other bodily functions should be affected as well.

If for example your liver is drawing toxins from things you consume rather than getting rid of them then wouldn’t your body eventually poison itself? I haven’t come to a conclusion about this yet.

The next question is how long can you stay in inverted time? Theoretically you could spend your entire lifetime inverted as long as you’ve taken enough oxygen with you through the machine. One thing to note is that you are not de-aging when inverted. It isn’t a Benjamin Button thing. Time as we experience it is reversed but you are not traveling back in time or overwriting events that have already happened. Think of it more as adding to or reusing time that has already passed.

So when i say that you can spend your entire lifetime inverted that doesn’t mean going from say age 30 down to being a baby and then unborn somehow. You age normally. So if you enter the machine in 2020 and stay in inverted time for 30 years, you would end up in the year 1990 aged 60.

One theory going around the internet is that Neil is actually Kat’s son. Throughout the film we get hints that he knows more than he’s letting on. He seemed overly concerned with cat’s bullet wound. It seems that Neil was first recruited by the protagonist after the events of the film. At some point was inverted to before the start of the film. This would definitely be able to cover the 10 to 20 years needed for Kat’s son, who is a young boy in the film to become adult Neil. Both using normal and inverted time.

Another thing to consider with time inversion is that if you wanted to go back to normal time at some point you would need a turnstile machine to do so. Therefore if you travelled inverted for too long before the time that these machines are invented you are doomed to be inverted forever. To solve this you would likely need to bring a machine with you or at least the instructions on how to build one whilst inverted.


Let’s go back to my 30 minute time inversion example. This gets confusing after you’ve completed the journey: what happens in the next 30 minutes? During that time there will be three instances of you at once.

  • The current one the one who has done the journey back and forth.
  • The inverted one on the blue side.
  • The original one who will enter the machine at 10 30 am.

So what happens if your current self-interacts with the two other versions of yourself? What would happen if you killed the original version of yourself that enters the machine in the first place? These questions are essentially the basis of the grandfather paradox that is referenced in the film. On a much smaller time frame.

The grandfather paradox asks if you go back and kill your grandfather, you cease to exist because you are never born. If you are never born you cannot go back and kill your grandfather. Therefore your grandfather lives and you exist to go back to kill him. A paradox!

With tenet the emphasis is on the most current version of yourself. If you did kill the original version that goes into the machine, then you would still continue to exist having done the whole journey already. This concept of time inversion has a parallel in antimatter particle physics.

The point of time inversion is that you still exist on a forward-moving timeline. But time itself is non-linear. You are not accessing alternative timelines or realities to your own. You are in the same reality. Imagine it like this, you wake up too late and you miss a flight. You go into the machine and invert time to the point where you should have woken up and make the same flight you had originally missed.


All right! So we have dealt with what will happen to a person during time inversion. But what about objects particularly bullets? What happens during that testing the bullet sequence, when the protagonist seemingly wills a bullet into a gun? Why does he get hypothermia during the SAAB explosion? Why does Kat need to be put into inverted time, in order for her bullet wound to heal?

Basically entropy refers to the distribution of energy in all things over time. Some situations given in the video are a hot drink, cooling ice melting or a punctured tyre expelling air. In each one energy is being distributed from the thing that has the most energy to the thing that has less. So the hot drink loses heat to the cold air in order to balance the energy. The term low entropy refers to things that have a big concentration of energy. The term high entropy refers to things that have a balanced amount of energy that is spread out evenly. Hot drinks will always have a rising entropy over time as the drink cools and the energy spreads out.

In the case of inverted time in tenet where there is reverse entropy, the entropy of objects is also going backwards in time. However the idea of rising entropy over time still applies.

When the protagonist crashes the SAAB and it blows up in inverted time the entropy of the explosion is reversed. The explosion begins cold and draws heat from its environment to heat it up. In normal time the highest temperature of an explosion is right at the start. In inverted time the start has the lowest temperature which is why the protagonist gets hypothermia.

The bullets function in the same way. A normal bullet in normal time moves forwards and loses heat over time after ignition. An inverted bullet shot in inverted time will move forwards but start cold on ignition and gain heat over time. An inverted bullet shot in normal time will move backwards starting cold and gaining heat because it has had its entropy reversed.

The tricky part comes in how these inverted bullets affect surfaces and bodies. In Kat’s case she is kidnapped by an inverted Sata while she is not inverted. She is taken to the inverted side of the turnstile machine and shot from Sata’s inverted point of view. He shoots Kat and the bullet moves forwards through her and hits the glass. From the protagonist and Kat’s point of view a bullet goes backwards through the glass through her and back into Sata’s gun. For the solution to her wound to be that she needs to invert then the act of shooting her with an inverted bullet must mean that the bullet reversed the entropy of the things it touched inside her. Her wound is essentially not healing over time but getting worse. When she is put through to inverted time her entropy is put back to normal so the wound heals.

The main question i have is how wide is the radius of effect that an inverted object has on a non-inverted one? It likely depends on the energy distribution and how much has been put out of balance. In other words how far is the ripple of reversed entropy? It kind of makes sense. However in the case of the inverted bullets in the wall scene with Kermit’s posies character things don’t make as much sense.

When a gun is shot the bullet is expelled from the barrel via the action of a finger pulling the trigger. How then does pulling the trigger cause a bullet to move back into the barrel? How does the bullet an inanimate object know it is meant to be there? For this i actually could not find a concrete answer.

Some people speculate that if you look at the timeline of events from a deterministic point of view then that bullet belongs in that gun. And it is stuck in the wall waiting for someone to pull the trigger and bring it back to the barrel. It just doesn’t make sense to me in terms of how the bullet got there in the first place. Someone must have shot that bullet into the wall in inverted time the wall was retrieved in normal time and the bullets are still inverted within it.

The entropy rules apply so the bullet in the wall should be heating up in anticipation for being unshot. What is the time frame for this? How long does it continue to heat up for in anticipation for being on a shot? Did the protagonist from the future shoot the wall in inverted time only to have himself un-shooted in the scene we are watching? This is perhaps a plot hole that i just need to let go of and take the deterministic approach so i can sleep better at night.


On to the timeline of the film what happens in what order? I have decided to make a whole other article about this because there are a lot of details in the plot worth mentioning that make other moments in the film make sense?


Outside of the timeline of the film we have the timeline of the universe. We learn that in the future the world is in some sort of climate change crisis that is bordering on an apocalypse. In that world these turn style machines have been created to invert time. A scientist has developed an algorithm that will allow for the whole world’s time to be inverted and fearing the magnitude of her creation. She splits up the algorithm and hides it in the past in the pieces that we see in the film.

The future we aren’t sure who exactly decide, that they need to find the algorithm and revert the world’s time in order to destroy the past generations who first caused the climate change crisis.

They do this by sending pieces of information about how to find the algorithm as well as presumably instructions on how to build the turnstile machines to Sata. We see a flashback of him getting his first instructions as a young man in Ukraine who has volunteered to find plutonium but instead uncovers the first piece of the algorithm.

The biggest question this raises is how does destroying the past mean the future is better off. As discussed time inversion is not time travel there are no alternate timelines or realities. It appears then that the future’s plan is based on paradoxical beliefs. If killing the people living in the past doesn’t mean the people in the future disappear. Then how can destroying the past planet mean the future’s climate change crisis is somehow resolved?

It took me a lot of reading and a lot of time to come up with some sort of theory as to a solution to this. Here it is. Imagine you’re a member of the future generation living in the climate apocalypse. If the plan succeeds in the past planet namely the people are destroyed. The environment will have a chance to start anew and recover from the damage done by humanity. The future generation will then be able to use their inversion technology to invert time. And to get to the point after the past planet is destroyed and live in a world that is now recovering.

They are essentially hitting a reset switch on the planet in order to start again and prevent the climate change crisis that they experience the first time around. This is similar to my example of getting on the flight that you originally missed.

Another question i had when watching the film is, why does Sata’s death mean the end of the world? At first i thought the two things are inexorably linked, that for the world to end Sata must die.  Then he dies and the world is saved anyway. It seems his death was just the most villainous way he could kick-start the apocalypse. The algorithm/ bomb that was buried was ready and he could have just died with everyone else. Instead of that he takes his own life in some final act of pure bad kindness.


Nolan certainly has not made this easy. So i hope this video has cleared up at least some of the questions you had when watching this complicated film. Many of the things i have discussed have different explanations, interpretations and still suffer from a great deal of paradox.

It require definite suspension of disbelief, regardless i have enjoyed researching, theorizing, and beginning to wrap my head around this film and its concept. If anything doesn’t make sense call me out on it. There’s still a lot of discussion to be had. So head to the comment section and let’s all help each other figure this out collectively.

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