How Tenet’s Time Inversion Works

Tenet John David Washington split in two directions

Warning: we’re about to spoil a lot of Tenet**, particularly how the time travel/time inversion works in the film, in this rundown you’re about to read. If you haven’t seen the film yet, invert your way back to before you saw this headline, and go about your business. Catch up with us once you’ve seen the movie, as you don’t want to spoil one second of the story.**

Well now: this week has taken a most interesting turn, hasn’t it? If you’re reading this, future CinemaBlend picked up on the fact that we were planning on doing a rundown on About Time’s time travel, in the week that Tenet was going to be released. But then, thanks to posterity and all that, our plans were changed, and I think Future Mike had something to do with this. Thanks to directions he sent me, I was able to not only see Tenet in a theater near me, I can now break down how time inversion works in the Christopher Nolan film.

For those of you who were expecting more traditional time travel fun, don’t you fret. About Time’s day will come, but for now it’s in the cupboard, traveling to next week. And don’t worry, this Tenet explanation will play in real time, with no pieces inverted and running backwards. We’ll explain that in a moment, but for now, this is your last and final warning before we step into the ways of time inversion, and how it works in Tenet.

Tenet John David Washington and Robert Pattinson touring a vault

The Time Inversion In Tenet

After nearly giving his life during a covert operation at an opera house, The Protagonist (John David Washington) finds himself embroiled in the fight to stop a war with the future thanks to an organization called Tenet. With the help of a compatriot named Neil (Robert Pattinson,) the race is on to figure out the threat, and neutralize it before those who would do us harm from the future can counter.

Who's Using Time Inversion

Various persons from both the present day and future of Tenet’s timeline are using inversion for their own means. Most notably, we see The Protagonist and Neil using it to fight for the present as part of Tenet, a covert organization that engages in time inversion operations. Meanwhile, villainous oligarch Sator (Kenneth Branagh) uses time inversion to help those who would do us harm from the future.

The Purpose Of Time Inversion

At some point in the future, “The Algorithm” is invented, the key to time inversion on a global scale. Designed as retaliation for the past’s reckless allowance of global warming, the future decides they want to invert the entire world, which would basically reverse the flow of time and send humanity on a reverse course through history.

Tenet The Turnstile

How Time Inversion Happens In Tenet

On a wider scale, Tenet would theoretically use The Algorithm to invert the whole of time on Earth. However, in terms of the more immediate usage of inversion, a much simpler method is used, known as a Turnstile. Brace yourself, because this is where the fun of Tenet really kicks in, thanks to two rooms: one red and one blue.

A Turnstile is a facility that uses those color coded rooms to invert and revert any traveler’s path through time. Using the red room inverts the person and objects that are sent through, which puts said person/objects onto the blue side of the continuum. Through that process, people and objects now move in reverse to those observing them on the other side.

If you want to revert a person or object into the proper flow of time, you must bring them to a Turnstile, so that they can enter the blue room, and revert to the regular flow of time, exiting through the red room. You can’t just jump any place, any time in the world of Tenet: merely backwards and forwards from the moment you are traveling.

While there are no technical specs on the Turnstile, the power of nuclear energy is mentioned as the source of power used in Tenet’s mode of travel travel. Using a nuclear reaction, inverse radiation flips an object’s particular motion in the timeline, as well as giving off a signature that can be picked up by those evaluating inverted objects and people. So use enough nuclear energy, courtesy of the ever handy Turnstile, and boom – you’re running backwards through time.

Which leads to one crucial plot point: everything you do on the other side of the time divide is inverted – but time isn’t. Think of time and space as a cassette tape, with two different sides of information playing out at once. If you were able to play both sides at once, one would sound normal, while the other would be playing backwards. Using a Turnstile is basically flipping a person or object from Side A to Side B, with the other side supposedly running in the reverse direction.

Side A: Forward Flowing Time

On this side of Tenet's time stream, everything plays out normally. You walk normally, talk normally and everything is as it should be. However, since both sides of this temporal cassette are playing at the same time, you're seeing Side B's actions in reverse. While everything is happening at the same time and place, respectively, things look backwards. That's an easy tell to spot someone who's not supposed to be there, and it also plays out in the important moment when Sator captures Kat and shoots her in the inverted side of Tenet's story. To The Protagonist, the event happens in reverse, which prompts him to cross through to Side B, in hopes of saving Kat, so that she could prevent Sator from obtaining the last piece of The Algorithm.

Side B: Reverse Flowing Time

On Side B, it's Side A that looks like it's happening in reverse, but in actuality it's you that's inverted. Which brings up the reason those oxygen masks are needed, as once you've inverted, your entire body exists as an inverted machine. As such, the inverted membrane of your lungs cannot handle standard air, and you'll need to reverted to breath normally. 

Tenet sums this up rather neatly in a piece of dialogue: “You’re inverted, the world isn’t.” So when The Protagonist saves Kat in inverted time, this creates the necessity to bring her to the Oslo Freeport to revert her back to normal. Not only does she not need the telling oxygen mask that would out her as another inverted version of herself, but she'd be able to speak normally. As such, the now reverted Kat 2.0 is now able to go to Vietnam, sans oxygen mask, and try to stop Sator from killing himself; while her original self goes on a trip with her son.

Tenet John David Washington wearing an oxygen mask

Can History Be Changed As A Result Of Time Inversion In Tenet?

Technically, history can’t be changed in the world of Tenet, all thanks to the concept of posterity. If something happens in the present and it’s documented somewhere, somehow, those in the future can monitor the results and try to prevent/alter the result. However, thanks to Tenet playing all the angles out in real time, just across two different sides of the same temporal cassette tape, the result is always present on the timeline. So while you think you’re merely listening to “Baby, One More Time,” the corresponding track on the other side of that Britney Spears cassette is playing at the same time, in reverse, observable to everyone in the room.

Both in the Oslo Freeport incident, where the 747 full of gold crashes into the secret art vault Sator uses to hide his goodies, and the freeway chase sequence where Sator uses his goon’s recounting of events to get his way, The Protagonist’s inverted form is on hand to supposedly get in the way of events playing out in normal time. He knows how things are supposed to go, because he sees them play out that way the first time.

This plays into the Grandfather Paradox, something that Neil mentions earlier in the film. If someone decides to try and take action to prevent the past, the ultimate outcome that results is the same as before you took action. If someone travels back in time to kill their grandfather, it would prevent their birth, but in turn prevent them from traveling back in time, which is a zero sum game.

Almost immediately, thanks to The Protagonist knowing the markers he has to hit in his own personal timeline, those changes are seen in real time once he inverts himself. Since there’s technically two streams of time existing simultaneously, just flowing in different directions, events occur as they are seen. The same can be said about Elizabeth Debicki's character, Kat, who recounts a story about seeing her husband on his yacht with another woman, only to realize that another version of her was that other woman.

Which means, Tenet is yet another predestination paradox, as everything falls into place the way that it’s supposed to. With events like The Protagonist’s fight with his inverted self at the Oslo Freeport, and the green BMW getting in the way of the handoff between The Protagonist and Sator, it looks like everything is happening instantaneously. But in the subjective viewpoint of The Protagonist’s journey through inverted time, it feels like something’s changing.

Tenet Robert Pattinson and John David Washington stand apart on the roof

What Are The Consequences Of Time Inversion In Tenet?

Ultimately, if The Algorithm’s full purpose was fulfilled, the whole of history could have run in reverse in Tenet’s universe. But thanks to Neil and The Protagonist’s efforts, and the eventual revelation that Tenet would be founded in the future by The Protagonist himself, the actions that the future took to alter the past have been cancelled out. Again, it looks like things have changed subjectively, but the sum total of events even out to a zero sum game.

The Future Of Neil

Doctor Who fans, you know exactly where this story’s going when you get to the end of Tenet. As indicated by the red thread in his backpack, Neil is the inverted corpse that helps save The Protagonist in the nick of time, as Sator’s goon is about to shoot him. With Neil sacrificing his life, The Protagonist is able to help Ives (Aaron Taylor Johnson) retrieve The Algorithm, just in time for the three of them to disassemble it and scatter it so it can never be used. Neil knows this, because he’s been briefed on the mission, by none other than the founder of Tenet… The Protagonist. His efforts in the future prevent a massive catastrophe, putting himself on a very specific path as well.

The Future Of The Protagonist

While Neil’s history with Tenet is at an end, The Protagonist’s story is just starting. As Neil has been briefed and acting on behalf of Tenet for some time now, he’s just shown his future boss the ropes on how to get it all done. Now, The Protagonist will spend the rest of his life tying up loose ends, and monitoring posterity to make sure that nothing hinky corrupts the timeline. Eventually, he’ll encounter Neil again, giving him his orders to save the past from the future yet again.

Tenet Robert Pattinson gets ready to pour some coffee

Time To Tie Up Loose Ends

So there you have it! Everything you wanted to know about Tenet’s time inversion, but haven’t had the chance to ask after, has officially been completed! I hope that our present audience, as well as Future CinemaBlend and Future Mike are pleased with the work we’ve done here. So without further ado, we will be covering About Time’s time travel, unless there’s some sort of crazy future emergency that details out present selves yet again.

Don’t let that stop you from sending in your suggestions though, as we’ll be running through every time travel story we can get our hands on. After all, the fun in these write ups comes from showing you from here to there in the now and then! So until next time, have a pleasant inversion, and remember your mask – be it oxygen or protective – when taking your journey!

Mike Reyes
Senior Movies Contributor

CinemaBlend's James Bond (expert). Also versed in Large Scale Aggressors, time travel, and Guillermo del Toro. He fights for The User.