History Headscratchers / Tenet

** Do you remember the scene where Sator flees Ives and his men into the turnstyle and seems to disappear? The Protagonist asks where he went and Ives answers "into the past." If something enter a turnstyle they seem to disappear from the point of view of other people going forward in time, and [[JustForPun inversely]] if they enter the turnstyle while inverted, they seem to spring from nothing just like the Protagonist suddenly appeared to Neil and his older self in the Freeport. So, if someone were to put a rock in a turnstyle without going to they'd see the future version of the rock on the other side of the proving window when they arrive and it falling inside the turnstyle as they put it in and then it would seem to disappear.

** There's a rather interesting theory that [[spoiler:Neil is actually Kat's son. If that's the case, then The Protagonist could have watched over the boy as he grew up, befriended him once he was old enough, and formally recruited him into TENET when he was ready.]]

[[folder: Where do inverted objects spacially go?]]

[[folder: Kat being a loose end]]

[[folder: Sator's dead drops and the dual futures of inverted objects]]

[[folder: Inverting the world]]

** I’m not sure if you’re reading too much into it or not, but from the sound of things in the movie the people of the future want to invert the earth to collide it with the uninverted earth. Remember the conversation about Anhilation? Sounds like they want to go that plantwide, the second the earth is inverted it will occupy the same timespace as the earth moments before it was inverted. Which creates a paradox for those in the future, if the earth was destroyed in their past then how can they exist in their present?

[[folder: Freeport, Round 2]]

[[folder: Who Would Make &/ Use Such a Doomsday Weapon?]]

[[folder: The collected aftermath of the future war]]

[[folder: What actually arms the algorithm at the end?]]

** They were fighting against Sator's men. The troper writing this agrees the scene wasn't shot well, including not showing much or any enemies on camera (I understood the overall battle actions after a Youtube video, though this doesn't fix some other issues. Grr, missed opportunities there....but this isn't a review). They were trying to fight their way to the opening of the tunnel where the Algorithm was, clear Sator's people nearby, and get the main team/strike team/whatever you call them in without anyone noticing.

[[folder: Senses while inverted]]

[[folder: Taking a sledgehammer to the Algorithm]]

** The Turnstile wouldn't invert the rock unless you found the future, inverted version of the rock and put it in the blue side of the turnstile at the same time that you put the original rock into the red side, that's why Ives has to explain the proving window to the Protag. A good way to visualize it would be an object traveling in a given direction along a timeline before "bouncing" off of a turnstile to begin going in the opposite direction instead.

A formula translated into physical form that can't be copied or communicated. A black box with one function. So, besides separating the nine pieces, why not just take those pieces to separate corners of the world and take a sledgehammer to them? Smash them, cut them, melt them, and turn them into useless pieces of slag? Then you can hide what's left.

*** That is correct. Kat says her husband vanished that particular day, from which the Protagonist and Neil conclude he was directing the opera attack (it was on the same day) and indeed we see his helicopter leave the yacht when older!Kat arrives. Furthermore, the Sator she shoots is familiar with the Protagonist and recognizes the "despair or anger" line, proving he has already lived through the other events of the movie.

*** The big question is, how was it put into storage from it’s perspective? Invertedly (yes I’m using that) it was taken out of storage and put into the ground by Laura (assuming she found it) but Invertedly how did it get into storage? From normal time perspective, someone will have to take it out of storage and put it somewhere for it to end up returning to its point of origin in time.

*** But this makes no sense. If the injury is inflicted by a 'forwards' knife then the wound should be moving forwards on inverted!Protagonist up util he became inverted in the future at which point it wither disappears--or continues onto non-inverted!Protagonist. Either way he would have noticed at some point. If it is more about the direction of the injured party, then inverted!Protagonist would have no wound until he was stabbed from his perspective. As we see the wound running forwards and go with this explanation then why does the wound appear so suddenly? This also calls into question the nature of the inverted shot Kat suffers, the injury having a linear progression on her no matter which way she is going, though Protagonist is stabbed while inverted and by himself, maybe making his injury of a different nature. but in both cases the attacker is inverted (though the status of the weapons is unclear.)

** So, at the beginning of the scene, there are bullet holes in the glass pane. This troper thinks this is a mistake. From the point of view of the inverted!bullet: the bullet is fired from the gun / the bullet flies from the gun to the glass pane / the bullet strikes the glass pane / Due to impact, there is a hole in the glass pane / the bullet falls to the ground. From the point of view of the glass pane: the bullet un-falls from the ground and strikes the glass pane / Due to impact, there is a hole in the glass pane / the bullet flies from the glass pane to the gun / the bullet is un-fired. The bullet hole appears because of the impact between the bullet and the glass pane. But the glass pane is not inverted, therefore the hole (effect) should appear AFTER impact (cause). Therefore, at the beginning of the scene, the glass pane should be intact. The bullet holes should appear only after impact, later in the scene. This is not what happens in the movie. In the movie, the bullet holes exist before impact and disappear after impact.

* Here's a question that applies to most inversion (including the bullet in the demo), but most obviously to Sator's dead drops. At future time x, the dead drop is inverted and buried in Russia. For the dead drop, time runs opposite: (x-1), (x-2), so on. Up until time = 0 when it is unearthed by Sator, it has been in the ground. Now, (non-inverted) Sator and company unearth the dead drop at time = 0, and move it to the ship. So where is the dead drop at time = 1? time = 2? It is both in Sator's posession and buried which is a paradox.

** I hope to have a big write up of tenet physics at some point. For light, the way you see is that light hits a pigment molecule and excites it,,the excited molecule than sets off a nerve signal. To see using opposite time light, all that is needed is that the light can transfer energy to the pigment, once this happens, a nerve signal goes and you can see. A "flames cool you" situation is unlikely since less than excited pigments don't exist. The most likely hiccup is if "pigment excites magically like bullet damage appearing, than emits light" is the sequence. (So no actual answer, but the movie's physics isn't consistent) Most cameras use a similar "light excites something, which sends a signal" principle, so would work or not work along with eyes.

** For shooting the gun: the standard explanation is that he misses on purpose so that his forward self can't use it (Also why he disassembles it.) Presumably, he doesn't want to take a chance his normal self gets his hands on a loaded gun and fires, changing the timeline and injuring hmself. Outside the story, inverted gunshots and disassembly make obvious to the audience that gas mask man is inverted: a pure hand to hand fight wouldn't be so clear.

** A related question is why Neil uninverts after seeing Volkov instead of just telling the red team as planned,and maybe than heading into battle again to help them. Answer to the original headscratcher might be stable time loop, plus they know that they stopped Sator, so no point in possibly messing with timeline. Tenet selects agents willing to self sacrifice, making Neil's death more acceptable. (Obvious outside the movie answer is to create drama.)

** The physics of the movie is tricky and not consistent, or just weird, but it does make sense that in erted air wouldn't be breathable while inverted light and sound are fine. For air to be breathed, it has to be pushed into the lungs, have oxygen diffuse into the blood, diffuse into the cells, than chemically react with body stuff. All of these steps are tricky, breathing itself might be doable since expansion and contraction is symmetric, so oxygen would enter on the exhale, from the air's view the lungs are expanding. Diffusing is a straight up entropy based process, chemicals will spread out in their own time direction. An inverted person would see oxygen seeming to move from their cells into the air. What really messes up respiration is reacting inverted air with something else. Which way chemical reactions go is also straight up entropy based, so a chemical reaction between opposite time chemicals is hard to work out: whether it happens, how much energy it makes, whether that energy can be harvested. Quantum effects also come into play, which I don't understand well, it's possible a normal and reversed time atom or particles don't interact the same way same time ones do. A body might by able to use food and air inverted from itself with reactions happening in reverse and harvesting energy, but reverse time oxygen diffusing out of the body and doing who knows what inside is a good recipe for bad or weird things that don't produce usable energy.

** The physics of the movie is tricky and not consistent, or just weird, but it does make sense that in erted air wouldn't be breathable while inverted light and sound are fine. For air to be breathed, it has to be pushed into the lungs, have oxygen diffuse into the blood, diffuse into the cells, than chemically react with body stuff. All of these steps are tricky, breathing itself might be doable since expansion and contraction is symmetric, so Oxygen would enter on the exhale. Diffusing is tricky, the air from the person's view would be flowing out of their body. What really messed up respiration is reacting inverted air with something else. A chemical reaction between opposite time chicas is hard to work out: whether it happens, how much energy it makes, whether it can be harvested. A body might by able to use food and air inverted from itself with reactions happening in reverse and harvesting energy, but oxygen diffusing out of the body and doing who knows what inside is a good recipe for bad things.
*** Sound and light are simpler. Force and pressure seem to work done inverted, so sound works, the pressure wave pushes against ear components as normal, bit since the person is going backwards to he pressure pattern seems reversed and you have backwards sound. Light probably works, but could go either way. Vision works by a photon hitting a Chicago in the eye, being absorbed and exciting said chemical, than the excited chemical sets off a nerve signal. It might be an inverted person has the chemical get excited from nowhere and emit light, like the bullet holes/mirror/wound appearing from nothing. It is also possible that a nerve signal appears from nothing crating vision and moving towards the eye, or that the light seems to move backwards but still excited the eye and works normally from the person's view from there. Either way, they could see.

A formula translated into physical form that can't be copied or communicated. A black box with one function. So, besides separating the nine pieces, why not just take that those pieces to separate corners of the world and take a sledgehammer to them? Smash them, cut them, melt them, turn them into useless pieces of slag?

* So the writers wanted to look smart and include how you can't breathe air while inverted so you need a supply of inverted air but this is rather selective. If you continue this line of logic then an inverted person shouldn't be able to see as light is still moving forward and unable to hit their eyes for them to see anything. The same goes for sound, the soundwaves are still moving forwards. Maybe air is different for how it interacts with the body but an inverted person should be blind and deaf as well as sufocating.

*** There would be no literal 'merging'. Past Kat, who unknowingly saw her future self jump from the yacht, would eventually invert and become the Future Kat that jumps from the yacht, and presumably, Future Kat would step into Past Kat's place once Past Kat inverts, picking up where she left off, as it were.