How long were the bullet holes present in the glass from the non-inverted perspective?

Question

In the first half of Tenet, there is a scene where The Protagonist and Neil break into Freeport and find a glass wall with bullet holes (could only find a good photo with Christopher Nolan in it):

In the next scene, we find out that these bullet holes were caused by an inverted armed man entering the room (exiting the room from their perspective) and reverse-shooting the glass, which removes the bullet holes from the future-facing perspective. This all makes sense, but raises a question: how long were the bullet holes there in the first place? Were they in place as soon as the glass was installed, possibly years ago? Or even back when the glass was manufactured?

Answer 1

Questions like this do touch the nerve of the film's logical consistency.

In our normal, non-inverted timeflow, when you shoot a wall/glass, the resulting hole remains in it indefinitely and only gets worse with time. It will eventually get buried/destroyed after the building gets demolished. The hole will not magically self-heal / disappear.

In Tenet's inverted timeflow the laws of physics are deemed to be all the same. It's just the entropy/time that flows in the opposite direction. So, there should be no reasons to presume that the behaviour of a bullet hole shot by an inverted round would be any different in its timeflow. Like with a normal bullet hole, it should be worsening with its time going forwards (ours backwards), not self-healing.

What that means is that, logically, the hole got formed it its worst/oldest state in the glass right when it was solidifying from liquid silica at the glass factory. Yes it was essentially a factory-made flaw/defect which, for whatever reasons, was ignored by the factory's QA, glass supply chain, the builders and the Freeport vault staff all the way along. Think they all were on Tenet's payroll or whatever.

Like Barbara said to the Protagonist: "Don't try to understand it. Feel it". I don't think Christopher Nolan intended to make it completely logically consistent and making sense. It's just supposed to be a "wow" to impress the majority of viewers who will simply say "Ingenious! Let's go see it again, maybe we'll understand some more".

Answer 2

The in-universe explanation is that traces of all interactions between inverted and regular objects were always present in our universe. What has happened - happened.

So as soon as the glass was made it was already cracked, although the cracks were microscopic. Then they would grow larger and larger until they form a complete bullet hole at some time prior to the event.

All this is clearly explained during the inverted trip to Oslo.

1. When the inverted Protagonist, Neil and Cat board the container, it is specifically shown that the Protagonist's right biceps is bothering him.
2. During the trip, judging by Protagonist's emotions, it starts bothering him even more.
3. When they arrive at Oslo airport, it is bothering him so much that Protagonist rolls up the sleeve and looks at his arm. We can see that there is some kind of a bruise on his right biceps.
4. Just a few seconds prior to leaving the container, Neil sees blood dripping from Protagonist's right arm, but they have no time to investigate.
5. From that moment, it is about 20 minutes give or take until he gets stabbed exactly in his right biceps.

Answer 3

Yes, those bullet holes have always been there since the glass was manufactured. From the inverted perspective, the building is eventually dismantled and the glass is driven backwards in a truck back to a factory then is melted down into sand.

According to the principle of "whatever happened, happened", the fact that the bullet holes are there, it must mean that they were installed that way. If there was, for example, a fastidious contractor who would have noticed the holes and thrown it out, then the original shots could not have ever happened. This is similar to how they looked through the window to see if their inverted selves were going into the turnstile. If you decided not to go into the turnstile, then you wouldn't see your inverted self going into the turnstile either. Or similarly with the inverted rounds jumping up into the characters' hands. It seems implausible but the construction of the room is not shown to the audience and you could come up with any explanation for why those holes are there.

There's a great novelette called "The Merchant and the Alchemist's Gate" by Ted Chiang:

In it, a character has a hoop where one side is delayed relative to the other. If you put your hand in one side in you see your hand come out the other side a minute later. If you put your hand in the other side your hand comes out the other side a minute earlier. If you see your hand come out that side of hoop you will inevitably be putting your hand in the other side in one minute. If you decide you would not do that then your hand wouldn't have shown up in the first place.

If you manage to shoot someone and the bullet is embedded in their body, then you follow that bullet back to the person's birth, eventually that bullet is too big to fit inside that person. Either you have a paradox since the bullet is going to kill that person before they're old enough to get shot by that bullet (and one way to look at it is that the paradox could not happen therefore it's impossible for the original shooting event to have occurred), or the bullet falls out at some point without killing the person. So in the forward perspective you have a child walking along when a bullet suddenly jumps up off the ground and embeds itself in their body.