See this is where it gets complicated. If we go by standard physics, if you repeat a test with the exact same parameters, you'll get the same result.

The issue is quantum mechanics, and it's been a while since I studied this, so I'm very rusty on this subject and will need someone else to fill in here. It was a complicated subject back then, even more so after 15 years of not studying it.

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they wouldnt happen in the same order because quantum mechanics but if the universe were infinite then eventually every configuration of atoms would exist again

At first, yes, if things are identical. Then changes would accumulate, thanks to the consequences of randomly different events at the subatomic level. Opinions vary on things like whether there's any kind of universal inertia that would tend to drag events back toward some particular path.

Depends on where it occurs, if it happens on earth or anywhere near this universe, there’ll be universal chaos. If it happens trillions of light years away from this universe’s boundaries then well not much but double everything

Well, no - not according to quantum mechanics.

Unless you view all quantum “worlds” as equally valid. Then, all of them “happen” each time

Not really. You can have an infinite universe, but still have no stars shaped as a pyramid for example.

well you dont have stars shaped like pyramids in this universe either so im pretty sure this proves that youre a hamster after all

We don't know.

Quantum physics seems to suggest that all interactions are probabilistic. If that's strictly true, and the outcomes truly are random (seems to be) then no, things would definitely end up progressing differently.

But the apparent randomness of quantum physics doesn't sit well with people, so there's plenty of theories for how various unobservable mechanisms might restore causality. If one of those were true then yes, things would progress exactly the same from the same initial conditions.

Your answers so far help highlight the fact that we have absolutely no idea. Essentially this is a metaphysical and philosophical question and scientists are not particularly good at philosophy.

There is nothing intrinsically or philosophically different about quantum mechanics that would suggest it isn't deterministic, despite the assertions that this somehow answers your question. There are theories that support a determinist universe and theories that don't, but demonstrating which represents our reality is not a simple matter.

As humans that believe in free will we naturally reject the notion of determinism. That only hinders our understanding of the universe, because a scientific approach needs neutrality.

Naturally, when a scientific model came along that emphasised probability, entanglement and observation many people latched onto that as rejection of determinism. This could be seen as an unhelpful bias.

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