knightly the Sneptaur

All we can say is “that seems weird” but that’s not a scientific argument against it.

You say it diverges from reality but… how do you know that? No experiment has ever demonstrated this.

On the contrary, this breaks semi-classical gravity’s usage of quantum mechanics. The predictions the approximation makes are not compatible with our observations of how quantum mechanics works, and scientists are working on an experiment that can disprove the hypothesis. ( https://doi.org/10.1103/PhysRevLett.133.180201 )

Science is not falsifiability. Science is about continually updating our models to resolve contradictions between the theory and experimental practice. If there is no contradiction between the theory and experimental practice then there is no justification to update the model.

I’m afraid you’ve got that precisely backwards. Falsifiability is the core of science, as it is the method by which factually-deficient hypotheses are discarded. If there is no contradiction between the theory and experimental practice then either all false theories have been discarded or we have overlooked an experiment that could prove otherwise.

I have seen a mentality growing more popular these days which is that “fundamental physics hasn’t made progress in nearly a century.”

That’s distinctly false. The Higgs Boson was only proposed in 1964 and wasn’t measured 'til just 13 years ago.

But my response to this is why should it make progress?

Because we still have falsifiable hypotheses to test.

Why have not encountered a contradiction between experimental practice and theory, so all this “research” into things like String Theory is just guesswork, there is no reason to expect it to actually go anywhere.

We have, actually. The list of unsolved problems in physics on Wikipedia is like 15 pages long and we’re developing new experiments to address those questions constantly.

There is no reason to assume the universe acts the way we’d like it to. Maybe the laws of physics really are just convoluted and break down at black holes.

Likewise, there’s no reason to assume that the universe is not acting the way we’d like it to except where contradicted by observable evidence. If the laws of physics can “break down” then they aren’t “laws”, merely approximations that are only accurate under a limited range of conditions. The fact that the universe continues to exist despite the flaws in our theories proves that there must be a set of rules which are applicable in all cases.

And if the rules can change, then our theories will have to be updated to describe those changes and the conditions where they occur.

To oversimplify with another example from the theory, assume that planet earth was in superposition between two states with a non-zero separation. Semi-classical gravity says the distribution of the gravity field would be split evenly between the two points, but observing such a state is impossible as it must decohere into 100% of the mass being either in one point or the other. It simply doesn’t make sense when we try to apply quantum maths to gravitationally-significant objects because gravity/spacetime isn’t a quantum field.

So yes, the predictions made by semi-classical gravity diverge from reality when faced with extreme masses, but that theory was only ever intended to be an approximation. It is useful and consistent with reality under certain ranges of conditions, but we shouldn’t jump to the conclusion that physics breaks from all known fundamentals in the presence of large masses when the simpler answer is that this is a case where the approximation is wrong. A more complete theory will be able to accurately explain physics across a wider range of conditions without requiring the untestable assumption that there are places where the rules don’t apply. We’ve got a good reason to believe that the rules of physics don’t change in the fact that no matter where we look the rules seem to always have been the same and all prior divergences from the model could be explained by better models.

The problem in physics is that we have two models that describe reality with absurd mathematical precision at different scales but which seem to be fundamentally irreconcilable. But we know they must be, because reality has to be assumed to be consistent with itself.

It’s fundamentally a product of one of our most basic assumptions, that the laws of physics don’t change.

When the laws of physics don’t change, symmetries arise in the math used to describe them, and each of these invariant symmetries corresponds to a law of conservation we can observe experimentally and an aspect of the universe it renders un-measurable.

Conservation of Momentum is a space-translation symmetry which makes it so that absolute position is unmeasurable, we can only tell where we are in relation to other things. Conservation of angular momentum is a rotation symmetry that does the same thing for direction. There’s no “center” to the universe and no “up” or “down” without something to stand on for context, and no experiment we could possibly design can prove otherwise.

Conservation of energy (and therefore mass) arises out of time-translation symmetries. There’s no way we can distinguish a particular moment in time from any other without setting a relative “time zero” for comparison, and no possible clock we can build that could be 100% accurate. We have to account for the different rate of time in the atomic clocks in our GPS satellites due to their relative velocity to us on the ground, but the lack of absolute time precision means it can only ever provide an estimate with some range of error.

Exactly how the relativity of spacetime implies a universe with conservation of information would require a lot of math, and a new description of spacetime that breaks these conservation laws would have to explain why it “seems to” adhere to them in all the ways we’ve tested our reality so far.

The other alternative is that the quantum information is somehow converted to some value of the black hole’s measurable properties; charge, mass, and spin. We know that isn’t the case because the values for these that we can infer from observation are consistent rather than growing faster than expected.

The problem is that it’d be like if matter and energy could just disappear. Black holes would be exclusively tiny, as soon as one formed it’d start vanishing anything that crossed it’s event horizon rather than growing, so galaxies could never have formed as their cores would just shrink away as soon as they got too dense.

Black holes are regions of space where information density hits the upper limits allowed by physics. Add more information to it, and the event horizon expands proportionally to what was added. With that in hindsight, it seems rather obvious that the boundary of the event horizon could encode the information once thought to be lost to the black hole inside.

Also: The Lagrangian mathematics they use for quantum physics can be used to describe universes like the one you talk about, and if you’re interested in things like that then I absolutely have to recommend some novels by the mathematician and science fiction author Greg Egan. It’s way easier to start grasping how weird the physics can get when you get a story from the perspective of people who live there:

The Orthogonal Trilogy (2011-2013) is set in a 4d universe where the passage of time is dependent on the direction of travel in space, about a generation ship launched on an anti-timewise loop back around to the near future to develop a solution to an impending apocalyptic crisis of energy creation at the quantum scale.

Dichronauts (2017) is a journey to the end of the world in a universe where time has two dimensions and life evolved as a symbiosis of two creatures that could each experience only one direction in time.

Schild’s Ladder (2002) is set in a distant future where an experiment gone awry creates a more stable form of vacuum, creating an event horizon that expands at half the speed of light. 600 years later, a ship studying the event horizon discovers that the complex geometry of the new space behind it harbors intelligent life at a much smaller scale, with their equivalent of microbes being built from the interactions of a veritable zoo of quantum fields rather than molecules and proteins.

Quarantine (1992) explores the copenhagen interpretation of quantum mechanics, set on a future earth where the technology to put the waveform of a human mind into superposition with reality was invented. The user could turn it on, then live all possible lives from that monent until the version of themselves that achieved the result they desired would turn it off and collapse reality back into a single state. This isn’t really possible for complicated physics reasons, but if it was then it’d enable seemingly impossible things to become true. The novel explores the consequences of such a future conflicting with the existence of alien species that evolved within superpositioned reality and can’t survive when it’s collapsed into a single unique state.

“Information” in the quantum sense refers to the waveform of the quantum system as a whole, which is kind of a weird thing to get one’s head around.

Even in the case of chaotic pendulums, there’s no theoretical principle that keeps us from observing and accounting for every particle and quanta of energy involved and using that to prove that the waveform of the entire pendulum is consistent with itself and the expected evolution from previous states.

But the event horizons of black holes seem to break that rule, because the waveforms of black holes can be described with just three properties; mass, charge, and spin. There didn’t seem to be “room” for them to encode all the waveforms of anything that falls inside until Stephen Hawking theorized that it could be saved in polarization states of the event horizon boundary and black holes would gradually radiate it away.

To oversimplify, “information” is a very specific thing in quantum physics. Classical physics has the rule that energy can change form but cannot either be created or destroyed.

Information works the same way in quantum physics, which makes black holes seem like a problem since their event horizons are inescapable and anything that falls inside is lost.