Does quantum mechanics mean that we are far behind in understanding the physical universe?

Question

Until a certain time, physicists were using Newtonian mechanics, and until this time they did not have much difficulty in solving problems with this method. After quantum mechanics was discovered in the early 20th century, people's understanding of the physical universe changed completely. However, efforts to understand ancient Newtonian mechanics have become more difficult and not a problem that can remain unsolved.

Quantum mechanics cannot be directly understood by an smart thing being at Newtonian mechanics. To understand quantum mechanics, then, this thing entity must be smarter. Perhaps there are different mechanics of physics than quantum mechanics, and we don't know if it exists.

What are the different mechanics in the universe for? I don't think the most likely reason is that smart things being can be simple enough to obtain physical substance. Is understanding quantum mechanics a vision that science considers correct or alternative?

Answer 1

There seem to me to be several misconceptions in your question. Quantum mechanics isn't a replacement for Newtonian- the two are different models of reality, with different realms of applicability. You cannot use Newtonian mechanics to model an atom, for example, but it can be a better tool than quantum mechanics for modelling macroscopic objects. Newtonian mechanics, while simpler conceptually than quantum mechanics, isn't necessarily simpler in practice. Some quantum mechanical calculations are simpler than some Newtonian calculations and vice versa. It would be wrong to say that quantum mechanics changed our understanding of the Universe 'completely'- much of what we know about the Universe can be modelled very successfully with Newtonian mechanics, and over very large scales relativity is the dominant theory. Using quantum theory, classical physics and general relativity, we can explain a very wide range of natural phenomena and model them very precisely. The problem is that the three theories do not dovetail well, and have conflicting conceptual foundations, so we are lacking a consistent theoretical framework that explains reality at all scales. I would say that we have a much better understanding of the Universe than we had 150 years ago, and that is because of quantum mechanics not in spite of it. Are we still a long way from understanding the Universe completely? Who knows. We might find some breakthrough insight that allows the puzzle to come together quickly, or we might find the we peel away one layer of complexity to find a series of layers underneath. One problem that we do face, however, is that the testing of new theories might present technical challenges that we are simply unable to overcome.

Answer 2

Just to add one further aspect to the answer of @MarcoOcram. My answer refers only to your title question:

Since about one hundred years quantum mechanics teaches us the hard lesson to dismiss the premisses of our all-day experience when entering into the micro world.

All-day experience is what became our second nature from living in the world of middle dimensions concerning length, time, mass, the so called “meso-cosmos”. Newtonian mechanics meets our imagination that material objects behave like billiard balls - at least we got used to this conception.

The micro-cosmo is different and invalidates our established conceptions. E.g., the conception that all observables of a particle have a value, not depending on whether we observe the position, the velocity or the energy of the particle or whether we do not make an observation.

This premisse has to be abandoned according to one of the influential interpretations of the theory: If an electron has been observed at point A and later at point B, then we must not assume that the electron follows a particular path from A to B in the time between the two observations. The concept of such a path is meaningless.

It is not an easy task to accommodate with such a theory. In this sense we have to improve our practice to think and become acquainted with the rules of the new paradigm.

But it’s us who have to accommodate with the answers nature gives to our questions. It’s not nature which must behave according to our extrapolations from meso-cosmos.

Answer 3

So, what do you think understanding is? In science, it generally means having models of the world that make correct predictions.

The photoelectric effect, Brownian motion, and the ultraviolet-catastrophe, were problems that stood out at the beginning of the last century which were explained. Plus many more things, like doped semiconductors, and superconduction. We have models for those that work, so we say we understand them. And the anomolous orbit of Mercury was explained by General Relativity.

We still have substantial outstanding problems, like dark matter and energy, the proton radius puzzle, the inside of blackhole event horizons and how Hawking radiation might preserve conservation of information, which Unruh radiation exists, whether entanglement means wormholes (ER = RPR), and many more. Eg List of unsolved problems in physics. We can't know which might be the foundations of a new model, of new physics, until it happens.

Two things to understand about quantum physics. Uncertainty is an inevitable result of looking at systems where taking a measurement even with the smallest/lightest probe will disturb the system. And that fundamental particles can be literally indistinguishable, which has real-world consequences in Bose-Einstein and Fermi-Dirac statistics which govern bosons and fermions respectively. This is different to say a dice or coins, where we just choose to ignore differences. Like a blackhole, we only ha e certain limited 'handles' on them, and that can help us understand otherwise baffling behaviour like the Stern-Gerlach experiment.

What is missing? The Measurement Problem, or interpretations of quantum mechanics, is unresolved, but is usually argued to be for philosophy not physics because the proposals seem unfalsifiable. What governs the quantum coherence limit is the subject of intense interest for quantum computing which depends on increasing it. Possibly it's micro-scale gravity effects disturbing the system, and Bose-Einstein condensates in orbit or on the moon might identify that. And quantum-gravity, large masses at small scales.

Quantum Field Theory and the Standard Model are giant keaps forward in our understanding. That they have helped expose the scale of our ignorance, like about dark matter and dark energy, is part of that progress.