Calculate but don’t shut up
aeon.co
aeon.co
Universe is not made of little balls.
Particles ARE their wave functions. Nothing less, nothing more.
Sometimes those two wavevy objects interact as if two little balls bounced at one point, but that's only "accidental" similarity between the way they exchange the energy (and momentum) and the way macroscopic balls exchange the energy. Yes. It's not deterministic, what will be the parameters of that interaction. At what spot exactly will it seem to have happened, how much energy will be exchanged and how will it reshape and redirect the inital wavy objects. But thanks to our math we can predict likelyhood of everything that might happen.
Well, not exactly accidental because the way macroscopic balls bounce comes out of the exchange of energy by microscopic wavy objects bound tightly together. Same way that macroscopic magnetic interactions come from microscopic interactions of many thightly bound and oriented particles.
Wave functions never collapse into little balls, they just interact as if two balls bounced, and they get reshaped to be smaller and less fuzzy, but that's it. You can easily spread them back by interacting with them again in a different manner.
There's no such thing as a measurement. Measurement is just interaction with large rigidly bound chunk of matter which reshapes the measured particle because any interaction always reshapes.
There's really no reason to think that particles are little balls or matrial points or anything similar.
Initially people thought that because of photoelectric effect. That energy is transferred in quanta. But it's not hard to imagine this as purely fuzzy, wavy phenomenon where electrons are stuck around the nucleus in a sort of "harmonic" and they can't jump up to the place half-way to their next more energetic harmonic. Check out how orbitals look (and Chladni figures) if what I wrote seems unclear.
If you know any reason to think particles are little pointlike objects please let me known because I couldn't find any.
> Quantum mechanics is intrinsically indeterministic.
> The correspondence principle: in the appropriate limit, quantum theory comes to resemble classical physics and reproduces the classical predictions. The Born rule: the wave function of a system yields probabilities for the outcomes of measurements upon that system.
> Complementarity: certain properties cannot be jointly defined for the same system at the same time. In order to talk about a specific property of a system, that system must be considered within the context of a specific laboratory arrangement. Observable quantities corresponding to mutually exclusive laboratory arrangements cannot be predicted together, but considering multiple such mutually exclusive experiments is necessary to characterize a system.
These are universally accepted facts now (it would be silly for any physical theory to contradict the second one). Even a kind of "out there" theory like many worlds theory (https://en.wikipedia.org/wiki/Many-worlds_interpretation) would not dispute these facts (it just reinterprets the indeterminism of quantum mechanics as taking different "branches" in a multiverse). The "interpretation" part of it is a bit historical, as no "interpretation" should contradict these facts (a la Bell's theorem).
Edit: As a philosophy, any "interpretation" built off of these facts is cool, but until you calculate anything, it's essentially useless as a physical theory.
In many worlds, collapse is a subjective and approximate phenomena, not something fundamental.
That's perhaps the Narcissistic Many Worlds interpretation. Another way of thinking about Many Worlds is that there's only one universe, in which: after measuring a particle in a superposition of two states, you are now in a superposition of two states. Each of the superimposed you states thinks your instrument measured a single clear result.
The wavefunction of the universe goes on propagating as usual, including both of the superimposed yous, but within each of the superimposed states, that you thinks that it has witnessed wavefunction collapse.
The measurement results are mathematically necessary. The Copenhagen interpretation, that this means there is a physical collapse in the wavefunction, is not.
> To me, it seems that other theories are just disputing what the "collapse" fundamentally means.
If you substitute "collapse" for "measurement" this is pretty much true. What else could "different interpretations of a theory" mean?
One is about what actually happens. This contains Shrodinger equation and similar things.
The other is about what results will we get if we poke the particles with macroscopic objects disturbing them beyond recognition. That's the all math where the word "measurement" is used.
Somehow we think the science of what happens to a frog when you poke it with a knife is a part of zoology. It's important, it might be even more important than zoology, but that's a different domain of science.
The way I see it, other interpretations have no purpose except to reconcile what we observe on small scales with incorrect statements such as "electron is a tiny ball", or "electron is a wave in the three-dimensional space", or "an observer which are themselves composed of quantum mechanical particles is independent of the system, and exerts free will to choose measurements while the observed system is purely deterministic".
The uncertainty principle says you can never know both the location and the momentum of a particle. This stems from the fact that because spacetime is the way it is, knowing either one of those things requires having made a measurement, which by its nature, prevents the measurement of the other thing.
The act of measurement is independent of there being an "observer" in the sense of some sort of intelligence or consciousness. The use of the word observer in early communications led to all sorts of woowoo garbage later on.
More recent interpretations suggest that instead of the requirement that particles be in a singular state, perhaps their fundamental nature is probabilistic. The wave function is the thing, the particle at a singular place and time is an illusion. There's no need for wave functions to collapse, and that view seems to be an imposition of human scale expectations on the quantum universe. An electron exists as a point cloud - what we observe is an artifact of the observation, not a fundamental property of the particle.
I am fond of the "universe is made of math" view suggested by Max Tegmark.
https://en.m.wikipedia.org/wiki/Mathematical_universe_hypoth...
We did not evolve to perceive the universe as it is. We have limitations built into the mechanics of our existence that have to be overcome and understood at every level of abstraction that our tools of reason and technology provide. The more degrees of separation between our evolved tools of perception and extrapolated and abstracted concepts about how the universe works, the more it will diverge from human experience and seem to be "weird." When we try to make weird things make sense to our monkey brains, we introduce a bias that can lead us astray.
https://www.quantamagazine.org/where-quantum-probability-com...
The Copenhagen interpretation is an attempt to make monkey sense of something that has no direct input into any of our tools of perception.
The Everett interpretation recognizes that any observation has to include the quantum states of the mechanism doing the measuring, the environment in which the mechanism resides, and the entities in proximity to the environment, and planet, solar system, galaxy, and universe - that by existing inside the universe, you are subject to the influence of everything else that exists within the universe, and that quantum states are one of the proxies we have for predicting the results of interactions between the states.
Stephen Hawking was an Everettian, and discounted the Copenhagen interpretation.
https://en.wikipedia.org/wiki/Many-worlds_interpretation
Tldr; there's no such consensus on Copenhagen, and the many worlds interpretation is gaining precedence, because it's got the most rigorous basis in mathematics.
Scientific Realism holds that in some sense scientific theories approximate the world, not just in what the experiments observe, but also in the content of their explanations (precisely, you gain knowledge not just about observables, but also non-observables: things that the theory requires to be true, but can't show). The article ascribes this view to Einstein, who presumably thought that there was a such thing as space-time, and it does actually curve under the influence of mass - despite only seeing things that are explained by the curvature, and not the curvature, or the space-time, itself.
The article then goes on to say that the anti-realist approach (dominated by not-undeserving practical concerns and application) focuses on computation: the mathematics is good so long as it gets the right answers in the end, and the end justifies the means. Therefore, it doesn't matter what contrivances must be dealt with in-between: if you get a better prediction, or can do a new exciting thing, then that was always the aim.
Thus, I read the article as advocating a stepping back from this view: it blames this focus on sheer mathematical sophistication as the route to truth as the source of profound disinterest in philosophy by physicists (it is important to note that I think that aeon is a philosophy newsletter!). Earlier and contemporary physicists (prominently, Einstein) had an interest in not just what their theories produced, but what they explained the world to be, and the article decries the modern lack of this.
I recommend the SEP article on scientific realism, which is dense but on a brief reading gives enough of the context to recognise the article. https://plato.stanford.edu/entries/scientific-realism/ (Although it is even more philosophically focused).
NB. I'm not a physicist or philosopher either, so grains of salt! My only self-endorsement is that I spent the last year reading a bit of philosophy, so perhaps I can be at least a stepping-stone to better resource.
So my take now is that as long as it works no one is questioning why or how it works. Which is what you'd expect scientists to be doing.
I've noticed that many of humanity's models try to simplify things into neat models and that results in either - many specific models, each focusing on a specific macro-behaviour - one statistical model which basically describes the underlying process as non-deterministic
Couple that with performance debugging 101: Measuring the performance of a function changes the performance of a function
(Fudamentally because you can't see without interacting, and sometimes that interaction creates weird results)
And the conclusion is that Quantum Mechanics is a statistical model of a complex hot path which we're trying to measure, so of course it's going to be weird and hard to so.