In physics, complex numbers were considered to be purely mathematical in nature.

Yes, but what few physicists realize is that the universe is a mathematical object and respond to mathematical functions. Max Tegmark has proposed a "mathematical Universe" for some time now. To me that sounds eminently reasonable and would explain why human symbolized mathematics are so effective in unraveling the properties and functions of all things in the Universe.

Physicists Prove That the Imaginary Part of Quantum Mechanics Really Exists!
By Faculty of Physics University of Warsaw on Apr 27, 2021

… The experiment verifying the role of complex numbers in quantum mechanics can be presented in the form of a game played by Alice and Bob with the participation of a master conducting the game. Using a device with lasers and crystals, the game master binds two photons into one of two quantum states, absolutely requiring the use of complex numbers to distinguish between them. Then, one photon is sent to Alice and the other to Bob. Each of them measures their photon and then communicates with the other to establish any existing correlations.

“Let’s assume Alice and Bob’s measurement results can only take on the values of 0 or 1. Alice sees a nonsensical sequence of 0s and 1s, as does Bob. However, if they communicate, they can establish links between the relevant measurements. If the game master sends them a correlated state, when one sees a result of 0, so will the other. If they receive an anti-correlated state, when Alice measures 0, Bob will have 1. By mutual agreement, Alice and Bob could distinguish our states, but only if their quantum nature was fundamentally complex,” says Dr. Streltsov.

An approach known as quantum resource theory was used for the theoretical description. The experiment itself with local discrimination between entangled two-photon states was carried out in the laboratory at Hefei using linear optics techniques. The quantum states prepared by the researchers turned out to be distinguishable, which proves that complex numbers are an integral, indelible part of quantum mechanics. …

Interesting video, thank you. I’ve got a slightly better idea of what this is about, and I’m grateful, though it still makes my head spin and fortunately I can live without it. Though that won’t stop me from peeking in and experiencing this stuff blow my mind, though not my nose.

‘‘Mathematics is the queen of the sciences and
number theory is the queen of mathematics.’’
/ Carl Friedrich Gauss /
All numbers , , , including imaginary numbers
Is imaginary number theory real?
If this is true, then it is possible that we live in metaphysical reality
‘’Imaginary numbers are a fine and wonderful refuge of the divine spirit,
almost an amphibian between being and non-being.’’
/ Gottfried Leibniz /
If this is true, then it is possible that in the beginning were imaginary
numbers, then complex and at end real numbers.

‘’One might think this means that imaginary numbers are just a mathematical
game having nothing to do with the real world. From the viewpoint of
positivist philosophy, however, one cannot determine what is real.
All one can do is find which mathematical models describe the universe
we live in. It turns out that a mathematical model involving imaginary time
predicts not only effects we have already observed but also effects we have
not been able to measure yet nevertheless believe in for other reasons.
So what is real and what is imaginary?
Is the distinction just in our minds?’’
/ Stephen Hawking //
===== …

Forgot who said it but it’s relevant: don’t mistake the description for the thing being described. Imaginary numbers are just tools for description. If physicists happen to need that tool in their current descriptions, big whoop. Doesn’t say much about the real world.

[quote=“citizenschallengev3, post:3, topic:7893”]
If you can make sense of that, more power to you!

It makes perfect sense if you consider that at the extreme fundamental “state”, there exist only three elementary “values”.

Elementary particle

In particle physics, an elementary particle or fundamental particle is a subatomic particle that is not composed of other particles.[1]: 1–3

Particles currently thought to be elementary include the fundamental fermions (quarks, leptons, antiquarks, and antileptons), which generally are “matter particles” and “antimatter particles”, as well as the fundamental bosons (gauge bosons and the Higgs boson), which generally are “force particles” that mediate interactions among fermions.[1]: 1–3 A particle containing two or more elementary particles is a composite particle.

Around 1980, an elementary particle’s status as indeed elementary – an ultimate constituent of substance – was mostly discarded for a more practical outlook,[1]: 1–3 embodied in particle physics’ Standard Model, what’s known as science’s most experimentally successful theory.[4][6]

Many elaborations upon and theories beyond the Standard Model, including the popular supersymmetry, double the number of elementary particles by hypothesizing that each known particle associates with a “shadow” partner far more massive,[7][8] although all such superpartners remain undiscovered.[6][9]

Meanwhile, an elementary boson mediating gravitation – the graviton – remains hypothetical.[1]: 1–3 Also, according to some hypotheses, spacetime is quantized, so within these hypotheses there probably exist “atoms” of space and time themselves.[10]

We call them particles, but they are not yet physical objects, they are fundamental “values”.

In nature the fundamental particle is atom
atom = electron + proton
electron is fermion an active particle force
proton is boson a passive particle
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I remember being shown how to graph an imaginary number once. I think it was high school math. It wasn’t on the test. I didn’t quite get it. I promptly forgot it