If the ancient Greeks were left doing only arithmetic they would've never encounterd irrationals — TheMadFool
So geometry then injects just enough physical reality into the mathematical abstraction to raise the problem?
Zeno's paradoxes were another route into the same issue. As an object of the mathematical imagination, the number line claims to be both continuous yet also infinitely divided. That is a useful quality for modelling/measuring the world, but what way is it realistic?
I'm with Peirce and those who argue that reality is at root vague, and then this vagueness can be organised towards opposing dichotomous limits of being. So reality is organic rather than mechanical. It has to develop the counterfactuality attributed to rational structure.
When it comes to the number line, this means that it is neither continuous nor discrete in the absolute sense usually claimed. Instead, it is only relatively connected or divided. It can approach either of these claimed states "in the limit". But the limits are themselves unreached in actuality. It is only in the mathematical model that it is useful to think this way.
So mathematicians tend to want to treat the closest approach to these paired limits on possibility as being true actualities. The infinite and the infinitesimal are both real objects in the mathematical imagination. They stand for the concepts of the continuous and the discrete, the line and the point, being extremetised - boundaries states which can actually exist in categorical fashion.
But the alternative view - based on Peirce's organic logic of vagueness - is that the infinite and the infinitesimal are the two ends of a process of dichotomising. Each is yoked to the other in a reciprocal relation. Infinity = 1/infinitesimal, and infinitesimal = 1/infinity. So as quantities, each is formally quantified not in terms of what it is, but in terms of how little of its other it contains.
The rational numbers stand far enough back from the fray that it seems quite easy to treat a continuous line as an ordered series of points. As an object, it can paradoxically be the two things at once. But then as mathematicians go deeper, they have to keep expanding the notion of continuity to come up with a transcendent hierarchy of infinities. Likewise, the ability to cut the number line ever finer leads to a hierarchy of divisions. We encounter the infinite decimal expansions of the irrationals.
This maths is useful, so people believe in it. People get used to "taking the limit" and that allows them to knit together models of reality that marry dichotomies like lines vs curves. We can do calculus and other tricks. We can employ constants like pi, e and phi that are treated as exact values - even though they are at root vague values, being irrational numbers.
So there is no dispute the maths works. But the point is that it works by simplifying reality. It models the fact that reality arises in this symmetry-breaking, dichotomous fashion - the good old unity of opposites - but instead of treating the two halves of the deal as co-defining limits, it treats them as two categorical states of being.
A Peircean approach adds a further dimension to the picture - the organic and developmental one. It says at root is the vague. And so the infinite decimal expansion of an irrational value is another way of accepting this, without openly admitting it. We are happy to have the first four or five digits of pi. That is enough for almost all our practical purposes. The rest of the long line of digits can be allowed to disappear into the mists of the unknowable. We don't have to make a big metaphysical deal out of the fact we can never actually arrive at a final number. Instead, we create a metaphysics which claims that the infinite expansion actually exists ... in some Platonia.
But I am coming at this from the side of physics where vagueness might be a useful thing to be able to model and measure. And where the difference between a constant being produced by a closed symmetry operation, vs a constant reflecting an endlessly convergent series, seems like an important dichotomy to understand.
It isn't too much of a stretch then to posit there's something geometric about the irrationals. Helium - Sunnish; Irrationals - Geometric. — TheMadFool
I have no idea how you make that connection. Was that some other post?
No matter what you plug into that equation as the value of x, you will always miss out some points (incommensurable/noncomputable/transcendental numbers) i.e. the line will actually be discontinuous. — TheMadFool
Well, the more points you plot, the smoother the line will become. So as a construction, you are progressively limiting the possibility of the line turning rough, jagged or fractal inbetween the points you have so far plotted.
It depends which way round you want to view the situation. But the mathematical object appearing on the page is becoming both more a collection of points and more a continuous line at the same time.
So symmetry produces neat rational constants in your opinion? However, I maybe wrong of course, these values (spin and the other one whatever it is) don't show up as physical constants in Wikipedia. — TheMadFool
That is the idea I would explore.
The dimensionless physical constants of the Standard Model are made a fuss of because they seem to be arbitrary values. They are numbers that could have been anything as they don't seem to follow from some fundamental symmetry that would have to be enforce on any form of material being. They are irritatingly patternless as well as irrational as actual numbers.
On the other hand, values like quantum spin are well behaved because they fall directly out of symmetry principles. There is an exactness imposed on them in the way that resonances in a cavity must fall into countable whole numbers - the Pythagorean discovery of harmonics, the music of the spheres, which was the pleasant metaphysical surprise the ancient Greeks celebrated, alongside their disgust at finding numbers could also be irrational or matchingly discordant.
So if we really dig into the issue from the side of fundamental physics, I see three classes of constants.
There are the arbitrary numbers (dimensionless ratios of measured values) that give us things like the odd difference in mass between an up and down quark. Why does one weighs 2.01 megaelectron-volts, the other 4.79 (give or take current measurement error)? A theory of everything would want to find a way to calculate such values from first principles rather than have no good explanation at all.
Then there are the properties of particles that follow directly from closure of symmetry relations - things like the Lie groups or permutation symmetries that underpin gauge symmetry breaking. It is quite natural to see why these are rational numbers, being counts of transformations that leave things unchanged. A perfect triangle maps onto itself three times with every rotation. We are counting its resonant states. In the same way, quarks and leptons - as products of Platonic-strength symmetries, and indeed quantum harmonic oscillators - have no other choices, no possible intermediate states, as they are metaphorically, but effectively, like reverberations in fixed cavities.
The third class of constants are the magic triad of the Planck constants - c, G and h. Okun's cube shows how they anchor all of physical theory, and a theory of quantum gravity will finally unite all three values in the one fully relativised quantum field theory. As constants, these have measured values. But really, it makes just as much sense to set all their values to 1 as they are arranged to create a set of reciprocal equations. Each represents a different kind of physical limit - a limit on connection, curvature and certainty - and so are just absolutes. We can presume that like the gauge symmetries written into the Standard Model, they have no specific material value as they are just pure forms - the expression of pure relations, an ontological structure that would have to be the same for any universe with a self-organisingly "resonant" geometry.
So my overview is that the notion of a physical constant refers to that which is fundamental because of closed symmetry principles - change that doesn't make a change, then that which is fundamental as an measured and apparently arbitrary ratio (why should up and down quarks lack symmetry in their relative coupling strengths?), and finally, underpinning everything is the Planck triad that is itself a kind of decomposed ultimate constant in breaking reality in three absolute ways.
G defines flatness (in terms of a lack of curvature). h defines uncertainty or vagueness (in terms of a lack of counterfactual definiteness). And c defines the rate at which a thermalising coherence of the two is achieved - the universe arriving at a state that is as flat and decohered as it can get at any particular moment in its thermodynamic trajectory.
Again I stress this is my speculative understanding and not even my final opinion. It is how the current physics looks once you see its maths as a reductionist mask and you start to interpret things instead from the point of view of a holistic systems science, or Peircean metaphysics, approach.