Symmetry between up and down quarks is more broken than expected

It's not as bad as that. AIUI, the essence is, if you've ever seen the concept of a Feynman diagram and summing over all possible interactions, that works well for electromagnetism and some other interactions because the alternative terms fall off very quickly. For the strong interaction, they fall off so slowly that it takes massive amounts of computing power to walk through all the alternatives, essentially infeasible amounts of it. So we have to use some heuristics. If it turns out one of our heuristics was wrong, well, that's actually happened a number of times before.

So it's not quite as bad as "you just hit the model until it says what you want it to say". It's more "your shortcut broke so take less of a shortcut and you may discover that the standard model worked better all along than your shortcut". Which, again, has already happened multiple times.

In fact it is quite frustrating to physicists that the standard model always wins these fights. They'd love for it to break in some concrete manner, which is why they're always going on about this break or that break. As it stands now, in some sense, every time the standard model is vindicated it's a worst-case scenario for particle physics. It's not like there's a cartel trying to defend it... everyone would love to be the one who definitively broke it! It's virtually a guaranteed Nobel prize.

So far nobody expected this effect so no attempts were made to derive at least the bounds on it from the first principles. With strong interactions it may require a lot (like many man-years) of efforts, but it will be eventually done if no plausible explanation can be given using semi-experimental models.

Well, it's intended to explain everything so, y'know.

the standard model isn't one thing, it's the sum total of human knowledge of particle physics. it's an equation with a gazillion terms - this is an adjustment to one of those terms. and yes, you can add terms for any new physics you discover, so technically you're right, but it's not a gotcha.

The first principles here refer to the basic equations of the Standard Model. There were a lot of alternative theories in sixties and seventies but eventually they were disproven experimentally and only SM survived.

But the problem with SM is that when one deals with strong interactions, nobody so far came with good ways to calculate things. For example, in theory the mass of proton can be derived. But in practice it is not. So one uses that as an extra parameter and tries to use that to constrain calculations in other areas.

The data comes in two ways:

1. Hey these particles are interacting with each other (e.g. they attract each other, they repel each other, they combine or split apart into each other, etc...)

2. I have measured something about this interaction (e.g. how fast, how far, how likely, etc...) to within a certain degree of accuracy

Put them together and we have a sparse noisy list of forces, and a list of constants.

Then we come up with theories to explain and reduce the data to their simplest components.

Those theories occasionally spit out that there should be an interaction we haven't seen between some particles yet or a more accurate picture of an interaction we have already seen and we can run some experiments to see if the theory holds true in practice.

We can then check how well those theories work by their predictions.

- Gravity is just varying amounts of positive attraction over unlimited range (i.e. just a positive integer).

- Electromagnetism is varying amounts of positive or negative attraction over unlimited range. (i.e. just an integer)

The problem with strong interactions is that they get messy really fast. The energies and interactions involved are crazy.

- We have the quarks (which are the fundamental matter particles that the strong force interacts on)

- We have the gluons (which are part of the strong force itself)

- And the strong interactions: which are actually 3 different amounts of positive or negative attractions that must all balance out (i.e. a whole bunch of numbers), but they get stronger as they get further away to the point that new particles can be created to reduce the range between any two particles, oh and the gluons can also interact with each other complicating matters further.

> using isospin and hypercharge is like using epicycles to describe the motion of the planets

No, it isn't; those are actual quantum numbers of the electroweak interaction below the symmetry breaking energy (the other such quantum number is electric charge).