That energy forms into a bunch of particles, each of which will then decay into less esoteric particles.
We have no proof (and it's probably impossible to do so), that anything we've found is fundamental.
This is a good statement.
I've seen many online state that quarks are fundamental.
There is no way we can make such a definitive statement.
Quarks may be not be fundamental.
But using current accelerator technology it would require an accelerator many times the size of the earth, _many_.
I use to work at a particle accelerator, part time, when i was in college. Fun fact i once confirmed Einsteins photoelectric effect using a high energy x-ray beam, a copper target, and high voltage.
We will never, in the lifetime of anybody who guesses we ever existed, be able to build an accelerator powerful enough to check whether it is right about gravity. So, they potter and try to show this or that family of variations (among 10^500 imagined) does or doesn't contradict details of the Standard Model we have most confidence in.
All other particles would be derivative, and their being caused by some base rules.
Physics will only be complete when fully explained in terms of information, regardless of the physical reality of information. The two aspects of explanation are 1. the rules and 2. what are the bits? Perhaps both those things are one.
Perhaps bits are not fundamental and quaternary bits are, but that would still implicate information as fundamental.
It's not possible to do better than that, though, because you can't prove a negative statement like "there are no more fundamental particles". Even if we understood the laws of physics completely, they could always change on us. It's all up to the guy who owns the universe simulator.
I sense that the next step in physics and ontology can only happen when we have created a new linguistic approach to capture the 'fundamental' idea here.
this entire discussion is fully outside of my knowledge wheelhouse but why should we believe that the universe is anything less than infinitely fractal at the micro scale? like you said, how would we even know if something is fundamental?
And what basis does that claim rest on
Physics has had the other problem for a while now - they know the current theory is wrong, but they can't find any evidence to disprove it, and it's wasting generations of scientists and particle accelerators to do it.