Why stop there? Maybe those particles are made of even smaller particles.
Why not? Atoms were once thought to be elementary, indivisible particles.
Atomos means "indivisible" in Greek.
We discovered the electron empirically. We made a machine that separated electrons from the rest of the atom and manipulated them in a way that allowed us to observe that they had an electrical charge and a computable mass. The formulation of the rest of the structure of the atom proceeded empirically. But it also required a mathematical formulation, because such things as the inertiall masses of the particles and their charges had to balance. Because of the math we were able to deduce the existence of the neutron. Then more machines proved the existence of a massive nuclear particle that did not have an electrical charge.
This is the pattern by which physics discoveries have proceeded for 200 years—interleaved and mutually supportive observation and mathematical deduction.
Quarks et al. were discovered empirically as higher-energy machines were able to smash matter more violently and produce observations that could not be explained by the three known kinds of particles. As usual, this "zoo" of observed new particles was organized using mathematics into what we call today the Standard Model. The model proposes properties that exist as mathematical entities associated with measurable behavior in each of the "-ons."
Among other things, this model explains fundamental physical forces by proposing the existence of force-carrying, massless particles called bosons that carry force across spacetime by being exchanged among affected mass-having particles. Electromagnetic force, for example, is carried by the photon.
The problem with the math is that the simplest and most elegant equations only described the observed behavior if all the particles involved had zero mass, including the ones for which we knew empirically this was not true. The solution was the Higgs field, with which some particles interacted in a way that gave them the appearance of inertial mass. Interactions with fields (quantities that vary over spacetime) describes almost all of what we can observe about the universe, so this made intuitive sense.
But if this were true, then high-energy motion through the Higgs field would create something we could observe. If you have a boat moving slowly through the harbor, it generates little if any wake. But it still experiences hydrodynamic drag and so still exhibits behavior consistent with something moving through a fluid. But when the boat speeds up in open water, it creates a visible wake. In a sense, the observation of the wake proves the existence of water through which the boat moves. It's a localized disturbance in the fabric of water that looks different than the surrounding water and stands out so we can observe it.
In normal quantum field theory, such localized disturbances are called "particles." That is, when the various fields (descriptions of the change in some value over space and time) described in quantum field theory "kink up" and form localized "wakes," that's where a particle is. There's a field that describes quarks, for example. When a "wake" forms in it, a quark appears.
Planck's remarkable contribution to this knowledge was the observation that these kinks or wakes can only form in certain locations and times, like spots on the grid in the game
Battleship. Your shots can only land in the named spots, and only when you take your turn. They don't show up in half-positions or in half-turns.
But I digress. How do we make particles move so fast that the Higgs field (the "water" that fills all of spacetime) will form a visible wake (i.e., "kink up" and make a particle appear there)?
You make a Large Hadron Collider.
You've seen the giant detectors it takes to observe these kinks, because they stand in for part of the
Enterprise's warp drive in the J.J. Abrams
Star Trek universe. Lo and behold, we observed a wake or kink—which we famously already gave the name of "Higgs boson." So we proved the Higgs field exists as predicted. The field that creates a Higgs boson under conditions of duress is what gives some particles inertia and therefore inertial mass.
So what does a Higgs field look like? What does
any field look like? You know what a magnetic field looks like because the magnetic field lines are the characteristic graphical expression of a magnet. And we can draw similar field lines for electrical fields. And, it turns out, for gravity. But I'm getting ahead of myself. Those lines are the locations in space where the quantity in question, say, "the amount of magnetic attraction," are equal, like elevation lines on a topographical map. But it's the
math that tells us where to draw those lines that is interesting to physicists. Math can be tested and manipulated and combined with other math to make predictions.
Imagine your teakettle full of water on the stove, heating up to make tea. Freeze time. Every tiny portion of the water in the kettle is at a different temperature. The water near the burner at the bottom is hotter than the water at the top. At every (x,y.z) coordinate inside your kettle, a different temperature value appears. This is a field, a "temperature field." You can compare the temperature at two points. The direction between the points is the direction part of a vector. The difference in temperature could be the magnitude of that vector. So you can overlay a field of vectors (several fields, in fact) that describes the difference in temperatures as vectors as you look in any direction from any point.
To simplify the mind-boggling complexity of that, we open up the field of "differential geometry," which uses the upside-down triangle operator ∇ in conjunction with vector math to concisely describe the ways in which quantities change through the field. A handful of such equations describes the shape and strength of all fields in physics. Solving them for specific values gives us those field lines that help you see the shape of the field without understanding the math. But it's the underlying math that physicists care about because they can manipulate the math algebraically to arrive at testable predictions and combine them with other fields. It's why you can't have physics without math.
Notably absent from any of this is gravity. Nothing in the Standard Model explains the apparent attractive force between two masses.
Einstein and his mathematician buddies wrote down some field equations that describe gravity accurately (i.e., we can observe that they work even under weird corner-case conditions), but their field equations have nothing whatsoever to do with the field equations that the Standard Model uses. It's not even apples-and-oranges. It's like comparing apples to brake pads.
The Standard Model
could explain gravity by means of a new particle, the graviton. It would do for gravity what the photon does for electromagnetic force—if it could only be proven to exist. If it does exist, and if it does behave as required, then it has to have certain properties that apply to all particles in the Standard Model. You've heard of "spin" and "charge" and so forth. You would need to be able to describe a graviton in those terms and show that it participates in Standard Model equations through the mathematical expression of those properties.
To be sure, Einstein's model of gravity—curved spacetime—doesn't need any kind of particle at all. Gravity in his model isn't a force that needs a field or particle to make it happen. It's not a force at all. It's pure geometry.
@wise47 proposes that he has solved this problem, which is arguably the greatest open problem in physics—a so-called Theory Of Everything. He says the graviton exists and is a "bulges of space," which he vaguely describes as akin to spacetime curvature in Einstein's model. The Standard Model provides field equations that tell us how and where to find the "kinks" that we see as quarks, bosons, etc. Einstein's model provides field equations that tell us how spacetime curves in relation to masses and therefore how objects that think they're traveling in a straight line are actually bending to follow spacetime and thereby appear to be attracted to other masses. To be sure, there is a branch of physics called loop quantum gravity that is proposing one way to unify these two dissimilar visions of how matter behaves. They're working their way through different possibilities of field equations that might explain observable behavior, but so far they've had little luck. And while
@wise47's explanation alludes to concepts in that physics, he won't actually embrace it.
Instead
@wise47 proposes that he has figured it all out without all that pesky math or without borrowing from others' work. We're rightly suspicious because his presentation is copiously decorated with telltale phrases like "It can be assumed..." and "We can say that there is..." In other words, pure "shower thoughts," as someone observed. And the empirical foundation of his theory is his "observation" of a tiny "microgrid" (Planck on steroids?) through which his tiny conjectural galaxies of wise47-ons bob and weave. As has been done previously in physics, he just keeps slicing things up finer and finer. Only he can't do the slicing with the mathematical knives his predecessors know how to use, so we can't even being to study whether or not it would work.
He doesn't say how he observed his "microgrid," so we propose that he did so in the same magical way as he raises his own I.Q. to 1600 (claimed in his other threads). His pseudo-physics gibberish in the linked article is liberally mixed with assurances of his own personal prowess as a scientist, able to see beyond the conceptual blockade that pervades the entire field as it is now practice.
In other words, pure crackpottery.