What is in the universe at the most basic, fundamental level? Is there a smallest possible brick or set of bricks from which you can build literally everything in our Universe that cannot be divided into something smaller? To this question science has a lot of interesting answers, however which is not truly final and final. Because in physics there is always room for uncertainty, especially when it comes to what we find in the future.
If you would like to know what is in the universe, where would you start? Thousands of years ago, imagination and logic were the best tools available to man. We knew about the matter, but had no idea what it is. It was assumed that there are several fundamental ingredients that you can combine and combine different ways, in different settings — to create all things.
We were able to demonstrate experimentally that matter, be it solid, liquid or gas, occupies the space. We were able to show that it has a mass. We could merge it in large quantities or break up into smaller ones. And break down the matter and to access the smallest components, which will show how “fundamental” it may be, this is a little different. This we could not.
Some believed that the matter may consist of different elements such as fire, earth, air and water. Others believed that there is only one fundamental component of reality is the monad from which everything else turns and going. Others, such as the Pythagoreans, believed that there should be a geometric mathematical structure, establishing rules for reality, and the Assembly of these structures led to the emergence of the known Universe.
The idea that a truly fundamental particle does exist, however, dates back to Orderscom Democritus, who lived 2,400 years ago. Although it was just an idea that Democritus believed that all matter is composed of indivisible particles that he called atoms (“ἄτομος” in Greek means “indivisible”). Atoms, in his opinion, are merged in the background of the empty space. Although his ideas contained many other strange details, the concept of fundamental particles was fixed and left.
Take any piece of cloth that you want, and try to cut. Then break it into even smaller pieces. Every time you do it, or abuse and or abuse, yet the idea of cutting of meaning: the next layer will be thicker than your “knife”. Macroscopic objects become microscopic; complex compounds become simple molecules; molecules become atoms; atoms become electrons and atomic nucleus; atomic nucleus become protons and neutrons, which themselves are divided into quarks and gluons.
At the least possible level we can take everything we know, fundamental, indivisible, particle-like objects: quarks, leptons and bosons of the Standard model.
As for physical quantities, they are defined by the rules of quantum physics. Every quantum in the Universe — structure with nonzero energy can be described as containing a certain amount of energy. Since everything that exists can be described as a particle and a wave, you can set restrictions and limits on the physical sizes for any such photons.
While the molecules may well describe the reality on the nanometer scale (10-9 meters), and the atoms perfectly describe the reality of the scale of Angstrom (10-10 meters), the atomic nucleus is even smaller, and the individual protons and neutrons go in the scale of a femtometer (10-15m). Particles of the Standard model and less. The energies that we were able to test, we can confidently say that all known particles are pointlike and structure-free before 10-19 meters.
The best of our experimental knowledge allows us to name these fundamental particles in nature. Particles and antiparticles, and bosons of the Standard model are fundamental experimental and theoretical points of view. And the higher the energy of the particles, the more evident the structure of reality.
The large hadron Collider allows us to limit the scope of the fundamental particles that way, but the colliders of the future or is extremely sensitive experiments from cosmic rays could bring us many orders of magnitude further: up to 10-21 to 10 or even-26 for the extreme energy cosmic rays.
With all this, these ideas impose restrictions only on what we know and can say. It follows that if we bounce a particle (or antiparticle or photon) with a certain amount of energy with another particle at rest, the affected particle will behave in fundamentally the point manner within our experiments, detectors and achievable energies. These experiments establish an empirical limit on how large can be conceivable fundamental particles, and collectively are referred to as experiments on deep inelastic scattering.
Does this mean that these particles really fundamental? Not at all. They can be:
- and further divisible, i.e. they can be divided into smaller components;
- resonance each other when the heavier “cousins” of light particles represent excited state or the composite version of the lungs;
- not particles, but rather particles in appearance with a deeper underlying structure.
These ideas abound in scenarios like Technicolor (and these scripts were limited after the discovery of the Higgs boson, but it is possible), but most prominently represented in string theory.
There is no immutable law that requires it to be made of particles. Reality based particle is a theoretical idea that is supported by and is consistent with the experiments, our experiments are limited in energy and the information that can tell us about fundamental reality. In scenarios like string theory all the so-called “fundamental particles” may be nothing more than a string vibrating or rotating with a certain frequency, having an open (not connected with two ends) or closed nature (when two ends are linked). Strings can be cleaved, forming two quantum where before it was one, or connect, creating one quantum from two previously existing ones.
At a fundamental level there is no requirement that the components of our Universe was zero-dimensional point particles.
There are many scenarios in which unsolved mysteries of our Universe such as dark matter and dark energy, do not consist of particles, but rather from a liquid or represented by a property of space. The nature of space-time itself is unknown; it may be fundamentally quantum or non-quantum in nature, can be discrete or continuous.
The particles, known to us now, which we consider fundamental, can have either a finite, non-zero size in one or more dimensions, or they can be a true point, potentially down to the Planck length or less.
The most important thing to understand is that everything we know in science, that of conditionality. Including the fundamental nature of particles. There is nothing inviolable or unchangeable. All of our scientific knowledge is only the best approximation to reality that we have managed to build to date. Theories that best describe our Universe, can explain all the observed phenomena, to create new, powerful, testable predictions and have no alternatives.
But this does not mean that is correct in any absolute sense. Science always seeks to gather more data, to explore new territory and scenarios and review yourself if there is a conflict. Particles known to us today seem fundamental, but it does not guarantee that nature will continue to indicate the existence of more fundamental particles, if we continue to dive into the essence of these particles.