Anyone who has pondered the question of whether matter can be subdivided all the time or not. If matter cannot be subdivided, what exactly is the smallest matter?
According to current physical theory, the smallest degree of subdivision of matter is the quark, to the end of the quark, it can no longer be subdivided. After reading the article patiently you must have understood the reasoning.
Before the 20th century, mankind had not yet invented the electron microscope, and although the existence of atoms was known at that time, there was still basically a gap in cognition, and the knowledge of matter basically remained at the molecular level.
In the late 19th and early 20th centuries, scientists discovered a structure of matter smaller than the molecular scale: the atom.
But there is no microscope to see directly what an atom looks like, and physicists can only speculate about the possible atomic structure through related phenomena.
In 1803, Dalton was the first to propose the modern atomic model, arguing that the atom is the smallest particle of the material world, a solid sphere that cannot be subdivided, and that everything in the world is formed based on different permutations of this smallest solid sphere.
This idea, of course, inherited from the atomic theory of the ancient philosopher Democritus, relies on subjective conclusions.
By 1890, man had invented the cathode ray tube, and a green fluorescence could be observed by irradiating zinc sulfide. In fact, these green lights are the effect of a magnetic field controlling the movement of a stream of negatively charged particles.
It was thanks to the cathode ray tube that physicists discovered that atoms can be electrically charged.
But sometimes the atoms are electrically neutral and sometimes they are electrically active. So scientists deduce that the electron is definitely not a solid ball with electrons embedded inside it.
The fact that the atom is electrically neutral proves that there is positively charged material inside the atom that counteracts the charge of the electrons.
The electrical nature of an atom indicates an imbalance in the ratio of positive to negative charges inside the atom, either more positive charges inside the atom to cause the atom to be positively charged as a whole, or vice versa.
Since that time scientists already knew that atoms were made up of electrons and positively charged matter inside. Then it was time to think about how these charges were actually distributed, and a wave of various predictive atomic models was set in motion!
For example, Thomson's "raisin bread" model suggests that the positive and negative charges within an atom are evenly distributed within the atom like raisin bread.
Later, Rutherford concluded from numerous alpha particle scattering experiments that there is a nucleus inside the atom, which is positively charged, and a group of negatively charged electrons outside the nucleus moving around, just as the planets move around the stars, obeying the rules of circular motion.
In fact, the development of physics' knowledge of the interior of the atom up to Rutherford's time was still stuck in classical mechanics.
But soon scientists found that, according to Maxwell's electromagnetic theory, the electrons moving around the nucleus of an atom will emit electromagnetic waves, which is a loss of energy, reduced energy electrons in accordance with the logical reasoning of the planets moving around the stars, will inevitably fall to the nucleus, this process will occur at the beginning of the birth of the universe, and later all the nuclei in the universe outside the nucleus there can not be a group of electrons in circular motion.
So now new atomic models are needed to explain this phenomenon. That's when the fierce man, Bohr, came across the scene. Bohr was the physicist who really quantified the atomic model, and since then it has become extraordinarily difficult to understand.
At that time, Planck's quantization of energy and Einstein's photoelectric effect were already recognized.
In 1913, Ball proposed an energy level model for electrons based on the spectrum of the hydrogen atom, arguing that electrons are at different energy levels outside the nucleus and that energy levels are not a concept similar to planetary orbits. Because the change of planetary orbits has a transfer process, which is continuous.
The switch between energy levels is a leap, a step in place, there is no transition in between, the electron absorbs a copy of the energy, can be directly from the low energy leap to high energy levels, this "a copy of the energy" is not refinable energy value, another academic name is called energy quantization.
The development of the atomic model into the Bohr period raised new doubts.
Since everything is made up of atoms, and atoms are made up of nuclei and electrons. What are electrons and nuclei made of?
Electrons were discovered long ago and the study of the internal structure of electrons has been going on until after the Ball model was proposed, when scientists discovered that since electrons absorb energy quantitatively, they should not have an internal structure.
Once the electron has an internal structure, the absorbed and released energies cannot correspond exactly to the spectrum, because the internal structure of the electron may "swallow" some of the energy, resulting in a linear relationship between the spectrum and the energy change during the electron leap.
So physicists have basically decided that the electron is the smallest kind of particle since then, and no longer expect to study the internal structure of the electron.
Although Rutherford was the first to discover the nucleus, at that time he did not know the internal structure of the nucleus.
Meanwhile, Rutherford's scattering experiments have shown that the nucleus is much heavier than the electron, and that the nucleus is probable to have a much smaller internal structure.
At that time, it was already known that the nucleus was positively charged, and if the nucleus had an internal structure, this positive charge would have been given by the matter inside the nucleus.
Nowadays we know that the nucleus of an atom consists of protons and neutrons. Protons are positively charged and neutrons are uncharged.
Since neutrons are not charged, they are difficult to be observed at that time. So for a time, people mistook the nucleus of an atom for a proton.
In fact, protons were discovered very early, in Rutherford's scattering experiments, Rutherford called the nucleus of an atom a proton, and at that time it was thought that the nucleus was the proton, so the study of the internal structure of the nucleus seemed at that time to be the study of the internal structure of the proton.
Rutherford understood that if the nucleus had only protons, there would be no conservation of atomic mass.
At that time, Rutherford had already predicted that there should be some uncharged, electrically neutral material in the nucleus that would take up some of the atomic mass. But no more experiments were done to verify the existence of such substances.
It was not until 1932, when scientists bombarded nitrogen-13 with boron-10, that they discovered that there was an uncharged particle in the nucleus, and that this particle was the neutron.
This is when physics learned that the nucleus of an atom is made up of protons and neutrons.
Of course, new questions immediately arise: do protons and neutrons have an internal structure, and what are they made of?
Now we know that quarks have the property of "color charge", so the study of the interaction between quarks is also called quantum chromodynamics.
Because of the very late discovery of quarks, quantum chromodynamics was not established until the mid-1960s.
The discovery process of quarks is so complex that you may not be able to read it without a deep knowledge of specialized physics.
I will next dedicate an article to the process of quark discovery.
This article is just a brief reduction of the idea of quark discovery
Although physicists at that time discovered protons and neutrons, they were found to be not particularly stable and occasionally switched between each other, that is, protons would become neutrons and neutrons would become protons under certain circumstances.
In the spirit of simple philosophy, physicists believe that if a thing is not stable and changes its state, then this change must be determined by internal factors.
A non-refinable substance is stable and unchanging, and if it can change, then it proves that there must be smaller internal structures at play.
The first theoretical predictions of the existence of quarks were made by Gellman and Zweig, and the corresponding quark model was proposed in 1964.
It was not until 1968, when deep inelastic scattering experiments at the Stanford Linear Acceleration Center revealed that there were smaller dots inside the proton, so it was a definite fact that the proton had internal structure, and that these dots were quarks.
And does a quark have an internal structure?
The modern view of physics is: no!
Because quarks are already the smallest matter and belong to the elementary particles.
In the standard model, the elementary particles are the smallest particles and cannot be subdivided any further, so matter subdivided into quarks comes to a head. Or strictly speaking, as far as mankind's current physical framework is concerned, the internal structure of quarks is unknown, or unproven strings!
It may be hard for many people to believe that matter is subdivided into quarks and that is the end of the line?
It is difficult to be accepted, both emotionally and rationally.
Why do physicists believe that quarks cannot be subdivided any further?
Because this is related to the four basic forces, the reason why they are called basic forces is because these forces are the most fundamental interactions in the universe.
All mechanical phenomena in the macroscopic world, once traced back to first cause and effect, will eventually be found to be caused by these fundamental forces, and if there were deeper mechanisms for the fundamental forces, they would not be called fundamental forces.
For example, friction, elasticity is the essence of electromagnetic force, friction and elasticity are only the macroscopic manifestation of electromagnetic force. The reason why friction is not a basic force is because there is a deeper reason for its action, which is the electromagnetic force.
The centripetal force of the Earth around the Sun is also not fundamental, because it is only an expression of gravitational force.
So the transmission of fundamental forces is necessarily carried out by elementary particles. If the propagator of the fundamental force is not an elementary particle, but a composite particle, what force is at work inside the composite particle, so these so-called fundamental forces would not be fundamental forces.
Nowadays we already know that the propagator of the electromagnetic force is the photon, which is the elementary particle.
The propagators of the weak force are the W and Z bosons, which are also elementary particles.
The strong propagator is the gluon, which remains the elementary particle. The propagator of gravity is the graviton, and although the graviton has not yet been discovered, scientists are convinced that the graviton is also an elementary particle and has been reserved for it in the Standard Model.
But what does all this have to do with whether quarks can be further subdivided?
Of course it is relevant, and non-discretization proves that quarks are elementary particles.
This is because electrons can radiate photons and are one of the most primitive channels of birth.
Photons are elementary particles, it proves that the electron must also be elementary particles, because if the electron is not an elementary particle, then the radiation photon must be caused by the electron's internal, then the electron is not the most primitive radiation channel of the photon, there is no evidence that the electron has an internal structure.
Theoretically, the generation of propagators of fundamental forces should also be caused by particles of the same level.
The action between the elementary particles is of the same level, if not, the elementary particles should be interacting with the internal structure of the composite particles only, and not with the composite particles.
We'll look at weak and strong forces at this point.
Scientists found that the weak and strong forces occur at the quark level, where the flavor change of quarks triggers the weak force and the confinement between quarks is caused by the strong force.
So the two fundamental forces, the weak force and the strong force, both act at the quark level, so we have reason to believe that quarks are elementary particles, which cannot be subdivided any further.
At the end of the article, I have to emphasize that all speculations are currently based on the existing physical framework.
If in the future quarks are found to have a smaller matter component, that would completely destroy the entire Standard Model. And it may lead to the removal of the weak and strong forces from the fundamental forces.
In this way, the fundamental particles of the Standard Model will be completely rewritten.
In fact, I hope so, if science is developed in accordance with the concept of human simplicity and beauty, then physics has ended in Newton's time. There will not be today's quantum mechanics and relativity, and we naturally can not enjoy the technological achievements brought about by these theories.