In search of a source of mass
Is the measurement of the mass of an object derived from any of its more basic religions? What does modern particle physics say?
How classical physics depends on mass:
The way the definition of mass is given in school textbooks, many of them may be a little confused, — let’s start the discussion from there.
“The amount of matter in an object is called the mass of that object.”
But how can the matter be measured? Suppose a friend of mine from school, Democritus, was asked such a question. The answer to the wise Democrats is ready, ‘Very straightforward. An object is made up of countless molecules, measuring the amount of matter in a molecule. Multiply that by the number of molecules in the object. Then the mass of the object = the total number of molecules ⨉ the mass of one molecule.
One thing is clear from the words of Democritus. In classical physics, the concept of mass somehow comes from the combination of density (in this case mass of a molecule) and volume (in this case brown molecule). That is mass = density ⨉ volume.
But this idea of mass is not exactly complete. For example, to reach the given speed of Newton, we have to assume that there is one more fundamental mass of religion. That is the permanence of mass, — mass cannot be created or destroyed. This religion is so fundamental in Newtonian dynamics that it can be called Newton’s zero motion! However, from the idea derived from Democritus, it is not clear why mass will be conserved.
We then define momentum as a ‘measure of the kinetic velocity of an object’, — mathematically what is written as the mass ⨉ velocity of an object. Using the definition of momentum and the constantness of mass, the concept of momentum retention of a particle from Newton’s first law of motion and the concept of a force from the second law of motion is very simple. As you can see, Newtonian kinetic mass is the main idea behind which classical physics grew. See a more detailed discussion here.
In order to reach the speed given by Newton, we have to assume that one of the most fundamental properties of mass is the permanence of mass.
But what is the source of mass? Can we get a measure of the mass of an object from any of its more basic religions? The biggest question is, in the absence of ‘matter’ can there be the mass of an object? The last question may bring the famous E = mc2 formula to the minds of many. It’s okay to think that way, but we’ll go a little bit further with more arguments and evidence and try to understand how much of the mass comes from energy. Most of the mass of an atom comes from the nucleus, and the nucleus contains two very heavy particles — protons and neutrons. These two particles are a huge amount of captive energy, matter? Actually what is in it!
A few words about the nucleus:
To try to understand how the mass of protons and neutrons comes together, let us first look at these two experimental facts about the nucleus of an atom:
- The nucleus is a very durable thing, in which neutrons and protons are very well bound. Which force holds them together so well? That cannot be the electromagnetic force we know. Because neutrons are chargeless — they are not affected by the electromagnetic force. And the condition of protons is more serious. All protons are positively charged, so they repel each other by the electromagnetic force. From there, it can be inferred that the nucleons (protons and neutrons together are called by this name) have a completely different gravitational force that is not dependent on the charge. And to hold all the nuclei together, this force must overcome the electromagnetic repulsive force between the protons. So this force is stronger than the electromagnetic force.
- With the discovery of the neutron by James Sadwick in 1932, another strange thing came to the attention of scientists. The mass of protons and neutrons is roughly the same, and if we forget that protons have a positive charge, the two particles behave in the same way. Warner Heisenberg infers from A that protons and neutrons are opposite sides of the same quantum state. Just like electrons with up-spin and down-spin. That is why this strange symmetry is called ‘isotopic spin’ or ‘isospin’ in keeping with the spin-symmetry. In mathematical terms, this symmetry is the symmetry SU (2) and the same symmetry is also fundamentally represented in the spin of electrons. However, this symmetry means that roughly the same amount of nuclear force will work between two protons or two neutrons or one proton and one neutron. In this context, let me say that physicists have a special love for such equality because it makes a theory beautiful. As a result, calculations often become quite simple.
Warner Heisenberg speculates that protons and neutrons are opposite sides of the same quantum state.
Then let’s go forty years ahead. It is understood that Heisenberg’s guess is fairly accurate. At the same time, it has been observed that protons and neutrons are not fundamental or indivisible particles. They are each made up of three more elementary particles. They are named quark. The protons and neutrons are almost identical but not completely one because the quarks have different ‘flavors’. Both protons and neutrons have ‘up’ and ‘down’ flavor quarks, but protons have two up and one down and neutrons have one up and two down (see image). The charge of up is + (2/3) e and the charge of down is — (1/3) e, so the charge of protons is + e and the charge of neutrons (-e = charge of an electron). And the SU (2) symmetry of the proton-neutron comes from the SU (2) symmetry of the up and down.
Where the mass of Nucleas comes from:
Even if all this is right, the problem is elsewhere. Two problems and both are pretty crazy. First, free quarks alone have never been seen. However, the behavior of the compound particles in which these quarks are bound provides indirect experimental evidence for the existence of quarks. Second, the mass of the nucleon is about a thousand times greater than the mass of the up and down quarks obtained from quantum field theory. Meanwhile, there are only three quarks in the nucleus. If not from the quarks, where does the mass of the nucleus come from? To understand the two puzzles, let’s start with the example of the familiar electromagnetic force. Two charges apply force on each other by exchanging photons. A photon is a carrier of an electromagnetic force and may have momentum or momentum according to relativity even if it has no rest mass. When two charged photons are exchanged, momentum is also exchanged, which is manifested as an electromagnetic force.
The repulsive force between two electrons (e — ^) originates by exchanging photons (γ) between them. The arrow signifies the direction of the two electrons. Similarly, forces are formed between quarks inside protons or neutrons through gluon exchange.- See Image
The funny thing is that the photon itself is non-charged, meaning that two photons cannot apply force to each other.
Generalizing these ideas also shows the force that binds quarks inside a nucleus. This force is called a strong force or color force. The two quarks have a color charge and the momentum between them is exchanged by the exchange of gluon particles, which are manifested as the color force.
Like photons, gluons are massless particles. But the biggest difference between these two particles is that gluons have a color spectrum, so they can interact with each other even in the absence of quarks. In this way, they can also create new gluons. So as the distance between the two quarks increases, more and more gluons are formed by the interaction of the gluons between them. This creates so many colored forces that the quarks are completely bound and cannot leave each other. This is why free quarks alone are never seen.
Not only that, but the size of a nucleus is also close to that of a pharma (femtometer). If the quarks are at this distance, so many gluons are formed between them that the three quarks seem to float in the sea of gluons. These gluons cannot escape from the confinement of the nucleon again because the collective spectrum of a nucleon is zero and he wants to remain in that state. Since gluons have spectroscopy, the nucleon will no longer have zero spectroscopy from a nucleon that is not favorable at all. In this way, a proton or neutron can hold a huge amount of energy within itself, which is reflected as their mass according to the formula E = mc2.
There is no end to the questions:
Pretty nice explanation! However, there are a few more questions whose answers are still unknown to us. The distance between the nucleons themselves within a nucleus is almost the same as the distance between the quarks inside the nucleus. So why don’t these quarks merge to form a quark-commune in the nucleus? Why are protons so permanent particles? Can protons break down on their own? Particle physicists do not want the proton to be a permanent particle. Because if the proton is temporary, we can use it to solve a bigger puzzle. That is, why is the amount of matter in this universe so much greater than the amount of antimatter? (It would take another whole text to tell the story. So I’m pressing for now. You can Google Baryon asymmetry.) It’s not yet clear where the mass of particles like quarks or electrons comes from. Particle physicists have asked and answered that question. They get to mass by interacting with the Higgs boson, but how, the explanation is quite profound. We will discuss that later.
Note:
[1] We know the nature of photons in the same way. There are two main reasons why we see any object in the vicinity: One, the photons that come from that object do not interact with each other. Two, photons do not interact with nitrogen or oxygen atoms, because atoms are inert at normal temperatures. This means that a photon reflected from an object does not interact with anything else on its way to us.
