An hypothetical conversation between a professor and a student
to discover what the universe is made of.
$: Professor, what is the matter all around us made of?
$: All the matter around us, both in the solid, liquid and gaseous state, as well as the matter forming our biological organism, is made of only three kinds of particles: protons, neutrons and electrons.
$: I know that electrons have a negative electric charge, protons have a positive electric charge while neutrons have no electric charge. Besides, I know that neutrons and protons have a similar mass, while electron mass is about 1800 times smaller. Are these the only differences among these kinds of particles?
$: No, there are many other important differences. First of all, electrons are leptons while protons and neutrons are adrons. Adrons are all those particles which are subjet to the strong nuclear interaction, while leptons are not.
$: Does this mean that leptons are not affected by the strong nuclear interaction just like an electrically neutral particle is not affected by an electric field?
$: Yes, and this has very important consequences because the strong nuclear interaction is the most intense interaction in the universe. It is in fact the strong nuclear interaction which is responsible of the existence and stability of atomic nuclea, which are aggregates of protons and neutrons.
$: And this is then the reason why no nuclea made of electrons exist.
Do any other kinds of leptons exist?
$: Yes, there are only six kinds of leptons. Three of them have a negative electric charge, and they are the electron, the muon and the tau. The muon and the tau differ from the electron because the have a much larger mass. For each of these three electrically charged leptons, there is a corresponding neutrin, electrically neutral particles with no mass or with a very very small mass.
$:Professor, you did not mention muons and taus when I asked what matter all around us is made of!
Why aren't there any muons or taus inside atoms and molecules?
$: Because muons and taus are not stable particles, but they decay very rapidely. Therefore we cannot find them in nature as components of atoms and molecules, but we can produce them in laboratory through very high energy processes, and observe their decay. According to the theory of relativity, it is in fact possible to change energy into matter, and therefore to create particles.The energy necessary to create a particle is however much greater than the energy released in the chemical-physical processes of stable matter; so, to observe the muon and the tau we have to resort to laboratory experiments. Consider that modern particle accelerators allow to reach energies beyond one billion times superior to the energy released in chemical and molecular processes. Electron and neutrins are the only stable leptons.
$: If neutrins are stable, why don't we find them inside the atoms?
$: Because neutrins are electrically neutral, and therefore, contrary to electrons, they are not affected by the electrostatic attraction generated by the protons present in the atomic nucleus.
$: But also neutrons are electrically neutral! Nevertheless, they are present in atoms and molecules.
$: This is due to the fact that neutrons are adrons, and they are therefore subject to the strong nuclear interaction. The forming of atoms and molecules is due only to these two interactions: electromagnetic and strong nuclear interactions. Since neutrins are not subject to any of these two interactions, they are solitary particles, which, after their creation, go away at high velocity.
$: Now I understand why the electrons are the only leptons present in atoms and molecules. How about adrons? I guess that there are some other kinds of adrons, beyond protons and neutrons.
$: Of course. Today we know about 200 kinds of adrons, but there is a fundamental difference with the case of leptons. The six leptons are in fact considered fundamental particles, that is particles without any inner structure. On the contrary, adrons are not fundamental particles, but they are aggregates of two or three fundamental particles. These fundamental particles, forming all adrons, are the quarks. The quarks are only six: up, down, charme, strange, top, an bottom.
$: So, six leptons and six quarks for a total of twelve fundamental particles. Which interaction binds the quarks together, allowing them to form the adrons?
$: It is the strong nuclear interaction, the same that binds together protons and neutrons inside the atomic nuclea.
$: Now I guess that the reason why in the matter around us there are only protons and neutrons is that all the other adrons are unstable and rapidely decay.
$: Exactly. Besides, only two quarks are stable, the quark up and the quark down. The proton is formed by 2 up and 1 down, while the neutron is formed by 1 up and 2 down.
$: So, if we consider only fundamental particles, we can say that all the stable matter around us is made of three kinds of fundamental particles: the electron, the quark up and the quark down.
But now I wonder what photons are!
$: In classical physics, the interaction among particles is described in terms of contact or distance forces, which push or pull the particles. In quantum physics, the interaction is described in terms of exchanges of interaction "bearer", called mediator bosons. Photons are the mediator bosons corresponding to the electromagnetic interaction. For example, the exchanges of energy between particles and the electromagnetic field are described as absorption and emission of photons.
$: I guess that there are specific bosons for every kind of interaction. How many kinds of interactions exist in nature?
$: There are only four kinds of interactions: strong nuclear, electromagnetic, weak nuclear and gravitational. The gravitational interaction is the weakest one; consider that it is more than one billion of billions of billions of billions times weaker than the electromagnetic interaction.
$: If it is so weak, it should produce no relevant effects in matter.
$: Actually, the gravitational interaction among the electrons, the protons and the neutrons forming an atom or a molecule is absolutely negligible. However, the gravitational interaction has the advantage to have an infinite range.
$: This means that, though the gravitational field becomes weaker at larger and larger distances, it never disappears.
$: Yes, and since the gravitational field of a set of particles is the sum of the fields of all the particles, huge stacks of particles can exercise a relevant attraction also at large distances. This is the reason why the gravitational interaction is so important in the dynamics of planets and stars. And it is also so important here on earth, where it manifests itself as an actractive force directed towards the center of the earth. According to the theory of general relativity, gravitation modifies also time, but here on earth we do not notice this kind of effect because it is too weak.
$: The effects of terrestrial gravity are the ones I understand better, at least because of my direct experience. Now I would like to understand the effects generated by the weak nuclear interaction.
$: The weak nuclear interaction is about one hundred billions times weaker than the electromagnetic one. Contrary to gravity, it has a very short range, about a millionth of a billionth of a centimeter. For this reason, in nature the weak nuclear effects consist only in some radioactive decay processes, such as the beta decay, where a neutron changes into a proton.
$: So, in order to explain the phenomena we observe in stable matter, such as molecular, chemical and biological processes, we have only two kinds of interaction: the strong nuclear interaction and the electromagnetic interaction.
$: This is correct, but we must point out that these two interactions have a very different role. The strong nuclear interaction is about one hundred times stronger than the elctromagnetic one, but it has a very short range: about a thousendth of a billionth of a millimeter, which is the typical dimension of an atomic nucleous.
$: This means that an atomic nucleous produces no strong nuclear effect on the particles placed outside the nucleous itself. Unless inside matter, the atomic nuclea are placed so close to one another that they "touch" one another!
$: The atomic nuclea are instead very far from one another. The distance among them is about ten thousands times superior to their dimensions.
$: That is ten thousands times superior to the range of the strong nuclear interaction! But what would it happen if two nuclea touched each other?
$: In this case, a nuclear reaction would occur. However you must consider that, since all atomic nuclea have an electric positive charge, they strongly repulse one another. The only way to place two nuclea close to ech other is to throw them at large velocity against each other, but this requires a very large amount od energy. This is the reason why in stable matter, no nuclear reactions occur. In nature, these reactions occur only in the case of radioactive elements because these atoms have a too large nucleous which tends to break, throwing away the fragments at high velocity.
$: If too large nuclea are unstable, then we can have only a few kinds of different atoms.
$: Right; there are fewer than a hundred stable atoms.
Of course, combining these elements in different ways, we can obtain many different molecules.
$: So, in stable matter, the only role of the strong nuclear interaction, is to keep protons and neutrons firmly bound inside the nucleous. This means that all the processes we observe in stable matter are due to the electromagnetic interaction only.
$: Yes, they are. Quantum mechanics has in fact proved that all molecular, chemical and biological processes are only electromagnetic processes.
$: If the electromagnetic interaction is the only responsible of molecular bonds, why do so many different molecules exist?
$: As you know, the electromagnetic interaction has both an actractive and a repulsive nature: two equal charges repulse each other, while two opposite charges attact each other.
Since the intensity of this repulsion and attraction depends on the distance among the particles, a modification of the positions of the atomic nuclea changes the interaction among the nuclea and among the nuclea and the electrons.
A stable molecule is formed when nuclea are placed in a geometrical configuration where repulsive and attractive forces balance. The equations of quantum mechanics allow to calculate these configurations, and to know how much energy is necessary to break the molecule or to modify the geometrical structure of the molecule.
$: So, many different molecules exist because many different stable geometrical configurations exist as the number or the kind of atoms change. The stiffness of a molecule depends on the amount of energy necessary to change the geometrical structure of the molecule. But what happens then in a chemical reaction?
$: In a chemical reaction, one or more molecules break, which means that one or more atoms come off the molecule. This creates an unbalance of forces pushing the atoms towards a new stable configuration, that is a new molecule or new molecules.
$: Which is the cause of the break of the molecule?
$: The causes may be various; for example, temperature. Temperature is related to the average kinetic energy of the particles. The higher is temperature, the faster the molecules move; when molecules collide with one another, they give some energy also to the atomic nuclea, which vibrations get stronger at encreasing temperatures. When the intensity of these virations becomes sufficently high, some atoms come off the molecule.
$: Quantum mechanics gives then a very clear mechanicistic explanation of all chemical processes. Does this mean that also all biological processes are explainable by quantum mechanics?
$: Of course. Actually, biological life consists uniquely in several successions of chain chemical reactions.
$: How does this chain work?
$: After a chemical reactions, atoms are placed in a different geometrical configuration. If the energy of the new geometrical configuration is greater than the preceding one, it means that the molecules have absorbed energy from the external environment, while, in the opposite case, there is an emission of energy; this energy may be absorbed by another molecule and a new chemical reactions may occur, and so on.
$: This reminds me that japanese game where many dominoes are placed in a long row; when the first domino falls down, it makes the second one fall down, and so on.
$: Of course, the process can go on only if every domino is in the right place, otherwise the chain breaks. The death of a biological organism consists in the break of the chain of its chemical reactions because of some fundamental missing element.
$: Science gives then a clear and logical mechanicistic explanation of biological life. However, I see no explanation of the psychical life. Electrons and quarks certainly do not think, they are neither sad nor happy, they feel no pleasure, no pain, etc.
$: Perfectly right. Materialism is a phylosophy which developped long before quantum mechanics, when biology and chemistry were considered independent from physics and biological matter was considered radically different from inorganic matter. In particular, many phylosophers believed that biological matter and cerebral processes had a different nature from inorganic matter and inorganic processes. Quantum mechanics has scientifically proved that these opinions were completely false. Now we know that biological matter and biological processes have exactly the same nature of inorganic matter and processes, and that all biological and cerebral processes are determined uniquely by the laws of quantum electrodynamics.
$: Materialists claims that sensations, emotions and thoughts are generated by the chemical reactions and the electric impulses which occur in our brain.
$: This is clearly a scientifically wrong opinion, since chemical reactions, both inside and outside the brain, consists only in a chamge of the geometrical configuration of the atomic nuclea, with a consequent settling of the electrons. On the other hand, electric impulses, both inside and outside the brain, are only moving electrons; the laws of physics establish that electric impulses generate only electromagnetic waves which spread in the space at the speed of light. The electric impulses inside the brain are then absolutely equivalent to the ones in a bulb, and they generate no sensations, no emotions, no thoughts.
$: What creates sensations, emotions, consciousness?
$: What we know is that the cause of the existence of consciousness, sensations, emotions and thoughts is neither a material nor a physical entity. We can call this entity with several different names, such as mind, psyche, soul or spirit. Apart from the name, the fundamental result is that such entity certainly exists in man, and then man is not only a biological organism. In man there is something else, something transcending the physical, material, biological reality.
$: How can then the psychical effects of drugs or cerebral trauma be explained?
$: They are explained by the existence of an interaction between psyche and brain. On the other hand, if such interaction didn't exist, man could never know the external reality and he would be completely isolated from the external environment. In fact, man knows the external reality only through his senses, which are connected to the brain, which represents the interface between the psiche and the esternal reality. Because of this interaction between brain and psiche, every alteration of the normal cerebral activity affects also the psyche.
$: Since the brain can generate no sensations, I wonder whether it is possible to prove the existence of sensations and emotions in animals?
$: No, it isn't. There exist no instruments allowing to detect or measure sensations and emotions. This is due to the fact that all intruments are designed on the basis of the laws of physics, while psychical experiences transcend the laws of physics.
$: Can we prove scientifically the possible existence of sensations or emotions in animals through the analysis of their behavior?
$: No, because it would be a matter of subjective and arbitrary interpretations; no arbitrary interpretations can be considered a scientific proof. In fact, a fundamental requirement of every scientific theory is the "inter-subjectivity"; in other words, a scientific theory must be supported by (experimental and rational) objective elements which can be shared by everybody, endowed with reason and intellectually honest.
Science has proved that it is possible to build some machines (computer, robot, etc.) able to react to external stimula and analyze imagines, sounds, etc. Of course, these machines make use of automatic processes and they feel no sensations. The behavior of animals is then explainable in the same way, that is as a mechanism of automatic reaction to external stimula. This explanation is plausible both from a logical and scientific point of view. Because of the absence of any objective scientific elements, the idea that also animals have sensations and emotions is to be considered a personal opinion, without any scientific foundations.
$: It seems to me that the most important question is then: how does our mind or psyche come into being?
$: This is certainly the most important question. On the basis of our scientific knowledges, we can establish that our psyche does not come into being because of any physical, chemical or biological processes. The Cause of the existence of our psyche transcends the laws of physics and the material reality. We have then come to speak of God.