What is matter?
What is matter?
The matter is any substance (composed of various types of particles) that has mass, inertia, and occupies physical space by having volume. This definition, adequate for macroscopic physics, the object of study of mechanics and thermodynamics, does not fit well with modern theories in the microscopic realm, proper to atomic and subatomic physics. In physics, there is no unanimous consensus on the definition of matter, in part because the notion of “occupying space” is inconsistent within quantum mechanics. Instead, many physicists prefer to use the concepts of mass, energy, and particle.
For example, the space occupied by an object is mostly empty, given the large ratio (≈105) between the average radius of the electronic orbits and the typical size of an atomic nucleus; moreover, the law of conservation of mass is strongly violated on subatomic scales. In these fields, it is possible instead to adopt the definition that matter is constituted by a certain class of particles, which are the smallest and fundamental entities physically detectable: these particles are called fermions and follow the Pauli exclusion principle, which states that no more than one fermion can exist in the same quantum state.
Because of this principle, the particles that compose the matter are not all at the minimum energy state and for this reason it is possible to create stable structures of assembled fermions. Particles of the complementary class, called bosons, constitute instead the fields. They can then be considered the agents that operate the assemblies of fermions or their modifications, interactions and energy exchanges. A metaphor not entirely correct from a physical point of view, but effective and intuitive, sees the fermions as the bricks that make up the matter of the universe, and bosons as the glues or cements that hold them together to constitute the physical reality.
The atom is the simplest example of matter particles, which represent the smallest unit of matter composed of electrons, the protons, and the neutrons. They retain all of the chemical properties of an element. Massless particles such as photons, energy phenomena, or waves like light or sound, are not included in this definition.
Matter and mass should not be confused with each other because they are not the same thing in modern physics. The matter is a general term describing any physical substance, and the mass is a quantitative property of matter.
The term matter can be traced directly to the Latin term mater, which means mother. The etymology of the term, therefore, suggests how matter can be considered the constituent foundation of all bodies and all things: the first substance of which all other substances are formed. The term matter derives from philosophical jargon.