We explain what modern physics is, its goals and how it differs from classical physics. Also, what are its branches.
What is modern physics?
In the scientific field, we speak of modern physics to refer to contemporary studies on the fundamental laws of the universe which take as their starting point the formulation at the end of the 19th century and the beginning of the 20th of two revolutionary theories on the subject:
- quantum theory by Max Planck from 1900.
- The theory of relativity by Albert Einstein from 1905.
Heisenberg's indeterminacy relation of 1927 is often incorporated into this. In any case, all previous physics studies are known as classical physics.
However, this difference is not merely historical, as it might seem. On the one hand, modern physics It is distinguished from the classical due to the notion of “quanta of action” (Wirkungsquantum) proposed by Planck, who proposed it as the minimum possible energy level.
That is, according to this modern approach, the energy in the universe could be divided into minimal and indivisible units (each called a “quanta” or quantum), while in classical physics energy was continuous and indivisible.
On the other hand, modern physics replaced the idea of a deterministic physics, in which all phenomena in the universe could be described as the result of a cause and an effect, with a physics of indeterminacy and inaccuracy. Thus, modern physics usually talks about probabilities of occurrence of a phenomenon as it deals with the mysterious laws that govern matter and energy.
The latter is because classical physics largely studied situations that the human senses could encompass, that is, situations from a macroscopic point of view.
In contrast, modern physics delves into more complicated regions of the universe, such as subatomic matter and the wave-particle behavior of matter, or physical phenomena that occur at the speed of light. In these scenarios, classical laws are no longer useful.
On the other hand, one of the main aspirations of modern physics is to achieve the integration into a single harmonious theory of all known natural forces: gravity, electromagnetism, strong nuclear forces and weak nuclear forces.
This unifying theory, which does not yet exist, would be known as the “theory for everything.” This theory would serve to understand both the relationships between the tiny particles of matter and those between the colossal stars of the universe.
Branches of modern physics
Modern physics is divided into two large branches, each of which in turn has much more specialized subfields.
- Quantum mechanics dedicated to the study of very small spatial scales, such as atomic and subatomic systems, or their interaction with electromagnetic radiation, always as observable phenomena. Its fundamental principle is that all forms of energy are released in regular units known as “quanta.” Among its areas of interest are nuclear physics, atomic physics or molecular physics, for example.
- The theory of relativity dedicated to the study of gravity, that is, physical events in both time and space, but always in relation to a variable observer. This means that time and space are not invariable but relative, unlike what classical physics maintained. This subfield of study is based on Einstein's two great theories: the Theory of Special Relativity of 1905 and the Theory of General Relativity of 1915. Its field of application is, mainly, that of cosmology, that is, the study of the universe as a whole and on a large scale.
References
- “Modern physics” on Wikipedia.
- “Classical physics” on Wikipedia.
- “Modern Physics” in ICL Didactica.
- “Classical and Modern Physics” in Science Encyclopedia.
