Branches of physics

Physics is part of human knowledge that is dedicated to studying and modeling different phenomena that take place in our universe. This science is very broad and for this reason it has been divided into different branches. Physicists choose one of these areas when they finish their degree and specialize in it.

Physics is divided into different branches to facilitate the learning process . It is important to note that we have made a selection of the most relevant areas of physics. However, many of them coexist with each other. That is, there is no total separation.

Surely, as we delve deeper and deeper into our universe, new branches of physics will emerge. Many of the fields that exist today in the physical sciences emerged during the 20th century, that is, they are not more than a century old.

The field of classical mechanics or classical physics It is based on the laws that Newton postulated in his book Principia Mathematica in 1687. These famous physical laws describe the movement of bodies and the forces exerted on them.

This field of physical sciences also includes reformulations of classical mechanics known as Hamiltonian mechanics and Lagrangian mechanics that generalize Newton's laws and in many cases, these reformulations are more useful since they facilitate calculations.

Within this branch of physics, sub-branches are included that are also necessary to mention since they have been vital for the modern formulation of physics. These are:

The kinematics is the study of the laws of motion of bodies . Its objective is to predict the position, speed and acceleration of the study bodies. Some examples of laws studied by kinematics are uniform rectilinear motion (MRU), accelerated uniform rectilinear motion (MRUA), parabolic trajectories or simple harmonic motion, basic in the study of springs or pendulums.

We have seen that the kinematics studies the movement of bodies , but without understanding what generates this displacement of bodies. Dynamics is the field of classical physics that studies the forces that are generated on bodies. The main equation is the one provided by Newton's second law, the famous F=ma. From this expression we can analyze the forces on objects and the accelerations necessary to generate said force.

Statics is the branch of classical systems mechanics that studies the forces that act on rigid systems that are in equilibrium , that is, their acceleration is zero as no external forces act on them.

If you want to learn more you can read our interesting article on classical physics .

Quantum mechanics It is the part of physics that studies the smallest world in the universe , that is, to the atomic and subatomic world. To do this, it uses the famous Schrödinger equation that describes the temporal evolution of a quantum system.

Quantum physics has many applications within the physical sciences and technology themselves. It is essential in relativistic quantum mechanics, quantum field theory, quantum chemistry and the study of condensed matter.

In the world of technology it is also very useful. It is essential in quantum computing or in various areas of nanotechnology.

Relativity is the field of physics that includes two of the most important contributions to modern physics made by the famous physicist Albert Einstein.

This includes special relativity and general relativity.

Special relativity tells us that two observers can witness different realities . Therefore, physical quantities that were believed to be absolute, such as time, become relative.

This discipline of physics also studies the mathematical relationships between observers with different coordinate points through what are known as Lorentz transformations. The physical laws of two observers with a different point of view of reality do not change under these mathematical transformations. They are Lorentz invariants.

For example, Newton's laws do not depend on the coordinates of the observer, they are universal and independent of the person's point of view.

general relativity generalizes special relativity and adds time to the equation . It tells us that time and space are part of the same set known as space-time.

The basis of general relativity is Einstein's field equations that relate the density of an object to the deformation it causes in spacetime.

It explains gravity, which treats it as the geometric consequence of the curvature of the fabric of space-time.

To understand this discipline, advanced mathematical knowledge of differential geometry, tensor algebra and topology is necessary.

thermodynamics studies energy transfers and more specifically heat and work that can be generated with this. Thermodynamics studies systems at a macroscopic level and from its study derives the three famous laws of thermodynamics.

He First Law of thermodynamics It postulates that energy is neither created nor destroyed, only transformed. It is the principle of conservation of energy or what is the same, the internal energy of a closed system does not vary.

The Second law of thermodynamics discusses one of the most difficult terms to understand, entropy. This principle says that the total energy of the universe always increases. It is possible that locally the entropy decreases thanks to the contribution of external energy. However, the total entropy of the universe always increases.

The Third law of thermodynamics says that it is impossible to reach absolute zero (-273.15 ºC).

The field of thermodynamics uses these principles as a basis for deriving the rest of the equations.

Statistical physics is the study of physical systems from a microscopic and statistical point of view . We could say that it is the microscopic version of thermodynamics.

As we have seen previously, thermodynamics studies magnitudes at a macroscopic level. In statistical physics we see these magnitudes as an average of what happens at the molecular level.

For example, we can see temperature as an average of the kinetic speed of the particles. Therefore, by averaging this energy we can obtain the macroscopic variable that would be the temperature.

Another example is entropy. At the molecular level, entropy is defined as a magnitude proportional to the number of microstates of a system. Therefore, using statistical mechanics we can calculate all the microstates of a system and obtain the macroscopic variable, which in this case is entropy.

If we apply the laws of quantum mechanics to statistical physics, then we have quantum statistical mechanics.

The optics is the field of physics that studies the properties and behavior of light in different situations.

Some of these phenomena are refraction, reflection or dispersion of photons when interacting with matter.

Optics has many applications in our daily lives. For example, our glasses or the microscopes used in laboratories around the world are possible thanks to this branch of science.

It is also essential for me to write this publication and for you to read it since its principles are what make the transfer of information through fiber optics possible.

Acoustics is the study of the propagation of mechanical waves through different media. It basically consists of understanding the behavior of sounds and ultrasounds and how they affect bodies.

Within this branch of physics there are different sub-branches depending on the area of ​​science where the laws of acoustics are applied. Some of them are:

Study the different mechanisms by which animals use sounds to interact with their environment. For example, bats use ultrasound to orient themselves, dolphins use low and high frequency sound emissions for echolocation, or dogs bark to communicate.

Aeroacoustics investigates the sounds generated by turbulent fluid flows. A common application is to try to reduce the sound generated at airports by airplanes and reduce the stress that these sounds can generate for the inhabitants of places near airports.

The branch of electroacoustics studies the transformation of electrical impulses into sounds and vice versa. It is essential to be able to design quality speakers or microphones.

Musical acoustics attempts to understand the physics of sounds. Understand how these spread through instruments or human voices. In this way you can improve musical instruments and achieve better sound quality.

This area of ​​science focuses on studying the behavior of liquids and gases in motion and at rest. The motion of fluids can be described using the famous Navier-Stokes equations.

With these equations, highly complex phenomena such as the dynamics of the atmosphere, ocean currents or the air flow generated by airplanes can be described.

The Navier-Stokes equations are very complex and there are no analytical solutions for it. That is why numerical calculations must be used to approximate the solutions to these problems.

Meteorology is the field of physics that studies weather through fluid physics applied to the atmosphere. Through complicated calculations, often carried out on supercomputers, the behavior of the wind or clouds can be approximated and the weather in the coming days can be predicted quite accurately.

The biophysics It is the area of ​​knowledge that combines the knowledge of biology and physics to understand different phenomena that occur in living beings.

Experts in this branch of physics have to understand very well the relationship between these two scientific disciplines to understand in detail the biochemical processes that take place in living organisms. There are different branches within biophysics. Let's look at some examples.

Structural biology uses supercomputers to carry out complex calculations and simulate the dynamics of proteins or genetic material. Some applications of structural biology are the design of enzymes or drugs.

Bioenergetics aims to study the energy transfer that takes place through different metabolic pathways. The generation of energy molecules such as ATP or its use to carry out all vital functions are objects of study in this discipline.

Cosmology is the area of ​​knowledge that aims to understand the birth and evolution of our universe. Cosmology makes use of other branches of the physical sciences such as astronomy or astrophysics to describe the behavior of the universe as a whole.

Astrophysics makes use of theories from theoretical physics such as general relativity or statistical mechanics to describe astronomical objects. The creation or death of stars is an important field of astrophysics.

Although surely one of the most exciting is the study of objects as mysterious as black holes or the existence of other worlds accessible through wormholes.

Chemical physics is the area of ​​science that uses physical models to study chemical systems. It is very common to use quantum mechanics and statistical physics to study chemical reactions and understand how catalysis mechanisms work.

This branch also has a high application in structural biology where quantum methods are used for the study and optimization of enzymatic reactions.

Mathematical physics is the area of ​​science that aims to find mathematical tools that can be used to describe physical phenomena.

For example, general relativity makes use of complex tools of mathematics such as differential geometry or tensor algebra.

Other fields of physics such as quantum field theory use perturbation theory or abstract group algebra to model the fundamental interactions of nature.

Nuclear physics aims to understand the behavior of atomic nuclei and the energy they generate. Understanding nuclear fission made it possible to create nuclear power plants and generate energy in them.

Now, one of the main goals of high energy physics is to master nuclear fusion since it is a much cleaner type of energy than the nuclear fission that we have used to date.

Particle physics is the branch of physics that studies the different fundamental particles and their behavior. It uses the standard model to understand the evolution of these particles.

Interactions between particles are studied using quantum field theory which describes fundamental particles as excitations of quantum fields.

At CERN, experiments are carried out to try to understand these most fundamental particles from an empirical point of view and in this way confirm or discard the theoretical models that exist.

Geophysics is the branch of knowledge that uses physics to understand the phenomena of our planet, planet Earth.

Some of the main applications of geophysics are the study of earthquakes and the propagation of waves through the Earth's layer, the study of plate dynamics or the radiation and heat generation processes induced by events such as volcanoes.

Electromagnetism is the study of electric and magnetic fields and the behavior of the particles found in them.

Maxwell's laws unify the different studies on electromagnetism that existed and allow us to classically describe the forces of electric and magnetic fields and make predictions of how bodies immersed in these fields are affected.

Later, from the classical version of fields, the quantum version of fields was developed, giving rise to the branch that studies electromagnetism at a quantum level: quantum electrodynamics.

Quantum electrodynamics is one of the most precise theories we have today, reaching a precision with experimental studies of up to eleven decimals.

String theory is the area of ​​physics that proposes that everything is made up of small fundamental strings that vibrate in different dimensions. Depending on the mode of vibration, one type of particles or others would be generated.

This theory attempts to unify all existing theories to date. It is spectacularly beautiful since general relativity and many aspects of quantum mechanics naturally emerge from it.

It is the candidate to be the theory of everything, but there is still a lot of work to be done both physically and mathematically to complete this spectacular theory. To learn more I recommend reading our article on string theory .

Condensed matter physics is surely the branch of physics with the most scientists working on it.

It includes the study of the macroscopic properties and transformations of matter such as density, hardness or temperature.

This knowledge is used by engineers to create new technologies or improve existing ones.