What is Physics? (The Study Of)

First of all, physics is defined as the study of matter in relation to energy. Hence, its primary goal it to try to unravel the interactions between the two. In order to do this, it studies the entire universe from the most massive cosmic structures to the smallest sub-atomic particles. By doing so, it forms the basis of the other sciences such as chemistry, astronomy, and biology.

For many, physics is a mysterious abyss of impossible information. For others, it is an incredible source of enlightening discoveries. And both are right. It’s always been a tough subject, but has also consistently provided a wealth of progress for society. For those wondering what physics is and how it affects us all, this article gives a quick rundown.

The Fathers of Physics

Before diving into the scientific details of physics, it’s good to be familiar with the people who brought the field into being. Galileo, Newton and Albert Einstein are all referred to as the fathers of physics.

First, Galileo Galilei made contributions to observational astronomy at the turn of the 17th century. He observed through telescopes the phases of Venus, Jupiter’s largest moons, and even sunspots. He also helped spread science to the masses during the Scientific Revolution.

Isaac Newton then came up with the renowned laws of force and motion in the next century. He proposed three laws to describe the concepts, and these laws form the basis of classical mechanics. The story goes that he was sitting under an apple tree when one of the apples fell and hit him on the head. This seemed to knock an idea into his head: the idea of gravity.

Albert Einstein came last at the end of the 19th century, and is recognized for many contributions to both math and physics. Most people have heard of or even used his mass-energy formula of e=mc^2. He also came up with the theories of special and general relativity, and discovered the photoelectric effect.

Main Areas of Physics

Physics has a number of topics and fields, but there are eight main branches which you should know about. In fact, you’ve probably already heard of them, and maybe even took some classes on them in high school or college. Each branch is generally classified by properties of matter on different scales. So, high energy physics are lumped together, as are the very small, the very big, the very energetic, and so on.

Classical Mechanics

One of most fundamental branches of physics is classical mechanics. It’s the one that gives us many of the classic equations, laws, and principles of motion and energy. It was originally created by Sir Isaac Newton in the 17th century, making it the first branch of physics ever discovered. Thus, all other branches of physics build upon the foundations of classical mechanics.

Through classical mechanics, physicists can describe the motions and interactions of objects and systems. Whether a rocket leaving orbit or an apple falling on your head, this branch accurately describes most normal objects.

However, there is an emphasis on “normal.” Some things find themselves outside the domain of classical mechanics. These include things larger than a planet and smaller than a molecule. “Normal” objects should also be close to room temperature and going much slower than the speed of light. Once calculations go beyond these constraints, classical laws and principles start to not work so well. And that’s where the next branches come in.


For those often very large objects going very fast, relativistic mechanics is a better fit than classical. As physicists started looking to the stars through telescopes, this branch of physics became increasingly important.

Albert Einstein first came up with the special theory of relativity and then with the general theory. The first considers objects with constant motion, while the latter considers those which are accelerating. General relativity also considers how space can “curve” when interacting with gravity and time. This currently makes it the most accurate method of predicting gravitational interactions.

Quantum Mechanics

On the other end of the spectrum, this branch became more important as scientists started looking more through microscopes. It deals with the physics of the very small, on the scale of atoms and electrons.

What’s interesting about this scale is the breakdown of classical mechanics rules. They can no longer describe the physics of an object like an electron existing at a certain point in space—because electrons don’t really exist in a certain point in space. Rather, they exist in clouds of probability of being in a certain point at a certain moment.

Unlike the two branches above, no single scientist can take credit for the creation of this branch. Instead, a number of scientists contributed to the three principles that form the foundation of it. These principles are quantized properties, particles of light, and waves of matter.

These principles were revolutionary, and they were verified through experimentation in the early 20th century. Quantized properties meant that certain properties could only occur in certain amounts. Particles of light meant that light can behave as a particle, and likewise waves of matter meant that matter can behave as waves.

Thermodynamics and Statistical Mechanics

Thermodynamics starts to look at the properties of matter and how they relate to the transfer of thermal energy. Thermal energy is the energy of vibrating or moving molecules, and we sense this as heat. It also has various ways of converting to and from other types of energy. As is does this, it affects matter in different ways.

This branch of physics distinguishes between heat (the movement of particles) and temperature (the amount of heat transferred by a substance). Another important concept is specific heat (or specific heat capacity). It is the amount of heat needed to increase the temperature of a certain amount of matter by a certain amount. Thermal conductivity is then the rate that heat passes through certain material, and Newton’s Law of Cooling describes the exponential decay in temperature difference as an object cools. Other topics in the field include heat transfer, the Carnot cycle, and entropy.

Probably the biggest parts of this branch are the four laws of thermodynamics. They were originally just three laws, but the fourth (that is, the “zeroth”) was added when it was determined that it was so fundamental no one had thought to include it before. This Zeroth Law describes bodies in thermal equilibrium. The First Law then talks about heat transfer, and the Third Law talks about entropy and waste energy.


This branch of physics looks specifically at electrons and the forces and interactions between them. Electrons are the small electrically charged particles that form part of an atom. The electromagnetic force occurs between them. It is made of electric and magnetic fields, and carried by electromagnetic fields. From it, we get electromagnetic radiation, which includes light itself.

The electromagnetic force is one of four physical forces that scientists consider fundamental. The other three forces are the strong interaction, weak interaction, and gravitation. Electromagnetism is interesting because it and gravity are strikingly similar. Gravity attracts objects by an inverse square force, and magnets do as well. However, magnets can also repel one another, whereas gravity only attracts.

Unique Fields and Forces of Electromagnetism

Additionally, while gravity seems to warp space and time to create its attraction, electromagnetic forces reach out to each other with the fields mentioned previously. Fields of electricity surround charges, and magnets have magnetic fields.

The relationship between these two distinct fields is then seen when they move. When moving, electric fields create magnetic fields, and moving magnetic fields create electric fields. This revolutionary discovery vastly changed the field of physics and particularly astronomy.

Atomic, Molecular, and Optical Physics

Also known as AMO, these three topics are all related because they study the properties of atoms, molecules, and light. As mentioned above, light have a peculiar property of being both a wave and a particle, and it also interacts with matter in interesting ways. These interactions between matter and light as well as matter with other matter are the focus of the field.

Interactions of interest include absorption, emission, and scattering of light (electromagnetic radiation) from molecules and atoms. The main tools and methods for this process include the use of spectroscopy and lasers.

These various topics also frequently consider molecules and atoms in isolation from one another on very small scales.  This helps simplify the study and results by reducing time scales significantly. The field provides underlying theories for atmospheric physics and plasma physics. However, atomic physics should not be confused with nuclear physics. The two are separate in that atomic physics considers the nucleus and electrons rather than just the nucleus.

Condensed Matter Physics

Condensed matter is really just a fancy word for solids and liquids. Such condensed matter surrounds us all the time, so we usually take it for granted. This branch of physics, however, studies these types of matter, especially in systems with many interacting pieces.

In these types of complicated systems, exact calculations can be impractical or even impossible. Topics that the field explores include why some elements have different properties than others and why they interact and behave the way they do.

This branch of physics is also unique in that it affects our daily lives quite a bit. The field makes advances in areas like electronics and storage or transfer of information, therefore contributing to the rapid development of electronics. It also has huge implications for the field of medicine, medical technology, and unique materials.

High Energy and Particle Physics

In this field, scientists look at the most basic parts of matter and even antimatter. They study the forces that govern the interactions between these particles and are able to identify new particles that we didn’t even know existed. For instance, leptons, quarks, bosons, Z particles, muons, neutrinos, and more are just part of the list of particles they work with.

Physicists in the field have been able to shed light on some of the inner workings of the universe and reality. For example, we now know that quarks and leptons are the basis of all normal matter that exists in the Universe. We also know that bosons carry and mediate three of the four fundamental forces of nature mentioned above.

These discoveries come from the use of enormous accelerators like CERN or the Large Hadron Collider. These machines can create particles that existed during the first stages of the Universe but that don’t usually show up in daily life today.

Some of the remaining mysteries left for physicists in the field include dark matter, dark energy, antimatter, and unification of gravity.

Learning Physics

Physics equips learners with a broad understanding of the physical environment. It aids them in developing critical thinking and quantitative reasoning skills, empowering them to think critically and creatively towards solving the worlds’ scientific problems.

It accomplishes this by putting emphasis on experimental methods. Hence, making measurements, doing mathematical analysis, and quantifying the physical world are very important. If something can’t be proven (repeatedly), then it’s not considered a scientific fact. Thus, learning math and the scientific method are crucial for success in physics.

Benefits for Today and Tomorrow

Physics forms a central part of our lives, as indirect as it might sometimes seem. Some examples of helpful inventions that owe their existence to physics include microwaves, cell phones, cars, and refrigerators, just to name a few.

The field also has many applications in healthcare that can help extend our life expectancy or improve our quality of life. In this area, it has played a vital role in the improvement of diagnosis and treatment of diseases such as cancer. There is even a potential tumor treatment which scientists call Hadron therapy!

Physics also plays a significant role in the future human progress by generating critical knowledge needed for future technological advances. This includes advances in space travel and general knowledge about the universe. Physics continues to evolve as more and more discoveries come to light, so it’s easy to see the potential it has to transform the world.

About David A. Smith aka Dave
About Dave

David Smith (Dave) has a B.S. and M.S. in Mathematics and has enjoyed teaching precalculus, calculus, linear algebra, and number theory at both the junior college and university levels for over 20 years. David is the founder and CEO of Dave4Math.

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