What is Physics?

Mattye Brecht, Elizabeth Friedl
  • Author
    Mattye Brecht

    Mattye earned an undergraduate in biology with a minor in chemistry from Colorado Christian University and a Masters in Secondary Education from University of Colorado at Denver. She has taught 5 years of high school. She has also worked in pathology and food manufacturing labs.

  • Instructor
    Elizabeth Friedl

    Elizabeth, a Licensed Massage Therapist, has a Master's in Zoology from North Carolina State, one in GIS from Florida State University, and a Bachelor's in Biology from Eastern Michigan University. She has taught college level Physical Science and Biology.

What is physics? Is physics science? Learn the definition of physics and the relation between physics and science. See the various branches of physics and learn their importance. Updated: 07/21/2021

Table of Contents


What is Physics?

The definition of physics is the study of the physical plane of matter, motion, force, and energy. The root word of physics is Phys- and is Greek for "nature" and "natural order." Physics itself is studying the natural world and the interactions between objects and energy in any given environment.

In ancient Greece, early scientists did not have anything more than their senses to help them study the world around them. These scientists often studied their environment through touch, taste, smell, sight, and sound. During the 17th century, people like Galileo, Copernicus, and Newton revolutionized science with breakthroughs of physics through the laws of gravity, the sun-centered theory, and the discovery of atoms. With modern technology and advances in the scientific method, physics incorporates things that are not observable to the naked eye.

Is Physics Science?

Is physics science? This question may seem obvious, but is physics considered science or art? Science is defined as a compilation of observations, predictions, and organizational methods of testing the universe. Art is an individual's expression of their experiences through creative skill.

The answer is yes; physics is a science. Since physics concerns itself with observations and testable predictions about the physical universe and not someone's opinion of said universe, it is most definitely a science.

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  • 0:01 What Is Physics?
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Branches of Physics

The physical universe has many moving parts and is not simply what is observed through the naked eye. Physics is also how the most prominent objects interact with the smallest and everything in between. Since physics is such a broad subject, it has to be broken into smaller categories or disciplines, also known as fields of study.

There are three main categories of modern physical study:

  1. Classical physics covers electromagnetism, classical mechanics, thermodynamics, and statistical mechanics. Classic physics provides action and reaction, showing how objects acting in a system will interact with other objects in that same system.
  2. Relativity has two types of study; there is general and specific relativity. General relativity deals with how the law of gravity interacts with objects; this has a significant bearing in astrophysics and astronomy. Special relativity concerns how objects interact in a vacuum or are devoid of gravity.
  3. Quantum physics is the most recent course of study in physics. Here, scientists study quantum mechanics, quantum statistics, quantum electrodynamics, and quantum field theory. This branch deals primarily with objects at an atomic and subatomic level. It answers questions like, "what makes a proton different from a neutron?"


The study of mechanics is both broad and specific. Broadly, mechanics study objects, their motion, energy, and how they interact with other objects and energy. There are two sub-branches of mechanics, quantum mechanics and classical mechanics.

  • Quantum mechanics, studies how atom and subatomic particles act and react with one another; similar to how the atom is held together, what happens if two atoms collide? What makes up the atomic particles; how and why do two atoms bond; what holds together millions of atoms into a complex compound?
  • Classical mechanics follows the same principles as quantum, at a much larger scale. Examples of classical mechanics would be predicting planetary orbits or the path of a bullet, black holes, friction between a car tire and the road, why water has surface tension, or the arc of a baseball as it is thrown across home plate.

Mechanics can explain a minor interaction, like why an electron is attracted to a proton, and the most significant interaction, like why the earth orbits the sun.


One of our two most important senses is that of sight. In physics, the study of light and its properties is called optics.

One reason light is a fascinating study subject is that it contains the properties of a wave and particles. Additionally, electromagnetic waves make up light, meaning it has properties of electricity and magnetism and does not need a medium to move.

There are several different types of light:

  • Visible
  • Ultraviolet
  • Infrared
  • X-ray
  • Radio Waves
  • Gamma Rays

Prisms take visible light and split it into different wavelengths

Prisms take visible light and split it into different wavelengths


Similar to mechanics, thermodynamics covers a broad range of studies. Thermo-heat and dynamics-relationships is the study of relationships between heat and other forms of energy.

For example, due to oceans covering a significant part of Earth, Earth does not experience large swings in overall temperature because water holds in heat better than dirt and keeps life going on this planet. Fewer oceans would result in temperatures between night and day, summer and winter being too large to sustain many life forms. The relationship between heat held in water versus heat given up by water is vital to study and understand.

There are three laws of thermodynamics, which govern the interaction between heat and energy in a system:

  1. First Law: Energy can change its form, but not amount.
  2. Second Law: Entropy of any system ascends towards chaos or the loss of useable energy.
  3. Third Law: Entropy is at its smallest when the temperature of a system approaches absolute zero.

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Frequently Asked Questions

What are the 7 branches of physics?

The seven branches of physics are optics, electromagnetism, relativity, thermodynamics, acoustics, quantum physics, and mechanics. There are smaller categories within these broad areas.

What is physics in simple terms?

Physics is the study of the natural world, both seen and unseen. It is a broad subject that can be broken down into specific areas of study, like electromagnetism and optics.

What is physics and why is it important?

Physics is an important area of study because it allows scientists to understand the world, the environment, and the interactions between objects in a system. Understanding our world allows for appreciation, conservation, innovation of the world around us.

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