What is Physics?

An introduction to physical quantities.


In this post, we are going to bring to you a novel definition of physics which you might not have read anywhere else. Also, the following description will prove to be insightful for an absolute beginner or layperson.

What is physics? Physics is one of the oldest branches of science in which we study the relationships between physical quantities. Now, what is a physical quantity, you may want to know.

A physical quantity is any entity which has some "physicalness" to it, meaning, you can experience or visualize it through sense. In addition, you can also measure its magnitude with an instrument, hence, quantity meaning "how much".

Let us understand with examples.

Say you touch a hot cup of tea. Then, your hands instantly sense the hotness of the material. This hotness or coldness can be measured with a thermometer. The physical quantity in this case is called the temperature of the material.

what is physics?
The SI base unit of temperature is Kelvin

When you look at a marvelous building such as The Empire State Building in New York City, you begin to admire its height, size and its overall structure. The physicalness of it is distinctly visible to your eyes. The quantities involved in this case are length and volume, measured in m and m^3 respectively.

Take "time" for example. In this case, we experience the passage of time as we go through our lives. As the sun moves across the sky, shadows change in direction and length, so a simple sundial can measure the length of a day. Thus, time is a physical quantity.

Mass is another example of a physical quantity. It is a measure of an object's "resistance to acceleration" when a net force is applied upon it. So, it is harder to lift an elephant baby than it is to lift a human baby.

what is physics?
The SI base unit of mass is kilograms

So, what is not a physical quantity?

  • There is no physicalness to it
  • It is not measurable

Therefore, joy, love or anger are not examples of physical quantity. These are in fact examples of internal feelings having no physicalness and no measurability. A physicist goes through all of these emotions in his/her personal life without ever studying them professionally.

A neuroscientist on the other hand has a specialized knowledge in the field of physiology, biochemistry, anatomy and molecular biology of neurons and neural circuits and especially their association with behavior and learning.

what is physics?
A study of physical nature

When you experiment in a physics laboratory, you are working with two or more physical quantities and their interrelationships. These relationships are called laws. For example, consider "F=ma" which is a relationship between vectors force and acceleration.

Usually, the result of experiment is a number followed up by a proper unit. It is important that you learn to write your result in the correct units or otherwise, things can get bad like really bad:

On December 11 in 1998, NASA launched the Mars Climate Orbiter to study the environment of planet mars. However, the spacecraft was destroyed while attempting to enter martian atmosphere because engineers at the manufacturing plant forgot to convert data on engine thrusts from pounds into the SI unit of force (Newton) before giving it to NASA.

Therefore, using the correct units is important.

what is physics?

Nobel Prize winning American physicist Richard Feynman has compared physics to chess. He had famously said, "You are observing an ongoing chess game and from observations trying to discern the rules of the game. The rules of the game are what we mean by fundamental physics."




To summarize, physics is a prodigious gameplay, an interaction between physical quantities. We are merely the spectators and through a combination of sensible hypotheses, mathematics and experiment, attempting to describe the game while using its rules to our advantage.

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