WHAT IS PHYSICS?

What is Physics?

To understand physics, we first need to understand the concept of Science and Natural Philosophy and why we learn them.

What Is Natural Philosophy?

Just assume that whatever the first human got the chance to enter this world, that newly existing human being who knew nothing about this world when observing nature, air, water, land, sky, and stars, what would be his feelings? Would he be happy or terrified? Now just think of a question you are the first human being on this planet. What if you come across a lion?  You know nothing about it. What would be your feelings? Would you be afraid of it? No, you won’t. Human beings become happy or afraid of something when they know its past. So if you don’t know the past history of lions, they will not fear you or make you happy. Similarly, when the first human observes the natural processes and the entire system. The feeling that arose inside him was neither terrifying nor frightening. Instead, it was the feeling of curiosity. He was urged to think why am I here? How this entire universe is working?  All these questions puzzled human beings and their curiosity to explore things increased. This curiosity let the man explore different things in his surroundings. As the man explores something he wrote it down so that he might not forget anything. In this way, the man gathered a bulk of knowledge. It was a time when knowledge of science didn’t exist. All the things that man studied was considered as the study of nature and so this study was known as Natural philosophy, not science. The person studying natural philosophy is known as a philosopher instead of a scientist. As you might have heard about the Greek philosopher Aristotle. If he exists today, he will be known as a scientist.

Main branches of Natural philosophy:

As more and more people get engaged in natural philosophy, their knowledge exceeded up to an extent that it becomes almost impossible for a single man to study the whole natural philosophy. This was the period that the philosophers of the time realized the fact that natural philosophy should be broken down into two sub-branches that are:

1.       Biological science

2.       Physical Science

Biological science: As the name suggests Biological science is the study of living organisms like human beings, animals, plants, algae, fungi, bacteria, etc.

Physical science:  We see many things in our surroundings like stars, moon, sky, stones, seas, oceans, etc. All of them are non-living things and their study is known as Physical Science.

Branches of physical science:

 Since man is always curious to explore things and discover the secrets of the universe man could not stop himself to divide this vast field of physical science into further subbranches known as:

1. Physics

2. Chemistry

3. Geology

4. Astronomy

Now in chemistry, you will study chemicals and chemical reactions. Geo means earth, so, geology is the study of the earth. Similarly, in astronomy, you will study heavenly bodies like stars, planets, etc. But our blog is related to physics therefore we will now see the definition of physics.

Definition of Physics:

"Physics is the branch of science that deals with the study of matter, energy, and their mutual relationship."

If you want to get a firm understanding of this definition, you need to understand three terms discussed in the definition that are 'Matter', 'Energy', and 'Their mutual relationship'. 

What is matter?

There are two conditions to check whether the body is a matter or not. The body is said to be matter if and only if it has:

1.  Mass

2. Volume (physical)

For example: If I want to check whether a pencil in my hand is a matter or not? 

I must apply both checks. First I will check the pencil for its weight. So yes, it has some weight. Then I will check it for volume. It is occupying space which indicates that it has some volume as well. This confirms that the pencil is a matter. Since the pencil is solid this means that all solids are matter. Let us check whether a liquid is a matter or not. 

Suppose I have water and I want to know if it is matter or not?

 I will apply the same check here. I will check it for mass and I know that water has weight. I will apply the next check which also results in positive because water also occupies space. This means that water or any other liquid is also a matter. 

Now let us check the same thing for gases. I knew that air surrounds us. So for instance I assume that there is some air in my hand and I am eager to check whether it is a matter or not. 

Firstly, I will check its mass. I will find that apparently, it has no weight. Then I will check it for volume and again I will say that it has no volume. So I may think that air is not a matter because I cannot feel its mass and volume. Let us ponder over the situation deeply. If an ant is sitting on your head but you can not feel its weight so does it mean that the ant is not sitting on your head? You will say that the ant is sitting on my head but its weight is as much less that cannot be felt by me. The same is the case for air. It is present on my hand but apparently, it seems to be massless. But if I have some extraordinarily efficient and sensitive instruments I will come to know that air also has mass. Now let us apply the second check. If I have a cylinder and I want to get it filled with air. Can I keep filling the cylinder and the gas or air will not occupy any space i.e., the cylinder will not be filled? You will say No. Because there is a limit up to which you can fill the cylinder else it will burst. This means that air also has volume. Hence we find that air or gas is also a matter. This means that Solids, Liquids, and gases are matter. They are called Physical states of matter or simply states of matter.

What is Energy?

If you look around yourself you will find yourself surrounded by matter. Now think of a thing that is a non-matter. So just imagine heat rising from a hot body. Is it a matter? Does heat have mass? Does it occupy space? You will find the heat a non-physical thing. In the same way, if I talk about sound, does it occupy space? If I keep on talking continuously, the room will get filled with sound, and will burst? You will say no, this can not happen. This means that sound is also non-matter. So if heat and sound are non-matters so what are they? They are Energies. Heat, sound, light, wind, gravity, etc. all are non-matters and non-matter is called energy. 

What is the relationship between matter and energy?

Let us consider an atomic bomb. What does it do? It converts Uranium (a radioactive substance used in atomic bombs) which is matter into heat which is energy. This means that the atomic bomb is a process that can convert matter into energy. This result tells us that there is some relationship between matter and energy. In the same way, energy can also be converted into a matter which is called Pair Production. In this perspective physics is not only the study of matter and energy but it is also the study that involves the conversion of matter into energy and vice versa. 

Hence we concluded that everything around us is either matter, energy, or their mutual relationship. This means that in physics you are studying everything, you are studying the whole universe under this single subject. That is why we say that Physics is the most fundamental science. Furthermore, it is an experimental science. You can not state anything unless you have proven it experimentally.

Branches of Physics:

Branches of physics are divided into two basic categories:

1. Pure Branches

2. Overlapping branches

Pure Branches:

These include mechanics, optics, nuclear physics, etc. In this course of study, you are only concerned with physics.

Overlapping Branches:

These are branches in which you have to study physics along with other sciences. These include biophysics, medical physics, astrophysics, etc.

What are the main frontiers of physics?

Frontiers mean levels, therefore frontiers of physics mean levels on which we study physics. So, there are three main frontiers of physics:

1. Study of extremely large objects:

It includes the study of the universe, the formation of the universe i.e., the Big Bang occurred 20 billion years before, Radio telescopes, etc. 

2. Study of extremely small objects:

It includes the study of atomic and sub-atomic particles like electrons, protons, mesons, etc.

3. Study of middle-size objects:

It is also known as the study of complex matter. It includes all things with sizes ranging from a molecule to the size of the Earth. The human study is also involved in the same frontier.

What do we investigate in Physics?

We investigate many things in physics. Some of the most essential things are:

1. Laws of motion

2. Structure of space-time

3. Interaction of matters

4. Interaction of radiation with matter

5. Different types of forces

We will be discussing them in further blogs. Till then keep learning and keep exploring.