4. Strong force and Nuclear force

There is a reason why I ordered the forces starting from Strong force to Gravitational force. It's because of their purpose and how they contribute to form things that we see around us, including us. Once we explore the forces in detail, you would also understand the same.

Before proceeding into details, let's understand the reality. At any given space & time, all these fundamental forces are always acting on each other. We can also says that any activity or incident that occur in this universe is a final outcome of the resultant force derived from all four participating fundamental forces.

Let's see why it strong force is. Considering the above fact, we see this force has more control and cancel out all other forces that act on a quark or hadron. To understand it better, first we need to understand what this strong force does. This force acts on the nucleus and it has two different forms. 1. As strong force between the quarks. 2. Residual strong force between the nucleons. Nucleon is the common term for protons and neutrons. Hence, this residual force is also called as 'Nuclear force'. Let's get into the details now.

Quarks:
It's a sub-elementary particle and it also consists sub-elementary particles called 'gluons'. They get together and form the elementary particles called hadrons. Protons and Neutrons are examples of hadrons.

Strong Force:
In other words, when quarks and gluons are shared between hadrons, we can say that there is the strong force acting. One specialty about this force is that unlike any other force that we studied in physics, it's strength is proportional to the distance between the two particles! Yes, the force increases by distance. That's interesting, isn't it! That means when the hadrons come too close it repels each other or the force becomes weak. This helps to keep the hadrons not too far and not too close to each other and ultimately form the nucleons.

Nuclear Force:
We had seen that the strong force is acting between hadrons sharing quarks and gluons. If this is strong force, then what is holding the nucleons? Population of neutrons and protons is always conserved because in a nucleus, the number of protons and neutrons are always same! As a result of such a strong force inside nucleons, it extends it's field outside the nucleons and acts between nucleons as a residual force. This force also increases by distance as it's simply an extension of the strong force. It holds the nucleons not too far and not too close to each other. Hence it forms the nucleus at the center of the atom with high density.

As I said above, any activity or incident that occur in this universe is a final outcome of the resultant force derived from all four participating fundamental forces. So, considering all other forces, this force has to be the strongest one in order to form the sub-atomic particles as a first step of the creation process, the creation of an atomic nucleus!