Let’s talk about atoms for a second. We have known the structure of an atom for more than a century now. We know that an atom has a positively charged nucleus made of protons and neutrons in the centre and a cloud of electrons swirling around it. For now consider only the nucleus of an atom. We know that unlike charges attract and like charges repel. This means that the protons in the nucleus of an atom repel each other. As protons are packed in an extremely small volume to form the nucleus, they exert an extremely large force on each other. the force is approximately 90 newtons which is tremendous at the quantum scale. This force is even larger in heavier nuclei, but, we observe stable atoms all over the universe. This means that there is an inward force keeping the nucleus together. This force is known as the Strong Nuclear force.
The strong Nuclear Force
The Strong Nuclear Force is one of the four and the strongest of the fundamental forces in the universe. The other three include Electromagnetism, Gravity and the Weak nuclear. Electromagnetism is more than a 100 times weaker than the Strong force and the Weak Nuclear force is approximately 1 million times weaker than the Strong Nuclear Force. The Strong Nuclear force is a force experienced on the quantum scale. On the quantum scale, gravity is 1038 times weaker than the Strong Nuclear force.
The Strong Nuclear force also has the shortest range of the fundamental forces – around 0.5 to 3 femtometres (1 femtometre = 10-15 metres). This force is only experienced by protons when they are almost in contact with each other. When the protons are separated, even by a small distance, this force disappears.
Other than the nucleus of an atom, the Strong Nuclear Force is also observed in a second location. It is also present within the protons and neutrons. Both Protons and Neutrons are divided into smaller particles known as quarks. Out of the 6 known quarks (top, bottom, strange, charm, up and down), only two are involved in creating protons and neutrons (up and down). Protons are made of two up quarks and one down quark whereas the Neutron is made up of two down quarks and one up quark. These quarks are held together by the strong nuclear forces.
Exchange Particle of the Strong Force
Similar to how every force has its own carrier particle or exchange particle, like photons for Electromagnetism and W and Z Bosons for the Weak Nuclear force, there are gluons for the Strong Nuclear force. The gluon is a massless bosonic particle with spin 1. Quarks are held together by the exchange of these gluons between them. In simple words, gluons “glue” quarks together.
The strong nuclear force is one of the most captivating forces. It is the most powerful and also one of most important forces in the universe, for without it, the universe wouldn’t exist as we see it.