In my previous post, we had seen how Strong force is contributing to the formation of Nucleus. Now what? To form a complete atom, we need set of electrons swirling around the nucleus. So, our next objective is to understand how an atom is formed on top of the nucleus.
Particle physics say that 98% of the total mass of an atom is from the mass of its nucleus! So, once the nucleus is formed, it becomes heavy. Once again, nature exhibits its intelligence here. Neutrons are basically heavier (0.2%) than protons and it has no charge or it is neutral in charge. So, neutrons start releasing part of its mass (0.2% of its mass) in the form 'W− bosons' with the energy of 1.29 MeV. Since W− bosons are unstable they immediately break down into a negative charged particle and a positive charged particle. They are nothing but an electron and an anti-electron neutrino!
We can indicate the above reaction by the below equation. This process is called 'Beta decay'.
- n0 → p+ + e− + νe
There are two important points to be observed:
1. Neutron gets transformed into a Proton.
2. An electron is created out of Neutron.
So, as per the above reaction, in a nucleus, all the neutrons should have transformed into protons and all the electrons might have been created simultaneously. Ideally we would think that nucleus would then be filled only with Protons and no neutrons would exist; but in every atoms, population of protons and neutrons in it's nucleus is same. How is it possible?
In a same way how neutron gets transformed into a proton, a proton can also get transformed into a neutron if it receives an energy of 1.29 MeV. This is a reverse process of neutron's beta decay. In the early stages of big bang when the energy was so high, protons and neutrons were able to freely get transformed vice versa and so there were equal number of protons and neutrons in the atomic nuclei.
Sometime, when the size of the nucleus grows too big or too heavy, strong force start repel hadrons from each other due to collective positive (+) charges of protons in the nucleus. At some point, the nucleus gets broken into multiple smaller nucleus; eventually weak forces plays its role and creates smaller atoms out of those smaller nuclei by release electrons.
It's simple and obvious to realize why the electrons swirl around nucleus instead of traveling into the space. Yes, it's the attractive force that is generated between positively charged protons that is inside the nucleus and the negatively charged electrons that swirls around the nucleus. If you ask me what made electrons to swirl instead of just hang around the nucleus, I would surmise that it could be due to the effect of Big Bang that bursts out and left each and every subatomic and atomic particles in this universe to spin as a result of its kinetic energy and it's angular momentum!
Why is this called as weak force? because it is weaker than strong and electromagnetic forces. However without this force, there was no chance for the formation of electrons, eventually, atoms. Also this force plays a vital role in keeping the pace, at which Sun burns helium, very low and so Earth could get enough time to support the formation of lives. If such force would be stronger, then Sun might have burned all the helium very early, probably even before lives might have been formed on Earth. Hence weak force is as unique and important as any other fundamental force in this universe!
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