Every matter and energy is made of elementary particles. Elementary particles are categorised in fermions those carry matter, and bosons those carry forces. Further fermions are subdivided into quarks and leptons. Quarks participate in strong forces and form other particles. For e.g. proton and neutron is made of quarks. Whereas leptons don't participate in strong forces that's why leptons can be observed independently. The well known leptons is electron and its massive versions are muon and tau. They are electric charged leptons and carry a negative charge. As they are charged particles so they can be detected with the help of electromagnetic forces. Neutrinos are other leptons and they don't carry charge. Due to electrically neutral characteristics, neutrinos are affected by weak and gravity forces only. They are so less in mass that effect of weak and gravity forces can't be observed for neutrinos. Due to their masses, they travel almost with a speed of light. They are the least reactive leptons. That's why we could still find the neutrinos those were formed at the time of big bang.
They are so less reactive that it was very hard to know anything about them and they were called the ghost particles due to their isolationist behavior. It is also the reason thay they can travel almost with the speed of light without getting affected by gravity and weak forces. They are so less reactive that they can pass through stainless steel as easier as any comet travels through space. For a long time, they were considered massless particle but after their detection, it is found that they have a rest mass which is not more than a millionth of an electron's mass. Well, now it too is found that they exist in three discrete forms. They are electron neutrino, muon neutrino and tau neutrino. They are created during the beta decay of atomic nucleus. For e.g., electron neutrino is generated in beta decay with the corresponding leptons i.e. electron. Similarly, muan and tau neutrino are generated with their corresponding leptons.
First time the concept of neutrino was brought by W. Pauli in 1930 to conserve energy and momentum in beta decay. Later, the term neutrino was coined by E. Fermi. For a long period, neutrino was just an theoretical and undetected particles. Well, in 1956, first time direct detection of neutrino was carried out during the beta decay in nuclear plant.
Even though a little we know about this tiny particles but still there is need to know a lot. For this, there is need to detect the particles those are coming from our sun and universe.
For this purpose various observatory have been built across the globe by different countries. India is too planning to built India based Neutrino Observatory (INO) equipped with iron calorimeter (ICAL) detector. Even though process is in progress, it doesn't seem completion of that for now. Physicists think that detection of cosmic neutrino will led to understand this mysterious particles much more and eventually it will guide them to understand our universe better.
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