You would not be mistaken to think that this is just another name for neutrons – and whilst they are similar to neutrons (as they have no electric charge), that’s where the commonalities would stop.

The simplest explanation of the neutrino is that it is a fundamental particle and that it cannot be broken down into anything smaller; it is what it is. The neutrino has no electric charge, and it has very little mass – so small that is it 500000 smaller than an electron. They are extremely abundant – there are billions of neutrinos all across the universe (including where you are right now). They are very unreactive, and they are very hard to detect – in fact there are millions of neutrinos going through you this very second, but you won’t know. They can easily pass through anything, whether it be from a simple apple to an entire planet, whilst causing basically no damage.

The origin of neutrinos in one sense is not as elusive as some of its properties – neutrinos are created due to radioactive decay. As a matter of fact, the existence of the neutrino was theorised whilst trying to explain a type of radioactive decay called the “Beta decay”. The understanding in the early 20th century was that if a heavy unstable nucleus were to become stable, it would undergo decay (i.e. the composition of the nucleus would change or the number of particles in it would change). At that time, it was understood that in Beta decay, a neutron decays into a proton and would also emit an electron. However, the energy that this “Beta” particle (i.e. electron) was supposed to have been less than what was measured: the theory didn’t align with reality – moreover it contradicted the principle of the conservation of energy. In response to this problem, a famous physicist called Wolfgang Pauli came up with the idea that there could have been another particle emitted with the electron at the time of the decay, which had not charge and had very little mass. Twenty-six years later, the theory of Pauli was found to be true when neutrinos were detected in an experiment conducted in South Carolina.

There are different type (or flavours) of neutrinos – moreover they can change between the three flavours – this is called neutrino oscillation. The three flavours are the electron neutrino, muon neutrino and the tau neutrino. These neutrinos are not easy to detect – the detectors are usually the size of a cricket pitch in diameter (they could be smaller or much larger as well). Moreover, it is still a matter of debate on whether there is a fourth type of neutrino exists.

What is a neutrino then? It’s something very small, incredibly fascinating and necessary to our lives.

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