The word atom means “indivisible, ” which meant that it was thought to be the smallest thing in existence. It was the primary building block of all matter. However, as science techniques improved, we found that the atom consisted of a nucleus consisting of protons and neutrons. Around the nucleus electrons circle in various fixed orbits. Most of the mass of an atom is contained in the nucleus. The neutron has no electrical charge but accounts for most of the mass. A proton carries a positive charge and an electron carries a negative charge. Further years of investigations showed that protons and neutrons consisted of even smaller particles called quarks. When the electron came under further investigation, it too, proved to be one of a number of other fundamental particles called leptons.
Another sub-atomic particle is the neutrino. It is similar to an electron but carries no electrical charge. They are extremely small and travel around close to the speed of light. They very rarely interact with anything. This is good if we consider that trillions of neutrinos pass through our bodies every second without “hitting” anything. Now, that is small!
From 1930, it was suggested that a particle such as the neutrino must exist. But, it was not until 1956 that the neutrino was finally detected in the laboratory. There is still a lot we do not know about neutrinos. For example, we should be able to predict roughly how many neutrinos are projected out from the Sun’s nuclear fusion reactions. But, the number measured falls far short of what was expected. Theories on why this might be so, include the possibility that there is more than one type of neutrino. There may be some with mass and others without any mass.
There is another theory which says that perhaps neutrinos make up Dark Matter. Our measurements of the mechanics of galaxies indicate that there is not enough matter in the visible universe to create sufficient forces of gravity to hold everything together. It is an interesting theory but we are still in the dark regarding both Dark Matter and Dark Energy.
John Pullen 