Neutrinos: Athens- North Pole in no time

 Created on Sunday 04 Jan 2009
by Άννα Χριστοδούλου

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Every time we stroll around or we rush to go at work, we don’t even suspect that at the moment, and every single moment, our body is been penetrated by trillions microscopic particles called neutrinos. More specifically, our body is been penetrated by ten trillions neutrinos per second and before we even think of this fact, the neutrinos have already flown away and probably reached the Northern Pole, having almost the light speed (300.000 kilometres per second).

What is a neutrino?

A neutrino is the smallest quantity of matter the human mind can conceive. They are called as the ghost- particles, because their main characteristic is that they cannot be easily found. That is because they don’t have any electric charge and they are terribly microscopic, with infinitely small mass. Consequently they react very weakly with the matter, making their detection very difficult.

The neutrinos detection long story

The decade of 1920 found the scientific community extremely puzzled. For the first time, one of the most undisputed till now laws of Physics, the Energy Conservation, was henceforth under questioning. The energy is not lost and is not presented from nowhere. What had happened then therefore that made famous physicists despair?

At that time scientists dealt with nuclear decay. When the nucleus of the elements is very big, it subsequently isn’t constant and it emits some particles in order to get stable and “survive” in the nature. In a nuclear decay type though, which is called the b – decay, there seemed to be a problem. During the b- decay the nucleus emits a b particle, that is to say an electron. There should be a specific energy rate after the decay, according to the theory, but there emerged many different energy rates, none of which verified the Energy Conservation.

Having no other logical explanation to this mysterious behavior of the nucleus, Niels Bohr, one of the founders of quantum mechanics, reached to the following conclusion: “At the present stage of atomic theory, however, we may say that we have no argument, either empirical or theoretical, for upholding the energy principle in the case of b-ray disintegrations.”

This odd opinion of Bohr was the only reasonable explanation for b-decay, when Pauli, another famous physicist for his contribution to the atomic theory, made the “Neutrino Hypothesis” in 1930. He claimed that there existed a particle which had infinitely small mass and reacted with the matter terribly weak and so it couldn’t be found. He betted a box of champagnes that neutrinos would never be detected.

This particle, he supported, played a huge role in b - decay and verified the Energy Conservation, by making up the energy shortage. The neutrino history had just begun. Four years later, Enriko Fermi studied too the b decay and renamed the mysterious particle “neutrino”, after Pauli’s “neutron”. In 1956 Frederick Reines and Clyde Cowan managed to detect neutrinos and Pauli receive a letter with their results and therefore was made to pay the bet that had put 26 years earlier, sending them a box of champagnes!

Interesting facts about neutrinos

Yet, there is!

Every second ten trillion neutrinos penetrate us. Is there a chance that one of them reacts with our body? Yes, there is! We don’t have a clue what will happen in this case as it has never been observed something like that. The probability though exists, even if it is extremely small!

Do the neutrinos have taste or color?

Yes, they do! We use the words “taste” and “color” to describe the different neutrino types.

Where do the neutrinos come from?

From everywhere! They come from everywhere and they go everywhere! They come directly from the Big Bang (300 neutrinos per cubic centimeter come from the Big Bang), they come from the sun, they come from supernova explosions and we can produce neutrinos too in the accelerators!

Nowadays big experiments are set in order to detect neutrinos in many places around the world, including Antarctica, France, Greece and America. Scientists are particularly interested in neutrinos from distant astrophysical sources.

The above text is a translated abstract of “How can we catch neutrinos”, a simplified physics article written by Anna Christodoulou and published in “Discovery & Science” magazine, February 2006.