Question: Are neutrinos difficult to understand

Pierre Lasorak answered on 10 Nov 2014:

Hello
Yes neutrinos are difficult to understand! This is because we don’t see them often, in fact quite rarely! In the detector that I am talking about for example there are roughly 20 neutrinos that are interacting every day, but the background is 2 events per second. This means in the detector you see more than 150 000 things everyday, but out of these you only want to select 20! It’s like look for a needle in a haystack!
This comes from the fact that neutrino are not interacting a lot with matter. So when we want to tell something about neutrinos, we often have to face the fact that we have very few things to analyse. I’ll give you an example: say you want to analyse the level of English for people in village of 200 people. You can probably make up some question to test it and test everybody in the village. Then if somebody comes to you and says “all right, now tell me only for the 4 to 5 years old persons of this village” and you have 2 person of that age, then your results will be more uncertain than if you had more, say 20. This is what we scientists call “statistical uncertainties”. It means that if I had a bigger village, with more people in it, my result would be more accurate. And this happen a lot in neutrino physics.
But it is even worse than that, sometimes there are things that, no matter how big is your population, you can never calculate accurately. It it like if you take your ruler to measure the length of a pencil, no matter how many times you measure, with different rulers and different pencil, the error that you will make will always be of the order of the millimetre. There is also a lot of that in neutrino physics unfortunately, these are called “systematics uncertainties”.
So both these effects statistical uncertainties and systematic uncertainties make the neutrino hard to study (which is why it is so fun!)