Hello World! My name is the electron neutrino and my symbol is \nu_e
. I have two sisters, the muon neutrino \nu_\mu
and the tau neutrino \nu_\tau
, but we all look very much alike. We are often just called neutrino \nu
because people don't bother specifying which one of us it is they are referring to. (We don't really mind.) You can see in the figure below all the known fundamental particles. (We, the three neutrinos, are on the top). The only fundamental particle in this list that we have seen earlier is the electron denoted e. The lines tell you who talks to whom (but you don't need to worry about it for now). We all have tricky family relationships!
- \nu_e
: So, I just wanted to introduce myself. I think you may not know much about me but I am all around you all the time. The sun emits light, as you know and see, but it also emits me, the electron neutrino. In fact, from the sun alone, there is about 2\times 10^{14}
neutrinos going through your body every second.
- S: Really?
- \nu_e
: Yes really. Count 1 s. Zip 10^{14}
neutrinos went through. It does not matter where the sun is (during the night, we go through the Earth and then through you).
- S: Ok this is really strange. Why have I not heard about you before?
- \nu_e
: This is a bit shameful. You see, we don't like to interact with anybody very much. We just pass through everything and we very, very, very rarely stop to enjoy the sights.
- S: So what's the point of having three neutrinos?
- \nu_e
: Well. . . thanks for the confidence! We are very important. I am not sure what my two sisters are good for, but I—the super important electron neutrino—do tons of stuff. For one, I cool down stars (stars get rid of their energy by sending me away) and that's kind of important for life on Earth isn't it?
- S: Ok, anything else?
- \nu_e
: I participate in nuclear reactions and I am an important participant in the structure of the whole cosmos (there is power in numbers is what I say!)