Eli5: what is a neutrino and what does is do?


Electrons, protons and neutrons are easy to follow. But every time I try to look up neutrinos I get videos that are hard to follow and an unhelpful wiki page.

In: Physics

They’re particles similar to electrons, except they have no charge. They also don’t interact through the strong force.

They interact solely through the weak force (and presumably through gravity, since they have mass, but we’ve never managed to measure their effect since they’re so light). This means that they hardly interact with other particles at all. Hundreds of trillions pass through you every second, coming from the sun, and they don’t do anything. On average, for any individual neutrino to “bump into” a matter particle, it would take light-years of lead.

To detect neutrinos, we have GIANT observatories. The most famous observatory is essentially just the ice in the South Pole. The new P-One observatory off the coast of Canada uses a good chunk of the Pacific Ocean as the observatory. Even these giant neutrino detectors are lucky to detect one or two neutrinos every once in a while. Neutrinos are just that hard to measure.

As for what they “do”, nothing really. They just sort of exist. They don’t make up any matter we interact with, and they hardly interact with us at all. **Edit:** *u/funhousefrankenstein mentioned that fusion (and other particle interactions) can emit neutrinos in order to obey the universe’s conservation laws. The neutrinos are sort of the waste products of the processes. They still don’t “do” anything, but it’s impossible to do the reaction without producing the waste as well.*