Sunday Science: The Neutrino

Super-Kamiokande: a huge detector looking out for tiny particles Kamioka Observatory/ICRR(Institute for Cosmic Ray Research)/The University of Tokyo

A neutrino is a tiny subatomic particle.

It's also one of the most abundant particles in the universe.

In fact, there are roughly 65 billion neutrinos passing through your body right now.

Did you notice them? 

No?

That's because neutrinos barely interact with matter, which makes them really difficult to detect.

To detect anything you can't "see" like a neutrino, scientists usually use one of the four fundamental forces to "see" how a particle interacts with matter. 

These four fundamental forces are: the electromagnetic force, gravity, the weak force and the strong force.

Neutrinos have a neutral charge and a very small mass. So, you can't detect them with the electromagnetic force (because they have no charge) or easily detect them with gravity (because they are so light and tiny).

And neutrinos do not interact with the strong force (which bonds protons and neutrons together in an atom's nucleus) because they simply do not feel it.

Neutrinos are only affected by the weak force, which has a tiny range and is involved in the decay of nuclear particles. The problem is, the chances of a neutrino interacting with the weak force are incredibly small.

This post explains the (quite frankly, bonkers) process of detecting neutrinos rather well.

If neutrinos didn't have mass, it would save a lot of physicists a lot of work.

The weird world of weighing neutrinos

For decades, scientists thought neutrinos had no mass. Then, in 1998, they discovered neutrinos do have a very small mass. We still don't know how much mass they have.

The more interesting question is why neutrinos have mass. According to one of the longstanding models of physics, called the Standard Model of Particle Physics, neutrinos should not have mass. 

So, the fact that they do have mass has really baffled the scientific community. But there are a couple of other problems with the Standard Model.

Also, if we could explain why neutrinos have mass - we could also explain why we live in a universe made of matter, and not antimatter. 

Extra reading

This year, we could see some exciting neutrino news as a huge, extraordinary machine called KATRIN (KArlsruhe TRItium Neutrino) will try to determine the mass of the neutrino once and for all. This is a lovely article all about the experiment.

In fact, there are quite a few neutrino-based experiments going on around the world: here's a list of the lot.

This is an excellent series of in-depth articles from Berkeley that give more details about neutrinos and the implications of neutrino mass.

And if you want to find out more about the experiments that hinted neutrino mass could explain why we live in a matter universe, check out this article from New Scientist.

What is Sunday Science?

Hello. I’m the freelance writer who gets tech. I have two degrees in Physics and, during my studies, I became increasingly frustrated with the complicated language used to describe some outstanding scientific principles. Language should aid our understanding — in science, it often feels like a barrier.
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So, I want to simplify these science sayings and this blog series “Sunday Science” gives a quick, no-nonsense definition of the complex-sounding scientific terms you often hear, but may not completely understand. 

If there’s a scientific term or topic you’d like me to tackle in my next post, fire an email to [email protected] or leave a comment below. If you want to sign up for our weekly newsletter, click here.