Friday, February 26, 2010

JJNN: Neutrino

There are a lot of things out there that we can't see with our naked eyes. There are also a lot of things out there that are extremely hard (or maybe impossible) to detect with even our most sensitive detectors. One example of this was my last post about dark matter. Another example is what I want to talk about today: neutrinos.

Neutrinos are much like the WIMPs that I talked about last time. Neutrinos do not carry a charge so they tend not to interact with matter in the same way that particles that carry a charge interact with matter. That is a little hard to think about so I want to give a concrete example. Imagine a sheet of atoms. This sheet can represent anything, but we shall say that it is the surface of a desk. If you take a close look at all of the atoms they are surrounded by electrons. They electrons are negatively charged and surround the positively charged core of the atom like a cloud. Now, think of another atom falling toward the surface of the desk. This atom also has an electron cloud. From basic physics we know that like charges repel and that is just what happens. Basically one electron cloud hits the other electron cloud and they atoms repel from each other. That is how it it is with a normal atom.

In the case of the neutrino it is different. The neutrino has no electric charge. This means that it is not repelled by the electric charge of the electron cloud. The neutrino can basically slid effortlessly though the electric cloud. In other words the neutrino will not bounce off from the surface and will go though. There is a case where the neutrino will not go though the surface. That is when the neutrino interacts with the atom by smashing into the atoms nucleus. You would think that that would happen a lot, but the fact is that the diameter of a normal atom is about 10^5 times that of its nucleus. This means that a atom is mostly made up of "empty space," and the chances of actually hitting the nucleus are very small indeed. Even though the chances are small that is the only time we actually detect a neutrino. The fact is that 50 million neutrinos that are produced in the sun pass though our bodies every second and hardly any of them actually interact with us. That is how hard it is to detect these things.

Now that the basics of the neutrino are covered, I want to get into this news story. It seems that the High Energy Accelerator Research Organization (Know as KEK for it's Japanese name) located in Ibaragi prefecture produced a neutrino that was detected 295 kilometers (183 miles) away by the Super Kamiokande detector in Gifu prefecture on the 24th of this month.

This is actually amazing because there are a lot of countries that are in the race at the moment to produce and detect neutrinos and this was the first time it has ever happened. The article does not really got into that many details so I wonder how they know this was the neutrino that was produced by the KEK. It could have just been a coincidence that they detector detected a neutrino from the sun at the same time as the neutrino was produced by the group at KEK. I would really like to hear more about this story and see how they set up their experiment. For now all I can say is that it looks like something amazing happened, but I am not so sure yet.

Any way, it is now time for the word of the day. Today's word is ニュートリノ(にゅうとりの). It is pronounced nyuutorino and it means neutrino. It is just another big piece in the puzzle of science.

See you next time at JJNN

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