Astronomers propose building a neutrino detector out of the Pacific Ocean

Neutrinos are the second most elusive particle in the universe. They are made in large quantities and are responsible for nuclear fusion and decay. When a nuclear event is happening, the neutrinos are involved.

The sun's core is a giant nuclear fusion reaction, so naturally it's producing a lot of neutrinos. If you hold your thumb up to the sun, 60 billion neutrinos will pass through your thumbnail every second.

Where did all the baryons go?

The total number of neutrinos that will hit your body is about one, despite the trillions of them passing through your body every second.

Physicists for decades assumed that Neutrinos were completely massless and traveled through the universe at the speed of light. Scientists discovered that neutrinos have a tiny amount of mass.

How much mass is a matter of scientific research. There are three types of neutrinos. Each of these "flavors" participates in different kinds of nuclear reactions, and frustratingly, all three of them have the ability to change identities as they travel. You only know a fraction of what you wish you knew, even if you can see a neutrino and determine its type.

There are whispers in the water.

The Standard Model of particle physics has no explanation for the mass of neutrinos. Physicists would love to measure the mass of the threeflavors and understand where they come from. They have to do a lot of experiments.
You can either set up a device to generate a bunch of buggers in a laboratory or build a huge array to capture some that originate off Earth.

The experiments have made a lot of progress. The Kamiokande experiment in Japan detected the neutrinos from the supernova 1987A. They needed a vat of water to do it.

The IceCube Neutrino Observatory has increased the ante in recent years. The observatory consists of a solid kilometer of ice at the South Pole, with dozens of strands of receivers sunk a kilometer into the surface. After a decade of work, IceCube has discovered some of the most energetic neutrinos ever. It involves high-energy processes in the universe.

Kamiokande and IceCube use a lot of water. Pure water is the best choice for a large chunk of anything that can serve as a neutrino detector. When one of the trillions of passing neutrinos strikes a random water molecule, it gives off a brief flash of light. The purity of the water allows the detectors to see the direction, angle and intensity of the flash very accurately. It would be difficult to reconstruct where the flash came from if the water had impurities.

They can get a handle on the incoming neutrino's energy from there.

Massive simulation of the universe probes mystery of ghostly neutrinos.

The patch of the Pacific.

This is good for normal, everyday neutrinos. The most energetic neutrinos are very rare. Only the most powerful events in the universe can cause the extremely rare neutrinos.

After a decade of observation, IceCube has only been able to capture a few ultra-powerful neutrinos.

We're going to need a bigger boat.

A paper published to the preprint server arXiv in November proposes to turn a large swath of the Pacific Ocean into a nature's own neutrino detector.

The idea of finding a suitable, lonely part of the Pacific is surprisingly simple. It's pretty easy. I mean strands of photodetectors that are at least a kilometer long. The strands should be sunk to the bottom of the ocean. Attach floats to them so they are upright in the water.

The P-one design has seven 10- string clusters with each string holding 20 optical elements. More coverage is provided by the 1,400 photodetectors floating around an area of the Pacific several miles across.

You just need to wait once it's up and running. The detectors will trace the ocean water after the neutrinos strike it.

It is harder than it sounds. The strands will move with the ocean. The Pacific Ocean is not as pure as it could be. It will be difficult to measure the light between the strands.

The experiment will need constant calibration to adjust for all these variables. The team behind P-one is working on a small, two-strand demo as a proof of concept.

We can go hunting for neutrinos.

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"Ask a Spaceman" and "Space Radio" are hosted by Paul M. Sutter, who is also the author of "How to Die in Space."'s expert voices: op-ed and insights was written by Sutter.