The elusive neutrino – a mysterious subatomic particle that may be a key to the unexplained dark matter of the universe.
The neutrino is a subatomic particle, smaller than a proton and an electron. The neutrino was proposed by Enrico Fermi and his co-workers in 1930-1932 to explain a common nuclear reaction called beta-decay.
Not too long after, Fermi couldn’t get a paper published in Nature because the neutrino concept was too unrealistic, so he switched to experimental physics. He later worked on designing the atom bomb in Los Alamos, not far from where I live.
The neutrino is a tiny particle that should be emitted by the sun’s nuclear reactions which produce the heat that the earth needs. But they are so tiny that they are essentially weightless. The mass of a neutrino is now known to be less than a millionth of an electron.
In the late 1960’s Ray Davis, an astrophysicist, built a large detector in the Homestake gold mine in South Dakota, and identified neutrinos coming from the sun. Davis was the first to measure the flux or number of neutrinos arriving at earth from the sun.
Most neutrinos at the earth come from the sun – 400 billion of them arrive every second through every square inch of earth’s surface. But most of them pass through earth without hitting anything because they are so small and weigh virtually nothing.
Now, 50 years later, we know that a neutrino is a subatomic particle that comes in three types and several flavors, like icecream has different flavors.
An immense particle detector has been put together in the Antarctic ice sheet. The detector is a cube of the ice sheet about a kilometer (3/5 of a mile) length on each side.
A larger detector means a greater chance of seeing a collision between a neutrino and the nucleus of an ice molecule (i.e. water).
5,000 sensors have been drilled into this so-called IceCube to catch such collisions. The IceCube will record neutrinos from billions of light-years away in the universe.
The neutrinos are a part of the Standard Model of nuclear physics, which was developed to explain the interactions between all known nuclear particles. If a neutron is fired at a uranium nucleus, for example, it may enter the nucleus and cause it to split into two smaller nuclei. This is called nuclear fission and is how the atom bomb works.
After many years of research, the Standard Model is the best model to include all types of subatomic particles, like protons, neutrons, quarks, muons, leptons, and neutrinos – and their interactions with other particles or nuclei.
But the Standard Model has a problem – it can only explain 5% of the Universe. The other 95% is called dark matter and dark energy because it can’t be explained by even the best minds in astrophysics.
How do we know dark matter is there? because it has gravity and affects the rotation of galaxies. If you add up all the matter we can see and measure in a galaxy, its gravity pull is not enough.
But the “dark” stuff, whatever it is, is not measurable by any of our scientific instruments. We have to seek some other way to find and measure the missing particles that make up dark matter, according to Kirsten Perez.
The discovery of different types of neutrinos may hold the key. Or the key may lie in some other undiscovered nuclear particle.
So if people tell you that scientists know everything – this shows they don’t. After 100 years of creative research in astrophysics and cosmology, they can’t explain the missing dark matter and dark energy.
But don’t be fooled, scientists can explain a plethora of related information including neutron stars, black holes, gravity waves, and the Higgs boson, which I have written about in past blogs.
And when you next get a CTScan, or a PET scan, know that these medical instruments work on principles derived from research on nuclear particles and their interaction with your body.
Post-script: The above was adapted from Nova, the PBS video Published on October 13, 2021 and available on YouTube: “This detector can catch cosmic neutrinos.”
BLOG TOPICS: I write in-depth blogs about a mix of topics: Health and Hiking, and Science and Energy, and Inspiration and Hope.
The Gray Nomad ….. It’s fun to contemplate mind-boggling things about the universe.
Religion that God our Father accepts as pure and faultless is this: to look after orphans and widows in their distress and to keep oneself from being polluted by the world. [Book of James, chapter 1.]
I loved this – absolutely fascinating! Thank you for your contributions to our scientific awareness!
Hello Ian,sounds very deep from a photographers limited understanding,but well explained.Interestingly,Sarena has just finished a session of radioactive Iodine, to eliminate any cancer cells from her faulty thyroid, removed a month ago.So she was in isolation until the radioactive readings were low enough….sounds scary,but they have been practising nuclear medicine for 50 years!