Every second of every day you are bombarded by billions of trillion subatomic particles shooting down from deep within space. They are blown through you with the power of a cosmic hurricane and shot at almost the speed of light. They come from all over the world at all times of the day and night. They permeate the earth's magnetic field and our protective atmosphere like so many butter.
And yet the hair on your head is not even disheveled.
What's going on?
Little neutral one [19659005DiesewinzigenKugelnwerdenNeutrinosgenannteinBegriffder1934vombrillantenPhysikerEnricoFermigeprägtwurdeDasWortistvageitalienischfür”
;kleinesneutrales”undihreExistenzwurdevermutetumeinesehrmerkwürdigenukleareReaktionzuerklären[The Biggest Unsolved Mysteries in Physics]
Sometimes elements feel a little … unstable. And if they are left alone too long, they fall apart and turn into something else, a little easier on the periodic table. In addition, a small electron would pop out. However, in the twenties, careful and detailed observations of these distortions found tiny, fluctuating discrepancies. The total energy at the beginning of the process was a little bit bigger than the energy that came out. The math was not right. Strange.
So some physicists have brewed a whole new particle of whole matter. Something to take the missing energy. Something small, something light, something without charge. Something that could slip unnoticed through their detectors.
A small, neutral. A neutrino.
It took a few decades to confirm their existence – so slippery and devious are they. But in 1956 neutrinos joined the growing family of known, measured and confirmed particles.
And then things got weird.
With the discovery of the muon, the difficulties began to brew At the same time as the neutrino idea gained ground: the 1930s. The muon is almost exactly like an electron. Same fee. Same Spin But in one crucial sense, it's different: it's heavier, over 200 times more massive than its brother, the electron.
Muons participate in their own reactions, but they do not tend to last long. Because of their impressive volume, they are very unstable and quickly disintegrate into smaller-bit showers ("fast" means here within microseconds or two).
This is all well and good, which is why muons enter into neutrino history
Physicists found that in decay reactions that indicate the existence of the neutrino, one electron always jumped out and never a muon. In other reactions, muons would pop out and not electrons. To explain these results, they argued that neutrinos in these decay reactions (and not in any other kind of neutrino) always agree with electrons, while the muon must pair with an as yet undiscovered type of neutrino electron-friendly neutrino would be the events from the muon events can not explain. [Wacky Physics: The Coolest Little Particles in Nature]
And so the hunt went on. And further. And further. Only in 1962 did physicists finally feel the second kind of neutrino. Originally it was called "Neutretto". The scheme of calling it a muon neutrino outweighed rational heads, as it always pairs in reactions with the muon.
The Way of the Tao
Okay, so two confirmed neutrinos. Did nature have more in store for us? In 1975, researchers at the Stanford Linear Accelerator Center bravely searched the mountains of monotone data to reveal the existence of an even heavier sibling for the nimble electron and the powerful muon: the massive dew that reached a whopping 3,500 times the mass of the electron. That's a big particle!
So the question immediately came up: If there is a family of three particles, the electron, the muon and the dew … could there be a third neutrino that could mate with this newly found creature?
Maybe, maybe not. Maybe there are only the two neutrinos. Maybe there are four. Maybe 17. Nature has not met our expectations so far, so no reason to start now.
Having skipped many gruesome details, physicists over the decades persuaded themselves of various experiments and observations that needed a third neutrino. But it was only on the brink of the millennium in 2000 that a specially designed experiment on Fermilab (called the DONUT experiment humorous, for direct observation of the NU Tau and no, I do not think so) had enough assured sightings to rightly make a discovery to promote.
The Ghost Hunt
So why are neutrinos so interested in us? Why have we been hunting them for more than 70 years, from World War II to modern times? Why have generations of scientists been so fascinated by these small, neutral ones?
The reason is that neutrinos continue to live beyond our expectations. For a long time we were not even sure if they existed. For a long time we were convinced that they were completely without mass until the experiments proved annoying that they needed to have mass. Exactly how much remains a modern problem. And Neutrinos have this annoying habit of changing their character while traveling. When a neutrino travels in flight, it can switch between the three flavors.
There may even be an additional neutrino that does not participate in common interactions – something called a sterile neutrino. Physicists are hungry for it.
In other words, neutrinos constantly challenge everything we know about physics. And if there is one thing we need in the past and in the future, this is a good challenge.
Paul M. Sutter is astrophysicist at of Ohio State University host of  Ask a Spaceman and Space Radio and author of Your Place in the Universe .
Originally published on ] Live Science .