Mostly from the sun. About 100 trillion a second. Maybe one of them hits you in a whole life.
About 100 trillion neutrinos pass through your body every second. IceCube says so, and UNLV physicist Michael Pravica gave Live Science the same number. Nearly all come from the sun, says UW-Madison’s Lu Lu.162
You will not feel them. Lu’s line on the hits, not the traffic, is the spooky one: over a whole lifetime you should expect no more than roughly one interaction in your body, perhaps a few.2 IceCube puts the same idea on a detector the size of a person: about 100 years for one interaction, and about 100,000 years in the high-energy range IceCube was built for.1 Those are not the same clock. They are the same joke. The flood is real. The collision is almost not.
Same rabbit hole, told by TP, in your pocket.
A neutrino is a speck with no electric charge and a mass so small that for years the catalogs set it to zero. Light bounces off you because electric charges shove. A neutrino does not shove. It can fly through the Earth and keep going. People call it a ghost particle for that reason, not because anyone thinks it is a soul.2
The sun makes them in its core, where hydrogen fuses into helium. They leave at almost the speed of light. About eight minutes later they are here, including the ones coming up through the floor at night. You are not a wall to them. You are a rumor.
The reason anyone invented them is a bookkeeping error that would not go away. In a kind of radioactivity called beta decay, a nucleus spits out an electron. If that were the whole story, every electron from the same kind of nucleus would leave with the same energy, the way a ball dropped from one shelf hits the floor at one speed. The electrons came out with a smear of energies. Either energy was not conserved, which would crack physics, or something invisible was carrying the rest.
In December 1930 Wolfgang Pauli wrote to a meeting in Tübingen, to the “radioactive ladies and gentlemen,” and offered what he called a desperate remedy: a light, neutral particle that took the missing energy.3 He was embarrassed. He was not sure anyone could catch it. He also was not claiming it was magic. Fermi and Edoardo Amaldi later named it the neutrino, a little neutron. Pauli had been using the word neutron, and then James Chadwick found the actual neutron, so the little one needed its own name.3
Catching one took until 1956. Clyde Cowan and Frederick Reines parked a detector next to a nuclear reactor in South Carolina, a firehose of antineutrinos, the antimatter twin. An antineutrino hits a proton. A positron and a neutron come out. They saw that. Reines got the Nobel Prize in 1995. Cowan had died, and the prize is not given after death.34
The 100 trillion is not a headcount of your torso this second. Detectors record the tiny fraction that hit, then work backward. Lu’s picture is a coarse net in a river. If you know the net, how long it was in the water, and how easily the fish slip through, you can estimate the river.2 IceCube’s net is a cubic kilometer of Antarctic ice. A human body is a terrible net. That is why the traffic and the “maybe one hit in a life” can both be true.
There are three flavors: electron, muon, and tau. A muon is a heavier cousin of the electron. A neutrino is born as one flavor and can arrive as another. That swap is called oscillation, and it only happens if the neutrinos have mass. The Standard Model had required them to be massless. Oscillation says the model is not the whole story. It still does not weigh the three masses in grams. Which one is heaviest got a first hint in 2026, and it is a lean, not a call.511
The 1998 result from Super-Kamiokande, a water tank deep in a mine at Kamioka in Japan, was about atmospheric neutrinos, the ones cosmic rays make in the air. They changed flavor on long paths through the Earth. The solar puzzle, decades of experiments undercounting electron neutrinos from the sun, was closed by the Sudbury Neutrino Observatory. The sun was making the right number. A share of them had changed clothes on the way. Takaaki Kajita and Arthur McDonald shared the 2015 Nobel Prize for those two proofs of oscillation.5
How much lead stops one? CERN says a typical neutrino could cross a light-year of solid lead before it interacts. The Nobel Foundation’s theme article says solar neutrinos can pass through several light-years of lead before they are absorbed.34 Higher energy, shorter trip. IceCube has watched the Earth stop neutrinos more than a million times more energetic than the sun’s. The solar flood still goes through the planet. You do not.6
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and counting
This is not a sensor. It is the published average, about 100 trillion neutrinos a second through a person, times how long this page has been open. Nothing is measured, stored, or sent.
Nothing you type is stored or sent anywhere. The age stays in this page, in your browser, and the math runs here.
Type an age. This is the published average times the seconds in that many years, not a count of you.
1.0
Lu told Live Science that nearly all of the neutrinos going through you come from fusion in the sun. A few come from farther away, including other galaxies. The counter on this page does not sort them. It uses the round total.2
Lu: no more than roughly one interaction in your body in a lifetime, perhaps a few, and no health risk worth mentioning.2 IceCube: about 100 years for a person-sized detector, and 100,000 years at IceCube’s energies.1 A lifetime and a century are the same neighborhood. A hundred thousand years is a different faucet.
About 100,000 atmospheric neutrinos a year in a cubic kilometer of ice. That’s about 275 a day. The ice is buried from 1,450 to 2,450 meters so cosmic-ray junk does not drown the sensors. The size and the depth are different reasons.1
Supernova 1987A. Underground detectors recorded neutrinos hours before the light. Kamiokande II saw 11, a detector in Ohio saw 8, one in Russia saw 5. About two dozen, total, from a star in a neighbor galaxy. Fermilab and the Sanford lab both tell that story.78
Oscillation proves the masses are not zero. It does not weigh them. KATRIN did put a ceiling on it: under 0.45 eV, less than a millionth of an electron’s mass.12 In September 2026 JUNO posted its first hint: the third mass is probably the heaviest. That’s at about 2 sigma; physicists want 5 before calling it. Leaning, not settled.11
A sterile neutrino would be a flavor that does not even feel the weak force, only gravity. JUNO lists a search for them as a window, not a result. Nobody has a confirmed one to put on this page.9
Super-Kamiokande sits in the Kamioka mine and watches for a flash of light when a neutrino finally hits. That 1998 atmospheric result is half of the 2015 Nobel. SNO, in a Canadian mine, is the other half: the sun was fine, the neutrinos had changed flavor.5
IceCube is the brute-force version. One cubic kilometer. 86 cables, 5,160 light sensors in the ice, frozen in from 2004 to 2010. When a neutrino hits a nucleus, the debris moves faster than light can move in ice, which is allowed, and that makes a faint blue glow the sensors can see. From the glow they get an energy and a direction.12
The 1987 supernova is the proof that this is not a parlor trick. The neutrinos left the collapsing core and got out. The light had to ride the shock. So the ghosts arrived hours earlier, and the people running the detectors only noticed after astronomers saw the star.7 If a star in our own galaxy dies while a big detector is on, the warning comes first, and the telescopes get a head start.
“A hundred trillion” is an estimate with a friendly face. It comes from the few that hit a detector, scaled up by the size of the net.2 If someone tells you it is an exact census of your ribs this second, they are selling the rounding. “Maybe one hit in a life” is Lu’s ceiling, with room for a few. IceCube’s 100 years is the cousin of that sentence. Neither is a promise that your particular body gets exactly one.
The masses are still unknown as numbers. In September 2026 JUNO posted its first hint: the third mass is probably the heaviest. That’s at about 2 sigma; physicists want 5 before calling it. Leaning, not settled.11 A sterile neutrino is a maybe. And the highest-energy ones IceCube catches, from places like the neighborhoods of giant black holes, are rare enough that each one is a press release. The solar flood is the ordinary one. The weird ones are not.19
Where this page lands. The flood is real. About 100 trillion a second, mostly from the sun, and your body almost never notices. The hundred trillion is a round estimate scaled up from the few that hit a detector. It is the right picture. The exact masses are still unweighed, and the September hint on which one is heaviest is a lean.
JUNO, the Jiangmen Underground Neutrino Observatory in China, finished filling a 20,000-ton liquid-scintillator detector and started physics data on August 26, 2025. The Chinese Academy of Sciences said so. Nature published the first oscillation measurement on June 10, 2026, from 59 days of data.913 It watches antineutrinos from reactors about 53 kilometers away. The question it is built to answer is the mass ordering: is the third neutrino heavier than the second. In September 2026 the collaboration posted a longer analysis, 207 days, that leans that way at about 2 sigma once other experiments’ mass-splitting measurements are folded in. Physicists want 5 before calling it.11 It also lists sterile neutrinos as something to look for, which is not the same as having found one.
DUNE, the Deep Underground Neutrino Experiment, is not taking that data yet. First data from the South Dakota detector around early 2030, Fermilab’s beam in 2031. A June 2026 collaboration talk is where that schedule is written down.10 The point of the machine, when it is on, is the same list: ordering, the three-flavor picture, and a supernova in our galaxy, which would light the detector up with thousands of events instead of 1987’s two dozen.8
That is the stake in 2026. The particle Pauli apologized for is now a tool. It told us the sun was fine. It arrived before the light of a dying star. The next detectors are there to weigh the thing, or at least to say which way the weights run. Until they do, the honest sentence is the short one. They are going through you. Almost none of them notice.
The 100 trillion, the 100 years, and the 100,000-year caveat, on one page.
Lu Lu on the sun, the lifetime hit, and why the count is a net in a river.
Kajita and McDonald. Oscillation, and why mass broke the massless rule.
The neutrinos got here hours before the light. The event counts are in the piece.
August 26, 2025. The mass-ordering experiment that is actually on.
Pauli’s letter, 1956, and a light-year of lead.
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