There is a particle moving through your body right now. Trillions of them, actually, knifing through your flesh, your bones, the chair beneath you, the ground below that, the entire bulk of the Earth, without slowing, without stopping, without leaving the faintest trace that they were ever there. They are called neutrinos, and for something so absurdly abundant, we know embarrassingly little about them.
Jeanne Wilson has spent her career trying to change that. A Professor of Particle Physics at King’s College London, she works on some of the most remote and physically demanding experiments in science, chasing particles that seem almost philosophically committed to not being found. She spoke about why that impossibility is precisely the point.
“Neutrinos are the hardest particles to measure,” she says, “which is why they’re the most exciting. They’re still the ones we probably know least about.”
Going Underground
The first thing you notice about neutrino research is where it happens. Not in gleaming university laboratories or on the clean floors of physics departments, but deep underground, buried beneath mountains and the floors of mines, hidden from the noise of the world above.
The reason is radiation. The Earth’s surface is a cacophony of particles raining down from the cosmos, a constant background roar that would drown out the whisper of a neutrino interaction entirely. To hear anything at all, you have to go somewhere quiet. Very quiet.
“All of the experiments I work on are deep underground,” Wilson explains, “because you’ve got to get away from the radiation of the Earth’s surface.”
One of her laboratories, SNOLAB, sits two kilometres beneath the surface at the bottom of a Canadian mine. Getting there is an experience unto itself: a descent down the mine shaft, then a mile-long walk through the dark to reach the lab, followed by a mandatory shower before entering the clean room. Another experiment, Super-K, is being built beneath a mountain in Japan, accessed horizontally through a tunnel. It will be the largest underground cavity ever excavated anywhere on Earth.
“It’s a huge privilege to work in these places,” she says, and there is nothing performative about it.
Why a Ghost Particle Matters
The universe, at its most fundamental level, is built from twelve particles. Just twelve. Neutrinos account for three of them, which means that understanding these near-invisible slivers of matter is not a niche pursuit but a condition of understanding reality itself.
And there is a great deal still to understand. Scientists do not yet know precisely how much a neutrino weighs. They know it is extraordinarily light, but not exactly how light. More strangely, neutrinos have the habit of shifting identity as they travel, oscillating between three distinct types, or flavours, in a quantum sleight of hand that has no tidy analogy in everyday life. Wilson’s research is focused on mapping the rules that govern these transformations.
Then there is the bigger question lurking behind all of it. The Big Bang, by every calculation we trust, should have produced equal quantities of matter and antimatter. Yet the universe we inhabit is made almost entirely of matter. The antimatter is simply gone, annihilated by some asymmetry in the early universe that physics has not yet fully explained. Wilson believes the answer may be sitting in her detectors.
“There is no antimatter flying around at the moment, but the Big Bang should have made equal amounts of matter and antimatter. Something must have happened in the past to destroy all the antimatter to leave us in this matter-dominated world. We think that the answer to this might be in our neutrino detectors.”
A New Kind of Astronomy
Beyond the fundamental questions, Wilson sees something more practical taking shape on the horizon. Because neutrinos are produced in the most violent events in the universe, supernovae, black hole mergers, the deaths of massive stars, they carry information that light cannot. They travel in straight lines, undeflected by magnetic fields, undimmed by dust. A neutrino that left a dying star ten thousand light years away arrives here carrying a faithful record of what happened.
“If we understand neutrinos,” she says, “then we can use them to understand other things, and do astronomy with them. In the same way that infrared astronomy has opened up new frontiers, we could theoretically have the same thing with neutrino astronomy.”
The field already has a name: multi-messenger astronomy. The idea is to read the universe not through a single channel but through all of them simultaneously, catching gravitational waves, light across every wavelength, and particles, neutrinos among them, from the same cataclysmic event. Each messenger tells a different part of the story.
The Long Road to a Ghost
Wilson did not set out to spend her career underground. At school she was, by her own description, a good all-rounder, the kind of student who kept options open rather than charging toward a fixed destination. She considered optics for a time, arranged work experience at an optician and an eye hospital, and quickly concluded that was not for her.
Physics won out, she says, because of logic. She found it more structured than chemistry, more grounded than pure mathematics, and she had the good fortune of enthusiastic teachers at her all-girls school who pushed her toward it rather than away. A summer internship at CERN during her undergraduate years sealed it. She was assigned to a neutrino experiment and never really left.
“Those sorts of internships are still offered,” she notes. “It’s highly competitive, but it’s a brilliant experience if you can get on it.”
Her days now bear little resemblance to the solitary genius of physics mythology. They are made of early-morning video calls with colleagues in Japan, late-afternoon calls with collaborators in North America, supervision sessions with PhD students, university administration, and, squeezed in wherever the calendar allows, the work she loves most: writing code, pulling patterns out of data, making the numbers speak.
“The great thing about being an academic is that there isn’t really a typical day,” she says.
For young people drawn toward physics, her advice cuts against the grain of how the subject is often taught. The students who go furthest, she suggests, are not necessarily the ones who score highest on exams, but the ones who cannot stop asking why.
“The kind of students who do well at physics are those who want to know why, and don’t just learn things by rote. Those who enjoy the learning, and don’t just want to know what to do to pass exams.”
Somewhere beneath a Canadian mine right now, a detector the size of a house is waiting. Neutrinos are passing through it by the trillion, nearly all of them undetected, indifferent, gone. But occasionally, just occasionally, one leaves a mark. And that is enough.