🌞 When the Sun Sends Its Ghosts: How the Sun Forges Neutrinos — and How We, on Earth, Have Learned to Make Our Own
Preface
In February 2024, I had written “Neutrinos: What Are They?” — a humble attempt to introduce these ghostly travellers of the cosmos. Among the thoughtful responses was a reader’s question that deserves not merely a comment, but a continuation:
“Interesting article. Also, I would love to see more about how many neutrinos are generated by the Sun and how long does it take? Is it possible to artificially create on Earth?”
This essay is both an answer and a reflection — a journey from the Sun’s fiery womb to the laboratories of humankind, following the paths of particles so elusive that most will cross the entire Earth without leaving a trace.
I. How many neutrinos does the Sun create?
Deep in the Sun’s core — a realm of unimaginable pressure and heat — hydrogen nuclei fuse to form helium through the proton–proton chain reaction. In this furnace of fusion, neutrinos are born.
Each second, the Sun produces approximately 10³⁸ neutrinos — that is, ten thousand trillion trillion trillion. It is an absurdly vast number; yet, like most cosmic truths, it feels both remote and intimate.
To human scale:
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Roughly 60–70 billion neutrinos pass through every square centimetre of your body each second.
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Through your thumbnail alone, about 100 billion neutrinos flow per second — silent, invisible, unstoppable.
They are the shyest of nature’s children: hardly any interact with matter, and fewer still are ever caught by our detectors.
II. How long do they take to reach us?
Neutrinos are created in the solar core, nearly 150,000 km below the surface. Once formed, they flee outward at nearly the speed of light, escaping the Sun within seconds.
Then, across the 150 million km of interplanetary space, they race to Earth in about eight minutes and twenty seconds — the same time it takes sunlight to arrive.
But there is a cosmic twist:
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The light we see from the Sun today began its journey as photons trapped in the dense plasma of the solar core — a random walk that can take hundreds of thousands of years before the photon finally escapes to space.
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The neutrinos, however, leave immediately.
So, every neutrino detected on Earth is a direct messenger from the Sun’s present moment, not its ancient past. They allow us to glimpse the nuclear furnace as it burns now, eight minutes ago by the cosmic clock.
III. Can we create neutrinos on Earth?
We can — and we do. But compared to the Sun’s torrent, our human efforts are but gentle ripples.
1. Nuclear Reactors
Every operating reactor on Earth emits a steady stream of electron antineutrinos, born from the radioactive decay of fission fragments.
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These reactor neutrinos are crucial for experiments such as KamLAND (Japan) and Daya Bay (China), which study the phenomenon of neutrino oscillation — the ability of a neutrino to change its “flavour” (electron, muon, tau) as it travels.
2. Particle Accelerators
At laboratories like CERN and Fermilab, high-energy protons are slammed into metal targets, producing pions and kaons that decay into muons and neutrinos.
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These accelerator neutrinos are fired through the Earth towards distant detectors — experiments such as T2K (Japan) or MINOS (USA) — enabling physicists to measure neutrino masses and mixing angles with precision.
Thus, while we cannot rival the Sun’s cosmic abundance, we have learned to summon neutrinos deliberately, in controlled environments, for the sheer purpose of understanding them. It is one of science’s quiet triumphs — that we can recreate, in miniature, what the universe does effortlessly at stellar scales.
IV. The cosmic connection:
Every second, as you read this, billions of neutrinos are passing through you — through the walls, through the planet, unimpeded. You are, whether you realise it or not, transparent to the universe.
The Sun sends them as if in benediction: silent proof that we are continuously in communion with the stars. And on Earth, when we create our own neutrinos in reactors and accelerators, we are, in a way, replying to the cosmos in its own language — translating awe into experiment, and mystery into measurement.
Epilogue: The Dialogue Continues:
So, to the reader whose question sparked this essay — thank you.
Yes, the Sun produces an unimaginable flood of neutrinos each second, and yes, they reach us in barely eight minutes and 30 seconds. And yes again — humanity, ever curious, has found ways to create these same particles here on Earth, not to mimic the Sun, but to learn from it.
In these ghostly messengers lies something profoundly poetic: the universe speaks not in words, but in whispers of energy and time — and every neutrino is a syllable of that eternal speech.
References & Further Reading:
- Bahcall, J. N. Neutrino Astrophysics. Cambridge University Press, 1989
- Super-Kamiokande Collaboration – “Solar Neutrinos” (University of Tokyo)
- Fermilab – “Solar and Artificial Neutrinos”
- National Research Council (USA) –– Neutrinos and Beyond: New Windows on Nature. National Academies Press, 2003.
- Big Think – “Eight facts about the Sun’s most ghostly particle”
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