Neutrino from the Cradle: The Secret of the Early Universe ⚡ экспресс
We explore whether the recently recorded KM3NeT ultra-high-energy neutrino has an early-universe origin—from the decay or annihilation of long-lived primordial relics. This scenario produces a sharp spectral peak, where the neutrino flux is tiny everywhere except at the event's energy, easing the discrepancy with IceCube's nondetection versus a simple power law. For emission close to the recombination epoch, we included interactions with the cosmic neutrino background and radiation from decay products, which alter the spectrum; computations used a custom code. We find that this scenario could leave an observable mark on the cosmic microwave background soon, without predicting an excess of gamma rays. The upshot: the KM3NeT event could be a primordial neutrino, if it came from the recombination era or later.
Neutrinos are almost elusive particles: they zip through planets without noticing atoms. So every catch is a stroke of luck. Recently, the underwater detector KM3NeT snagged a neutrino with energy millions of times greater than Earth's most powerful accelerators can produce. A new study suggests: it's not a visitor from a distant galaxy, but a message from the early Universe. The particle was born when the world was only 380,000 years old, right after it became transparent.
This explains the silence of other observatories: the message is heard only at one energy. On its way to us, the neutrino collided with other neutrinos, and its energy changed. Such encounters could have left an imprint on the cosmic microwave background — the afterglow of the Big Bang, stretched by the Universe's expansion.
If the theory is correct, this lonely message will allow us to peer into the era of the first atoms and even deeper.
🎯 Every second, trillions of solar neutrinos pass through your body without causing the slightest harm.
🎬 Like in Arthur C. Clarke's 'Space Odyssey', where a mysterious signal comes from an unimaginable past.