The Sun is not just a source of light but a giant laboratory where ghostly particles are born. Every second, billions of neutrinos fly through your body, barely noticing you. But inside the Sun, these particles behave differently: they change their type on the fly, like an actor playing three roles in a single play.
In a new study, scientists explored an unusual idea: gravity itself might influence this performance. In teleparallel gravity, spacetime is described not by curvature but by torsion. It's like working with a twisted spring rather than a bent rubber sheet. In such a universe, an extra field appears that senses the density of surrounding matter. Inside the Sun, where density is enormous, the field "hides"—its influence becomes as faint as a voice in a noisy crowd. But outside, in the vacuum, it regains strength.
It is this field that changes neutrino mass. The mass depends on how dense the surrounding matter is: at the Sun's core, it's one value; near the surface, another. This shift alters the point at which one neutrino flavor converts into another. The effect is like tuning a radio: usually you pick up a station at 100 MHz, but due to interference the signal shifts, and you have to nudge the dial a bit.
The authors checked what real data say. They took results from three detectors — Super-Kamiokande (a huge water tank in a Japanese mine), Borexino (a vessel of liquid scintillator at Italy's Gran Sasso laboratory), and SNO (a Canadian detector using heavy water). These instruments catch neutrinos from the Sun and count how many of each flavor arrive. By comparing theory with measurements, the researchers placed constraints on the strength of the field's interaction with torsion. It turns out the effect must be very weak, but not zero.
This approach is a rare opportunity to test a theory of gravity not through the motion of stars or galaxies but through the behavior of tiny particles. If future experiments, such as the next-generation detector JUNO, see the predicted shift, it would build a bridge between the physics of the microcosm and the structure of spacetime. For now, we gaze at solar neutrinos as into a mirror reflecting the hidden mechanisms of gravity.
The Sun produces about 10³⁸ neutrinos per second, but even at night you get your dose: they pass freely through Earth, like light through a window pane.
In Stanisław Lem's novel "Solaris," a sentient ocean manipulates gravity, and here spacetime itself changes particle properties depending on density — almost like a living medium.