In 2025, a team from the University of Calgary placed four anesthetized mice inside a dark chamber and focused a hypersensitive camera on them. It captured what the eye cannot see: a very faint light coming from the animals' skin. When they died, the light disappeared.
This glow has a name: biophotons, or ultra-weak light emissions. In fact, all living cells produce them. It is a byproduct of aerobic metabolism that mainly occurs in the mitochondria. The intensity is just below the threshold of human vision, ranging from ultraviolet to near-infrared. Nothing to do with the bioluminescence of fireflies or the thermal radiation emitted by any surface.
Now, interest in biophotons is centered on their possible diagnostic applications. Since cancer, cardiovascular diseases, and neurodegenerative diseases are associated with increased oxidative stress, emission patterns differ between healthy and diseased cells. Some teams are already exploring whether photon counting can distinguish a benign mole from a melanoma without the need for a biopsy, or monitor the viability of an organ before transplanting it.
Let's be careful, however, because the field of biophotons carries a few decades of bad reputation: in the seventies, biophysicist Fritz-Albert Popp linked biophotons with homeopathy and acupuncture. There is no evidence of this supposed "quantum coherence," and some experts doubt that such a weak signal will ever reach the clinic. The most daring hypothesis, that cells communicate with each other using light, remains the most controversial and open.
This last idea is not new. In the twenties, Russian biologist Alexander Gurwitsch observed that the tip of a onion root seemed to stimulate the cell division of a neighboring root, and that the effect passed through quartz, but not ordinary glass, as if the cells were communicating with ultraviolet light. It was impossible to replicate and was filed away in the drawer of pseudoscience. Now, in experiments still unpublished, those from Calgary have seen that, when cutting a leaf, a stream of photons lights up around the wound and spreads in a ring shape. In another study, isolated mitochondria in sealed quartz containers appear to influence each other, and the effect stops with a sheet of aluminum in between.
Just as the light from Calgary mice is only observable (with instruments) in the dark of the chamber, the solar corona (the Sun's outer atmosphere, millions of times fainter than the disk) is only observable during a total eclipse.
As you know, the solar eclipse on the 12th will be visible from very few inhabited places on the planet, and Spain is the most populated stretch of the entire trajectory. We haven't seen a total eclipse here for over a century, and the 'path of totality' will cross the Peninsula from northwest to southeast and will end in the afternoon over the Balearic Islands. But it won't be the last astronomical phenomenon soon: after a partial eclipse in 2027, in January 2028 an annular eclipse will again cross the Mediterranean, drawing a ring of fire over Ibiza, Formentera, and Mallorca. Enjoy the first one.
