14-05-2025
Living Creatures Cast a Faint Aura That Stops at Death, Study Suggests
We often say that the light leaves a person's eyes when they die. But it turns out all living organisms, including humans, emit a literal glow that extinguishes after death, according to a new study.
The study, published in The Journal of Physical Chemistry Letters, found that living things glow faintly throughout their lives due to the energy released by metabolic and cellular processes. Monitoring this weak signal could one day help scientists track injury and disease.
As cells consume energy, mitochondria release tiny amounts of reactive oxygen species (ROS) as a byproduct. These ROS react with molecules including proteins, lipids, and fluorophores, giving off a few sparse photons. But this light, a phenomenon called ultraweak photon emission (UPE), is—like its name suggests—extremely weak compared to ambient light sources—and is really hard to image. It's been observed in cells belonging to plants, animals, and humans, but never in entire living—or dead—animals.
To capture this ghostly glow, lead author Daniel Oblak, an associate professor at the University of Calgary, and his team used an ultra-sensitive digital imaging system. They placed mice in dark, temperature-controlled boxes and imaged them with a two-hour-long exposure. When they imaged a living mouse, they saw photons rising all over the mouse's body, and with hotspots over its organs, head, and paws. However, dead mice exhibited a widespread drop-off in UPE, indicating that their light had been snuffed out, literally.
'While the live mice emit robust UPE, likely indicative of ongoing biological processes and cellular activity, the dead mice's UPE emission is nearly extinguished,' the authors wrote in the paper, which was supported by the Quantum Sensors Challenge program of Canada's National Research Council (NRC).
And it's not just animals—living plants also give off an otherworldly glow. The researchers analyzed UPEs in an umbrella tree, finding that the strength of the glow increased when plants were injured or exposed to high temperatures. Chemical modifications, in particular the application of the anesthetic benzocaine, also increased the intensity of this light.
Since the light is correlated with metabolic activity, the amount of light emitted by tissues can increase when they're damaged. By looking at tissues producing too much or too little light, doctors could noninvasively monitor the health of tissues. Researchers might also be able to monitor health and plant growth under different environmental conditions, the authors say.
UPE might be 'a promising tool for advancing our understanding of both plant biology and biomedical research at the fundamental level,' the authors wrote.
