Researchers record how life’s glow fades after death

Images captured by V. Salari, V. Seshan, L. Frankle, D. England, C. Simon and D. Oblak and published in the The Journal of Physical Chemistry Letters are shown.

A new study by Canadian scientists captured something interesting: a faint glow emitted by living organisms that faded as the species died.

The research may sound supernatural, but before you imagine glowing bodies or human auras, researchers want to be clear – this isn’t mysticism, it’s biology in action.

“We metabolize; we give off light,” study co-author and University of Calgary associate professor Daniel Oblak told CTVNews.ca in a Zoom interview Wednesday. “That does not imply anything else than we’re producing energy.”

This subtle glow is called ultraweak photon emission (UPE), and while it’s invisible to the naked eye, it may hold powerful clues about health, stress and the very definition of life in the long run, researchers say.

Scientists already knew UPE existed in living things including humans, animals and plants, but this study is the first to capture detailed images showing how quickly the glow fades after death.

Researchers said previous studies were involved living mice. This study is the first to compare the UPE of living and dead mice.

The research was published in the Journal of Physical Chemistry Letters and was supported by the National Research Council Quantum Sensors Challenge program.

What is UPE?

Living things naturally give off tiny amounts of light, researchers say.

The glow is a result of chemical reactions in cells involving oxidative stress and metabolism, researchers say. It’s similar to the way a glow stick works, Oblak explained. Two chemicals mix, energy is released, and some of the energy escapes as light.

Vahid Salari, one of the study’s authors, said an interview with CTVNews.ca, “This kind of light can be seen from all living systems – from humans to plants to cell cultures.

“It’s extremely weak,” he said, estimating just 10 to 1,000 photons are emitted from each square centimetre per second. Photons are the smallest units of light.

To help put that in perspective, Oblak said, “A light bulb emits something like a billion billion photons per second. So, what we’re seeing here is so much less (than) anything that you could normally look at a light source. You would need extreme darkness.”

To study this light, researchers used ultra-sensitive cameras capable of capturing single photons. The cameras operate in total darkness to avoid interference and can detect light in the ultraviolet-visible-near-infrared spectrum – the range photons fall in.

This incredibly faint glow is a natural side effect of how our cells work, the study said. When our bodies process oxygen, they create reactive molecules that sometimes give off photons. It’s a chemical byproduct of metabolism and cellular activity – a flicker of life captured on camera.

Fading light different than body heat

Using these cameras, the researchers set out to capture the faint glow from living and recently deceased mice, as well as from injured plant leaves.

In living mice, they observed light primarily coming from the skin, where the majority of UPE occurs. After death, Salari said, “some organs still emit light, most likely from the liver.”

While some photons travel from internal organs through tissue, this contribution is small. Salari said the photons from the internal organs accounted for less than 10 per cent of the total detected signal in the images of living mice.

The team captured images 30 minutes after euthanasia and noticed the overall glow had faded significantly. Some bright spots still remained for a time, emissions they said they knew weren’t due to body heat.

“That’s the first question people ask: ‘Isn’t that just body heat?’” Oblak said. The answer is no, according to researchers, who say the mice were kept in a temperature-controlled box and every specimen was at the same temperature during imaging.

Additionally, what warm objects emit is called blackbody radiation and it shows up on the infrared spectrum, Oblak said. But what was captured for this study was something else.

Dan Riskin, CTV News Channel’s resident science expert, said the emissions these researchers were looking at are much more subtle than those from body heat.

“When you’re talking about sensitivity at this scale, the heat that we give off in the light that comes as a result of that infrared signal, it’s like a speaker playing a full blast, and they’re listening for a whisper,” he said.

Areas for future study

Noting the limitations based on the species studied, Riskin said a worthwhile direction for future studies would be to explore whether other species, such as cold-blooded animals like snakes, lizards or fish, also emit UPE. It would also be interesting to know whether the pattern of light emission differs in these species as they approach or undergo death, he said.

“Mice are warm blooded. This isn’t just the heat energy given off an infrared, it’s a different wavelength, and intensity. But is it true for fish? Is it true for humans?”

Researchers say there have been a few previous studies confirming UPE in living humans, typically seen near the hand, forehand or chest. As for deceased humans, no research exists yet, Salari said.

“Our study focused on animal models to capture high resolution, time-resolved data, but the underlying biochemical mechanisms are shared across mammals, including humans,” he added.

Plants glow too – especially under stress

The team also examined plants under stress, including injury from cutting or exposure to chemicals. A surprise came when they applied the common pain reliever benzocaine to injured leaves.

Salari said the application of benzocaine to the damaged parts of the leaf led to the light getting significantly brighter. He said it caused a stronger reaction than hydrogen peroxide, which is already known to increase light signals.

As for why this happened, it’s unclear at this point.

“We still don’t know the main source. We have some speculation, like a (sodium) channel or the release of more reactive oxygen species,” Salari said.

Researchers originally began exploring UPE reaction to anesthesia out of a broader curiosity about consciousness and reactivity in biology.

“We started doing some experiments, first with the leaf. Because some plants, like the fly trap, respond to touch,” Salari said.

Researchers wrote when anesthesia was applied, the plant stopped reacting to touch, promoting them to question whether the application of certain medications might impact the UPE.

Oblak added that while these early findings are still observational, what follows will be more detailed investigations into how chemicals affect living systems and how those effects might be seen through changes in UPE.

Possible applications and ‘metaphysical connotations’

The researchers who spoke to CTV News say they’re aware that faint glowing light in living systems might sound supernatural, but that it’s important to understand what causes it, and the implications.

“There’s a lot of metaphysical connotations to the glow,” Oblak said, but “it’s not an energy field that surrounds us. It’s biochemistry.”

And while it’s invisible to the naked eye, its invisibility doesn’t mean it’s not useful. UPE may become a valuable tool in medicine and science, researchers hope.

Riskin said with a lot of scientific discoveries, it’s unclear how useful they are until much later.

“I think it has the potential to be something that we’re going to look back on,” he said.

Salari said that because this light is tied to metabolic activity and oxidative stress, it could be used as a non-invasive way to assess health, especially in cases where early detection is difficult, like skin cancer.

Researchers said they also see the potential for monitoring organs during transplants, including using UPE to evaluate organ vitality before transplantation.

But Salari said the research has not advanced to that point yet.

Beyond medicine, UPE might also help in agriculture to detect plant stress before it becomes visible, or to monitor the health of forests or crops.

Riskin said this may give us a way to tell if a plant is alive or dead, describing a UPE reaction as “an unambiguous signal.”

“Having a new way to investigate the process of death itself is interesting,” Riskin said. “Technologies keep evolving. Now that we know there’s a signal, we can create things to listen for that signal.”

He said one way to use this research might be drone flyovers.

“It’s completely plausible that you’re going to have a drone flying over a farmer’s field that uses those wavelengths as a way of measuring the health of the plants or in a laboratory or experimental setting, where you’re looking at what happens to plants that are different treatments,” Riskin said.

Researchers stress that these applications are early-stage and will require further study.