We all have a (very tiny) glow of light, no movie magic needed

Numerous sci-fi and fantasy narratives are wrapped in a nostalgic glow, but it’s not merely sentimentality at play. Several characters emit a literal glow—from the fingertip of E.T. to the demon symbols featured in this year’s blockbuster K-Pop Demon Hunters.

This dazzling effect can be easily replicated through drawing or digital enhancement, but in reality, we—and all living organisms—emit feeble traces of light. Researchers remain puzzled about whether these biophotons have a specific function or if they are just trivial by-products of cellular activity.

This phenomenon is distinct from bioluminescence, which involves well-defined chemical reactions, asserts Catalina Curceanu, a nuclear and quantum physicist at Italy’s National Institute of Nuclear Physics–National Laboratories of Frascati. It’s also separate from thermal radiation, which arises from bodily heat!

Biophotons themselves are single photons that appear to stem from standard cellular processes, even though the exact mechanism of their generation remains unclear, says Christoph Simon, a quantum physicist at the University of Calgary. For instance, cells tend to generate reactive oxygen species—tiny molecules with unstable oxygen atoms that can either signal within the cell or inflict damage on other molecules.

When these reactive entities engage with lipids, long chains of fatty acids that create structures like cell membranes, they trigger a “chain reaction,” explains Simon. “When two radicals interact and produce another radical,” he adds, energy is released. This energy may take the form of a photon with a wavelength ranging from 200 to 1,000 nanometers, encompassing ultraviolet, visible, and near-infrared light.

The majority of biophotons don’t escape the cellular environment or reach our skin. Instead, they are absorbed by the myriad of proteins, lipids, and other cellular components. Nonetheless, a few do break free, generating “around 1,000 photons per square centimeter per second” from our skin, notes Simon. This quantity is roughly a millionth of what you would see from a firefly and cannot be discerned by the naked eye, he further claims, noting that he and his colleagues have successful detected these photons from the skin of live mice.

Moreover, sprouting lentils and beans also emit biophotons, as observed by Curceanu and her team. “It displays a particular pattern, some level of complexity… implying that this signal might have a purpose,” she remarks.

However, the precise nature of this purpose remains elusive. Various organisms possess molecules known as rhodopsins that sense light. Humans have them in their eyes. Yet, the actual function of this emitted light may occur in hidden realms.

Some smaller molecules within our body can absorb and re-emit light, explains Philip Kurian, a theoretical physicist at Howard University in Washington, D.C. Tryptophan, an essential amino acid, is especially known for its fluorescent properties.

Kurian and his colleagues have demonstrated that certain cellular structures, like microtubules—which form the cellular architecture—have protein configurations that could facilitate tryptophan’s role in a quantum information network. The amino acids may share a photon, allowing it to exist in two places within the network simultaneously, demonstrating a quantum superposition.

This effect enhances the fluorescence of tryptophan, thereby enabling increased information processing capabilities, he explains. Consequently, such biophotons may facilitate more rapid information processing within cells and beyond. This could account for why our brains can execute significant processing tasks with relatively minimal energy, Kurian suggests.

The luminous quality depicted in science fiction diverges from the reality of biophotons, emphasizes Curceanu. “It’s easy to misunderstand biophotons and envision that we all glow in an unrealistic manner.” Nevertheless, life does emit a faint light, and scientists are striving to uncover the reasons behind this biological luminescence.