Your Brain Is Glowing—and Scientists Don’t Know Why

Life on Earth is drenched in light. The sun floods the planet with energy, fueling the growth of plants and sustaining nearly all ecosystems. But light doesn’t only come from the sky. In a remarkable discovery, scientists are realizing that life itself creates light—not just in glowing jellyfish or fireflies, but deep within our own bodies.

This hidden glow is known as ultraweak photon emissions (UPEs). These are tiny streams of light particles—called biophotons—emitted by living tissues, including the human brain. Scientists have long suspected their existence, but for the first time ever, researchers have successfully measured biophotons coming from a living human brain—without opening the skull.

Published in the journal iScience, this study opens a new frontier in neuroscience. The researchers discovered not only that the brain emits light, but also that the intensity and pattern of this glow change depending on what you're thinking or doing. This unexpected link suggests that these biophotons might be more than just metabolic by-products—they could play an active role in cognition itself.


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Why Does the Brain Glow?

Everything that exists above absolute zero emits radiation. But the UPEs coming from living organisms are far more intense than normal heat radiation. They occur in the visible or near-visible light spectrum, meaning they’re technically visible—but far too faint for the human eye to detect without special equipment.

These photons are produced when excited oxygen molecules, created during cellular energy production, return to a stable state and release energy in the form of light. This process, called radiative decay, occurs constantly in the body.

The brain, being one of the most energy-hungry organs in the human body, is theoretically a major source of biophotons. Until now, this light had only been observed in neuron cultures—nerve cells in petri dishes—where scientists recorded small but measurable amounts of photon activity.

The new study scales this up to living humans. Using extremely sensitive photon detectors and EEG caps to measure brain activity, the researchers placed participants in a completely darkened room. Detectors were focused on two specific brain regions: the occipital lobes (which process vision) and the temporal lobes (which process sound).


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The Stunning Results

The first major finding was simple—but groundbreaking: photons are consistently coming out of the human head. It wasn’t random noise, interference, or background radiation. The light is real, and it's coming from the brain.

The second discovery was even more puzzling. When participants switched between different cognitive tasks—such as opening or closing their eyes—the pattern of light changed. Yet, this change did not neatly correspond with brain activity detected via EEG. In fact, more electrical activity didn’t always mean more light.

Lead author Dr. Nirosha Murugan suggests a possible reason: “Maybe the photons aren’t being picked up by our detectors because they’re being absorbed, scattered, or even used within the brain before they escape.”


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Do These Photons Serve a Purpose?

The idea that light plays a role in biology isn't new. As early as 1923, Russian scientist Alexander Gurwitsch demonstrated that onion roots could stop growing if a light-blocking barrier was placed between them. This hinted that photons may act as messengers in cellular communication.

Recent studies have added weight to this idea, especially in plants, bacteria, and simple organisms. But applying this theory to the human brain—the most complex structure in the known universe—is a huge leap.

Still, researchers like Murugan think it’s worth exploring. Could these photons help transmit information between neurons? Could they represent a new form of brain signaling, beyond electricity and chemistry?

Michael Gramlich, a biophysicist at Auburn University who was not involved in the study, finds the work “intriguing and potentially revolutionary,” but cautions that there’s still a long way to go. “The big question,” he says, “is whether UPEs are actually causing cognitive changes—or if they’re just a side-effect of standard brain processes.”


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Looking Ahead

Other scientists are now working on nanotechnology tools to probe deeper. At the University of Rochester, researchers are developing nanoscale fiber-optic probes to see whether nerve fibers can guide photons like tiny light cables.

Meanwhile, Murugan’s team is planning to use more advanced sensor arrays to pinpoint where in the brain these photons come from and whether they follow any known neural pathways.

Even if biophotons turn out not to play a direct role in cognition, the method used in the study—measuring light along with electrical activity—is a promising new technique. Murugan calls it photoencephalography, and it could become a non-invasive way to monitor mental states in the future.

As Gramlich concludes, “Even if the theory that biophotons are part of brain function turns out to be wrong, the tools developed here will be invaluable. This field is just beginning.