The Return of Light: Imbolc and the Metabolic Awakening of Spring

In the Northern latitudes, early February marks a turning point most people today aren't aware of, but ancient civilizations took very seriously.

Feb 17, 2026

Note: I'd planned to publish this essay during Imbolc, but the 49ers story had other ideas. I never intended Living Energy to be only about electromagnetic radiation and health—the deeper thread is how modern life has disconnected us from the signals our biology evolved to receive. Light. Seasons. The rhythms encoded by the ancients in fire festivals and architectural monuments. This piece is a return to that thread.

From February 1st to the spring equinox, those of us at northern latitudes gain over two hours of daylight. The rate of change accelerates—what felt like an endless plateau of darkness through December and January now tilts decisively toward light. At 45°N, we’ve already climbed from 8.5 hours at the solstice to nearly 10 hours today. By the equinox in roughly 7 weeks, we’ll cross 12 hours.

The ancient Celts marked this moment as Imbolc—from the Old Irish i mbolc, meaning “in the belly.” The name refers to pregnant ewes, who begin lactating around this time as their bodies prepare for birth. Astronomically, Imbolc falls at the midpoint between the winter solstice and spring equinox—typically between February 3rd and 6th, though it’s often celebrated on February 1st, which later became St. Brigid’s Day.

The Neolithic peoples of Ireland took this cross-quarter day seriously enough to build for it. At the Mound of the Hostages on the Hill of Tara—a 5,000-year-old passage tomb—the chamber is aligned so that the rising sun illuminates its interior at Imbolc, and again at Samhain in autumn. These sit as architectural commitments, carved in stone, that have tracked the returning light for five millennia.

By Celtic times, Imbolc had become a fire festival—bonfires lit to honor the goddess Brigid, candles placed in windows, hearth fires ceremonially rekindled to mirror the strengthening sun.

What ancient peoples marked with fire festivals and rituals—practices we often associate with mysticism—they arrived at through careful observation of the world around them, and intuition from living in connection with nature and the elements. Modern photobiology is only now catching up, giving us the scientific vocabulary for what the ancients intuitively understood: that light is the primary signal life evolved to follow.

Our bodies don’t wait for warmth to respond to light.

Melatonin secretion shifts. The hypothalamic-pituitary axis begins recalibrating hormone output. Mitochondria in tissues throughout the body sense the lengthening photoperiod through pathways only recently uncovered, including melanopsin receptors—non-visual light-sensing proteins that are triggered by blue wavelengths of light—that exist not just in the eyes, but in the skin, adipose tissue, and blood vessels.

Animals know this instinctively. Ewes lactate. Birds begin courtship behavior. Bears stir in their dens. Cats go into heat. The light reaching their cells has crossed a threshold that tells their system: prepare. Humans, insulated by artificial light and indoor climate control, have largely lost this sensitivity, but it is still built into our cells.

The crocus remembers what we’ve forgotten.

When a crocus pushes through frozen ground in early February, it’s not responding to soil temperature. It’s responding to photoperiod—the cumulative signal of lengthening days that triggers molecular cascades that lead to germination. The plant has no brain, no nervous system, but it does have photoreceptors, and those photoreceptors tell it that the light is returning.

We also have photoreceptors, we’ve just built an environment that overrides natures signals.

John Ott stumbled onto this truth by accident.

In the 1950s, working as a time-lapse photographer for Walt Disney, John Ott was commissioned to film a pumpkin growing from seed to maturity—reference footage for animators drawing the transformation of Cinderella's coach, but he ran into trouble. Under pinkish fluorescent lights, the vine produced only male blossoms. When he switched to bluish tubes, it produced only female blossoms—a complete inversion of reproductive expression controlled entirely by wavelength. Only after discovering that full-spectrum light restored normal flowering was he finally able to grow a pumpkin. The problem that nearly derailed a Disney film set him on a decades-long investigation into photobiology.

Ott wasn’t a biologist, he was a banker with a passion for time-lapse photography, which he perfected by documenting flowers blooming as a hobby in his basement lab. His careful observation of plants responding to light quality—not just intensity, but the specific wavelengths present—opened a door to new discoveries he never could have imagined. He filmed chloroplasts streaming inside leaf cells, watching them fall into sluggish clumps under incandescent light and resume their orderly circulation when he added trace ultraviolet. He documented how tomato plants infected with virus recovered when moved from glass greenhouses that filtered UV to plastic greenhouses that transmitted it.

Then he tried something stranger. Many plants close their leaves at night—a behavior called nyctinasty—but the mimosa is famous for being dramatically touch-sensitive, folding inward the moment anything brushes against it. This "sleeping" behavior was the subject of one of the earliest experiments in chronobiology: in 1729, the French astronomer Jean-Jacques d'Ortous de Mairan placed a mimosa in a dark closet and discovered that it continued to open and close its leaves on a day/night cycle even without any light cues. The plant had its own internal clock. De Mairan was too occupied with his other pursuits—the aurora borealis, the rotation of the earth—to write up the finding himself; his colleague M. Marchant presented it to the Royal Academy on his behalf.

Two centuries later, another hobbyist outsider would pick up where he left off. Ott repeated the experiment—but then went further. He took a mimosa 650 feet underground, into a coal mine. There, surrounded by a massive shield of earth, the plant immediately assumed its nighttime position—regardless of the time of day above. The internal clock had stopped. Something the plant could sense in the closet, it could no longer sense underground.

Ott’s hypothesis was that some form of radiation beyond visible light—cosmic rays, perhaps, or other ionizing radiation—penetrates ordinary building materials but not hundreds of feet of rock. The plant in the closet could still sense the day/night cycle through this invisible signal, but underground, that signal was blocked.

Modern research has expanded on this idea. German researchers Rutger Wever and Jurgen Aschoff conducted experiments from 1964 to 1989, placing hundreds of human subjects in underground bunkers shielded from external electromagnetic fields. The subjects developed circadian desynchronization, depression, and hormonal dysfunction. When the researchers introduced a 10 Hz signal—mimicking the Earth’s Schumann resonance, the electromagnetic pulse generated by lightning in the cavity between the Earth’s surface and ionosphere—the subjects’ rhythms normalized. More recent work suggests that diurnal variations in the geomagnetic field, and even tidal fluctuations in background radiation from radon-222, may also serve as timing cues for biological clocks.

The question Ott raised remains open: how many signals is life listening to? Light is the brightest, but it is not the only one. The mimosa in the coal mine suggests that organisms evolved to read the electromagnetic environment in ways we’re only beginning to understand.

The flowers taught him what ancient cultures like the Celts already knew—that light is information, and living systems are listening.

Imbolc sits at a metabolic crossroads.

The period from the winter solstice to the spring equinox is when the body is primed for transition—from fat-burning dominance back toward carbohydrate utilization, from rest and deep repair cycles to renewed activity. In traditional cultures, this was a time of emerging from winter stores, of the first green shoots, of lighter eating as fresh foods became available again.

The mismatch between our modern lifestyle and this seasonal rhythm may explain why so many people feel "off" in February—tired despite adequate sleep, unmotivated despite no clear depression, filled with unspecific irritability from the winter gloom. The body is trying to shift gears, but the environmental signals are scrambled. Artificial light at night, insufficient morning light, and climate-controlled environments kept us from ever fully entering winter's slower rhythm of rest and repair. When spring's signals arrive, we're not emerging restored, we're just depleted, trying to accelerate out of a season we never properly inhabited.

The light is returning.

Get outside in the morning. Let your eyes see the sky. Feel the quality of light changing—it’s bluer now, more energizing, carrying UV wavelengths that were absent just weeks ago. Don’t think of this as a wellness hack, think of it as reconnecting with the signals in nature that your mitochondria evolved to receive.

The birds are singing again. The crocuses are pushing through the snow. Beneath the frozen surface, other life is waking up.

Sunlight is life.

References

John Ott and Time-Lapse Photography

Ott, John Nash. My Ivory Cellar: The Story of Time-Lapse Photography. Chicago: Twentieth Century Press, 1958.
Ott, John Nash. Health and Light: The Effects of Natural and Artificial Light on Man and Other Living Things. Columbus: Ariel Press, 1973.
“Dr. John Nash Ott.” Winnetka Historical Society, July 19, 2022. https://www.winnetkahistory.org/gazette/dr-john-nash-ott/
“Dr. John Ott: The Light Side of Health.” Mother Earth News, January 1, 1986. https://motherearthnews.com/nature-and-environment/john-ott-zm0z86zhun
“Exploring the Spectrum” (documentary film, 1974/2008). Full film available on YouTube:

Early Chronobiology

de Mairan, Jean-Jacques d’Ortous. “Observation Botanique.” Histoire de l’Académie Royale des Sciences, Paris (1729): 35. (Reported by M. Marchant)
“The birth of chronobiology: a botanical observation.” Society for Research on Biological Rhythms. https://srbr.org/the-birth-of-chronobiology-a-botanical-observation/
“Jean-Jacques d’Ortous de Mairan." Wikipedia. https://en.wikipedia.org/wiki/Jean-Jacques_d%27Ortous_de_Mairan

Schumann Resonance and Bunker Experiments

Wever, Rutger. The Circadian System of Man: Results of Experiments Under Temporal Isolation. New York: Springer, 1979.
Cherry, Neil. “Schumann Resonances, a plausible biophysical mechanism for the human health effects of Solar/Geomagnetic Activity.” Natural Hazards 26 (2002): 279–331. https://www.helios3.com/wp-content/uploads/2020/11/Schumann-Resonances-Dr-Neil-Cherry-2002.pdf
McCraty, Rollin, et al. “Synchronization of Human Autonomic Nervous System Rhythms with Geomagnetic Activity in Human Subjects.” International Journal of Environmental Research and Public Health 14, no. 7 (2017): 770. https://pmc.ncbi.nlm.nih.gov/articles/PMC5551208/

Background Radiation and Circadian Timing

Zakhvataev, V.E. “Tidal variations of background ionizing radiation and circadian timing of the suprachiasmatic nucleus clock.” Medical Hypotheses 139 (2020): 109642. https://www.sciencedirect.com/science/article/abs/pii/S0306987720300608

Electromagnetic Fields and Circadian Rhythms

Valic, B., et al. “Influence of electromagnetic fields on the circadian rhythm: Implications for human health and disease.” Progress in Biophysics and Molecular Biology 178 (2023): 39–51. https://pmc.ncbi.nlm.nih.gov/articles/PMC10105029/

Melanopsin in Peripheral Tissues

Sikka, Gautam, et al. “Melanopsin mediates light-dependent relaxation in blood vessels.” Proceedings of the National Academy of Sciences 111, no. 50 (2014): 17977–17982. https://www.pnas.org/doi/10.1073/pnas.1420258111
Ondrusova, Katarina, et al. “Subcutaneous white adipocytes express a light sensitive signaling pathway mediated via a melanopsin/TRPC channel axis.” Scientific Reports 7 (2017): 16332. https://www.nature.com/articles/s41598-017-16689-4
Stachurska, Aleksandra, and Tadeusz Sarna. “Regulation of Melanopsin Signaling: Key Interactions of the Nonvisual Photopigment.” Photochemistry and Photobiology 95, no. 1 (2019): 83–94. https://onlinelibrary.wiley.com/doi/full/10.1111/php.12995
Rao, Yibing, and Samer Hattar. “Circadian-independent light regulation of mammalian metabolism.” Nature Metabolism 6 (2024): 1000–1009. https://www.nature.com/articles/s42255-024-01051-6

Imbolc and Celtic Seasonal Traditions

“Imbolc.” Wikipedia. https://en.wikipedia.org/wiki/Imbolc
“Imbolc (Imbolg) Cross Quarter Day in Early February.” Newgrange.com. https://www.newgrange.com/imbolc.htm
“What is Imbolc? This Celtic festival welcomes spring—in February.” National Geographic, January 2025. https://www.nationalgeographic.com/culture/article/imbolc-celtic-celebration-brigid
Chadwick, Nora. The Celts. London: Penguin Books, 1971.

Plant Circadian Rhythms and Photoperiodism

McClung, C. Robertson. “Plant Circadian Rhythms.” The Plant Cell 18, no. 4 (2006): 792–803. https://pmc.ncbi.nlm.nih.gov/articles/PMC1425852/
Millar, Andrew J. “The Circadian Clock: A Plant’s Best Friend in a Spinning World.” The Plant Cell 16, supplement 1 (2004): S493–S496. https://pmc.ncbi.nlm.nih.gov/articles/PMC523864/