DAO / Science & Research

The science of light, timing, and human rhythms.

The human circadian system responds to light — its intensity, spectrum, timing, and duration. DAO is exploring how these signals can be understood and translated into more intentional daily routines.

Scientific foundations

Published research by independent scientists.

The studies DAO’s approach is built on. Each was conducted by external researchers; none of them tested DAO or any DAO hardware.

Expert consensus · Light-exposure guidance

Recommendations for daytime, evening, and nighttime indoor light exposure to best support physiology, sleep, and wakefulness in healthy adults

Brown TM, Brainard GC, Cajochen C, et al. (2022). PLOS Biology 20(3): e3001571. doi:10.1371/journal.pbio.3001571

An international group of sleep and circadian researchers agreed recommended indoor light levels for healthy adults, expressed in melanopic equivalent daylight illuminance (melanopic EDI) — a measure weighted for the retinal cells that drive circadian responses. During the day, at least 250 lux melanopic EDI at the eye; in the three hours before bed, no more than 10; in the sleep environment, no more than 1.

What it establishesA consensus recommendation drawn from laboratory dose–response evidence, giving one measurable target for light at the eye. It is guidance, not a trial of any product.

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Laboratory study · Individual sensitivity

High sensitivity and interindividual variability in the response of the human circadian system to evening light

Phillips AJK, Vidafar P, Burns AC, et al. (2019). PNAS 116(24): 12019–12024. doi:10.1073/pnas.1901824116

Fifty-five adults aged 18 to 30 were exposed to evening light from 10 to 2,000 lux while melatonin suppression was measured person by person. Half-maximal suppression came at about 25 lux for the group — an ordinary indoor level — but individual thresholds ranged from 6 lux to 350 lux.

What it establishesThe same evening-light environment registers very differently between individuals. One fixed light threshold does not describe everyone.

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Field study · Natural light–dark cycle

Entrainment of the human circadian clock to the natural light-dark cycle

Wright KP Jr, McHill AW, Birks BR, et al. (2013). Current Biology 23(16): 1554–1558. doi:10.1016/j.cub.2013.06.039

Circadian timing was measured under participants’ usual modern routine and again after a week of summer camping with only natural light. Under natural light the internal clock synchronised to solar time, with biological night beginning around sunset, and later chronotypes shifted earliest.

What it establishesElectric lighting and the built environment are associated with less daytime sunlight, more light after sunset and later circadian timing. The light–dark cycle itself is a strong timing signal.

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International standard · Measurement

CIE S 026/E:2018 — CIE System for Metrology of Optical Radiation for ipRGC-Influenced Responses to Light

International Commission on Illumination (CIE), 2018. doi:10.25039/S026.2018

The standard defines how to weight a light spectrum for each of the eye’s five photoreceptor types — including the melanopsin-containing ipRGCs most associated with circadian effects — and how to report the result, for example as melanopic EDI.

What it establishesCircadian-relevant light is a spectral quantity. Ordinary photopic lux describes brightness for vision; it cannot be converted to melanopic EDI without knowing the spectrum.

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From science to product design

From light exposure to informed action.

  1. 01 /

    Observe exposure context

    Record when, where and how much light a day actually contains.

  2. 02 /

    Understand timing

    Place each exposure on the person’s circadian day, not only on the clock.

  3. 03 /

    Interpret relevant evidence

    Relate exposure to the published research, with its limits stated.

  4. 04 /

    Suggest actionable routines

    Turn that into a specific, timed suggestion — when to seek light, when to dim it.

  5. 05 /

    Learn from measurable outcomes

    Check each suggestion against something a person can observe, and adjust.

These are DAO’s design objectives — the principles that decide what gets built. They are not a claim that each step is already operational or validated.

Validation status

What is published, what is built, what is still to prove.

Foundational research

Peer-reviewed studies and an international standard by external researchers, listed above.

DAO engineering

  • Solar geometry for any place and date — sunrise, sunset, solar noon, day length — checked against known astronomical invariants.
  • The interactive web Instrument and the 24-term Almanac.
  • Signup, a ten-question self-assessment, and Founding Access requests.

DAO-specific validation

DAO’s hardware and product-specific performance validation are in development. There are no DAO device measurements, accuracy figures or study results to report yet.

  • Ambient light is not light at the eye.A sensor measures its own surroundings, which can differ from what actually reaches the retina.
  • Lux is not melanopic EDI.A light reading worn at the ear or wrist does not, by itself, measure retinal exposure or melanopic EDI.
  • UV is a different pathway.UVA and UVB exposure concerns the skin. It is not the retinal signal that sets circadian timing.

How the pieces fit together.

Explore the DAO FrameworkFounding Access