On the purported oscillation of human capacities, measured in days since birth.
BiOS plots the three biorhythm cycles — physical, emotional, intellectual — for you, your friends, and whatever Thursday you’re worried about.
Free · iPhone · No account, just a birthday
Background
Invented in the 1890s. Huge in the 1970s. Unproven ever since.
The theory begins, as many strange things do, in 1890s Berlin: Wilhelm Fliess — ear-nose-throat man and close friend of Freud — became convinced that human life runs on fixed cycles of 23 and 28 days, counted from birth.¹ A 33-day intellectual cycle was appended later by people who felt thinking deserved its own wave.
By the 1970s the theory was popular. Airlines and Japanese transport companies charted their drivers’ “critical days.”² Pocket biorhythm calculators sold in the millions. Controlled studies then found the predictions performed precisely as well as chance, and everyone quietly moved on to star signs.
We are not everyone.
The cycles
Three waves. Three alleged jurisdictions.
Physical · 23 days
Governs (allegedly): strength, stamina, opening jars. BiOS opens on your own curves, today’s numbers, and your running count of days on Earth.
Emotional · 28 days
Governs (allegedly): mood, patience with group chats. Add friends by birthday — when Ol’ Mate’s wave is in the trench, maybe ring him Wednesday.
Intellectual · 33 days
Governs (allegedly): judgement, wit, crossword speed. Point the chart at any date — the exam, the speech, the grand final — and see what the theory reckons.
Method
We’re checking whether any of this is real. With you.
Once a day, BiOS asks a single question: how do today’s numbers feel? Responses are pooled anonymously — no names, no accounts — into a running tally of theory versus actual Tuesdays.
If the waves mean anything, the tally will show it. If they don’t, the tally will show that instead, and we’ll frame it.
Enrolment
Participation is free and takes one birthday. n = you, plus whoever you rope in.
1. Fliess also believed the nose was the seat of most human ailments. We mention this so you can calibrate your trust appropriately.
2. The Ohmi Railway Co. reported fewer accidents after issuing drivers biorhythm warnings — an effect researchers attribute to people simply being told to drive carefully. Placebo, but make it sinusoidal.
3. The three waves realign only once every 23 × 28 × 33 = 21,252 days — a little over 58 years. The pattern drifting behind this page hasn’t repeated since the day you were born, and won’t for decades yet.