Full moon and human activity

Folklore says the full moon makes people restless and apt to go out. We test it against Tokyo's mobility data: Google's COVID-19 Community Mobility Reports, as a percent change from a normal baseline. We look at transit stations (the closest proxy for how crowded the trains are), retail and recreation (people out and about), and — as a reverse control — time spent at home, which should fall if people really do go out more. The values cross zero, so we compare the deviation (in points) from a local same-weekday average.

Transit stations (a proxy for train crowding)

Retail & recreation (people out and about)

Time at home (reverse control — should fall if people go out)

Data: February 15, 2020–October 15, 2022, Google mobility reports (Tokyo), 974 days

"People act up on a full moon"

On a full-moon night people grow restless and want to go out — a belief you'll hear in emergency rooms, on police shifts, and behind every service counter. The moon's pull, the story goes, stirs the body and the mood and drives people into the streets. If that were true, full-moon nights should show more people on the move — busier stations and busier streets.

We test it against Tokyo's mobility data. No public dataset records train crowding over the long run, but the closest proxy is the volume at "transit stations" in Google's published mobility reports.

How this verdict is computed

The data is Google's COVID-19 Community Mobility Reports for Tokyo (Feb 2020 – Oct 2022, a frozen, discontinued dataset). Each day's value is a percent change from a baseline — the day-of-week median in early 2020. We use transit stations (a proxy for trains), retail and recreation (people out and about), and, as a reverse control, time at home — which should fall if people really do go out more.
Mobility swings hard with the weekday/weekend rhythm and with the upheavals of the pandemic. So we take the average of the same weekday within ±3 weeks as the expected value, and measure the deviation (in points) for full- and new-moon days. That removes the weekly rhythm and the slow social trend at once.
Full- and new-moon days (the instant ±24h) are marked using the moon's age at noon Japan time.

See the methodology for the full criteria.

A caveat on the data

This dataset covers only about two and a half years, all within the pandemic, with roughly 33 full moons — a far smaller sample than the 22-year topics, so the confidence intervals are wider, and it was an unusual time when mobility lurched with social events. And yet — perhaps because of that — one thing stands out: even as a state of emergency cut movement in half, the full-moon nights remained indistinguishable from any other.

The real culprit: the schedule of daily life

What moves people is not the moon. It's the weekday/weekend rhythm and the events of society. Transit drops sharply on weekends and sank deeper still under the state of emergency — a swing far larger than anything the full moon could produce. What the moon genuinely moves is not people's feet but the tide (→ tides).

Data sources

Google COVID-19 Community Mobility Reports (Tokyo, daily percent change from baseline; source: Google LLC)
Lunar age and the instants of the phases are computed in-house from the algorithms in Jean Meeus, "Astronomical Algorithms" (UTC basis)

No difference