Rainbows
My shared office has large west-facing windows that on sunny days see direct sunlight for a few hours every day before the sun sinks behind an adjacent building. A couple of suncatchers hanging over the windowsill split this sunlight into little round rainbows sprinked all over the office.
Bochum can feel quite grey, but to quantify just how grey, I've been logging the days that see the appearance of these rainbows since March 2025. Below you can see the data collected since then.
This is obviously not a perfect method—you would be better off looking at weather data on a meteorological website—but it is fun. Here are some Caveats:
- Rainbows are logged when they are observed; if no rainbows are logged, it is assumed there was no rainbow that day. Rainbows can only be logged when I observe them while in the office or when someone else who is in the office observes them and reports a sighting to me. There may therefore be a small number of falsely labelled no-rainbow days from when, say, it was very sunny only while everyone was off for a seminar.
- The above also means there is no data for weekends, public holidays, and other days when the university is closed; these are excluded from the dataset.
- The rainbows may appear when the sun manages to peek through for just a few seconds on an otherwise cloudy day; if these rainbows are observed, they are logged. On some days, they might be missed.
- It may happen that it is sunny in the morning but cloudy in the afternoon or vice versa. The sun's light can only hit the suncatchers when the sun is within a very specific region of the sky, and it is in this region for a couple of hours starting as early as 12:30pm in the winters and as late as 5:00pm in the summers. So we are only logging sunniness at a specific period during the day, and this period itself oscillates with the seasons.