My friend Augustine pointed me to this interesting graph showing the time of sunset over the course of a year. (The original author's write-up is here.)
Of course, one can produce a perfect chart by looking up meterological records. The main interest in this graph is how it was constructed. Each cell in the graph represents an hour of a day, with days running across and time running down. The cells that are not dark each contain a photograph of the sunset contributed to Flickr, the photo-sharing site. So this is in effect a graph created through mass collaboration (about 35,000 photos).
The "white" band roughly indicates the sunset. What intrigues me is the variability... what are the reasons for lighted cells appearing all over the graph?
Some ideas include:
- Different time zones
- Incorrect time setting by some photographers
- Erroneous tagging of photos as "sunset"