How can a photo in Explore go from #1 to dropping completely off the list?
It seems counter intuitive but it makes sense. Interestingness is not calculated in real-time, microsecond to microsecond. It is calculated en masse at intervals, perhaps once per hour. Imagine all of the activity that occurs in an hour—not just on your photo but all of the other photos in Explore and on the rest of Flickr. All of that activity goes into the Interestingness algorithm and every photo is re-ranked. The result of that activity is that many photos’ Interestingness rankings may have changed drastically.
