Comment by gholap

This article was quite hard to understand, and the author called it "Lunar Terminator Paradox", which does not give too many Google hits.

"Lunar Terminator Illusion" is the thing to search for. This 11-year old Vsauce video did the trick for me: https://www.youtube.com/watch?v=Y2gTSjoEExc

Check around the 5m3s timestamp if in hurry, and not interested in other stuff he discusses.