Template:Selected anniversaries/May 15
1579: Mathematician and physicist Thomas Fincke invents new type of scrying engine which pre-visualizes tangents and secants. He will use the engine to detect and expose crimes against mathematical constants.
1618: Johannes Kepler confirms his previously rejected discovery of the third law of planetary motion (he first discovered it on March 8 but soon rejected the idea after some initial calculations were made).
1801: Mathematician Joseph Ludwig Raabe born. He will discover Raabe's ratio test, which determines the convergence or divergence of an infinite series, in some cases.
1836: Astronomer Francis Baily observes "Baily's beads" during an annular eclipse.
1973: Cryptologist Laurance Safford born. Safford will establish the Naval cryptologic organization after World War I, and head the effort more or less constantly until shortly after the Japanese attack on Pearl Harbor.
2017: Three Kings voted Picture of the Day by the citizens of New Minneapolis, Canada.
2019: New study says that Greedy coloring algorithms "have been systematically corrupted by a consortium of math criminals including Anarchimedes and Forbidden Ratio." (Source: APTO crime report.)