1600s / 17th century history on the 15th of May
1618 : Johannes Kepler confirmed his discovery of the third law of planetary motion, which he first discovered 2 months earlier on the 8th of March but originally rejected the idea.
1800s / 19th century history on the 15th of May
1817 : The 1st private mental health hospital was opened in the United States, in Philadelphia, Pennsylvania. The Asylum for the Relief of Persons Deprived of the Use of Their Reason is now known as the Friends Hospital.Continue reading 15th MAY ~ HiSTORY ON THiS DAY