Stirring Astronomy into Theology: Sir Isaac Newton on the Date of the Passion of Christ

It is known that Sir Isaac Newton suggested a date for the Passion of Christ in the posthumously published "Observations upon the Prophecies of Daniel and the Apocalypse of St. John" (1733). What was not known is that the first attempts to find that date were made during the early period of his life. The Jewish National and University Library in Jerusalem contains two undated drafts in Latin under the same title, "Rules for the Determination of Easter", grouped as Yahuda MS 24E. The earlier draft contains multiple references to the virtually forgotten "De Annis Christi" (1649), written by Villum Lange, the 17th century Danish astronomer and theologian, who might have been Newton's first mentor on the Jewish calendar tradition. The second draft shows not only Newton's close acquaintance with Maimonides' theory of first lunar visibility, but also his attempt to simplify the latter's criteria by introducing different, more practical parameters. These "astronomical exercises", announced in a 1673 book, were likely intended to appear as an appendix to Nicholas Mercator's 1676 book. Both of Yahuda 24E's drafts contain an astronomical table with the solar and lunar positions for years 30-37, which Newton used to decide on the year and date of the Passion. The astronomical data comes from either 1651 "Harmonicon Coeleste" or 1669 "Astronomia Britannica" by Vincent Wing, a semi-forgotten astronomer of the seventeenth century. This makes Yahuda 24E one of the earliest of Newton's drafts, likely written in 1669-73 and certainly not later than 1683/4. A comparison of the two drafts of Yahuda 24E shows that in the later one, Newton changed his allegiance from St. John's chronology of the Passion to that shown in the synoptic gospels.