One of the minor puzzles of the Bible's New Testament is the date of Jesus' crucifixion. Two British scientists report they have found an astronomical clue that enables them to pin down the correct month, day, and year.
It is an eclipse of the moon, which they believe the Apostle Peter linked to that event.
Thanks to modern techniques that allow for such factors as the gradual slowdown in Earth's rate of rotation, they are able to back-calculate the moon's motions as seen from Jerusalem with a high degree of precision. This allows them both to pick out the significant eclipse and to refine the correlation between the first century Jewish and Roman (Julian) calendars.
The scientists are Colin J. Humphreys and W. G. Waddington of Oxford University. They take as their basis the statement of the Gospels and weight of scholarly opinion. Those place Jesus' trial and crucifixion on the eve of the Jewish sabbath (that is, on a Friday) and the eve of the Passover, a feast held coincident with a full moon. As they explain in reviewing their work in Nature, they used these indications to narrow down the dating.
The Jewish day ran from evening to evening. Lambs for the Passover feast were slaughtered between 3 p.m. and 5 p.m. on the 14th day of the Jewish month Nisan. The meal itself began with moonrise that evening, which was the beginning of 15 Nisan. Thus, the scientists reckon, the date sought must be a Friday coincident with a full moon. And it must fall between 26 and 36 AD on the Julian calendar because that was the duration of Pontius Pilate's procuratorship of Judea.
First, the researchers recalculated the old Jewish calendar using what they consider an improved astronomical basis. Jewish months began with the observation, at Jerusalem, of the first sliver of a new moon. Humphreys and Waddington have refined the estimates of when this should have been visible to the temple priests.
From this calendar, they draw a list of possible Friday full-moon dates between AD 26 and 36. They discard dates earlier than AD 28 - the earliest possible date for the start of Jesus' ministry. Dates beyond 33 AD are considered too late. This leaves April 7, 30, and April 3, 33. The researchers settle on the latter date as most likely. But they acknowledge that scholars are divided on this question.
This is where the lunar eclipse supplies an independent indication.
Gospel accounts note that the sun was darkened (possibly by a dust storm) on the day of crucifixion. Seven days later, in addressing a crowd on the day of Pentecost, Peter recalls a prophesy of Joel, saying (Acts 2:20, 21), ''The Sun will be turned to darkness and the Moon to blood before that great and glorious day of the Lord shall come'' (New English Bible).
Humphreys and Waddington take the ''great and glorious day'' as referring to Jesus' resurrection. They then conclude that Peter was referring to extraordinary astronomical events which the people would have witnessed on the day of crucifixion - a darkened sun (clearly mentioned in the Gospel accounts) and a blood-red moon. This is the way the moon appears during an eclipse due to light refracted into Earth's shadow by the atmosphere. The effect isespecially striking when the moon is near the horizon.
There was such an eclipse on April 3, 33. This had been discounted because it was thought the eclipse would have been finished by moonrise at Jerusalem. However, the high-precision calculations of Humphreys and Wad-dington show that the rising moon would still have been partly within Earth's shadow. Moreover, the eclipsed part would have been the edge of the moon that first appeared. It would have loomed on the horizon with a deep reddish cast. ''The effect,'' say the scientists, ''would have been dramatic. . . . The crowd on the day of Pentecost would undoubtedly have understood Peter's words as referring to an eclipse which they had recently seen.''
Thus the puzzle of the crucifixion date may well have been solved. As Humphreys and Waddington note, the date of the eclipse coincides exactly with a date which, for other reasons, is a plausible candidate. If this assessment holds up under further study, we can assign the crucifixion the Julian calendar date of April 3, 33.