Sunday, April 9, 2017

Marking Time Until Easter

Finding a painting that captures the resurrection of Jesus in a convincing way is a daunting task. Jesus climbing out of a tomb or standing before a weeping Mary abound. But while they may accurately describe a scene, they don't (for me) capture the momentousness of the event. So for this week, we will consider art and faith beyond an illustrative image. See the Art&Faith Matters Facebook this week for some narrative images covering the events of Holy Week.

Diagonally across the floor of the nave of S. Maria degli Angeli in Rome is a brass line. The metal is inlaid and marked at intervals by words and images. Similar lines are found in the Basilica of San Petronio in Bologna, St. Sulpice in Paris and Santa Maria del Fiore in Florence. The reason they are there has to do with Easter. Specifically, calculating when Easter would be.

Unlike Christmas, Easter is not on a fixed day. Instead it is celebrated on the first Sunday after the first full moon after the Spring equinox. The equinox is the day when the hours of the day are divided equally: 12 hours of daylight and 12 hours of night. We consider March 21 as the equinox, but the true equinox is not always on March 21. Figuring exactly when the equinox would occur required a meridian line. Such lines were installed in many cathedrals, turning them into solar observatories.

The meridian line is half of the apparatus required to track the path of the sun (and the dependent celebration of Easter). The other required element is an oculus - a hole in the ceiling that serves as an aperture. The sun's rays shone through the oculus onto the meridian line, crossing the line at solar noon and over the course of the year, indicating both winter and summer solstices (the extreme ends of the sun's journey at the extreme ends of the meridian line) as well as the equinox at the midpoint of the meridian line.

The meridian lines really served more to confirm the accuracy of Gregorian calendar reform than to predict an unknown Easter date. Pope Gregory XIII instituted calendar reform in 1582 in an effort to stop the drift of events like the solstices and equinoxes. In that year, ten days were removed from the calendar so that Eastern and Western Christians would celebrate Easter on the same day. This intersection of sun and Easter was also an intersection of science and faith. The meridian lines were supported by the church authorities who were happy to be able to tell at a glance when Easter would be.

The meridian lines have not remained completely accurate. This is due not to any astronomical discrepancies but rather to the fact that some of these cathedrals are sinking. The measurements are no longer as accurate, meaning the sun shining through the oculus illuminates the floor near but perhaps not on the line. In some cases, the lines are now used as instruments to measure how the structure of the cathedral has shifted. The lines are still there, though, visible reminders of the movement of the universe that God created and then redeemed through the life, death and resurrection of Jesus Christ.

All images are of S. Maria degli Angeli e dei Martiri in Rome, Italy. (Top) The meridian line crossing the nave of the church. (Middle) Close-up of the meridian line with Easter - Paschae - identified. (Bottom) Exterior of S. Maria degli Angeli e dei Martiri.

For thoughts on the followers who came to the tomb, click here.
For thoughts on Jesus' words to Mary, click here.
For thoughts on how we picture what Jesus did in his life, death and resurrection, click here.

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