Rome's Prime Meridian

Trip Start May 22, 2007
Trip End Jun 04, 2007

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Thursday, May 24, 2007

Thursday 24May07 - Rome's Prime Meridian
In Allan Weisbecker writes in his book "In Search of Captain Zero" that there are theories about the center of the universe and curved space - that the fabric of space is thought to be curved, not straight as logic would seem to dictate.  This suggests that the universe is finite yet unbounded, of definable size yet with no edges or borders, no beginning, no end, a perfectly enclosed system.  And if there is a center to it all, that center is simply wherever you are at the moment.  The subtextual point, one is never truly lost unless and until that condition is admitted to and therefore, the center of the universe is wherever one happens to be.  I've certainly applied this reasoning in my defense when accused of being lost.  I was reminded of this point as I stood under the stained glass dome depicting the universe in the Basilica Santa Maria.  There was another surprise in store.
"Not all those who wander are lost."
I spent the first day in Rome without a map.  For a geographer, traveling without benefit of map is torment and while I didn't know exactly where I was, I certainly wouldn't admit to being lost.  Rob and I visited several churches and I was thoroughly turned around until Basilica Santa Maria.  Where once I was lost, I was found again.  There, on the floor of the huge vaulted basilica, inlaid in Marble and bronze, the blessed demarcation for lost geographers - the Prime Meridian. This best describes my accidental discovery of Rome's eighteenth century Prime Meridian in the Basilica Santa Maria degli Angeli e del Martini.
Here in the basilica, I came across what I hadn't expected to find; earth sciences depicted in the floor, ceiling and walls.  The following is a description of the meridian line.
"This meridian was until 1846 the regulator of time for the Romans. Now, time is known through a cannon shot fired daily at noon from the Janiculum Hill. Whereas the line in St Sulpice is very "Spartan", that of Santa Maria degli Angeli is very "illuminated". Around 1700, Pope Clement XI commissioned Francesco Bianchini to build this meridian line, within the basilica. The object was threefold: the pope wanted to check the accuracy of the Gregorian reformation of the calendar; he wanted to produce a tool to exactly predict Easter; finally, he wanted to give Rome a meridian line as important as the one Bianchini had recently built in Bologna's cathedral, San Petronio.
The church was chosen for several reasons:
1) Like other baths in Rome, the building was already naturally southerly oriented, so as to receive unobstructed exposure to the sun.
2) The height of the walls allowed for a long line to more precisely measure the sun's progress through the year.
3) The ancient walls had long since stopped settling into the ground, ensuring that carefully calibrated observational instruments set in them would not move out of place.
4) Because it was set in the former baths of Diocletian, it would symbolically represent a victory of the Christian calendar over the earlier pagan calendar. But perhaps there is even a fifth point, which is that this is indeed a church "of angels".
Furthermore Bianchini's sundial was built along the meridian that crosses Rome, at longitude 12 50'. At solar noon, around 12.15 p.m. (1.15 p.m. in summer time), the sun shines through a small hole in the wall to cast its light on this line each day. At the summer solstice, the sun appears highest, and its ray hits the meridian line at the point closest to the wall. At the winter solstice, the ray crosses the line at the point furthest from the wall. At either equinox, the sun touches the line exactly halfway between these two extremes. The longer the meridian line, the more accurately can the observer calculate the length of the year. The meridian line built here is 45 m long, and is composed of bronze, enclosed in yellow-white marble.
But that is not all: Bianchini also added holes in the ceiling to mark the passage of stars. Inside the dark interior, Polaris, Arcturus and Sirius are visible through these holes, even in bright midday and their names are recorded on the floor." (ref:
I ended the afternoon floating east to west across the meridian around this amazing space of biblical science.
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