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Sparavigna, A. (2016). Augusta Emerita and the Major Lunar Standstill of 24 BC. PHILICA.COM Article number 635.

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Augusta Emerita and the Major Lunar Standstill of 24 BC

Amelia Carolina Sparavignaunconfirmed user (Department of Applied Science and Technology, Politecnico di Torino)

Published in astro.philica.com

Abstract
Augusta Emerita, today Merida, in Spain, was a Roman town founded in 25 BC by Titus Publius Carisius, legate of Augustus, for the veterans discharged after Cantabrian wars. Here we are considering a possible astronomical orientation of this Roman town. Its decumanus has an alignment almost coincident to the moonrise azimuth on a major lunar standstill. In fact, 24 BC was a year of major lunar standstill. From 24 BC to 25 BC the maximum declination of the moon changed from 28.55 degrees to 28.32 degrees, and then, as we can see by simulations, the northern and southern moonrise azimuths are varying of a very small quantity. The coincidence of the date of foundation to a year close to a major lunar standstill reinforces the possibility that the decumanus of this town was deliberately designed with this specific astronomical orientation.

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Augusta Emerita and the Major Lunar Standstill of 24 BC

 

Amelia Carolina Sparavigna

Politecnico di Torino

 

Augusta Emerita, today Mérida, in Spain, was a Roman town founded in 25 BC by Titus Publius Carisius, legate of Augustus, for the veterans discharged after Cantabrian wars. Here we are considering a possible astronomical orientation of this Roman town. Its decumanus has an alignment almost coincident to the moonrise azimuth on a major lunar standstill. In fact, 24 BC was a year of major lunar standstill. From 24 BC to 25 BC the maximum declination of the moon changed from 28.55 degrees to 28.32 degrees, and then, as we can see by simulations, the northern and southern moonrise azimuths are varying of a very small quantity. The coincidence of the date of foundation to a year close to a major lunar standstill reinforces the possibility that the decumanus of this town was deliberately designed with this specific astronomical orientation.  

 

Augusta Emerita, today Mérida, in Spain, was a Roman town founded in 25 BC by Titus Publius Carisius, legate of Augustus, for the veterans discharged after Cantabrian wars. Of this Roman town, we find a detailed discussion in [1]. First of all, the reference is remarking that the rectangular plan, which is typical of the Roman military camps, is still visible in the modern town. “The decumanus maximus survives almost unchanged from the head of the Roman bridge over the Guadiana to the site of the so-called town gate; the cardo maximus ran from Trajan's arch to the problematic Arch of Cimbron (no longer extant). Probably there was originally a walled enclosure framing this central quadrilateral" [1]. However, no visible remains of this enclosure are still existing. There are only references to the sites of the gates, such as the Trajan's arch. "Nothing is known of the forum, which must have been near the modern Plaza Mayor, at the intersection of the cardo and decumanus, but extensive remains of two of its temples survive” [1].

As discussed by F. Haverfield in his book on the ancient town-planning [2,3], during the later Republic and the earlier Empire, a reason for the foundation of new towns was in the necessity of discharge the large masses of soldiery used in the armies of Rome. Like in the case of the army used for the Cantabrian wars, a quick solution was that these men were settled in the civil life by creating a new colonia. It is not surprising then that many Roman towns, such as Augusta Emerita, have a definite type of town planning, which was the same of Roman camps, the “castra”. In this case then, the “town areas … are small squares or oblongs; they are divided by two main streets into four parts and by other and parallel streets into square or oblong house-blocks ('insulae'), and the rectangular scheme is carried through with some geometrical precision. … The two main streets [Decumanus and Kardo] appear to follow some method of orientation connected with augural science. As a rule, one of them [Kardo] runs north and south, the other east and west, and now and again the latter street [the Decumanus] seems to point to the spot where the sun rises above the horizon on the dawn of some day important in the history of the town" [2]. For instance, the town of Timgad in Africa was oriented to the sunrise on September 18, the birthday of Trajan. On Timgad, Haverfield is referring to a discussion he found in the works of Walter Barthel (1880-1915), a German archaeologist, who studied towns and land limitation (subdivision) of Roman Africa [4].

Then, according to Haverfield, that followed Barthel and some Latin authors who discussed of the augural science about the foundation of a town, the Decumanus could had been determined to have its direction aligned along the azimuth of the rising sun. Using satellite maps and sunrise azimuths, it is possible to check easily if a Roman town or castrum had a possible solar orientation [5-7]. Sometimes, we find alignment along sunrise on solstices, in an evident symbolical link between towns and Heavens.

However, some Roman town exist having the decumanus which cannot be oriented to sunrise. Analyses made by means of a modern ephemeris, which is giving the sunrise/sunset and moonrise/moonset azimuths on satellite maps (Photographer’s Ephemeris), are showing that they could have been oriented to moonrise on a major lunar standstill [8-12]. Augusta Emerita is one of this cases: it can be a remarkable example of this astronomical orientation, remarkable because we have a specific date for its foundation, the year 25 BC.

 

As previously told, the decumanus maximus is running from the head of the Roman bridge over the Guadiana to the site of the so-called town gate. So let us investigate using the Photographer’s Ephemeris, the bridge and decumani on a major lunar standstill (April 2025). The results are given in the Figure 1. The bridge and the decumani have an alignment almost coincident to the northern possible moonrise azimuth. In the following Figure 2, we apply the software to a Roman temple, that we can find in the town. “Near the decumanus [there exist] some parts of a temple, for no good reason usually called the temple of Diana” [1].

As we can see from the Figure 2, the moonrise azimuth seems a little bit different from the direction of the temple basement. For this reason we have investigated whether 25 BC was a year of major lunar standstill. Using CalSky (http://www.calsky.com/cs.cgi), a web based astronomical calculator used by astronomers, we have that for 24 BC the maximum declination of the moon was 28.55 degrees and then it was a year of major lunar standstill. The year 25 BC had a maximum declination which was of 28.30 degrees. So, as we can see by simulation (in the Figure 3, we simulated for 2025 and 2026), the northern moonrise azimuths are varying of a very small quantity. The coincidence of the date of foundation (25 BC) to a year close to a major lunar standstill (24 BC) reinforces the possibility that the decumanus of Augusta Emerita was deliberately planned with this specific astronomical orientation. 

 

 

 

References

[1] Iglesias, L. G. (1976). Augusta Emerita. In the Princeton encyclopedia of classical sites. Stillwell, Richard. MacDonald, William L. McAlister, Marian Holland. Princeton, N.J. Princeton University Press.

[2] Haverfield, F. (1913). Ancient Town-Planning, Oxford, Clarendon.

[3] Francis John Haverfield (1860–1919) was a British historian and archaeologist, who was the first to undertake a scientific study of Roman Britain. He is considered by some scholars to be the first theorist to tackle the issue of the Romanization of the Roman Empire.

[4]  Barthel, W. (1911). Römische Limitation in der Provinz Africa, Bonn, Carl Georgi Verlag.

[5] Sparavigna, A. C. (2016). The Town Planning of Pompeii and Herculaneum Having Streets Aligned Along Sunrise on Summer Solstice. SSRN Electronic Journal June 30, 2016). DOI: 10.2139/ssrn.2802439

[6] Sparavigna, A. C. (2016). Roman Towns Oriented to Sunrise and Sunset on Solstices. SSRN Journal May 8, 2016. DOI: 10.2139/ssrn.2777118

[7] Sparavigna, A. C. (2014). Solstices at the Hardknott Roman Fort. PHILICA Article number 549. Available at SSRN: http://ssrn.com/abstract=2745184

[8] Sparavigna, A. C. (2016). Torino e i Lunistizi. PHILICA Article number 603.

[9] Sparavigna, A. C. (2016). Alcuni siti romani in Piemonte orientati coi lunistizi. PHILICA.COM Article number 604.

[10] Sparavigna, A. C. (2016). On the Orientation of the Roman Grumentum. SSRN Journal. DOI: 10.2139/ssen.2796722 

[11]  Vv. Aa. (2016). Wikipedia, https://en.wikipedia.org/wiki/Lunar_standstill

[12] The moon has an apparent behavior, which is more complex than that of the sun. We have that the sunrise direction oscillates between the two solstitial positions during a year, whereas the moon does the same during a nodal period (about 27 days). Moreover, the moon has a period – the lunar standstill period (18.613 years) – on which the values of the extremal directions (standstills) are changing. In this manner there are major and minor standstills, of which we can calculate the directions that are depending on latitude. For a latitude of about 45°, like that of Torino for instance, we have that the minor and major northern moonrise azimuths (directions) are 47.40° and 65.65° (angles are given from true north). The minor and major southern moonrise azimuths are 116.35° and 132.58°. The azimuths of sunrise on summer and winter solstices are between these lunar azimuths. For the calculation of moonrise azimuths, we can sue the formula given by Jürgen Giesen at his web site http://www.geoastro.de/sunmoonpolar/index.html#Mondwenden. The reader can find detailed discussion and apps for simulate the moon apparent motion there.

 

 

 

Figure 1:  In these images, the blue lines represent the northern moonrise and moonset azimuths on a major lunar standstill (April 2025). It seems that the roman bridge and the decumani are along the northern possible moonrise azimuth. The yellow and orange lines are the sunrise and sunset azimuths. The images had been obtained from snapshots of the Photographer’s Ephemeris results.

 

Figure 2:  The same of the Figure 1, with snapshots of the Photographer’s Ephemeris results (simulation on April 4, 2025). The software has been applied to the temple of Diana.  Note that the moonrise azimuth seems a little different from the direction of the temple basement.

 

 

 Figure 3:  The two images are giving snapshots of the Photographer’s Ephemeris results, for the software applied to a decumanus of Augusta Emerita. In the upper panel we see the northern moonrise azimuth for a year of major lunar standstill (April 2025). In the lower panel, we see the northern moonrise azimuth for the next year (April 2016). There is a small difference, as we had for years 24 BC and 25 BC.

 

 


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Sparavigna, A. (2016). Augusta Emerita and the Major Lunar Standstill of 24 BC. PHILICA.COM Article number 635.


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1 Author comment added 10th July, 2016 at 11:55:39

In the caption of Figure 3 there is a misprint. Please read this: “In the lower panel, we see the northern moonrise azimuth for the next year (April 2026)”. As you can see, the date of the panel is April 21, 2026.




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