Roman dodecahedron

A Roman dodecahedron or Gallo-Roman dodecahedron[1][2] is a small hollow object made of copper alloy which has been cast into a regular dodecahedral shape: twelve flat pentagonal faces, each face having a circular hole of varying diameter in the middle, the holes connecting to the hollow center.[1] Roman dodecahedra date from the 2nd to 4th centuries AD and their purpose remains unknown.[1] They rarely show signs of wear, and do not have any inscribed numbers or letters. [3]

Roman bronze dodecahedron found in Tongeren, Gallo-Roman Museum, Tongeren

History
Two dodecahedra and an icosahedron on display in the Rheinisches Landesmuseum Bonn, Germany

The first dodecahedron was found in 1739. Since then, at least 116 similar objects have been found in Italy, Austria, Belgium, France, Germany, Hungary, Luxembourg, the Netherlands, Switzerland and the United Kingdom.[1] Instances range in size from 4 to 11 centimetres (1.6 to 4.3 in). A Roman icosahedron has also been discovered after having long been misclassified as a dodecahedron. This icosahedron was excavated near Arloff in Germany and is currently on display in the Rheinisches Landesmuseum in Bonn.[4]

Purpose

No mention of dodecahedrons has been found in contemporary accounts or pictures of the time. Speculative uses include as a survey instrument for estimating distances to (or sizes of) distant objects, though this is questioned as there are no markings to indicate that they would be a mathematical instrument;[5] as spool knitting devices for making gloves,[3] though the earliest known reference to spool knitting is from 1535;[6][7][8] as part of a child's toy,[3] or for decorative purposes.[9]

Contemporary craftspeople and YouTubers have successfully created knit gloves using 3-D printed reconstructions of the dodecohedrons, demonstrating their functionality for this purpose, and suggesting this as the historic use case.

Several dodecahedra were found in coin hoards, providing evidence that their owners either considered them valuable objects, or believed their only use was connected with coins.[10] It has been suggested that they might have been religious artifacts, or even fortune-telling devices. This latter speculation is based on the fact that most of the examples have been found in Gallo-Roman sites.[11][12] It has also been suggested that they might have been an object to test the skill of a metalsmith, perhaps as part of a portfolio to demonstrate their capabilities to customers or as a way to qualify for a certain status in a collegium (guild). This speculation is based on the historic cost of bronze and the level of skill necessary to cast such an object.[3] Some 19th century antiquarians speculated that they might be weapons, such as the head of a mace or a metal bullet, but other scholars have suggested that the dodecahedrons are too light to make for an effective weapon.[3]

A further suggestion as to the purpose of these artifacts is that of nighttime candle clocks with each face with its unique diameter circular hole designed with candles of appropriate sizes to match the mean length of night for each month of a year and for the specific latitude where each example was made for. A full description of this hypothesis can be found at Gallo Roman Dodecahedron, A Night Candle Clock.[13]

Similar objects

Smaller dodecahedra with the same features (holes and knobs) and made from gold have been found in South-East Asia along the Maritime Silk Road and the earliest items appear to be from the Roman epoch. Examples include those uncovered in Óc Eo by Louis Malleret, who concluded that the objects represented the influence of Mediterranean trade on the Funan economy.[14] Similar decorative gold dodecahedrons have been found in the Pyu city-states and Khao Sam Kaeo.[9][15]

References
  1. Guggenberger, Michael (2013-10-03). "The Gallo-Roman Dodecahedron". The Mathematical Intelligencer. Springer Science and Business Media LLC. 35 (4): 56–60. doi:10.1007/s00283-013-9403-7. ISSN 0343-6993. S2CID 122337773.
  2. Hill, Christopher (1994). "Gallo-Roman Dodecahedra: A Progress Report". The Antiquaries Journal. Cambridge University Press (CUP). 74: 289–292. doi:10.1017/s0003581500024458. ISSN 0003-5815. S2CID 161691752.
  3. Metcalfe, Tom (August 6, 2018). "The Mysterious Bronze Objects that Have Baffled Archaeologists for Centuries". Pocket. Mental Floss. Retrieved 17 September 2019.
  4. Benno Artmann (2012), Euclid – The Creation of Mathematics, pp. 307–308
  5. Sparavigna, A. (2012). "Roman dodecahedron as dioptron: Analysis of freely available data". arXiv:1206.0946 [physics.pop-ph].
  6. von Schmoller, Gustav (1879). "67. Rathsentscheidung in einem Streite der Tuchersunft und der Zunft zum Spiegel. dass das Hosenstricker-Handwerk ze der erstern gehöre. 1535.". Die Strassburger tucher- und weberzunft: Urkunden und darstellung nebst regesten und glossar. Ein beitrag zur geschichte der deutschen weberei und des deutschen gewerberechts vom XIII.-XVII. jahrhundert. Strassburg: Verlag von Karl J. Trübner. Retrieved 27 January 2023.
  7. Rutt, Richard (1987). A History of Hand Knitting (U.S. ed.). Loveland, Colo.: Interweave Press. ISBN 0934026351. Retrieved 27 January 2023.
  8. Spencer, David J. (2001). Knitting technology : a comprehensive handbook and practical guide (3rd ed.). Lancaster, Pa.: Technomic. ISBN 9781855737556.
  9. Bennett, Anna T.N. (2009-12-31). "Gold in early Southeast Asia". ArchéoSciences. OpenEdition (33): 99–107. doi:10.4000/archeosciences.2072. ISSN 1960-1360.
  10. Greiner, Bernhard A. (1996). "Römische Dodekaeder: Untersuchungen zur Typologie, Herstellung, Verbreitung, und Funktion". Carnuntum Jahrbuch 1995 (in German). pp. 9–44.
  11. Henig, Martin (1984). Religion in Roman Britain. Routledge. p. 128. ISBN 0-7134-6047-4.
  12. Kilford, L.J.P. (December 2004). "A mathematical tourist in Germany". Mathematics Today. Vol. 40, no. 6. p. 204.
  13. https://www.dropbox.com/pri/get/Dodecahedron/Gallo%20Roman%20Dodecahedron.docx?_subject_uid=34127042&w=AABRwbfYUDa3oJWAAP5WcHsV0CjplCFFf5Rl-vmRcFc_5g
  14. Malleret, Louis (1961). "Les dodecaedres d'or du site d'Oc-eo" [The gold dodecohedrons from the Oc-eo site]. Artibus Asiae (in French). JSTOR. 24 (3–4): 343–350. doi:10.2307/3249235. ISSN 0004-3648. JSTOR 3249235.
  15. Xiong, Zhaoming (2014). "The Hepu Han tombs and the maritime Silk Road of the Han Dynasty". Antiquity. Cambridge University Press (CUP). 88 (342): 1229–1243. doi:10.1017/s0003598x0011542x. ISSN 0003-598X. S2CID 161059940.

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