Dating the spheres
The spheres were dated in two stages using the AMS radiocarbon method, first for the terrestrial globe (in 2013) and then for the celestial globe (in 2015). The tests were run by Dr Irka Hajdas at the ETH Laboratory for Ion Beam Physics, Radiocarbon Dating in Zurich.
These AMS radiocarbon analyses dated the materials used to manufacture the spheres. Although the resulting time ranges may seem large, the exercise made it possible to state with a good degree of certainty that the UNIL globes were produced in Mercator’s workshop in the 16th century.
Ill. Rapport LRD
Two samples were drawn from the terrestrial sphere near the South Pole, one from the surface paper and the other from the substratum fibres. The substratum is composed of a textile substance but it is difficult to be more precise.
The C/N (carbon/nitrogen) ratio of an organic material indicates to what extent it has changed over time and thus the speed at which it can decompose in the ground: the higher the ratio, the slower the decomposition process. In the case of the terrestrial sphere, the paper sample had a C/N ratio of 63.32 and the textile sample a C/N ratio of 23.73. This suggests that the paper was made from a textile substance, as was common in medieval times.
| C14 radiocarbon dating yielded the following results : | ||
| Sphere, paper (surface) | 1450-1640 | probability 95,4% |
| Sphere, fibres (substratum) | 1480-1650 | probability 95,4% |
Ill. 13, Rapport SIK|ISEA
Two samples were taken from the celestial globe, one from the surface paper and the other from the substratum fibres.
| C14 radiocarbon dating yielded the following results : | ||
| Sphere, paper (surface) | 1458-1706 | probability 58,0% |
| Sphère, fibres (substrat) | 1473-1640 | probability 95,4% |
-
- Prélèvements sur le globe céleste : couche de papier et fibres (Ill. 35, Rapport SIK|ISEA)
-
- Prélèvements sur le globe céleste : échantillons de papier après nettoyage (Ill. 36, Rapport SIK|ISEA)
-
- Prélèvements sur le globe céleste : échantillons de fibres (substrat) après nettoyage (Ill. 37, Rapport SIK|ISEA)
C12 and C13 analyses of the spheres
Besides the conclusive C14 dating of the stands, additional C12 and C13 tests were conducted by Prof. Torsten Vennemann at the Institute of Earth Surface Dynamics of UNILs Faculty of Geosciences and the Environment. These tests buttressed the earlier dating observations.
-
- Fabrice Ducrest © UNIL
-
- Fabrice Ducrest © UNIL
-
- Fabrice Ducrest © UNIL
-
- Fabrice Ducrest © UNIL
-
- Fabrice Ducrest © UNIL
-
- Fabrice Ducrest © UNIL
-
- Fabrice Ducrest © UNIL
-
- Fabrice Ducrest © UNIL
-
- Fabrice Ducrest © UNIL
-
- Fabrice Ducrest © UNIL
-
- Fabrice Ducrest © UNIL
-
- Fabrice Ducrest © UNIL
-
- Fabrice Ducrest © UNIL
-
- Fabrice Ducrest © UNIL
-
- Fabrice Ducrest © UNIL
Find out more
- Rapport d’analyse radiocarbone par AMS, Globe terrestre : AMS radiocarbon analysis report on the terrestrial sphere, West Swiss Laboratory of Dendrochronology, N° réf. LRD12/R6756R, 02.09.2013, Jean Tercier & Jean-Pierre Hurni, Moudon.
- Les globes de Mercator de l’Université de Lausanne. Observations matérielles. Constat d’état. Rapport de conservation-restauration : The Mercator globes of the University of Lausanne. Material observations. Condition report. Report on conservation-restoration, Workshop and laboratory of the Swiss Institute for Art Research SIK-ISEA, N° réf. 141110 0002 : 01/02, October 2015, Margaux Genton, Zürich.