virtual laboratory for archaeometry
dubal (at) archaeometry.org
History starts when
a group of people agrees
to share a common way to count time.
A calendar represents therefore a symbol of identity,
which contributes to the feeling of belonging to a community.
Who knows if sharing a calendar is not a more powerful discriminating factor
than sharing a common territory ?
Therefore there is not ONE and only ONE History,
but as many as there are cultural & calendrical eras.
The timeline of a cultural era starts with YEAR 1,
the commemorated date of the mythical founding act of this era, e.g.:
The French Republican calendrical era starts on Vendémiaire 1st, Year 1,
but...it has been introduced only later, i.e.: on Vendemiaire 15th, Year 2 !
Its period of use extends from Year 2 up to Year 79, a relatively short time.
Other mythical calendrical era founding events are:
for the Seleucid Era, SE: Babylon's mythical take-over by Seleukos
then (for Syrians) Gaza's mythical battle.
for Ab Urbe Condita Era, AUC: Rome's mythical fundation by Romulus
for the Hispanic Era or Safar date, ERA: Iberic penninsula's mythical romanization.
for the Anno Hegirae or Hijri Era, AH: from Mecca to Medina
mythical migration from a muslim tribe.
for the Anno Domini, AD: the mythical Incarnation of the Lord,
in contrast to calendrical eras,
necessitates a secular & universal reference time-scale.
The astronomer Johannes Kepler introduced such a time scale he called vulgaris aerae.
He kept the length of the year the same as the one of the alexandrian astronomer Sosigene,
and set the current year on his time scale to +1616, in agreement with 1616 AD,
as during his lifetime, the Anno Domini calendar was broadly used in Europe.
One century later, Kepler's secular timescale has been renamed as
Common Era or CE.
one would tune the
remaining 5 strings to this same frequency,
by cliping them with a finger in the prescribed position, see below:
As we all know there exists "no external event generator" to tune Kepler's secular timescale.
Nevertheless some natural events have been reported in terms of various timelines.
To illustrate this point, let us look at one
piece of archives of Coimbra
I discovered recently in : http://digitarq.arquivos.pt/viewer?id=1457770
Thanks to Xavier Jubier 5 Millenium Corpus of
which is directly coupled to GoogleEarth,
one can (with some training) easily find out to which solar eclipse this annal is refering to:
Therefore, it turns out that year 1117 ERA corresponds to +1079.07.01 CE
Those findings are discused in details
in Portuguese: http://www.archaeometry.org/eraPT.pdf
in Spanish: http://www.archaeometry.org/eraES.pdf
in Catalan: http://www.archaeometry.org/eraCT.pdf
in French: http://www.archaeometry.org/era.pdf
The table below gives a list of
ancient solar eclipses
reported in terms of various timelines:
Let us position those data onto the guitar-like chart:
Using Kepler secular timeline we have retro-dated
One sees that 2 solar eclipses have been recorded in terms of Seleucid Era with a 13 centuries timespan!
This timespan indicate to us that the period of use of SE extends to at least this time laps,
while Common Era has only been in used from 1616 on.
In order to find out the extend of the period of use of the eras discussed here,
one will have to look for some other kinds of artefact.
The colophon of an
artefact provides its date and site of
e.g.: the colophon of the above pictured conical guitar...
For ancient colophons labelled in terms of various calendrical eras, see:
Those colophons are the key-stones to establish the duration of
the period of use of a given timeline.
One should be aware that :
the introduction of new
eras might be the fact of a sole individual (Varro, Bede)
and that the earliest year given on colophons might amount up to several hundreds,
making difficult to retrodate down to the mythical Year 1 of those eras (AUC, AD) .
- the beginning of the year might swap season (and even mythical founding event)
during its period of use (SE).
- it might take decades until some authorities declared official a given era (ERA).
- the choice of astral cycle (lunar, solar...) might differ (AH)
While myths escape
chronology, nothing prevents one
to retro-compute the correspondance, to Common Era, of a mythical Year 1,
even far beyond the lowest limit of the period of use of its calendrical era:
Year 1 of the Seleucid Era corresponds
to year -310 CE.
This era has been promoted 30 years after the death of the dictator Seleukos
probably by babylonian astronomers and it remained in use until printing's invention.
- Year 1 of the Ab Urbe Condita era corresponds to year -753CE.
This era has been promoted by Varo in year 700 AUC.
- Year 1 of ERA corresponds to year -38 CE.
In 554 ERA, i.e. 74 years after the 1st use of this era in funerary art,
the arianist Council of Tarragona officialised this calendar,
- Year 1 of Hijri era correponds to year +622 CE.
The promotion of this calendrical era took place prior to year 67 AH.
- Year 1 of Anno Domini corresponds to year +1 CE.
This era has been promoted by the Venerable Bede probably around 725 AD.
summarize, let us now integrate
- Dual-date of anchoring solar eclipse
- Period of use of calendrical era
- Mythical Year 1
into the guitar-like timelines chart: