g'day chris here and welcome back to Clickspring so after much work on the structure and gearing
of the mechanism we can now have a look at what it was all designed to do and starting
with the back plate the remains of the device have proven to be just enough for various
researchers to piece together the likely markings revealing much about both the machine itself
and the world in which it was constructed this includes as a major feature what is probably
the most complete calendar from the ancient greek world a lunar solar calendar based upon
the 19-year Metonic cycle with the 235 lunar months laid out around a five-turn spiral
there are also two subsidiary dials one observable in the wreckage and the other assumed as well
as some more subtle markings that permit correct interpretation of the dial the dial was designed
to give the user a lot of information all at once and some of it is quite unfamiliar
from our modern perspective the commonly used Gregorian calendar for example has a very
different structure so this presentation isn't immediately recognizable to most of us and
so requires a little decoding so let's start with the building blocks of the calendar those
small cells that represent the lunar months the Ancient Greeks made sure that their months
would ideally follow the phases of the moon the first of the month was the day after New
Moon when theoretically a small sliver would first be visible at sunset the 15th was around
the middle of the month at Full Moon and the end of the month was defined as when the moon
was no longer visible or New Moon
each of these cycles was defined as a month and naturally enough given a name and while
we're on the subject of names there was a fair amount of regional variation in the month
names but there was also some interesting overlap and commonality to the extent that
month names tend to be a useful tool in determining the regional origin of a given calendar and
as we'll go through later the presence of a specific set of month names on the mechanism
has been used to do just that
in any event 12 lunar months in series was the most basic representation of any given
local calendar as appropriate to the region the 12 months was cycled through in accordance
with a system of regulation that served to synchronize what was in practice a lunar cycle
based calendar with the local seasons now that system of regulation happens to be a
critical aspect of how the whole thing worked because as convenient as it is to have a calendar
based upon months that anybody can simply look at the sky to verify a series of 12 lunar
cycles as measured in days falls well short of a solar year and of course the length of
a lunar month is also not a neat integer number of days without some sort of remedy before
long the months would drift noticeably from the seasons and the lunar phase would drift
out of alignment with the months a solution well known in the ancient world was to use
a set of rules to specify when there should be an additional or intercalary 13th month
to maintain seasonal alignment and when a given month was to be of either 29 or 30 day
duration and in our case that system is the Metonic calendar
it's a calendar based around the fortunate coincidence i mentioned in a previous video
where 235 lunar months almost exactly equals 19 solar years this permits a close enough
whole number reconciliation between the solar and lunar cycles over those periods hence
the name "lunisolar calendar" the 235 months were laid out in a radial pattern of five
spirals each of 47 cells with the dial divisions running radially directly across each of the
spiral turns
the display was intended to run clockwise out from the centre
years were presented in sequence from 1 to 19 around the spiral
seven of the years were intercalary years and so 13 months in duration and it's believed
that these intercalary years were spread out relatively evenly across the sequence of 19.
all months were nominally presented as being 30 days in duration or what's known as 'full'
however 110 months were prescribed to drop a day to be 29 days in duration and so become
'hollow' 110 being neatly divisible by five means that on a five spiral dial these hollow
months can be conveniently displayed as 22 regularly spaced groups of five sharing the
same radial sector and the evidence suggests that the index numbers associated with each
radial sector specified which day of each of those months was to be skipped so for example
each month on this sector is hollow so of 29 days duration and skipped day 23
this clever use of the neat divisibility of both 110 and 235 by five is the reason behind
the five spiral layout of this style it was an intentional choice of the maker to make
use of what amounts to five sub-cycles of 47 to simplify the presentation of the full
sequence of 235 months this choice permitted a compact and predictable display of the Metonic
cycle and also ensured just enough space for each cell to contain a legible text engraving
of each month name and speaking of month names let's go through them now as I mark out the
dial in preparation for engraving all of the text on the device is of course inscribed
in ancient Greek which means the text is in all capitals there are no spaces accents or
punctuation and often ancient Greek tends to be written as blocks of text but in the
case of the month names on this mechanism they're divided mostly by syllable over two
or three lines with the smallest characters just a little over one millimeter tall
okay so the month names in sequence are Phoinikaios
Kraneios
Lanotropios
Machaneus the month now understood to be the intercalary month
Dodekateus
Eukleios
Artemisios
Psydreus
Gameilios
Agrianios
Panamos
and finally Apellaios
now disputes regarding pronunciation aside if
you've followed along reading these names out loud for yourself then congratulations
because you've just given voice to the month names of a very old calendar the complete
list and month order of which only became known with the rediscovery of the mechanism
the calendar is understood to be of Corinthian origin and most likely from the ancient region
of Epirus an area now shared between north western Greece and southern Albania and its
existence on the mechanism suggests an association between the device and this region now the
main calendar was intended to be interpreted in context with its subsidiary dials the games
dial and the assumed Callippic dial each of these dials was divided into four sectors
with each quadrant of the Callippic dial indicating progress of the Callippic cycle and each quadrant
in the Games dial indicating the sequence of the pan-Hellenic games with this dial in
particular set a few degrees anti-clockwise relative to the natural axis of the plate
the text of the Games dial may provide an indication of where the device was constructed
Derek de Solla Price first put forward the idea that the mechanism may have been associated
with the device making tradition of Rhodes and more recently the reading of the relatively
low significance Alieian games of Rhodes on this Dial has been interpreted as possibly
supporting that suggestion
okay so that's the top half of the plate marked out time to make a start on the engraving
the remains of the mechanism suggest a burin style cutting tool with a v-shaped cutting
face in the modern context the cutting edge of an engraving tool is usually modified to
include a small heel to reduce the tendency for the tool to dig in and that heel is sized
according to the preference of each engraver but one thing common to all engraving cutters
is that they must be quite hard and able to retain a very sharp edge to be capable of
doing an acceptable job so again we have a reason to investigate what sort of material
was used for this cutting tool to make the cleanly inscribed cuts that we can see in
the remains of the mechanism the tempered martensite that i've shown in use in previous
episodes is again an excellent candidate to consider for those that haven't yet seen those
videos it's a carburized iron that could have been quite easily produced on demand in the
ancient workshop using commonly available materials it can be quenched in water to a
glass martensitic state but in its annealed state it can be fairly easily worked into
just about any required shape using files or abrasive stones in this case I formed a
roughly 90 degree v-shaped cutting edge with a slight taper towards the cutting face
the material is then taken to a red heat and quenched again to transform it back into martensite
the material is then tempered back slightly and finally sharpened on abrasive stones
the metal is still very hard but importantly also now tough enough to accept a sharp edge
and able to retain that edge and the heel facets throughout the cutting process ensuring
a consistent and repeatable engraving standard across the workpiece
now my preference is to use a hammer to drive the cutter but it could just as easily have
been used as a push engraver depending on the maker's preference the objective in each
case being maintaining careful control of the cut
the tool preparation may have had a few extra steps but from here the workflow is much the
same as for a modern engraver importantly the tool handles as expected and the cutter
forms bright chips generating the clean edge cuts that can be seen in the remains of the
mechanism
the text that can be viewed on the original mechanism provides some guidance to follow
for the ancient Greek lettering style and there's some interesting detail on the characters
to be found in the scans much of the lettering is serifed which gives it quite a formal appearance
Pi is the first character to catch the eye with its unequal legs the second a little
shorter than the first and with a slight curl or a more pronounced serif
Sigma also has an interesting appearance not always but often with its top and bottom lines
a little splayed as opposed to horizontal and Mu often has a similar kind of splay with
the two outside lines at an angle rather than vertical
Upsilon often has a short vertical stroke Phi has a slightly flattened appearance and
Omicron is well represented as the "little o" often raised relative to the other text
now the significance of all of this is open for interpretation much of it could simply
be a result of tiny engraved characters being forced into a small space but there's been
quite a bit of discussion on it all so be sure to check out the research linked in the
description for more detail
in any event the engraving work itself is a time consuming task making this component
easily the most labor-intensive of the build so far
so as we approach the completion of this section of the plate it's worth pointing out that
numbers on the mechanism are indicated using the Greek letters-for-numbers system where
for example the alpha character represents one beta 2 gamma 3 and so on a good example
to see this in use is the Games dial when combined with the L-shaped symbol for year
the letters alpha beta gamma and delta represent the first second third and fourth years of
the Games cycle
and we also see this system used for the skipped days of the hollow months the months on the
radial sector corresponding with alpha skip day 1 with epsilon day 5 with theta day 9
for higher numbers the numbering system is additive so for example iota gamma represents
10 plus 3 or 13.
iota theta 19 kappa gamma 23 and so on
and so the mechanism provided the user with a comprehensive layout of the excluded days
of each month for the entire 235 month cycle now i'll go through how the gains and Callippic
dials are ready in conjunction with this Metonic calendar and the rest of the backplate in
the next video but for now let's put all of this together and have a go at reading just
the calendar for example this stretch of 12 cells represents a single 12 month year the
first sell of the year as always is the month Phoinikaios and we see the L-shaped year symbol
followed by an epsilon so we know that this year is year five as an example the seventh
month of this year Artemisios has no characters inscribed on the inside of its radius segment
so we know that in this year Artemisias is a full month with 30 days however the very
next month along Psydreus does have a number on the inside of its radius so we know that
it's a hollow month of 29 days the characters kappa alpha indicate the number 21 so we know
that there's no 21st day for the month of Psydreus in the fifth year of the Metonic
cycle
now that was a year of 12 lunar months duration let's try another one this time an intercalary
year this year is 13 lunar months in duration and a closer look at that first cell tells
us that it's year 9.
as an intercalary year it has an additional intercalary month of Machaneus immediately
following the standard month of Machaneus
and with no number on the inside of its radius segment we can confirm that this additional
month is a full 30 days in length
however the preceding month does have a number on the inside radius so we know that it's
hollow and that there's no 17th day for this month of Machaneus in the ninth year of the
Metonic cycle
now all of this takes quite a bit to get used to so be assured we'll go through it all again
in part two of this video when I cover the inscriptions for the Saros dial but with this
section of the dial reconstructed another small test is complete that shows like so
many of the other cut features a simple tempered martensite cutting tool is quite capable of
producing the fine crisply engraved detail that can be observed in the wreckage of the
Antikythera Mechanism thanks for watching i'll see you later