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