January 23, 2007
as it appears today, with x-rays superimposed;
from Jo Marchant's
'In search of lost time' (Nature)
A recent issue of the British scientific
journal Nature (dated 2006-11-30) has several fascinating articles
including a research report on the Antikythera Mechanism, in which a
battery of powerful techniques including x-ray computed tomography,
high-resolution surface examination together with much painstaking
analysis have, more than a century after its discovery at the bottom
of the sea, begun to reveal the fascinating secrets of this ancient
As Jo Marchant puts it in her
companion piece “In search of lost time”: 1
It looks like something from another
world — nothing like the classical statues and vases that fill
the rest of the echoing hall. Three flat pieces of what looks
like green, flaky pastry are supported in perspex cradles.
Within each fragment, layers of
something that was once metal have been squashed together, and
are now covered in calcareous accretions and various corrosions,
from the whitish tin oxide to the dark bluish green of copper
chloride. This thing spent 2,000 years at the bottom of the sea
before making it to the National Archaeological Museum in
Athens, and it shows.
But it is the details that take my breath away. Beneath the
powdery deposits, tiny cramped writing is visible along with a
spiral scale; there are traces of gear-wheels edged with jagged
teeth. Next to the fragments an X-ray shows some of the object’s
internal workings. It looks just like the inside of a
This is the Antikythera Mechanism. These fragments
contain at least 30 interlocking gear-wheels, along with copious
astronomical inscriptions. Before its sojourn on the sea bed, it
computed and displayed the movement of the Sun, the Moon and
possibly the planets around Earth, and predicted the dates of
future eclipses. It’s one of the most stunning artefacts we have
from classical antiquity.
No earlier geared mechanism of any sort has ever been found.
Nothing close to its technological sophistication appears again
for well over a millennium, when astronomical clocks appear in
medieval Europe. It stands as a strange exception, stripped of
context, of ancestry, of descendants.
Considering how remarkable it is, the Antikythera Mechanism has
received comparatively scant attention from archaeologists or
historians of science and technology, and is largely
unappreciated in the wider world. A virtual reconstruction of
the device, published by Mike Edmunds and his colleagues
in this week’s Nature (see page 587), may help to change that.
With the help of pioneering
three-dimensional images of the fragments’ innards, the authors
present something close to a complete picture of how the device
worked, which in turn hints at who might have been responsible
for building it.
Now that close to a comprehensive
understanding of the Antikythera Mechanism has emerged from these
studies, the picture of the revealed machine is astounding:
Rear side, sideways
view of reconstruction of Antikythera Mechanism;
Charette, 'High tech from Ancient Greece' (Nature)
Schematic diagram of gear trains, as per Price and Wright;
from T. Freeth et al.
'Decoding the ancient Greek astronomical calculator
known as the
Antikythera Mechanism' (Nature)
Diagram showing position of principal dials and inscriptions;
from T. Freeth et al.
'Decoding the ancient Greek astronomical calculator
known as the
Antikythera Mechanism' (Nature)
Reading the research report’s
description of its analysis of the dials and inscriptions on the
device is almost like reading an alternate history novel (a sequel
to a book by L. Sprague de Camp, say, The Glory that Was),
where science took off in antiquity and all this arcane technology
that results is accompanied by an impressive Ancient Greek technical
vocabulary… except that this is our timeline.
Prior to historians and archaeologists’ realization of what the
Antikythera mechanism really was, scholars had no reason to think
that ancients were aware of the principle of clockwork-like complex
gearing at all.
Via the 1st century b.c.
Roman architect writer Vitruvius, we know that simple dual
gearing, for directional change, was in use following this time
frame in a type of water-powered mill. There are still no instances
known of the use of gears of any type predating the Antikythera
mechanism, however, nor anything of comparable sophistication for
beyond a thousand years after.
A revealing excerpt from the Nature report, “Decoding
the ancient Greek astronomical calculator known as the Antikythera
Mechanism,” by Tony Freeth (Cardiff University,
School of Physics and Astronomy), et al., reads as follows: 2
Named after its place of discovery
in 1901 in a Roman shipwreck, the Antikythera Mechanism
is technically more complex than any known device for at least a
millennium afterwards. Its specific functions have remained
controversial because its gears and the inscriptions upon its
faces are only fragmentary.
Here we report surface imaging and
high-resolution X-ray tomography of the surviving fragments,
enabling us to reconstruct the gear function and double the
number of deciphered inscriptions. The mechanism predicted lunar
and solar eclipses on the basis of Babylonian
arithmetic-progression cycles. The inscriptions support
suggestions of mechanical display of planetary positions, now
lost. In the second century b.c., Hipparchos developed a
theory to explain the irregularities of the Moon’s motion across
the sky caused by its elliptic orbit.
We find a mechanical realization of
this theory in the gearing of the mechanism, revealing an
unexpected degree of technical sophistication for the period.
The bronze mechanism (Fig. 1), probably hand-driven, was
originally housed in a wooden-framed case of (uncertain) overall
size 315 × 190 × 100 mm (Fig. 2). It had front and back doors,
with astronomical inscriptions covering much of the exterior of
the mechanism. Our new transcriptions and translations of the
Greek texts are given in Supplementary Note “glyphs
and inscriptions”. 2
The detailed form of the lettering
can be dated to the second half of the second century B.C.,
implying that the mechanism was constructed during the period
150-100 B.C., slightly earlier than previously suggested. This
is consistent with a date of around 80-60 B.C. for the wreck
from which the mechanism was recovered by some of the first
We are able to complete the
reconstruction of the back door inscription with text from
fragment E, and characters from fragments A and F (see Fig. 1
legend for fragment nomenclature). The front door is mainly from
The text is astronomical, with many
numbers that could be related to planetary motions; the word
“sterigmos” (ΣΤΗΡΙΓΜΟΣ, translated as “station” or “stationary
point”) is found, meaning where a planet’s apparent motion
changes direction, and the numbers may relate to planetary
cycles. We note that a major aim of this investigation is to set
up a data archive to allow non-invasive future research, and
access to this will start in 2007. Details will be available on
The back door inscription mixes mechanical terms about
construction (“trunnions,” “gnomon,” “perforations”) with
astronomical periods. Of the periods, 223 is the Saros eclipse
Box 1 for a brief explanation
of astronomical cycles and periods). We discover the inscription
“spiral divided into 235 sections,” which is the key to
understanding the function of the upper back dial.
The references to “golden little
sphere” and “little sphere” probably refer to the front zodiac
display for the Sun and Moon — including phase for the latter.
The text near the lower back dial includes “Pharos” and “from
south (about/around)… Spain (ΙΣΠΑΝΙΑ) ten.”
These geographical references,
together with previous readings of “towards the east,”
“west-north-west” and “west-south-west” suggest an eclipse
function for the dial, as solar eclipses occur only at limited
geographical sites, and winds were often recorded in antiquity
with eclipse observations. Possibly this information was added
to the mechanism during use.
Turning to the dials themselves, the front dial displays the
position of the Sun and Moon in the zodiac, and a corresponding
calendar of 365 days that could be adjusted for leap years.
Previously, it was suggested that the upper back dial might have
five concentric rings with 47 divisions per turn, showing the
235 months of the 19-year Metonic cycle.
A later proposal augments this with
the upper subsidiary dial showing the 76-year
Callippic cycle. Our optical
and X-ray micro-focus computed tomography (CT) imaging confirms
these proposals, with 34 scale markings discovered on the upper
back dial. On the basis of a statistical analysis analogous to
that described for gear tooth counts below, we confirm the 235
We also find from the CT that the
subsidiary dial is indeed divided into quadrants, as required
for a Callippic dial. In agreement with the back door
inscription, we also substantiate the preceptive proposal that
the dial is in fact a spiral made from semicircular arcs
displaced to centers on the vertical midline. In the CT of
fragment B we find a new feature that explains why the dial is a
spiral: a “pointer-follower” device (Fig. 3) traveled around the
spiral groove to indicate which month (across the five turns of
the scale) should be read.
From our CT data of the 48 scale divisions observed in fragments
A, E and F, we establish 223 divisions in the four-turn spiral
on the lower back dial, the spiral starting at the bottom of the
dial. This is the Saros eclipse cycle, whose number is on the
back door inscription. The 54-year Exeligmos cycle of three
Saros cycles is shown on the
lower subsidiary dial.
Between the scale divisions of the Saros dial we have identified
16 blocks of characters, or “glyphs” (see “glyphs and
inscriptions”) at intervals of one, five and six months. These
are eclipse predictions and contain either Σ for a lunar eclipse
(from ΣΕΛΗΝΗ, Moon) or Η for a solar eclipse (from ΗΛΙΟΣ, Sun)
A correlation analysis (analogous to
DNA sequence matching) with historic eclipse data (all modern
eclipse data and predictions in our work are from this
reference) indicates that over a period of 400-1 b.c., the
sequence of eclipses marked by the identified glyphs would be
exactly matched by 121 possible start dates. The matching only
occurs if the lunar month starts at first crescent, and confirms
this choice of month start in the mechanism.
The sequences of eclipses can then
be used to predict the expected position of glyphs on the whole
dial, as seen in Fig. 4. The dial starts and finishes with an
eclipse. Although Ptolemy indicates that the Greeks recorded
eclipses in the second century b.c., the Babylonian Saros canon
is the only known source of sufficient data to construct the
Of particular note is the dual use of the large gear, e3, at the
back of the mechanism, which has found no use in previous
models. In our model, it is powered by m3 as part of a
fixed-axis train that turns the Saros and Exeligmos dials for
eclipse prediction, and also doubles as the “epicyclic table”
for the gears k1, k2.
These are part of the epicyclic
gearing that calculates the theory of the irregular motion of
the moon, developed by Hipparchos some time between 146 and 128
b.c. (ref. 22) - the “first anomaly,” caused by its elliptical
orbit about the Earth. The period of this anomaly is the period
from apogee to apogee (the anomalistic month).
To realize this theory, the mean
sidereal lunar motion is first calculated by gears on axes c, d
and e and this is then fed into the epicyclic system. As
explained in Fig. 6, a pin-and-slot device on the epicyclic
gears k1 and k2, clearly seen in the CT, provides the variation.
This was previously identified, but rejected as a lunar
The remarkable purpose of mounting
the pin-and-slot mechanism on the gear e3 is to change the
period of variation from the sidereal month (that is, the time
taken for the moon to orbit the Earth relative to the zodiac),
which would occur if k1 and k2 were on fixed axes, to
anomalistic month — by carrying the gears epicyclically at a
rate that is the difference between the rates of the sidereal
and anomalistic months, that is, at the rate of rotation of
about 9 years of the Moon’s apogee.
Gears with 53 teeth are awkward to divide. So it may seem
surprising that the gearing includes two such gears (f1, l2),
whose effects cancel in the train leading to the Saros dial. But
the gearing has been specifically designed so that the
“epicyclic table” e3 turns at the rate of rotation of the Moon’s
apogee — the factor 53 being derived from the calculation of
this rotation from the Metonic and Saros cycles, which are the
bases for all the prime factors in the tooth counts of the
The establishment of the 53-tooth
count of these gears is powerful confirmation of our proposed
model of Hipparchos’ lunar theory. The output of this complex
system is carried from e6 back through e3 and thence, via e1 and
b3, to the zodiac scale on the front dial and the lunar phase
mechanism. Our CT confirms the complex structure of axis e that
this model entails.
The Antikythera Mechanism shows great economy and ingenuity of
It stands as a witness to the
extraordinary technological potential of Ancient Greece,
apparently lost within the Roman Empire.
'Pointer-follower' device for spiral dial as it appears in x-ray
from T. Freeth et
ancient Greek astronomical calculator known as the Antikythera
Map of the
Mediterranean, showing Antikythera area in inset;
from Jo Marchant, 'In
search of lost time' (Nature)
Raised From The Depths
by Jo Marchant
Nature 444, 534-538
(30 November 2006)
In 1900 a party of
Greek sponge divers sought shelter from a storm in the
lee of the barren, rocky islet of Antikythera. Once the
winds had eased, Elias Stadiatis dived 42 meters to a
rocky shelf to look for late additions to his
hard-earned haul. Instead of sponges nestled on the sea
bed, the shape of a great ship loomed out of the blue.
After grabbing the
larger-than-life arm of a bronze figure as proof of his
find, he returned to the surface to inform his
companions. The Antikythera wreck was to yield a
stunning collection of bronze and marble statues,
pottery, glassware, jewellery and coins; it was also to
claim the life of one of the divers, not yet aware of
the risk of the bends when diving with an oxygen hose.
As busy museum staff struggled to piece together statues
and vases, a formless, corroded lump of bronze and wood
lay unnoticed. But as the wood dried and shrivelled, the
lump cracked open, and on 17 May 1902, archaeologist
Valerios Stais noticed that there were gear-wheels
The gears elicited interest, but it was not until
investigations delved beneath the surface that the box
started to yield its secrets. The British science
historian Derek de Solla Price and the Greek nuclear
physicist Charalampos Karakalos made X- and gamma-ray
images of the fragments in 1971. Karakalos and his wife
Emily painstakingly counted the visible teeth; in 1974
Price published a heroic 70-page account of the machine
(D. de S. Price Trans. Am. Phil. Soc., New Ser.64, 1–70;
"Price really put the mechanism on the map," says Tony
Freeth, co-author of a new reconstruction of the device
(see page 587). "He understood the essence of what it
was — an astronomical computer." But Price massaged some
of the data (much to the annoyance of Karakalos and his
wife), and his reconstruction was unnecessarily
complicated — perhaps too complicated for historians and
archaeologists. They largely ignored Price's work, and
he died in 1983.
That same year, a Lebanese man walked into the Science
Museum in London with the pieces of another ancient
mechanism in his pocket. Curator Michael Wright realized
the device was a Byzantine sundial from the sixth
century AD, which also contained a simple geared
mechanism that drove pointers showing the position of
the Moon and Sun in the sky. Studying the astronomically
enhanced sundial led Wright to Price's treatment of the
Antikythera Mechanism, in which he saw serious holes.
Wright ended up working with Allan Bromley, a computer
scientist at Sydney University in Australia who had
become interested in the Antikythera Mechanism at around
the same time. Bromley wanted to study the machine with
X-ray tomography, which assembles a sheaf of
cross-sections of its subject.
As the fragments
could not be moved from the museum, and Bromley didn't
have the money to ship a tomography machine to Athens,
Wright used his tool-making skills to build a crude
tomograph in situ. The two researchers took around 700
images of the fragments, and Wright has been working on
a reconstruction that supercedes Price's ever since.
In the meantime, Mike Edmunds, an astrophysicist at
Cardiff University, UK, and his friend Tony Freeth, a
mathematician-turned-film-maker living in London,
decided the mechanism would make a fantastic subject for
a documentary. But their efforts soon turned to
discovering more about how the device worked.
Hewlett-Packard, which had developed a method for
reading eroded cuneiform tablets that involved building
up a composite computer image from pictures taken under
light from a wide variety of directions, to reveal more
of the inscriptions.
experts in computer-assisted tomography from British
firm XTEC, which developed a new machine just for the
In search of lost time M. KIRK
Derek de Solla Price tried to undo the Antikythera
In autumn 2005, the
Hewlett-Packard equipment and all 12 tonnes of XTEC's
machinery were shipped to the museum. The results have
allowed the team to confirm many of Wright's ideas, and
extend them. "My main fear initially was that we'd throw
all this technology at it and we wouldn't do more than
dot the i's and cross the t's," says Freeth. "But we got
more out of it than I dared hope."
One major new result came as much from chance as from
technology; a key section of a dial found sitting
unnoticed in the museum's store room helped reveal that
one of the dials was used to predict eclipses. Another
big discovery was the identification of a 'pin and slot'
mechanism to model the varying speed of the Moon through
the sky (see main story).
The inscriptions are also revealing novelties, although
deciphering them is hard work: some of them are less
than 2 millimetres high, and there are no spaces to show
where each word starts and finishes. Agamemnon Tselikas,
director of the Centre for History and Palaeography in
Athens, spent a concentrated three months trying to
decipher the wording, working from late at night into
the early hours of the morning: "I needed the silence."
So far Tselikas and his colleague Yanis Bitsakis have
more than doubled the number of legible characters on
the mechanism, which seem to form a manual that explains
how the mechanism was to be used.
"imagination and intuition" to decipher the
inscriptions, says Tselikas.
"We are just
starting to penetrate the mentality of the user of
Intriguing questions demanded by the mere existence of an ancient
device of the sophistication and elegance of the Antikythera
mechanism, of course, include where did it come from, and who built
The wreck on which the toponymically
named mechanism was found, had foundered off the island of
Antikythera, lying at the western extremity of the Aegean Sea
directly astride important trade routes connecting the Aegean —
places like Rhodes, a principal trading entrepot, along with points
east and north (e.g., Pergamon) — with the western Mediterranean,
most importantly the city of Rome itself.
Given the cargo of luxury goods aboard
(originating to the east of the ship’s final resting place), it
seems very likely that the vessel was indeed bound west, quite
probably for Rome, when it abruptly sank in 42 meters (138 feet) of
Where then did the mechanism originate and who might have made it?
A clue is provided by the fact that in
addition to the famous mechanism the ship also carried luxury trade
goods which have been identified as originating at Rhodes, as well
as other goods that are from Pergamon but which may have been
transshipped through Rhodes.
As noted before, the Antikythera device
itself contains an algorithm built-in to express the “first anomaly”
of lunar motion which was worked out in the 2nd century b.c. by the
Greek astronomer Hipparchos — perhaps greatest of ancient Greek
astronomers; who indeed did much of his work at Rhodes — and on
which island afterwards the philosopher Poseidonius
(contemporaneously regarded as the most learned man of his age; who
did astronomical work himself, and at one point instructed Cicero at
Rome) established a school.
Hence the hypothesis that Poseidonius’ school at Rhodes developed
the technological traditions — that may have been directly
influenced by Hipparchos himself, and which must have taken a good
long while to gestate, as the Antikythera mechanism clearly didn't
spring whole-cloth out of nowhere — leading to the construction of
the machine and others like it; one of which was sent off to Rome.
It never made it, and the rest is
(latter day) history.
eight-geared lunisolar calendar
astrolabe treatise of 996 AD
Beyond its jaw-dropping technology and
fascinating provenance, the question of what effect the discovery
and decipherment of this ancient technology has on our understanding
of history itself, as Jo Marchant observes in her Nature companion
piece, is perhaps even more intriguing.
As she notes, prior to the Antikythera
device it was believed that the advent of clockwork-type mechanisms
in 14th century Medieval Europe represented the invention of this
fundamental technology at around something like that time frame.
Since Antikythera, however, a geared 6th
century a.d. Byzantine sundial with four surviving gears (and which
probably originally incorporated at least eight) has turned up;
4, 5 while the Medieval Persian scholar/scientist al-Biruni
described a “box of the Moon” that is quite like the Byzantine
device. (See at right an illustration of an eight-geared lunisolar
calendar from al-Biruni’s astrolabe treatise of 996 a.d.)
Such an augmented astrolabe from 13th
century Iran is still extant today. The step from that to the clocks
of 14th century Europe is chronologically and technologically short.
Thus, the history of gearing and clockwork is being revolutionized.
Instead of originating late in the Medieval era, as previously
assumed (in a form we now see as suspiciously like that of the
Antikythera mechanism), now it appears likely that the tremendously
sophisticated gear-work that we see reflected in this machine
continued to survive in some form in the Greco-Roman world, as
displayed in the 6th century Byzantine device; from
whence it found a refuge somewhere during the early Medieval period
— perhaps in the Baghdad Caliphate — and it may well be that (after
say the Mongol destruction of Baghdad during the 13th century) this
technology thereupon migrated with scholarly refugees and ended up
influencing the West’s own technological trajectory a century or so
As François Charette observes in his Nature companion piece “High
tech from Ancient Greece,” 6 all this is not unlike us
one fine day discovering that steam engines had actually been
invented during the Renaissance, and Newcomen and Watt’s invention
of improved steam engines during the 1700’s unbeknownst to us had
ultimately derived from that.
Dane looks out over the Martian ruins;
in H. Beam Piper's 'Omnilingual'
An echo with speculative literature is
found in the way that the deciphering of the Antikythera mechanism
utilized such details as the number of teeth in the assorted gears
(unique ratios identifying which heavenly phenomena are being
computed or charted on the dials of the machine) along with such
things as historic eclipse patterns (the Saros canon) as important
indicators of its meaning and function and aids in reconstruction of
This sense of using natural law and
natural history as one’s keys to the decipherment, is very much akin
to a classic science fiction tale from half a century ago, in which
scientists investigating the remains of a disappeared alien race and
civilization on their home world (Mars), in attempting to decipher
their language — which seemed inherently almost impossible due to
lack of a “Rosetta stone” (like the original that assisted in the
decipherment of Ancient Egyptian) — ultimately came to realize that
science (natural law), knowledge of which was embedded in the
technology and writings of the science-savvy aliens, would serve as
their universal Rosetta stone.
That story is “Omnilingual” by H. Beam Piper, 7 first
published just fifty years ago, in the February 1957 (1957-02) issue
of the extremely influential science fiction magazine then known as
Astounding Science Fiction, altered a few years later to the
still-extant name of
Astounding/Analog for many years was
under the inspired editorship of very well-regarded science fiction
author John W. Campbell, Jr. — who has since become even
better known as the “father of modern science fiction,” as a result
of his tutelage and inspiration of a whole generation and host of
talented writers — Heinlein, Asimov, Clarke, van Vogt, Poul
Anderson, the list goes on and on…
Piper’s story, I’d venture to suggest,
shows every sign of having profited from Campbell’s famous idea
generation process vis-a-vis his authors.
is no longer under copyright today, and can be accessed, with its
original Kelly Freas illustrations from Astounding and blurb by John
The story concludes with the archaeologists reveling in having
finally begun comprehending the rudiments of the structure of the
Martians’ language, using the periodic table of the elements as a
starting point — in the course of which Martha Dane compliments one
of her colleagues:
“You said we had to find a
bilingual,” she said. “You were right, too.”
“This is better than a bilingual, Martha,” Hubert Penrose said.
“Physical science expresses universal facts; necessarily it is a
universal language. Heretofore archaeologists have dealt only
with pre-scientific cultures.”
As we see with the Antikythera
mechanism, one need not go to Mars or Alpha Centauri to encounter a
scientific culture in archaeology.
However, one can’t help but wonder…
Had any of the scientists who
deciphered the Antikythera machine read “Omnilingual,” lo
these many years before or at some moment since?
Did it influence their work, or
even career; did they realize they were retracing the steps,
in a sense performing the verification of a scientific
hypothesis, which is implicit in the story?
Martian City in H.
Beam Piper's 'Omnilingual'
in Feb. 1957
Astounding (Kelly Freas)
Jo Marchant, “In search of lost
time,” Nature, Vol. 444, Issue No. 7119 (issue dated
2006-11-30), pp. 534-538; doi:10.1038/444534a. See also Box
1: Raised from the depths.
T. Freeth, Y. Bitsakis, X.
Moussas, J. H. Seiradakis, A. Tselikas, H. Mangou, M.
Zafeiropoulou, R. Hadland, D. Bate, A. Ramsey, M. Allen, A.
Crawley, P. Hockley, T. Malzbender, D. Gelb, W. Ambrisco,
and M. G. Edmunds, “Decoding the ancient Greek astronomical
calculator known as the Antikythera Mechanism,” Nature, Vol.
444, Issue No. 7119 (issue dated 2006-11-30), pp. 587-591;
doi:10.1038/nature05357. Also, Figures and Tables,
Supplementary Information, and Box 1: Astronomical cycles
known to the Babylonians.
Antikythera Mechanism Research
J.V. Field and M.T. Wright (both
of The Science Museum, London, SW7 2DD, England), “Gears
from the Byzantines: A portable sundial with calendrical
gearing,” Annals of Science, Taylor & Francis, Vol. 42,
Issue No. 2, issue dated 1985 March (1985-03), pp. 87-138;
Francis Maddison (Curator of the
Museum of History and Science, Oxford OX1 3AZ, UK), “Early
mathematical wheelwork: Byzantine calendrical gearing,”
Nature, Vol. 314, Issue No. 6009 (issue dated 1985-03-28),
pp. 316-317; doi: 10.1038/314316b0.
François Charette, “High tech
from Ancient Greece,” Nature, Vol. 444, Issue No. 7119
(issue dated 2006-11-30), pp. 551-552; doi:10.1038/444551a.
H. Beam Piper, “Omnilingual,”
Astounding Science Fiction (subsequently Analog), February
1957 (1957-02) issue.