A mechanical computer that existed two-thousand
years before the age of electronics. Who built it?
One day a Greek archaeologist named Spyridon Stais
was carefully going through some of the material brought up from
a shipwreck. The wreck had been found accidentally two years earlier
in 1900 when a group of sponge divers had been blown off course
and forced to anchor at a new location near the island of Crete
at a place called Antikythera. There the sponge divers started
conducting business as usual. Instead of finding sponges, however,
they started bringing up bits of pottery and other very old artifacts.
Amazingly, what the divers had happened upon was a Roman ship
that floundered at sea an estimated 2000 years earlier.
The Greek government, anxious to recover what they
could from the wreck, had employed the divers to take on the difficult
job of bringing up artifacts from the bottom of the sea using
the same methods they used to search for sponges: free dives with
no breathing apparatus. It was a dangerous business. One diver
died and another was permanently disabled. Still, the group managed
to retrieve a treasure trove of historical objects.
One of the less impressive finds was the lump of
material that Stais was looking at. It appeared to be a mass of
wood which was now decaying since it had been brought to the surface
and started drying out. The rot seemed to have exposed something
that Stais hadn't seen before: a bit of metal. Not just a bit
of metal, a bit of metal that was round with teeth. A gear. Stais
couldn't believe his eyes. A metal gear from a shipwreck before
the birth of Christ? What was this thing?
What Stais had stumbled upon was the remains of
one of the world's oldest-geared devices - an analog computer
- almost two millennia in age. Over the next century it would
upset the archeological world's understanding about the kind of
technology the ancients were capable of producing.
After Stais's discovery, speculation about what
the device was used for echoed around the archeological world
for decades. Scientists knew that the device seemed to have 32
interlocking gears and a hand crank, plus a display that showed
information about the moon, sun and planets against a background
of stars. The gears inside the mechanism were made of bronze and
the whole device had apparently been mounted in a wooden box that
measured about 13 inches high, 7 inches wide and 3 ½ inches deep.
Unfortunately, much of the device however had been damaged by
its time in the water, making it difficult to work out exactly
how all the parts had been put together.
Efforts to figure out what the thing actually did
received a boost in 1971 when the mechanism was X-rayed. This
enabled scientists to count the teeth on each gear and then make
detailed drawings to determine how it might have worked. In 1974,
Derek de Solla Price, a historian at Yale University, who had
been studying the mechanism for over twenty years, published a
paper showing how he thought the mechanism operated. Price wrote
that the existence of the device "requires us to completely rethink
our attitudes toward ancient Greek technology." Price also built
a reproduction of the device now housed at the National Museum
Much of Price's work, however, was met with skepticism
from other historians who advanced alternate, less-controversial
theories. The existence of a device like the Antikythera Mechanism
from this early a period in history simply did not match many
historians' preconceived notions about the kind of technical expertise
the ancients had. One skeptic, in a desperate attempt to explain
how such a sophisticated object was found in the remains of a
Roman ship, suggested that it was actually a device from the 18th
century that had fallen overboard at some later date and onto
the deck of the wreck.
reproduction of the Mechanism (National
archaeological museum, Athens/Wikipedia Commons)
Recent efforts to find out more about the device
have been spearheaded by the Antikythera Mechanism Research Project,
a consortium of several agencies, businesses and museums interested
in finding out more about the object. The device was too fragile
to be removed from its home at the National Archaeological Museum
of Athens, so the Project constructed a 12-ton portable micro
focus computerized tomographer that used high resolution X-rays
to probe the object and create a 3-dimensional image. Two Hewlett-Packard
scientists, also involved in the project, used a technique they
developed involving a digital camera and fifty different lights
to photograph details of the object that could not previously
be seen. In 2006, the Project announced that with these tools
almost 95 percent of the text engraved on the various parts of
the device is now readable, giving scientists a much-improved
understanding of its capabilities.
Much of what Price and other researchers surmised
about the device seems to be true. The mechanism was clearly an
analog computer designed to allow the operator to predict the
future or past positions of the sun, moon, and probably some of
the planets. On the front of the device were two dials marked
with the zodiac and a solar calendar, with pointers for the Sun
and Moon plus a display showing the phase of the moon. On the
rear of the object was displayed information about the Saros cycle
(a period of around 18 years used in eclipse prediction) and the
Callippic cycle (a period of about 76 years) using two ingeniously
designed spiral dials.
The capability of the machine has amazed scientists.
It has an accuracy of one unit of error out of 860000. One researcher,
Professor Mike Edmonds remarked, "This device is just extraordinary,
the only thing of its kind. The design is beautiful, the astronomy
is exactly right. The way the mechanics are designed just makes
your jaw drop. Whoever has done this has done it extremely carefully."
Who built this ingenious device? Some have gone
so far as to suggest it was the work of aliens. There is no real
evidence for this, of course, and historical texts do have references
to devices similar in design to the Antikythera Mechanism. The
Roman historian Cicero wrote about a device supposedly constructed
by the Greek philosopher Archimedes which was brought back to
Rome by the Roman general Marcus Claudius Marcellus after he conqured
Syracuse in 212 BC. According to Cicero, he received a demonstration
of the device from a descendant of Marcellus and the object displayed
the motions of the sun, moon and five planets. Cecero also mentions
that a similar device was built by his friend Posidonius, another
A millenium later the Persian scholar al-Biruni
also described a device similar to the Antikythera Mechanism and
included a diagram of it in a treatise written in AD 996. Though
it was much simpler in design, historians have speculated that
the object in the diagram was a direct descendant of the Antikythea
Price had a theory that the Antikythera Mechanism
was constructed by the Greek astronomer Geminus on the Greek island
of Rhodes around 87 BC. At the time the island was a center of
learning for astronomy and mechanical engineering. Engineers there
were well-known for creating intricate automata (mechanical toys
or tools that demonstrated basic scientific principles). The device
could have found its way on board a Roman ship a decade later
as part of a hoard of treasure being taken to Rome to be displayed
in a triumphal parade for Julius Caesar.
was it used?
This remains a matter of great speculation. Such
a device would have been of great help to an astrologer in creating
star charts. It could have also been used to correct calendars
and set the dates of religious festivals. It might even have provided
assistance in predicting what days eclipses were likely to occur.
We may never know exactly who built it or what it
was used for. However, it remains a testament to the engineering
skills of the ancients and a warning that despite all we know
about history, there are still mysteries to be solved.
A Partial Bibliography
Archaeology: High tech from Ancient Greece, by François
Charette, Nature, November 2006, http://www.nature.com/nature/journal/v444/n7119/full/444551a.html
Greatest Treasures, by Michael Bradley, Barnes & Noble,
Copyright Lee Krystek
2007. All Rights Reserved.