Ancient Computer (fwd)

Now where do I plug in a gecko? :-)

----------------------- begin forwarded message from House, David Alan -----------------------

From: "House, David Alan" <housed@...>
Subject: Ancient Computer
Date: Thu, 13 Dec 2001 16:52:28 -0500


This one is a bit long, 3, 1/2 pages. I've not finished reading it, and
cannot just now, but I find it sufficiently interesting to pass along for
that which I have seen so far. Enjoy!

David House

Subject: Ancient Greek Computing Device

An Ancient Greek Computer

In 1901 divers working off the isle of Antikythera found the remains of a
clocklike mechanism 2,000 years old. The mechanism now appears to have been
a device for calculating the motions of stars and planets.

by Derek J. de Solla Price

From June 1959 Scientific American p.60

Among the treasures of the Greek National Archaeological Museum in Athens
are the remains of the most complex scientific object that has been
preserved from antiquity. Corroded and crumbling from 2,000 years under the
sea, its dials, gear wheels and inscribed plates present the historian with
a tantalizing problem. Because of them we may have to revise many of our
estimates of Greek science. By studying them we may find vital clues to the
true origins of that high scientific technology which hitherto has seemed
peculiar to our modern civilization, setting it apart from all cultures of
the past. From the evidence of the fragments one can get a good idea of the
appearance of the original object. Consisting of a box with dials on the
outside and a very complex assembly of gear wheels mounted within, it must
have resembled a well- made 18ih-century clock. Doors hinged to the box
served to protect the dials, and on all available surfaces of box, doors and
dials there were long Greek inscriptions describing the operation and
construction of the instrument. At least 20 gear wheels of the mechanism
have been preserved, including a very sophisticated assembly of gears that
were mounted eccentrically on a turntable and probably functioned as a sort
of epicyclic or differential, gear-system.

Nothing like this instrument is preserved elsewhere. Nothing
comparable to it is known from any ancient scientific text or literary
allusion. On the contrary, from all that we know of science and technology
in the Hellenistic Age we should have felt that such a device could not
exist. Some historians have suggested that the Greeks were not interested in
experiment because of a contempt-perhaps induced by the existence of the
institution of slavery-for manual labor. On the other hand it has long been
recognized that in abstract mathematics and in mathematical astronomy they
were no beginners but rather "fellows of another college" who reached great
heights of sophistication. Many of the Greek scientific devices known to us
from written descriptions show much mathematical ingenuity, but in all cases
the purely mechanical part of the design seems relatively crude. Gearing was
clearly known to the Greeks, but it was used only in relatively simple
applications. They employed pairs of gears to change angular speed or
mechanical advantage, or to apply power through a right angle, as in the
water-driven mill.

Even the most complex mechanical devices described by the ancient
writers Hero of Alexandria and Vitruvius contained only simple gearing. For
example, the taximeter used by the Greeks to measure the distance traveled
by the wheels of a carriage employed only pairs of gears (or gears and
worms) to achieve the necessary ratio of movement. It could be argued that
if the Greeks knew the principle of gearing, they should have had no
difficulty in constructing mechanisms as complex as epicyclic gears. We now
know from the fragments in the National Museum that the Greeks did make such
mechanisms, but the knowledge is so unexpected that some scholars at first
thought that the fragments must belong to some more modern device. Can we in
fact be sure that the device is ancient? If we can, what was its purpose?
What can it tell us of the ancient world and of the evolution of modern
science? To authenticate the dating of the fragments. We must tell the story
of their discovery, which involves the first (though inadvertent) adventure
in underwater archaeology. Just before Easter in 1900
a party of Dodecanese sponge-divers were driven by storm to anchor near the
tiny southern Greek island of Antikythera (the accent is on the "kyth,"
pronounced to rhyme with pith). There, at a depth of some 200 feet, they
found the wreck of an ancient ship. With the help of Greek archaeologists
the wreck was explored; several fine bronze and marble statues and other
objects were recovered. The finds created great excitement, but the
difficulties of diving without heavy equipment were immense, and in
September, 1901, the "dig' was abandoned. Eight months later Valerios
StaCEs, an archaeologist at the National Museum, was examining some
calcified lumps of corroded bronze that had been set aside as possible
pieces of broken statuary. Suddenly he recognized among them the fragments
of a mechanism.

It is now accepted that the wreck occurred during the first century
B.C. Gladys Weinberg of Athens has been kind enough to report to me the
results of several recent archaeological examinations of the amphorae,
pottery and minor objects from the ship. It appears from her report that one
might reason-ably date the wreck more closely as 65 B.C. 115 years.
Furthermore, since the identifiable objects come from Rhodes and Cos, it
seems that the ship may have been voyaging from these islands to Rome,
perhaps without calling at the Greek mainland.

The fragment that first caught the eye of StaCEs was one of the
corroded, inscribed plates that is an integral part of the Antikythera
mechanism, as the device later came to be called. StaCEs saw immediately
that the inscription was ancient. In the opinion of the epigrapher Benjamin
Dean Meritt, the forms of the letters are those of the 'first century B.C.;
they could hardly be older than 100 B.C. nor younger than the time of
Christ. The dating is supported by the content of the inscriptions. The
words used and their astronomical sense are all of this period. For example,
the most extensive and complete piece of inscription is part of a parapegma
(astronomical calendar) similar to that written by one Geminos, who is
thought to have lived in Rhodes about 77 B.C. We may thus be reasonably sure
that the mechanism did not find its way into the wreck at some later period.
Furthermore, it cannot have been very old when it was taken aboard the ship
as booty or merchandise.

As soon as the fragments had been discovered they were examined by
every available archaeologist; so began the long and difficult process of
identifying the mechanism and determining its function. Some things were
clear from the beginning. The unique importance of the object was obvious,
and the gearing was impressively complex. From the inscriptions and the
dials the mechanism was correctly identified as an astronomical device. The
first conjecture was that it was some kind of navigating instrument -
perhaps an astrolabe (a sort of circular star-finder map also used for
simple observations). Some thought that it might be a small planetarium of
the kind that Archirnedes is said to have made. Unfortunately the fragments
were covered by a thick curtain of calcified material and corrosion
products, and these concealed so much detail that no one could be sure of
his conjectures or reconstructions. There was nothing to do but wait for the
slow and delicate work of the Museum technicians in cleaning away this
curtain. Meantime, as the work proceeded, several scholars published
accounts of all that was visible, and through their labors a general picture
of the mechanism began to emerge.

On the basis of new photographs made for me by the Museum in 1955 I
realized that the work of cleaning had reached a point where it might at
last be possible to take the work of identification to a new level. Last
summer, wilt the assistance of a grant from the American Philosophical
Society, I was able to visit Athens and make a minute examination of the
fragments. By good fortune George Stamires, a Greek epigrapher, was there at
the same time; he was able to give me invaluable help by deciphering and
transcribing much more of the inscriptions than had been read before. We are
now in the position of being able to "join" the fragments and to see how
they fitted together in the original machine and when they were brought up
from the sea [see illustration]. The success of this work has been most
significant, for previously it had been supposed that the various dials and
plates had been badly squashed together and distorted. It now appears that
most of the pieces are very nearly in their original places, and that we
have a much larger fraction of the complete device than had been thought.
This work also provides a clue to the puzzle of why the fragments lay
unrecognized until StaCEs saw them. When they were found, the fragments were
probably held together in their original positions by the remains of the
wooden frame of the case. In the Museum the waterlogged wood dried and
shriveled. The fragments then fell apart, revealing the interior of the
mechanism, with its gears and inscribed plates. As a result of the new
examinations we shall in due course be able to publish a technical account
of the fragments and of the construction of the instrument. In the meantime
we can tentatively summarize some of these results and show how they help to
answer the question. What is it? There are four ways of getting at the
answer First, if we knew the details of the mechanism, we should know what
it did. Second, if we could read the dials, we could tell what they showed.
Third, if we could understand the inscriptions, they might tell us about the
mechanism. Fourth, if we knew of any similar mechanism, analogies might be
helpful. All these approaches must be used, for none of them is complete.

The geared wheels within the mechanism were mounted on a bronze plate. On
one side of the plate we can trace all the gear wheels of the assembly and
can determine, at least approximately, how many teeth each had and how they
meshed together. On the other side we can do nearly as well, but we still
lack vital links that would provide a complete picture of the gearing. The
general pattern of the mechanism is nonetheless quite clear. An input was
provided by an axle that came through the side of the casing and turned a
crown-gear wheel. This moved a big, four-spoked driving-wheel that was
connected with two trains of gears that respectively led up and down the
plate and were connected by axles to gears on the other side of the plate.
On that side the gear-trains continued, leading through an epicyclic
turntable and coming eventually to a set of shafts that turned the dial
pointers. When the input axle was turned, the pointers all moved at various
speeds around their dials.

Certain structural features of the mechanism deserve special attention.
All the metal parts of the machine seem to have been cut from a single sheet
of low-tin bronze about two millimeters thick; no parts were cast or made of
another metal. There are indications that the maker may have used a sheet
made much earlier-uniform metal plate of good quality was probably rare and
expensive. All the gear wheels have been made with teeth of just the same
angle (60 degrees) and size, so that any wheel could mesh with any other.
There are signs that the machine was repaired at least twice; a spoke of the
driving wheel has been (mended?), and a broken tooth in a small wheel has
been replaced. This indicates that the machine actually worked.

The casing was provided with three dials, one at the front and two at the
back. The fragments of all of them are still covered with pieces of the
doors of the casing and with other debris. Very little can be read on the
dials, but there is hope that they can be cleaned sufficiently to provide
information that might be decisive. The front dial is just clean enough to
say exactly what it did. It has two scales, one of which is fixed and
displays the names of the signs of the zodiac; the other is on a movable
slip ring and shows the months of the year. Both scales are carefully marked
off in degrees. The front dial fitted exactly over the main driving-wheel,
which seems to have turned the pointer by means of an eccentric
drum-assembly. Clearly this dial showed the annual motion of the sun in the
zodiac. By means of key letters inscribed on the zodiac scale, corresponding
to other letters on the parapegma calendar plate, it also showed the main
risings and settings of bright stars and constellations throughout the year.

The back dials are more complex and less legible. The lower one had three
slip rings; the upper, four. Each had a little subsidiary dial resembling
the "seconds" dial of a watch. Each of the large dials is inscribed with
lines about every six degrees, and between the lines there are letters and
numbers. On the lower dial the letters and numbers seem to record "moon, so
many hours; sun, so many hours"; we therefore suggest that this scale
indicates the main lunar phenomena of phases and times of rising and
setting. On the upper dial the inscriptions are much more crowded and might
well present information on the risings and settings, stations and
retrogradations of the planets known to the Greeks, Mercury, Venus, Mars,
Jupiter and Saturn).

Some of the technical details of the dials are especially interesting.
The front dial provides the only known extensive specimen from antiquity of
a scientifically graduated instrument. When we measure the accuracy of the
graduations under the microscope, we find that their average error over the
visible 45 degrees is about a quarter of a degree. The way in which the
error varies suggests that the arc was first geometrically divided and then
subdivided by eye only. Even more important, this dial may give a means of
dating the instrument astronomically. The slip ring is necessary because the
old Egyptian calendar, having no leap years, fell into error by 1/4 day
every year; the month scale thus had to be adjusted by this amount. As they
are preserved the two scales of the dial are out of phase by 13 degrees.
Standard tables show that this amount could only occur in the year 80 B.C.
and (because we do not know the month) at all years just 120 years (i.e.,
30 days divided by 1/4 day per year) before or after that date. Alternative
dates are archaeologically unlikely: 200 B.C. is too early; 40 A.D. is too
late. Hence, if the slip ring has not moved from its last position, it was
set in. 80 B.C. Furthermore, if we are right in supposing that a fiducial
mark near the month scale was put there originally to provide a means of
setting that scale in case of accidental movement, we can tell more. This
mark is exactly 1/2 degree away from the present position of the scale, and
this implies that the mark was made two years before the setting. Thus,
although the evidence is by no means conclusive, we are led to suggest that
the instrument was made about 82 B.C., used for two years (just long enough
for the repairs to have been needed) and then taken onto the ship within the
next 30 years.

The fragments show that the original instrument carried at least four
large areas of inscription: outside the front door, inside the back door, on
the plate between the two back dials and on the parapegma plates near the
front dial. As I have noted, there are also inscriptions around all the
dials, and furthermore each part and hole would seem to have had identifying
letters so that the pieces could be put together in the correct order and
position. The main inscriptions are in a sorry state and only short snatches
of them can be read. To provide an idea of their condition it need only be
said that in some cases a plate has completely disappeared, leaving behind
an impression of its letters, standing up in a mirror image, in relief on
the soft corrosion products on the plate below. It is remarkable that such
inscriptions can be read at all.

But even from the evidence of a few complete words one can get an idea of
the subject matter. The sun is mentioned several times, and the planet Venus
once; terms are used that refer to the stations and retrogradations of
planets; the ecliptic is named. Pointers, apparently those of the dials, are
mentioned. A line of one inscription significantly records "76 years, 19
years." This refers to the well-known Calippic cycle of 76 years, which is
four times the Metonic cycle of 19 years, or 235 synodic (lunar) months. The
next line includes the number "223," which refers to the eclipse cycle of
223 lunar months.

Putting together the information gathered so far, it seems reasonable to
suppose that the whole purpose of the Antikythera device was to mechanize
just this sort of cyclical relation, which was a strong feature of ancient
astronomy. Using the cycles that have been mentioned, one could easily
design gearing that would operate from one dial having a wheel that revolved
annually, and turn by this gearing a series of other wheels which would move
pointers indicating the sidereal, synodic and draconitic months. Similar
cycles were known for the planetary phenomena; in fact, this type of
arithmetical theory is the central theme of Seleucid Babylonian astronomy,
which was transmitted to the Hellenistic world in the last few centuries
B.C. Such arithmetical schemes are quite distinct from the geometrical
theory of circles and epicycles in astronomy, which seems to have been
essentially Greek. The two types of theory were unified and brought to their
peak in the second century A.D. by Claudius Ptolemy, whose labors marked the
triumph of the new mathematical attitude toward geometrical models that
still characterizes physics today.

The Antikythera mechanism must therefore be an arithmetical counterpart
of the much more familiar geometrical models of the solar system which were
known to Plato and Archimedes and evolved into the orrery and the
(planetarium) The mechanism is like a great astronomical clock without an
escapement, or like a modern analogue computer which uses mechanical parts
to save tedious calculation. It is a pity that we have no way of knowing
whether the device was turned automatically or by hand. It might have been
held in the hand and turned by a wheel at the side so that it would operate
as a computer, possibly for astrological use. I feel it is more likely that
it was permanently mounted, perhaps set in a statue, and displayed as an
exhibition piece. In that case it might well have been turned by the power
from a water clock or some other device. Perhaps it is just such a wondrous
device that was mounted inside the famous Tower of Winds in Athens. It is
certainly very similar to the great astronomical cathedral clocks that were
built all over Europe during the Renaissance.

It is to the prehistory of the mechanical I clock that we must look for
important analogies the Antikythera mechanism and for an assessment of its
significance. Unlike other mechanical devices, the clock did not evolve from
the simple to the complex. The oldest clocks of which we are well informed
were the most complicated. All the evidence points to the fact that the
clock started as an astronomical showpiece that happened also to indicate
the time. Gradually the timekeeping functions became more important and the
device that showed the marvelous clockwork of the heavens became subsidiary.
Behind the astronomical clocks of the 14th century there stretches an
unbroken sequence of mechanical models of astronomical theory. At the head
of this sequence is the Antikythera mechanism. Following it are instruments
and clocklike computers known from Islam, from China and India and from the
European Middle Ages. The importance of this line is very great, because it
was the tradition of clock- making that preserved most of man's skill in
scientific fine mechanics. During the Renaissance the scientific
instrument-makers evolved from the clockmakers. Thus the Antikythera
mechanism is, in a way, the venerable progenitor of all our present plethora
of scientific hardware.

A significant passage in this story has to do with the astronomical
computers of Islam. Preserved complete at the Museum of History of Science
at Oxford is a 13th-century Islamic geared calendar-computer that has
various periods built into it, so that it shows on dials the various cycles
of the sun and moon. This design can be traced back, with slightly different
periods but a similar arrangement of gears, to a manuscript written by the
astronomer al-Biruni about 1000 A.D. Such instruments (are) much simpler
than the Antikythera mechanism, but they show so many points of agreement in
technical detail that it seems clear they came from a common tradition. The
same 60-degree gear teeth are used; wheels are mounted on square-shanked
axles; the geometrical layout of the gear assembly appears comparable. It
was just at this time that Islam was drawing on Greek knowledge and
rediscovering ancient Greek texts. It seems likely that the Antikythera
tradition was part of a large corpus of knowledge that has since been lost
to us but was known to the Arabs. It was developed and transmitted by them
to medieval Europe, where it became the foundation for the whole range of
subsequent invention in the field of clockwork.

On the one hand the Islamic devices knit the whole story together, and
demonstrate that it is through ancestry and not mere coincidence that the
Antikythera mechanism resembles a modern clock. On the other hand they show
that the Antikythera mechanism was no flash in the pan but was a part of an
important current in Hellenistic civilization. History has contrived to keep
that current dark to us, and only the accidental underwater preservation of
fragments that would otherwise have crumbled to dust has now brought it to
light. It is a bit frightening to know that just before the fall of their
great civilization the ancient Greeks had come so close to our age, not only
in their thought, but also in their scientific technology.

----------------------- end forwarded message from House, David Alan -----------------------

--
----------------------------------------------------------------------------
RKBA! ***** Blessings On Thee, Oh Israel! ***** 4-19!
----------------+----------+--------------------------+---------------------
An _EFFECTIVE_ | Insured | All matter is vibration. | Let he who hath no
weapon in every | by COLT; | -- Max Plank | weapon sell his
hand = Freedom | DIAL | In the beginning was the | garment and buy a
on every side! | 1911-A1. | word. -- The Bible | sword.--Jesus Christ
----------------+----------+--------------------------+---------------------

Constitutional Government is dead, LONG LIVE THE CONSTITUTION!!!!!

----------------------------------------------------------------------------