Essays Relating To The History Of 

Occidental Constellations and 

Star Names to the Classical Period 

The Myth of Babylonian Knowledge of Precession by Gary D. Thompson 

Copyright © 2004-2012 by Gary D. Thompson 

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The Myth of Babylonian Knowledge of Precession 

A central claim of the Panbabylonists (a group of German Cuneiform
Philologists and Assyriologists at the beginning of the 20th-century) was
that the Babylonians had discovered precession. The various forms of proof
included arguments involving: believed early Babylonian ability for
accurate observations and involved calculations, calendrical systems,
believed early zodiacal scheme, solstice-equinox-Sirius texts, the
Astronomical Diaries, zero points in System A and System B, and legends
and symbols. The hypothesis that the Babylonians knew precession can be
confidently dismissed. The hypothesis has been adequately refuted by the
studies of the astronomer and Assyriologist Franz Kugler, the
mathematician Otto Neugebauer, and the Assyriologist Abraham Sachs.

Franz Kugler was a pioneer of the study of mathematical-astronomical
cuneiform texts and also calendrical texts. His refutation of the
Panbabylonist arguments for Babylonian knowledge of precession is
contained in his Sternkunde und Sterndienst in Babel (1907-1924). The
ideas that a 12-constellation equally divided Babylonian zodiac originated
circa 6000 BCE (promoted by the Panbabylonists Fritz Hommel and Alfred
Jeremias) did not begin to be entirely discarded until the monumental
multi-volume Sternkunde und Sterndienst in Babel by Franz Kugler began
publication in 1907. Franz Kugler, in his numerous clashes with the
Panbabylonists Fritz Hommel, Alfred Jeremias, and Ernst Weidner,
convincingly demonstrated that the Babylonians had a late and sidereal
zodiac and a late mathematical astronomy. This meant that precession could
not have been marked at an early date through either the constellations or
signs of the zodiac. Also, from his study of cuneiform texts Kugler
pointed out that the concept of precessional movement of the tropical
points through ecliptic constellations was not contained in early
Babylonian astronomical texts. There is nothing in the Babylonian texts to
prove a Twins-, Bull-, and Ram-period of precession. The ecliptic only
became important in the 1st millennium BCE. There was certainly no
pre-first millennium zodiac for observing and measuring precessional
"zodiacal ages." A zodiac for being able to do such only came into
existence in the last half of the 1st millennium BCE.

In addition to the above Otto Negebauer pointed out ("Babylonian Planetary
Theory.", Proceedings of the American Philosophical Society, Volume 98,
1954, Page 64): "There is no trace of any definition of the vernal point
as the intersection of ecliptic and equator (which appears nowhere in
Babylonian astronomy)."

The Ram was an important cult figure in both ancient Egyptian and
Babylonian civilizations - but not a constellation. The Ram is a Greek
constellation. When the Greeks borrowed the zodiacal system from
Babylonian uranography the Babylonian constellation of the "Hired Man" was
replaced by the Ram. (For a philological explanation of how this may have
occurred see "Zodiacal Signs among the Seal Impressions from Hellenistic
Uruk." by Ronald Wallenfels in: The Tablet and the Scroll edited by Mark
Cohen et. al., 1993, Pages 282-283.)

Unfortunately the myth of a prehistoric 12-constellation zodiac (of equal
divisions) is not yet dead. The importance of the ecliptic and the
development of the 12-constellation zodiac does not appear anywhere until
its origin in Babylonia circa 700 BCE.. The development of the equally
divided 12-constellation zodiac does not appear until after the start of
the Persian Period in Babylonia (circa 500 BCE). The cuneiform tablet
evidence clearly establishes that it was the astronomy of the Mul.Apin
scheme (circa 1000 BCE) that established the preconditions for the
importance of the ecliptic and the establishment of the Babylonian
zodiacal scheme which was later adopted by the Greeks. The Babylonian
scheme of 12 zodiacal constellations was derived from a system of 18
constellations (established during the Assyrian Period beginning circa
1100 BCE)  along the ecliptic to mark the path of the Moon. (Prior to
circa 1000 BCE the ecliptic was not specifically marked in Babylonian
astronomy. The three path system of the "three stars each" was established
and in effect was an equatorial system. However, the Babylonians clearly
had no concept of a celestial equator.)  Circa 700 BCE (toward the
Neo-Babylonian Period) the scheme of 18 constellations used to mark the
path of the moon were then reduced to a scheme of 12 (unequal)  
constellations along the ecliptic to suit a schematic year of 12 months of
30 days each. This scheme was finally achieved with the division of the
zodiac into 12 equal divisions (during the Neo-Babylonian period). (The
constellations not wholly occupying the ecliptic were removed.) The scheme
of 12 constellations (and 12 zodiacal divisions of equal length) was the
last scheme of constellations (and divisions) to be finalised (and is not
older than the 5th-century BCE). However, the individual constellations
included in the zodiacal scheme have far earlier origins and some can be
dated back 1500 years to the Old Babylonian Period. The evidence is
conclusive that a system of 12 equal zodiacal divisions did not exist
until circa 450 BCE. This date is the earliest from which there was a
possible basis for the determination of precessional "zodiacal ages."
However, precession remained undiscovered until the work of the Greek
astronomer Hipparchus circa 120 BCE. Exactly how Hipparchus understood
precession and why it occurs is unclear. Hipparchus calculated a rate for
precession rather than identifying what was happening and why.

Hipparchus had the benefit of the concept of the ecliptic and 12 zodiacal
constellations, a solid concept of the equinoxes and solstices, plus a
geometrical model of the earth in space, to work with. Importantly, he
also had the positions (i.e., declinations) of some 25 stars near the
ecliptic (established the previous century by the Greek astronomers
Timocharis and Aristyllos). There is no evidence to establish that anybody
earlier than the Greeks circa 500 BCE had the same collection of concepts.
If the Babylonians (or some other cultural group) were aware of precession
prior to 1000 BCE then they did not have the combined benefit of the
concept of the ecliptic, an equally-divided 12-constellation zodiac, a
geometrical perspective of the heavenly bodies, and the abstract moving
points of the equinoxes and solstices. Thus if an early group became aware
of precession they can not be expected to have explained it in the same
way Hipparchus did. The Greek philosopher and polymath Aristotle (384-322
BCE)  had never heard of precession. Using John Dreyer's History of the
Planetary Systems from Thales to Kepler (1906) we find that in the
Greek-Roman world precession was only mentioned by Hipparchus of Rhodes
(circa 190-circa 120 BCE, Greek astronomer and mathematician), Claudius
Ptolemy (Greek-Roman citizen and astronomer and mathematician, circa
100-circa 165 CE), Proclus Lycaeus (412-485 CE, a Greek Neoplatonic
philosopher) who emphatically denied its existence, Theon of Alexandria
(circa 335-405 CE, Greek mathematician and astronomer), and Origen
Adamantius (184/185-253/254 CE, early Christian Alexandrian scholar and
theologian). It is one thing to claim - as some writers do - precession
was known by circa 200 CE and another to provide reasonable proof of the
claim. On similar lack of evidence it can be claimed that precession was
denied by the early fathers of the Church. Precession was not mentioned by
Geminus of Rhodes (Greek astronomer and mathematician, flourished
1st-century BCE), Cleomedes (flourished 1st-century CE, Greek (Stoic)
philosopher and astronomer), Theon of Smyrna (circa 70-circa 135 CE, Greek
philosopher and mathematician), Marcus Manilius (flourished 1st-century
CE, Roman poet, astrologer, and author of a poem in five books called
Astronomica), Pliny the Elder ((Gaius Plinius Secundus), 23-79 CE, Roman
author, naturalist, and natural philosopher), Censorinus (flourished
3rd-century CE, Roman grammarian and miscellaneous writer), Achilles
Tatius (flourished 3rd-century CE, Greek writer (referred to by Firmicus
Maternus)), Chalcidius ((Calcidius)  flourished 4th-century, Greek
philosopher (possibly a Christian), Ambrosius Macrobius (flourished early
5th-century CE, Roman scholar), and Martianius Capella (circa 365-circa
440 CE, Roman school teacher at Carthage).

The dissemination of knowledge in the ancient world (including the
Hellenistic period) was neither fast nor efficient. Many astronomers well
into the early medieval period either did not know of - or did not accept
- precession. Some simply believed in trepidation. The theory of
trepidation is oscillation in the precession of the equinoxes. The origin
of the idea of trepidation comes from the Small Commentary to the Handy
Tables written by Theon of Alexandria in the 4th-century CE. The theory
was popular in European and Arab-Islamic astronomy from the 9th to the
16th centuries. The most widely used theory of trepidation during the
Middle Ages was that of the 9th-century Arab-Islamic astronomer, Thabit
ibn Qurra. Thabit ibn Qurra is generally credited with first postulating
the theory of the progressive and regressive (oscillating) motion of the
stars, also known as access and recess. Isaac Newton (1642-1727)
understood the nature of precession and had accurately calculated its
annual rate. He is credited with the first full theoretical explanation of
the precession of the equinoxes. It is obvious that discovering precession
is not as easy as having a grandfather who has a tree and passes down
stories about his lifetime observation of the night sky.

When the zodiacal system was first being devised (over the period circa
700 BCE to 500 BCE) it is evident that precession had not been discovered.
The Babylonian astronomers who first originated the zodiac did not attempt
to measure the zodiac from an invisible tropical point they were unable to
observe (and could only approximate). It was easiest for them to observe
the fixed stars and the zodiac was tied to the fixed stars. The Babylonian
astronomers simply defined the starting points of the zodiacal signs by
their positions relative to the fixed stars. The Babylonians simply placed
the tropical points in the middle of the relevant signs (i.e., 15 degrees
Aries per Mul.Apin) or related them to fixed stars (i.e., put the vernal
point at 10 degrees Aries per System A, or 8 degrees Aries per System B).
(It appears it was the Greek astronomer Hipparchus who was the first to
identify the "first point of Aries" with the vernal point.)  It would
appear that the Babylonians had no suitable understanding of the tropical
points, at least for most of their history. Up til the 7th-century BCE
most administrative and astronomical texts show an almost exclusive use of
a schematic calendar comprised of twelve 30-day months. Its use is
evidenced in administrative texts from Uruk III at the end of the 4th
millennium BCE and from Jemdet Nasr throughout the 3rd millennium BCE. In
astronomical texts its use is evidenced in BM 17175 (from the Old
Babylonian Period); the series Mul.Apin (from the Assyrian Period); Tablet
14 of the omen series Enuma Anu Enlil (circa the Cassite Period); the
series I.NAM.GIS.HUR.AN.KI.A (from the Middle Babylonian Period); and also
in the various "Three Stars Each" star calendar texts (which date from the
Middle Babylonian Period. In all these astronomical texts the solstices
and the equinoxes are equidistantly spaced at the midpoints (i,e, day 15)
of certain months - usually months 3 (summer solstice), 6 (autumn
equinox), 9 (winter solstice), and 12 (spring equinox). (In the series
Mul.Apin (and also in BE 13918 and the "Ivory Prism," both from the
Neo-Assyrian Period) there is a change in calendar practices and the dates
of the solstices and equinoxes are shifted by one month.) The basic method
of the Babylonians for determining the tropical points was simply to
observe the summer solstice and then the position of the other solstice
and the equinoxes were found by adding approximately 3, 6, or 9 months.
(For a discussion of the methods used to determine the solstices and
equinoxes see: Astral Sciences in Mesopotamia by Hermann Hunger and David
Pingree (1999; Pages 75-77).)

Kugler also pointed out that the lack of accurate calculation and
observation in early records of eclipses and of the planets demonstrates
the absence of a precise system of measuring location and time in the sky.
Precise date and position details are not given for any early
observations. The total eclipse observed in 763 BCE was only recorded by
the simple statement: "In the month Sivan an eclipse of the Sun took
place."

Until the (Late) Assyrian Period Mesopotamian astronomy is simply
qualitative.  Astronomical observations the early period of Mesopotamian
astronomy show little exactness. The Venus observations made during the
reign of Ammizaduqa were made in order to provide empirical material for
omina. It is only from the (Late)  Assyrian Period that the mathematical
treatment of astronomy begins. Also, it is only from this period that
systematic observational reports begin to appear.

Importantly, the development of latitude and longitude as astronomical
coordinates did not occur before circa 200 BCE. (It was only during the
Seleucid Period (beginning circa 200 BCE) that techniques were developed
for determining the positions of celestial bodies in terms of degrees of
latitude and longitude.)  The inaccurate nature of the calendar for
approximately 2000 years is inconsistent with an ability for careful and
systematic observations. Before the 7th-century BCE almost all
astronomical texts used the schematic calendar of twelve 30-day months.
The absence of an accurate calendar also makes it difficult to easily
discover precessional change. (See: Sternkunde und Sterndienst in Babels,
Buch 2, Teil 1,1909/10, Pages 20-31; and Buch 2, Teil 2, Heft 2, 1924.)
The lack of an accurate calendrical system and the lack of exactitude in
early Babylonian astronomy makes it implausible to believe that a
continuous series of precise observations, and accompanying accumulation
of continually maintained records, was possible. Changes in the position
of the sun relative to the tropical points is a fraction of a degree per
year and difficult to observe simply because when the sun is visible the
fixed stars are not. The return of the Sun to the equinox point could not
be timed with accuracy by the Babylonians. This means it would be
difficult to make the distinction between the sidereal year and the
tropical year. The Babylonian astronomical and calendrical texts do not
distinguish a sidereal year and a tropical year.

In his 1914 paper "Die Entdeckung der Präzession, eine Geistestat
babylonischer Astronomen." (Babyloniaca, Tome 7, Pages 1-19) Ernst Weidner
attempted to prove that the Babylonians knew of precession at least by
circa 1500 BCE. His argument was that the dates of the solstices and
equinoxes in a tablet (CBS 11901) which he dated to circa 1500 BCE were
approximately correct as were the dates of the solstices and equinoxes in
tablets dating from circa the 6th-century BCE.  However, Kugler
(Sternkunde und Sterndienst in Babels, Erganzungen 2 für Buch 1 und Buch
2, Pages 233-242) demonstrated that the cuneiform tablet (CBS 11901 (=
LBAT 1478)) that Weidner dated to circa 1500 BCE was actually to be
correctly dated to 424/3 BCE.

Standardisation of the calendar was necessary for the discovery of
precession.  The lunar calendar scheme was unsuitable for anything but
approximate time timekeeping. The early introduction of the use of the
ideal or schematic year of 360 days still posed problems for accurate time
measurement. (The observation-based Babylonian month had 29 or 30 days. If
the crescent moon was already visible at the beginning of day 30 in a
month, this day 30 was rejected, which meant that the month only had 29
days.) Early Babylonian calendars were rather awful regarding accuracy and
were simply adjusted (intercalated) on an arbitrary basis.  They remained
chaotic through to the late first millennium BCE. For most of their
history the Babylonians had no method of keeping the lunar year and the
solar year together. This precludes the keeping of accurate astronomical
records.  The Assyrian calendar of the second millennium BCE did not use
intercalation at all and drifted all through the solar year. (The early
Babylonians were more interested in having a calendar comprised of uniform
numbers than dealing with the non-uniform numbers resulting from
exactness.) In Babylonia the year began at about the time of the spring
equinox.

In the Astrolabes of the late 2nd millennium BCE the first day of the
first month of the year, the first of Nisan (= March/April), was marked by
the approximate conjunction of the first visible crescent Moon with the
star group Mul.Iku (= The Field). The observation of the heliacal rising
of Mul.Iku on the eastern horizon (just before sunrise) and then the first
appearance of the crescent new Moon at dusk on the western horizon marked
the beginning of the new year. In the Mul.Apin series of the 1st
millennium BCE Mul.Mul (= Pleiades) was the star group that functioned to
mark the new year (the first of Nisan). In the spring when the Pleiades
rose heliacally on the eastern horizon (just before sunrise) in
conjunction with the first visible crescent Moon on the western horizon
(at dusk) it marked the first day of the month Nisan (and the beginning of
the new year). However, as the sequence of years of 12 and 13 months was
very irregular sometimes the year began earlier and sometimes it began
later. (The identification of the Babylonian calendar months were aided by
the use of the scheme of the "three stars each" which enabled the
Babylonians to know when the lunar months were shifting out of correlation
with the seasons. The "three stars each" consisted of a month-by-month
listing of constellations, stars, and planets which rose heliacally (on
the eastern horizon) in each of the twelve 30-day months of the schematic
year. For each month a star was assigned to each of the "three ways"
(i.e., the paths of Anu, Enlil, and Ea) and rose at 10 day intervals. At
first they were recorded as a circular pictorial representation and then
later as a listing only.) No cyclically regulated intercalation (to
control the calendar) existed in Babylonian prior to the Persian Period
(circa 450 BCE). When finally introduced the unit of intercalation was
simply the lunation (and was used as needed to keep the calendar year in
line with the seasons). When the grain was ready for harvest was the key
issue in determining intercalation. The time of a star's heliacal rising
changes at the rate of about a month approximately every two thousand
years. The way the Babylonian calendar operated there is no reason to
suppose that the calendar error would become really conspicuous until
after approximately 2000 years. This brings us down to the Late
Hellenistic Period. Also, there is no identified tradition of long-term
seasonal displacement of familiar stars used as markers.

Otto Neugebauer spent a life-time engaged in the study of
mathematical-astronomical cuneiform texts. His decisive demolition of Paul
Schnabel's argument for Babylonian knowledge of precession ("Kidenas,
Hipparch und die Entdeckung der Präzession." (Zeitschrift für Assyriologie
und Verwandte Gebiete, Neue Folge, Band 3 (Band 37), 1927, Pages 1-60)) is
contained in his paper "The Alleged Babylonian Discovery of the Precession
of the Equinoxes." (Journal of the American Oriental Society, Volume 70,
Number 1, 1950, Pages 1-8). In this paper and his earlier book Berossos
und die babylonisch-hellenistische Lieratur (1923, Pages 233-237)
Schnabel.had claimed that the Babylonian astronomer Kidinnu had discovered
precession at (mistakenly, due to an earlier translation error made by
Franz Kugler) Sippar. The date offered in 1923 was 313 BCE but this was
changed in his 1927 paper (in which he offered further arguments to
counter the criticisms made by Franz Kugler in Sternkunde und Sterndienst
in Babel (Buch 2, Teil 2, Heft 2, 1924) Pages 582-621 and Pages 627-630)
to 378 BCE. Paul Schnabel basically proposed that the 4th-century BCE
astrologer/mathematician Kidinnu discovered precession when distinguishing
between sidereal and tropical years.  Schnabel's argument for the
Babylonian discovery of precession was based on a commonly made scribal
numerical error (the interchange of cuneiform 4 and 7).  The other half of
the text used by Schnabel was later located in Chicago and it contained
other scribal errors that more than outbalanced the one that Schnabel had
taken seriously. Also included in Schnabel's main argument for the
Babylonian discovery of precession was was that System B developed from
System A.  This was undermined by (1) evidence for the near contemporary
development of both systems, and (2) their different provinces in Babylon
(for System A) and Uruk (for System B). Also, System A and System B were
used contemporaneously.  Tablets for both systems have been found in both
Babylon and Uruk. Tablets based on System B have been found mostly in
Uruk, but the somewhat earlier System A tablets came predominantly from
Babylon.

In his monumental A History of Ancient Mathematical Astronomy (3 Parts,
1975)  Neugebauer wrote (Part 1, Page 369): "We have no evidence from
Babylonian sources about a recognition of precession and we have no reason
to assume that the difference of zero points in System A and B had
anything to do with it, knowingly or unknowingly. ... That the vernal
point maintained in each of the two systems a fixed sidereal longitude
indicates that precession was unknown."

Also relevant are the solstice-equinox-Sirius texts. (These texts formed
part of the Astronomical Diaries. Hermann Hunger and David Pingree write
(Astral Sciences in Mesopotamia (1999) Page 151): "The only aspects of
solar motion mentioned in the diaries are the dates of the occurrences of
solstices and equinoxes and of the heliacal rising and setting and the
acronychal rising of Sirius.") The phases of Sirius and other fixed stars
were put into a definite relation to the solstice-equinox scheme. (The
term "phases" of a star relates to horizon aspects of apparent movement.
The four important "phases" of a star were heliacal rising (its first
visible rising above the eastern horizon just before sunrise) and heliacal
setting (its last visible setting below the western horizon just after
sunset); and acronychal rising (when it first rises above the eastern
horizon just as the sun sets below the western horizon) and acronychal
setting (when it first sets below the western horizon just as the sun
rises above the eastern horizon). Both the heliacal and acronychal risings
and settings are directly observable phenomena.) These texts contain
information setting out the positions of Sirius and other stars relative
to the solstice and equinox points. The discussion by Neugebauer (A
History of Ancient Mathematical Astronomy, Part 1, Page 543) of these
solstice-equinox-Sirius texts, which date from circa the 6th-century BCE
through to the Seleucid Period, shows that the position of Sirius relative
to the solstices and equinoxes does not change over time with precession
as would be expected had the Babylonians known of such. The earliest
Sirius dates circa 600 BCE are the same as those of the later period. (The
scheme found in BM 36731 lists equinoxes, solstices, and heliacal risings
and settings of Sirius from, it would appear, 615-587 BCE. The
solstice-equinox-Sirius dates are resumed again by the Astronomical
Diaries in 330 BCE.) Neugebauer (A History of Ancient Mathematical
Astronomy, Part 1, Page 543, Note 13) concludes:  "This is, incidentally,
further evidence for the fact that the Babylonian astronomers were not
aware of the existence of precession."

See also the early study by Abraham Sachs on the dates of the phases of
Sirius related to the solstice and equinox schemes: "Sirius Dates in
Babylonian Astronomical Texts of the Seleucid Period." by Abraham Sachs
(Journal of Cuneiform Studies, Volume 6, 1952, Pages 105-114). Simply, the
dates of all solstices and equinoxes found in Seleucid texts are the
result of computation according to a fixed scheme. Observation was not
involved. A succinct summary explanation is given by Hermann Hunger in his
booklet, Astrology and Other Predictions in Mesopotamia (1997, Page 29):
"The dates of the equinoxes and solstices and the appearance of the star
Sirius are all given according to a schematical computation; so these are
not observations." For the Babylonians the arrangement of the solstices
and equinoxes are part of the schematic year - they are simply established
within the time frames of the ideal 360-day year. The Babylonians show no
awareness of actual periodicities and only modest observational
foundations are indicated as forming the basis for their calculated
schemes.

Within the methods and results of Babylonian astronomy very great emphasis
was placed on schematization. The main concern of Babylonian astronomy was
convenience of numerical manipulation and the intent to solve complicated
periodic relationships by the use of successive approximations based on
arithmetical progressions. As such the dates of solstices and equinoxes
were the result of computation according to a fixed scheme. There is no
evidence at all that during the entire Assyrian Period the spring equinox
had any significance for the beginning of the year. The equinoxes and
solstices had no effect on the Mesopotamian calendar.

The idea that the Babylonian knew precession is also refuted by the study
of two tablets from Uruk for the computation of summer solstices. (See:
"Schematische Berechnungen der Sonnenwenden." by Hermann Hunger (Baghdader
Mitteilungen, Volume 22, 1991, Pages 513-519).)

Abraham Sachs spent the latter part of his career in a detailed study of
the Astronomical Diaries. (His work has been continued by the
Assyriologist Hermann Hunger.) His detailed studies of these and related
texts has established that this uninterrupted 800 year long observational
program did not lead to Babylonian knowledge of precession. (See further:
Annals of Science, Volume 58, Number 3, July 1, 2001, Pages 323-326.) The
data in the Astronomical Diaries and the Almanacs is frequently
contradictory. In Babylonian texts the dates of various celestial
phenomena may be either observed or computed. The use of calculations
based on a combination of theory and observations was frequent.  Much of
the data recorded in both Astronomical Diaries and Almanacs are not
observation-based but computation-based. The comparison of the data in the
Astronomical Diaries and Almanacs demonstrates the absence of one unifying
and exact observation and computation scheme. Interestingly, all of the
data recorded in Normal Star Almanacs are predictions. Again, it is
obvious that discovering precession is not as easy as having a grandfather
who has a tree and passes down stories about his lifetime observation of
the night sky.

In his 1993 book, The Eye of Heaven : Ptolemy, Copernicus, Kepler the
American historian of science Owen Gingerich offered a succinct
explanation for the appearance of preciseness in Babylonian computation
schemes (Page 21): "But how could the Babylonians find the length of the
seasons so well, since it would have been no easier for them than for
Ptolemy to find the time of the solstice by direct observation? The answer
seems to lie in the idea that the Babylonian astronomy was thoroughly
dependent upon lunar observations, and particularly on a long series of
lunar eclipses. Over the past century the astronomical cuneiform tablets
have gradually been deciphered, and one of the most surprising things that
has emerged is the relatively high accuracy with which parameters can be
extracted from very approximate observations. Provided there are enough
records over a considerable period of time, even crude measurements
furnish quite reliable figures for planetary periods and for their
non-uniform motion along the ecliptic. In particular, the Babylonians
discovered that the lunar eclipses repeated in certain patterns, and that
the possible eclipses positions were more crowded together in the
direction of Sagittarius than in Gemini. This meant that the Sun was
moving more slowly when it was in Gemini, and more rapidly in Sagittarius.
From this observation it was possible to work backward and establish when
the seasons began without actually making daytime measurements of the
solstices."

In his paper "The Young Avestan and Babylonian Calendars and the
Antecedents of Precession." (Journal for the History of Astronomy, Volume
10, 1979, Pages 1-22)  Willy Hartner suggests that the tropical and
sidereal year were distinguished in Babylonian astronomy by 503 BCE and
that it implies knowledge of precession.  However, there is no evidence
that the Babylonians differentiated between the tropical and sidereal year
at all. Though the Babylonians, quite late, came to realize that there was
a difference between the tropical and and the sidereal mean longitude of
the sun there is no evidence that they could rationalise the discrepancy
and understand it as the Greek astronomer Hipparchus later did. In his
review of Bartel van der Waerden's 1988 book, Die Astronomie der Griechen
Alexander Jones writes (Isis, Volume 81, 1990, Page 332): "... van der
Waerden revives the old bogey of a Babylonian discovery of precession,
because of the discrepancy between the "sidereal" year underlying the
system A and B lunar theories and the "tropical" year derivable from the
Uruk solstice scheme. But this tropical year is merely a consequence of
the nineteen-year calendric cycle, which is both older and of a lower
order of accuracy than the lunar theories;  the tropical year implicit in
system A is identical with the sidereal year, while in system B there is
only a small discrepancy that results from the arithmetrical constraints
of the zigzag functions."

It is difficult to understand what is meant when it is claimed by the
"new"  Panbabylonists such as Giorgio de Santillana and Hertha von Dechend
that early cultures must have recognised or understood precession. In
seeking to establish who was the first to be aware of precession the
zodiac, the tropical points, and the mechanism of precession are not
wholly relevant. The questions to ask are: (1)  Who in antiquity appears
to have been aware of precession?; (2) Can a date for the awareness be
assigned?; (3) How did they come to notice it?; (4) What did they notice?;
and (5) Was an explanation attempted? However, some sort of vague
realisation without quantification or ability to describe it in terms of a
precise astronomical coordinate system is not exactly a firmly established
discovery. (See: Appendix 3: Defining Discovery) The expected easiest
observations of precession (by some early culture at a continuously
settled site)  would perhaps be (1) the 'shifting' horizon and changes in
the heliacal risings of stars (marker stars or otherwise), (2) the
pole-star and the replacement of one (marker star) by another over time,
and (3) calendrical systems and the adjustments to such. None of the
efforts using these arguments have been found to convincingly demonstrate
the awareness of precession prior to Hipparchus.  However, to perhaps
vaguely realize something about the effects of precessional shift is one
thing, and it is another thing entirely to suppose that they could have
discovered the precession of the equinoxes as did the later Greek
astronomer Hipparchus. (For 'discovery' to be made there would be no need
to match Hipparchus and his coordinate system explanation; simply
concluding the rate of stellar movement/shift is a systematic continuous
displacement , would be sufficient. Additionally identifying that it was
able to be calculated would be perhaps an unnecessary requirement to
consolidate 'discovery.') In his article "The Celestial David and
Goliath." published in 1995 (Journal of the Royal Astronomical Society of
Canada, Volume 89, Number 4, Pages 141-154) F[?].  Millar argued that the
ancient fear that "the sky is falling" was a description that identified
knowledge of precession. The article assumes that an early culture, using
the horizon as a measuring instrument, could identify both the slow
tilting effect of the sky and also the slow displacement of the pole star
and interpret the effects of both as a slow lowering of the sky. (For a
further example of pole star myths and collapsing skies see the myth of
Boahje-naste discussed in Finno-Ugric and Siberian Mythology by Uno
Holmsberg (1927).)  However, in interpreting ancient myths we can easily
succumb to reading into them whatever we would like to believe. Moreover,
the interpretation of myths most usually remains unverifiable.

For a short critique by Otto Neugebauer of the inaccuracies of Giorgio de
Santillana as an historian of early science see "The Survival of
Babylonian Methods in the Exact Sciences of Antiquity and Middle Ages." in
Proceedings of the American Philosophical Society, Volume 107, Number 6,
December 20, 1963, Page 531. See also the short critique of Giorgio de
Santillana by Asger Aaboe in the book review "Historians of Science." in
The Yale Review, Volume 52, Winter, 1962, Pages 326-328.

The authors of Hamlet's Mill hold that the clearest statement of
precession exists in the Erra-Epic (also known as the Erra and Ishum
Epic). (See: Hamlet's Mill by Giorgio de Santillana and Hertha von Dechend
(1969) Pages 325.) The authors write: "... it is necessary to leave Era's
somber prophecy unfulfilled, relating as it does to a coming world age:
"Open the way, I will take the road, The days are ended, the fixed time is
past." But with it comes the clearest statement ever uttered by men or
gods concerning the Precession. Says Marduk:  When I stood up from my seat
and let the flood break in, then the judgement of Earth and Heaven went
out of joint ... The gods, which trembled, the stars of heaven - their
position changed, and I did not bring them back." The authors fail to to
engage in any developed discussion, scholarly or otherwise, of this
section of the text. The source of the "Marduk quote" in Hamlet's Mill is
the late version of the Erra-Epic, generally believed by scholars to have
been written circa the eighth-century BCE, and is likely derived from (the
German-language)  book Das Era-Epos by Felix Gössmann (1956). (The author
of the Erra-Epic, Kabti-ilani-Marduk of the Dabibi-family, claimed that
the work was revealed to him in a dream. The Erra-Epic is written as a
dialogue between gods.) Which author of Hamlet's Mill made the
English-language translation is not known. Unfortunately Gössmann's
edition of the Erra-Epic has problems. In his review of the book (Archive
für Orientforschung, Achtzehnter Band, 1957-1958, Pages 395-401) the
Assyriologist Wilfred Lambert concluded it was not generally reliable. In
the Erra-Epic there is a scenario involving disorder affecting the earth
and heavens when Marduk temporarily leaves his throne. The context is an
apocalyptic type scenario similar to the Biblical book, Apocalypse of John
(i.e., Book of Revelation). (See the discussion in Cosmos, Chaos and the
World to Come by Norman Cohn (1993).  Erra is an Akkadian warrior god. The
result of Erra's assault is that the world is plunged into darkness and as
a result Marduk is displaced from his throne and forced to descend to the
underworld. Erra temporarily seizes control of Babylon from Marduk during
the latter's temporary absence. As the phenomena of precession is
completely unconnected with any occurrence of celestial darkness this type
of imagery can hardly be descriptive of precession. The actual overall
point being made by the story is the equilibrium of the physical and moral
world (both equally divine appointments) depend on the presence of the god
Marduk.

The theme of the chosen imagery of the Erra-Epic is believed to refer to a
disastrous military event that occurred to the city of Babylon in the
"dark age"  at the beginning of the first millennium BCE. The central
theme of the poem is concerned with the assault by Erra on the kingdom of
Marduk. Babylon was the residence of the god Marduk and the centre of the
universe. The disaster was interpreted in religious terms as the temporary
replacement of Marduk by Erra.  It is likely the poem is descriptive of a
raid by the semi-nomadic Sutian people on the city of Babylon. It is most
likely the Sutû raids of the 11th-century BCE were the background of the
Epic. The Sutû tribes created havoc in Babylonia shortly after 1100 BCE.
The Sutû (Aramaean tribes who lived along the Euphrates River)
periodically raided Mesopotamian cities. The attacks on the Mesopotamian
cities are stated in the Epic to be the work of the Sutû. The
Assyriologist Wilfred Lambert held that the reign of Adad-apal-iddina fits
the account of the Epic quite well. It has also been proposed that the
epic was composed following the recovery of the statue of Marduk from Susa
by Nebuchadnezzar 1 after its removal by the Elamite king Kutir-Nahhunte.
(The cult statue was an important feature of Mesopotamian religion. The
removal of cult-statues (or the key cult statue) of sacked city's patron
god/goddess by a victorious army as booty was viewed as a grievous event
by the inhabitants of the sacked city. It implied they had been abandoned
by their patron god/goddess.) This event is dated to the 12th-century BCE.
Circa 1160 BCE King Kutir-Nahhunte invaded Mesopotamia and took the city
of Babylon. Included amongst the items he brought back from Babylon was
the Code of Hammurapi. Circa 1120 BCE King Nebuchadnezzar 1 conquered
Elam.

Erra is the god of war and pestilence (and ultimately fire). For an
authoritative discussion that the Erra poem (a narrative poem) is not
myth; it is mythologised history, see the paper "The Epic of Gilgamesh:
Thoughts on Genre and Meaning." by the assyriologist A. R. George. For a
discussion of some content of the epic of Erra and I?um (its theme of
alternating destruction through flood and fire) as a possible mythological
antecedent to the later astronomical theory of the 'Great Year' see: "A
Possible Babylonian Precursor to the Theory of ecypr?sis." by Marinus van
der Sluijs (Culture and Cosmos, Volume 9, Number 2, Autumn/Winter, 2005,
Pages 1-19).(For the possibility of an additional astronomical
interpretation of the story, see Mesopotamian Planetary
Astronomy-Astrology by David Brown (2000, Pages 256-257).)

The "changes in symbolism" argument used by the authors of Hamlet's Mill
to claim that the shift from an "Age of Twins" to an "Age of Taurus" to an
"Age of Aries" to an "Age of Fish(es) is identifiable suffers from the
dual burden of wishful thinking and absence of evidence. "At time Zero
(say, 5000 B.C. - there are reasons for this approximate date), the sun
was in Gemini; it moved ever so slowly from Gemini into Taurus, then
Aries, then Pisces, which it still occupies and will for some centuries
more. The advent of Christ the Fish marks our age. ...  The preceding age,
that of Aries, had been heralded by Moses coming down from Mount Sinai as
"two-horned," that is, crowned with Ram's horns, while his flock
disobediently insisted upon dancing around the "Golden Calf" that was,
rather, a "Golden Bull," Taurus (Hamlet's Mill, Pages 59-60)."
(Interestingly, Hertha von Dechend, though raising the possibility of such
an interpretation in her M.I.T.  seminar notes, stated she did not favour
this particular explanation.)  Additionally, the voyage of the Argonauts
for the Golden Fleece (of a ram)  introduces the "Age of Aries" (Hamlet's
Mill, Page 318).

Other writers like to add in further examples such as the slaying of the
Cretan Minotaur symbolising the end of the "Age of Taurus." The cult of
the Apis bulls in Ancient Egypt is held to represent the "Age of Taurus"
and the Amun cult in Egypt is held to represent the "Age of Aries."

The "changes in symbolism" argument, which goes back to the 19th-century,
easily collapses with only a few criticisms. The date of Moses is usually
given as circa 1500 BCE. There was no zodiac circa 1500 BCE. so it is
impossible to have zodiacal world ages at this early date. Certainly there
was no scheme for equally dividing the ecliptic, or other established
convenient frame of coordinates, at this early date. As such equally timed
changes in "world ages"  is out of the question. In the case of Moses
having horns we have a simple translation error. The Hebrew root KRN can
be keren meaning "horn" or karan meaning "radiant." When the Hebrew bible
was translated into Latin the Hebrew KRN was mistranslated as "horned"
(and so instead of Moses' face being radiant it was horned). It has not
been demonstrated that the search by Greek heroes for the "Golden Fleece"
has anything to do with a constellation or astronomy. The Golden Fleece of
the Argonautica may be connected with the holy fleece of Hittite ritual.
It was a Hittite custom to hang a container made from the skin of a sheep
from a sacred evergreen tree in the centre of a grove. The fleece were
decorated with gold and the sheep skin container filled with offerings to
their gods/goddesses. However, it is common to interpret the Argonautica
as an adventure story recalling how early Greek mariners searched for new
territories to expand Greek trade.

The Cretan Minotaur was half bull and half man. Taurus is simply a
truncated bull. Why exactly the Cretan Minotaur should represent the
"zodiacal" bull (Taurus)  is never explained. Why Theseus killing it
should represent the end of the "Age of Taurus" is also never explained.
Nothing at all is known of Minoan constellations so no proof of any
intended association with a Minoan bull constellation is possible. The
Apis bull was believed to be the incarnation of the Egyptian god Ptah. It
has not been demonstrated that the Apis bull has anything to do with
astronomy. The identification of native Egyptian constellations is mostly
uncertain. The Apis bull has never been linked with a native Egyptian bull
constellation (at any time - let alone during a supposed "Age of Taurus").
Chronologically the cult was more popular during the supposed "Age of
Aries" than it was during the supposed "Age of Taurus." The Egyptian god
Amun was originally frequently depicted as the Nile goose and later more
frequently depicted as a ram, or as a ram-headed man. However, from the
cult's beginning's Amun could be depicted as either a Nile goose or as a
ram, or as a ram-headed man. Chronologically the cult originated in the
supposed "Age of Taurus."

The concept of precession-based zodiacal "world ages" is largely a
19th-century Theosophical concept invented by the occultist Helena
Blavatsky. Nick Campion identifies that the concept draws "partly on
Hesiod's sequence of ages outlined in the Works and Days, the Hindu Yugas,
some 19th century studies of comparative religion and Madame Blavatsky's
own theory of racial and spiritual evolution (Hastro-L, 13 April, 2000)."
(However, the concept of precessional "world ages" can also be traced back
to Origine des tous les cultes: ou, Religion universelle by Charles Dupuis
(1794).) Additionally, the constellations are all of uneven size and we
have no knowledge of the boundaries of any early constellations. We have
no knowledge of even the boundaries of the Greek constellation scheme of
Aratus of Soli circa 275 BCE.

If precession was known in early Babylonia we could reasonably expect it
to be recognised in some form of the mathematical astronomy that developed
and/or later calendar systems. (The Babylonians did identify and record
some long-term astronomical cycles such as the synodic periods of the moon
and planets.) It would seem that the Babylonians were limited by their
lack of interest in theoretical astronomy and they had no geometric scheme
to assist them. (See, however, Lengths, Widths, Surfaces: A Portrait of
Old Babylonian Algebra and its Kin, by Jens Høyrup (2002), for the
proposal that Old Babylonian algebra was not numerical but geometrical in
nature.) They simply applied arithmetic to data that the later Greeks
would apply geometry to. The concept of precession could be realistically
discovered and described only when geometric concepts had been developed.
This was only achieved by the Greeks. The earliest Greek geometry can be
traced to Thales of Ionia (635-543 BCE) and Pythagoras of Ionia (582-496
BCE).  (The rudiments of practical geometry are, however, found in the
earlier mathematical traditions of Babylonia and Egypt.) It can be
confidently stated that the phenomenon of precession was not identified by
the Babylonians (and so it is out of the question that it was understood
as a systematic continuous variation (i.e., that all stars have slow
continuous motions parallel to the ecliptic) and that the rate of
precession was measured).

Appendix 1: The Myth of Knowledge of Precession in the Eddas

It is not unusual to hear the claim repeated that knowledge of precession
appears in the Eddas (a collection of old Norse poems and tales dating
circa 10th-century CE). The claim simply rests on verse 23 of the poem
Grimnismál in the Eddas. At Ragnarok ("end of the world") out of each of
the 540 doors of Valholl ("hall of the dead" or "hall of the slain") will
come 800 warriors. (It is also pointed out that in verse 24 of the poem
there are 540 rooms (or "floor-rooms") in Thor's palace of Bilskirnir.)

Stanza 23 of Grimnismál has the descriptive lines:

"Five hundred doors and forty,

Think I there at Valholl;

Eight hundred einhergar go out one door,

When they go to fight with the wolf."

Valholl was the largest building in Asgard, the celestial realm of the
Norse gods/goddesses. The number of doors is multiplied by the number of
warriors emerging from each door to achieve an end number of 432,000
warriors. (This calculation and the resulting number of 432,000 is not in
the Eddas.) The claim is then made that the number 432,000 refers to a
precessional "great year."

It is correct that according some sources Valholl has 540 doors each wide
enough for 800 warriors. It is correct that the 540 rooms (or
"floor-rooms") in Bilskirnir can match the version of 540 doors of
Valholl. However, I do not recall any "associated number" such as 800 (or
960) warriors (or whatever)  connected with Bilskirnir. Also, according to
other sources Valholl has 640 doors each wide enough for 960 warriors.
Hence out of the medieval tale we can multiply the former figures and get
the resulting number 432,000 or we can multiply the latter figures and get
the number 614,400. The figure of 432,000 may be linked with the
Babylonian doctrine of "cosmic recurrence" (i.e., a "great year" linked to
"powerful" conjunctions, not a precessional "great year"). I have never
seen the figure 614,400 touted as belonging to either. (A prime candidate
for uncritically promulgating this sort of arithmetic is the Jungian
mythologist Joseph Campbell in his (for example) book The Masks of God:  
Occidental Mythology (1964, Page 459).)

The supporters of knowledge of precession in the Eddas seem to have no
knowledge of the old Germanic system of calculation. In the old Germanic
system of reckoning the "long hundred" had the value of 120. In all
likelihood the "five hundred ... and forty" and the "eight hundred" have
the Germanic "long hundred"  value (not the decimal value 100). Hence 640
doors and 960 warriors. Even orthodox writers may or may not indicate
knowledge of the old Germanic system of calculation. Norse Mythology by
John Lindow (2001) simply gives 540 doors and 800 warriors. World
Mythology by Donna Rosenberg (2nd edn., 1994) simply gives 640 doors and
960 warriors. Myth and Religion of the North by Edward Turville-Petre
(1964) gives both 540 (or 640) doors and 800 (or 960) warriors. An
important discussion of the issues by Magnus Olsen appeared in (the Danish
language) Acta Philologica Scandinavica, Volume VI, 1931-1932. (The
particular paper was later included in his collected papers Norrone
studier (1938).) See also "Numeracy and the Germanic Upper Decades" by
Carol Justus (Journal of Indo-European Studies, Volume 24, 1996).

References to Valholl can thus have the numbers 540 and 800 or 640 and
960.  References to Bilskirnir simply have the number 540 but not 640 nor
800 or 960.  Some people are keen to multiply 540 by 800 but not 640 by
960.

For the number 540 Vincent Hopper suggested (Medieval Number Symbolism,
1938, reprinted 1978) that the Medieval Norse (1) had an idealised 360 day
year calendar (adjusted by intercalation), (2) calculated time by half
years; and (3)  540 denotes a calendar cycle of 3 half years
(winter-summer-winter). It seems we may be playing with nothing deeper
than mundane calendar-based numbers.

A further (standard) study of Valholl is Walhall by Gustav Neckel (1913).
His opinion was the "five hundred ... and forty" doors intends to express
nothing more than a large number and was perhaps influence by Norse
knowledge of the numerous doorways (and vomitoria) of the Roman Colosseum
(Coliseum). There were 80 entrances at ground level. However, the
Colosseum incorporated a number of vomitoria - passageways designed so
that the venue could quickly disperse people into their seats (in 15
minutes), and evacuate them abruptly (in 5 minutes).

Appendix 2: The Recognition of Precession in China

The earliest archaeological evidence of a Chinese calendar appears on the
oracle bones of the late 2nd-millennium BCE. They demonstrate a 12-month
lunisolar year with the occasional arbitrary intercalation of a 13th- and
even 14th-month.  However, Chinese historical records place the origin of
a lunisolar calendar (of 366 days) to circa 3000 BCE. The development of a
calendar in China was closely related to the development of astronomy and
the needs of agriculture. (China was largely an agricultural society.)

The earliest tentative awareness of precession in China took hold in the
Hou Han (= later Han) period. (The later Han period is also now referred
to as the Eastern Han Dynasty and spanned from 25 to 220 CE.) During this
period it was quite widely recognised that the calendar altered (i.e.,
became unreliable)  every 300 years. That is, every 300 years there was a
requirement to use a new calendar. Multiple mentions of the fact that the
calendar was only good for 300 years appears in the multiple volumes of
the Hou Hanshu (= Book of the Later Han)  by the historian Fan Ye
(flourished 398-445 CE).

The discovery of precession - or at least the hunch of its existence - is
attributed by Wolfram Eberhard and Rolf Mueller to the Palace astronomer
Chia K'uei (30-101 CE) of the Han dynasty. The date they give for his
suspicion is circa 89 CE. (See: "Contributions to the Astronomy of the Han
Period III: Astronomy of the Later Han Period." by Wolfram Eberhard and
Rolf Mueller in Harvard Journal of Asiatic Studies, Volume 1, Number 2,
July, 1936, Pages 194-241.)

The discovery of the precession of the equinoxes in China can be
attributed to the scholar Yü Hsi (flourished circa 307-338 CE) circa 320
CE who discussed it in his book, the An Thien Lun written 336 CE. (The
book discussed whether the motions of the heavens were stable.) Yü Hsi
obtained a value of about 1 degree in 50 tropic years for the precessional
movement.

The brilliant scholar Zu Chongzi (420-500 CE) created the Daming Calendar
(some sources say promoted his father's calendar ) which took precession
into account for the first time. The most thorough and comprehensive
calendar in the history of China was the Dayan Calendar compiled in the
Tang Dynasty (616-907 CE) by the monk Yi Xing.

Appendix 3: Defining Discovery

Some persons resolutely claim (including Hamlet?s Mill supporters) that
the Chinese discovered precession prior to Hipparchus. The nature of what
can constitute ?discovery? needs to be qualified/described. A primary
concern of any science is the categorisation, description, and definition
of phenomena.  Definition is fundamental to the scientific enterprise, and
listing criterial features of categories is fundamental to the process of
definition.

I think it is perhaps rare in science to find definitions on which more
than a few persons will agree - even perhaps for the most fundamental
terms. Continual breakdowns in the use of terms are readily apparent in
professional publications (however, all ideas are remain ?up for grabs').
Many definitions become cluttered with conditional stipulations and can
comprise a lengthy paragraph. I believe definitions should be readily
functional. I also doubt if 'traditional' concepts of discovery are
careless.

If someone convincingly demonstrates they have found a description of
precession in a myth then this demonstration becomes a discovery for the
person. Whether the material in the myth shows 'discovery' of the
phenomenon of precession is a separate issue.

The method/process/stages of scientific investigation for the purpose of
discovery should not be confused with actual discovery. The professional
literature still reflects the view that the process of discovery is not
adequately understood.

I would offer that the process of discovery of phenomenon such as
precession involves perhaps: (1) inception (instance of commencement - an
intriguing/baffling observation (description - the positions of several
marker stars have apparently moved) and decision to follow-up the
significance and think through/analyse and make 'sense' of the
observation(s)), (2) emergence (something becoming apparent - it is the
not inaccurate technique by an observer(s), rather the positions of some
marker stars are not fixed) using process of evaluation/analysis, and (3)  
concept (an idea/inference constructed from specific instances - (the
explanation - the marker stars (the other 'fixed' stars) progressively
shift position (discovery)). Discovery is an outcome - an achievement. The
preceding steps would fall under process.

Precision of language used in an explanation is important for deciding
whether a ?discovery? has been made, and the nature of that discovery.

Randomly noting an effect/effects of precession without understanding is
only a discovery in the weakest sense - it is a discovery of change (an
'effect' discovery). I would class it as observation/observations of
change. The process of investigation and analysis and explanation-making
is absent. Knowledge is perhaps not so much the problem to be
investigated/solved but the 'answer,' usually, I think, achieved through
extrapolation.

The conclusion that the rate of stellar movement is a systematic
continuous displacement able to be calculated (within a coordinate system)
demonstrates/consolidates the confidence, reliability, and strength of the
discovery (a 'technical' discovery).

Observation of change by itself (effect(s)) related to the phenomenon of
precession is not discovery of precession and perhaps to label it as
'discovery of change' is not really suitable. This does not exclude the
terms 'collective discovery' and 'pre-discovery.' However, their
definitions/use become an important issue.

A modern analogy is the accidental discovery of the aberration of light
(also referred to as astronomical aberration or stellar aberration) by the
English astronomer James Bradley. (One of the reasons for the apparent
displacement of the stars due to the earth's motion is what is known as
aberration.) The discovery arose out of the attempt by James Bradley
(1693-1762) and Samuel Molyneux to detect stellar parallax. (A popular
account of the course of his discovery is given in Astronomical Discovery
by Herbert Turner (1904).) On the basis of quantitative observations the
phenomenon was first noticed in late 1725 by way of unexpected changes in
the position of ? Draconis, unrelated to parallax. Prolonged observations
of changes in the position of ? Draconis convinced him that it could not
be parallax he had measured.) Explanations that the anomalous measurement
were an error due perhaps to a fault with the telescopic instrument, the
plumb-line, or perhaps the effect of refraction were considered and
dismissed. Bradley (a determined and meticulous astronomer) was originally
ignorant of what his initial observation(s) meant by way of explanation.
(The cause of anomalous motion was at first completely obscure.) He
pursued an explanation for 3 years before he found the real explanation.
In 1729 he communicated his discovery and explanation to the Royal Society
(of London)  with the publication of his (celebrated) paper in the
Philosophical Transactions of the Royal Society (Volume 35). He later
discovered the nutation of the earth's axis (the periodic oscillation of
the earth's axis, caused by the changing direction of the gravitational
pull of the moon on the equatorial bulge He delayed publication of his
discovery of nutation until he had tested its reality by minute
observations during an entire revolution (18.6 years) of the moon's nodes.
He finally announced his discovery in print in 1748 in the Philosophical
Transactions of the Royal Society.

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