Understanding the Seasons
Time & Its Measurement
& Lunar Eclipses
Archaeoastronomy is the practical use
of astronomy as it applies to early cultures. It is of interest to astronomers
and archaeologists because it encompasses the study of astronomical
principles employed in ancient works of architecture (sometimes referred
to as astroarchaeology) as well as the practice of astronomy and methods
of observations among ancient peoples.
ORIGINS OF ASTRONOMY AND ASTRONOMICAL OBSERVATIONS
The importance of astronomy to all ancient
cultures stemmed from a practical need to establish a precise method
for telling time, monitoring agricultural events, performing religious
ceremonies, and regulating governmental activities. Early people discovered
that the systematic progression of the seasons was matched to the rhythmic
motions of the heavens, and that the sky was a far more accurate indicator
of these cycles than making systematic observations of the weather.
People realized that the movement of the sun
across the sky could fix the day and its divisions, while the changing
phases of the moon established the month ("moonth" in Old
English). By observing the rising or setting of a specific star when
near the sun (heliacal rising or setting), the year could be defined.
And, because there were seven objects which moved against the starry
background; five planets, the moon, and the sun, the popular notion
of the week came to fore.
Ancient cultures did not understand the true
physical nature of these seven wanderers in the heavens, so it was only
natural to deify them and to closely monitor their changing positions.
Those individuals who became proficient in these tasks were able to
wield enormous power with the populace and ruling infrastructures; so
much so, that they were venerated as priests and allowed to exist as
a separate, almost untouchable segment of society. They designed temples
with astronomical alignments to track the extreme positions of the sun
and the moon. In a sense, these structures acted as permanent calendars.
Eventually, in the Middle East, a complex series of rules were devised
to relate this celestial dance as an indicator of human destiny. The
pseudoscience of astrology with its many different types of horoscopes
was a direct result of this synthesis.
THE ANASAZI INDIANS OF THE SOUTHWESTERN US
About 500 AD, Indians who lived in the upper
Rio Grande, Colorado, and San Juan river basins of what is today, Utah,
Colorado, Arizona, and New Mexico, began to abandon their nomadic existence
for the richer rewards of a more stable and settled agrarian lifestyle.
Instead of seasonal migrations from region to region, as hunters and
gatherers, crops were planted on a regular basis to insure a more consistent
and varied food supply. In good years, food surpluses were realized
which helped sustain villages against times of famine. Collectively
these people were known as the Anasazi, a Navajo word meaning "ancient
ones" or "ancient enemies." The Navajo never knew the
Anasazi, for when they migrated into the Four Corners area during the
fifteenth century, they only discovered their silent ruins.
The Anasazi lived in harmony with nature, and
as a result they were keen observers of the earth and the heavens. Most
of their waking hours were spent out-of-doors surrounded by blue sky
and yellow rock. They could tell impending weather changes by monitoring
insect activity or wind direction. The rhythmic changes of the heavens
set the tone for daily, monthly, and yearly calendric cycles. Farming
was difficult because rainfall was scarce. Most of the annual precipitation
came in short bursts, during thunderstorms which occurred mainly in
the spring and summer months. Temperatures could range from -10°
F on the coldest winter mornings to around 100° F on many summer
The Anasazi dwelled in family or clan units
on mesa tops or in the many protective enclaves afforded by surrounding
cliff walls. They built their pueblos (towns) and ceremonial structures
from the abundant sandstone rock which was all around them. A distinctive
feature of pueblo architecture was the kiva, a roofed ceremonial room,
found usually below ground level, and almost always reserved for males.
This may possibly be explained by the fact that Anasazi society was
matriarchal. Women held property rights, and family names were passed
down through the wife? relations. Divorce, Anasazi style, was simply
the wife putting the husband? belongings outside of her pueblo. Men
and boys had to have a place to congregate, and the kiva was thought
to be used to that practical end.
Anasazi men and women were short and lean. Average
heights were about five feet, slightly higher for men and lower for
women. Weights were about 100 pounds. Life spans averaged under 30 years
with men living longer than women. Arthritis and bad teeth were often
contributing factors to an early grave, as well as a high child mortality
EARLY CULTURES AND THE SKY
- What were the conditions which allowed ancient people
to make good astronomical observations thousands of years ago?
The culture had to possess a
- Functioning language or some method of communication
- Practical, working knowledge of mathematical principles
- Sufficient longevity of its population to observe the repetition
of cyclical events
- Early people probably did not understand the relationships
in movements between the earth, moon, and sun. They were, however,
able to measure their positions and establish alignments which served
as monitoring devices.
- Objects and observations of interest to early humans
- Sun: Solstitial sunrise and sunset positions. For the
northern hemisphere, the sun rises at its most northerly and southerly
positions on the dates of June 21 and December 21 respectively.
- Moon: Major and minor standstill positions. These represent
the extreme positions of moonrise and moonset along the horizon.
- Helical rising of a star: This was not applicable for
Stonehenge, but the Egyptian's first observations of Sirius before
sunrise pinpointed their year and the annual flooding of the Nile
- Bright Stars and their rising positions: Certain stars
signal seasonal changes.
- Conjunctions (objects appear close together in the sky)
and eclipses of the sun and of the moon.
- Methods of observation
- Menhir: Standing stones which were used as positional
markers, usually associated with European megalithic sites.
- Foresight: A distant mountain or conspicuous geographical
feature which the sun rises or sets behind.
- Backsight: The position from which the observations
- Stationary observer: The observer watches the changing
position of the rising or setting sun against the features of
a distant horizon. Stone circles or other isolated menhirs between
the backsight and foresight could have been used as markers to
indicate the extreme positions of the sun or moon or other religious
and agricultural events. In this manner a calendar could have
been established. The use of intervening menhirs in American Indian
observations did not usually occur.
- Observer moves: Distinctive notches on hillsides located
miles away from the observer could have been used as foresights.
The observer would have positioned himself (at a backsight) so
that each day the sun would have risen or set behind the same
geographical point, i.e., a notch in a mountain peak. Since the
location of the sun would have shifted from one day to the next,
the observer would have continuously changed his backsight location
to keep the sun rising behind the same geographical location.
He could have marked these changing positions with a series of
stones. He would have easily noticed when the solstice occurred
(longest or shortest day of the year, marked by the most northerly
or southerly rising positions of the sun), since afterwards,
he would have been retracing his steps as the sun moved in the
- Windows/Ports (small openings) and doorways, etc.:
A building is designed in such a manner that hallways/doors/windows
(ports) permit the passage of sunlight or moonlight into certain
parts of the structure at certain key times of the year or when
these objects are in certain key positions. The entire structures
themselves or the alignment of ports create the markers which
can be used to establish a yearly calendar.
- Sun Daggers: The passage of sunlight through natural
or contrived rock formations creates a dagger-like image on another
rock face at certain key times of the year. The most famous of
these observatories is the sun dagger atop Fajada Butte in Chaco
Culture National Historical Park in northern New Mexico.
- Stonehenge: Europe's best known and most visited
- Introductory remarks
- Megalithic astronomy: Deals with structures
built from large stones which have an astronomical relationship.
Megalith means large stone.
- What was Stonehenge? A megalithic calendar
used to monitor the positional movements of the sun and moon
for agricultural purposes and possibly for use as a computational
device for the prediction of lunar eclipses.
- Location: In south central England, about
two hours west of London, near the town of Salisbury, just
off Route A344.
- Size: Smaller than expected, especially
when viewed from the perimeter fence, but impressive when
walking within the stone circle and horseshoe.
- Description: A very shallow round ditch,
flanked internally by a low bank (320 feet in diameter) is
concentric with a circular group of standing stones, called
sarsens (100 feet in diameter), capped with lintels. Inside
of the sarsen circle there are five huge freestanding trilithons
(three are still complete) shaped like a horseshoe with the
open end pointed to the northeast, toward a large menhir called
the heel stone, about 70 feet from the ditch and 256 feet
from the center of the monument. See the map of Stonehenge
on the next page.
- Stonehenge nomenclature
- Sarsen: Name given to the large uprights (25-50
tons) which form the circle and central horseshoe. It
is also the name of the rock itself. These were found
at Marlborough Downs, 20 miles to the north of the monument.
- Lintel: Term used to denote the cross slabs of
worked stone which lie on top of the sarsens.
- Bluestones: Smaller stones (five tons apiece)
which were transported mostly by water from the Prescelly
Mountains of southern Wales to Salisbury Plain. Their
significance is unknown.
- Trilithons: Name given to the five freestanding
sarsen and lintel caps which form the central horseshoe.
These were used as key seasonal markers.
- Heel stone: A large menhir about 256 feet to
the northeast from the center of the Stonehenge structure.
The sun rises over the heel stone on the summer solstice.
- Aubrey holes: A series of 56 holes spaced at
16 foot intervals forming a circle 288 feet in diameter.
They may have been used as a predictor for lunar eclipses.
- 'Y' and 'Z' holes: There are 30 Y holes and 29
Z holes. The Y's form a circle about 35 feet outside of
the sarsen circle, and the Z's form a smaller circle lying
from five to 15 feet outside of the sarsen circle. They
may have been used to measure the phase period of the
moon, which is 29-1/2 days. Even though there is a number
30 Z hole, Z hole 8 is missing, allowing for only 29 Z's.
Sometimes the Aubrey holes are referred to as the X holes.
- Station stones: Originally there were four sarsen
stones in the shape of a rectangle (two are missing) which
paralleled the axis of the summer solstice sunrise.
- The construction of Stonehenge: Three major phases
- Stonehenge I: Ditch-bank circle, four
small post holes, two larger post holes, heel stone plus narrow
circular ditch, 56 Aubrey holes
- Date: 2800 BC
- Construction period: 40 years
- People: Late Stone Age people (Windmill People)
who came from Europe (4300 BC) bringing with them agriculture,
cattle, primitive wheat,flint, bone tools and pottery.
They built long earthen barrows for the burial of their
- Stonehenge II: Bluestones were erected in
two concentric circles about six feet apart and 35 feet from
the monument's center. This construction was never completed.
The old ditch-bank entrance was widened by 25 feet, construction
of the Stonehenge avenue to the Avon river two miles away.
The station stones were thought to have been placed at this
- Date: 2130 BC
- Construction period: less than 100 years
- People: Beaker people. Came from Holland and
the Rhineland (Germany). They introduced the use of worked
metal and beer to Britain and dominated the economy of
southern England. They got their name from the elaborate
clay beakers they often buried with their dead.
- Stonehenge III:
- Date: 2075 BC
- Construction period: 50 years
- People: Wessex people. The blending of various
clans of Beaker people formed the Wessex group. Dominated
by a wealthy, powerful aristocracy whose trade routes
extended into central Europe, Ireland, Crete and Greece
- Three different periods of construction
- Erection of trilithons in the horseshoe pattern
(45-50 ton uprights) and the outer ring of sarsens
and lintels (25 ton uprights). Erection of slaughter
stone? Double circle of bluestones were removed to
an unknown location.
- Erection of bluestone oval within the trilithon
horseshoe, 'Y' and 'Z' holes dug, bluestone oval dismantled,
erection of altar stone at the monument's center.
- Erection of bluestones in a horseshoe pattern within
the trilithon structure to match its shape, and a
bluestone oval between the trilithons and the outer
- Numerous alignments at Stonehenge were discovered by
Gerald Hawkins in the mid 1960's. They can be divided into two main
- Group one: Alignments involving Stonehenge I
- Sun: Summer and winter solstice sunrise and sunset
- Moon: Northern and southern major and minor standstill
- Alignments involving the sarsens of Stonehenge III
- Sun: Summer and winter solstice sunrise and sunset
- Moon: Northern and southern major and minor standstill positions