AY 101 Study Guide - Summer 2018, Comprehensive Midterm Notes - Earth, Sun, Planet
AY 101
MIDTERM EXAM
STUDY GUIDE
Fall 2018
Archaeoastronomy
Archaeoastronomy is the study of ancient (pre‐technological) humankind's awareness
of celestial phenomena and its influence on their societies. A number of these
influences in ancient societies have been identified, including how structures were built,
early forms of calendars, and the development of mathematical concepts.
Ancient structures
Ample evidence exists that in ancient times, many cultural groups all over the world built
single structures, buildings, and even cities facing in astronomically significant
directions. For example, the Newgrange passage grave in Ireland (circa 3200 B.C.)
faces the mid‐winter sunrise, and Stonehenge, in southern England (circa 2800 B.C.),
points toward the mid‐summer sunrise. Similarly, various Mayan buildings in
Mesoamerica show relationships to significant horizon rise and set positions for the
planet Venus.
Early calendars
Before ancient humans recognized that the yearly cycle predictably repeats itself, they
regulated agricultural, hunting, and religious activities by directly observing celestial
phenomena. These phenomena included solar position against the background of stars,
the cyclic north‐south oscillation of the Sun's rise and set positions on the horizon, or
the pattern of nighttime constellations. Evidence of early peoples' celestial timekeeping
include the orientation of Stonehenge, which suggests a calendrical awareness, and the
Sun Circle (circa 1100 A.D.) built by the people of the Indian city of Cahokia, Illinois.
Navigation
When societies embarked on extended travel where natural features on land were not
available, the sky provided an alternative means to mark one's position during journeys.
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The Polynesians were experts at using the apparent positions of stars in the sky to
navigate across the vast expanses of the southern Pacific Ocean. In the same manner,
traders crossing the featureless tracks of the Sahara Desert used the sky for their
directions. It has been argued that our oldest constellations may date from the
delineation of stellar patterns as mnemonic devices for Mediterranean navigation as
early as 3000 B.C.
Mathematics
In due course, as societies accumulated extensive observations of the sky, there
developed the desire to understand celestial events in a quantitative fashion. The 360
degrees of the circle is the most tractable approximation that the Babylonians could
make for the annual circuit of the Sun around the sky in 365.25 days. Islamic scholars
were inspired to develop spherical trigonometry for navigational reasons as well as for
the Islamic tenet to pray toward the city of Mecca.
Other cultural influences
Awareness of phenomena in the sky has affected other aspects of cultures.
Descendancy from the celestial deities of the Sun and Moon was used in many past
societies to justify political supremacy. The development of mythologies, astrologies,
and religions also contain elements that help societies obtain a sense of order regarding
the workings of celestial events.
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