Early History of Astronomy
of day/night: Keep track of time for planning and orientation;
later also for navigation purposes. Use the position of the Sun and
its phase), and the fixed stars.
of year: Season
changes, marked by equinoxes and solstices (celebrated with decorated
trees, yule logs, mistletoe and communal celebrations, for example),
were important dates for agriculture and hunting. Again, use the motion
of the Sun, Moon,
planets: In the bronze age around 3000 BC, five were known,
out to Saturn. Their wandering motion made them less useful for orientation,
but they were used for calendars and astrology.
Prehistoric Period - Early
Sites and Archeoastronomy
- Earliest evidence: Cave paintings
like the ones at Lascaux (16,000 yr old) and others including depictions
of celestial objects (stars, 5000-yr old map of the Moon).
- Earliest structures: Examples
with calendar circles, aligned markers to keep track of time of year,
like Stonehenge (3100-1550 BC) and many others [Goseck (5000 BC), Nabta (5000-3000
- America: Caracol Temple by Mexico's
Mayas in the Yucatán peninsula; Aztec Templo Mayor in
Tenochtitlán; Big Horn Medicine Wheel by the plains Indians
in the US.
- Early Development of Ideas
- The Middle East: Rich societies
at commercial crossroads after 3000 BC; Mesopotamians (astrology and
prediction, sexagesimal number system), Egyptians (practical needs
like predicting floods, aligned buildings).
- Greeks: Emphasized the need for explanation
and understanding; Developed conceptual models based on their naturalistic
(as opposed to mystic) philosophy and interpretation of the universe;
Used measurements and knowledge of geometry.
- Aristotle (IV cy BC): The
most important figure, wanted to develop an understanding of all
natural phenomena. In physics, the natural state of an object is
rest, heavier objects fall faster than light ones; In astronomy,
he argued for a geocentric model (Earth is the center of all motion):
we have no feeling of motion, no wind, no stellar parallax; the Earth,
Moon, Sun, planets, and stars are spheres; and time is uniform and
ever-flowing. Most of his views dominated until the XVII century.
Classical Period - Early
Solar System Models
- Setting: Alexandria, founded
by Alexander in 332 BC, became Egypt's capital with Ptolemy I
(one of his generals), and an international cultural center.
- Eratosthenes (III cy BC): Believed
the Earth is a sphere, and measured its radius.
- Aristarchus of Samos (III cy BC):
Contrary to most people, believed in heliocentric
model; also calculated sizes and distances to the Sun and Moon,
- Hipparchus of Rhodes (II cy BC):
Wrote a star catalog in which he introduced the magnitude system; also
calculated the length of the year and discovered the precession of
- Ptolemy (II cy AD): Followed Aristotle's
ideas; Perfected a geocentric model which survived for 1300 years,
preserved and refined by Arab astronomers; Wrote the "Almagest";
[latitude and longitude; North = up, South = down; stellar magnitudes.
- How do planets move? Their changes
of speed and retrograde motion, was explained assuming they moved
on large circles and epicycles; [Observations at the time were
accurate to about 10'].
- Medieval ideas: Stars are "holes"
in the surface of the celestial sphere, that let light from behind
- Arabs (VIII-XV cy): New instruments,
mathematical tools, many names of stars; contacts with Eastern
scholars (mainly Indian and Chinese); Studied, criticized and
improved Aristotle's and Ptolemy's ideas; Reintroduced them to
European thinkers during the XII and XIII centuries, paving the
way for the Renaissance.
- Chinese: As part of the imperial
establishment in ancient China, an astronomical observatory was
usually built inside the capital city. Trained astronomers were
appointed to keep a diligent watch of the sky day and night,
and recorded important events (eclipses, comets, "new"
stars...) for astrological reasons.
- Renaissance Europe: Beginning
of development of science; Took over Eastern knowledge and accumulated
observational records, used technological advances.
- Other cultures: Temples with
astronomical alignments and images in Asia; The Great Enclosure
in the archaeological site of Great Zimbabwe from the 1300s...
page by luca bombelli <bombelli at olemiss.edu>,
modified 31 jan 2013