What are the Origins of Astronomy?
Astronomy has often been seen as field first developed by ancient Greek scholars, but its origins most likely stretch back to before recorded history. We know that astronomy has played a vital role in the agricultural cycle and early religions. These early innovations have led to major advancements in developing our calendar, a system of time, understanding of astronomical movements and prediction, coordinate system, and mathematical developments.
Most likely astronomy begins to develop when agriculture becomes significant in the Neolithic in the ancient Near East. However, we only learn about astronomy in the 3rd and particularly in the 2nd millennium BC. By this time, astronomy had developed in part to regulate the agricultural cycle; however, perhaps more significantly for ancient Mesopotamian societies, it was used to create a calendar utilized in the worship of gods.
In effect, much of the learning that had to do with the understanding of the movement of celestial bodies were generally conflated with astrology. The signs of the zodiac were invented in Mesopotamia probably by the 3rd millennium BC. Specifically, this occurred in southern Mesopotamia, a region that eventually became synonymous with Babylonia and by extension the Babylonians, who provided much of our knowledge of how ancient astronomy developed there.
The first astronomers were priests who were responsible for recording their observations on cuneiform tablets (Figure 1). Their observations were utilized as signs from the gods, and that information was then interpreted to understand events that might affect the king and his kingdom.
Although on the surface these seem to be nothing more than a system of superstition, the nearly continuous observation, over many centuries, of the celestial bodies led to subsequent developments that have influenced our scientific progress in the area.
Humans developed systems to understand where specific bodies, i.e., stars, moons, planets, comets, and asteroids, would be to interpret and provide omens to their information to their communities to both understand the past and predict the future.
This led to the creation of a calendar that would be timed around the movement of the moon in particular and also a system to predict when specific events would occur, such as eclipses. The eventual calendar that emerged began to have features we now also have in our calendars.
The calendar was based on the lunar cycle but also the rotation of the Earth around the Sun, thus a form of a lunisolar calendar, giving the calendar 12 months, with the name of the months still used in Arabic and other Near East calendars. Leap months were utilized to make up for the shortfall in days for a given year. Because the Babylonian calendar was relatively accurate, this means many historical events that are recorded in their calendar could be dated to the exact day in some instances. For instance, we know the exact time in which Halley’s comet was observed for the first time (Figure 1). While Herodotus is often called the first historian, more accurately the Babylonians should have this title as they provide the first set of accurate ancient dates anywhere in ancient history.
Other achievements include the understanding that solar and moon eclipses occur in periodic cycles that can be predicted. This eventually led to the system we call the Saros system, which is a system still used to predict eclipses. The world Saros derives from an Akkadian (i.e., the language used in much of Mesopotamia) word. In general, the system used by Mesopotamians, or more specifically the Babylonians, to calculate lunar orbit was considered to be highly accurate.
Additional innovations include the idea that the sky can be divided into coordinates using 360 degrees. This invented the idea of a coordinate system used for any type of spatial mapping, which is a system we still use. In Mesopotamia, a sexagesimal system for counting and recording numeric data such as coordinates made keeping track of location convenient. This also works well for a time, and this Mesopotamian sexagesimal system is what we have inherited for use in the measurement of time, while also using the Babylonian system in our own coordinate systems.
The need to keep track of time, record the location of celestial bodies in a type of coordinate system, and predict when events such as eclipses would occur meant that in Mesopotamia geometry had to be well developed. By at least the 2nd millennium BC people already understood the measurement of angles, the Pythagorean theorem (i.e. long before Pythagoras lived; Figure 2), and measurement of circular surfaces. As an example, the Babylonians had already known that Pi was slightly greater than 3.1 in value.
- For a history of astronomical developments and mathematics in Mesopotamia see: Hodgkin, Luke Howard. 2013. A History of Mathematics: From Mesopotamia to Modernity. Oxford: Oxford University Press.
- For information on how early observations may have developed or utilized in agriculture and religion, see: Olson, Richard. 2010. Technology and Science in Ancient Civilizations. Prayer Series on the Ancient World. Santa Barbara, Calif: Praeger, Pg. 99.
- For information about the development of the Zodiac signs, see: Nardo, Don. 2009. Peoples and Empires of Ancient Mesopotamia. Lucent Library of Historical Eras. Farmington Hills, MI: Lucent Books, Pg. 108.
- For information on Mesopotamian (or Babylonian) astronomers, see: Powell, Robert, and Kevin T. Dann. 2010. The Astrological Revolution: Unveiling the Science of the Stars as a Science of Reincarnation and Karma. Great Barrington, MA: Lindisfarne Books.
- For Information on observations and mathematical concepts used to determine the movement of celestial bodies in Mesopotamia, see: Ossendrijver, Mathieu. 2012. Babylonian Mathematical Astronomy Procedure Texts. New York, NY: Springer. http://dx.doi.org/10.1007/978-1-4614-3782-6.
- The Calendar system of the Babylonians is discussed further here: Cohn, Marc. 2007. The Mathematics of the Calendar. Raleigh, NC: Lulu.com, Pg. 6.
- For information on the Saros system and its development, see: Aaboe, Asger, ed. 1991. Saros Cycle Dates and Related Babylonian Astronomical Texts. Transactions of the American Philosophical Society, v. 81, pt. 6. Philadelphia: American Philosophical Society.
- For Information on the Babylonian sexagesimal systems, see: Ore, Øystein. 1988. Number Theory and Its History. Dover Classics of Science and Mathematics. New York: Dover, Pg. 2.
- For Information about Babylonian geometry, see : Rudman, Peter Strom, and Peter Strom Rudman. 2010. The Babylonian Theorem: The Mathematical Journey to Pythagoras and Euclid. Amherst, N.Y: Prometheus Books.
- For Information about Pi in Babylonia, see: Beckmann, Petr. 1976. A History of [pi]. Repr. New York: Barnes & Noble, Pg. 21.