For convenience the article about Yuga is divided into five parts.
- Emergence of the Yuga System
- Yuga Definitions in Mahabharata
- Yugas mapped to Common Era
- Events in Chatur Yuga 1
- Events after Chatur Yuga 1
This is the first part of the article about Yuga, where we will discuss on the emergence of Yuga System as a time frame to record prehistoric events.
People who study ancient India and ancient Indian history often accuse that ancient Indians were poor in keeping track of time. They say that ancient Indians were brilliant mathematicians, astronomers, builders, architects and philosophers but were not good historians. To record large durations of time, they have used a time-framework called the Yuga-System. Like we now describe that a certain event happened in 200 BC or 500 AD, they described that the event happened in Dwapara Yuga or in Treta Yuga. Yuga system is often criticized as inaccurate or as impossible to map into modern time-frameworks. In this article I am trying to analyze the Yuga system from information available in Mahabharata. Attempt is made to map the Yuga time-frame into current time-frames.
To understand how the Yuga system came into being one need to understand the original meaning of the Sanskrit words like Yuga and Nakshatra, the various schools of ancient astronomy like the Lunar and Solar astronomy and also about the ancient Indian astronomers, their stunning discoveries and the royal dynasties who employed these astronomers in keeping track of time.
The ancient meaning of the word Yuga
The Sanskrit word Yuga is derived from the root Yuj meaning to join or to yoke. Since the two wheels of a chariot is yoked (joined) by an axle, the word Yuga also served to denote the axle or axis of a chariot. This is why in many allegories in Mahabharata and other texts we find Yuga compared to the axle of a chariot. In the same way ancient Indians had the concept of an axle (axis) for Earth, considering Earth to be spinning about this axle or axis. If we analyze ancient Indian texts we find that they initially thought the Earth to be a stationary flat land mass of different shapes with many oceans and continents. Sky with its stars, sun, moon and planets is thought as moving around Earth as a giant enveloping sphere, the celestial sphere. Subsequently Earth was modeled as a wheel spinning about its axis and finally as a sphere spinning about its axis close to what we now understand. The term Yuga was then used to denote this axis of Earth. As Earth rotated about its axis, the stars in the night were found to travel in circles about a center. Some times this center coincided with a prominent star, like it now coincides with the Pole Star. Sometimes (after several centuries) no star would be present at this center and some times another star coincided with this center. The ancient Indians knew that this center-point was the projection Earth's axis upon the sky. Thus, the ancient Indians made a remarkable discovery that the axis of rotation of Earth is shifting. Due to many centuries of continuous observations, they understood that the axis of Earth is rotating slowly with respect to the fixed stars in the night sky.
The ancient meaning of the word Nakshatra
The astronomers among the ancient Indians had already divided the sky into 30 divisions of 12 degree each called Nakshatras. Currently the word nakshatra means star. But in ancient times the word was used to denote divisions of the night sky. The word Nakta (Nak in short) means night. The word kshatra means field or region like in Ahi-kshatra meaning the region or field of Ahi (Nagas) and like in Kshatra-pati the ruler of the field / region / kingdom / empire. Thus the word Nak-kshatra would mean fields or regions in the starry night sky. Since in ancient days there was no possibility (no high-precision instruments) of marking these 30 divisions on the sky, they associated each of the Nakshatras (the 30 divisions of sky) to the prominent stars belonging to those divisions and began to call these stars by name. Thus the word Nakshatra also started to denote stars. The word Naksha meaning map also is connected with the word Nakshatra. The original meaning of the word, viz. Nakshatra, viz. field started to mean the field / region around each prominent star or the map of the star-field visible in the night sky. The number of prominent stars varied from 33, 32, 30, 29 and 27.
The astronomers of ancient India
Astronomers were also the time keepers of ancient India. They were employed by ancient Indian kings to keep track of time. The ancient Indian astronomers followed the motion of Sun and Moon across the sky. Some where specialized in the motion of Moon across the starry night sky. Some others were specialized in the motion of Sun across the sky. Among the astronomers of of ancient India were sages like Agastya, Vasistha, Parasara, Vyasa, Vrihaspati, Sukra, Budha and the Valikhilyas. The Vanara tribes in southern India too were good observers of the sky. Sage Markandeya too was an expert in the motion of luminaries in the sky. Asura Maya had considerable knowledge of astronomy. Rakshasa king Ravana was yet another expert in the motion of planets, which led to the myth that the planets like Sani and Kuja were under his control.
Solar Astronomers usually lived in low latitudes. Solar astronomers discovered the division of time called a year as the time taken by Sun to complete one revolution in the sky. The kings who followed solar astronomy later became known as the Solar Dynasty kings. The Ikshwakus and Raghus were solar dynasty kings. They had at some point of time lived in central and southern India. Dakshina Kosala (Chattisghad) was one of their ancient kingdoms, situated in central India. They were more aware of the circular motion of the Sun across the sky rather than the north-south pendulum like motion of the Sun which is not prominent in lower latitudes but visible clearly in higher latitudes. Their one year constituted 365 days. The solar astronomers later came into contact with the Lunar Astronomers who followed the motion of moon to record passage of time. Then they divided the year into 12 divisions of 30 degree each called the Raasis. The time the Sun spend in a single Raasi was thus around 30 days, which was more or less equal to the month (one revolution of Moon, 29 days) followed by the Lunar Astronomers. Thus the Solar Astronomers synchronized their calender with the Lunar Astronomers. Agastya was one of the prominent astronomer from the low latitudes (South India).
Valikhilyas (valkhilyas / valikhilya) were an ancient tribe, whose main occupation was to study the motion of Sun across the sky. They were among the most ancient astronomers. They were mentioned as short in height (dwarf bodied). They probably lived in southern latitudes in southern India. From there they studied the yearly motion of the Sun across the sky. It seems that they later moved to northern latitudes where they recognized the north-south motion of Sun and called it Uttarayana and Dakshinayana. It takes a year to complete this pendulum like movement of Sun in the sky. This movement is caused due to the motion of Earth around the Sun with a 23.5 degree tilt of Earth's axis with respect to Earth's orbit around Sun.
Valikhilyas used the motions of sun (circular motions and pendulum motions) to define a unit of time called a year.
Following the moon in night sky was relatively easy as it involved locating the position of Moon with respect to the prominent stars clearly visible in the night sky. These astronomers defined Nakshatras as lunar mansions, the places where Moon stays in its periodic travel across the sky. This was close to the original definition of a Nakshatra. Lunar astronomers were able to recognize the division of time called month as one revolution of moon in the sky. Lunar astronomers usually lived in higher latitudes. The kings who followed lunar astronomy later became known as the Lunar Dynasty kings. They lived at some point of time on the northern side of Saraswati, in Tibet. The Purus, the Bharatas and the Kurus were lunar dynasty kings. From their northern locations, they were aware of the motions of moon across the sky and also about the north-south motion of Sun (Uttarayana and Dakshinayana). When Lunar Astronomers came into contact with the Solar Astronomers, they synchronized their calender. They counted 12 revolutions of Moon as one year and added one additional month (Adhi-maasa) after some years to match up with the accuracy of a 365 day solar year followed by the Solar Astronomers.
The pendulum motion of the sun was noticed by these high-latitude astronomers. This helped them to define a year. But this was not as accurate as the 365 day year of the Solar Astronomers. Their year definition usually consisted of 360 days. This was due to the five day ambiguity in the motion of Sun when it reaches extreme north and south as it move across the sky. It was not possible to know if Sun really changed direction before 5 days are elapses. After coming to contact with Solar Astronomy the corrected their year definition.
Among the notable astronomers in the north were Vrihaspati (aka Brihaspati), Sukra and Vudha (aka Budha). Three planets are named after them, viz Jupiter (Vrihaspati), Venus (Sukra) and Mercury (Budha). Among other planets, Sani (Saturn) is named thus due to its slow motion and is not the name of any astronomer. Similarly Angaraka or Kuja (Mars) is named thus due to its coppery-red-color and is not the name of any astronomer.
Emergence of Yuga as a Unit of Time
Interaction of solar and lunar astronomers and the kings who followed either of them happened in the early periods of ancient Indian history. To study the motions of heavenly bodies they traveled to extreme north and south of ancient India. Thus the lunar astronomers of north traveled to south and the solar astronomers of south traveled to north and understood each others point of view. (It is possible that one of the reasons why sage Agastya traveled to southern India was to study the sky as seen from low latitudes). Their interaction gave a solid foundation to ancient Indian astronomy. Together they studied the motions of all the luminaries and also conceptualized the shadow planets (imaginary / conceptual points of significance in space) viz. Rahu and Ketu the ascending and descending nodes of lunar orbit.
It is then that they compiled all the ancient observations of the motion of Earth's axis with respect to the stars in the sky. They understood that this can be used to record time larger than a year. They found that it takes roughly 1000 years for the axis-projection to move from one Nakshatra to another, counting 27 Nakshatras. Remember, the axis of Earth was called Yuga (yoke). Similarly the imaginary junction of Earth axis with the starry-sky (an imaginary sphere surrounding the earth), viz. the axis-projection-point (the Celestial North Pole) on the sky (about which the stars seems to rotate every night) was also called a Yuga (junction / joint). The time it takes for this 'Yuga' (the axis or the axis-projection-point in the sky) to travel from one star to another was also called 'Yuga'. It was thus used as a unit of time. It was approximately equal to 1000 years.
Significance of the discovery of Yuga
The discovery of axial-precession (the rotation of the Earth's axis) and its usage in recording passage of time of the order of thousands of years was a great achievement of the ancient Indian astronomers. In order to understand this they should have an uninterrupted practice of astronomical observation for several centuries. Modern science calculates that the axial-precession of Earth takes 25,771.5 years. Ancient Indians calculated it as 27,000 years. This is pretty close! They did not use any high precision instrument to calculate this. The lack of high-precision instruments was compensated by patient observations for many thousand years. If we assume that the ancient Indians observed one full revolution of the axis, it would mean that they had a flourishing civilization with very good astronomers, for around 27,000 years! We can then reasonably assume that ancient Indian civilization is at least half of that period (13,000 years) old. That much long period of observations would be needed to conclude that the axis is traversing a circle and that the motion is periodic (not some random motion). Translated to modern time-frames, that would mean that our civilization started around 12,500 BC. This date is arrived at, by calculating backwards from 1000 AD. This is because, by 1000 AD (period of Bhaskara-II, 1100 AD), ancient Indian astronomy reached its current state. If we count backwards from the period of Aryabhata (500 AD or 2500 BC), then the start of the civilization would be at 13,000 BC or 16,000 BC.
The authors of Ramayana, Mahabharata and many Puranas had used astronomical observations and Yuga system of time recording to record important events mentioned in their works. They tried to record the positions of stars, axis-projection-point and planets as best as they can, whenever they were describing a crucial event, such as the birth of Rama, coronation of Rama, start and end of Kurukshetra War etc. These were currently used by modern analysts to date the events mentioned in Ramayana and Mahabharata. Using modern software tools (like the Planetarium software), and astronomical information contained in the ancient texts, researchers have made considerable progress in dating the period of Rama and Kurukshetra war. Thus a new science called archeo-astronomy is born. Earlier archeology and linguistics was the only science used to study the ancient world.
The celestial chariot of time
Coincidentally, the two circular regions around the poles of the celestial sphere (the sky) were compared to the wheels of a giant celestial-chariot, with the Earth as the body of the chariot and the axis of Earth as the axis (or axle) of the chariot. This system is called the celestial-chariot of time, in which the time-traveler (Kala-Purusha) is making his journey through time! Though a symbolic proposition, this conceptualization also led the ancient Indian astronomers to propose that Earth is not stationary but moving like a chariot. Stretching this concept further they also discovered that it is Earth that was moving in an orbit around Sun and not vice versa.
The wheels of this chariot of time were also known as the wheel of time (Kala-Chakra). This name was also given to the strip of sky along the equator of the celestial sphere. While the equatorial Kala-Chakra measured the passage of time in months (due to motion of moon) and in years (due to motion of sun), the polar Kala-Chakra measured the passage of time in 1000 year long Yugas (due to the motion of Earth's axis).
Variations in the definition of a Yuga
The naming of four consecutive Yugas as Krita (alias Kruta / Krta / Rta / Satya / Adi), Treta, Dwapara and Kali was a later invention. The four consecutive Yugas were together known as Maha-Yuga, Chatur-Yuga or the Yugas in plural. The division of Yugas into the ratio of 4:3:2:1 too was a later invention. The Chatur Yugas were thus 4000 years in length when calculated in the ratio of 1:1:1:1 and 10000 years in length when calculated using the ratio of 4:3:2:1 (Krita: 4000 years, Treta: 3000 years, Dwapara: 2000 years and Kali: 1000 years).
There was also a practice in which Yugas were counted starting from Kali. Thus Dwapara becomes second, Treta the third and Krita the fourth. This was sometimes counted in the forward direction of time and sometimes in the backward direction of time. When counted backwards, we still have Kali Yuga as the most recent Yuga with Dwapara preceding Kali, Treta preceding Dwapara and finally Krita as oldest Yuga of remote prehistory. This seems to be the correct interpretation. There are some who consider that after Krita, Treta, Dwapara and Kali, we have Kali coming again, then Dwapara, then Treta and then Krita in the remote future.
After Yuga became the unit of time, other periodic durations too were termed as Yugas. Thus one annual revolution of Sun viz. a year was termed as a Yuga. Hence we have the start of a year called Yugadi (Ugadi) in southern India. Similarly one revolution of planet Jupiter (Vrihaspati or Guru) too was considered as a Yuga. Kumbhamela is based on this. During the period of Aryabhata, he introduced longer Yugas, where he considered alignment of several luminary bodies to define a Yuga. Planetary alignment also is a kind of joining (Yuj : Yuga). Here the planets are joined in a line. Based on these definition duration of a single Yuga increased to several thousand years.
- How many Yugas are there?