Vrddha Garga was the earliest reference to precession of equinoxes?

Though the lunar time between two successive full moons is 29.53059 solar days, the time taken for moon to go round the earth (sidereal month) is 27.32166 days. Moon also has an oscillatory motion crossing the ecliptic. The moon anomalistic motion and nodal motion have periods are 27.55545 and 27.21222 days for a revolution around earth. The reason for time between full moons being higher than sidereal month is because, the moon has to go around the earth by more than a revolution (nearly 390 degrees) to keep with earth which moves forward in its trajectory around sun. The Chandramaana lunar calendar system keeps a natural cyclic count of days using two Moon based properties described below.

First property is that moon functions as an astronomical day count clock in which Moon is the pointer and the stars are numerals in the sky pointed to by moon each day of the lunar month. The astronomers of Vedic period identified this approximate 13 degree movement of the moon between successive days and named the 27/28 stars pointed to by moon on a daily basis over a rotation as 27/28 nakshatra's, corresponding to little less than a lunar month. Thus a Nakshatra shift corresponds to moon traverse over approximately one solar day.

The second property is the size of fractional moon exposure to sun can indicate a day count and is defined as a moon day or thiti. Thirty thiti's are defined in a lunar month, each thiti being smaller than a solar day. Fifteen are identified as Shukla paksha or ascending fortnight and next fifteen are called krishna paksha or descending fortnight.

This system of day count calendar keeping, is traceable to Veda's. Veda's, which are perhaps the oldest original documentation of knowledge any where in the world, still in their original shape and language. A study of theVeda's, Brahmana's, and Aaranyaka's point exclusive use of a lunar pointer as the primary calendar in the Vedicperiods. Pournamsya, a time at which earth, sun, moon are aligned is a time of singularity used for religious purposes and formed the unit of half a month and is used in Rigveda. The Vedas also refer to solar events such as Aayanas, and Vishuwat-Sankramana's as solar singular events. Ayana means Solstices when apparent North-South movement of Sun reverses, usually occurring on June 21 and Dec 22. Vishuwat means equal or the spring and fall equinox’s when daytime is equal to nighttime, usually occurring on March 21 and Sep 21. There are vedic references to solar singularities with corresponding solar/lunar pointed star locations.

The six-season definition is unique to vedic system and is not found in any other recorded culture or system. These seasons are, Vasanta, Geeshma, Varsha, Sharad, Himavanta and Shishira each season being about two moon cycles. It is in Taittareeya Samhita (Krishna Yajurveda) and in Atharva samhita 19th kaanda /7th Sootrathat an explicit first definition and identification of the twenty- seven(28) Nakshatra’s is available (Refs, 1 and 2). It should be noted that the concept of Zodiac/Raashi is not even hinted in any vedic texts of the old period.

The table below provides a list of the twenty-seven stars from Taittareeya Samhita and Krishna Yajurveda 4thKaanda 4th Prashna of Andhra School. Similar list is referred to in Atharvaveda, 19th kaanda/7th Sookta. It differs from the Yajurveda list in that twenty eight stars are listed. In 19^th Kaanda/8^th sooktha twenty eight(ashtha vimshaani) nakshatras are declared. The nakshatra not explicitly used in Jyotishya and in yajurvedais named Abhijit. The taiaareeya brahmana (third Ashtaka) derived from yajurveda again lists 28 nakshatrasincluding Abhijit. It is referred to in Athrvana veda. The author or Drashtaara of Atharva veda sookta is Gaargya Rishi.

The confusion about 27/28 Nakshatras can be analyzed as follows. The 27.3 days taken by moon for visiting the same star can be rounded to either 27 or 28. Each of these integers represents a nakshatra or a daily star. It is possible that initially 28 nakshatras were proposed and defined to represent every day. This is evident fromGargya’s Nakshtara sooktha. Subsequently many years later when Jyotishya was taking a more formal and mathematical shape, 27 integer identities were perhaps found to be more reasonable and accurate. Hence one of the original 28 nakshatras had to be deleted. This could not be done easily as the vedas are considered to be ‘apourusheya’ and no liberties were allowed. Hence perhaps Abhijit, was declared to be an imaginary nakshatrameant only for phala.(ref 10).

The Table below lists names of Nakshatras, the deity to which Nakshatra is dedicated to, and alternate names.Ashwini and Bharani are listed as last two Nakshatras. Note that the list starts from Krittika and not fromAshwini as is currently used in Jyotishya Shaastra (Ref 3). The time at which Rishi Gargya documented the list of nakshatra's in Atharvana Veda is at least circa 2400 BC, as analyzed in appendix I. The appendix also dates the Jyotishya Shaastra as having been brought in to the present form around circa 400 BC.

The lunar calendar was in universal and secular use in ancient Bhaarata. Historical events used lunar calendar for dating all events. It is well known that Gautama Buddha was born, achieved his enlightenment and died on full moon day with the full moon pointing to Vishakha Nakshatra. The twelve months were named after the stars at which full moon occurs and these are Chaitra, Vaishakha, Jyeshta, Ashaada, Sharavna, Bhadrapda, Ashwija, Kaartika, Margashira, Pushya, Maagha, Phalguna. Typically alternate stars with some skips refer to month names and hence accommodate 27 stars corresponding to nearly 360 degrees motion of Sun in a solar year.The first question that arises is whether a 'Nakshatra' corresponds to one single star entity or a group of stars in the sky. Bharateeya Jyotishya shaastra states that each Nakshatra name corresponds to a group of stars called star mansions or Asterisms. The concept is that Chandra or Moon visits these mansions in his trajectory around earth. It is very possible that at the inception of daily star concept during the early vedic period, a Nakshatra may have been a specific single star. Nakshatra positions may have been rationalized in later days to mansions or groups of stars for purposes of mathematical averaging to be exactly 13.333 degrees apart required in Jyotishya. The table above also shows the number of stars, accepted by Jyotishya shaastra, constituting the specific Nakshatra.

The European view (originally from Chaldian and Kassarian cultures of Middle East and from Egypt), propagated by Greek philosophers, of the night sky and the star system ran in a different direction in ancient times in that Sun was considered as the pointer to skies. In contrast, the moon is considered to be the primary pointer fromvedic astronomical point of view. Star groups pointed to by the sun were defined as Zodiacs representing clusters of stars forming shapes of animals and figures. Zodiacs were named after animal shapes or Greek mythological figures. The twelve months were named and represented Zodiac groups, which had an animal form through which the Sun passes.

If we compare the names of Bhaarateeya Rashis and Zodiacs and Weekdays, are same but for the language as shown in table below. It is inconceivable that two non-communicating societies can evolve name systems, which are translations of each other in a linguistic sense. Clearly, one of the two parties influenced the other.

The Vedas and other older texts do not refer to weekdays named after Graha's or Planets or to Raashis. TheGrahas referred to in Veda's are Surya, Chandra, Brihaspati, Shukra, Budha, shani, Kuja, Rahu, Ketu. They extensively refer to Nakshatra month names and moon pointing at different Nakshatra's for various purposes. Therefore it appears likely that the Bharateeya cosmological system interacted with the European solar calendar and gradually the Jyotishya shaastra was modified to the present form, as we know now. Sun based concepts ofRashi, weekdays were invoked in to Jyotishya. This could have occurred, perhaps through contact with Yavanas (Greek's) as there is considerable evidence of Greek and Bharateeya interaction during period before Chandra Gupta. Appendix provides astronomical time markers which confirm the origins of Jyotishya Shaastra in present form to circa 400 BC. Without acceptance of this interaction, it is difficult to explain why the twelve Zodiacs of the European star system are translations of the Nakshatra-Rashi defined in Jyotishya.

It is worth while looking at the some Bharateeya astronomers of a more recent time of 300-500 AD. They areAryabhata, Varaha Mihira, Brahma Gupta. These astronomers were aware of the vedic astronomy and made new and unique contributions. Specifically Aryabhata made contributions to Spherical geometry, a part of understanding the earth as a globe. Varaha Mihira's contributions include pesently used Soorya Siddhanta, (He refers to nine types of time keeping and calenders) and the fact that he proposed Prime Meridian through Ujjainin Madhya Pradesh. He knew of Earth's Precession and called it as ayanaamsha. Brahma Gupta made contributions to Arcsin in Trigonometry. Aryabhata had estimated the beginning of kaliyuga as 3102 BC. He stated that when he was 26, sixty of the 60-year cycles were completed after start of kaliyuga. Varahmihiramade an estimate of 2526 before start of Shaka varsha for Mahabharata's Yudhishtira. Texts from that period likeYavana Jataka, Romaka Siddahnta provide evidence of understanding of European astronomical works.

The Chandramaana Lunar scale has 27 daily and twelve month name definitions. While amalgamating the solar calibrations of zodiacs in to Lunar calibrations of Nakshatra's, the issue of translating 27 Nakshatras in a revolution to 12 Rashis was solved in Jyotishya Shaastra by treating 1/4 of a Nakshatra as a unit making Nine quarters of Nakshatra as one Raashi.

Chinese have had a long tradition of astronomical observations. They appear to have used, Sun, Moon and Jupiter as pointers which included zodiac division in to 28 segments as early as 1200 BC. The 28 segmental division is somewhat similar to vedic system. The starting position of the 28 zodiacs was in Libra (near Swati orVishakha). That appears to rule out Chinese interaction with Vedic culture.

The concept of animal shaped zodiac representing 10-12 zodiacs per year is attributed to Chaldean and Akkadian cultures of Messapotamia. Egyptian Dendera Palnisphere, presently in France, which has been dated to about 1800 BC shows the twelve zodiacs (Ref 4). The earliest traceable documentation from European sources is by Ptolemy in 130 AD, who lived in Alexandria in current Egypt. He compiled data from many centuries of European knowledge before him and he used Hipparchus's astronomical observations (nearly 300 year older than Ptolemy) for many of his observations. The observation of Earth's Precession is attributed to Ptolemy and Hipparchus, and is a major astronomical observational finding. Ptolemy’s works comes down to modern days via Arab astronomers who called his work `Al magist’. In this Ptolemy, refers to 48 constellations in the skies. He used the Egyptian year and month names, which were well advanced and similar to Julian system. Interaction of middle eastern/European astronomical knowledge with Bharateeya knowledge clearly must have happened, much before Ptolemy when many Greeks were in Bhaarat. Ptolemy's zodiac boundaries are different from present zodiac boundaries of same name. The Arab astronomers used Ptolemy's data base and made a thorough study of the skies after Ptolemy and many individual stars were named by them in post Ptolemy centuries. These names have been widely accepted and used.

During many centuries after Ptolemy's time, number of changes have occurred in constellation definitions and boundaries. In 17th century, Bayer systematically named stars using three parameters, first to give star a serial number in its constellation, and second to assign a Greek alphabet representative of the brightness and third to refer to constellation where star is. Therefore a should always be the brightest star of the constellation followed by b, etc. Flamsteed numbers are another catalog of stars from same era. The presently accepted 88 Zodiac definition was frozen in 1932 by International Astronomical Union and stars are named by Bayer's system. This came about because of the meriad constellation names and boundaries that were being floated at that time.

Since the profound beginnings of modern astronomy by Kepler, Galileo, Newton and their astonishing advances in recent times by Hubble and others, extensive and detailed catalogs of all bodies in skies have been made. Optical and other electromagnetic wavelength telescopes have been used to study all objects in the skies. The modern astronomers have a very precise understanding of major and minor planetary motion, binary stars, Messier objects, Comets, and even man made objects in sky. Modern astronomical science has catalogs all the visible stars. The identification currently extensively used in modern astronomy is the HD number standing for Henry Draper Classifications, and SAO number standing for Smithsonian Astronomical Observatory catalog number. There are star catalogs from Germany, France, and Britain.

Most of the European style analysis of astronomical references in veda's (starting from German and British writers of 19 and early 20th century) have always suggested that the vedic text astronomical observations were generally primitive and any non-primitive elements were some how derived from Messapotamian/Akkadian/Chaldean origins. These analyses trivialize any significant original observations in theVeda's. This bias has been brought out be David Frawley succinctly in his work (ref-8).

Star brightness has been numerically expressed since Hipparchus in 150 BC. The scale presently used to measure brightness of objects is an inverse geometrical scale with brightness of sun at -26. With such a bright object, flooding atmosphere, other objects in sky are only visible to normal human eyes during night when sun is not visible. Full moon has a brightness of -12. Venus at its brightest has a brightness of -3. A change of brightness by 2.56 refers to a change of brightness by factor of two. The brightest star is Sirius, which has a brightness of -1.5. On a clear dark night (without moon), the dullest object that can be seen by healthy human eye is considered to be +6.

The following principles and assumptions can perhaps be used as the basis for establishing identity ofBharateeya Nakshatras in this article.

*Nakshatra named by people at Vedic time, must have been visible to naked eye and hence must be brighter than +5, based on brightness definitions.

*Moon is said to visit the Nakshatra or star mansions. Moon traverse plane is inclined to sun motion plane and hence over a period of time, the moon trajectories form a band. Let us call it as the moon traverse band. It is typically 5 degrees around ecliptic. Hence for any star or group of stars to qualify as a Nakshatra, it must be within the moon traverse band or outside not exceeding a few moon diameters. One Moon diameter is about 0.6 degree as seen from earth.

* The Nakshatras should be about 13.33 degrees apart or to 1/27 of 360.

* It is also necessary that they belong to the Raashi's or twelve Zodiacs. There are 88 officially identified zodiacs in the sky, moon traverse band passes only through 12. It should be noted that the Raashi or zodiac boundaries may vary from past definitions of 2400 years ago when possibly the Zodiac concepts were amalgamated in toJyotishya.

*In Bharat, the traditional Panchangas/almanacs provide chandramana details including the beginning and end of visit of moon to 27 Nakshatras time to within few minutes of accuracy for every day of the year. Such almanacs are used even today for religious purposes. This data has to correlate with our identification in that moon must be near the star.

Implicit in these rules is the assumption that Jyotishya Shaastra experts of circa 400 BC carried forward the knowledge and identity of the Nakshatras correctly from vedic period accurately in correlating nakshatra's toRaashi's at that time. It is this interrelation of Nakshatras and Raashi's that permit us to identify what the vedictime names of stars were. The effect of natural motion of stars is assumed to be insignificant, but accounting for precession or Ayanamsha is necessary.

An astronomical computer software, LOADSTAR PRO GS has been used to identify the traditional Bharateeya Nakshatras and their equivalents based on the rules and assumptions declared above.

Figure 1 shows the picture of Mesha or Aries group of Stars in the sky. Clearly, the Moon Band does not touch the Mesha Raashi or Aries as presently identified, but is within about 5 degrees of the band. Figure 1 shows fourNakshatras viz., Revati from Meena Raashi, Ashwini, Bharani, and Krittika.

Ashwini Nakshatra is defined in Bharateeya Jyotishya as group of three stars. A study of the figure 1 suggests that the best candidates for this group are as shown in table below based on brightness point of view, location with reference to moon traverse band and distance from previous Nakshatra.

The month of Ashwija (usually October in the Gregorian System) is named after Ashwini and at the full moon ofAshwija Moon is near Ashwini Nakshatra. If a single star has to be identified as representing Ashwini Nakshatra, Best candidate is 13 a Aries / SAO-75151/HD-12929/Hamal.

The Bharani Nakshatra is defined as a group of three stars. Brightest can be identified as HD17573 and SAO75596. The following table provides candidates which qualify as Bharani Nakshatra from brightness point of view, location with reference to moon traverse band and distance from previous Nakshatra.

If a single star has to be identified as representing Bharani Nakshatra, best candidate is 41-Aries/SAO-75596/HD-17573.

Krittika Nakshatra is defined as a set of six stars. Bharateeya tradition has it that Kaartikeya, is surrounded by five Apsaras. This set of stars is identified by classical European system as Plaeidis. Brightest amongst them is called Alcyone by Arabs. The following table provides the candidates of stars for Krittika Nakshatra or Lunar mansion from brightness point of view, location with reference to moon traverse band and distance from previousNakshatra.

If a single star has to be identified as representing Krittika Nakshatra, best candidate is 25hAries/SAO-76199/HD-23630/ AlCyone.

Krittika is also the name of the Chandramana month Kaartika. On the full moon day of Kaartika, the moon is near Krittika Nakshatra. In the Raashi/Nakshatra translation, both the Ashwini/Bharani belong to Mesha Raashi. The Krittika is considered as 1/4 a part of Mesha (Aries) and 3/4 a part of Vrishbha (Taurus).

Arundhati Nakshatra (though not a part of the 27 day pointing stars) is near the Krittitka. It is said to be the eighth star in the cluster Krittika(Ref-2).

The Ashwini/Bharani Nakshatras stars are separated by 50 minutes of time or about 12.5 degrees (E-W), whileBharani and Krittika are separated by about 55 minutes corresponding to about 13.75 degrees (E-W). Both these gaps are near the ideal 13.33 degrees E-W gap between stars.