The Sangam age people possessed the knowledge of planets and the zodiac. Opponents are of the opinion that horoscopy was introduced in India only in the Common Era. But a verse on Karikal Chola of the Sangam age shows that people were well aware of the zodiacal position of the planets. This king built the famous "Kallanai" – the Grand Anicut in stone across the river Kaveri.
The Wikipedia article mentions the period of this dam as 2nd century AD. That is wrong. This king preceded Silappadhikaram period as there is a mention of him in that epic. Silappadhikaram was written in the period of the Cheran king Senkuttuvan who was a contemporary of Gautami putra Satakarni (78- 102 CE). Therefore Karikalan's time goes before that time.
In two places in two different poems on this king, there comes a mention of his birth. In a text called "Porunar ARRup padai", the poet says that this king was not born in the normal course of the expected date of delivery. He continued to be in his mother's womb until such a time that combinations for rulership and acquisition of country were in place at the time of his birth. (1) This refers to the Raja yoga causing planetary positions at the time of birth. This is not a stray reference in Tamil literature. Such births are known as "Karuvile thiru udaiyavar" (possessed greatness in conception). Another king by name KocchengaNaan was also known to have had a delayed birth as to coincide with favorable planetary combinations at birth. (2)
This is comparable with a story on the birth of Indrajit, when the planets were supposed to have been ordered by Ravana to be in favorable locations. There is no way to check the veracity of this story, but the verse on Karikala shows that the people had observed an unfavourable combination in his expected birth time horoscope. The king was not born at that time and was born later when the Raja yoga combinations came into place. This could have pertained to moon and or some planetary position. Going by his life events, it could have been to do with Gaja kesari and / or Mahapurusha yoga. This king was compared with Skanda in this text for anger against enemies and deadly wars he launched on his enemies. (3) Perhaps Mars was not in favorable position at the expected date of his birth. It would have moved to exaltation or its own house at the actual time of his birth.
As if to confirm that this is not the poet's exaggerated praise of this king, another poem written on this king by another poet repeats the same idea. There the poet says that the king got this rulership by destiny while he was in his mother's womb (4). By this it is not meant that he got the kingdom by virtue of his birth or as birth right. This poem (Pattinappaalai) says that he had a difficult beginning. He did not have kingdom initially. He was imprisoned by his enemy at his young age. He managed to escape and then went on war with the enemy and won his land in his young age like a young Lion. He won many lands and expanded his kingdom, the details of which are told in these poems.
There are a couple of verses (in the few Sangam texts I have read. There may be similar verses in other Sangam texts that I have not yet read) on the Heliocentric movement of the planets. In an unexpected context, the poet makes a comparison of the vessels filled with food with the heliocentric formation of the solar system. All the vessels are made of gold and therefore shining well. The central vessel is huge and filled with the main food item. The other vessels which are smaller in size are filled with other food items and kept around the central main vessel. This looks like the Sun being surrounded by the planets! The poet says that the arrangement of food items in the shining golden vessels was like Sun surrounded by the planets. (5)
Similar description comes in another Sangam text called Pura Nanooru by the famous poetess Auvaiyaar. She describes the vessels filled with different food items as resembling planets! (6) Unless this kind of comparison is a common way of expression of the Royal feast in those days, this kind of similarity in expression could not have taken place in two different texts on two different kings of two different time periods. It would have taken a while for such an expression to come into common use. This certainly puts the knowledge of planets well before 3rd century BC in Tamil lands.
An unexpected and amazing information just preceding the above verse numbered (5) is that these food items were made as per the instructions given in the cookery book authored by none other than Bheema of Mahabharat fame! Bheema is known for his huge body, his strength and his expertise in wrestling. That he was good at cooking is known from his stint as a cook in Virata's kitchen when the Pandavas were in the last year of exile. But it is hardly known that he had authored a book on cooking. Only from the Sangam text we come to know that he had written such a book which was used by the people in Tamil lands. That shows that it must have existed in North India too, but was lost and forgotten after repeated invasions and Islamic holocaust in North India. Even the way the opponents have been dabbling with the authenticity of Vedic astrology shows how they are in the dark due to this loss of connectivity with the knowledge level that existed in the pre-Christian era. Fortunately Tamil lands were insulated from the happenings in rest of India until the British period. Until then, the connectivity with a continuing past had existed in Tamil lands which we are re-discovering now through literature.
The poet does not simply say that Bheema had authored it. He says "the famous one having the cache of arrows that burnt Khandava vana and a waist dress decorated with flower designs; the one born before him having a broad chest like Himavan wrote a cookery book having the intricate details; on the basis of which these dishes were made" (7) The poet could not have written this unless this was a fact because the entire narration is a factual commentary on what the poet encountered on the way until he reached this king, Nalliyak kOdan and was duly honored by him with food and gifts. The location of this king was somewhere near Ambur - Krishna giri in the Chennai – Bangalore Highway.
There are many other texts of Sangam age that tell about the planets and stars. The descriptions are not superficial or fictitious. For example, the star Karthikai is compared with flowers in many places. These comparisons show that they had known the star with its shape and its nature astrologically. An interesting comparison comes in a Sangam text called "Malai Padu Kadaam". This text is about the scenes in hill tracts of Western Ghats. The poet describes the flowers and says that the flower called "Musundai" blossomed in white like the glowing stars of Karthikai. (8)