Rishis Not Scientists Discovered Astronomy!
Indian astronomy has a long history stretching from pre-historic to modern times. Some of the earliest roots of Indian astronomy can be dated to the period of Indus Valley Civilization or earlier. Astronomy later developed as a discipline of Vedanga or one of the “auxiliary disciplines” associated with the study of the Vedas, dating 1500 BCE or older. The oldest known text is the Vedanga Jyotisha, dated to 1400–1200 BCE (with the extant form possibly from 700–600 BCE).
Indian astronomy flowered in the 5th–6th century, with Aryabhata, whose Aryabhatiya represented the pinnacle of astronomical knowledge at the time. Later the Indian astronomy significantly influenced Greek astronomy, Chinese astronomy, European astronomy, and others. Other astronomers of the classical era who further elaborated on Aryabhata’s work include Brahmagupta, Varahamihira and Lalla.
Some cosmological concepts are present in the Vedas, as are notions of the movement of heavenly bodies and the course of the year. As in other traditions, there is a close association of astronomy and religion during the early history of the science, astronomical observation being necessitated by spatial and temporal requirements of correct performance of religious ritual. Thus, the Shulba Sutras, texts dedicated to altar construction, discusses advanced mathematics and basic astronomy. Vedanga Jyotisha is another of the earliest known Indian texts on astronomy, it includes the details about the Sun, Moon, nakshatras, lunisolar calendar.
The classical era of Indian astronomy begins in the late Gupta era, in the 5th to 6th centuries. The Pañcasiddhāntikā by Varāhamihira (505 CE) approximates the method for determination of the meridian direction from any three positions of the shadow using a gnomon. By the time of Aryabhata the motion of planets was treated to be elliptical rather than circular. Other topics included definitions of different units of time, eccentric models of planetary motion, epicyclic models of planetary motion, and planetary longitude corrections for various terrestrial locations.
The divisions of the year were on the basis of religious rites and seasons (
Rtu). The duration from mid March—mid May was taken to be spring (vasanta), mid May—mid July: summer (grishma), mid July—mid September: rains (varsha), mid September—mid November: autumn (sharad), mid November—mid January: winter (hemanta), mid January—mid March: the dews (shishir).
In the Vedānga Jyotiṣa, the year begins with the winter solstice.
Hindu calendars have several eras: The Hindu calendar, counting from the start of the Kali Yuga, has its epoch on 18 February 3102 BCE Julian (23 January 3102 BCE Gregorian). The Vikrama Samvat calendar, introduced about the 12th century, counts from 56–57 BCE. The “Saka Era”, used in some Hindu calendars and in the Indian national calendar, has its epoch near the vernal equinox of year 78. The Saptarshi calendar traditionally has its epoch at 3076 BCE. J.A.B. van Buitenen (2008) reports on the calendars in India: The oldest system, in many respects the basis of the classical one, is known from texts of about 1000 BCE.
It divides an approximate solar year of 360 days into 12 lunar months of 27 (according to the early Vedic text Taittirīya Saṃhitā 18.104.22.168–3) or 28 (according to the Atharvaveda, the fourth of the Vedas, 19.7.1.) days. The resulting discrepancy was resolved by the intercalation of a leap month every 60 months.
Time was reckoned by the position marked off in constellations on the ecliptic in which the Moon rises daily in the course of one lunation (the period from New Moon to New Moon) and the Sun rises monthly in the course of one year.
These constellations (nakṣatra) each measure an arc of 13° 20′ of the ecliptic circle. The positions of the Moon were directly observable, and those of the Sun inferred from the Moon’s position at Full Moon, when the Sun is on the opposite side of the Moon. The position of the Sun at midnight was calculated from the nakṣatra that culminated on the meridian at that time, the Sun then being in opposition to that nakṣatra.
Rishis- Notable Astronomers.
|1st millennium BCE
|The earliest astronomical text—named Vedānga Jyotiṣa details several astronomical attributes generally applied for timing social and religious events. The Vedānga Jyotiṣa also details astronomical calculations, calendrical studies, and establishes rules for empirical observation. Since the texts written by 1200 BCE were largely religious compositions the Vedānga Jyotiṣa has connections with Indian astrology and details several important aspects of the time and seasons, including lunar months, solar months, and their adjustment by a lunar leap month of Adhimāsa. Ritus are also described as ((yugams)). Tripathi (2008) holds that ‘ Twenty-seven constellations, eclipses, seven planets, and twelve signs of the zodiac were also known at that time.’
|Aryabhata was the author of the Āryabhatīya and the Aryabhatasiddhanta, which, according to Hayashi (2008): ‘circulated mainly in the northwest of India and, through the Sāsānian dynasty (224–651) of Iran, had a profound influence on the development of Islamic astronomy. Its contents are preserved to some extent in the works of Varahamihira (flourished c. 550), Bhaskara I (flourished c. 629), Brahmagupta (598–c. 665), and others. It is one of the earliest astronomical works to assign the start of each day to midnight.’ Aryabhata explicitly mentioned that the Earth rotates about its axis, thereby causing what appears to be an apparent westward motion of the stars. In his book, Aryabhatiya, he suggested that the Earth was sphere, containing a circumference of 24,835 miles (39,967 km). Aryabhata also mentioned that reflected sunlight is the cause behind the shining of the Moon. Aryabhata’s followers were particularly strong in South India, where his principles of the diurnal rotation of the Earth, among others, were followed and a number of secondary works were based on them.
|Brahmasphuta-siddhanta (Correctly Established Doctrine of Brahma, 628 CE) dealt with both Indian mathematics and astronomy. Hayashi (2008) writes: ‘It was translated into Arabic in Baghdad about 771 and had a major impact on Islamic mathematics and astronomy.’ In Khandakhadyaka (A Piece Eatable, 665 CE) Brahmagupta reinforced Aryabhata’s idea of another day beginning at midnight.Brahmagupta also calculated the instantaneous motion of a planet, gave correct equations for parallax, and some information related to the computation of eclipses. His works introduced Indian concept of mathematics based astronomy into the Arab world. He also theorized that all bodies with mass are attracted to the earth.
|Varāhamihira was an astronomer and mathematician who studied and Indian astronomy as well as the many principles of Greek, Egyptian, and Roman astronomical sciences. His Pañcasiddhāntikā is a treatise and compendium drawing from several knowledge systems.
|Authored the astronomical works Mahabhaskariya (Great Book of Bhaskara), Laghubhaskariya (Small Book of Bhaskara), and the Aryabhatiyabhashya (629 CE)—a commentary on the Āryabhatīya written by Aryabhata. Hayashi (2008) writes ‘Planetary longitudes, heliacal rising and setting of the planets, conjunctions among the planets and stars, solar and lunar eclipses, and the phases of the Moon are among the topics Bhāskara discusses in his astronomical treatises.’ Bhāskara I’s works were followed by Vateśvara (880 CE), who in his eight chapter Vateśvarasiddhānta devised methods for determining the parallax in longitude directly, the motion of the equinoxes and the solstices, and the quadrant of the sun at any given time.
|8th century CE
|Author of the Śisyadhīvrddhida (Treatise Which Expands the Intellect of Students), which corrects several assumptions of Āryabhata. The Śisyadhīvrddhida of Lalla itself is divided into two parts: Grahādhyāya and Golādhyāya. Grahādhyāya (Chapter I-XIII) deals with planetary calculations, determination of the mean and true planets, three problems pertaining to diurnal motion of Earth, eclipses, rising and setting of the planets, the various cusps of the Moon, planetary and astral conjunctions, and complementary situations of the Sun and the Moon. The second part—titled Golādhyāya (chapter XIV–XXII)—deals with graphical representation of planetary motion, astronomical instruments, spherics, and emphasizes on corrections and rejection of flawed principles. Lalla shows influence of Āryabhata, Brahmagupta, and Bhāskara I. His works were followed by later astronomers Śrīpati, Vateśvara, and Bhāskara II. Lalla also authored the Siddhāntatilaka.
|Authored Siddhāntaśiromaṇi (Head Jewel of Accuracy) and Karaṇakutūhala (Calculation of Astronomical Wonders) and reported on his observations of planetary positions, conjunctions, eclipses, cosmography, geography, mathematics, and astronomical equipment used in his research at the observatory in Ujjain, which he headed.
|Śrīpati was an astronomer and mathematician who followed the Brhmagupta school and authored the Siddhāntaśekhara (The Crest of Established Doctrines) in 20 chapters, thereby introducing several new concepts, including Moon’s second inequality.
|14th century CE
|Mahendra Suri authored the Yantra-rāja (The King of Instruments, written in 1370 CE)—a Sanskrit work on the astrolabe, itself introduced in India. The 182 verse Yantra-rāja mentions the astrolabe from the first chapter onwards, and also presents a fundamental formula along with a numerical table for drawing an astrolabe although the proof itself has not been detailed. Longitudes of 32 stars as well as their latitudes have also been mentioned. Mahendra Suri also explained the Gnomon, equatorial co-ordinates, and elliptical co-ordinates. The works of Mahendra Suri may have influenced later astronomers like Padmanābha (1423 CE)—author of the Yantra-rāja-adhikāra, the first chapter of his Yantra-kirnāvali.
|In 1500, Nilakanthan Somayaji of the Kerala school of astronomy and mathematics, in his Tantrasangraha, revised Aryabhata’s model for the planets Mercury and Venus. His equation of the centre for these planets remained the most accurate until the time of Johannes Kepler in the 17th century. Nilakanthan Somayaji, in his Aryabhatiyabhasya, a commentary on Aryabhata’s Aryabhatiya, developed his own computational system for a partially heliocentric planetary model, in which Mercury, Venus, Mars, Jupiter and Saturn orbit the Sun, which in turn orbits the Earth, similar to the Tychonic system later proposed by Tycho Brahe in the late 16th century. Nilakantha’s system, however, was mathematically more efficient than the Tychonic system, due to correctly taking into account the equation of the centre and latitudinal motion of Mercury and Venus. Most astronomers of the Kerala school of astronomy and mathematics who followed him accepted his planetary model. He also authored a treatise titled Jyotirmimamsa stressing the necessity and importance of astronomical observations to obtain correct parameters for computations.
|Sphutanirnaya (Determination of True Planets) details an elliptical correction to existing notions. Sphutanirnaya was later expanded to Rāśigolasphutānīti (True Longitude Computation of the Sphere of the Zodiac). Another work, Karanottama deals with eclipses, complementary relationship between the Sun and the Moon, and ‘the derivation of the mean and true planets’. In Uparāgakriyākrama (Method of Computing Eclipses), Acyuta Pisārati suggests improvements in methods of calculation of eclipses.
Among the devices used for astronomy was gnomon, known as Sanku, in which the shadow of a vertical rod is applied on a horizontal plane in order to ascertain the cardinal directions, the latitude of the point of observation, and the time of observation.
This device finds mention in the works of Varāhamihira, Āryabhata, Bhāskara, Brahmagupta, among others.The Cross-staff, known as Yasti-yantra, was used by the time of Bhaskara II (1114–1185 CE). This device could vary from a simple stick to V-shaped staffs designed specifically for determining angles with the help of a calibrated scale.
The clepsydra (Ghatī-yantra) was used in India for astronomical purposes until recent times. Ōhashi (2008) notes that: “Several astronomers also described water-driven instruments such as the model of fighting sheep.”The armillary sphere was used for observation in India since early times, and finds mention in the works of Āryabhata (476 CE).
The Goladīpikā—a detailed treatise dealing with globes and the armillary sphere was composed between 1380–1460 CE by Parameśvara.
An instrument invented by the mathematician and astronomer Bhaskara II (1114–1185 CE) consisted of a rectangular board with a pin and an index arm. This device—called the Phalaka-yantra—was used to determine time from the sun’s altitude.
The Kapālayantra was an equatorial sundial instrument used to determine the sun’s azimuth. Kartarī-yantra combined two semicircular board instruments to give rise to a ‘scissors instrument’. Introduced from the Islamic world and first finding mention in the works of Mahendra Sūri—the court astronomer of Firuz Shah Tughluq (1309–1388 CE)—the astrolabe was further mentioned by Padmanābha (1423 CE) and Rāmacandra (1428 CE) as its use grew in India. Invented by Padmanābha, a nocturnal polar rotation instrument consisted of a rectangular board with a slit and a set of pointers with concentric graduated circles.
Time and other astronomical quantities could be calculated by adjusting the slit to the directions of α and β Ursa Minor.
Its backside was made as a quadrant with a plumb and an index arm. Thirty parallel lines were drawn inside the quadrant, and trigonometrical calculations were done graphically. After determining the sun’s altitude with the help of the plumb, time was calculated graphically with the help of the index arm.