Indian astronomy


has a long history in the Indian subcontinent, stretching from pre-historic to modern times. Some of the earliest roots of Indian astronomy can be dated to the period of Indus Valley civilisation 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.
Indian astronomy was influenced by Greek astronomy beginning in the 4th century BCE and through the early centuries of the Common Era, for example by the Yavanajataka and the Romaka Siddhanta, a Sanskrit translation of a Greek text disseminated from the 2nd century.
Indian astronomy flowered in the 5th–6th century, with Aryabhata, whose work, Aryabhatiya, represented the pinnacle of astronomical knowledge at the time. The Aryabhatiya is composed of four sections, covering topics such as units of time, methods for determining the positions of planets, the cause of day and night, and several other cosmological concepts. Later, Indian astronomy significantly influenced Muslim 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.
An identifiable native Indian astronomical tradition remained active throughout the medieval period and into the 16th or 17th century, especially within the Kerala school of astronomy and mathematics.

History

Some of the earliest forms of astronomy can be dated to the Indus Valley Civilisation or earlier. Some cosmological concepts are present in the Vedas, as are notions of the movement of heavenly bodies and the course of the year. The Rig Veda is one of the oldest pieces of Indian literature. Rig Veda 1-64-11 & 48 describes time as a wheel with 12 parts and 360 spokes, with a remainder of 5, making reference to the solar calendar. 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 Vedanga Jyotisha describes rules for tracking the motions of the Sun and the Moon for the purposes of ritual. According to the Vedanga Jyotisha, in a yuga or "era", there are 5 solar years, 67 lunar sidereal cycles, 1,830 days, 1,835 sidereal days and 62 synodic months.
Greek astronomical ideas began to enter India in the 4th century BCE following the conquests of Alexander the Great. By the early centuries of the Common Era, Indo-Greek influence on the astronomical tradition is visible, with texts such as the Yavanajataka and Romaka Siddhanta.
Later astronomers mention the existence of various siddhantas during this period, among them a text known as the
Surya Siddhanta. These were not fixed texts but rather an oral tradition of knowledge, and their content is not extant. The text today known as Surya Siddhanta dates to the Gupta period and was received by Aryabhata.
The classical era of Indian astronomy begins in the late Gupta era, in the 5th to 6th centuries.
The Pañcasiddhāntikā by Varāhamihira 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.

Calendars

The divisions of the year were on the basis of religious rites and seasons. The duration from mid March–mid May was taken to be spring, mid May–mid July: summer, mid July–mid September: rains, mid September–mid November: autumn, mid November–mid January: winter, mid January–mid March: the dews.
In the , the year begins with the winter solstice. Hindu calendars have several eras:
J. A. B. van Buitenen reports on the calendars in India:

Astronomers

  • Lagadha : The earliest astronomical textnamed Vedanga Jyotisha| details several astronomical attributes generally applied for timing social and religious events. The ' also details astronomical calculations, calendrical studies, and establishes rules for empirical observation. Since the texts written by 1200 BCE were largely religious compositions the ' 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. Ṛtús are also described as yugāṃśas. Tripathi holds that 'Twenty-seven constellations, eclipses, seven planets, and twelve signs of the zodiac were also known at that time.'
  • Āryabhaṭa : Āryabhaṭa was the author of the Āryabhatīya and the Āryabhaṭasiddhānta, which, according to Hayashi, "circulated mainly in the northwest of India and, through the Sasanian dynasty of Iran, had a profound influence on the development of Islamic astronomy. Its contents are preserved to some extent in the works of Varāhamihira, Bhāskara I, Brahmagupta, 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, Aryabhata, he suggested that the Earth was sphere, containing a circumference of 24,835 miles. 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.
  • Brahmagupta : Brāhmasphuṭasiddhānta dealt with both Indian mathematics and astronomy. Hayashi writes: "It was translated into Arabic in Baghdad about 771 and had a major impact on Islamic mathematics and astronomy". In Khandakhadyaka 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 the Indian concept of mathematics based astronomy into the Arab world. He also theorized that all bodies with mass are attracted to the Earth.
  • Varāhamihira : 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.
  • Bhāskara I : Authored the astronomical works Mahābhāskariya, Laghubhaskariya, and the Aryabhatiyabhashya a commentary on the Āryabhatīya written by Aryabhata. Hayashi 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, 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.
  • Lalla : Author of the Śiṣyadhīvṛddhida, which corrects several assumptions of Āryabhaṭa. The Śisyadhīvrddhida of Lalla itself is divided into two parts: Grahādhyāya and Golādhyāya. Grahādhyāya 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 parttitled Golādhyāya 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.
  • Śatānanda : Authored Bhāsvatī – estimated precession
  • Bhāskara II : Authored Siddhānta Shiromani| and ' 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 : Śrīpati was an astronomer and mathematician who followed the Brahmagupta school and authored the Siddhāntaśekhara in 20 chapters, thereby introducing several new concepts, including Moon's second inequality.
  • Mahendra Sūri : Mahendra Sūri authored the Yantra-rāja a Sanskrit work on the astrolabe, itself introduced in India during the reign of the 14th century Tughlaq dynasty ruler Firuz Shah Tughlaq. Sūri seems to have been a Jain astronomer in the service of Firuz Shah Tughluq. 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 Sūri also explained the Gnomon, equatorial co-ordinates, and elliptical co-ordinates. The works of Mahendra Sūri may have influenced later astronomers like Padmanābha author of the Yantra-rāja-adhikāra, the first chapter of his Yantra-kirṇāvali.
  • Makarandacarya : Author of the Makaranda sāriṇī
  • Parameshvara Nambudiri : Creator of the Drgganita or Drig system, Parameshvara belonged to the Kerala school of astronomy and mathematics. Parameshvara was a proponent of observational astronomy in medieval India and he himself had made a series of eclipse observations to verify the accuracy of the computational methods then in use. Based on his eclipse observations, Parameshvara proposed several corrections to the astronomical parameters which had been in use since the times of Aryabhata.
  • Nilakantha Somayaji : In 1500, Nilakantha 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. Nilakantha Somayaji, in his Āryabhaṭīyabhāṣya, a commentary on Āryabhaṭa's Āryabhaṭīya, 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 Jyotirmīmāṁsā stressing the necessity and importance of astronomical observations to obtain correct parameters for computations.
  • Daśabala : Author of Cintāmanṇisāraṇikā and the Karaṇakamalamārtaṇḍa.
  • Acyuta Piṣāraṭi : Sphuṭanirṇaya details an elliptical correction to existing notions. Sphuṭanirṇaya was later expanded to Rāśigolasphutānīti. 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, Acyuta Piṣāraṭi suggests improvements in methods of calculation of eclipses.
  • Dinakara : Author of a popular work, the Candrārkī with 33 verses to produce calendars, calculate lunar, solar, and star positions.
  • Mathurānātha Śarman : Author of Ravisiddhāntamañjarī or Sūryasiddhāntamañjarī
  • Pathani Samanta ' the last in chain of naked eye astronomers of India belonging to Siddhantic Era. Was born in Kahndapada, a feudatory state of Odisha. He studied various Siddhantas and found them to be erroneous as the planets were either not found at the right places or at right time. He made more studies, observed deeply and made several instruments to perfect his analysis of his observation. He composed his findings into a voluminous treatise name Siddhanta Darpan giving new formulaes to predict celestial occurrences. His almanac was adopted by the Jagannath Temple of Puri. He was awarded the title of Mahamahopadhyaya by the Viceroy of India Mr.Lansdowne and also a title Harichandan Mahapatra'' by Gajapati King of Puri. The instruments designed by him were for measurement of time and position of stellar bodies and were named Chapa Yantra, Mana Yantra, Golardha Yantra, Dhanu Yantra, Chakra Yantra, Swayambha Yantra, Gola Yantra etc. A postage stamp has been issued by the government of India in his honor.