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 Vedas: An Introduction to Hinduism's Sacred Texts, Roshen Dalal, p. 188 The oldest known text is the Vedanga Jyotisha, dated to 1400–1200 BCE (with the extant form possibly from 700 to 600 BCE).
Indian astronomy was influenced by Greek astronomy beginning in the 4th century BCEHighlights of Astronomy, Volume 11B: As presented at the XXIIIrd General Assembly of the IAU, 1997. Johannes Andersen Springer, 31 January 1999 – Science – 616 pages. p. 721 Babylon to Voyager and Beyond: A History of Planetary Astronomy. David Leverington. Cambridge University Press, 29 May 2010 – Science – 568 pages. p. 41 The History and Practice of Ancient Astronomy. James Evans. Oxford University Press, 1 October 1998 – History – 496 pages. p.?393 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.Foreign Impact on Indian Life and Culture (c. 326 B.C. to c. 300 A.D.). Satyendra Nath Naskar. Abhinav Publications, 1 January 1996 – History – 253 pages. pp. 56–57
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."Star Maps: History, Artistry, and Cartography", p. 17, by Nick Kanas, 2012 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 Rigveda 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 (days), 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.Ōhashi (1993) 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 (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.Hayashi (2008), Aryabhata I 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 (Ṛtú).J.A.B. van Buitenen (2008) 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 (sharada), mid November–mid January: winter (hemanta), mid January–mid March: the dews (shishira).
In the , the year begins with the winter solstice.Bryant (2001), 253 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 Vikram Samvat calendar, introduced about the 12th century, counts from 56 to 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 Saptarishi calendar traditionally has its epoch at 3076 BCE.See A. Cunningham (1883), A Book of Indian Eras.
J. A. B. van Buitenen (2008) reports on the calendars in India:
Astronomers Lagadha (1st millennium BCE): The earliest astronomical textnamed 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.Subbaarayappa (1989) 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.Tripathi (2008) Ṛtús are also described as yugāṃśas (or parts of the yuga, i.e. conjunction cycle). Tripathi (2008) holds that 'Twenty-seven constellations, eclipses, seven planets, and twelve signs of the zodiac were also known at that time.' Āryabhaṭa (476–550 CE): Āryabhaṭa was the author of the Āryabhatīya and the Āryabhaṭasiddhānta, which, according to Hayashi (2008), "circulated mainly in the northwest of India and, through the Sasanian 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 Varāhamihira (flourished c. 550), Bhāskara I (flourished c. 629), Brahmagupta (598c. 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, Āryabhatīya, 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. Brahmagupta (598–668 CE): Brāhmasphuṭasiddhānta (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".Hayashi (2008), Brahmagupta 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 the Indian concept of mathematics based astronomy into the Arab world. He also theorized that all bodies with mass are attracted to the Earth.Brahmagupta, Brahmasphutasiddhanta (628) (cf. Al-Biruni (1030), Indica) Varāhamihira (505 CE): 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.Varāhamihira. Encyclopædia Britannica (2008) Bhāskara I (629 CE): Authored the astronomical works Mahābhāskariya (Great Book of Bhāskara), 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.'Hayashi (2008), Bhaskara I 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. Lalla (8th century CE): Author of the Śiṣyadhīvṛddhida (Treatise Which Expands the Intellect of Students), which corrects several assumptions of Āryabhaṭa. 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.Sarma (2008), Lalla The second parttitled 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. Śatānanda (1068–1099 CE): Authored Bhāsvatī (1099) – estimated precession Bhāskara II (1114 CE): Authored (Head Jewel of Accuracy) and (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 headedHayashi (2008), Bhaskara II Śrīpati (1045 CE): Śrīpati was an astronomer and mathematician who followed the Brahmagupta school and authored the Siddhāntaśekhara (The Crest of Established Doctrines) in 20 chapters, thereby introducing several new concepts, including Moon's second inequality.Hayashi (2008), Shripati