Indian astronomy

Astronomy has a long and fascinating history in the Indian subcontinent, dating back to pre-historic times. One of the earliest known texts, the Vedanga Jyotisha, comes from around 1400–1200 BCE, showing that ancient Indians carefully studied the stars and planets. This knowledge was part of Vedanga, a group of subjects that helped people understand the Vedas, important religious texts.

Later, Indian astronomy grew by sharing ideas with other cultures. After meeting with Greek astronomy in the 4th century BCE, Indian scholars used new methods and ideas, like those in the Yavanajataka and the Romaka Siddhanta. This helped them improve their understanding of the universe.

The biggest breakthrough came in the 5th–6th century with a brilliant astronomer named Aryabhata. His book, the Aryabhatiya, explained many important ideas about time, the movement of planets, and why we have day and night. After Aryabhata, other great thinkers like Brahmagupta, Varahamihira, and Lalla added even more to this wonderful science. Their work later helped astronomers in Muslim astronomy, China, and Europe learn amazing new things about the stars and planets.

History

Some of the earliest forms of astronomy can be dated to the Indus Valley Civilisation or earlier. Ideas about the stars and the movement of the Sun and Moon appear in ancient texts such as the Vedas. These early ideas were closely linked to religion, helping people know the right times for ceremonies.

Later, new ideas from Greece came into India after the conquests of Alexander the Great. Famous Indian astronomers like Aryabhata made important discoveries about how the planets move. They used tools like a gnomon to study the stars and developed clever ways to calculate time and positions.

Calendars

Further information: Hindu calendar

See also: Astronomical basis of the Hindu calendar

In ancient India, people divided the year based on seasons and religious traditions. Each season had its own name, like spring, summer, and winter. The Hindu calendar has several important starting points, or "eras," including one that begins from the start of the Kali Yuga, a very old time period. These calendars help people understand the passing of time and plan important events.

Astronomers

• Lagadha (1st millennium BCE): One of the earliest Indian astronomers, Lagadha wrote the Vedānga Jyotiṣa, which provided rules for timing social and religious events. This text also included details about lunar and solar months and the seasons.

• Āryabhaṭa (476–550 CE): Āryabhaṭa wrote important books about astronomy, including the Āryabhatīya. He was one of the first to say that the Earth spins, causing the stars to appear to move. He also described the Moon’s shine as coming from reflected sunlight.

• Brahmagupta (598–668 CE): Brahmagupta wrote about both math and astronomy. His book, Brāhmasphuṭasiddhānta, included ideas about planets’ movements and eclipses. He also suggested that all objects with mass are pulled toward the Earth.

• Varāhamihira (505 CE): Varāhamihira studied Indian and other cultures’ ideas about astronomy. His book Pañcasiddhāntikā brought together many different knowledge systems.

• Bhāskara I (629 CE): Bhāskara wrote several books about astronomy, discussing topics like planetary movements, eclipses, and the Moon’s phases. His work helped later astronomers.

• Lalla (8th century CE): Lalla wrote the Śiṣyadhīvṛddhida, which corrected some ideas of Āryabhaṭa. His book covered planetary calculations, eclipses, and tools for studying the stars.

• Śatānanda (1068–1099 CE): Śatānanda wrote Bhāsvatī, where he estimated the slow change in Earth’s tilt over time, called precession.

• Bhāskara II (1114 CE): Bhāskara II wrote books like Siddhāntaśiromaṇi and reported on his observations of planets and stars from his observatory in Ujjain.

• Śrīpati (1045 CE): Śrīpati followed Brahmagupta’s ideas and wrote Siddhāntaśekhara, introducing new concepts about the Moon’s movements.

• Mahendra Sūri (14th century CE): Mahendra Sūri wrote about the astrolabe, a tool for telling time and positions of stars. His book Yantra-rāja explained how to make and use this instrument.

• Makarandacarya (1438–1478 CE): He wrote the Makaranda sāriṇī, a book about astronomy.

• Parameshvara Nambudiri (1380–1460 CE): Parameshvara made careful observations of eclipses to check the accuracy of older astronomy methods. He improved some of these methods.

• Nilakantha Somayaji (1444–1544 CE): Nilakantha revised older models of how planets move. His ideas were very accurate and were used for many years. He also wrote about the importance of observing the sky to get correct information.

• Daśabala (fl. 1055–1058 CE): Daśabala wrote books including Cintāmanṇisāraṇikā and Karaṇakamalamārtaṇḍa.

• Acyuta Piṣāraṭi (1550–1621 CE): Acyuta Piṣāraṭi wrote books improving how people calculated planetary positions and eclipses. His work included methods for finding true positions of planets.

• Dinakara (1550 CE): Dinakara wrote Candrārkī, a popular book with verses for making calendars and finding positions of the Moon, Sun, and stars.

• Mathurānātha Śarman (1609 CE): He wrote Ravisiddhāntamañjarī, also called Sūryasiddhāntamañjarī.

• Pathani Samanta (1835–1904): Pathani Samanta was one of India’s last astronomers using only the naked eye. He made many instruments to study the stars and wrote a book called Siddhanta Darpan with new formulas for predicting celestial events. His work was honored by the government of India.

Instruments used

Ancient Indian astronomers used many clever tools to study the stars and the sky. One tool was the Sanku, or gnomon, a vertical rod whose shadow helped tell directions, time, and even where you were on Earth. Another tool was the Yasti-yantra, or Cross-staff, which could be a simple stick or a special V-shaped tool for measuring angles.

Astronomers also used the armillary sphere, a model of the sky on a frame, and water clocks called Ghatī-yantra. Later, big observatories were built with huge sundials and other instruments to track the movements of the Sun and stars. Some of these instruments were so large they looked like giant structures! One amazing invention was a seamless metal globe of the sky, made without any seams — a surprising feat of old metalworking skills.

Main article: Astronomy in the medieval Islamic world

International discourse

Indian astronomy shared ideas with other cultures, especially with the Greeks. Many Indian texts from the sixth century CE show similarities to Greek astronomy. Some Indian words about stars and time came from Greek. As Greek culture spread east, its ideas reached India, influencing local astronomers like Varahamihira and Brahmagupta.

Indian astronomy also reached China, especially during the spread of Buddhism. Later, Indian ideas influenced Islamic astronomy, and through this, they reached Europe. In the 17th century, Indian and Islamic astronomy mixed in the Mughal Empire, creating new ways to study the stars. Even after European astronomy became more common in India, some Indian scholars kept studying the older traditions.

Schools and organisations of astronomy

Further information: Jantar Mantar

See also: Jantar Mantar, Jaipur

Further information: Kerala school of astronomy and mathematics

In the 18th century, Jai Singh II built several large observatories called Jantar Mantars in cities such as Jaipur, Delhi, Ujjain, Varanasi, and Mathura. These observatories included many tools for studying the stars and predicting solar and lunar eclipses. One famous tool was the Samrat Yantra, the world's largest sundial, which helped tell very precise time.

The Kerala school of astronomy, active from 1380 to 1632, used advanced math to predict movements in our Solar System. They worked with complex equations to make accurate forecasts of planetary positions.

20th and 21st Century

During the 1920s, Indian astronomers such as Sisir Kumar Mitra, C.V. Raman, and Meghnad Saha worked on important projects. Homi J. Bhaba and Vikram Sarabhai helped advance astronomy in India. Vainu Bappu and Govind Swarup were key figures in developing modern observatories.

India's first modern observatory, the Madras Observatory, was established in 1786. Later, it moved and became the Kodaikanal Solar Observatory and then the Indian Institute of Astrophysics. Other observatories followed, such as the Aryabhatta Research Institute for Observational Sciences. The Tata Institute of Fundamental Research and the Physical Research Laboratory also contributed to space research. In 1962, the Indian National Committee for Space Research was created, which later became ISRO.

The Ooty Radio Telescope, built in 1970, was the largest of its kind in the world. Later, the Giant Meterwave radio Telescope was completed, also a world leader in radio astronomy. ISRO has made important discoveries, such as finding special bacteria in the upper atmosphere and launching the Astrosat space observatory. In 2023, Chandrayaan-3 successfully landed on the Moon's south pole, helping scientists learn more about our nearest neighbor in space.