Indian astronomy

Astronomy has a long and interesting history in the Indian subcontinent, going back to pre-historic times. One of the earliest known texts, the Vedanga Jyotisha, comes from around 1400–1200 BCE. It shows that ancient Indians watched the stars and planets closely. This knowledge was part of Vedanga. Vedanga was 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. They used ideas from the Yavanajataka and the Romaka Siddhanta. This helped them learn more about the universe.

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

History

A page from the Hindu calendar 1871–1872.

Some of the earliest ideas about astronomy began with the Indus Valley Civilisation or even earlier. Ancient texts such as the Vedas talk about stars, the Sun, and the Moon. These ideas were often connected to religion and helped people know when to hold ceremonies.

Later, new ideas from Greece reached India after the conquests of Alexander the Great. Famous Indian astronomers like Aryabhata discovered important facts about how planets move. They used tools like a gnomon to study the stars and found smart ways to calculate time and positions.

Calendars

Further information: Hindu calendar

In ancient India, people divided the year into seasons like spring, summer, and winter. The Hindu calendar has special starting points, or "eras." One of these starts from the beginning of the Kali Yuga, a very old time. These calendars helped people track time and plan important events.

Astronomers

Lagadha (1st millennium BCE): Lagadha was an early Indian astronomer. He wrote the Vedānga Jyotiṣa, which helped people plan social and religious events. The book also talked about the Moon, the Sun, and the seasons.
Āryabhaṭa (476–550 CE): Āryabhaṭa wrote important books about astronomy. He was one of the first to say that the Earth spins, making the stars seem to move. He also explained that the Moon shines because of sunlight reflecting on it.
Brahmagupta (598–668 CE): Brahmagupta wrote about math and astronomy. His book talked about how planets move and about eclipses. He also had ideas about how objects are pulled toward the Earth.
Varāhamihira (505 CE): Varāhamihira studied astronomy from India and other places. His book brought together many different ideas about the stars and planets.
Bhāskara I (629 CE): Bhāskara wrote books about astronomy. He talked about planets, eclipses, and the Moon’s phases. His work helped other astronomers.
Lalla (8th century CE): Lalla wrote a book that corrected some of Āryabhaṭa's ideas. His book covered how to calculate the positions of planets and when eclipses would happen.
Śatānanda (1068–1099 CE): Śatānanda wrote a book where he talked about a slow change in the way the Earth tilts.
Bhāskara II (1114 CE): Bhāskara II wrote books about astronomy. He observed planets and stars from his observatory in Ujjain.
Śrīpati (1045 CE): Śrīpati followed Brahmagupta's ideas. He wrote a book with new ideas about the Moon’s movements.
Mahendra Sūri (14th century CE): Mahendra Sūri wrote about the astrolabe, a tool for telling time and finding where stars are. His book explained how to make and use this tool.
Makarandacarya (1438–1478 CE): He wrote a book about astronomy called the Makaranda sāriṇī.
Parameshvara Nambudiri (1380–1460 CE): Parameshvara watched eclipses to check old astronomy methods. He made some of these methods better.
Nilakantha Somayaji (1444–1544 CE): Nilakantha improved old ideas about how planets move. His ideas were very good and were used for many years. He also said it was important to watch the sky to get the right information.
Daśabala (fl. 1055–1058 CE): Daśabala wrote books about astronomy.
Acyuta Piṣāraṭi (1550–1621 CE): Acyuta Piṣāraṭi wrote books with better ways to figure out where planets are and when eclipses will happen.
Dinakara (1550 CE): Dinakara wrote a popular book with verses for making calendars and finding where the Moon, Sun, and stars are.
Mathurānātha Śarman (1609 CE): He wrote a book called Ravisiddhāntamañjarī, also known as Sūryasiddhāntamañjarī.
Pathani Samanta (1835–1904): Pathani Samanta was one of India’s last astronomers who used only the naked eye. He made many tools to study the stars and wrote a book called Siddhanta Darpan with new ways to predict events in the sky. 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. Its shadow helped tell directions and time. Another tool was the Yasti-yantra, or Cross-staff. This could be a simple stick or a V-shaped tool for measuring angles.

Sawai Jai Singh (1688–1743 CE) initiated the construction of several observatories. Shown here is the Jantar Mantar (Jaipur) observatory.

Astronomers also used the armillary sphere, a model of the sky on a frame. They used water clocks called Ghatī-yantra. Later, big observatories were built with huge sundials. These helped track the movements of the Sun and stars. Some instruments were very large, looking like giant structures! One amazing invention was a seamless metal globe of the sky, made without any seams.

Main article: Astronomy in the medieval Islamic world

International discourse

Greek equatorial sun dial, Ai-Khanoum, Afghanistan 3rd–2nd centuries BCE

Indian astronomy shared ideas with other cultures, especially with the Greeks. Many Indian books from the sixth century CE had ideas like those in Greek astronomy. Some Indian words about stars came from Greek.

As Greek culture spread east, its ideas reached India and influenced local astronomers like Varahamihira and Brahmagupta.

Indian astronomy also reached China, especially when Buddhism spread. 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

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.