🃏 Science and technology in India

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When: Stone hand-axes at Attirampakkam? — c. 1.5 million years ago — Tamil Nadu

When: Smaller, finer stone tools? — c. 385,000–172,000 years ago — Attirampakkam, Tamil Nadu

When: Farming begins at Mehrgarh? — from c. 7000 BCE — Mehrgarh, Balochistan

When: The earliest dentistry? — 7,500–9,000 years ago — Mehrgarh, Balochistan

When: Early cotton? — Neolithic period — Mehrgarh, Balochistan

When: A ploughed field and terracotta ploughs? — Early Harappan — Kalibangan, Rajasthan

When: Copper and bronze metallurgy? — Harappan period — Harappan cities

What is it: Copper and bronze metallurgy? — The Harappan civilisation mastered copper and bronze metallurgy — a technology that made its cities possible.

When: The Harappan script? — Harappan civilization — Harappan cities

When: Planned drainage? — Harappan civilization — Mohenjo-daro, Harappa and other cities

When: Bricks of a standard ratio? — Harappan period — Harappan settlements

What is it: Bricks of a standard ratio? — Sun-dried or baked, Harappan bricks kept one ratio — length four times and breadth twice the height — and were used at all Harappan settlements, a sign the towns were planned first and then built.

When: Lost-wax bronze casting? — c. 2500 BCE — Mohenjo-daro

What is it: Lost-wax bronze casting? — The ‘lost-wax’ (cire-perdu) casting process was learnt as long ago as the Indus Valley Culture; the ‘Dancing Girl’ from Mohenjodaro is perhaps the earliest bronze sculpture, datable to 2500 BCE. Tribal craftspeople still use the process today.

When: Standard weights? — Harappan civilization — Harappan cities

When: Drilling hard stone beads? — Harappan period — Chanhudaro, Lothal, Dholavira

What is it: Drilling hard stone beads? — Beads of carnelian and other stones were shaped, ground, polished and drilled; specialised drills have been found at Chanhudaro, Lothal and Dholavira.

When: Scales and units of length? — Harappan period — Harappan sites

What is it: Scales and units of length? — Objects with ruled markings that could be scales have been found at Harappan sites. Later Indian literature names units such as the angula (finger width), dhanusa and yojana, used for artefacts, architecture and town planning — and carpenters and tailors still use the angula.

When: The wheel: terracotta carts? — Harappan civilization — Harappan sites

When: The dockyard at Lothal? — Harappan period — Lothal, Gujarat

What is it: The dockyard at Lothal? — A huge brick basin at the Harappan settlement of Lothal, which NCERT presents as a dockyard linked to trade.

When: Water management at Dholavira? — c. 3000–1500 BCE — Dholavira, Gujarat

When: Iron working in the Ganga plain? — 1800–1000 BCE — Uttar Pradesh

When: Number names and fractions in the Vedas? — Vedic period

What is it: Number names and fractions in the Vedas? — The Yajurveda Samhita lists names for powers of ten — eka, dasha, shata, sahasra, ayuta and on up to 10¹² and beyond; the Rig Veda calls the fraction three-quarters tri-pada.

When: The Sulba-sutras: geometry with a rope? — c. 800 BCE (Baudhayana)

What is it: The Sulba-sutras: geometry with a rope? — Geometric texts of the Vedic period on building fire altars — the earliest known Indian texts with methods to construct perpendiculars and perpendicular bisectors, using a rope as the compass. Baudhayana’s Sulbasutra (c. 800 BCE) already works with non-unit fractions.

When: Paddy transplantation? — c. 600–500 BCE — Ganga valley

When: Panini’s Ashtadhyayi? — c. 500 BCE

What is it: Panini’s Ashtadhyayi? — The Ashtadhyayi of Panini, a work on Sanskrit grammar.

When: Takshashila, a centre of learning? — Mauryan times — Takshashila (Taxila)

What is it: Takshashila, a centre of learning? — According to Buddhist texts, Kautilya — author of the Arthashastra, ‘the science of governance and economics’ — was a teacher at the world-renowned Takshashila university.

When: Brahmi: Ashoka's inscriptions? — 3rd century BCE — Across the Mauryan Empire

When: Wootz steel? — Ancient and medieval periods — South India

When: Shadow clocks and water clocks? — 2nd century BCE – 3rd century CE

What is it: Shadow clocks and water clocks? — The earliest reference to measuring time by shadows is in Kautilya’s Arthasastra, which also describes a water clock with water flowing out.

When: Charaka and Sushruta Samhitas? — c. 100 CE; final shape in the Gupta period

What is it: Charaka and Sushruta Samhitas? — Works on medicine in Sanskrit. Ayurveda has much older roots, but these texts — which deal with cataloguing and diagnosing diseases, among other topics — were compiled and given their final shape during the Gupta period.

When: The Kallanai (Grand Anicut)? — Karikala’s reign — Kaveri, below Srirangam

What is it: The Kallanai (Grand Anicut)? — A complex water-diversion system built by the Chola king Karikala just downstream of Srirangam island, sending Kaveri waters to the central and southern delta so that more land could be irrigated.

When: Sudarshana lake, a reservoir? — c. second century CE — Girnar, Gujarat

What is it: Sudarshana lake, a reservoir? — An artificial reservoir known from a Sanskrit rock inscription recording the achievements of the Shaka ruler Rudradaman, who rebuilt it.

When: Zero: the Bakhshali manuscript? — as early as the 3rd or 4th century CE — Bakhshali (now in Pakistan)

When: Nalanda Mahavihara? — 3rd century BCE – 13th century CE — Nalanda, Bihar

When: The rust-resistant iron pillar? — Ancient period — Delhi

When: Aryabhata and the Aryabhatiya? — around 500 CE — Kusumapura (near Patna)

What is it: Aryabhata and the Aryabhatiya? — A short treatise of mathematics and astronomy. Aryabhata proposed that the Earth spins on its axis, gave the length of the year within minutes of the modern value, estimated the size of the Earth and correctly explained solar and lunar eclipses. His value for one rotation of the Earth is about 23 hours 56 minutes 4.1 seconds.

When: Aryabhata computes with ten digits? — 499 CE

What is it: Aryabhata computes with ten digits? — Aryabhata was the first mathematician to fully explain, and do elaborate scientific computations with, the Indian system of ten symbols; he also first proposed a systematic way to solve problems with a single unknown.

When: The Ghatika-yantra (sinking-bowl water clock)? — Aryabhata’s time

What is it: The Ghatika-yantra (sinking-bowl water clock)? — Because outflow clocks slowed as the water dropped, a sinking-bowl water clock was developed — first mentioned by Aryabhata. It kept time at monasteries, palaces and town squares, where each sinking of the bowl was announced; the day was divided into 60 ghatis.

When: Varahamihira’s Brihat Samhita? — Gupta period — Ujjayini (Ujjain)

What is it: Varahamihira’s Brihat Samhita? — An encyclopedic work covering astronomy and astrology, weather forecasting, architecture, town planning and even farming.

When: Time from a stick’s shadow? — around 530 CE

What is it: Time from a stick’s shadow? — Varahamihira gave an accurate expression for time in terms of the shadow of a vertical stick.

When: Brahmagupta: rules for zero? — born 598 CE — Bhillamala

What is it: Brahmagupta: rules for zero? — In the Brahmasphutasiddhanta he gave the rules of arithmetic with zero, negative numbers and fractions. His works were later translated into Persian and Latin.

When: Bhaskara I and trigonometry? — 6th–10th centuries

What is it: Bhaskara I and trigonometry? — Bhaskara I did pioneering work in trigonometry and wrote a lengthy commentary on the Aryabhatiya.

When: Brahmagupta’s rules for fractions? — 628 CE

What is it: Brahmagupta’s rules for fractions? — The Brahmasphutasiddhanta first stated in general form how to add, subtract, multiply and divide fractions — the methods still taught today. These ideas reached Europe through the Arabs.

When: Virahanka’s numbers? — c. 700 CE

What is it: Virahanka’s numbers? — Counting the rhythms of short and long syllables in poetry, the Prakrit scholar Virahanka gave the rule for the sequence 1, 2, 3, 5, 8, 13, 21… — the first known person to write it down. It is now called the Virahanka–Fibonacci sequence.

When: Vikramashila university? — late 8th century — Banks of the Ganga, Bihar

What is it: Vikramashila university? — Founded by the Pala king Dharmapala, it remained a great centre of learning for more than four centuries, with six colleges, a vast library and nearly 3,000 scholars. Each college had a ‘scholar gatekeeper’ who set the admission test.

When: Indian numerals reach the Arab world? — 9th century — Baghdad

What is it: Indian numerals reach the Arab world? — Sanskrit texts of mathematics, astronomy and medicine were translated into Arabic. The Arabs adopted India’s decimal numeral system with the zero; in Europe these became known as ‘Arabic numerals’.

When: Al-Khwarizmi’s ‘Hindu numerals’? — c. 825 CE — Baghdad

What is it: Al-Khwarizmi’s ‘Hindu numerals’? — The Indian number system reached the Arab world by around 800 CE and was popularised there by Al-Khwarizmi’s book On the Calculation with Hindu Numerals (c. 825) and Al-Kindi’s On the Use of the Hindu Numerals (c. 830).

When: Mahaviracharya’s Ganita-sara-sangraha? — c. 850 CE

What is it: Mahaviracharya’s Ganita-sara-sangraha? — Mahaviracharya developed the arithmetic of fractions further and, in the Ganita-sara-sangraha, named the powers of ten up to 10²³.

When: The Chautisa Yantra magic square? — 10th century — Khajuraho

What is it: The Chautisa Yantra magic square? — The first recorded 4 × 4 magic square, in an inscription at the Parshvanath Jain temple: every row, column and diagonal adds up to 34.

When: Surapala’s Vrikshayurveda? — around the 10th century CE

What is it: Surapala’s Vrikshayurveda? — A text of plant science: which plants suit which soils, seed collection and treatment, irrigation by species and season, and natural pest control.

When: Al-Biruni studies Indian science? — 11th century — Ghazni

What is it: Al-Biruni studies Indian science? — Al-Biruni learnt Sanskrit and wrote an encyclopaedic survey of India, compiling in mathematics and astronomy what he could gather from the works of Aryabhata, Varahamihira and Brahmagupta.

When: Stepwells: Rani-ki-Vav? — 11th century — Patan, Gujarat

When: Bhaskaracharya’s Lilavati? — born 1114 — probably present-day Maharashtra

What is it: Bhaskaracharya’s Lilavati? — One of India’s greatest mathematicians and astronomers: Lilavati (1150 CE) teaches mathematics through riddles, Bijaganita covers advanced algebra and Siddhantashiromani astronomical calculation. Several of his works were translated into Persian in the Mughal period.

When: Watching the sky in bowls of water? — Bhaskara II’s time

What is it: Watching the sky in bowls of water? — More than 800 years ago, astronomers looked at stars and planets reflected in shallow bowls of water, through tubes set at the right angles, to measure their positions.

When: Indian numerals reach Europe? — around 1200

What is it: Indian numerals reach Europe? — From the Arab world the numerals reached Europe and parts of Africa by around 1100 CE; around 1200 the Italian mathematician Fibonacci made the case for Europe to adopt them. Arab scholars called them ‘Hindu numerals’.

When: Pure zinc by distillation? — 13th–17th centuries

What is it: Pure zinc by distillation? — The production of pure zinc reached its peak, with a special distillation process used for the first time in the world.

When: Narayana Pandita’s Ganitakaumudi? — 14th century

What is it: Narayana Pandita’s Ganitakaumudi? — A massive treatise of mathematics that included important original developments.

When: Madhava and the Kerala School? — 14th century — Kerala

What is it: Madhava and the Kerala School? — Madhava gave the series expansion for trigonometric functions — a world first — and an exact value of π as an infinite series. He and his followers are known as the Kerala School of Astronomy and Mathematics.

When: Nilakantha Somayaji’s planetary model? — 1500 — Kerala

What is it: Nilakantha Somayaji’s planetary model? — A scholar of the Kerala School worked out a planetary model in which Mercury and Venus went round the Sun.

When: The first printing press? — September 1556 — Old Goa

When: Jaipur, a planned city? — 1727 — Jaipur

What is it: Jaipur, a planned city? — Vidyadhar Bhattacharya, appointed by Sawai Jai Singh II, designed the new city on a grid of rectangular blocks, aligned to the cardinal directions, with wide streets, gardens and nine public squares.

When: Jantar Mantar observatory? — early 18th century — Jaipur, Rajasthan

When: India’s first printed newspaper? — 1780

What is it: India’s first printed newspaper? — The Bengal Gazette — the start, in NCERT’s timeline of communication, of printed news in India.

When: The first passenger train? — 16 April 1853 — Bombay (Mumbai) – Thane

When: India Meteorological Department set up? — 1875

What is it: India Meteorological Department set up? — After a disastrous cyclone struck Calcutta in 1864 and the monsoon failed in 1866 and 1871, the Government of India brought all meteorological work under one central authority. Its motto: ‘From the sun arises rain.’

When: Electric light arrives? — 1879 — Calcutta (Kolkata)

When: Darjeeling Himalayan Railway? — 1881 — Darjeeling, West Bengal

When: J.C. Bose shows wireless transmission? — 1895 — Calcutta

What is it: J.C. Bose shows wireless transmission? — Jagadish Chandra Bose pioneered wireless transmission using microwaves in the millimetre range; in an experiment in Calcutta he showed that signals could pass through a wall.

When: First commercial electricity: Sidrapong? — 1897 — Darjeeling, West Bengal

When: P.C. Ray founds India’s first pharmaceutical company? — 1901

What is it: P.C. Ray founds India’s first pharmaceutical company? — Prafulla Chandra Ray, ‘Father of Modern Indian Chemistry’, founded Bengal Chemicals and Pharmaceuticals — part of the Swadeshi drive to break the British monopoly. He also wrote on the history of chemistry in India.

When: Indian Institute of Science founded? — 27 May 1909 — Bangalore

What is it: Indian Institute of Science founded? — The Indian Institute of Science came into existence in Bangalore, after Jamsetji Tata’s vision and a Government of India vesting order.

When: Steel from Jamshedpur? — 16 February 1912 — Jamshedpur, Jharkhand

When: R.H. Dastur studies photosynthesis? — 1921–1935 — Royal Institute of Science, Bombay

What is it: R.H. Dastur studies photosynthesis? — As head of Botany, Rustom Hormusji Dastur studied how water, temperature and the colour of light affect photosynthesis.

When: Imperial Council of Agricultural Research founded? — 16 July 1929

What is it: Imperial Council of Agricultural Research founded? — Set up following the report of the Royal Commission on Agriculture; it is today the Indian Council of Agricultural Research (ICAR).

When: Radio broadcasting begins? — 1930

What is it: Radio broadcasting begins? — NCERT’s timeline of communication marks 1930 as the start of All India Radio (AIR) broadcasting in India.

When: C.V. Raman wins the Nobel Prize in Physics? — 1930

What is it: C.V. Raman wins the Nobel Prize in Physics? — Awarded “for his work on the scattering of light and for the discovery of the effect named after him” — the Raman effect.

When: Indian Statistical Institute founded? — 1931

What is it: Indian Statistical Institute founded? — Founded by P.C. Mahalanobis, a scientist and statistician of international repute who later led the team that drafted the Second Five Year Plan.

When: India’s nuclear programme begins? — late 1940s

What is it: India’s nuclear programme begins? — Initiated under the guidance of Homi J. Bhabha, to generate atomic energy for peaceful purposes.

When: Department of Atomic Energy set up? — 3 August 1954

What is it: Department of Atomic Energy set up? — Set up under the direct charge of the Prime Minister by a Presidential Order.

When: Apsara, Asia’s first research reactor? — 4 August 1956 — Trombay

What is it: Apsara, Asia’s first research reactor? — Apsara achieved criticality and was the first research reactor in Asia to do so.

When: The Indian National Calendar? — 21 March 1956

What is it: The Indian National Calendar? — A Calendar Reform Committee chaired by Meghnad Saha recommended a unified national calendar, adopted from 1 Chaitra 1878 Saka; it follows the general principles of the Surya Siddhanta.

When: Diesel locomotives: the WDM-1? — 1957

What is it: Diesel locomotives: the WDM-1? — In NCERT’s timeline of Indian trains, the WDM-1 diesel locomotive (1957) follows steam, and the WAM-4 electric locomotive follows in 1970.

When: Atomic Energy Commission set up? — 1 March 1958

What is it: Atomic Energy Commission set up? — An Atomic Energy Commission with full executive and financial powers was set up to plan and expand the atomic energy programme; it makes the policy of the Department of Atomic Energy.

When: The CIRUS research reactor? — 10 July 1960 — Trombay

What is it: The CIRUS research reactor? — A 40 MWth reactor built with Canada, used for neutron research, testing fuel and making radioisotopes for medicine, agriculture and industry; it trained the engineers of India’s heavy-water reactor programme and ran for 50 years.

When: TIFRAC: India's first working computer? — 1954–1960 — TIFR, Mumbai

When: INCOSPAR: India’s space research begins? — 1962

What is it: INCOSPAR: India’s space research begins? — The Indian National Committee for Space Research was set up by the Government of India, as envisioned by Vikram Sarabhai.

When: The Green Revolution? — 1960s and 1970s

What is it: The Green Revolution? — High-yielding seeds, more irrigation, fertilisers and machines raised food-grain production — especially of wheat and rice — and India became self-sufficient in food. NCERT also notes its costs to soil and groundwater.

When: Har Gobind Khorana shares the Nobel Prize? — 1968

What is it: Har Gobind Khorana shares the Nobel Prize? — Physiology or Medicine, shared with Robert W. Holley and Marshall W. Nirenberg, “for their interpretation of the genetic code and its function in protein synthesis”.

When: ISRO is formed? — 15 August 1969

What is it: ISRO is formed? — The Indian Space Research Organisation superseded INCOSPAR with an expanded role to harness space technology.

When: Tarapur: India’s first nuclear power station? — 28 October 1969 — Tarapur, Maharashtra

What is it: Tarapur: India’s first nuclear power station? — Units 1 and 2 of the Tarapur Atomic Power Station, boiling-water reactors of 160 MWe each, began commercial operation — the first entries in NPCIL’s list of nuclear power plants.

When: The White Revolution (Operation Flood)? — 1960s and 1970s

What is it: The White Revolution (Operation Flood)? — Alongside the Green Revolution, one of the strategies the Government of India began to improve Indian agriculture.

When: A bacterium that breaks down oil spills? — 1971

What is it: A bacterium that breaks down oil spills? — Ananda Mohan Chakrabarty developed a bacterium that could break down oil spills; the discovery was patented in 1980.

When: India’s first nuclear test? — May 1974 — Pokhran

What is it: India’s first nuclear test? — The first nuclear explosion undertaken by India.

When: Aryabhata, India’s first satellite? — 19 April 1975 — Launched from the Soviet Union

What is it: Aryabhata, India’s first satellite? — Named after the astronomer, it was completely designed and fabricated in India and launched by a Soviet rocket.

When: Bhaskara-I: first Indian remote-sensing satellite? — 7 June 1979 — Volgograd launch station (now in Russia)

What is it: Bhaskara-I: first Indian remote-sensing satellite? — The first experimental remote-sensing satellite built in India; its TV camera images were used in hydrology and forestry.

When: SLV-3 puts Rohini in orbit? — 18 July 1980 — Sriharikota

What is it: SLV-3 puts Rohini in orbit? — India’s first experimental satellite launch vehicle placed the Rohini satellite RS-1 in orbit, making India the sixth member of an exclusive club of space-faring nations.

When: APPLE, the first Indian communication satellite? — 19 June 1981 — Launched from Kourou

What is it: APPLE, the first Indian communication satellite? — ISRO’s first indigenous experimental communication satellite, designed and built in two years in industrial sheds and launched on an Ariane rocket.

When: Subrahmanyan Chandrasekhar shares the Nobel Prize? — 1983

What is it: Subrahmanyan Chandrasekhar shares the Nobel Prize? — Physics, shared with William A. Fowler; Chandrasekhar’s share was “for his theoretical studies of the physical processes of importance to the structure and evolution of the stars”.

When: INSAT-1B? — 30 August 1983

What is it: INSAT-1B? — A communication satellite that reached full operational capability in October 1983 and worked into 1990, with all its 4,375 two-way voice circuits in use; it returned around 36,000 Earth images.

When: Fast Breeder Test Reactor goes critical? — October 1985 — Kalpakkam

What is it: Fast Breeder Test Reactor goes critical? — With the 40 MWth FBTR at the Indira Gandhi Centre for Atomic Research, India entered the small club of countries with fast-breeder technology — the second stage of its three-stage nuclear programme. It runs on an indigenously developed uranium–plutonium carbide fuel.

When: C-DAC and the PARAM supercomputer? — 1988

What is it: C-DAC and the PARAM supercomputer? — C-DAC was set up to build supercomputers after the USA denied their import; it has built generations of them, starting with PARAM.

When: Nuclear tests at Pokhran? — May 1998 — Pokhran

What is it: Nuclear tests at Pokhran? — India conducted nuclear explosions at Pokhran.

When: Mid Day Meal Programme, built on nutrition science? — 2002

What is it: Mid Day Meal Programme, built on nutrition science? — Coluthur Gopalan analysed more than 500 Indian foods and surveyed the nation’s nutrition; his findings of widespread deficiencies led to the Mid Day Meal Programme, now PM POSHAN.

When: Cartosat-1: maps in stereo? — 5 May 2005 — Sriharikota

What is it: Cartosat-1: maps in stereo? — The first Indian remote-sensing satellite able to take stereo images in orbit, at 2.5 m resolution — used for elevation models and maps. NCERT notes that Cartosat images feed the Bhuvan mapping platform.

When: Chandrayaan-1? — 22 October 2008 — Sriharikota

When: IRNSS-1A: India’s own navigation system begins? — 1 July 2013 — Sriharikota

What is it: IRNSS-1A: India’s own navigation system begins? — The first of the seven satellites of the Indian Regional Navigation Satellite System, carrying a rubidium atomic clock in its navigation payload.

When: Mars Orbiter Mission? — 5 November 2013 — Sriharikota

When: AstroSat, India’s space observatory? — 28 September 2015 — Sriharikota

What is it: AstroSat, India’s space observatory? — India’s first dedicated space astronomy observatory, with five payloads that observe the same source at once from far ultraviolet to gamma rays.

When: UPI: instant digital payments? — 25 August 2016 — India

When: Chandrayaan-2? — 22 July 2019

What is it: Chandrayaan-2? — An orbiter, lander and rover to explore the unexplored south pole of the Moon — a significant technological leap for ISRO. It entered lunar orbit on 20 August 2019.

When: Vande Bharat trains? — 2019

What is it: Vande Bharat trains? — The electric Vande Bharat train — the latest step in NCERT’s timeline of Indian trains, after steam, diesel and electric locomotives.

When: Hanle Dark Sky Reserve? — December 2022 — Hanle, Ladakh

What is it: Hanle Dark Sky Reserve? — The area around the Himalayan Chandra Telescope — named after Subrahmanyan Chandrasekhar, at one of the highest observatories in the world — was notified as a dark sky reserve.

When: Aditya-L1 studies the Sun? — 2 September 2023

What is it: Aditya-L1 studies the Sun? — A satellite dedicated to the comprehensive study of the Sun, with seven indigenously developed payloads, placed near the L1 point between the Earth and the Sun.

When: Chandrayaan-3 lands on the Moon? — 23 August 2023 — The Moon

What is it: Kanad’s Parmanu? — Acharya Kanad first spoke of the Parmanu: matter made of tiny, indivisible, eternal particles. The idea is in his Vaisheshika Sutras.

What is it: The Surya Siddhanta and eclipses? — Many Indian astronomical texts give calculations to predict eclipses; the best known is the Surya Siddhanta, written in rhythmic Sanskrit shlokas. The Indian National Calendar adopted in 1956 follows its general principles.

What is it: Variolation against smallpox? — Long before modern vaccines, India had variolation: material from a smallpox sore was scratched into the skin to cause a mild infection and build immunity. Its practitioners were known as teekedaars.

What is it: Mishraloha: alloys in medicine? — Mishraloha was a mixture of metals with properties of its own. The Charaka Samhita, Susruta Samhita and Rasaratna Samucchaya mention alloys in medicine — bronze (kamsya) was 4 parts copper to 1 part tin. The Rasaratna Samucchaya says crucibles were made of clay and iron.

What is it: Krimi: visible and invisible? — The Vedas, including the Atharvaveda, use the word ‘krimi’ for tiny entities, both drishya (visible) and adrishya (invisible), and mention their beneficial and harmful effects.

What is it: Kunapa Jala: fermented manure? — The Vrikshayurveda advocates feeding the soil continuously with organic manure such as kunapa jala, a liquid fertiliser made by fermenting animal and plant waste.

Who: Built the crescograph to record how plants respond to light, heat, electricity and gravity, and showed that plants sense and respond to stimuli; also pioneered wireless transmission with millimetre waves. — Jagadish Chandra Bose (1858–1937)

Who: ‘Father of Modern Indian Chemistry’; founded India’s first pharmaceutical company in 1901, wrote on the history of chemistry in India and advocated teaching in the mother tongue. — Prafulla Chandra Ray

Who: Working with G. H. Hardy at Cambridge, he pointed out that 1729 is the smallest number expressible as the sum of two cubes in two different ways — now the Hardy–Ramanujan number. ‘Every positive integer was one of his personal friends,’ said Littlewood. — Srinivasa Ramanujan

Who: Pioneering astrophysicist who studied stars and their temperatures and gave the Saha equation; chaired the Calendar Reform Committee. The Saha Institute of Nuclear Physics in Kolkata is named after him. — Meghnad Saha (1893–1956)

Who: The ‘Birdman of India’ travelled the country recording birds, their routes and habitats, helped conserve places such as Keoladeo (Bharatpur) and Ranganathittu, and wrote a landmark 10-book series on the birds of the Subcontinent. — Salim Ali (1896–1987)

Who: Plant scientist who studied how water, temperature and the colour of light affect photosynthesis. — Rustom Hormusji Dastur (1896–1961)

Who: Botanist who, as head of the Botanical Survey of India, began programmes to document India’s plant diversity, and played a key role in the ‘Save Silent Valley’ movement. — Janaki Ammal (1897–1984)

Who: Earned a Ph.D. at Cambridge for work on respiration in plants, later directed the Royal Institute of Science, Bombay, and worked to improve the nutritive value of plant foods — including neera from coconut-palm sap. — Kamala Sohonie (1911–1998)

Who: Biomedical researcher who studied how hormones and certain viruses are linked to cancer, and showed how tobacco, diet and pollution raise cancer risk. — Kamal Ranadive (1917–2001)

Who: Began nutrition research in India, analysed more than 500 Indian foods and recommended a diet suited to India; his surveys led to the Mid Day Meal Programme (2002). — Coluthur Gopalan (1918–2019)

Who: The ‘Weather Woman of India’ invented and built many weather instruments, reducing India’s reliance on imports, and explored wind and solar energy. — Anna Mani (1918–2001)

Who: Developed anti-epileptic and anti-malarial drugs from medicinal plants; the second Indian woman to earn a Doctorate of Science and the first woman to receive the Shanti Swarup Bhatnagar Award in chemical science. — Asima Chatterjee

Who: Called the architect of the Green Revolution, and a recipient of the Bharat Ratna. — M. S. Swaminathan

Who: Scientist and statistician of international repute who founded the Indian Statistical Institute (1931) and led the drafting of the Second Five Year Plan. — P. C. Mahalanobis (1893–1972)

Who: Studied bacteria and in 1971 developed one that breaks down oil spills — showing how microbes can tackle pollution. — Ananda Mohan Chakrabarty (1938–2020)

Who: Doctor and scientist who, as Secretary of the Department of Biotechnology, played a key role in developing the Rotavirus vaccine that protects children from diarrhoea. — Maharaj Kishan Bhan