Science and Technology in Ancient India

India carries a long and well-documented legacy of scientific thinking. Many ideas that the modern world takes for granted first took shape here: the technique of algebra and the algorithm, the concept of zero, the surgical repair of a nose, the idea that matter is built from tiny indivisible particles, the herbal system of medicine, the smelting of metals, even the game of chess. Studying this period is not about nostalgia. It is about recognising that careful observation and reasoning have a deep history in the subcontinent. These contributions are also a favourite area for examiners.

Mathematics in ancient India went by the general name Ganita. It covered several branches:

• Arithmetic: called Pattin Ganita or Anka Ganita.
• Algebra: called Bijaganita, literally "the other mathematics".
• Geometry: called Rekha Ganita.
• Astronomy: called Khagolshastra.
• Astrology: called Jyotisa.

The earliest known mathematical work was the Sulvasutra, written by Baudhayana in the 6th century BC. It already contained a value for Pi (used to find the area and circumference of a circle) and rules very similar to what later became known as the Pythagoras theorem. In the 2nd century BC, Apastamba developed practical geometry (acute, obtuse and right angles). This knowledge was used to lay out fire altars. The fine town planning of the Harappan cities also shows an early command of measurement and geometry.

A series of great mathematicians followed:

• Aryabhatta (around 499 AD) wrote the Aryabhattiya. It introduced a method of denoting large decimal numbers using alphabets, and covered number theory, geometry, trigonometry and algebra. He worked out the area of a triangle and is credited with a value of Pi more accurate than the Greeks'.
• Brahmagupta (7th century AD), in his Brahmasputa Siddhantika, was the first to treat zero (Shunya) as a number in its own right. He also introduced negative numbers, describing them as "debts" and positive numbers as "fortunes". In geometry, he worked out the properties of cyclic quadrilaterals, four-sided figures whose corners all lie on a circle, including a formula for their area.
• Mahaviracharya (9th century AD) wrote Ganit Sara Sangraha. It was the first textbook on arithmetic in its present form. It laid out the method of finding the Lowest Common Multiple long before John Napier.
• Bhaskaracharya (12th century AD) wrote the Siddhanta Shiromani in four parts: Lilavati (arithmetic), Beejganita (algebra), Goladhyaya (spheres) and Grahaganita (mathematics of the planets). His chakrawat (cyclic) method solved algebraic equations.
• Pingala described the binary number system in his Chandahsastra, the earliest Sanskrit treatise on prosody. The sequence later known in Europe as Fibonacci numbers first appears in his work as the matrameru.

This mathematical precision was part of a wider scientific culture, and the two are often tested together. While geometers refined Pi and the properties of figures, surgeons refined their tools. By around the 1st century AD, the Sushruta Samhita already describes a large set of specialised surgical instruments, and these were in common use among practising surgeons. So two claims about this era are both true: ancient India had an accurate value of Pi early on, and it had specialised surgical tools in everyday use by the 1st century AD.

The concept of zero and the decimal place-value system spread outward from India. Arab traders carried it abroad. The Arabs acknowledged the debt by calling mathematics "Hindisat", the Indian art. In the medieval period the tradition continued: Narayan Pandit wrote Ganitakaumudi and Bijaganitavatamsa, Nilakantha Somasutvan wrote Tantrasamgraha on trigonometric functions, and at Akbar's court Faizi translated Bhaskara's Lilavati and Beejaganita into Persian.

Astronomy was called Khagol shastra, named after Khagol, the famous astronomical observatory at Nalanda where Aryabhatta studied. People studied the skies for very practical reasons:

• To make calendars accurate.
• To predict climate and rainfall patterns.
• To aid navigation, which let traders cross deserts and seas by reading direction from the night sky.
• To know the tides and the stars.
• To cast horoscopes.

The towering figure here is again Aryabhatta. In a sharp break from the beliefs of his day, he argued that:

• The earth is round and rotates on its own axis.
• A lunar eclipse happens when the shadow of the earth falls on the moon.
• A solar eclipse happens when the shadow of the moon falls on the earth.

This was a clear departure from the orthodox explanation that a demon was swallowing the planet. The Jyotisa part of his work also dealt with the true positions of the planets and the movements of the sun and moon. Centuries later, Bhaskaracharya calculated the time the earth takes to orbit the sun as about 365.2588 days. This is remarkably close to the modern figure.

Medieval rulers carried the tradition forward by building observatories:

• Feroz Shah Tughlaq set up an observatory in Delhi.
• Feroz Shah Bahmani set one up at Daulatabad. His court astronomer Mahendra Suri invented an astronomical instrument called the Yantaraja.
• Sawai Jai Singh built five observatories, the Jantar Mantars, at Delhi, Jaipur, Varanasi, Ujjain and Mathura.

In the Vedic age, the Ashwini Kumars were honoured as divine physicians and Dhanvantari was worshipped as the god of medicine. The Atharva Veda was the first text to mention diseases, cures and medicines, including remedies for diarrhoea, cough, leprosy, fever and seizures. It still blamed illness on demons and spirits. A more rational, practical era of medicine emerged around 600 BC, with Takshila and Varanasi as the leading centres of medical learning. Two great treatises define the period:

• Charak Samhita, by Charak, is the foundational text of Ayurveda (the science of healthy living through plants and herbs).
• Sushruta Samhita, by Sushruta, is the foundational text of surgery, which was then called Sastrakarma.

The Charak Samhita organised Ayurveda into eight branches:

• Kaya Chikitsa: general medicine.
• Kaumara-Bhrtya: paediatrics.
• Shalya Chikitsa: surgery.
• Salakya Tantra: ophthalmology and ENT.
• Bhuta Vidya: psychiatry and demonology.
• Agada Tantra: toxicology.
• Rasayana Tantra: elixirs and rejuvenation.
• Vajikarana Tantra: aphrodisiacs.

Charaka taught that the body is governed by three doshas: Vata (wind), Pitta (bile) and Kapha (phlegm). Disease arises when these fall out of balance. He stressed prevention over cure, and even touched on digestion, metabolism, immunity and genetics. Sushruta, often called the father of surgery, studied anatomy using a human cadaver. His Samhita, which had taken shape by around the 1st century AD, describes about 121 specialised surgical instruments, blunt and sharp, modelled on the beaks and claws of birds and animals. These were not museum curiosities. They were in common use among surgeons of the time. Sushruta is famous for two achievements:

• Rhinoplasty: restoring a mutilated nose through plastic surgery.
• Cataract surgery: removing the clouded lens from the eye with a specially designed curved needle, the Jabamukhi Salaka.

Indian medicine travelled widely. Buddhist monks carried Ayurveda to Tibet and China, and the two great treatises were translated into Arabic. Alongside Ayurveda grew two related systems:

• Siddha: a southern system nurtured by Tamil tradition, in which the use of metals, minerals and chemical products is predominant. A branch dealing with injuries is called Varmam.
• Unani: a Greek-origin system that reached India with the text Firdausu Hikmat by Ali-bin-Rabban.

In the medieval period, the 13th-century Sarangdhara Samhita emphasised the use of opium in medicine and urine examination. The Rasachikitsa system treated diseases with mineral-based medicines.

From Vedic times, the material world was held to be made of five elements, the panchmahabhootas, each linked to a sense:

• Prithvi (earth): smell.
• Agni (fire): vision.
• Maya (air): feeling.
• Apa (water): taste.
• Akasha (ether): sound.

Indian philosophers reasoned that, except for ether, these elements were made of tiny particles of matter. The smallest, indivisible unit was the Parmanu (atom). Kanada and Pakudha Katyayana, in the 6th century BC, first proposed that the world is built from atoms. This idea anticipated modern atomic theory long before John Dalton.

Chemistry in India was called Rasayan Shastra (the science of liquids). Laboratories were Rasakriya Shala and a chemist was a rasadanya. Its main areas of application were:

• Metallurgy: the smelting of metals.
• Distillation of perfumes.
• Dyes and pigments.
• Extraction of sugar.
• Production of paper.
• Gunpowder and the casting of cannons.

The great name in early chemistry is the alchemist Nagarjuna, born in Gujarat in 931 AD. His treatise Rasaratnakara dealt with the preparation of liquids, especially mercury, and with metallurgy and alchemy. It included attempts to transmute base metals into gold. He also wrote Uttaratantra, a supplement to the Sushruta Samhita on medicinal drugs. Another medieval text, Rasarnava (12th century), dealt with metallic preparations and alchemy under the banner of Tantra.

Indian metallurgy was world-class. Smelting and casting were highly developed. Two artefacts stand as proof:

• The rustless iron pillar at Mehrauli, Delhi, which has not corroded in over a thousand years.
• The huge copper idol of the Buddha at Sultanganj, Bihar, similarly rust-free.

Indians also developed Wootz steel (known as Ukku, Hindwani or Seric Iron), the prized material of the famous Damascus swords. Under the Mughals, gunpowder (saltpetre, sulphur and charcoal in varying ratios) and cannon-casting flourished. The Ain-i-Akbari even describes Akbar's "regulation of perfume office".

Sanskrit and Pali literature record a long Indian tradition of maritime activity. The key text is the Yukti Kalpa Taru, a Sanskrit treatise that describes the types of ships, their sizes and the materials used to build them. Ships were divided into two broad classes:

• Samanya: the ordinary class, used for sea voyages.
• Vishesha: the special class.

The ordinary class itself had two designs:

• Dirgha: a long, narrow hull.
• Unnata: a higher hull.

By the length and position of their cabins, ships were further classified into three types:

• Sarvamandira: cabins running the whole length of the deck, used for royal voyages and to carry horses.
• Madhyamandira: cabins in the middle of the deck, used for pleasure trips.
• Agramandira: used for warfare.

Several Sanskrit terms for the parts of a ship were tested favourites:

• Nava bandhan kilaha: the anchor.
• Vata vastra: the sail.
• Jeni pata (or karna): the rudder.
• Nava tala: the keel.
• Machayantra: the compass, the "fish machine", shaped like a fish.