Astronomy in ancient India — Aryabhata, Varahamihira, Brahmagupta and the origins of Indian sky observation
EDISLA · Astronomy Heritage Series
India Looked Up First — The Extraordinary Astronomical Heritage of a Civilisation
Fifteen hundred years before Galileo turned his spyglass toward the heavens, Indian mathematicians were calculating the Earth's circumference, predicting eclipses to the minute, and building observatories of stone and brass that still work today. This is their story — and an invitation to continue it.
There is a verse in the Aryabhatiya, written in 499 CE, that states with quiet certainty: the Earth rotates on its own axis, the stars do not move, and what appears to be their motion is an illusion caused by the spinning of the ground beneath our feet. The man who wrote it, Aryabhata, was 23 years old. He lived in Kusumapura — present-day Patna — and he arrived at this conclusion not with a telescope, not with modern instrumentation, but with mathematics, observation, and a mind of extraordinary clarity.
This post is about that mind, and the minds that followed it. About Brahmagupta, who solved equations in the seventh century that Europe would not understand for another thousand years. About Varahamihira, who synthesised five schools of astronomical thought into a single masterwork. About Sawai Jai Singh II, who built open-air observatories of monumental scale that you can still visit today. And about the skies themselves — the same stars that these scholars mapped, calculated, and named, still visible above every Indian city, town, and village every clear night.
You don't need a ₹5 lakh telescope to connect with this heritage. You need only to look up.
The Lineage — 3,000 years of Indian sky science
~1500 BCE
Vedanga Jyotisha — the first systematic Indian astronomy
The Vedanga Jyotisha, an auxiliary text of the Vedas, establishes the earliest systematic Indian astronomical calendar. It divides the sky into 27 nakshatras (lunar mansions), calculates the synodic months, and predicts the timing of religious ceremonies by solar and lunar position. Indian astronomy is born not as pure science but as a sacred practical necessity — the stars govern when to plant, when to harvest, when to perform the rituals that sustain cosmic order.
~400–200 BCE
Siddhantas — five schools of astronomical calculation emerge
The five Siddhantas (literally "established doctrines") form the classical framework of Indian astronomy: Pitamaha, Vasishtha, Romaka, Paulisa, and Surya Siddhantas. Each school has its own methods for calculating planetary positions, eclipses, and the lengths of days and years. The Surya Siddhanta, attributed to the Sun god Surya himself in legend, contains geometrical and trigonometric methods of remarkable accuracy. It would influence Indian astronomy for the next two millennia.
476 CE
Aryabhata born — mathematics meets the sky
The most celebrated name in Indian astronomy is born in Kusumapura. By 23, he will have written the Aryabhatiya — 118 verses that correctly identify Earth's rotation, calculate its circumference to within 0.2% of the correct value, give a value of pi accurate to four decimal places, and describe the orbital periods of the planets with extraordinary precision. His eclipse calculations would allow predictions accurate to within minutes.
505 CE
Varahamihira — the astronomer who synthesised a civilisation
Varahamihira of Ujjain writes the Pancha-Siddhantika — a synthesis of all five Siddhanta schools — and the Brihat Samhita, an encyclopedic work covering astronomy, astrology, meteorology, architecture, agriculture, and the interpretation of natural phenomena. He is the first Indian scholar to acknowledge Greek astronomical influences explicitly, and the first to systematically cross-reference them with native Indian calculations.
598 CE
Brahmagupta born — the rules that govern the universe
Born in Bhinmal (modern Rajasthan), Brahmagupta will write the Brahmasphutasiddhanta at age 30 — a foundational text that introduces the formal rules of arithmetic with zero and negative numbers, solves indeterminate quadratic equations, and calculates the length of the solar year at 365 days, 6 hours, 12 minutes and 9 seconds. Modern value: 365 days, 5 hours, 48 minutes and 46 seconds. His error: 23 minutes and 23 seconds, over thirteen centuries ago, without any instrument more sophisticated than the naked eye and mathematics.
1114 CE
Bhaskaracharya II — the astronomer-poet of Bijapur
Bhaskaracharya's Siddhanta Shiromani contains four parts: Lilavati (arithmetic), Bijaganita (algebra), Ganitadhyaya, and Goladhyaya (astronomy and spherical geometry). His Goladhyaya calculates the Earth's circumference, derives the formula for the differential of a sine function (anticipating calculus by 500 years), and describes the gravitational attraction of the Earth in qualitative terms centuries before Newton's formulation.
1727–1734 CE
Sawai Jai Singh II — stone and brass on a monumental scale
Maharaja Sawai Jai Singh II of Jaipur constructs five Jantar Mantar observatories — at Jaipur, Delhi, Varanasi, Ujjain, and Mathura — as instruments of astronomical precision at architectural scale. The Samrat Yantra at Jaipur, a 27-metre-tall sundial, reads local time accurate to two seconds. These are not ceremonial monuments. They are working scientific instruments, still capable of accurate solar and lunar observations today.
Aryabhata — the first modern mind
BORN 476 CE
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Aryabhata
476–550 CE · Kusumapura (Patna, Bihar)
Aryabhata wrote the Aryabhatiya in Sanskrit verse at the age of 23 — one of the earliest known astronomical texts in the world to correctly describe the Earth's axial rotation. In a civilisation that largely accepted a geocentric, stationary Earth, this was an act of extraordinary intellectual courage. He calculated the length of the sidereal year as 365 days, 6 hours, 12 minutes and 30 seconds. Modern value: 365 days, 6 hours, 9 minutes and 10 seconds. His error: 3 minutes and 20 seconds. He derived a value of pi (π) as approximately 3.1416 — accurate to four decimal places — and stated explicitly that this was an approximation. He explained solar and lunar eclipses as the shadow of the Earth and Moon respectively, rejecting the popular mythological explanation of a demon Rahu swallowing the luminaries.
Earth rotates on its axisSolar year calculated to 3 min accuracyπ ≈ 3.1416Eclipse shadow theoryTrigonometric sine table
"Just as a man in a boat moving forward sees the stationary objects as moving backward, so at Lanka, the stationary stars are seen moving westward."
Aryabhata explaining Earth's rotation through the analogy of a moving boat — the stars do not move; we do.
Aryabhatiya, Gola section, 499 CE
What makes Aryabhata extraordinary is not merely that he was correct — it is that he was correct in opposition to the prevailing cosmology of his time. The conventional view held the Earth stationary at the centre of the universe, with the Sun and planets revolving around it. Aryabhata knew this was wrong, said so in verse, and gave the correct explanation in a metaphor of such clarity that it requires no translation across fifteen centuries: you are moving, not the stars.
What Aryabhata calculated — and what you can verify tonight
The Moon's illumination comes from the Sun
Aryabhata wrote: "The Moon consists of water, the Sun of fire, the Earth of earth, and the Earth's shadow is the cause of the eclipse." He understood that the Moon shines by reflected sunlight — not by its own luminosity. You can verify this yourself with any telescope on a clear night. Watch the terminator — the boundary between the Moon's lit and dark sides — and you will see exactly what Aryabhata described: the Sun's light falling on an irregular rocky surface, casting shadows in craters that make them visible in three dimensions.
Varahamihira — the man who knew everything
~505 CE
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Varahamihira
~505–587 CE · Ujjain, Madhya Pradesh
Varahamihira of Ujjain was the polymath of classical Indian astronomy — a mind that ranged across the entirety of natural knowledge available to him. His Pancha-Siddhantika summarised the five schools of Indian astronomical thought with critical comparison, preserving astronomical knowledge that would otherwise have been lost. His encyclopedic Brihat Samhita covered meteorology (predicting rain from cloud formations, wind directions, and animal behaviour), earthquakes, comets, architectural orientation by solar direction, agricultural timing by stellar events, and the behaviour of plants in relation to celestial cycles. He was, in the most literal sense, a scientist of the natural world — a man who believed that the sky and the Earth formed a single interconnected system, and that understanding one illuminated the other.
Pancha-Siddhantika — synthesis of 5 schoolsComet catalogue and periodicityMeteorological prediction systemsSeismic precursor observationsBrihat Jataka — systematic astrology
Varahamihira's description of comets in the Brihat Samhita remains remarkable. He catalogued 101 types of comets, described their orbital characteristics (though not in modern terms), and noted that some comets recur on predictable timescales. European astronomy would not develop systematic comet observation until Tycho Brahe in the 16th century. Varahamihira preceded him by a thousand years.
He was also the first Indian astronomer to explicitly acknowledge and incorporate Greek astronomical influences — specifically the works of Hipparchus and the Hellenistic astronomical tradition that arrived in India via the Yavana ("Greek") texts. Varahamihira's greatness lies partly in this intellectual openness: he took what was useful from every tradition and synthesised it into something larger than any single source.
"The sky is the teacher of time. Its movements do not deceive; only our reading of them can err." — attributed to the tradition of Varahamihira
Brahmagupta — the man who found zero and weighed the universe
BORN 598 CE
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Brahmagupta
598–668 CE · Bhinmal, Rajasthan
Brahmagupta's Brahmasphutasiddhanta, written in 628 CE when he was 30 years old, is one of the most consequential scientific texts in human history — yet it is largely unknown outside specialist scholarship. In it, he establishes the formal arithmetic rules for zero (a number, not merely an absence) and negative numbers (debts, not merely absences of assets). He solves the Pell equation — a class of indeterminate quadratic equations — centuries before European mathematicians even formulated the problem. He calculates the circumference of the Earth as 36,000 km (modern value: 40,075 km — an error of 10%). And he computes the length of the solar year as 365 days, 6 hours, 12 minutes and 9 seconds.
Rules of arithmetic with zeroNegative number arithmeticSolar year to 23-min accuracyEarth's gravity described qualitativelyPell equation solved
Brahmagupta on gravity — 1,000 years before Newton
"The Earth, owing to its nature, pulls things downward"
In the Brahmasphutasiddhanta, Brahmagupta wrote: "Bodies fall toward the Earth as it is in the nature of the Earth to attract bodies." This is not Newton's inverse-square law — it is a qualitative description, not a mathematical one. But it is an explicit, confident statement that the Earth attracts objects toward itself as a fundamental property of its nature. Written in 628 CE. Isaac Newton's Principia was published in 1687 CE. The gap between Brahmagupta's intuition and Newton's mathematical formulation is 1,059 years.
Brahmagupta disagreed sharply with Aryabhata on the Earth's rotation — he maintained the conventional geocentric view that the Earth was stationary. Even the greatest minds are constrained by the paradigms of their age. Yet his disagreements with Aryabhata were formulated with precise counter-arguments, methodological rigour, and mathematical evidence. He was wrong about Earth's rotation and right about the nature of gravity, zero, and the solar year. The history of science is largely the history of brilliant people being partially right.
Jantar Mantar — when astronomy became architecture
In 1727, Maharaja Sawai Jai Singh II of Jaipur — a king who was also a mathematician, astronomer, and diplomat — began constructing the most ambitious network of astronomical observatories the world had ever seen. He built five of them: at Jaipur, Delhi, Varanasi, Ujjain, and Mathura. The name "Jantar Mantar" derives from the Sanskrit yantra mantra — "calculation instrument."
These were not decorative monuments. They were precision scientific instruments at architectural scale, designed to measure solar time, predict eclipses, track the positions of stars and planets, and calculate the declination of the Sun throughout the year. And they worked. The Samrat Yantra at Jaipur — a right-triangle sundial 27 metres tall — can read the local solar time accurate to within two seconds. It is still used today.
Jaipur — the flagship
BUILT 1727–1734 · UNESCO World Heritage Site
The largest of the five observatories, containing 19 astronomical instruments. The Samrat Yantra — a 27m-tall gnomon — casts a shadow that moves 6mm per second, allowing time measurement accurate to 2 seconds. The Jai Prakash Yantra (a pair of hemispherical bowls marked with coordinates) allows simultaneous day and night observations of the Sun, Moon, and planets. The Rashivalaya Yantra — twelve instruments representing the twelve zodiac signs — allows planetary declination calculations.
The Delhi Jantar Mantar, built before Jaipur, is the oldest of the five surviving observatories. Its Samrat Yantra is smaller than Jaipur's but functionally identical. The Misra Yantra at Delhi is the only instrument designed to show the noon hour at various longitudes simultaneously — effectively an early attempt at a world time standard. The observatory fell into disuse in the 19th century but was restored to functioning condition and remains accessible in the heart of central Delhi.
Jai Singh built the Varanasi observatory on the Man Mandir Ghat above the Ganges — the only Jantar Mantar with a river view. Smaller than Jaipur but architecturally integrated into the ghat's terraced structure. The instruments here were used for the precise calculation of the Hindu festival calendar — dates for Diwali, Holi, Dussehra and other celebrations were determined by observations made at this observatory.
Ujjain holds a unique place in Indian astronomical history: the Ujjain meridian (75.78°E) served as the prime meridian of Indian astronomy for centuries before Greenwich was established. The ancient Surya Siddhanta placed its reference longitude at Ujjain. Jai Singh chose to build here precisely because of this heritage, creating a deliberate link between the classical Siddhanta tradition and his own observatory programme. The Vedha Shala at Ujjain is still an active astronomical facility, operated by the state government.
The Jantar Mantars were built not because Jai Singh lacked access to European telescopes — he owned several, gifted by the Portuguese. He believed, rightly, that large fixed instruments made of stone and brass would achieve greater positional accuracy than small handheld telescopes for the specific purpose of measuring the Sun and planets' positions to high precision. He was correct for that application: the Samrat Yantra's shadow moves measurably in two seconds, allowing time measurement that no 18th-century handheld telescope could match.
— Context on Jai Singh's instrument philosophy
The thread that connects them to you
Every calculation Aryabhata made in 499 CE was a calculation about light — about the light of the Sun reflecting off the Moon, about the shadow of the Earth crossing the face of the Moon during an eclipse, about the motion of Venus as it moved between us and the Sun. He was calculating the behaviour of photons, had the concept existed. He was doing physics with mathematics because mathematics was the only instrument he had.
Every observation Varahamihira recorded was an observation through the same atmospheric column you look through tonight. The same turbulence that blurs your view of Jupiter through an eyepiece on a hot summer night blurred his view of the same planet through his unaided eye fifteen centuries ago.
Every instrument Jai Singh built at his five Jantar Mantars was an instrument for doing what you do when you point a telescope at the sky: measuring the precise angle between a celestial object and the horizon, calculating when it will return, understanding the rhythm of the universe.
The lineage is unbroken. The sky above India has not changed. The light that fell on Aryabhata's eyes in Patna in 499 CE is the same light — scattered, reflected, and transmitted across fifteen centuries — that falls through your eyepiece tonight.
See what they saw — the sky objects of Indian astronomical heritage
The celestial objects studied by India's greatest astronomers are visible from any Indian location on clear nights. Here is what each scholar focused on — and how to see it yourself with a modern telescope.
Aryabhata · 499 CE
The Moon's surface
Aryabhata used lunar observations to calculate the Moon's orbital period to within 0.001% accuracy. He described the Moon as spherical, shining by reflected sunlight, and casting a shadow that causes solar eclipses. With a 114mm+ telescope at 100×, the terminator reveals the same craters he was calculating. Try Meade EclipseView 114mm on any moonlit night.
Brahmagupta · 628 CE
Jupiter and Saturn
Brahmagupta calculated Jupiter's synodic period as 398.89 days (modern value: 398.88 days — error: 0.01 days). Saturn's at 378.09 days (modern: 378.09). These values were computed purely through mathematical analysis of naked-eye observations. Through a Bresser 6" Dobsonian at 150×, Jupiter's cloud bands and Saturn's Cassini Division are visible — the same planets, now seen in detail he could only imagine.
Varahamihira · 550 CE
The Nakshatra star fields
Varahamihira's Brihat Samhita catalogues 27 nakshatras — lunar mansions that divide the zodiac into Indian constellations. Each nakshatra is anchored on a principal star: Rohini (Aldebaran), Jyestha (Antares), Chitra (Spica). With binoculars or a small telescope, every nakshatra star is a brilliant, accessible target. The Athlon Midas G2 UHD 8×42 reveals the star colours Varahamihira categorised.
Jai Singh II · 1734 CE
Solar declination and time
The Samrat Yantra at Jaipur reads the Sun's hour angle and declination — the same measurements that define our understanding of seasons and solar time. With the Meade EclipseView 82mm with solar filter, you can observe the same Sun Jai Singh measured — tracking sunspots across the disc over days, observing the solar limb, noting the same seasonal change in the Sun's altitude that his 27-metre Samrat Yantra tracked at 2-second precision.
Visit the observatories — all five are open to the public
All four surviving Jantar Mantar observatories are open to visitors. Jaipur's is a UNESCO World Heritage Site with excellent interpretive facilities. Delhi's sits in the shadow of Parliament House. Varanasi's overlooks the Ganges ghats. Ujjain's is still an active astronomical facility. A visit to any of them — ideally around the winter solstice or summer solstice when the Sun's shadow movements are most dramatic — is one of the finest experiences available to any Indian astronomy enthusiast.
Jaipur Jantar Mantar
Jaipur, Rajasthan · UNESCO Heritage
Open daily 9 AM–4:30 PM
Delhi Jantar Mantar
New Delhi · Near Parliament
Open daily 9 AM–5 PM
Varanasi Jantar Mantar
Man Mandir Ghat, Varanasi
Open daily
Ujjain Vedha Shala
Ujjain, Madhya Pradesh
Active observatory
Vainu Bappu Observatory
Kavalur, Javadi Hills, Tamil Nadu
Free Saturday sessions 7–10 PM
Indian Institute of Astrophysics
Kodaikanal Solar Observatory
Open for guided visits
Bring a telescope to Jaipur: Visiting the Jantar Mantar during the day and then setting up your own telescope in the outskirts of Jaipur at night is one of the most meaningful astronomy experiences available in India. You will stand in the same tradition of observation — separated by 300 years and the entire history of optical astronomy — and look at the same sky.
Continue the tradition — your telescope, their sky
Aryabhata calculated the diameter of the Moon — 216 yojanas, which converts to approximately 3,375 km, against the modern value of 3,474 km — without ever seeing its surface. He inferred it from geometry, from the mathematics of shadows and orbital periods. His accuracy was extraordinary. But there is something he never experienced, something that no Indian astronomer before Galileo's era ever experienced: the actual sight of the Moon's surface at magnification.
The craters that Aryabhata calculated from orbital mechanics are visible through any telescope above 60mm aperture. The mountains his shadow geometry implied are real, rugged, and spectacular at 100× magnification. The planets whose synodic periods Brahmagupta computed to within minutes — Jupiter, Saturn, Mars, Venus — show actual detail: cloud bands, ring systems, polar ice caps, the phases of Venus that proved the heliocentric solar system.
What Aryabhata knew mathematically, you can see directly. What Brahmagupta inferred, you can verify in an evening. What Jai Singh measured with a 27-metre stone instrument, you can match with a 114mm mirror and a clear night.
India's astronomical heritage is not a historical artefact. It is an active invitation. The sky above Patna, above Ujjain, above Jaipur, above Chennai and Bengaluru and Mumbai is the same sky they worked under. The questions they asked — what is the Moon? what moves the planets? what is the distance to the stars? — are still being asked, still being partially answered, still pulling human curiosity upward.
All you need is to look up.
Start your own tradition — telescopes from EDISLA
EDISLA is India's specialist astronomy retailer, based in Chennai, serving 1,500+ Indian observers. Every telescope we recommend below connects you directly to the celestial objects India's greatest astronomers studied — now visible in the detail they never had access to.
EDISLA Astra 114 — See what Aryabhata calculated
India's #1 rated beginner telescope. 114mm aperture, Dobsonian mount — ready in 2 minutes. Shows the Moon's craters Aryabhata described, Jupiter's moons Brahmagupta tracked, and Saturn's rings in sharp detail. 4.9/5 from 1,500+ Indian customers.
Bresser 8" Dobsonian — The full deep-sky catalogue
203mm aperture. Galaxies, nebulae, and globular clusters that Varahamihira could only speculate about. The Orion Nebula resolves into individual stars at its heart. The Andromeda Galaxy shows its dust lanes. India's best visual telescope per rupee.
Meade EclipseView 82mm — Observe the Sun Jai Singh measured
The Samrat Yantra measured the Sun's declination daily. You can observe the same Sun — its sunspots, its slow drift across the sky, its corona during eclipses — with the Meade EclipseView's built-in solar filter. Safe, beautiful, and India's best value solar telescope.
Aryabhata (476–550 CE) correctly identified that the Earth rotates on its own axis — explaining the apparent westward motion of stars as an effect of Earth's rotation. He calculated the length of the sidereal year to within 3 minutes and 20 seconds of the modern value, gave an accurate value for π (3.1416), developed a trigonometric sine table, and correctly explained solar and lunar eclipses as shadow phenomena — rejecting the mythological explanation of a demon consuming the Sun or Moon.
What is the Jantar Mantar and can you still visit it?
The Jantar Mantars are a network of five astronomical observatories built by Maharaja Sawai Jai Singh II between 1724 and 1734 at Jaipur, Delhi, Varanasi, Ujjain, and Mathura. They contain large-scale stone and brass instruments for measuring solar time, predicting eclipses, and tracking planetary positions. The Jaipur Jantar Mantar is a UNESCO World Heritage Site. All four surviving observatories (Jaipur, Delhi, Varanasi, Ujjain) are open to the public. The Samrat Yantra at Jaipur is still accurate to within 2 seconds for local solar time measurement.
What did Brahmagupta contribute to astronomy?
Brahmagupta (598–668 CE) calculated the length of the solar year as 365 days, 6 hours, 12 minutes and 9 seconds — an error of approximately 23 minutes from the modern value. He described the Earth's gravity as a fundamental attracting property of the Earth centuries before Newton's mathematical formulation. He established formal arithmetic rules for zero and negative numbers in the Brahmasphutasiddhanta (628 CE) — work that was transmitted to the Islamic world and eventually to Europe, forming the foundation of modern mathematics.
Did ancient Indians know the Earth was round?
Yes. Indian astronomers from Aryabhata onward calculated the circumference of the spherical Earth with considerable accuracy. Aryabhata (499 CE) calculated Earth's circumference as approximately 39,968 km — within 0.2% of the modern value of 40,075 km. Brahmagupta calculated it as 36,000 km (an error of approximately 10%). Both calculations assumed a spherical Earth as a given, not as a hypothesis. The idea that medieval Indian (or European) scholars believed in a flat Earth is a modern misconception.
How can I continue India's astronomical tradition with a modern telescope?
The celestial objects studied by India's classical astronomers are visible from every Indian city, town, and village on clear nights. The Moon's surface (which Aryabhata described), Jupiter and Saturn (whose orbital periods Brahmagupta calculated), and the nakshatra star fields (catalogued by Varahamihira) are all observable with a telescope from ₹5,999 upward. EDISLA (edisla.in) stocks India's best range of telescopes for every budget, with free pan-India shipping and WhatsApp setup support from our Chennai team.
India's astronomical heritage continues — one clear night at a time.
