When the zero degree meridian of the ancient world passed through India

  • In 1905, John Eliot director-general of Indian observatories decided that India’s meridian should be 5 hours 30 minutes east of Greenwich Meridian. Author Sahana makes a case for the Indian Meridian to pass through Ujjain.   


In school, we all learn about the Greenwich Meridian and Greenwich Mean Time. We are also informed assiduously that Greenwich is not to be pronounced as Greenwich but as Grenich. And thus, we Indians struggle with another English word that is spelled in one way and pronounced in another.

What many people do not know is that Greenwich in the United Kingdom became the zero degree longtitude of the world less than 150 years ago. Before that, for thousands of years, the prime meridian of the ancient world passed through the city of Ujjayani, now called Ujjain (also known as Avanti in ancient times) in the Indian state of Madhya Pradesh. The capital of great kings such as Vikramaditya, the grand city was an acclaimed centre of astronomical study.

The oldest text on astronomy in the world Surya Siddhanta refers to Avanti as the Prime Meridian. The text also lists Rohtak, Kurukshetra and Lanka among the places lying on the zero degree meridian. Lanka was regarded as the city at the intersection of the Equatorial line and the Prime Meridian. Today’s Sri Lanka is not the one referenced in the ancient texts according to Indian astronomers.

Surya Sidhhanta Chapter 1 -62 mentions Avanti (Ujjain) lying on the zero degree meridian. Pic courtesy author. 

Southeast Asian countries  such as Indonesia, Thailand and Cambodia followed the Surya Siddhanta in their astronomical calculations and borrowed most of the technical terminology. The zijes or astronomical books in Arabic from the medieval period also used Ujjain under the name Arin as the prime meridian, according to Dr C.K. Raju  who analysed E.S. Kennedy’s “Survey of Islamic Astronomical Tables”.

The most important landmark of Ujjain is the Mahakaleshwar Temple situated on the banks of the River Shipra. The temple contains one of the sacred lingas representing Bhagwan Shiva known as Jyotirlinga. There are 12 such sacred Jyotirlinga temples all over India but the one in Ujjain is the only one which faces South-the direction of death.

The form of Shiva housed in the Mahakaleshwar Temple is that of the Lord of Time. He rules over Time itself and a darshan of his linga at this temple is said to impart the blessing of not having to face an untimely death. Though this temple was destroyed by an army of Islam in 1234 and the Jyotirlinga was thrown in a pond nearby, it was reconstructed by Maratha general Ranoji Shinde in the 1740. Mahakaleshwar permeates the consciousness of the entire city of Ujjain and people here do not greet each other with the characteristic Namaskar but with “Jai Shri Mahakaal” or “Jai Mahakaal”.

Not far from this temple is another one Kark Rajeshwar Temple. The Tropic of Cancer is called Karka Rekha in Sanskrit. This location is known to be intersection of the zero degree longitude with the tropic of cancer. However, as I discovered later, the point of intersection has changed over the years.

Ujjain had an ancient observatory where some of the best mathematical minds came together to study the skies and carry out elaborate calculations. The mathematical ideas churned out by the brilliant scholars of Ujjain such as Varahamihira, Bhaskara I, Brahmagupta and Bhaskara II were far ahead of what European mathematicians grappled with centuries later.

Read  Renowned Mathematicians of India

Let’s consider just two of the professors who headed the observatory in different time periods-Brahmagupta (born 598 CE) and Bhaskara II (born 1114 CE).

Brahmagupta (who hailed from Rajasthan) worked on trigonometric formulae, quadratic equations, area of cyclical quadrilaterals, arithmetic progression and on improving Aryabhata’s sine tables. He explained solar eclipses in terms of shadows cast by the moon and earth. He expounded on the average and real motions of planets, the distance of the sun from celestial bodies, various planetary conjunctions and a plethora of concepts that literally caused a knowledge revolution.

Today, we take zero for granted. But, can you imagine a time when the world had no idea about the notion of zero or negative numbers? It was a huge leap of human thinking for Gurus in India to visualize zero. While Aryabhata had already used zero as a placeholder in his calculations, it is Brahmagupta of Ujjain who first treated zero as a number in its own right not merely a placeholder digit. He established the basic mathematical rules for adding zero to a number, subtracting zero from a number and multiplying zero with a number which we still use today.

The idea of zero percolated from Ujjain to Baghdad where Brahmagupta’s works translated into Persian played a path breaking role in transforming mathematics and astronomy in the Arab world. Since mathematics and astronomy were inextricably a part of Hindu Dharma, the theories and methods were categorized by the Muslims as Hindu mathematics. When the idea of zero crossed over to Europe, it met with massive resistance. In those years of Christian Crusades, any knowledge that came from Arabs, even if it be mathematics, was treated as false. In fact, zero was banned along with other Indian numerals (which they called Arab numerals) in 1299! But the Dark Ages eventually passed and Europe not only soaked in the knowledge from India that came via Arab lands, but they also found the direct route to India, one of the richest countries of the time.

Bhaskara II or Bhaskaracharya (born in Karnataka) is another phenomenal polymath who became one of the brighest jewels of Ujjain and later, via the Arabs, the world itself. His treatise Siddhantasiromani is a monumental one which is divided into four parts- Lilavati, Bijaganita, Goladhyaya and Grahaganita-each dealing with important aspects of mathematics such as algebra, spherical trigonometry, permutations and combinations, ideas of differential calculus and astronomy. According to mathematicians J.J. O’Connor and E.F. Robertson, Bhaskaracharya “reached an understanding of the number systems and solving equations, which was not to be reached in Europe for several centuries”. What’s more, he infused mathematical exercises with delightful poetry which enchanted learners so much that Lilavati was a textbook for centuries. How many mathematicians do you know today who can communicate theories and formulae through engaging poetry?

In October 2023, Indica, a non-profit focused on Indian Knowledge Systems collaborated with me to conduct a conference titled “Pedagogy and Educational Heritage of India”. We chose Ujjain as the venue in order to highlight the zero meridian of the pre-colonial world, which was also a thriving hub of educators and students intent on discovering the mysteries of the universe. It was a successful conference and many interesting papers were presented on the pedagogical tools used in ancient India for teaching dance, music, medicine, language, logic and mathematics.

Afterwards, I went on a trip to locate the zero degree meridian along with my sister. To my surprise, I learned that the actual intersection of the meridian with the Tropic of Cancer was no longer at Ujjain but at a place called Dongla, which was 30 km to the north of Ujjain. The person who discovered this was the well-known archaeologist Dr Vishnu Sridhar Wakankar (1919–1988). I was familiar with his name. The famous Bhimbetka caves from the Paleolithic and Mesolithic periods which contain exquisite paintings were discovered by Dr V.S. Wakankar in 1957. As I learned more about Dr Wakankar’s work in the next two days, I felt even more amazed at his vast contributions.

The northward shift of the Tropic of Cancer has been caused by the Obliquity of the Earth’s axis as well as a phenomenon called Axial Precession. The axis of the Earth does not remain inclined at the same angle with respect to the ecliptic as it goes around the Sun. It’s tilt changes from 22.1 to 24.5 degrees and then comes back to 22.1 degrees. Right now it is 23.5 degrees. 

In addition, the axis of the Earth itself rotates and traces a circle. If you have seen a top wobbling, you will know what the phenomenon of Axial Precession means. Hindu astronomers spent a great deal of time observing and calculating that it would take about 27,000 years to complete one precession cycle.

However, if one takes the whole cycle of Obliquity plus Axial Precession which would bring back the Earth to the position where it started then that cycle (now called Milankovitch Cycle) would take 41,000 years. The ancient Hindu texts are replete with references to the pole star and constellations visible in the night sky, which have allowed astronomers to calculate the year being referred to.

On the way to Dongla, the driver of my car stopped to talk to his relative who was waiting for him on the side of the road. I was surprised to find that the man knew all about the zero degree meridian of ancient times and its shift to Dongla. He informed me that an observatory was being built at the site.

Passing through beautiful fields, we finally reached Dongla, where I could see a Vedhshala with a variety of traditional Indian astronomical yantras on one side and several modern buildings on the other side. A shaft-like structure jutted out of the landscape and I later learned that it was a modern observatory equipped with a powerful telescope, which had been installed by the government of Madhya Pradesh.

Shri Ghanshyam Ratnani ji, the caretaker of the observatory showed us around. The great Dr V.S. Wakankar himself had taught him the principles of astronomy! Ghanshyam ji took us up the steps of the structure and we had a look at the telescope. He told us that many researchers came periodically to use the telescope for their projects. The government is planning to develop the site for tourism in the years to come.

From the second floor of the building, one could see the village landscape all around. I learned that there was a planetarium as well as auditorium. A school building stood a little distance away and I wondered if the children there were familiar with the astronomical Yantras next door.

On a two-acre plot, the Wakankar family is maintaining the yantras and also plans to build an experential centre. Ghanshyam ji took us to each of the Yantras and explained how they worked. The first one we saw was the Shanku.

Shanku Yantra.  

At that time I did not know what it was called in English but later I learned it was the gnomon. The Shanku is just a vertical staff placed over a horizontal surface. But it holds great importance in Indian astronomy and just by observing its shadow, so many astronomical and geographical readings can be determined such as the cardinal directions, time of the day, latitude, longitude of the sun and so on. It is a crying shame that modern schools do not teach children how to use the Shanku to build a fundamental understanding of astronomy.

It was fascinating for me to learn about how Dr Wakankar sent teams of people carrying a Shanku or gnomon (a basic but powerful instrument used by Indian astronomers from ancient times) to find out where the Karka Rekha (Tropic of Cancer) had shifted. At that time, Ghanshyam ji was just a 15-year old assisting Dr Wakankar!

The second yantra at the Dongla Vedshala is the Bhaskar Yantra. A hollow rod passes through the centre of a sphere which is tilted at the same angle as the actual tilt of the earth. “If you see the sky through this rod then you will see the Pole Star,” informed Ghanshyam ji. Polaris or Dhruva is the pole star to which the North Pole of the Earth points today.

“It was at this spot that Dr Wakankar stood and said I found the place I have been searching for,” said Ghanshyam ji. “He always said that we should not have Greenwich Mean Time but Mahakaal Mean Time!” Recounting how the British moved the Prime Meridian to Greenwich, Ghanshyam ji said:


They moved the meridian there but they don’t even have more than a few hours of sunlight. And when their day changes at midnight, it is still dark for them while the Sun has already risen for us here.

Ghanshyam ji narrated a delightful story of how Krishna and Sudama, in their student days had set out in search of the Karka Rekha. They studied under Rishi Sandipani at his Ashram located in Ujjain. At that time, Dongla was covered by jungles and not easily accessible therefore the duo went to a place called Narayan Dham which was at the same latitude but not on the zero degree meridian. At that place, even today two Shankus can be found which are believed to have been used by Krishna and Sudama. The story goes that the two were caught in heavy rain and took shelter under a tree.

“Remember the story of Sudama eating chana and not sharing with Krishna,” said Ghanshyam ji. “That episode happened at the time.”

I smiled to myself as I saw the endearing manner in which Ghanshyam ji was juxtaposing scientific facts with delightful stories from the Puranas just as it has always been done in Bharat. Even when he scientifically explained the Earth’s rotation, revolution and precession which caused the change in seasons, his gratitude to Bhagwan for all these phenomena was palpable.

We also saw the Bhitti Yantra which is basically a wall placed along the north-south meridian. Quadrants are inscribed on the wall with markings of degrees and minutes. This yantra is used to measure the meridian altitude or the zenith distance of an object such as the sun, moon or a planet, which can then be used to prepare the Panchanga (Hindu almanac). The structure looked very familiar because it can be seen in all the observatories built by Sawai Raja Jai Singh at Delhi, Mathura, Banaras, Ujjain and Jaipur.

The Samrat Yantra is perhaps the most imposing of all the Yantras. At Dongla it was a modest one but the one in Jantar Mantar at Jaipur is the tallest at 90 feet. We were so engrossed in listening to Ghanshyam ji that we did not click good photos. The two quadrant shaped walls projecting from the two sides with a staircase at the centre (forming the hypotenuse) give the feeling of being launched into the sky. As the Sun moves from the east to the west, its shadow on the markings of the quadrants tell the local solar time which we were told had to be corrected by 15 minutes to get the time referenced to the Greenwich time.

Yet another sun dial at Dongla also gave the time in hours and minutes with the help of the shadows cast by a gnomon. When I asked how the time could be known in ancient times if the sun was covered with clouds, Ghanshyam ji said that a sand clock was used in such situations.

Such has been the march of time that today, the grand Samrat Yantra and sun dials of the world are all replaced by wrist watches and electronic devices. I was lost in thought about the miniaturization of instruments with the advance of time but Ghanshyam ji reminded me of the huge environmental footprint that had come in the wake of all the progress in technology. Our instruments have become compact but our energy and water consumption have bloated beyond redemption.

One might wonder why we need the Yantras when we already have sophisticated astronomical instruments. I would argue that if students do not build their understanding of the universe on basic fundamentals by using the Yantras, their knowledge will be extremely superficial and incomplete. Let us say tomorrow we wake up to a world where all cooking is done only on induction stoves and microwave ovens, and people don’t know that fire can be used for cooking, would it not be a huge deficit in our understanding? Being so slavishly dependent on gadgets is taking away the connection with Nature. Should we not be trained to tell the time and season by looking at the skies and making basic measurements? After all, the movements of celestial bodies such as the Sun and Moon have direct impact on all the living beings on Earth.

A cruel twist that came in India’s history is that occupation by colonial powers downgraded its knowledge systems which had been transmitted for thousands of years through a variety of institutions such as Gurukulas, Mathas, Viharas, Ghatikas, Agraharas and Tols. In the period that the British occupied India first via the East India Company and then directly via the British monarchy, huge changes were made to the socio-economic structure of India. A policy of divide-and-rule which deepened the fault lines in society and the impoverishment of the people via draconian taxes and destruction of indigenous industry rendered a whole people powerless and voiceless. The imposition of English as a medium of instruction via the English Education Act in 1835 caused millions of Indians to be disconnected from their indigenous education systems.

In my two books on India’s educational heritage written in 2017 and 2021, I have made a strong case for recognising the knowledge that India gave to the world and for strengthening the civilizational roots of Indians today.

In 1884, when the International Meridian Conference was held in Washington, D.C., with representatives from 25 nations, there was obviously no representation from India because it was a colony of Britain. At this conference, the meridian passing through the Royal Observatory in Greenwich was voted as the Prime Meridian. Also, in 1905, the meridian passing through the east of Allahabad (now Prayagraj) was chosen as the central meridian of British India. John Eliot, a meteorologist in the service of the occupying British government of India and director-general of Indian observatories was asked by the Royal Geographic Society to choose two time zones of 5 hours and 6 hours east of Greenwich as the standard time zones of India. He decided to go for a single time zone of 5 hours 30 minutes East of Greenwich Mean Time as the most suitable from the British point of view. The British-operated railways had informed him that they did not want the inconvenience of two time zones for operating trains within the country. And thus, an arbitrary time zone was chosen for India by the British regime.

Inside Vikramaditya University, Ujjain. 

In the past decade there has been a great churning amongst Indians who are discovering their true history which is free from colonial bias. The government of India has been trying to include Indian Knowledge Systems in education. In Ujjain, I found a keen desire among the educated people to restore the status of their city as a hub of knowledge as it used to be during the times of Emperor Vikramaditya. The Government of Madhya Pradesh is actively promoting initiatives to showcase art, culture and heritage.

In a recent development, the newly appointed Chief Minister of Madhya Pradesh Shri Mohan Yadav has asserted that Ujjain should once again become the Global Prime Meridian, which has created quite a controversy in the media.

Technically, it does not matter which meridian is used as the zero degree meridian unlike the Equator which has astronomical significance. However, the importance of Ujjain in the history of astronomical observations cannot be ignored. While it is too impractical to expect the global order to accept Ujjain as a prime meridian once again, perhaps the Indian Standard Time meridian which currently passes through Mirzapur (82.5 degree East) in Uttar Pradesh can be changed to Ujjain (75.79 degrees East) in Madhya Pradesh.

It will involve a great deal of administrative pain however it will set our history right in a small way. At least, let us make the Indian meridian pass through Ujjain as a sign of respect to all those astronomers who built the foundation of astronomy and mathematics. More importantly, as friend Raj Vedam says, Ujjain must be developed into a major hub of astronomical research. Let the best astronomical minds meet again at Ujjain as they did from the times of Varahamihira.


I would like to thank Dr Vedveer Arya, Dr Raj Vedam and Shri Anil Narayanan for their critical inputs to this article.

Note: Today, the Greenwich Meridian has been replaced by the IERS Reference Meridian, which differs slightly from the historical Greenwich Meridian.

This article was first published here It has a few short videos which can be viewed by clicking on the link. Except where stated pics from esamskriti database. 

Also see albums of

1. Jantar Mantar Observatory Ujjain

2. Jantar Mantar Jaipur 

3. Read Places to see in Ujjain  

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