Heliocentricity, Aryabhata, and Indian Astronomy (Part II)

It is quite possible that the early astronomers in India and in the Arabic lands observed this effect with naked eyes. In the Indian astrology (oh, such a loaded word!) there are 27 stars. These must refer to the star constellations – as any layperson would quickly count the stars of a night sky and would conclude that there are certainly more than twenty-seven stars visible to the naked eye on any night. Modern astronomical texts put the number of constellations in the northern hemisphere at about 89; in the southern hemisphere, 35 constellations were identified. In the early history of India, the organization of knowledge was much different from what it is today. Today, to most people mathematics, astrology, poetics, astronomy, and physics are all different disciplines with well-defined boundaries. In the olden days, mathematics, poetry, physics, astronomy, and astrology used to exist in a mixed knowledge base, a sort of intellectual potpourri.  

Aryabhata I

Aryabhata (also known as Aryabhata I to distinguish from the later day mathematician Aryabhata II) was born around 475 A.D. at Kusumupura, a short distance from the present day Patna. In his lifetime, Ujjain used to be the seat of science and astronomy, a city six hundred miles away from Patna. Aryabhata10

worked in astronomy, mathematics, and perhaps a bit in physics. In his time the notions of planets, stars, sun, and astronomy were influenced by the concepts expounded in the Hindu religion. Looking from a modern perspective, one may be tempted to brush aside all the earlier concepts of Hindu religion as irrational and unscientific. But we will be startled by the uncanny correctness of some of the earlier beliefs (or concepts?). Here are some glimpses of those ancient thinkers’ insights (Again, we cannot clearly fathom how these conclusions were arrived at, what were the reasonings and what were the original experimental or observational data):

In the fifth century, Indians computed the age of earth as 4.3 billion years. Modern investigations with radioactive lead and argon give the age of earth about 4 billion years. A more accurate estimate puts the number as 4.6 billion years. The Sanskrit word for gravitation is gurutvakarshan – ‘guru’ meaning heavy (heaven). Does it indicate mass? Akarshan means attractiveness. Does it imply that the ancient investigators had a vague concept of “gravitation”? In physics, gravitational force is unique because it is always attractive. On the contrary, in electricity and magnetism both attractive and repulsive forces are observed. Or, consider the expression – “sapta-aswa-ratha-maruudha” for the sun. Is it just an allegorical way of saying that the visible white light is composed of seven colors? Or is it a poetic utterance that burst into expression upon coming across a nascent rainbow in the sky?

Aryabhata published the famous “The Aryabhatiya” in 499 A.D. The work deals with astronomy and spherical trigonometry. He was the first Indian to describe the earth as a sphere with a diameter of 7,980 miles; we now know that the equatorial diameter of earth is 7926.81 miles!

It appears that Aryabhata probably observed with naked eye (as most amateur sky watchers or astronomers do) the planets and stars and carefully recorded their motions. Perhaps, he also had access to instrumental observations and results achieved by earlier astronomers. He described the planetary motion in terms of epicycles and apsides. Almost one thousand years before Copernicus, Aryabhata postulated that the apparent sunset and sunrise are caused by the rotation of the Earth around its axis. Aryabhata also offered explanations of equinoxes (March 21 and September 22) and solstices (June 22 and December 22) due to the tilt of earth as it revolves around the sun. He calculated the Hindu calendar to consist of 365 days, six hours, twelve minutes, and thirty seconds; it is a slight overestimate. In mathematics, his contributions include right angle triangle (60°, 30°, 90°), formula for sine, formulae for square root and cube root. Aryabhata also computed an extremely accurate value for pi (π) as 3.1416. The Indian Space Research Organization (ISRO) named its first satellite as Aryabhata to commemorate this pioneering astronomer’s discoveries. 

Conclusion

Often I wondered whether the high school textbooks in India should have depicted a more accurate account of the original achievements of the earlier Indian scientists. Except a smattering of a few names such Susrita and Aryabhata, most of the science books (as I recall my high school days) completely ignored the stellar achievements of the pioneers. College textbooks (Indian) often appear to be just mirror copies of the western science books reflecting the glories of Kepler, Galileo, and Newton without any rational analysis of the earlier groundwork done by others. At a minimum, an accurate account of the early Indian scientists and mathematicians would inculcate a sense of pride and self respect in the high school students. The western tilted science curriculum coupled with the pernicious English medium (which puts regional language speaking, yet creative students at a disadvantage) produced enormous devastation in the post independent India and robbed much of the originality in the Indian science. One needs to look only at the lack of Indian Nobel laureates in science during 1947 – 2006 (notwithstanding emigrant luminaries like Drs. S. Chandrasekhar and H. G. Khorana). Books on the early mathematicians such as Aryabhata, Bhaskara, and Brahmagupta were written by a number of Indians, particularly authors well versed in Sanskrit and other Indian languages; but such works need to be brought to the level of aspiring high school and college students across all the states, in the vernacular (as well as English). 

References

1. “Conversations with Jean Piaget”, by Jean Claude Bringuier, University of Chicago Press, 1980

2a. “Lost Discoveries”, by Dick Teresi, Simon and Schuster, 2002

2b.

3. “The Act of Creation”, by Arthur Koestler, Macmillan Press, 1964

4. “The History of Physics”, by Isaac Asimov, Walker and Company, New York, 1985

5. “The Ascent of Man” by Jacob Bronowski, Little Brown, 1973

6. “Mechanics”, by J. P. Den Hartog, Dover, New York 1961, p. 307

7. “A Field Guide to the Stars and Planets”, by D. H. Menzel, Houton Miflin Company, Boston, 1964

8. “Stargazing Astronomy with a Telescope”, by Patrick Moore, Barron’s Educational Series Inc., Woodbury, New York, 1985

9. “The Telescope Handbook and Star Atlas”, by Neale E. Howard, Thomas Y. Crowell Company, New York, 1967

10. “Great Scientists”, vol. 1, edited by Frank N. Magill, Grolier Educational Corporation, Danbury, CT, 1989

☨ I completed the first draft of this article in November 2003. Later in 2005 it was published on the on-line magazine of TLCA (Telugu Literary And Cultural Association) of NY-NJ-CT. Copyright 2003, 2005, and 2021 by the author. 

Heliocentricity, Aryabhata, and Indian Astronomy

Heliocentricity, Aryabhata, and some glimpses of the Indian Astronomy☨

Introduction

Many years ago, a physicist friend posed an interesting question: Had the Indian astronomers or scientists ever pondered on the question of earth’s rotation, earth centric celestial system versus sun centric celestial system? What were their theories and findings? Or did they erroneously postulate that the earth is stationary and the planets and sun just rotate as they appear? I did not have any ready-made answers then, but averred that perhaps some the earlier Indian astronomers probably had addressed the issue at some point in Indian history. After all, one cannot naively presume that Galileo or Kepler were the only scientists to stumble on the right answers to such questions. Somehow, I could not easily accept a priori that intelligence or creativity is the prerogative of some select civilizations. Also, the traditional Indian calendars (both solar and lunar) accurately predict lunar and solar eclipses. In fact, the Hindu calendar is considered even today as perhaps the best rational system. Both Delhi and Jaipur possess astronomical observatories of a bygone era, albeit in a dilapidated condition. Thus, I heuristically intuited that perhaps one of the Indian astronomers had seriously looked into the issue of our solar system, the planets, and their periodic movements. However, I was not then certain which Indian astronomer had tackled this issue and my guess was purely based a bit on the fondness to the ancient Indian civilization and a bit on the “spirit of positivism” (to borrow a phrase from Jean Piaget1).

Elementary and advanced texts in physics and astronomy credit the hypothesis of heliocentric planetary system to Copernicus (1473 – 1543) and Galileo (1564 – 1642). Recently discovered historical evidence2a, 2b refutes this and suggests that the sun centered planetary system ideas originated in the Indian and Arabic regions much earlier, often hundreds of years earlier. Some of the well-known historians of science (ex: Arthur Koestler3, Isaac Asimov4, Jacob Bronowski5) erroneously attributed most of the important scientific discoveries and inventions to regions around Greece, ignoring all the scientific culture that originated in Indian, Chinese, Arabic, and Mayan civilizations with one stroke, which preceded the modern western civilization by hundreds, if not thousands of years. What a terrible moral lapse, historical injustice, and intellectual chicanery!  

Effects of (Relative) Motion

To appreciate the difficulties involved with the motion of astronomical bodies, first we have to understand the concept of “frame of reference”. The issue of “frame of reference” is best understood in the context of relativity. In layman’s language, this simply means that what we observe (or what is observed by an instrument) depends on where we are located. One need not invoke the esoteric concepts of relativity (i.e., Einstein’s). The essential ideas about (moving) frames of reference can be gleamed from the common day-to-day experiences. For example, most children notice that while traveling in a train or car the close-by trees on the roadside appear moving away. To a child, the moon and the sun certainly appear moving from east to west. Our visual clues, bodily balance, and senses are conditioned or accustomed to earth’s gravity and earth’s diurnal and annual rotations. Unless we are up in the space and that too on a properly designed laboratory pedestal (in physics lingo, it is called a “frame”), we would not able to see clearly the daily and yearly rotations of our planet earth. The modern space exploration and space vehicles were not available to the early astronomers; they had to contend with the limitation of being tied to the moving frame of earth. Still, they had to decipher the solar system, stars, and the lunar and solar eclipses with precision and postulate a model for all the wonders of our planetary system. Verily, it must have been a stupendous task! 

Periodicity

Only the day and night events have the periodicity of 12/24 hour cycles. All other events with longer-term periodic effects cannot be accounted by the simple notion that the sun rotates around the earth. How do we account for the fact that the seasons of spring, summer, and winter occur with regularity that approximates to twelve months rather than 24 hours? Also, many ancient observers or astronomers very likely observed that the stars and some of the nearby planets apparently move in certain pre-determined paths and their positions with respect to earth follows set patterns that retrace periodically. Again, all these observations are difficult to be explained away with a simple hypothesis that everything goes around our “home planet earth”. One can reasonably suppose that these questions surely haunted the early astronomers and physicists in India and other ancient cultures.

Some Clues and Observations

How can we detect that the earth is rotating? Are there some easy experiments or observations that can intimate the motion of earth? For example, it is observed that the cyclones in the North and South have different directions of rotation (clockwise or counter clockwise). This is due to the Coriolis effect, which arises due to the spinning of earth along the North-South vertical axis. The photographs of cyclones with their clear rotation are possible only with modern satellites, balloons, or highflying airplanes. Spinning of the earth can also be observed inside a building by setting up a Foucault’s (1819 – 1868) pendulum. The Coriolis effect is also observed in the flowing river waters; it is observed that one of the banks is eroded more than the other in rivers located in the Northern hemisphere. The effect can be noticed with the motion of a projectile or the drop of a stone in deep mines6. It is not certain whether such effects were ever observed by the early Indian scientists or astronomers in mines (ex: Kolar gold mines, depth approx. 10,000 ft.). We can visually see the earth’s spinning and rotation by watching the night sky7-9. Suppose we leave a camera on a tripod stand focused or aligned along the pole star and leave the shutter open for 10 -30 minutes. What we find on the film is a set of arcs (known as star trails) all arranged as parts of concentric circles; these arcs represent the stars and their (apparent) circular motion as observed by the earth bound viewer. 

(to be Contd.) Copyright 2003, 2005, 2021 by the author