Ten Ancient Indian Scientists Of Repute – Part II

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(SP Turaga)

  1. BHASKARACHARYA II

(1114-1183 CE)

Bhaskara (1114 – 1185) (also known as Bhaskara II and Bhaskara Achārya (“Bhaskara the teacher”)) was an Indian mathematician and astronomer. He was born near Bijjada Bida (in present day Bijapur district, Karnataka state, South India) into the Deshastha Brahmin family. Bhaskara was head of an astronomical observatory at Ujjain, the leading mathematical centre of ancient India. His predecessors in this post had included both the noted Indian mathematician Brahmagupta (598–c. 665) and Varahamihira. He lived in the Sahyadri region of Western Mahrastra.

It has been recorded that his great-great-great-grandfather held a hereditary post as a court scholar, as did his son and other descendants. His father Mahesvara was as an astrologer, who taught him mathematics, which he later passed on to his son Loksamudra. Loksamudra’s son helped to set up a school in 1207 for the study of Bhāskara’s writings.

Bhaskara and his works represent a significant contribution to mathematical and astronomical knowledge in the 12th century. His main works were the Lilavati (dealing with arithmetic), Bijaganita (Algebra) and Siddhanta Shiromani (written in 1150) which consists of two parts: Goladhyaya (sphere) and Grahaganita (mathematics of the planets).

His book on arithmetic is the source of interesting legends that assert that it was written for his daughter, Lilavati. In one of these stories, which is found in a Persian translation of Lilavati, Bhaskara II studied Lilavati’s horoscope and predicted that her husband would die soon after the marriage if the marriage did not take place at a particular time. To alert his daughter at the correct time, he placed a cup with a small hole at the bottom of the vessel filled with water, arranged so that the cup would sink at the beginning of the propitious hour. He put the device in a room with a warning to Lilavati to not go near it. In her curiosity though, she went to look at the device and a pearl from her nose ring accidentally dropped into it, thus upsetting it. The marriage took place at wrong time and she was widowed soon.

Bhaskaracharya had made great contributions in various fields of mathematics. Bhaskaracharya or Bhaskara II is regarded almost without question as the greatest Hindu mathematician of all time and his contribution to not just Indian, but world mathematics is undeniable. As L Gurjar states:

…Because of his work India gave a definite ‘quota’ to the forward world march of the science. [LG, P 104]

Born in 1114 AD (in Vijayapura, he belonged to Bijjada Bida) he became head of the Ujjain school of mathematical astronomy (Varahamihira and Brahmagupta had helped to found this school or at least ‘build it up’). There is some confusion amongst the texts I have referred to as to the works that he wrote. C Srinivasiengar claims he wrote Siddhanta Shiromani in 1150 AD, which contained four sections:

1) Lilavati (arithmetic)

2) Bijaganita (algebra)

3) Goladhyaya (sphere/celestial globe)

4) Grahaganita (mathematics of the planets)

E Robertson and J O’Connor claim that he wrote 6 works, 1), 2) and SS (which contained two sections) and three further astronomical works, including two commentaries on the SS.

G Joseph claims his mathematically significant works were 1), 2), and SS (which indeed he wrote in 1150 and is a highly influential astronomical work). S Sinha however agrees with C Srinivasiengar that Lilavati was a section (chapter) of the SS, and thus I will agree with the respected Indian historians.

Lilavati (or Lilavati, there is a charming if unlikely story regarding the origin of the name of this work) is divided into 13 chapters (possibly by later scribes) and covers many branches of mathematics, arithmetic, algebra, geometry, and a little trigonometry and mensuration. More specifically the contents include:

  • Definitions
  • Properties of zero (including division).
  • Further extensive numerical work, including use of negative numbers and surds.
  • Estimation ofp.
  • Arithmetical terms, methods of multiplication, squaring, inverse rule of three, plus rules of 5, 7 and 9.
  • Problems involving interest
  • Arithmetical and geometrical progressions
  • Plane geometry.
  • Solid geometry.
  • Indeterminate equations (Kuttaka), integer solutions (first and second order) His contributions to this topic are among his most important, the rules he gives are (in effect) the same as those given by the renaissance European mathematicians (17th Century) yet his work was of 12th Method of solving was an improvement of the methods found in the work of Aryabhatta and subsequent mathematicians.
  • Shadow of the gnomon.

The Lilavati is written in poetic form with a prose commentary and Bhaskara acknowledges that he has condensed the works of Brahmagupta, Sridhara (and Padmanabha).

However, his work is outstanding for its systemization, improved methods and the new topics that he has introduced. Furthermore, the Lilavati contained excellent recreative problems and it is thought that Bhāskara’s intention may have been that a student of ‘Lilavati‘ should concern himself with the mechanical application of the method. A student of ‘Bijaganita‘ should however concern himself with the theory underlying the method.

His work Bijaganita is effectively a treatise on algebra and contains the following topics:

  • Positive and negative numbers.
  • The ‘unknown’.
  • Simple equations (indeterminate of second, third and fourth degree).
  • Simple equations with more than one unknown.
  • Indeterminate quadratic equations (of the type ax2 + b = y2).
  • Quadratic equations.
  • Quadratic equations with more than one unknown.
  • Operations with products of several unknowns.

Bhaskara derived a cyclic, ‘Cakraval‘ method for solving equations of the form ax2 + bx + c = y, which is usually attributed to William Brouncker who ‘rediscovered’ it around 1657. Bhāskara’s method for finding the solutions of the problem Nx2 + 1 = y2 (so called “Pell’s equation”) is of considerable interest and importance.

His work the Siddhanta Shiromani is an astronomical treatise and contains many theories not found in earlier works. There is not a large mathematical content but of particular interest are several results in trigonometry and calculus that are found in the work. These include results of differential and integral calculus.

Bhaskara is though to be the first to show that: sin x = cos x x

Evidence suggests Bhaskara was fully acquainted with the principle of differential calculus, and that his research were in no way inferior to Newton’s, asides the fact that it seems he did not understand the utility of his researches, and thus historians of mathematics generally neglect his outstanding achievement, which is extremely regrettable. Bhaskara also goes deeper into the ‘differential calculus’ and suggests the differential coefficient vanishes at an extreme value of the function, indicating knowledge of the concept of ‘infinitesimals’

He also gives the (now) well known results for sin (a + b) and sin (ab). There is also evidence of an early form of Rolle’s Theorem.

if f(a) = f(b) = 0 then f ‘(x) = 0 for some x with a < x< b, in Bhāskara’s work.

There have been several unscrupulous attempts to argue that there are traces of Diophantine influence in Bhāskara’s work, but this once again seems like an attempt by European scholars to claim European influence on (all) the great works of mathematics. These claims should be ignored. Particularly in the field of algebra, Diophantus only looked at specific cases and did not achieve the general methods of the Indians. (To be concluded)  (The author is a reputed scientists who was associated with ONGC as senior chemist.  Now he resides in US)

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