Lalla 

Born: about 720 in India Died: about
790 in India Lalla's father was Trivikrama Bhatta
and Trivikrama's father, Lalla's paternal grandfather, was named
Samba. Lalla was an Indian astronomer and mathematician who followed
the tradition of Aryabhata I. Lalla's most famous work was entitled
Shishyadhividdhidatantra. This major treatise was in two volumes. The
first volume, On the computation of the positions of the planets, was
in thirteen chapters and covered topics such as: mean longitudes of
the planets; true longitudes of the planets; the three problems of
diurnal rotation; lunar eclipses; solar eclipses; syzygies; risings
and settings; the shadow of the moon; the moon's crescent;
conjunctions of the planets with each other; conjunctions of the
planets with the fixed stars; the patas of the moon and sun, and a
final chapter in the first volume which forms a conclusion.
The second volume was On the sphere. In this volume Lalla
examined topics such as: graphical representation; the celestial
sphere; the principle of mean motion; the terrestrial sphere; motions
and stations of the planets; geography; erroneous knowledge;
instruments; and finally selected problems.
In Shishyadhividdhidatantra Lalla uses Sanskrit numerical symbols.
Ifrah writes in [2]: ... over the
centuries, Sanskrit has lent itself admirably to the rules of prosody
and versification. This explains why Indian astronomers [like Lalla]
favoured the use of Sanskrit numerical symbols, based on a complex
symbolism which was extraordinarily fertile and sophisticated,
possessing as it did an almost limitless choice of synonyms.
Despite writing the most famous treatise giving the views
of Aryabhata I, Lalla did not accept his theory given in the
Aryabhatiya that the earth rotated. Lalla argues in his commentary,
like many other Indian astronomers before him such as Varahamihira
and Brahmagupta, that if the earth rotated then the speed would have
to be such that one would have to ask how do the bees or birds flying
in the sky come back to their nests? In fact Lalla misinterpreted
some of Aryabhata I's statements about the rotating earth. One has to
assume that the idea appeared so impossible to him that he just could
not appreciate Aryabhata I's arguments. As Chatterjee writes in [3],
Lalla in his commentary: ... did not
interpret the relevant verses in the way meant by Aryabhata I.
Astrology at this time was based on astronomical tables and
often the horoscopes allow one to identify the tables used. Some
Arabic horoscopes were based on astronomical tables calculated in
India. The most frequently used tables were by Aryabhata I. Lalla
improved on these tables and he produced a set of corrections for the
Moon's longitude. One aspect of Aryabhata I's work which Lalla did
follow was his value of p. Lalla uses p = 62832/20000, i.e. p =
3.1416 which is a value correct to the fourth decimal place.
Lalla also wrote a commentary on Khandakhadyaka, a work of
Brahmagupta. Lalla's commentary has not survived but there is another
work on astrology by Lalla which has survived, namely the
Jyotisaratnakosa. This was a very popular work which was the main one
on the subject in India for around 300 years.
Article by: J J O'Connor and E F Robertson
Source: www.history.mcs.standrews.ac.uk/Mathematicians



