|
Jyotisha
in common parlance today is used to mean 'predictive astrology; but, in
ancient India it was used as a synonym for Astronomy, of which
Mathematics was a part.
Why did ancient
Indians study celestial objects?That part of the Vedas, called Purva
Mimamsa,
deals mainly with the performance of yagnas (sacrifices).
The time of the sacrifice always had to be precisely fixed, and days in
the Vedic period were reckoned in terms of the nakshatras
(stars). To perform sacrifices knowledgeably, it was important to be
conversant with time and direction. It was imperative, therefore, that Jyotisha,
or the study of the motion of celestial objects, was properly
understood.
For us, today, it is important to know
about
astronomy in ancient India so as to appreciate the Indian approach to
Science and the remarkable achievements of our astronomers of yore,
whose efforts, unfortunately, were not followed up.
Vedanga Jyotisha
is the earliest available Indian text on astronomy. Based on the
astronomical observations in the text, the book has been dated to the 14th
century BC, or the last part of the Vedic Age. It is
written in a language that is comparable to Kalidasa, rather than the
Vedic Sanskrit.
After Vedanga Jyotisha, there
are no
complete texts on astronomy available up to the date of the Aryabhatiyam,
that is the 5th century AD, except the Siddhantas,
which, though compiled by Varahamihira as the Panchasiddhantika in
the 6th century AD, actually evolved in the beginning of the
Christian era and were originally 18 in number.
Aryabhatiyam
Aryabhatiyam has
121 sutras, which are very difficult to understand by themselves,
though they are very brief. Bhaskara's commentary explained these
aphorisms of
Aryabhatta I. In 1976, to
commemorate
the 1500th birth anniversary of Aryabhatta, INSA published
English and Hindi translations of Aryabhatiyam and Bhaskara's
commentary as well. But, you'd be lucky if you could find an Aryabhatiyam
now in any language - Sanskrit, English or Hindi!
As Aryabhatiyam is written in
the form
of shlokas, the author uses a standardised, innovative method
of substituting letters from the Sanskrit lexicon for representing
numbers, so that the chandas, or metrics, are maintained,
making the text easy to memorize. For example, the first line of
the stanza in which Aryabhatta gives the rule for the formation of the
sine table reads:
Makhi
bhakhi phakhi dhakhi Nakhi Gnakhi…..,
to
indicate that (the R sine differences in the minutes of an arc are)
225, 224,
222, 219, 215, 210……..
Some of
the important findings of Arybhatta, which had
application in Astronomy, are listed here:
¨ He gave the
value of P correct to
four decimal
places, but more importantly, mentioned that this value could only be 'asanna',
or approximate! It was only a 1000+ years after Aryabhatta that
the western world came to recognise this feature of P!
¨ In just one stanza
(the first line of which you would
have read in the previous para), he gives the rule for drawing up the
sine table for values of angles from 0 degrees to 90 degrees, at
intervals of 3º45'.
¨ Disagreeing with the
majority of his time, he stated that
the earth is circular in all directions - "Bugolah sarvato vruttah",
he said.
¨ He was the first
Indian astronomer to recognise that the
earth and other planets are not self-luminous: "Halves of the globes of
the earth and the planets are dark due to their own shadows; the other
halves facing the sun are bright," he said.
¨ He explicitly
mentions that the luminous heavenly bodies,
despite being stationary appear to move from east to west - "Achalani
bhani samapashchimagani", he said.
¨
He gave a remarkably
accurate measure of the period of
one rotation of the earth with reference to the fixed stars in the sky,
as 23hours, 56minutes, 4.1seconds. The corresponding modern value
is 23hours, 56minutes, 4.091seconds!
¨ He has computed the
number of revolutions likely to be
made by the planets in one
mahayuga, the traditional duration of which time period is
considered as being 43,20,000 years.
The scientific
temperament of ancient Indian astronomers
A serious
criticism against ancient Indian astronomers is
that they were not scientific observers but only mathematical
manipulators. However, a detailed study of the original texts of
the earliest works on astronomy and an appraisal of the observation
methodology and attitude of the astronomers reveals their strong
scientific basis.
¨ The
Yajurveda recognised that a year comprised 12 solar months and 6
seasons (rtus) (See box for Vedic nomenclature of seasons and
corresponding months)
|
Season
|
Description
|
vedic Solar Months
|
Julian calendar months(Approx.)
|
|
Vasanta
|
Spring
|
Madhu,
Madhava
|
February 19
- April
19
|
|
Grishma
|
Summer
|
Shukra, Suchi
|
April 20 -
June 20
|
|
Varsha
|
Rainy
|
Nabhas,
Nabhasya
|
June 21 -
August 22
|
|
Sharat
|
Autumn
|
Sahas,
Sahasya
|
August 23 -
October
23
|
|
Hemanta
|
Dewy/ Snowy
|
Isa, Urja
|
October 24 -
December 21
|
|
Sishira
|
Cold
|
Tapas,
Tapasya
|
December 22
-
February 18
|
¨
The Vedic astronomers
also noted that the shortest day
was at the winter solstice when the seasonal year, Sisira
began, with Uttarayana and rose to the maximum at the summer
solstice.
¨ The
Vedangajyotisa gives the duration of the longest and the shortest
days and a number of other astronomical computations such as the time
taken by the Sun and Moon to transit through a nakshatra, which
were required for practical application by the people of that age, in
their day to day lives.
¨ The Kerala
astronomer, Paramesvara (1360-1455), a
prolific writer, made astronomical observations for 55 long years and
recorded many of his findings in his works. Besides revising
existing parameters to be more exact, he also said that his
computations had to be periodically revised in keeping with the time
period.
¨ Aryabhatta boldly
differed from the puranic
theory of creation and destruction of the universe and maintained that
time is anadi, or continuous - without beginning or end.
¨ Bhaskara, speaking
against those who blindly believed in
tradition, asserted, "It will be impossible to believe in whatever is
said earlier unless every erroneous statement is criticised and
condemned."
¨ Ganesha Daivajna
(1507 AD) whose computations are used to
this day to draw up
panchangas in North India, and even north Karnataka, reasoned that
shastras, which are accurate in one era, become inaccurate over
time, and therefore need periodical correction.
The Hindu calendar (panchanga),
which
began as a simple compilation of celestial observations relevant to the
contemporary needs of the Vedic times is an abiding symbol of the
unbroken continuity of Indian astronomy. The knowledge of astronomy,
which was once common throughout India, was lost due to the vagaries of
history, though it was prevalent in Kerala till the 15th and
16th centuries. In fact, the astronomers of Kerala
made discoveries that were often corroborated by the discoveries of
western mathematicians and astronomers only in the 18th or 19th
centuries!
Dr S
Balachandra
Rao is the Director,
BHAVAN's Gandhi Centre of Science and Human Values, and the author of
several acclaimed books on Indian Mathematics and Astronomy. This
essay is based on a talk delivered by him at the invitation of Sri
Tirunarayana Trust, at the Indian Institute of World Culture, on August
29, 2004
TOP
|
