Transmission of Indian astronomy to China, Korea and Japan
Sky as a bridge:
Transmission of Indian astronomy
to China, Korea and Japan
President IAU Commission 41: History of Astronomy
Hon. Prof. Panjab University Mathematics Department Chandigarh
Indian Institute of Science Education and Research, Mohali, Punjab
ICOA-8 Hefei, China, 26-28 March 2014
Ancient cultural tradition of the Indian
subcontinent (India for short) is
characterized by a combination of three
important factors: (i) antiquity, (ii)
continuity, and (iii) interaction with the
There are two distinct phases in Indian
astronomy: (i) Vedic astronomy and (ii)
The oldest astronomical text in India is
Vedanga Jyotisha the earliest portions of
which could be as old as 1400 BCE. Indian
astronomy remained static for a very long
From 1st century BCE to 5th century CE new
Greco-Babylonian inputs were received from
the northwest. These included an accurate
luni-solar calendar (the Shaka (Saka) calendar
) and concepts of zodiac and week days.
The pioneering name in the modernization
of Indian mathematical (or Siddhantic)
astronomy is Aryabhata (b. 476 BCE) who
composed his concise but influential work
Aryabhatiyam [simply meaning
Aryabhata’s] in 499 CE.
Siddhantic astronomy focused on
calculating eclipses and planetary orbits.
In a tradition spanning more than 1000
years India produced a number of
eminent mathematician- astronomers
who set up and solved new equations,
and suitably adjusted the parameters so
that calculated planetary positions could
match the observed sky. /
India’s interaction with East Asia was on two
Interaction with China, and through it with
Korea, Japan and Vietnam, was driven by
Buddhism and characterized by translation of
Buddhist and other texts.
Interaction with Indonesia and Thailand ( not
being discussed here) was by sea from the
Indian east coast. There was no direct
contact with Japan, only though China and
Buddha personally was firmly against
astrology, but by the time Buddhism was
exported to East Asia, astronomy/ astrology
had become part of it. Unlike the traditional
Chinese focus on portents, Indian
mathematical astronomy could prepare
horoscopes for the benefit of individuals.
Transmission to China
Transmission of astronomy to China began
in the 1st century CE during the Later Han
period (25–220 CE) and continued into the
politically unstable Three Kingdom period
Indian inputs to China continued
intermittently even after that, with the most
detailed incorporation of Indian astronomy
coming during the Tang Dynasty (618-906
It needs to be appreciated that Indian
and Chinese histories of astronomy are
interlinked. An investigation of India-inspired
developments in Chinese
astronomy requires familiarity with the
state of astronomical knowledge in India
at that time.
At the same time China is important for
obtaining a better understanding of
developments within India.
This is so because India’s own
sources have inherent limitations.
Reference to Chinese sources may
help overcome them to an extent.
Nature and limitation of ancient Indian
India’s intellectual tradition has been
oral. Permanent writing material was not
used. And there was no system of
Astronomy texts were not designed as self-contained
self-study library books. Their
comprehension required familiarity with the
context and help of commentaries which in
many cases are no longer extant.
Astronomical results were recorded in terse
metrical poetry, in imitation of the sacred
Rigveda. However unlike the sacred texts
which were frozen in time, astronomy (and
healthcare) texts underwent constant
revision. A text not considered relevant at
any time would be forgotten for ever,>
except for excerpts incorporated in other
texts. Some time only the names of texts
or authors have been preserved without
any other information.
Chronology remains a severe handicap in case of
ancient Indian literature. Astronomy fares a little
better than other disciplines because time in
inbuilt into astronomical calculations. Still, there
are many texts and developments which cannot be
In other words, it is not possible to construct a
connected historical account of ancient astronomy
(or science in general) in India. Celebrated texts
record the end results but various stages of
development preceding them may not be known
at all or known only sketchily.
Buddhist intellectual tradition followed a different
route. Buddhists wrote down their texts and
preserved them. In many cases they can be
assigned reliable time bracket, by reference to
Thus East Asian records with firm dates can
help fix the chronology of Indian
developments which Indian sources
themselves may not be able to do.
Instructive illustration of this come from
The celebrated medical texts, Charaka.samhita and
Sushruta.samhita, are known to India only in their
final definitive un-dated form. We know about state
of Indian healthcare in India in 4th century CE from
the well-known Bower manuscript which came from
Kucha, now a county in the Aksu prefecture in mid-western
Also, an influential Indian healthcare text
Ashtanga.hrdya.samhita composed by
Vagabhata can be confidently dated 7th
century or a little earlier on the basis of
implicit reference to it in the work of the well-known
Chinese pilgrim I-tsing who was in
India from 672 CE till about 688 CE.
A valuable aid in the discussion of the
text’s contents is its Tibetan edition
prepared between 1013-1055 CE (Vogel
1965, pp. 8, 18). Vagbhata is the first
Indian physician to assign astronomical
causes to illnesses.
Vagbhata claimed that diseases which
originated during different stellar
(nakshatra) conjunctions followed
different courses. It would be interesting
to see how the Tibetan edition handles
Rahu and Ketu: Changing meaning
In ancient times, the planets with their
predictable orbits represented cosmic order
and were a source of comfort. On the other
hand, phenomena like comets and meteors
appeared without warning and thus
represented divine wrath.
Ancient Hindu and Buddhist sacred literature
treats eclipses as a calamity caused by a demon.
He is called Svarbhanu in the Rigveda, but later
texts use the name Rahu. The Pali Buddhist texts
tell us that the Moon and the Sun freed themselves
from the grasp of Rahu by invoking Buddha’s
name (Chandima Sutta, Samyutta-nikaya 2.9; Suriya Sutta,
Similarly the Buddhist Sanskrit text Shardula.
karana.vadana, a portion of which was translated
into Chinese in 265 CE, treats Rahu as a calamity.
For later reference we may note that the
term ketu was used as a common noun to
denote a number of phenomena involving
light and smoke. It could thus refer to
comets and meteors.
Mathematical theory of eclipses was propounded
in India in 499 CE by Aryabhata. According to
this theory, solar and lunar eclipses occur when
the Moon is at either of its orbital nodes. These
theoretical points move in a direction opposite to
that of the planets and complete an orbit in the
rather short period of 18.6 years.
One would have expected the astronomers to
declare that since the cause of eclipses was now
understood, there was no need for a demon.
However to maintain continuity with the sacred
tradition, the demon was not banished but made
mathematically amenable. It now did not appear
suddenly but came by appointment!
The mathematical theory of eclipses was
immediately taken note of in astrological
literature, by Varahamihira. The two nodes were
classified as planets, implying that they were now
amenable to mathematics. Since they were
hypothetical they were dubbed shadow planets.
They could have been given entirely new names.
But to maintain continuity with sacred
literature, old terms were given new
The name Rahu, already associated with the
eclipses, was given to the ascending node.
Another name was needed for the
The old common noun ketu was picked up for
the purpose ( why, we do not know).
The two nodes are 180 degrees apart so that
specifying one fixes the other. It would thus have
sufficed to include just one of them. Both were
listed as planets no doubt to bring the planetary
number up to nine which was considered sacred.
To sum up so far, 6th century CE onwards,
Rahu and Ketu represent shadow planets.
Ketu is in addition used to denote meteor/
comet. Before 6th century CE, ketu is only
comet/ meteor while Rahu is the eclipse-causing
Rahu as Luo-hou makes its first appearance in the
translated Matanga-sutra, that is Mo-deng-jie-jing,
which was rendered into Chinese by Zhu
Lu-yan and Ziu-Qian in 230 CE (sutra numbered
1300 of Taisho Tripataka).
According to Lee and Chen (2000), ‘In this
sutra, Luo-hou and “comet” are the two
hidden ones of Nine luminaries (jiu-yao)’.
I suspect this interpretation is anachronistic. The
term nine luminaries should not appear before 6th
A literal translation of the original Chinese
passage would be most welcome. It can then be
compared with the Sanskrit original
China’s systematic introduction to Indian
astronomy began in the early 8th century.
Remarkably, the Indian inputs did not reamin an
add-on, but were successfully assimilated. ( See
various papers by Michio Yano.)
An astronomer of Indian descent Qutan Xida
[Gautam Siddha] prepared an astronomical
treatise, Jiu-zhi-li in 718 CE. The elements
of this Treatise in turn were employed by
the well known Chinese astronomer Yi-
Xing (687-727 CE) in his famous calendar
Astrological treatise of the Kaiyuan Period is also
attributed to Qutan Xida. Consistent with the Indian
tradition Jiu-zhi-li designates Rahu as the ascending
node and Ketu the descending.
For some reason, Shen Kuo (1031-1095) in his
Meng-Xi Bi Tan interchanges the nomenclature of
ascending and descending nodes.
Far more significant was the contribution of
Indian Buddhist monk, Jin Ju Zha. His
work ‘Formulae forwarding of calamities
according to the Seven Luminaries’
contains detailed ephemerides of Rahu and
Ketu . These
were incorporated into the calendrical
calculations of the Tang dynasty Yuanhe
era, Year I ( 806 CE).
As already noted, naming the two nodes separately
is not necessary because they are 180 degrees
apart. Jin Ju Zha’s work recognizes this and
introduces a modification.
While employing Rahu to denote the ascending
node, he boldly decided to use Ketu to denote
lunar apogee (Niu 1995).
This is significant because in Indian
astronomical texts ( as distinct from the
astrological ones) the term ketu does not
appear. This is for good reason.
Once ascending note had been fixed there was no
need to discuss the descending node. Since
meteors/ comets were not predicable phenomena
ketu in the other sense would be irrelevant in a
The Chinese use of the term ketu in a
mathematical sense was thus an innovation.
An influential astrological text in China was
Hsiu-yao ching ( ‘the canon of mansions and
planets’) translated from an Indian work by
Amoghavajra in 759 CE. A more detailed account
was given in the 9th century treatise Ch’i-yao
jang-tsai-chuch (‘formulae for avoiding
calamities according to the seven luminaries’).
Taisho Tripitaka compiled by the Japanese during
1924-1934 CE is the most popular edition of the
Sanskrit sutras translated from Sanskrit into
Chinese from late 2nd till 11th century CE. Niu
Wei-Xing has published extensively on
astronomy in these sutras.
While interpreting Indian influences in Chinese
astronomy, scholars should not fall in the
anachronistic trap. First of all as literal a
translation as possible of the original Chinese text
should be provided. Next, the interpretation of
Chinese sources should be attempted in the
framework of knowledge prevalent in India at that
time and not later.
Let me say a few lines about Buddhist
cosmology which in fact needs a separate
Buddhist cosmology was inspired by India’s
geography. At the centre of the Earth stood
Mount Sumeru around which revolved the
geocentric planets and the cosmic sphere.
Sumeru was thus an abstraction of the
Himalayas and the Earth’s spin axis.
From the point of view of Indian
history scholars would be interested in
obtaining help from China on two
(1) What can we learn from Chinese
sources about Indian astronomy prior to
Aryabhata (499 CE). ( As I mentioned, very
little is known about transition from the
Vedic astronomy to the Siddhantic.)
(2) What gaps can be filled with help
from Chinese sources in the
development of post- 499 CE
Kochhar, Rajesh (2010) ‘Rahu and Ketu in mythological
and “astronomological” contexts.’ Indian Journal of
History of Science, Vol. 45, No. 2, pp. 287-297.
Lee, Eon- Hee and Chen, Kwan-Yu (2000) ‘A study of the
motions of Rahu and Ketu.’ Proc. 3rd Intl Conf on
Oriental Astronomy (ed: M. Hirai), pp. 93-96 ( Fukuoka:
Fukuoka University of Education Press).
Nakayama, Shigeru ( 1969) A History of Japanese
Astronomy: Chinese Background and Western Impact
(Cambridge: Harvard University Press).
Niu, Wei-Xing (1995) ‘An inquiry into the
astrological meaning of Rahu and Ketu.’ Chinese
Astronomy and Astrophysics, Vol. 19, No. 2, pp. 259-
Niu, Wei-Xing (1997/98) ‘Astronomy in the sutras
translated into Chinese.’ Studies in the History of
Medicine and Science, Vol. 15, No. 1-2, pp. 119- 129.
Vogel, Claus (1965) Vagabhata’s
Astangahrdyasamhita: The first five chapters of its
Tibetan Version ( Wiesbaden: Deutsche