ब्राह्मस्फुटसिद्धान्त (ब्रह्मगुप्त - शून्य, कुट्टक, बीजगणित एवं सम्पूर्ण २१ अध्याय सान्वय सटीक)

250 ARABIC AND INDIAN DIVISIONS OF THE ZODIAC tary on Ulugh Beg, and that the Kāmūs makes this term to be the name of eight stars in the form of a bow. 8. Puṣya, the eighth asterism, is described as an arrow, and consists of three stars, the chief of which being also the middle most, has no latitude, and is 12° to 13° distant from the seventh asterism, being placed by Hindu astronomers in 106° of longitude. This is evidently δ Cancri; and does not differ widely from the eighth lunar mansion Nethrah, which according to Ulugh Beg and others consists of two stars, including the nebula of Cancer. The Indian constellation comprises two other stars besides δ Cancri, which are perhaps γ and β of the same constellation. 9. Aśleṣā, the ninth asterism, contains five stars figured as a potter’s wheel, and of which the principal or eastern one is placed in 7°S, and according to different tables, 107°, 108° or 109° E. This appears to be intended for the bright star in the south- ern claw of Cancer (α Cancri), and cannot be reconciled with the lunar mansion Tarf or Tarfah, which comprises two stars near the lion’s (siṁha) eye, the northernmost being placed by Mohammad of Tīzīn in 24° of N. declination. 10. Maghā, the tenth asterism, contains like the last, five stars, but which are figured as a house. The principal of the Southern one has no latitude; and according to all authorities, has 129° longitude. This is evidently Regulus (α Leonis) : which is exactly 129½° distant from the last star in Revatī. The tenth lunar mansion of Arabians is Jebhah, which comprises three (some say, four) stars, nearly in the longitude of the lion’s heart. In this instance, therefore, the Indian and Arabian divisions of the zodiac coincide. This nakastra consists of α, γ, η and ν Leonis. 11. Pūrva-Phālgunī is the eleventh nakṣatra and is repre- sented by a couch or bedstead; it consists of two stars deter- mined by the place of the chief star (the northernmost, accord- ing to the Sūrya-Siddhānta) in 12°N and 144°E., or according to Brahmagupta, the Śiromaṇi and the Grahalāghava 147° or 148° E. They are probably δ and θ Leonis. The Arabian name for this lunar mansion is zubrah or Khertan.

ARABIC AND INDIAN DIVISIONS OF THE ZODIAC 281 It may be mentioned here that Brahmagupta and Bhāskara selected the southern for the principal star; while the Sūrya- Siddhānta took the northern. Hence the latitude stated by several Hindu authorities is the mean between both stars; and the difference of longitude, compared to the preceding and subse- quent asterisms, may be exactly reconciled upon this suppo- sition. 12. Uttara-Phalgunī, which is the twelfth nakṣatra, con- sists of two stars, and is figured as a bed or cot. These stars are ascertained by the place of one of them (the northernmost) 13°N. and 155° E. This indicates β Leonis; the same which singly constitutes the Arabian Lunar mansion Serfah, though Moham- mad of Tīzīn seems to hint that it consists of more than one star. 13. Hasta, the thirteenth nakṣatra, has the name and figure of a hand; and is suitably made to contain five stars. The principal one towards the west, next to the north-western star, is placed according to all authorities in 11° and 170° E. This can only belong to the constellation Corvus ; and accordingly five stars in that constellation (α, β, γ, δ and ε Corvi). The thirteenth lunar mansion of Arabs is Awwā, which is also described to contain five stars, situated under Virgo and so disposed as to resemble the letter Alif. They are placed by Ulugh Beg in the wing. Here obviously, there is nothing common between the Hindu and Arabian specification of the asterism. The agreement is only in the number of stars and in the longi- tude. 14. Citrā, the fourteenth nakṣatra, is figured as pearl. It is placed by the Sūrya-Siddhānta in 2° S and 180° E. and by Brahmagupta, the Śiromaṇi and Grahalāghava in 1¾ or 2°S and 183°E. This agrees with the Virgin's spike (α Virginis). The same star constitutes the fourteenth lunar mansion of the Arabs named from it Simāc ul aāzi. 15. Svāti, the fifteenth nakṣatra, is represented by a coral bead. The Sūrya-Siddhānta, Brahmagupta, the Śiromaṇi and Grahalāghava, all concur in placing it at 37°N. They differ one degree in longitude of its circle of declination, three of them

282 ARABIC AND INDIAN DIVISIONS OF THE ZODIAC making it 199° and the other 198°. The Indian asterism totally disagrees with the lunar mansion Ghafr which is the fifteenth Arabian mansion. and which consists of three stars in the Virgin's (Kanyā) foot, according to Ulugh Beg. but in or near the balance (Tulā), according to others. 16. Viśākhā, the sixteenth nakṣatra, consists of four stars described as a festoon. All the authorities place the principal and northernmost star in 1°, 1°20′ or 1°30′ S and in 212°, 212°5′ or 213° E. The latitude seems to indicate the bright star in the Soutehrn Scale (α Librae), though the longitude disagrees (suggest- ing possibly a remote star κ Librae). Colebrooke suggests the four stars to be α ν ι Librae and γ Scorpii. The sixteenth lunar mansion according to Arabs is Zubanah or Zubāniyah according to Mohammad of Tizin, the bright star in the northern scale (β Librae). 17. Anurādhā, the seventeenth nakṣatra, consists of four stars and is described as a row of oblations in a right line. Its chief or middlemost star is placed in 3°, or 2° or 1°45′ S and in 224° or 224°5′E, thus placing it near the head of the Scorpion (Vṛścika) (δ Scorpionis) and the asterism comprises β, δ, π, and ρ Scorpionis. The seventeenth lunar mansion of Arabs is called Iklīl or Iklīlu'l- jebhah, which is said to contain 4, 3, or 6 stars lying in a straight line. Those assigned by Ulugh Beg for this mansion are β, δ, ν and π Scorpionis. Thus here the Indian and Arabian astronomers both concur exactly. 18. Jyeṣṭha, the eighteenth nakṣatra, comprises three stars figured as a ring. The principal and middlemost star is placed in 4°·3½° or 3° S and in 229°, 229°5′ or 230°E; this position indicates Antares or the Scorpion's heart (α Scorpionis), which is also the eighteenth lunar mansion, named Kalb or Kalbul'akrab. The three stars of Indian asterism may be α, σ and τ Scorpionis. 19. Mūla, the nineteenth nakṣatra, is represented by a lion's tail, and it contains eleven stars, of which the charac- teristic one, the easternmost, is placed in 9°, 8½° or 8° S and in 241° or 242° E. This probably (not exactly) indicates ν Scor- pionis. This agrees with the eighteenth lunar mansion of Arabs known as Shaulah, consisting of two stars near the Scorpion's

sting. The Hindu asterism probably includes all the stars in the Scorpion’s tail (ε, μ, ζ, η, θ, ι, κ, λ, υ and ν Scorpionis). 20. Pūrva-Āṣāḍha, the twentieth nakṣatra, is figured as an elephant’s tooth or as a couch, and it consists of two stars, of which the most southern one is placed in 5½°, 5⅓° or 5° S and 254° or 255° E. This corresponds well with δ Sagittarii, and which also corresponds with the twentieth lunar mansion of Arabs called Nāaim. The Arabian mansion consists of four, or according to some eight, stars. The Indian nakṣatra corres- ponds to δ and ε Sagittarii. 21. Uttara-Āṣāḍha, the twenty-first nakṣatra, is represented by a couch or by an elephant’s tooth. The principal or the most northerly star is placed in 5° S and 260° or 261° E, agreeing with a star in the body of Sagittarius (τ Sagittarii), and the other star is perhaps the one marked ζ. The Arabian lunar mansion corresponding to it is Baldah, consisting of six stars, two, of which are placed by Mohammad of Tīzīn in declination 21° and 16°. One of these must be a star in the head of Sagit- tarius. Some authors, on the contrary, describe the lunar mansion as destitute of stars. Here the Arabs and Hindus do not show reconciliation. 22. Abhijit, the twenty-second asterism, consists of three stars figuring as a triangle or as a nut of floating Trapa (in modern Indian astronomy, it does not occupy an equal portion of the ecliptic with other nakṣatras). Its brightest star is very remote from the zodiac, being in 60° or 62° N. The longitude of its circle of declination is 265°, 266° 40′ or 268° according to different authorities. The corresponding lunar mansion of Arabs is Zābih, consisting of two stars (according to some, four) in the horns of Capricorn. This totally disagrees with Indian asterism. 23. Śravaṇa, the twenty-third nakṣatra, is represented by three footsteps, and contains three stars of which the middlemost is placed in 30° N (all authorities agree), and longitude 280° (Sūrya-Siddhānta) or 278° (Brahmagupta and Śiromaṇi), or 275° (Grahalāghava). The assigned latitude indicates the bright star in the Eagle, whence the three may be inferred to be α, β

284 ARABIC AND INDIAN DIVISIONS OF THE ZODIAC and γ Aquilae. According to Arabs, the twenty-third lunar mansion is Balā, which consists of two stars in the left hand of Aquarius. Here again Arabian and Hindu divisions are at variance. 24. Dhaniṣṭhā, the twenty-fourth nakṣatra, is represented by a drum or tabor. It comprises four stars, the westernmost of which is placed in 36° N and according to Brahmagupta, Śiromaṇi and the Sūrya-Siddhānta in 290° E (Grahalāghava gives 286°). This longitude of the circle of declination and the distance of the star on it from the ecliptic indicate the Dolphin : and the four stars are α, β, γ and δ Dolphini. The correspond- ing lunar mansion of Arabs is Sāud, which comprises two stars in Aquarius (β and ζ Aquarii). Here again the two divisions disagree completely. 24. Śatabhiṣak, the twenty fifth nakṣatra, is a cluster of 100 stars figured by a circle. The principal or the brightest has no latitude; or only a third, or at utmost half, a degree of south latitude; and longitude 320°. This best corresponds with λ Aquarii. According to Arabs, the twenty-fifth lunar mansion is known as Akhbiyah which consists of three stars only, placed in the wrist of the right hand of Aquarius. However, it appears from Ulugh Beg's tables, as well as from Mohammad of Tīzīn's, that four stars are assigned to this mansion. The Indian and Arabian systems of division differ considerably but less widely according to some. 26. Pūrva-Bhādrapada, the twenty-sixth nakṣatra, consists of two stars represented by a couch or bed, or else by a double headed figure, one of which is placed in 24° N and 325° or 326° E. The only conspicuous star nearly in that position is the bright star in Pegasus (α Pegasi) and the other may be the nearest considerable star in the same constellation (ζ Pegasi). The twenty-sixth Arabian lunar mansion is Mukaddim, consisting of two brightest stars in Pegasus (α and β). Here the Indian and Arabian divisions show concurrence. 27. Uttar-Bhādrapada, the twenty-seventh nakṣatra, consists of two stars, figured as a twin or a person with double face, or else as a couch. The position of the most northerly of the two

ARABIC AND INDIAN DIVISIONS OF THE ZODIAC 285 is in 26° or 27°N and 337° E. which probably indicates the bright star in the head of Andromeda, and the other star to be the one in the extremity of the wing of Pegasus (γ Pegasi). This exactly agrees with the twenty-seventh lunar mansion of Arabs named as Muakkher. Ulugh Beg assigns those stars to it. 28. Revatī, the twenty-eighth nakṣatra, comprises thirty- two stars figured as a tabor. The principal star is the southern- most one, it has no latitude, and two of them assert no longitude, but some make it ten minutes short of the origin of the ecliptic, viz. 359° 50'. This clearly marks the star on the ecliptic in the string of the Fishes (ζ Piscium). The ascertainment of this star is important in regard to the adjustment of the Hindu sphere. The Arabic name for this mansion is Risha, signifying a cord. But the constellation as described by Jauhari and cited by Golius, consists of a multitude of stars in the shape of a fish and termed Betnu'lhūt; in the navel of which is the lunar mansion. Moham- mad of Tīzīn alse makes this lunar mansion to be the same with Betnu'lhūt, which appears, however, to be the bright star in the girdle of Andromeda (β Andromedae) though others describe it as the northern fish, extending, however, to the horns of Ram. The lunar mansion and the Indian asterism, therefore, are not reconcileable in this last instance. I leave it to the readers to draw an inference as to the concurrence of the divisions of zodiac in Indian and Arabian systems. I would personally agree with Sir William Jones that the agreements are by chance. Arabs derived the idea of dividing zodiac in 27 or 28 mansions from Indians, or may have got it from Greeks, and then they proceeded in their own way for details. I do not agree with those scholars who sometimes state that the Hindus took the hint of dividing the ecliptic from Greeks. The Atharvaveda devotes a number of Suktas or hymns on Nakṣatras, and I have shown elsewhere that inspired by these hymns, Gārgya was the first Ṛṣi who detailed out the nakṣatras. This happened much before Greeks developed even their first notions of astronomy. While the concept of 27 nakṣatras is Vedic and most ancient and of purely Indian origin the concept of 12 Rāśis (signs) or twelve constellations is proba- bly inspired from Greeks. [The names Kanyā, (virgo), Tulā

286 ARABIC AND INDIAN DIVISIONS OF THE ZODIAC (Libra),Vṛścika (Scorpio), Dhanu, (Sagittarius), Makara, (Capri- corn), Kumbha (Aquarius), Mīna (pisces), Meṣa (Aries), Vṛṣa (Taurus), Mithuna (Gemini), Karka (Cancer), and Siṁha (Leo) were not used for Rāśis or signs in the Vedic times]. I shall con- clude this description with a passage from Colebrooke : The result of comparison shows, I hope satis- factorily, that the Indian asterisms, which mark the divisions of the ecliptic, generally consist of nearly the same stars, which constitute the lunar mansions of the Arabians : but in a few instances, they essentially differ. The Hindus have likewise adopted the divi- sion of the ecliptic and zodiac into twelve signs or constellations, agreeing in figure and designation with those of the Greeks; and differing merely in the place of the constellations, which are carried on the Indian sphere a few degrees further west than on the Grecian. That the Hindus took the hint of this mode of dividing the ecliptic from the Greeks, is not perha- ps altogether improbable; but if such be the origin of it they have not implicitly received the arrangement suggested to them, but have reconciled and adapted it to their own ancient distribution of the ecliptic into twenty-seven parts. In like manner, they may have either received or given the hint of an armillary sphere as an instrument for astronomical observation ; but certainly they have not copied the instrument which was described by Ptolemy, for the construction differs considerably. Names, Shapes, and Number of the Stars of the Nakṣatras The Muhūrta-cintāmaṇi provides a list of shapes associated to the nakṣatras (MuC. II. 59-60), In this list we are giving the number of stars as indicated by Varāhamihira, Brahmagupta and Lalla. The identification given here is as indicated by E. Burgess, in his Translation of the Sūrya-Siddhānta 1935, p. 378. (Calcutta). This table has been reproduced here from the Mahābhāskarīya of Bhāskara I, edited by K.S. Shukla.

NAMES, SHAPES AND NUMBER OF THE STARS 287

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CHAPTER XI Brahmagupta’s Astronomy : Its Highlights Beginning or Starting Point Very often in Indian astronomy, we come across a term ahargaṇa (literally meaning collection of days), which means the number of mean civil days elapsed at mean Sunrise at Laṅkā on a given lunar day (tithi), since the beginning of Kaliyuga. It is the beginning of Kaliyuga, which is taken as the starting point for the reckoning of ahargaṇa. This happened on Friday, Febru- ary 18, B.C. 3102, at mean sunrise at Laṅkā, when the Sun, Moon, and the planets are supposed to have been in conjunction at the first point of the nakṣatra Aśvinī (which is a fixed point situated near the star ζ-Piscium). According to Āryabhaṭa and Bhāskara I, the duration of Kaliyuga is 1,080,000 solar years. Four times this (4,320,000) is the duration in solar years of a bigger unit called Mahāyuga or even yuga. Laṅkā in Indian astronomy is a hypothetical place where the meridian of Ujjain (latitude 23° 11′ N, longitude 75° 52′ E from Greenwich) intersects the equator. It is one of the four hypothetical cities on the equator called Laṅkā, Romaka, Siddhapur and Yamakoṭi (or Yavakoṭi). The Sūrya-siddhānta describes Laṅkā as a great city (mahāpurī) situated on an island to the south of Bhāratavarṣa.¹ The present Ceylon is not the

1. समन्तान्मेरुमध्यात्तु तुल्यभागेषु तोयधेः । द्वीपेषु दिक्षु पूर्वादिन्नगर्यो देवनिर्मिताः ।। भूवृत्त पादे पूर्वस्यां यवकोटीति विश्रु ता । भद्राश्व वर्षे नगरी स्वर्णप्राकारतोरणा । याम्यायां भारतेवर्षे लङ्का तद्वन्महापुरी ।। (Cont. on page 290)

290 BRAHMAGUPTA'S ASTRONOMY ITS HIGHLIGHT astronomical Laṅkā, as it is about six degrees to the north of equator. The astronomical Laṅkā is mentioned by Brahmagupta in the beginning of his very first Chapter¹. According to Brahmagupta all the four yugas of a Catur- yuga or mahāyuga are not of the equal duration : Kaliyuga is of 432,000 years. Dvāpara of 864,000 years, Tretā of 1,296,000 years and Kṛtayuga of 1,728,000 years; total of the four is 4,320,000 years. Āryabhaṭa regards all yugas of equal duration, 1,080,000 years². The Saka era, which is usually used in Indian astronomy for the reckoning of years commenced 3179 years after the beginning of Kaliyuga. The number of lunar months in a yuga does not coincide with the number of solar months. Thus we have the conception of the Intercalary months : the number of intercalary months in a yuga denotes the excess of the number of lunar months in a yuga over the number of solar months in a yuga. Thus in a yuga we have Lunar months 53,433,336 Solar months 51,840,000 Intercalary months 1,593,336 Lunar days 1,603,000,080 Civil days 1,577,917,500 Omitted lunar days 25,082,580 The number of omitted lunar days in a yuga is equal to the number of lunar days in a yuga minus the number of civil days in a yuga. (Cont. from page 289) पश्चिमेकेतुमालाख्ये रोमकाख्या प्रकीर्तिता । उदक्सिद्धपुरी नाम कुरुवर्षे प्रतिष्ठिता ॥ --Sūrya. XII. 36-39

1. चैत्रसितादेरुदयाद्भानोर्दिनमासवर्षयुगकल्पाः । सृष्ट्यादौ लंकायां समं प्रवृत्ता दिनेऽर्कस्य ॥ —BrSpSi. I. 4
2. युगदशभागो गुणितः कृतं चतुर्भिस्त्रिभिर्गुणस्त्रेता । द्विगुणो द्वापरमेकेन संगुणः कलियुगं भवति ॥ युगपादानायैभटश्चत्वारि समानि कृतयुगादीनि । यदभिहितवान् न तेषां स्मृत्युक्तसमानमेकमपि ॥ —BrSpSi. I. 8-9

UNITS OF TIME 291 Units of time For the measurements of durations, it is necessary to have units of time. Brahmagupta gives the following units :¹ 6 prāṇas or Asus=1 Ṛkṣa-vināḍikā or nakṣatra-vighaṭikā or one pala (24 seconds) 60 palas =1 ghaṭikā (24 minutes) 60 ghaṭikās =1 divasa or dina (day) (24 hours) 30 dinas =1 māsa (month) 12 māsas =1 varṣa or year Similar to the divisions of time, we have the divisions of an arc :² Vikalā (or viliptā or viliptikā) =second of arc. 60 vikalās =1 kalā (minute of arc) 60 kalās =1 aṁśa (degree of arc) 30 aṁśas =1 rāśi 12 rāśis =1 bhagaṇa (complete circle, 360°) Unlike Āryabhaṭa and others, who take kali, dvāpara, tretā, and kṛta of equal number of years, Brahmagupta regards kali consisting of 432,000 years, dvāpara twice of it, consisting of 864,000 years, tretā thrice of Kali consisting of 1,296,000 years and kṛta four times of kali conisting of thus 1,728,000 years, all the four to be making a yuga of 4,320,000 years.³ Further in the beginning of kṛta there is a sandhyā of 1728000/12 years (=144,000 years), and at the end of Kṛta, there is a sandhyāṁśa of 144,000 years; similarly in the beginning of tretā, we have a

1. प्राणैर्विनाडिकाऽर्क्षी षड्भिर्घटिका षष्ट्या । घटिका षष्ट्या दिवसो दिवसानां त्रिंशता मासः ॥ —BrSpSi. I. 6
2. मासा द्वादशवर्षं विकलालिप्तांशराशिभगणांतः । क्षेत्र विभागस्तुल्यः कालेन विनाडिकाद्ये न ॥ —BrSpSi. I. 6 वर्षं द्वादश मासास्त्रिंशद्दिवसो भवेत्स मासस्तु । षष्टि र्नाड्यो दिवसष्षष्टिश्च विनाडिका नाडी ॥ —Ārya. III. 1 गुर्वक्षराणि षष्टिर्विनाडिकार्क्षी षडेव वा प्राणाः । एवं काल विभागः क्षेत्र विभागस्तथा भगणात् ॥ —Ārya, III. 2
3. खचतुष्टयरदवेदा रवि वर्षाणां चतुर्यु गं भवति । सन्ध्या सन्ध्यांशैः सह चत्वारि पृथक् कृतादीनि ॥ युगदशभागो गुणितः कृतं चतुर्भिस्रिभिर्गुणस्त्रे ता । द्विगुणो द्वापरमेकेन संगुणः कलियुगं भवति ॥ —BrSpSi. I. 7. 8

292 BRAHMAGUPTA'S ASTRONOMY ITS HIGHLIGHT sandhyā of 1.296.000/12; i. e. 108.000 years and at the close of tretā a sandhyāṁśa of 108,000 years. Again, in the beginning of dvāpara we have a sandhyā of 864.000/12, i. e. 72.000 years and at the close of dvāpara a sandhyāṁśa of 72000 years; and similarly at the beginning a sandhyā and at the close a sandhyāṁśa of 432.000/ 1, i. e. of 36,000 years in the case of kali. In this respect Brahmagupta appears to follow Manu. the first author or giver of law. He regards further the following divisions of time :¹ 71 yugas =1 manu 14 manus =1 kalpa Again, in the beginning, at the middle and at the close of each manu, there are sandhis, each equal to the measure of kṛta. Thus, taken as a whole 1 kalpa=71×14 yugas+15 sandhyā-sandhyāṁśa =994 yugas+15×duration of kṛta =994 yugas+15×(4×432,000) years =994 yugas + 6 yugas =1000 yugas = 1 Brahma-dina (Brahmā's day) Thus Brahmā's day is regarded as 1 kalpa or one thousand caturyugis or 1000 yugas or the same as 1000 mahāyugas). Āryabhaṭa regards a manu to consist of 72 yugas and therefore a kalpa according to him would be of 14×72 yugas, or 1008 yugas.² Since in the foreign Siddhāntas like Romaka, there is no reference to yuga, manu and kalpa. Brahmagupta regards these systems to be unauthoritative.³ We have said that our starting point was the beginning of Kaliyuga, Friday February 18, B.C. 3102, at mean rise at Laṅkā, when the Sun, Moon and the planets are supposed to have been in conjunction at the first point of the Nakṣatra Aśviṇī. This type of conjunction would again happen after a period of kalpa.

1. मनुरेकसप्ततियुगः कल्पो मनवश्चतुर्दश मनूनाम् । आद्यन्तरान्त सन्धिषु कृतकालोऽस्माद्युग सहस्रम् ॥ —BrSpSi. I. 10
2. दिव्यं वर्ष सहस्रम् ग्रहसामान्यं युगं द्विषट्क गुणम् । अष्टोत्तरसहस्रं ब्राह्मो दिवसो ग्रहयुगानाम् ॥ —Ārya. III. 8
3. युगमन्वन्तरकल्पाः कालपरिच्छेदकाः स्मृतावुक्ताः । यस्मान्नरोमके ते स्मृतिबाह्यो रोमकस्तस्मात् ॥ —BrSpSi. I- 13

UNITS OF TIME 293 We shall have the same type of conjunction of grahocca, mandocca śīghrocca and pāta after a complete cycle of kalpa as we had in the beginning of creation. This is a natural observable cycle which is recognised in Indian astronomy and in no other foreign system; and hence only the Indian system recognises the time measure of kalpa. Ucca or apex is of two kinds : mandocca (apex of the slowest motion) and śīghrocca (apex of the fastest motion). The mandocca is that point of a planet's orbit which is at the remotest distance and where the motion of the planet is slowest. In the case of the Sun and the Moon, it is the apogee; and in the case of other planets, it is the apogee or aphelion, the geocentric longi- tude of the apogee being equal to the helio-centric longitude of the aphelion. The śīghrocca of a superior planet (Mars, Jupiter and Saturn) is defined as the mean Sun; that of an inferior planet Mercury or Venus) śīghrocca is an imaginary body which is supposed to move in such a way that its direction from the earth is always approximately the same as that of the actual planet from the Sun. The bhagaṇas or the revolution numbers of a planet have been given by Āryabhaṭa and Brahmagupta¹ both; they mean the number of revolutions that a planet performs in a certain period, say a kalpa of 4,320,000,000 years. The bhagaṇas of planets are given as follows :

1. कल्पेऽर्कबुधसितानां भगणाः शून्यानि सप्त रदवेदाः । प्राग्ब्रजता कुजगुरुशनि शीघ्रोच्चानां स्वकक्षासु ॥ पञ्चाम्बराणि गुण-गुण पञ्चमुनि स्वरैर्मिताः शशिनः । भौमस्य द्वियमशराष्टपञ्चवसूरसनवद्वियमाः ॥ कृतवसुखवाष्टनन्द-नवषट्‌त्रि नवागेन्द्वो ज्ञशीघ्रस्य । जीवस्य शरेष्वद्रि षट्पञ्चद्वि कृतरसरामाः ॥ सितशीघ्रस्य यमलगोवेदनवाष्टाग्निपञ्चयमखनगाः । अष्टनवपञ्च मुनि रसशररस मनवोऽर्कपुत्रस्य ॥ खाष्टाब्धयो वसुशरवसुपञ्चखचन्द्रक्सुवसुसमुद्राः । द्विनवयमा द्वित्रिगुणाः शरेषु वसवस्त्रि पञ्चरसाः ॥ शशिवेदा मन्दानामर्कादीनां विलोमपातानाम् । वसूरसरुद्रेन्दुगुणा द्वित्रियमाः सप्तरसपञ्चाः ॥ शशियमाशरा गुणरसास्त्रिनन्दवसवः समुद्रवसु विषयाः । चन्द्रादीनां पश्चात् व्रजतोऽश्विन्यादि भगणस्य ॥ BrSpSi. I. 15-21

294 BRAHMAGUPTA'S ASTRONOMY ITS : HIGHLIGHTS | Planet or a body | Bhagaṇas | | Ravi or Sun | 4,320,000,000 | | Budha or Mercury | 4,320,000,000 | | Śukra or Venus | 4,320,000,000 | | Candra or Moon | 57,753,300,000 | | Kuja or Bhauma or Mars | 2,296,828,522 | | Budha-śīghrocca | 17,936,998,984 | | Bṛhaspati or Jupiter | 364,226,455 | | Śukra-śīghrocca | 7,022,389,492 | | Śani or Saturn | 146,567,298 | | Arka or Ravi-mandocca | 480 | | Candra mandocca | 488,105,858 | | Kuja or Bhauma mandocca | 292 | | Budha-mandocca | 332 | | Bṛhaspati or Jīva-mandocca | 855 | | Śukra-mandocca | 653 | | Śani-mandocca | 41 | | Candra-pāta | 232,311,168 | | Kuja or Bhauma-pāta | 267 | | Budha-pāta | 521 | | Bṛhaspati or Guru-pāta | 63 | | Śukra-pāta | 893 | | Śani-pāta | 584 | By pāta is meant the ascending node of a planet's orbit (on the ecliptic). In a kalpa, the number of bha-bhramas (sidereal days) or also known as bha-parivartas is 51,040,000,000. If we subtract out from this number the bhagaṇa of the Sun, we get what is known as ku-dinas or Savana days or the solar or sacrificial days. (51,040,000,000—4,320,000,000=46,720,000,000 Sāvana days or kudinas). In a kalpa, the number of Ravi-bhagaṇas also correspond to the number of solar years (Saura-varṣas), i.e., 4,320,000,000; this number multiplied by 12 gives the number (i.e. 51,840,000,000) of solar months. The difference between the candra-bhagaṇas and the Ravi- bhagaṇas in a kalpa gives the number of lunar months (Cāndra-

UNITS OF TIME 295 māsa) in a kalpa (57,753,300,000-4,320,000,000=53,433,300,000 lunar months). By subtracting the number of solar months from the number of lunar months in a kalpa, one gets the number of adhi-māsas (additional-months) : 53,433,300,000-51,840,000,000= 1,593,300,000 adhimāsas. This multiplied by 30 gives the number of lunar days (śaśi-divasa) in a kalpa ; 53,433,300,000×30= 1,602,999,000,000 lunar days. The difference between the lunar days and kudinas in a kalpa gives the number of avama-dinas in a kalpa : 1,602,999,000,000-45,720,000,000=1,556,279,000,000.¹ Brahmagupta calculates out the sṛṣṭi-saṁvatsara or the Creation Era during his year of composition of the Treatise. He says : Six manus have gone in the kalpa ; the seventh manu is now running of which have lapsed 27 caturyugis ; of the twenty eighth caturyugī, the three yugas, kṛta, dvāpara and tretā have gone by and also of the present kaliyuga 3179 years have lapsed. The total period thus lapsed on calculation comes to be 1,972,947,179 years :² Total Period=6 manus+7 manu-sandhis+27 yugas +kṛta+dvāpara+tretā+3179 years of kali. =(6×71×4,320,000 years) +(7×4×432,000 years)+ (27×4,320,000 years)+(1,728,000+1,296,000+864,000)+ 3,179=1,972,947,179 years. =1,840,320,000+12,096,000+116,640,000+3,888,000+ 3,179=1,972,947,179 years. Calculation of Ahargaṇa : The method of calculating ahar- gaṇa (number of days elapsed since the beginning of kaliyuga)

1. परिवर्त्ताः स्वचतुष्टयशराश्वि रसगुणयमद्विवसुतिथयः । रवि भगणोना भानोः सावनदिवसाः कुदिवसास्ते ॥ रवि भगणाख्यब्दा द्वादशगुणिता भवन्ति रविमासाः । भगणान्तरं रवीन्द्वोः शशिमासाः सूर्यमासोनाः ॥ अधिमासाः शशिमासास्त्रिंशद्गुणिता भवन्ति शशिदिवसाः । शशिसावनदिवसान्तरमवमानि तिथिः शशांकदिनम् ॥ —BrSpSi. I. 22-24
2. कल्पपरार्द्धं मनवः षट् कस्य गताश्चतुर्युगत्रिघनाः । त्रीणिकृतादीनिकलेर्गोऽङ्गैक गुणाः शकान्तेऽब्दाः ॥ नवनगशशि मुनिकृत नव यमनगनन्देन्दवः शकनृपान्ते । सार्धमतीतमनूनां सन्धिभिराद्यन्तरान्तर्गैः ॥ BrSpSi. I. 26-27

: is it a footnote mark, or is the print literally: - खराऽष्टेषु? Wait, look at line 39: -खराऽष्टेषुद्वयष्टशून्यशरारिभिः । Wait, look at the first character: संगुण्याख्या? No, look at line 39 again very carefully: First word: संगुण्याख्या? Wait! Could it be: संगुण्याख्या- No, look at the image: संगुण्याख्या-बराऽष्टेषुद्वयष्टशून्यशरारिभिः । Wait, why बरा? Could it be ऽबरा? Wait, look at the English text above: "25,082,580" Why would the Sanskrit have those characters? Wait, this is an Indian printed book from around 1970-1980 (looks like Indian National Science Academy, INSA, "BRAHMAGUPTA'S ASTRONOMY ITS : HIGHLIGHTS", page 296). In these INSA publications (often edited by K. S. Shukla or similar scholars), let's look at how the typesetters set Sanskrit text. Often the typesetter made typos, or used specific ligatures! Let's transcribe what is VISUALLY PRINTED on the page, because the user wants: "Transcribe all text on the ancient Indian

UNITS OF TIME 297 Addendum : The mean lunar day (madhyama tithi) may, however, differ from a true lunar day (spaṣṭa tithi) by one, so that the ahargaṇa obtained by the above process may sometimes be in excess or defect by one. To test whether the ahargaṇa (obtained by the above process) is correct, it is divided by seven and the remainder counted with Friday. If this leads to the day of calculation, the ahargaṇa is correct; if it leads to the preceding day, the ahargaṇa is in defect; and if that leads to the succeeding day, the ahargaṇa is in excess. When the ahargaṇa is found to be in defect, it is increased by one; when it is found to be in excess, it is diminished by one. (K.S. Shukla : MBh. p. 4-5) Example—Calculate the ahargaṇa on October 1,1965. From Indian Calendar we find that October 1,1965 falls on Friday. 7th lunar day (tithi) in the light half of the 7th month Āśvina in the Saka year 1887 (elapsed). Let us proceed as follows : Adding 3,179 to 1,887. we get 5,066. (1) Multiplying this by 12 and adding 6 (i. e. the number of lunar months elapsed since the beginning of Caitra) we get 60,798. ... ... (2). Multiplying this by 1,593,336 and dividing the product by 51,840,000, we get 1,868 as quotient. (The remainder is discarded as unnecessary) (3) Adding this number (i.e. 1,868) to the previous one (i.e.) 60,798) we get 62,666. (4) Multiplying this by 30 and adding 6 (i.e. the number of lunar days elapsed since the beginning of the current month) to the product, we get 1,879,986. (5) Multiplying this by 25,082,580 and dividing the product by 1,603,000,080, we get 29,416 as the quotient. (The remainder is discarded as not necessary). (6) Subtracting this number (i.e. 29,416) from the previous one (i.e. 1,879,986) we get 1,850,570. (7) This is the required ahargaṇa. Since division by 7 leaves

298 BRAHMAGUPTA'S ASTRONOMY: ITS HIGHLIGHTS 1 as the remainder. we subtract one from it, and get 1,850,569 as the correct ahargaṇa for the day. An Alternative Rule for Ahargaṇa Both Bhāskara I and Brahmagupta give an alternative rule for calculating out ahargaṇa¹ : Multiply the number of (solar months) elapsed since the beginning of kaliyuga by the number of lunar months (in a yuga) and divide by the number of solar months (in a yuga). Reduce the quotient to days (and add the number of lunar days elapsed since the begin- ning of the current lunar month); then multiply by the number of civil days (in a yuga) and divide by the number of lunar days (in a yuga); the quotient denotes the ahargaṇa. Mean Longitude of a Planet (i) The mean longitude of a planet in revolutions is given by the expression : (Brahmagupta² and also Bhāskara³).

1. शशांकमासैरभिताडितान् हरेदतीतमासानथ वार्कसम्भवैः । दिनीकृतान् भूमिदिनैर्हतान् दिनैर्विभज्य लब्धश्शशिजैर्हरर्गणः ॥ MBh. I. 7 युगगतशशिमासवधाद्रविमासाप्तं दिनीकृतं सदिनम् । भूदिनगुणितं शशिदिनहृतमाप्तमहर्गणः सैकः ॥ —BrSpSi. XIII. 18
2. इष्टग्रह भगण गुणादहर्गणात् कल्पसावन द्यु हृतात् । भगणादि फलं मध्यो लंकायां भास्करौदयिकः ॥ BrSpSi. I. 31
3. उद्दारितान् यान् भगणान् क्षमादिनैर्लभामहे कान् कलियातवासरैः । इति प्रलब्धा भगणास्ततः क्रमाद् गृहाशलिप्ता विकलाः सतत्पराः । —MBh. I. 8 पर्यायाहर्गणाभ्यासो ह्रियते भूदिनैस्ततः । लभ्यन्ते पर्यायाः शेषाद्राशि भागकलादयः ॥ भास्करै स्त्रिंशता षष्ट्या सङ् गुणय्य पृथक् पृथक् । तेनैव भागहारेण लभ्यन्तेऽर्कोदयावधेः ॥ —LBh. I. 15-17 (Divide the product of the revolution-number of a planet and the ahargaṇa by the (number of) civil days (in a yuga); thus are obtained the (number of) revolutions (performed by that planet). From the (successive remainders multiplied respectively by 12,30 and 60 and divided by the same divisor (i.e. the number of civil days in yuga) are obtained the signs, degrees and minutes etc. (of the mean longitude of that planet) for (mean) sunrise (at Laṅkā).

MEAN LONGITUDE OF PLANET 299 revolution number of planet × ahargaṇa Mean longitude = —————————————————————————————————————— civil days in a yuga Similar expression is given by more recent Indian astro- nomers also. (ii) Mean longitude of desired planets in minutes (mean longitude of the known planet in revolu- tions etc. reduced to minutes) × (revolution number of the desired planet) = ———————————————————————————————————————————————— revolution number of the known planet. This rule is common to Brahmagupta¹ and Bhāskara I². (iii) An alternative rule for deriving the mean longitude of the Moon from that of the Sun and vice versa has been given by Bhāsakara I and Brahmagupta both. Multiply the ahargaṇa by the number of intercalary months in a yuga and divide (the product) by the number of civil days (in a yuga) : the result is in the terms of revolutions etc. Add that to thirteen times the mean longitude of the Sun. (This is the process) to obtain the mean longitude of the Moon³. Mean longitude of the Moon (intercalary months in a yuga) × ahargaṇa = ————————————————————————————————————————— revolutions civil days in a yuga

1. ज्ञातभगणादिभुक्तं सविकलमिष्टयुग भगणसंगुणितम् । ज्ञात युगभगणभक्तं मध्यो भगणादि फलमिष्टः ॥ — BrSpSi. XIII. 27
2. निशाकरं वाग्रहमुच्चमेव वा कलीकृतं तत्सहयातमण्डलैः । यथेष्ट नक्षत्रगणैर्हतं हरेत् तदीयनक्षत्र गणैस्ततः कला ॥ MBh. I. 10 The (mean) longitude of the Moon, the planet, or the Ucca (whichever is known) together with the revolutions performed should be reduced to minutes. The resulting minutes should then be multiplied by the revolution-number of the desired planet and (the product obtained should be) divided by the revolution-number of that (known) planet. The result is (the mean longitude of the desired planet) in minutes.
3. द्युगणं युगाधिमासैर्गुणितं युग भूदिनैर्हृतेऽलब्धम् । भगणादि मध्यमार्के त्रयोदश गुणार्धिकं चन्द्रः ॥ —BrSpSi. XIII. 33 युगाधिमासैर्धुगणं हतं हरेत् क्ष्मादिनैर्वां भगणादि लभ्यते । त्रयोदशघ्ने सवितर्यथा क्षिपेन्निशीथिनीनां पतिचारसिद्धये ॥ —MBh. I. 11