Origins of Astronomy - Tata Institute of Fundamental Research
Origins of Astronomy - Tata Institute of Fundamental Research
Origins of Astronomy - Tata Institute of Fundamental Research
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year2002200320042005200620072008200920102011201220132014Date and Time <strong>of</strong> Solstice and Equinoxday20212020202120202020202020EquinoxMartime19:1601:0006:4912:3318:2600:0705:4811:4417:3223:2105:1411:0216:57day21212121212120212121202121SolsticeJunetime13:2419:1000:5706:4612:2618:0623:5905:4511:2817:1623:0905:0410:51day23232222232322222323222223EquinoxSepttime04:5510:4716:3022:2304:0309:5115:4421:1803:0909:0414:4920:4402:29day22222121222221212122212121SolsticeDectime01:1407:0412:4218:3500:2206:0812:0417:4723:3805:3011:1117:1123:03Sun and seasons• Any observer will notice this drift <strong>of</strong> the Sunrise point(against the background geography) and its relation toseasons.• If you reside in cold regions outside the tropics, Sun,and its location become more important than theMoon.• These cultures therefore become Sun worshipers.<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 29<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 30Winters and Summers• For Northern Hemisphere, winter is the time theSun spends south <strong>of</strong> equinox.• By this count, there are 187 days for summerand 178.4 for winter. The winters are shorterand colder in the northern hemisphere.Sun and Rashis• The constellations at Sunrise change with time.• The constellations on the Sun’s path (Rashis) are sodesigned that in 1 lunar Synodic month (30 days) theSun moves 1 Rashi. There are 12 Rashi.• Since 360 < 365, seasons begin to drift 6 to 7days/year and in 5 years, addition <strong>of</strong> a month isrequired to synchronise the calendar with the seasons.• This is called the intercalary month.<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 31<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 328
Sun and Moon together• When the Moon returns to a Nakshatra it doesn’t have the same phase• Phase <strong>of</strong> the Moon is decided by its distance from the Sun• At each <strong>of</strong> Full Moon, the Moon is 2.25 Nakshatras away from the previousFull Moon, and the Sun is 1 Rashi ahead (Rashis are defined that way)• Sun and Moon move in the same direction suggests that the Earth isspinning in the same direction as it is rotating.• The Sun’s plane (Orbital plane <strong>of</strong> the Earth around the Sun or the Ecliptic) isinclined to the Moon’s path by 5 o.• Point <strong>of</strong> intersection <strong>of</strong> the two planes are called the nodes. These nodes arecalled Rahu and Ketu. These nodes rotate with a period <strong>of</strong> 18.6 years.<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 33 <strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 34Celestial Equator and EclipticEcliptic and Orbit <strong>of</strong> MoonNCPEclipticKetu (Descending Node) at VENCPLunar OrbitEclipticSSAECelestial EquatorCelestial EquatorWSVEAnglebetween thetwo is 23.5 oMotion <strong>of</strong> Sunand MoonVE = Vernal EquinoxSS = Summer SolsticeAE = Autumnal EquinoxWS = Winter Solstice<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 35Rahu (Ascending Node) at VEHrishikesh Joglekar <strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 369
Ecliptic and Orbit <strong>of</strong> MoonEcliptic and Orbit <strong>of</strong> MoonNCPNCP<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 37<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 38Ecliptic and Orbit <strong>of</strong> MoonEcliptic and Orbit <strong>of</strong> MoonNCPNCPRahu (Ascending Node) at WS<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 39<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 4010
Planets• Of the ~ 6,000 stars visible at night (from ~ 10 22 stars),there are 5 objects apart from Sun and Moon which are notstationary. They are called Planets.• These are Mercury, Venus, Mars, Jupiter and Saturn.• Their path is not random. They move more or less onthe same path as the Sun and the Moon.• Mercury moves the fastest and Saturn the slowest.Planet periods• Mercury goes around the Sun 88 (earth) in days.• Venus takes 0.61 (earth) years• Mars takes 1.88 (earth) years• Jupiter takes 11.9 (earth) years• Saturn takes 29.4 (earth) years• Mercury goes 30 o from the Sun• Venus goes 60 o from the Sun<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 49<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 50Making calendars• In order to keep track <strong>of</strong> time over long periods<strong>of</strong> years, a method <strong>of</strong> counting has to bedevised. This is called a calendar.• Apart from counting, special markers areintroduced to ensure that the counting iscorrect.• It also encourages study <strong>of</strong> rare events bypointing out their rarity.<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 51Ancient Calendars• Vedanga Jyotish (1200 BC) This is the oldest Lunar calendar. Itcontains a 5-year Yuga <strong>of</strong> 62 synodic lunar months.• Brihaspati samvatsar (year) chakra: 60 year cycle <strong>of</strong> Jupiter. The yearshave names like ‘Prabhav’, ‘Vibhav’ etc.• The Griha-parivritti cycle: It consist <strong>of</strong> 90 solar years. The length <strong>of</strong> 1year being 365.2586 days. The year commences with sun enteringMesha (Aries sign). This type <strong>of</strong> calendar is used in southern peninsula<strong>of</strong> India especially in Tamilnadu.• Saptarshi era: consists <strong>of</strong> cycles <strong>of</strong> 2700 years. It originated with thesupposition that seven Rishis stay in each Nakshatra for 100 years.This era was in use in Kashmir.• The currently used calendar is Luni-solar calendar in which eachmonth is synodic lunar month <strong>of</strong> 29.5 days. One year consists <strong>of</strong> 12such months = 254 days. The remaining 11 days <strong>of</strong> the year areadjusted in Adhik maas (intercalation month) that occur generally in<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 52the 3rd, 5th, 8th,11th,14th,16th and 19 year cycle <strong>of</strong> years.13
The Saptarshi EraSaptarshi Era• An interesting time line in the Vedic literature isthe Saptarshi Era.• It states that the Saptarshi constellation movesinto different Nakshatras giving different eras. Itis generally assumed to be wrong.• However, the exact manner <strong>of</strong> the definitionclearly shows that the starting date <strong>of</strong> the Era is2300 BC and originates in southern Gujarat.(Sule, Vahia, Bhujle, 2005)2100 BC 2000 AD<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 53<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 54Yuga in Vedic Literature• Yuga concept is introduced in Vedic astronomyto synchronise solar and lunar calendars.• The yuga period <strong>of</strong> five years, whoseconstituent years are called samvatsara,parivatsara, idavatsara, anuvatsara, andidvatsara, has been in use since Vedic times.• However, there are actually 1826.2819 days ina yuga <strong>of</strong> five solar (sidereal) years.Furthermore, there are 1830.8961 days in aperiod <strong>of</strong> 62 lunar months. It is suggested that~4.5 days were dropped as ‘reset error’.<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 55Yuga: Recent interpretation• There are 4 Yugas the duration scale <strong>of</strong> 4:3:2:1• Satya Yuga or Krita Yuga (1,728,000 years),• Treta Yuga (1,296,000 years) ,• Dvapara Yuga (864,000 years)• Kali Yuga (432,000 years)• Satya Yuga or Krita Yuga - dhyana (meditation)• Treta Yuga - yajna (sacrifice)• Dvapara Yuga - archana (worship)• Kali Yuga - daana (alms)• More acceptable interpretation is that they are Daivik years or days. Thisgives Yugas to be 1200: 2400: 3600: 4800 years (total 12,000 years).• It is believed to have begun with the death <strong>of</strong> Krishna in 3102 BC?????.• This reference <strong>of</strong> time is still used in religion and literature.<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 5614
Calendars in use• The Vikram era:– Begins with the coronation <strong>of</strong> King Vikramaditya.– The year 1900 AD corresponds to 1958 <strong>of</strong> the Vikram era,– It is popular in northern India and Gujarat.• The Saka era:– Begins with King Salivahana's accession to the throne.– The year 1900 AD would be 1823.– Popular in southern India, this reference in almost allastronomicalworks in Sanskrit written after 500 AD.– The Government calendar also follows the Saka era.<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 57<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 58NORTHSouth<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 59<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 6015
Rohini Shakat Bhed• Rohini Shakat Bhed isdefined as an event whereSaturn or Mars came insidethe triangle <strong>of</strong> Rohini.• Calculations with modernephemeris, its occurrencecan be dated.• The event last occurred in5284BC and then 9339 BEprior to that.<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 61 (Mahajani, Vahia, Apte and Jamkhedkar, <strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 622005)Nakshtras• Nakshatras are the path <strong>of</strong> Moon in the night sky. Zodiacs are the path <strong>of</strong>the Sun in the night sky.• Zodiacs were designed in Babylonia before 3000 BC.• Nakshatras appeared fully defined in Babylonia after 1000 BC.• Zodiacs are needed for people preoccupied with Seasons whileNakshatras are needed for people interested in calendar and time keeping.• Nakshatras therefore seem to be Harappan in origin who were seafearers.Vernal EquinoxSummer solsticeAvg Value VS Year from 3500 BC-2000 ADTHERE IS CLEAR EVIDENCETHAT NAKSHATRAS WEREDESIGNED AROUND 3000BC.Moon's Avg Value <strong>of</strong> Dec atpeak`5.004.504.003.503.002.502.001.501.000.500.00-4000 -3500 -3000 -2500 -2000 -1500 -1000 -500 0 500 1000 1500 2000 2500YearBhujale and Vahia, 2006<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 63<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 6416
Outstanding issues• Impact <strong>of</strong> astronomy on residential and burialsites• <strong>Origins</strong> <strong>of</strong> astrology• Affects <strong>of</strong> precession on the seasons• Mythologies, symbolisms and formalisation <strong>of</strong>astronomy• Records <strong>of</strong> comets and supernovaeIsn’t this more than enough for 1lecture?<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 65<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 66Acknowledgements• I want to acknowledge all the known and unknown Websources that I have used in the lecture.• My special thanks to WIKIPEDIA which provided some valuableinformation.• I want to thank my friends Sudha Bhujle, Kavita Gangal,Hrishikesh Joglekar, Parag Mahajani, Aniket Sule. I have stolenideas and images from all <strong>of</strong> them!• I want to particularly thank Dr. Jamkhedkar who has been myconstant source <strong>of</strong> inspiration on this subjects.• I want to express my apology to all those whom I may haveforgotten to thank.<strong>Origins</strong> <strong>of</strong> <strong>Astronomy</strong> 6717