Origins of Astronomy

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					                                                                  Events that shaped human
                                                         • The last ice age began about 120,000 years ago.
       Origins of Astronomy                              • The Last Glacial Maximum, occurred about 18,000 BCE.
                                                         • Between 15,000 BCE and 5,000 BCE, most of the
                                                           world's glaciers melted the sea reclaimed former
                                                           beaches and even valleys.
                                                         • This movement of the sea inland occurred in several
                                                            –   13,000 BC
                 Mayank Vahia                               –   9,000 - 8,000 BCE. 22 mm/year
                                                            –   6,000 BCE. 2 mm/year
   Tata Institute of Fundamental Research                   –   From 3000 BC, the rise is 7.5 mm/year.
               Mumbai 400 005                            • Myths of great floods occur in many of the world's

                   Origins of Astronomy            1                                 Origins of Astronomy       2

     End of Ice Age and Human
• The last great Ice Age ended around 15,000           AVERAGE
                                                       SNOW LINE
  years ago and that must have facilitated human

                   Origins of Astronomy            3                                 Origins of Astronomy       4

                               1,000,000 years in a nutshell!
                           •       Human race (Homo sapiens) first originate in Africa
                                   about million years ago.
                           •       They remain confined to central and northern Africa for
                                   almost 900,000 years!
                           •       Due to a mixture of reasons such as:
                               –     Sheer tireless desire to explore.
                               –     An overflow from population growth.
                               –     Inability of the local food sources to support a large human
                               –     Internal conflicts of personality within the population.
                               –     Differences in taste and preferred environment for settlement.

                           They migrate out of Africa about 100,000 years ago.

Origins of Astronomy   5                                Origins of Astronomy                          6

Origins of Astronomy   7                                Origins of Astronomy                          8

               Migration and evolution                                                                Astronomy
• Human race has gone through various stages of development.
   – Palaeolithic – First appearance of humans to 10,000 BCE. Neanderthal
                                                                                     • By all indications, serious astronomy begins in
     Man & Homo Erectus existed until 30,000 B.C. Stone tools of increasing            late Palaeolithic age itself.
     complexity mark this period.
   – Mesolithic – 11,000 to 9,000 BCE. Metals are used in this period.
   – Neolithic – pre-historic period 9,000 – 1,000 BCE. Sophisticated
     cultures and organised existence mark this age.                                 • Well accepted astronomical markings have
       •   Calolithic (Copper Stone) Age, 5500-3000 BCE.
       •   Bronze Age 3000 -1200 BCE.
                                                                                       been dated to 15,000 BCE
       •   Iron Age 1200 BCE -
       •   Silicon age 2000 AD -
   – Historic period.                                                                • We shall show later that stone carvings of much
• THESE PERIODS VARY FROM REGION TO REGION                                             earlier dates also exist.
                                  Origins of Astronomy                           9                       Origins of Astronomy                          10


                                                                                                                            Babylonian "map of the world" It
                                              Taurus                                                                        is the earliest extant map. The
                                                                                                                            clay tablet is 12.2 cms tall. The
                                                                                                                            map was composed in
                                                                                                                            Babylonia and is the only
                                                                                                                            Babylonian map drawn on an
                                                                                                                            international scale. It is a
                                                                                                                            Persian Period, (500 BCE) copy
                                                                                                                            of an original dating to late
                                                                                                                            eighth or seventh century BCE.

                                  Origins of Astronomy   prehistoric caves at   11                       Origins of Astronomy                          12
                                                         Lascaux in France.

                                                                                                           First steps
• Astronomy is the first ‘science’.
                                                                                     • Astronomy begins very early in Human life
• Sky obviously gets noticed quickly.
                                                                                     • The second thing we notice in the sky is
• In a steady landscape, it is the fastest moving thing                                the Moon
  (apart from animals and insects!).

• Sun rise and sunset are important for most life on
                                 Origins of Astronomy                       13                                Origins of Astronomy                14

                          Moon’s path                                                              Calculation of tithis
•   Moon moves only in a narrow region in the sky.
•   Moon visibly drifts in the night sky.                                          • Tithis are the dates of Lunar Calendar. It is related to the phase
                                                                                     of the moon.
•   It follows a specific path that is marked by a series of stars.
•   Moon waxes and wanes with a time period of 29/30 days.
                                                                                     Tithi = long. of Moon – Long. of Sun

•   At Full Moon the Moon rises at Sunset and then drifts towards the Sun
    and after New moon it rises later and later till it rises at Sunset again.     • Tithi remains the same until the Moon in increases its distance
                                                                                     from the Sun by 12 degrees. The complete revolution of the
•   Full Moon occurs near of different stars each month.                             Moon (29.5 days) occupies 30 tithis for 3600.
•   Synodic (Full moon to full moon) and Sidereal (w.r.t. distant stars) periods
    are different.                                                                 • Moon does not move at constant velocity so the length of tithis
•   Since the Sidereal period is 27 days, the sky can be divided into 27
    different parts where the Moon spends 1 day. This forms the basis of
    Nakshatras.                                                                    • The waning phase (from Full Moon to New Moon) is called
•   Moon gives us the concept of month, fortnight and week.
                                                                                     Krishna Paksha and the waxing phase (from New Moon to Full
                                                                                     Moon) is called Shukla Paksha.     Bhujle and Vahia, 2006
                                 Origins of Astronomy                       15                                Origins of Astronomy                16

  Names of tithis: (starting with Full Moon)
   Number   Phase        Tithi          Number    Phase       Tithi
     1      Krishna    Pratipada            16    Shukla    Pratipada
     2      Krishna     Dvitiya             17    Shukla     Dvitiya          • Sky is divided into patterns that we call
     3      Krishna     Tritiya             18    Shukla     Tritiya            constellations.
     4      Krishna    Chaturthi            19    Shukla    Chaturthi
     5      Krishna   Panchami              20    Shukla    Panchami
     6      Krishna    Shashthi             21    Shukla    Shashthi          • Star patterns on the path of the Moon are called
     7      Krishna    Saptami              22    Shukla    Saptami
     8      Krishna    Ashtami              23    Shukla    Ashtami
                                                                                Lunar Mansions (asterism) or Nakshatras.
     9      Krishna     Navami              24    Shukla     Navami
     10     Krishna     Dasami              25    Shukla     Dasami
     11     Krishna    Ekadasi              26    Shukla    Ekadasi
                                                                              • Sun mostly follows this path.
     12     Krishna    Dwadasi              27    Shukla    Dwadasi
     13     Krishna    Trayodasi            28    Shukla    Trayodasi
     14     Krishna   Chaturdashi           29    Shukla   Chaturdashi
                                                                              • The constellations on the path of the Sun are
     15     Krishna   Amavasya              30    Shukla    Purnima             called Rashis or Zodiacal Signs.
                           Origins of Astronomy                          17                         Origins of Astronomy        18

     Importance of Constellations
• Constellations help remember the sky

• They are small and easily recognisable.

• That they permit a universal definition of
  directions independent of geography

                           Origins of Astronomy                          19                         Origins of Astronomy        20

       Circumpolar constellations                                       Path of the Sun
                                                     • Sun mostly follows the path of the Moon. The difference is more
• Not all constellations rise and set.                 important than the similarity.

                                                     • Since the Sun is very bright, Sun’s path is inferred by looking at
                                                       the constellations just before Sunrise or just after Sunset.
• Pole star never sets and constellations close to
  it also do not set.                                • The path of the Sun is divided into 12 Rashis or Zodiacal signs.
                                                       Roughly 2.25 Nakshatras fit into a rashi.

                                                     • The Sun returns to the same Rashi when the Moon completes
• This gives a fixed (north) direction and             12 revolutions.
  circumpolar constellations permit determination    • 12 months therefore make one year (approximately)
  of exact (geographic) north.
                     Origins of Astronomy      21                               Origins of Astronomy                22

                     Origins of Astronomy      23                               Origins of Astronomy                24

                              The East
    • The Sun does not rise in the exact (global) east,
      i.e. it does not rise exactly at the point between
      north and south.

    • It rises in the eastern direction and sets in the
      western direction

    • But within that, the sun rises exactly in the (local)
      east i.e. the line joining sunrise point and sunset
      point is perpendicular to the line joining the
      observer to the north.

                                Origins of Astronomy                     25       Origins of Astronomy   26

                  Sunrise and Sunset
• The Sun rise point drifts North of East to South of East

• On Equinox (Spring or Autumn), the Sun rises exactly in the (global) East all
  over the world and the day and night are of equal length.

• How high the Sun rises depends on latitude.

• For regions within the Tropics, the day on which the Sun comes exactly
  overhead depends on the exact locations and 2 such days occur in a year.

• For regions in the North, Summer Solstice is the day of highest sunrise and
  for the South it is the Winter solstice (as experienced in the North).

                                Origins of Astronomy                     27       Origins of Astronomy   28

         Date and Time of Solstice and Equinox

                                                                                               Sun and seasons
              day   time    day   time     day       time    day   time
       2002   20    19:16   21    13:24    23        04:55   22    01:14        • Any observer will notice this drift of the Sunrise point
       2003   21    01:00   21    19:10    23        10:47   22    07:04
       2004   20    06:49   21    00:57    22        16:30   21    12:42
                                                                                  (against the background geography) and its relation to
       2005   20    12:33   21    06:46    22        22:23   21    18:35          seasons.
       2006   20    18:26   21    12:26    23        04:03   22    00:22
       2007   21    00:07   21    18:06    23        09:51   22    06:08
       2008   20    05:48   20    23:59    22        15:44   21    12:04        • If you reside in cold regions outside the tropics, Sun,
       2009   20    11:44   21    05:45    22        21:18   21    17:47          and its location become more important than the
       2010   20    17:32   21    11:28    23        03:09   21    23:38
       2011   20    23:21   21    17:16    23        09:04   22    05:30
       2012   20    05:14   20    23:09    22        14:49   21    11:11
       2013   20    11:02   21    05:04    22        20:44   21    17:11
       2014   20    16:57   21    10:51    23        02:29   21    23:03
                                                                                • These cultures therefore become Sun worshipers.
                              Origins of Astronomy                         29                           Origins of Astronomy           30

          Winters and Summers                                                                   Sun and Rashis
• For Northern Hemisphere, winter is the time the                               • The constellations at Sunrise change with time.
  Sun spends south of equinox.                                                  • The constellations on the Sun’s path (Rashis) are so
                                                                                  designed that in 1 lunar Synodic month (30 days) the
                                                                                  Sun moves 1 Rashi. There are 12 Rashi.
• By this count, there are 187 days for summer
  and 178.4 for winter. The winters are shorter                                 • Since 360 < 365, seasons begin to drift 6 to 7
  and colder in the northern hemisphere.                                          days/year and in 5 years, addition of a month is
                                                                                  required to synchronise the calendar with the seasons.

                                                                                • This is called the intercalary month.

                              Origins of Astronomy                         31                           Origins of Astronomy           32

                                                                                               Sun and Moon together
                                                                                • When the Moon returns to a Nakshatra it doesn’t have the same phase
                                                                                • Phase of the Moon is decided by its distance from the Sun
                                                                                • At each of Full Moon, the Moon is 2.25 Nakshatras away from the previous
                                                                                  Full 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 is
                                                                                  spinning in the same direction as it is rotating.
                                                                                • The Sun’s plane (Orbital plane of the Earth around the Sun or the Ecliptic) is
                                                                                  inclined to the Moon’s path by 5o.

                                                                                • Point of intersection of the two planes are called the nodes. These nodes are
                                                                                  called Rahu and Ketu. These nodes rotate with a period of 18.6 years.

                          Origins of Astronomy                             33                                    Origins of Astronomy                                34

          Celestial Equator and Ecliptic                                                             Ecliptic and Orbit of Moon

                                 NCP                                                                                    NCP
                                                                                  Ketu (Descending Node) at VE
                                                                                                                                                   Lunar Orbit
                                                          Ecliptic                                                                                  Ecliptic

                                                           Celestial Equator                                                                         Celestial Equator

                                                                 between the
                                                                 two is 23.5o

          Motion of Sun                          VE = Vernal Equinox
          and Moon
                                                 SS = Summer Solstice
                                                 AE = Autumnal Equinox
                                                 WS = Winter Solstice                                                      Rahu (Ascending Node) at VE
Hrishikesh Joglekar       Origins of Astronomy                             35                                    Origins of Astronomy                                36

Ecliptic and Orbit of Moon                           Ecliptic and Orbit of Moon

               NCP                                                  NCP

        Origins of Astronomy                    37           Origins of Astronomy   38

Ecliptic and Orbit of Moon                           Ecliptic and Orbit of Moon

               NCP                                                  NCP

                  Rahu (Ascending Node) at WS
        Origins of Astronomy                    39           Origins of Astronomy   40

Ecliptic and Orbit of Moon          Ecliptic and Orbit of Moon

               NCP                                 NCP

                                                      Rahu (Ascending Node) at AE
        Origins of Astronomy   41           Origins of Astronomy                    42

Ecliptic and Orbit of Moon          Ecliptic and Orbit of Moon

               NCP                                 NCP

        Origins of Astronomy   43           Origins of Astronomy                    44

Ecliptic and Orbit of Moon                                             Ecliptic and Orbit of Moon

               NCP                                                                    NCP

                  Rahu (Ascending Node) at SS
        Origins of Astronomy                    45                             Origins of Astronomy                    46

Ecliptic and Orbit of Moon                                             Ecliptic and Orbit of Moon

                                                     This complete cycle
               NCP                                   takes 18.6 years                 NCP

                                                                                         Rahu (Ascending Node) at VE
        Origins of Astronomy                    47                             Origins of Astronomy                    48

                       Planets                                                       Planet periods
• Of the ~ 6,000 stars visible at night (from ~ 1022 stars),      •   Mercury goes around the Sun 88 (earth) in days.
  there are 5 objects apart from Sun and Moon which are not       •   Venus takes 0.61 (earth) years
  stationary. They are called Planets.                            •   Mars takes 1.88 (earth) years
• These are Mercury, Venus, Mars, Jupiter and Saturn.             •   Jupiter takes 11.9 (earth) years
                                                                  •   Saturn takes 29.4 (earth) years
• Their path is not random. They move more or less on
  the same path as the Sun and the Moon.                          • Mercury goes 30o from the Sun
                                                                  • Venus goes 60o from the Sun
• Mercury moves the fastest and Saturn the slowest.

                        Origins of Astronomy           49                                    Origins of Astronomy                    50

                                                                                 Ancient Calendars
               Making calendars
                                                               • Vedanga Jyotish (1200 BC) This is the oldest Lunar calendar. It
                                                                 contains a 5-year Yuga of 62 synodic lunar months.
• In order to keep track of time over long periods
  of years, a method of counting has to be                     • Brihaspati samvatsar (year) chakra: 60 year cycle of Jupiter. The years
                                                                 have names like ‘Prabhav’, ‘Vibhav’ etc.
  devised. This is called a calendar.
                                                               • The Griha-parivritti cycle: It consist of 90 solar years. The length of 1
                                                                 year being 365.2586 days. The year commences with sun entering
• Apart from counting, special markers are                       Mesha (Aries sign). This type of calendar is used in southern peninsula
                                                                 of India especially in Tamilnadu.
  introduced to ensure that the counting is
  correct.                                                     • Saptarshi era: consists of cycles of 2700 years. It originated with the
                                                                 supposition that seven Rishis stay in each Nakshatra for 100 years.
                                                                 This era was in use in Kashmir.
• It also encourages study of rare events by                   • The currently used calendar is Luni-solar calendar in which each
  pointing out their rarity.                                     month is synodic lunar month of 29.5 days. One year consists of 12
                                                                 such months = 254 days. The remaining 11 days of the year are
                        Origins of Astronomy           51
                                                                 adjusted in Adhik maas (intercalation month) that occur generally 52
                                                                                              Origins of Astronomy
                                                                 the 3rd, 5th, 8th,11th,14th,16th and 19 year cycle of years.

            The Saptarshi Era                                                                    Saptarshi Era
• An interesting time line in the Vedic literature is
  the Saptarshi Era.

• It states that the Saptarshi constellation moves
  into different Nakshatras giving different eras. It
  is generally assumed to be wrong.

• However, the exact manner of the definition
  clearly shows that the starting date of the Era is
  2300 BC and originates in southern Gujarat.
                                            (Sule, Vahia, Bhujle, 2005)        2100 BC                                          2000 AD
                     Origins of Astronomy                           53                                   Origins of Astronomy                       54

       Yuga in Vedic Literature                                                   Yuga: Recent interpretation
                                                                          •   There are 4 Yugas the duration scale of 4:3:2:1
                                                                          •   Satya Yuga or Krita Yuga (1,728,000 years),
• Yuga concept is introduced in Vedic astronomy                           •   Treta Yuga (1,296,000 years) ,
  to synchronise solar and lunar calendars.                               •   Dvapara Yuga (864,000 years)
                                                                          •   Kali Yuga (432,000 years)
• The yuga period of five years, whose
  constituent years are called samvatsara,                                •   Satya Yuga or Krita Yuga - dhyana (meditation)
  parivatsara, idavatsara, anuvatsara, and                                •   Treta Yuga - yajna (sacrifice)
  idvatsara, has been in use since Vedic times.                           •   Dvapara Yuga - archana (worship)
                                                                          •   Kali Yuga - daana (alms)
• However, there are actually 1826.2819 days in
  a yuga of five solar (sidereal) years.                                  •   More acceptable interpretation is that they are Daivik years or days. This
                                                                              gives Yugas to be 1200: 2400: 3600: 4800 years (total 12,000 years).
  Furthermore, there are 1830.8961 days in a
  period of 62 lunar months. It is suggested that                         •   It is believed to have begun with the death of Krishna in 3102 BC?????.
  ~4.5 days were dropped as ‘reset error’.                                •   This reference of time is still used in religion and literature.
                     Origins of Astronomy                           55                                   Origins of Astronomy                       56

               Calendars in use
• The Vikram era:
  – Begins with the coronation of King Vikramaditya.
  – The year 1900 AD corresponds to 1958 of 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 all-
    astronomical works in Sanskrit written after 500 AD.
  – The Government calendar also follows the Saka era.

                          Origins of Astronomy                 57   Origins of Astronomy   58



                          Origins of Astronomy                 59   Origins of Astronomy   60

                                                                                                                                                                              Rohini Shakat Bhed
                                                                                                                                                              • Rohini Shakat Bhed is
                                                                                                                                                                defined as an event where
                                                                                                                                                                Saturn or Mars came inside
                                                                                                                                                                the triangle of Rohini.
                                                                                                                                                              • Calculations with modern
                                                                                                                                                                ephemeris, its occurrence
                                                                                                                                                                can be dated.
                                                                                                                                                              • The event last occurred in
                                                                                                                                                                5284BC and then 9339 BE
                                                                                                                                                                prior to that.

                               Origins of Astronomy                                                                                           61              (Mahajani, Vahia, Apte and Jamkhedkar, Astronomy
                                                                                                                                                                                             Origins of              62

                           Nakshtras                                                                                                                                              Vernal Equinox

•   Nakshatras are the path of Moon in the night sky. Zodiacs are the path of
    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 while
    Nakshatras are needed for people interested in calendar and time keeping.
• Nakshatras therefore seem to be Harappan in origin who were sea
  fearers.                                                                                                                                                                            Summer solstice

                                                                                   Avg Value VS Year from 3500 BC-2000 AD
                                             Moon's Avg Value of Dec at


THERE IS CLEAR EVIDENCE                                                   4.00

THAT NAKSHATRAS WERE                                                      2.50

DESIGNED AROUND 3000                                                      1.00
BC.                                                                          -4000 -3500 -3000 -2500 -2000 -1500 -1000 -500   0   500   1000 1500 2000 2500


Bhujale and Vahia, 2006
                               Origins of Astronomy                                                                                           63                                              Origins of Astronomy   64

               Outstanding issues
• Impact of astronomy on residential and burial
• Origins of astrology                                              Isn’t this more than enough for 1
• Affects of precession on the seasons                                            lecture?
• Mythologies, symbolisms and formalisation of
• Records of comets and supernovae

                          Origins of Astronomy              65                   Origins of Astronomy   66

• I want to acknowledge all the known and unknown Web
  sources that I have used in the lecture.
• My special thanks to WIKIPEDIA which provided some valuable
• I want to thank my friends Sudha Bhujle, Kavita Gangal,
  Hrishikesh Joglekar, Parag Mahajani, Aniket Sule. I have stolen
  ideas and images from all of them!

• I want to particularly thank Dr. Jamkhedkar who has been my
  constant source of inspiration on this subjects.

• I want to express my apology to all those whom I may have
  forgotten to thank.
                          Origins of Astronomy              67


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