Ancient Indian Astronomy

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Ancient Indian Astronomy
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Hindu calendar

• Brahma lives 100 years (Brahman years, not human
  years)
• One Kalpa coincides with one Day of Brahmas
  life.
• One Kalpa corresponds to 4,320,000,000 earthly
  years.
• Earthly time is divided into Yuga, or Ages which
  are
• Krita ( or Satya ) Yuga 4,800 years
• Treta-Yuga 3,600 years
• Dwapara-Yuga 2,400 years
• Kali-Yuga 1,200 years

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Calendar

• For a total of 12,000 years.
• The four Yuga make one Mahayuga
• The 12,000 years must be multiplied by 360, the
  days of the human year
• 12,000 x 360 4,320,000 years
• Every Kalpa has 1000 cycles of four Yuga
• 4,320,000 x 1000 4,320,000,000 years

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Astronomers

• Varahamihira (500CE)
• described the Earth as spherical and as being
  suspended in space
• Used latitude and longitude
• Described the stars as fixed and gave the
  planets a constant speed.

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Astronomers

• Aryabhata I (500CE)
• Heliocentric (somewhat) idea
• 1000 years before Copernicus and Galileo
• Described methods of eclipse prediction.
• Codified many trigonometric laws.
• Sin tables
• Value of pi
• Knew of most of the planets (at least 7) without
  a telescope

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Astronomers

• Brahmagupta (600CE)
• Estimated the Earths circumference as 5000
  yojanas (yojana 4.5 miles) Surprisingly
  accurate! (off by less than 10)
• Devacharya (600CE)
• First astronomer to describe a method for
  calculating the precession of the eqinoxes

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The Planets

• Hindu astronomers used epicycles (like Ptolemy)
  to describe the motion of the planets in a
  geocentric solar system.
• Epicycles are necessary to account for retrograde
  motion.
• Aditya the Sun
• Son of Aditi (the unchangeable)
• Soma the Moon
• Peace, gentleness

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The Planets

• Budha Mercury
• Intellect
• Shukra Venus
• Refined, sensual
• Ankgaraka Mars
• Burning coal
• Brihaspati Jupiter
• Great protector
• Shani Saturn
• Slow

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Interesting Notes

• Hindu texts speak of Pravaha, a celestial wind,
  the force that moves the planets.
• There is a famous Sanskrit saying when translated
  means, In all directions, Sun, Sun, Sun.
• Seems to be suggesting that all the stars are
  suns, just further away
• Olbers paradox long before Olbers!

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Invasion!

• With the invasion of the Moghuls, astronomy in
  India did not advance for some time.
• Think of what might have been achieved

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Controversy

• Throughout history some scholars have been
  determined to prove that these ideas and theories
  could not have originated in India
• 19th century notion that India did not have
  observational astronomy.

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Controversy

• More than 30 years ago, Roger Billard analyzed
  ancient calculations which were to predict the
  position of planets
• Compared to modern theory, they were surprisingly
  accurate!
• Aryabhatas constants are more accurate than the
  Wests at that time
• Not this advanced in Babylonia
• Cannot be from Babylonia!