1. Ancient Indian Astronomy

2. Hindu calendar Brahma lives 100 years (Brahman years, not human years)
One Kalpa coincides with one Day of Brahma’s 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

3. 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

4. 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.

5. 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

6. Astronomers Brahmagupta (~600CE) Devacharya (~600CE)
Estimated the Earth’s 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

7. 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

8. The Planets Budha – Mercury Shukra – Venus Ankgaraka – Mars
Intellect
Shukra – Venus
Refined, sensual
Ankgaraka – Mars
Burning coal
Brihaspati – Jupiter
Great protector
Shani – Saturn
Slow

9. 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!

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

11. 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.

12. 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!
Aryabhata’s constants are more accurate than the West’s at that time
Not this advanced in Babylonia
Cannot be from Babylonia!