Ancient astronomical observatories

“FUTURE OF THE PAST: ICTS Mini Workshop, Mangalore 22-26 November 2011”

Stonehenge

FUTURE OF THE PAST: ICTS Mini Workshop, Mangalore, 22-26, 2011

Ancient astronomical observatories

Srikumar M. Menon

Manipal University, Manipal

Nilaskal


The Fascinating Heavens – the sky as a cultural resource


Supernova?

Scorpio?

Petroglyph discovered in White Tank Regional Park, Arizona



The supernova of 1006AD



Prehistoric Astronomy: evidence for observing instruments?

#Rao, N. K., Bull. Astr. Soc. India (1993) 21, 67-77.

*Rao, N. K., Bull. Astr. Soc. India (2005) 33, 499-511.

**Aveni, A., Tropical Astronomy, Science (1981)

Mayan Zenith Tubes**

Brahmagiri#

Harappan Gnomons?*

Hanamsagar*


A bit of Positional Astronomy

The Celestial Sphere



Co-ordinate Systems



Declination (0o to 90o N & S)

Right Ascension (0h to 24h), measured from vernal or spring equinox


The Cycle of the Sun


The Solstice



The Solar Cycle (for a location N of the Equator)



Against a convenient skyline...


E W

N

S

Variation

of

Sunrise

points

during

different

months

Saptarshi rise point

locator

Constellation

locators

Courtesy: Prof. Mayank Vahia, TIFR

Stone Markers?


The Lunar Cycle

The Cycle of the Moon


18.6years

Monthly swing (Minor Standstill)

Monthly Swing (Major Standstill)

Horizon Horizon

18.6years

The Cycle of the Moon


Major standstill northern moonrise

Minor standstill northern moonrise

Minor standstill southern moonrise

Major standstill southern moonrise

Major standstill northern moonset

Minor standstill northern moonset

Minor standstill southern moonset

Major standstill southern moonset

N

Lunar Alignments and Sightlines


Celestial Alignments and Sightlines…


Precession of the Equinoxes

Precession is due to a gyroscopic wobble of earth's spin axis that takes

26,000 years to complete. In this wobble motion, the tilt of the earth stays

roughly constant at 23.4 degrees but the orientation is always changing.

Precession



Precession

• The north star

Polaris is

drifting. It is

only "north

star" by

coincidence

today. Vega will

be our north

star for a time

in the distant

future.

• Since the point where

the projection of the

rotation axis of the

Earth strikes the

Celestial Sphere

moves around, this

means that the North

Celestial Pole moves

around in a circle

among the stars. This

produces changes in

the coordinates of

stars. Today, it is

fortuitous that the

North star is Polaris. At

other times, other stars

were or will be the

North star!


Precession



Precession - what it implies for us…

Due to Precession, the position of Equinox Sunrise and Sunset, Solstice

Sunrise and Sunset etc. will be different for different eras.

So one has to account for Precession while assessing monuments for

alignments with these phenomena…

Amount of Precession: * #

One complete cycle = 25,800 years

Equinoxes move Westward by ~ 50”.3 per year

Which is 1o every 71.6 years

*Narlikar, J. V., The Scientific Edge: The Indian Scientist from Vedic to Modern Times (2003) Penguin Books, pp 7 #Ridpath, I. (ed.), Norton’s Star Atlas and Reference Handbook (Epoch 2000.0) (1998) Addison Wesley Longman Ltd., Pp 43


Archaeoastronomy and Related Fields

The study of astronomical practices, celestial lore, mythologies, religions and

world-views of all ancient cultures is called ARCHAEOASTRONOMY.

Archaeoastronomy, in essence, is the “anthropology of astronomy”.

The study of the practice of astronomy using both the written and unwritten

records. It began as a meeting ground for three established disciplines:

(Aveni, A., Journal of Archaeological Research, Vol.11, No.2, 2003)

Astroarchaeology – a methodology for retrieving astronomical information

from the study of alignments associated with ancient architecture. (Hawkins

1966)

Ethnoastronomy – a branch of cultural anthropology that develops an

understanding of cultural behavior as gleaned from indigenous perceptions of

events in the heaven. (Fabian, 2001)


The Stonehenge Controversy…

Stonehenge – an exceptional monument..?



Decades of research by several workers…



A composite structure… (~3500 BC – 1500 BC)



Too many celestial alignments..?



An eclipse predictor too..?


Alexander Thom and his Work…

“…long, patient, accurate and modestly pursued work” on a large number of

sites….



Accurate surveys of a large number of sites…


Mainly alignments in megalithic sites; but also on their design (geometry)….



…for a large number of sites

The importance of measuring Orientations…


Is an inferred sightline actually

intentional or a chance alignment?

The BIG Question…


Megalithic Calendar Devices..?

Stone alignments and Avenues prime candidates…

Topography to be taken into account too while considering sightlines…

Horizon visibility from each backsight to be considered too…

Callanish

Carnac


Teotihuacan – Astronomical Town Planning..?*

*Krupp, E. C., In Search of Ancient Astronomies (1977) Doubleday, New

York.


Teotihuacan – Astronomical Town Planning..?


Chankillo: The Mystery of the Thirteen Towers



*The thirteen towers situated on a N-S ridge

within a 4th Century BC ceremonial complex.

Most prominent feature – the citadel (a

fortified temple?)

The towers vary in area (75 – 125 m2 and in

height (2-6m)

Regularly spaced – gap between adjacent

towers vary from 4.7m – 5.1m

A structure on the West 235m away with a

corridor to a door-less opening facing towers

A small, isolated building on Eastern side

almost mirror-image of W observing position

in distance and elevation

*Ghezzi, I. and Ruggles, C., Chankillo: A 2300-Year-Old Solar Observatory

in Coastal Peru, Science (2007) Vol. 315



Sunrise at the 13 towers…



Sunset at the 13 towers…


Dholavira: the structure in the “bailey”


Dholavira: the structure in the “bailey”

Play Video!!


“Every age has the Stonehenge it deserves – or desires.” – Jacquetta Hawkes, 1967

Whose point of view..?

Equinox, solstice…

Alignments

Sepulchral

BRW…

Stratigraphy Form

Space Order!


The REAL thing!


Nilaskal

Thank You!

FUTURE OF THE PAST: ICTS Mini Workshop, Mangalore, 22-26, 2011

Ancient astronomical observatories

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