Indus Valley Civilization.

[Beagle]

No, I think the author is providing the degrees and minutes based on the info from the Rig Veda.

I may have to get a better explanation, but see what you think Monk and thanks in advance. There's no great hurry, I'm not going anywhere for the next 20 years or so.

[Digit]

Uuumh!

[Forum Monk]

It is not easy to look at ancient astronomy texts and apply a modern interpretation to them. For example for the purpose of astrology, the ecliptic (path of the sun) is divided into 12 equal zones occupied by the constellations of the zodiac. So each zone is 360/12 = 30 degreees wide. In science the constellation boundaries are not equal width. So to accurately interpret ancient knowldege, it is necessary to know, how many zones did they acknowledge and where are their borders. Further, the great circle of precession is at best estimated by ancients who probably had no real understanding of the process with contributed to precession. The common figure is 1 degree per 72 years, making a complete cycle in 360 x 72 years = 25920 years. (Science gives a figure more or less depending on many factors - its changing, not constant). Finally we must establish a starting point for calculations so lets say the sun entered Pisces in 70 BC, every 2160 years it will pass into the next zone. So here is a table of zones and dates based on the previous assumptions:

Cancer 8710 BC
Gemini 6550 BC
Taurus 4390 BC
Aries 2230 BC
Pisces 70 BC
Aquarius 2091 AD

If you want to explore it deeper, let me know. I would be glad to.

[Minimalist]

Yes, one of Hancock's most interesting chapter had to do with the frequency that "precessional numbers" or variants thereof show up in ancient mythology.

[Forum Monk]

The entire concept of "precessional numbers" is some kind of strange numerology which I can not fully comprehend. Precession was not known to have been calculated until Hipparcos in the 2nd century iirc. There is a recurring theme of 72 or 36 which people call precessional and many say the ancients had knowledge of astronomical precession, but there is no real "smoking gun" text which demonstrates it. It is noticable if you carefully record and track stellar movements eventually you will notice after several generations, a general shift northward of all constellations at a more or less constant rate.

I have always wondered: if you supposedly have knowledge of precession, why built a temple to align with a star if you know that soon enough, the alignment will no longer be valid. This tells me a) they DID NOT align to stars or b) they DID NOT know about precession.

[Minimalist]

Precession was not known to have been calculated until Hipparcos in the 2nd century iirc.

Exactly Hancock's point.

By poor analogy, America was still here even if the Europeans did not know about it. Similarly, the mechanics of precession existed even if it took the Greek Hipparchus to claim the discovery. But, if ancient myths keep using variants of those numbers..........................

[Forum Monk]

In my opinion you have to put limits and rules on the use of the numbers, I have seen many many multiples of these numbers and people claim these multiples are also precessional. If you multiply and divide numbers enough you will find one which suits your point. Also, since 72 is the years per degree in a precessional cycle, the culture using it must also divide the year into 360 increments. Apart from perhaps the Sumerians, I am not sure if the 360 degree circle was a universal standard.

[Minimalist]

There's another problem with it.

The concept of the Zodiac would have to be much older than we currently assume...of course, it could suffer from the same problem as precession. It needed a Hipparchus to publicize it.

[Beagle]

http://en.wikipedia.org/wiki/Hindu_astronomy

The beginning of the Saptarsi [4] calendar, which is still used in parts of India, is often placed at 3076 BCE[5], but references by Greek historians (Pliny and Arrian)[6] could possibly indicate an earlier beginning of the calendar at 6776 BCE.[7] These Greek historians wrote that 153 or 154 kings passed between between Dionysos and Chandragupta, and according to the Puranas there were about 143 kings during this period.[8] The Satapatha Brahmana says that the rsis and the Krittikas were married, and the Puranas says that the rsis are 100 years in each naksatra, which would amount to a cycle (cakra) of 2700 years. In some texts, Sravana is the first naksatra (which could be placed at the "Greek date" of 6676 BCE), and the Mahabharata War occurred with the Saptarsi in the Magha, or 2700 years later.[9] It was argued by Cunningham that during Pliny's and Arrians time, Asvini marked the beginning of the naksatras, as is the case in Surya Siddhanta 8.9. Thus one could calculate a date of 3976 BCE for the beginning of the cakra, or 2700 years after 6676 BCE.[

I decided to check Wikis' explanation of Vedic astronomy. It's not the best, but it's very mainstream.

The system used was sidereal. That doesn't tell me anything. I think though, from what I'm reading, most scholars accept the Indian method as accurate time keeping.

[Digit]

Just to make things more difficult Beag the precession is not a constant ie linear effect and does not actually scribe a truly circular path. What the shape was in the past, and how much it varied from truly circular, is beyond my ability to calculate.
Any calculation from eons ago, unless accompanied by referrence points, must be rather loose I'm afraid.

[Forum Monk]

I decided to check Wikis' explanation of Vedic astronomy. It's not the best, but it's very mainstream.

The system used was sidereal. That doesn't tell me anything. I think though, from what I'm reading, most scholars accept the Indian method as accurate time keeping.

I am reluctant to try and understand these ancient terminologies; naksatra and cakra and so on. Now sidereal means something to me.

If you look at stars tonight and note the position of a particular star at midnight, the next night, you will notice at midnight that star is actually slightly farther west. This makes the stars appear to rotate westerly throughout the year with respect to our solar calendar. In fact one "star" day is about 4 minutes shorter than one "solar" day. This star day is a "sidereal" day (23 hours 56 minutes). It is the actual amount of time it takes the earth to rotate one time on its axis. This means every 23h 43m a star will appear at exactly the same location in the sky. So why the difference between a star day and a solar day? As the earth rotates counterclockwise, it is revolving around the sun counterclockwise. In the following drawing, note the angle between the star direction and the sun direction (about 225 degrees)


In this diagram, the next night, because the earth is moving around the sun, the angle has now increased by 4 acrminutes:


So true rotation time is sidereal time. The slightly longer solar day is due to the earths movement around the sun. See the next post for what it means.

[Forum Monk]

What are the implications of a sidereal time versus solar time? I can't say because it depends on what was being timed. It is impractical to set a clock or calendar to sidereal time because soon you are out of sync with the sun, and soon your festival is at night or perhaps a different season all together. The rising/setting of the sun is a more natural clock for festivals, etc. In any case, whether using sidereal or solar day, one is still faced with the fact that the earth actually takes 365.25 days to revolve around the sun. So the entire year slips 1/4 of a day per year which is why we have leap years every fourth year. (Ancients also had adjustments for this). Bottom line: I don't know what is meant when they say the ancient Indians used a "sidereal system".

[Digit]

The reason I left this one to you Monk is that unless someone can show the methods of measurement it all comes down to educated guesswork. Let's face it, we've had enough trouble over the years with the cubit.
The only way I can see to relate ancient texts in these matters is if the ancients give us a calendrical reference that we can identify and a physical one against a fixed, and identifiable, star.

[Forum Monk]

The real problem with archaeoastronomy is not the science of astronomy and detemining alignments, planetary postions, etc. but rather it is interpreting the meanings in the texts and the architecture. For example, many of the omen texts of the ancient babylonian are often interpreted to describe eclipses. But the text is often very vague and can just as easily be interpreted as a sky darkening due to a thunder storm or freakish weather event. Who can say for sure? And yet whole historical chronologies are built around these.

[Digit]

Agreed Monk, but what I was trying to explain was that in the absence of such information as will permit of their constellations, star names etc, one star, positively identified and disapearing below the horizon, would help set a calendrical date, time measurements, if any, and the variations, if any, of the precession.
As regards the precession, it must have varied over geological time if only because the Earth's rotation has slowed, this would decrease any bulge in the Earth and that in turn should lessen the the dia of the precession's wanderings.