# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: Astronomy & math in ancient Babylon
Date: 2016 Feb 1, 13:16 -0500

Hello Alex

Correct!

Your explanation of the Babylonian "system" is far better than mine.  Once the journalist described it as a description of motion against the firmament, I assumed it was the equivalent of Ptolemy's description and stopped reading.  To hear from you that it was not even that equivalent, further sinks the Babylonian "system" in my estimation!  Many early astronomers noted the apparent motion of planets in the sky and attempted to describe that motion.  The Babylonian "system" is therefore just another attempt at description.

Of course the NA is earth-centered!  It has to be to permit observers to match observational data to computed data.  The observer is located on the surface of the earth, the position to be "fixed" is on the surface of the earth, so it follows that the frame reference of the NA is the earth.   I think of the NA as an artifact of the Copernican system, as observed from the earth.  Forgive my lack of precise terms in this description.

On Jan 31, 2016 9:00 PM, "Alexandre Eremenko" <NoReply_Eremenko@fer3.com> wrote:

```Dear Brad,

You overestimate Babylonian astronomy:-)
They did not even ask the question where it is centered, and how the planets really move in space.

What they did (roughly speaking) is recording the motion of a planet (like SHA, but they used anther angle)
as a function of time, and then approximated this by a piecewise-linear function.
This has nothing to do with any "model" in the sense Western science gives to this word.
This was just "fitting the data".

Then you underestimate earth-centered systems:-)
Have you ever noticed that the modern Nautical Almanach uses Earth-centered coordinates?
So they are not so hopelessly backward after all:-)

Alex.
________________________________________
Sent: Sunday, January 31, 2016 7:29 PM
To: eremenko---.edu
Subject: [NavList] Re: Astronomy & math in ancient Babylon

I saw that article and was excited right up until I realized the model described was the earth centered solar system.

Bras

On Jan 31, 2016 1:10 PM, "Noell Wilson" > wrote:

The right people looked at come clay tablets in the British Museum and recognized that Babylonian astronomers in the 350 to 50 B.C. Period described the unique motion of Jupiter across the sky with graphs of position versus time. "It was an abstract concept not known elsewhere at the time. 'It anticipates integral calculus.' "

http://www.nytimes.com/2016/01/29/science/babylonians-clay-tablets-geometry-astronomy-jupiter.html?_r=0

Regards, Noell

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