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Dgennero
2009-Feb-06, 02:58 PM
...and other cosmic events before Newton?
I've heard that in ancient cultures it has been done (Greece, Egypt, China, Maya...)
How could they predict eclipses?
And how would an amateur astronomer without computers go about it today ("dead reckoning" (*), so to speak) ?

(*) ok, pocket calculator would be allowed.

Hornblower
2009-Feb-06, 03:10 PM
...and other cosmic events before Newton?
I've heard that in ancient cultures it has been done (Greece, Egypt, China, Maya...)
How could they predict eclipses?
And how would an amateur astronomer without computers go about it today ("dead reckoning" (*), so to speak) ?

(*) ok, pocket calculator would be allowed.
By keeping records of observations over many centuries, the ancient astronomers could recognize recurring patterns such as the Saros cycle of the Moon's motion, make a reasonable assumption that the cycle would continue to repeat, and calculate an extrapolation of the cycle. No knowledge of a theory of gravity was needed.

Murphy
2009-Feb-06, 06:55 PM
Yeah, people have generally been able to predict such things since at least the Bronze Age, and probably earlier in the Neolithic (i.e. the builders of Stonehenge probably had a good idea about it).

Having said that, it seems there were still some people's who had no idea about eclipses as late as the Middle Ages, I think there was once a battle involving the Mongols in which there was an unexpected Solar eclipse in the middle of the fighting and (I memory serves me), one side thought it was a supernatural sign and ran away (though I can't remember if it was the Mongols or their opponents).

mugaliens
2009-Feb-07, 04:33 PM
While I've strong confidence and reason to believe the builders of Stonehenge were fully capable of determining the equinoxes and solstices (which is a piece of cake, even for stone-agers), I do not believe they possessed the skills necessary to accurately predict lunar eclipses, except perhaps a few days in advance (by looking at a waning Moon approaching the Sun).

ngc3314
2009-Feb-07, 05:02 PM
I do not believe they possessed the skills necessary to accurately predict lunar eclipses, except perhaps a few days in advance (by looking at a waning Moon approaching the Sun).

That wouldn't be a good way to predict lunar eclipses!

With a long enough timespan, they could notice the Saros cycle and start with times when an eclipse might occur. (I've read that the Maya started this way, from strictly numerical patterns rather than a geometric model of the motions).

Centaur
2009-Feb-07, 05:19 PM
...and other cosmic events before Newton?
I've heard that in ancient cultures it has been done (Greece, Egypt, China, Maya...)
How could they predict eclipses?
And how would an amateur astronomer without computers go about it today ("dead reckoning" (*), so to speak) ?

(*) ok, pocket calculator would be allowed.

Both solar and lunar eclipses repeat over a Saros cycle of 223 lunations (18.03 years). It was not that difficult for some ancient societies to figure that out. Aristotle explained the physical causes of eclipses in the fourth century BC, and apparently was passing along already known information. The application of the patterns became even more sophisticated during the Middle Ages, but it wasn’t until the Renaissance that prediction methods were significantly improved by a better understanding of celestial mechanics.

George
2009-Feb-07, 05:26 PM
Here (http://eclipse99.nasa.gov/pages/traditions_Calendars.html) is a short article from NASA on ancient eclipses.

Surprisingly, I used Starry Night Pro and entered the documented May 3rd 1375 BC eclipse near today's Tripoli, and it demonstrated that there was one. That's some significant accuracy I never expected in the software.

Cougar
2009-Feb-07, 06:15 PM
By keeping records of observations over many centuries, the ancient astronomers could recognize recurring patterns....
...people have generally been able to predict such things since at least the Bronze Age, and probably earlier in the Neolithic...

So that's generally around 3000-1000 BC? Egyptian society well under way. But "keeping records over many centuries" would be tough if it was 10,000 to 20,000 BC and you had to invent the medium and the method for keeping records... well, and the whole idea of keeping a "record" in the first place. But that's about the time1 (http://www.touregypt.net/ebph3.htm) early agriculture around the Nile would have made such patterns and correlations more... associated with one's livelihood. And the beginnings of agricultural stability would likely have given the early inhabitants of the Nile region a little extra time to sit around, look around, and think about such things.

Hornblower
2009-Feb-07, 08:41 PM
So that's generally around 3000-1000 BC? Egyptian society well under way. But "keeping records over many centuries" would be tough if it was 10,000 to 20,000 BC and you had to invent the medium and the method for keeping records... well, and the whole idea of keeping a "record" in the first place. But that's about the time1 (http://www.touregypt.net/ebph3.htm) early agriculture around the Nile would have made such patterns and correlations more... associated with one's livelihood. And the beginnings of agricultural stability would likely have given the early inhabitants of the Nile region a little extra time to sit around, look around, and think about such things.
I think the period of about 3000-1000 BC is about right for Egypt and especially Mesopotamia. The British authors Stephen Toulmin and June Goodfield, in their book The Fabric of the Heavens, wrote at length about the Babylonians in the latter region. The Babylonians looked upon the Sun, Moon and planets as gods and were very much interested in ascertaining their recurring patterns of motion. They had an accurate calendar and kept good records of their observations, and wrote them down on clay tablets that have survived to the present day. If I am not mistaken, Aristotle and his fellow scholars found these records to be valuable in developing their theories.

The last time I looked, within the past two years, that book was available on Amazon.

mugaliens
2009-Feb-07, 09:34 PM
That wouldn't be a good way to predict lunar eclipses!

Well... It's Saturday. I'm having fun. Just call me moonbrain!

Tensor
2009-Feb-08, 03:34 AM
Yeah, people have generally been able to predict such things since at least the Bronze Age, and probably earlier in the Neolithic (i.e. the builders of Stonehenge probably had a good idea about it).

Having said that, it seems there were still some people's who had no idea about eclipses as late as the Middle Ages, I think there was once a battle involving the Mongols in which there was an unexpected Solar eclipse in the middle of the fighting and (I memory serves me), one side thought it was a supernatural sign and ran away (though I can't remember if it was the Mongols or their opponents).

Actually, it wasn't the mongols, it was between Lydia and Medes in 585 BCE. Here (http://www.wired.com/science/discoveries/news/2008/05/dayintech_0528)is the story. Although is may seem remarkable that Lydia and Medes never again fought, in reality, the Persian empire overran both countries forty years after the battle in 546 BCE.