Saturday, August 19, 2017

Predicting the Eclipses

I am loving living in Ireland, and except for missing my friends, I'm not homesick.

But I am so bummed to be missing the eclipse. I am one of those people who would have arranged the transport and lodging a year in advance to see a total eclipse. I missed the totality in 1979, because I was only 17 and living in Fresno, and traveling to Washington State was impossible. At that time, I had only been to San Francisco once, and never to Los Angeles.

I could have predicted I'd feel this way.

This weekend the whole world is looking toward the eclipse, where the moon will eat the sun, and bring down the ridiculous King.

*crossing fingers*

The desire to predict the eclipses is an ancient preoccupation, and the tools devised are the earliest computers we know of, like the Antikythera mechanism, that Bronze Age thingamajig that predicts eclipses and the motion of planets. It's a portable version of what our ancestors had laid out with stones 3000 years before. Some of those stones are in Ireland, just down the road from me.

The little that modern astronomers and archaeologists have been able to reverse engineer from Irish stone circles is so tantalizing. When you visit a stone circle, you can use your compass to see how mountain peaks and distant cairns line up with various stones, BUT WHAT DOES IT MEAN? WHY DID IT MATTER? Gaah. Ravenclaws like me demand to know!

I wrote about a stone circle, Kealkil, in that earlier post about Summer Solstice, and mentioned the radial cairn. It's a flatish circle of stones, and along the edge are 18 taller stones, standing up like teeth.

You can see an edge of it in this picture I took on solstice, but you can find many more on the web taken under sunny skies, and diagrams of the circle and its orientation to the sun, moon, and mountains.

There is a better photo of this in the Roaringwater Journal post about this circle and a few other lovely places in West Cork.

And now, in esoterica you should know: the 18th Major Arcana card in tarot is The Moon, and the 19th is The Sun.

I've been told that this is because there is an 19-year Sun cycle and an 18-year Moon cycle. The 19 years come from a 19-year cycle of inserting a 13th month into a lunar year to keep a lunar calendar in sync with a solar year and its seasons. An extra month is inserted into years 3, 6, 8, 11, 14, 17, and 19, and then the cycle repeats. The Jewish practice of inserting this extra month into their lunar calendar is why Jewish holidays don't migrate around the Gregorian calendar like Muslim holidays do. (See Metonic Cycle).

So: The 19-year cycle keeps the moon synched up with seasons, which are solar.

The 18-year cycle predicts the eclipses, where the moon appears to cover the sun (solar eclipses), or the earth's shadow covers the moon (lunar eclipses). If you observe one eclipse, then 18 years later another eclipse will occur, roughly in the same place in the sky. We don't get them every month because the moon's orbit is not on the same plane as the earth's around the sun, and there is a complicated dance through lunar maximums and minimums above the horizon that you can read about elsewhere.

So: The 18-year cycle predicts eclipses, which are lunar.

Ancient Irish people who built the circles and the stones were definitely into the business of predicting solar eclipses. There is an image of an eclipse 5000 years ago chipped into the stone at Loughcrew.
Is the 18-stone radial cairn at Kealkil an eclipse predictor? Why wouldn't it be? I guess scientists would say we don't know for sure, but total solar eclipses are so emotionally moving that predicting them has preoccupied the brainiest nerds in every civilization for at least 5000 years.

Here's part of great article reprinted from a book, in Wired, "A Total Solar Eclipse Feels Really, Really Weird."

Actually, seeing an almost total eclipse is no better than almost falling in love or almost visiting the Grand Canyon. Only full totality produces the astonishing and absolutely singular phenomenon that resembles nothing else in our lives, on our planet, or in the known universe. ...
Then a minute or two before totality, shimmering dark lines suddenly wiggle over all white surfaces, such as sand or a sheet spread on the ground. These are called shadow bands, and they can’t be photographed! If you try, your video or still images will show the white substance or object without any wavy bands at all. The rather anticlimactic reason for this is simply that shadow bands have extremely low contrast. Because they shimmer, the eye readily picks them out. But they lie below the contrast required to show up in a photographic image. ...
Then comes totality, which can last anywhere between one second and around seven minutes. Now you take off your welding goggles and look at the sun directly. The bright stars come out. The sun’s corona leaps across the sky, much farther than you expected. ...
It’s an experience that does not seem of this life or this world. “The home of my soul” is how one eclipse watcher described it to me. But why? What has really happened? It’s obviously not simply a matter of the sun’s visible light being blocked. Its invisible rays are extinguished, too. ... Solar ultra-violet energy drops to zero. So does infrared radiation, whose absence starts to be felt long before totality arrives. With the drop in infrared energy, clouds, rocks, and the air just above the ground are suddenly cooled. This chill creates a pressure difference that manifests itself as a haunting eclipse wind. Moreover, the decreasing temperature as the sun is steadily blocked can shrink the gap between the temperature and the dew point, allowing clouds to suddenly form.

Imagine the rising reputation of nerds through the ages as they predict that sort of thing decades in advance! Building a stone computer on the top of a hill is the least Kings would do for you.

On Monday, I'll be in Dublin, where we can see just a tiny bite of the sun eaten away. I won't be experiencing totality, but I will be in Ireland, and that's a long way from Fresno.

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