I’m sure you’ve heard of those who are skilled in martial arts trying to get a black belt. It is a great achievement for any martial artist and represents years of hard work, dedication and discipline.
And for some “umbraphiles” – those who have spent decades chasing total solar eclipses around the world – the upcoming April 8 solar eclipse will (in my opinion) provide a chance to earn a black belt for chasing eclipses.
Let me explain. And while you’re at it, be sure to check out my talk on the total solar eclipse below, given to the Rockland Astronomy Club on February 23, 2024.
Related: What will it be like to experience the 2024 total solar eclipse?
Eclipse Replays
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It is an interesting phenomenon that a solar eclipse, whether of the sun or of the moon, will repeat or “return” itself. But to today’s layman, the whole situation regarding predicting eclipses seems like a random pattern.
This does not apply to those who lived more than two thousand years ago!
The beginning of eclipse predictions may have been started by some unknown and long-forgotten Sumerians who recorded an account of a lunar eclipse on clay tablets as an isolated incident in the 23rd century BC. And in 747 B.C. a series of such accounts began in Babylonia, lasting several centuries.
Astronomers in Assyria and Babylonia kept time by carefully observing the movements of the moon the sun. Capturing the details of solar and lunar eclipses significantly increased the accuracy of these measurements. And as they studied the history of centuries of eclipses, a pattern began to emerge: Eclipses tend to repeat themselves at intervals of just over 18 years, although they repeat in different places on Earth. Soil.
This eclipse cycle is called the saros – Greek for ‘repetition’. It is still used to make predictions today. A Saros cycle can be defined as 18 years, 15 days and 8 hours, minus the number of bissextles (leap years) between eclipses. In most cases this is equal to 18 years, 10 days and 8 hours or 11 days and 8 hours, as five or four leap years, respectively, almost always intervene with almost equal frequency.
Consecutive eclipses belonging to a given series are similar in type, terrestrial latitude of occurrence, and duration. Because of the extra 8 hours (one-third of a day), each successive solar eclipse occurs about 120 degrees of longitude west of its predecessor.
The upcoming solar eclipse of April 8, 2024 belongs to saros number 139, to distinguish it from other saros series that have ended, are ongoing, or have yet to begin. An eclipse with an even saros number occurs when the moon crosses the Earth’s orbital plane, from north to south (called the descending node), while an eclipse with an odd saros number (such as saros 139) occurs when the moon crosses the lunar eclipse. The Earth’s orbital plane running from south to north (called the ascending node).
During the more than 18-year period of one saros, there are an average of 42 solar eclipses. So there are 41 representatives of different saros series that can come and go between the time a specific member of an eclipse “family” takes its bow and its predecessor returns for an encore a little over 18 years later.
For many it started in 1970
Many umbraphiles caught the solar eclipse while hunting for “bug” after witnessing their first-ever total solar eclipse on Saturday afternoon, March 7, 1970. On that occasion, the dark shadow of the moon, from which a total solar eclipse can be seen, moved over the Isthmus of Tehuantepec, Mexico, and into the Gulf of Mexico, then over northwestern Florida, Georgia, the Carolinas, and into the Atlantic Ocean near Norfolk, Virginia.
Afterwards, totality was observable from land on Nantucket Island, Massachusetts, and from Nova Scotia and Newfoundland. The 1970 eclipse is, so to speak, a relative of the same saros family – 139 – to which our upcoming April 8 belongs.
One Saros cycle after 1970 – 18 years, 11 days and 8 hours later – on March 18, 1988, another member of Saros family 139 appeared. Totality began in the Indian Ocean at local sunrise, when the moon’s shadow was about 900 miles west of Sumatra landed.
In just five minutes, the shadow made landfall on the western shore of South Sumatra at a speed of 8.8 km per second. The narrow sliver of totality then curved northeast, turning day into night over central Borneo, and later southern Mindanao in the Philippines. The shadow’s remaining path lay across the open waters of the northern Pacific Ocean.
After another 18 years, 11 days and 8 hours, Saros 139 returned on March 29, 2006, spreading its totality over parts of West and North Africa, Turkey and Central Asia. The moon’s dark shadow traced a trail 9,000 miles long, ranging in width from 76 to 112 miles.
Although this narrow track covered only 0.4 percent of the Earth’s total area, those lucky enough to be positioned within it saw the sun completely obscured for just over four minutes.
This brings us to the present, where another member of Saros 139 is about to reassert its presence – as was the case in 1970 – over North America in less than a week, on April 8.
The “triple saros”
Now, after three saros repetitions, which equals 54 years and 33 ± 1 days (since 13 ± 1 leap years occur respectively, with 33 days and 13 leap years being the most common), a solar eclipse repeats in the same general part of the world . We can call this a ‘triple saros’ to describe this time interval. American astronomer Owen Gingerich (1930-2023) noted that the Greeks called a period equal to three saros cycles an ‘Exeligmos’, meaning ‘the turning of the wheel’. Because after three saros cycles the shadow of the moon has indeed completely revolved around the earth.
Study the similarities between the visibility zones of the March 7, 1970 solar eclipse, compared to an Exeligmos later with the upcoming April 8 solar eclipse.
And now, to earn a black belt in eclipse hunting, I suggest you would have literally had to have traveled the world to witness three previous members of the same saros family – in this case 139 – in 1970, 1988 and 2006, before completely “turning the wheel” by experiencing the April eclipse and completing a triple saros:
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1970-1988
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1988-2006
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2006-2024
This is certainly not an easy task, because to do this you literally have to travel around the world following a specific saros series, and it will take more than 54 years to do it!
The term “black belt” is certainly appropriate when you consider that the dark shadow of the moon itself follows a black belt of darkness as it moves across the Earth’s surface.
I personally will not be in the running for a black belt this year, as I have never experienced my first total solar eclipse until July 10, 1972 in Cap-Chat, Quebec. That eclipse was a member of saros family 126. On July 21, 1990, I experienced another total solar eclipse of that same saros family during a commercial flight over the North Pacific Ocean, halfway between Honolulu and San Francisco. When Saros 126 returned on August 1, 2008, I viewed it from a chartered flight bound for a circle above the North Pole. With any luck, I hope to witness the total solar eclipse of August 12, 2026, which will pass over Greenland, Iceland and the Iberian Peninsula, which would complete my personal triple saros and earn me a black belt in eclipse hunting.
Nothing lasts forever
One final point to note is that a saros family cannot last forever. Normally, a saros series contains 70 to 85 eclipses, lasting between 1,244 and 1,514 years. Series 139, with a total of 71 eclipses (16 partial, 12 annular total or hybrid, and 43 total) began in the year 1501 and will end in the year 2763, lasting from start to finish for a total of 1,262 years.