FIVE MILLENIUM CANON OF SOLAR ECLIPSES

Updated Sunday 15 May, 2011 12:18 PM

FIVE MILLENIUM CANON OF SOLAR ECLIPSES

Book Review by Thomas Wm. Hamilton

I was delighted recently to see a new publication by a former student of mine. Fred Espenak has co-authored, with Jan Meeus, a new, and probably definitive, summary of all solar eclipses from 2000 BC to 3000 AD. It uses the most up-to-date information on the motions of the Moon, and covers partial, total, annular, and hybrid eclipses. Some of the old and new eclipses are quite interesting.

The book begins by giving a history of past attempts to cover solar eclipses, beginning with the famous "Kanon der Finsternesse" by Theodor von Oppolzer in 1887. The authors hope that the new work will be of use to astronomers, educators, planetariums, and others. I suspect the "others" will include science fiction writers, as I already plan a minor change in my time travel novel to reflect some of this information.

For each eclipse during the five thousand year period, the book gives type (partial, annular, total. or hybrid). There is a map, showing where on Earth the eclipse path tracks, both in partial phases and as either total or annular. Modern political boundaries are shown to help locate paths. The duration of the eclipse at maximum is given along with the Sun's elevation above the horizon, and which saros cycle the eclipse belongs to.

In the five thousand year period Earth experiences 11,898 solar eclipses, of which 4200 are partial (35.3%), 3956 annular (34.1%), 3173 total (26.6%), and just 589 hybrid (4%). I didn't count all those entries, the book provides the numbers.

I checked out the total eclipses I have seen, including two from the same saros (1963 and 1980), as well as a couple I saw as partial. Then I started looking up some historic eclipses. Or not so historic, because the first thing I looked for was solar eclipses in England in the Sixth Century. Those who have read Mark Twain's "Connecticut Yankee in King Arthur's Court" will remember that the Yankee avoids execution as a witch by making the downtimers think he was causing a solar eclipse he just happened to remember was due.

We do not have a good historical date for King Arthur, and a few skeptics suspect he may be just a legend, but assuming he lived, it was in the Sixth Century, probably the middle third. I checked for solar eclipses visible from England between 525 and 575 AD. There were 129 solar eclipses of all types during those fifty years, most of course only partial. The most common of the others were the 42 annular eclipses, followed by 32 total, and just four that were hybrid.

The partial eclipses I ignored, since they usually are not even noticed unless people are told of them. This left the hybrids, totals, and annular eclipses. I quickly disposed of the handful of hybrids. The first one, on September 22, 526, barely touched England as the start of a partial at sunrise. The others came nowhere near the British Isles.

The totals of course mostly missed England also. The closest seems to have been one in June of 540 whose path of totality passed just north of Scotland. And an annular a few years later passed to the south, over Gibralter and the mouth of the Mediterranean.

So Mark Twain was faking it even bigger than his Yankee did, and King Arthur, if he lived, never got to see a solar eclipse. It's still a great story.

Twain may have gotten the idea from Columbus, who used a real lunar eclipse to intimidate some Indians on his second voyage in 1494. Lunar eclipses are not covered in this book, but they are often separated by two weeks from a solar eclipse. I checked, and sure enough, there was a partial solar eclipse on August 30, 1494. It was visible from New Zealand and a small portion of Anarctica.

How about the assassination of Julius Caesar? As Shakespeare wrote, "No man attends the death of beggars, the heavens themselves blaze forth the death of kings." Caesar's March 15, 44 BC death was attended by a comet, but the nearest solar eclipse was an annular on April 18. It was not seen in Rome, just in what would someday become Brazil, Argentina, and Chile.

As further evidence that solar eclipses are really not associated with historic events, there was an annular eclipse seen off the coast of Antarctica on March 28, 1066, and another across northern Asia on September 22, neatly bracketing the Battle of Hastings in both time and space. And the final proof eclipses are not related to disasters, the closest one to my birth was a partial 51 days before, and just barely made the West Coast at sunset. Sufficient I would hope to disprove the ancient fear of impending doom from eclipses.

Three solar eclipses crossed what was becoming the United States during the Revolution. An annular on July 5, 1777 actually touched no part that was involved in the Revolution, cutting through then-Spanish owned southern Louisiana, and Florida, then British owned but not in the war. However, the total eclipse of June 24, 1778 gave well over five minutes of totality as it crossed Georgia, the Carolinas, and a bit of Virginia. The eclipse of October 27, 1780 gave Maine (then a part of Massachusetts) only two minutes of totality, in a path somewhat like that of 1973.

Among the quirks to be found, starting on Nov. 29, 298 BC and continuing through May 3, 295 BC there are six eclipses, which are total, annular, hybrid, hybrid, annular, and total. Six eclipses, including two of the rarest, none of the most common type. Regrettably, the two totals in that sequence only touched land in Antarctica, unknown to the human race then and for another 2000 years, and New Zealand, which probably was also still uninhabited at that time.

One could spend hours playing with this book to find other oddities, or to compile statistics on what percentage of eclipse paths totally miss land, or fall only in the polar regions. This year we have just two partials, in eastern Asia on March 19 and in southern South America and the Palmer Peninsula of Antarctica on September 11. Next year has an annular in Antarctica on February 7, and a total eclipse of 2 minutes 27 seconds duration crossing Greenland through Russia into China. 2009 and 2010 each has two eclipses that are each one annular and one total, but 2011 has four, all partials. Make your travel plans early.

The inevitable question is how many lunar eclipses are there? In the same 5000 year period there are 12,186 lunar eclipses, 4468 (36.7%) penumbral, 4213 (34.6%) partial, and 3505 (28.8%) total. This comes from Espenak's catalog on the NASA website.

This book is available from NASA Center for Aerospace Information, 7121 Standard Drive, Hanover, MD 21076, (301) 621-0390, report number TP-2006-214141. The link to the NASA website is: http://sunearth.gsfc.nasa.gov/eclipse/LEcat/LEcatalog.html It can be downloaded in full or in blocks of centuries (i.e. 2001-2100, which BTW has 230 lunar eclipses, 85 of them total). I do not know the price.

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