Index of Topics on the "Calendars and Eclipses" page





More Information on "Why No Solar Eclipse Predictions?"


The following table compiled from the "Canon of Eclipses" between 1207 BC to AD 1600 shows a series of total solar eclipses visible over Egypt covering more than 1000 years. The right column gives the number of months between the current eclipse and the next one in the series.

August 1157 BC  
May 1124 BC 394
March 1084 BC 292
July 1063 BC 377
May 998 BC 71
May 957 BC 109
January 932 BC 297
June 911 BC 259
November 901 BC 126
August 831 BC 838
April 824 BC 81
March 702 BC 264
July 691 BC 137
September 646 BC 543
August 637 BC 108
August 636 BC 13
May 603 BC 394
September 582 BC 257
November 556 BC 315
June 531 BC 296
March 517 BC 166
August 502 BC 186
November 493 BC 112
February 357 BC 424
April 303 BC 651
September 256 BC 570
February 217 BC 462
June 176 BC 497
April 136 BC 479
April 127 BC 109
August 116 BC 137

Note that there is no discernable pattern or simple formula for knowing when an eclipse happened during a particular month and year, or to predict when the next total solar eclipse would happen in the same geographical location. In adition, bad weather further reduced the number of observable eclipses. Lunar eclipses follow after periods of 135 and 223 months. Plotting the distribution of months in the above table shows two peaks near 120 months and 270 months, but only half the total solar eclipses cluster near these two intervals. Astronomers using the 135-month or 223- month lunar eclipse periods to forecast total solar eclipses would be wrong at least half the time. Odds are similar to tossing a coin to predict whether an eclipse would occur this month.

Only after the lunar orbit was determined, and the changing orbital speeds of the Moon and Earth were established, could total solar eclipses be forecast to within the nearest month or less. This level of sophistication in astronomy was reached by Greek astronomers around the first century BC followed by Chinese astronomers centuries later. We can only speculate on the extent of knowledge lost in the fires of the Great Library at Alexandria, or in destruction by Spanish Conquistadores and missionaries in Mexico, Peru, and Chile.


For Further Readings

A History of Science, William Dampier, 1948, Cambridge University Press, Cambridge.

A Chronicle of Pre-Telescopic Astronomy, Barry Hetherington, 1996.

Ancient Astronomical Observations and the Accelerations of the Earth and Moon, Robert R. Newton, 1970, The Johns Hopkins Press (Baltimore, Maryland).

Canon of Eclipses, Theodor von Oppolzer and Owen Gingerich, Dover Publications, New York.

A Vienna Demotic Papyrus on Eclipse and Lunar Omina, Richard Parker, 1959, Brown University Press, Providence, RI.

Early Astronomy, Hugh Thurston, Springer-Verlag Publishing.

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