The knowledge of the shadow of the Earth


* El conocimiento de la sombra de la Tierra

"I will produce portents both in the sky and on the earth – blood, fire, and columns of smoke."

"The sunlight will be turned to darkness and the moon to the color of blood, before the day of the LORD [Yahweh] comes – that great and terrible day!"

This is from the book of the Hebrew prophet Joel, Chapter 2, verses 30 and 31 (NET [New English Translation] Bible, Biblical Studies Press, Richardson, Texas, 2005). It was written at some time between 800 B.C.E. and 350 B.C.E., and it clearly shows what in the minds of the ancients it was thought of the origin or cause of eclipses.

And in other cultures it was similar: "The eclipse of the Moon which took place in Marchesvan (month VIII) began [in the east]. That is bad for Subartu. What [is wrong]? (...) What is being done to (make) its evil pass? . . ." cried the scribe Bel-sum-iskun of Babylon in 675 B.C.E. (quoted by F. Richard Stephenson, "Historical Eclipses and the Earth's rotation", Cambridge University Press, London, 1997, page 125).

But in the "Book of Odes" of the eighth-century B.C.E. China some regularity on the phenomenon was already intuited: "Then the Moon became small (...) For the Moon to be eclipsed is but an ordinary matter." (Quoted by Stephenson, in the same book, page 222).

At that time the Babylonians already had records of centuries of astronomical observations, written on clay tablets, with the positions of the Sun, Moon and planets at different points in time. With this database they realized that if there is an eclipse today, there will be another similar eclipse within 223 full moons. This cycle was then known as the Saros cycle, and was the first system used to predict eclipses with more or less accuracy.

There are basically two types of visible lunar eclipses: the partial eclipse and the total eclipse. One of the characteristics that distinguishes a partial eclipse from a total eclipse is that in the latter the Moon acquires a reddish color, which to the ancients looked like blood. This hue is due to optical effects on the solar light passong through "the ring of air" of our planet's atmosphere, as seen from the Moon.


About the year 450 B.C.E. a Greek named Anaxagoras was sent to prison for not practicing religion and for teaching theories about the "things above." He said that the sun was not a god and that the moon was made of common earths, and it simply reflected the sunlight. Most of his writings have been lost unfortunately, but Hippolytus of Rome (ca. 170 - ca. 236 ), in his "The refutation of all heresies" (reprinted in "Ante-Nicene Fathers", Volume 5, Book 1, chapter 5, edited by Alexander Roberts and James Donaldson, revised and arranged chronologically by Cleveland Coxe, T & T Clark, Edinburgh, 1885), brings us one important fact about him: "This person affirmed (...) that the moon is eclipsed when the earth is interposed (...) This person was the first to frame definitions regarding eclipses and illuminations."

But this knowledge was hardly seeping out of scientific circles. Thus Plutarch tells us of the stumbling of Nicias (ca. 470 - 413 B.C.E.), an Athenian general who was besieging Syracuse and was preparing for the final assault. But on that night there was a lunar eclipse. Nicias was flooded with a superstitious terror and immediately abandoned his plans. This gave the enemy time to counterattack and Nicias ended prisoner.

But Alexander the Great, possibly the most successful general in Hstory, was to be smarter. On 20 September of the year 331 B.C.E., while preparing for the Battle of Arbela, a lunar eclipse occurred. Historian Quintus Curtius Rufus ("De la vida y las acciones de Alexandro, el Grande" ["Of the life and actions of Alexander the Great"], translated from the Latin language into Spanish by Don Mateo Ibañez de Segovia y Orellana, Marquis of Corpa, Knight of the Order of Calatraba. With license. In Madrid: in the press of Ramon Ruiz. Year M. DCC. XCIV. [1794], Book Quarto [Fourth], Chapter X) relates that "caused in the Army such a religious commotion that unforeseen incident (coming about in occasion of being such a bloody battle just to begin, and whose success had everybody in quite a care) than passing into unrestrained terror, bursted forth the soldiers, worried about it, in voices high and disconsolate." Alexander quickly summoned his generals and ordered his Egyptian soothsayers give their views. These wisepersons already knew the real cause of eclipses: that the cyclical movement of the Moon led it to be right behind the Earth. But it was decided not to explain this to the common soldiers: instead, they said "That the Greeks were denoted by the Sun and the Persians by the Moon; and that no eclipse of this ever failed to be to [these enemies] unlucky omen of some calamity. (...) With such, not being there more effective means to curb popular barbarianism, which as unrestrained and inconstant as it were, if it was to be touched of some useless shadow of religion, better obey the Diviners, than their Generals."

The Roman tribune, later consul, Sulpicius Gallus had a slightly more democratic behavior in a similar circumstance. Literary aficionado man, he was aware that there was an eclipse forecast for the night of 21 June 168 B.C.E.. Historian Titus Livius tells us ("History of Rome", volume 6, book 44, section 37, Ernest Rhys, editor, Rev. Canon Roberts, translator, J. M. Dent & Sons, London, 1905) that in the previous day Sulpicius Gallus addressed the troops of his fellow countryman Lucius Paulus, saying to them that "they ought not to take its obscuration [of the Moon] when it is hidden in the shadow of the earth for a supernatural portent" because just as they did not fear the cycle of day and night and the moon phases, they should not fear the eclipses, "because this happened in the natural order of things at stated intervals." The enemy's soothsayers, instead, could not give an explanation about the phenomenon other than the downfall of their kingdom: "Shouts and howls went on in the Macedonian camp". Lucius Paulus won the battle and with that the Third Macedonian War came to an end.


But superstition was slower in leaving off heavily theocratic cultures. Incidentally, Jewish historian Titus Flavius Josephus gives us the death date of the cruel Herod the Great, saying it was between one of his famous massacres, in which night there was a lunar eclipse, and the Week of Passover. With other information given by Josephus and modern Astronomy it is estimated that the king may have died after the eclipse of 15 September of 5 B.C.E. and near the start of the Week of Passover, begun on 12 April of 4 B.C.E., Julian Calendar dates (Titus Flavius Josephus, "Antiquities of the Jews", Book 17, Chapter 6, paragraph 4, through Chapter 9, paragraph 3). With these data and choosing the Gospel according to Matthew (2:1-16) instead of the Gospel according to Luke (1:1-7), one can speculate that Jesus of Nazareth was born before the latter date.

In Acts, chapter 2, Simon Peter continues associating the fear of God with eclipses, insisting that Joel's prophecy was fulfilled with the possible help of an eclipse near the supposed "descent of the Holy Spirit on the Apostles" on the Jewish feast of Pentecost, 50 days after the finding of the emty tomb of Jesus of Nazareth. Estrapolating from the Gospels (Luke 3:1-2 and Luke 3:23), from the regime of emperor Tiberius Caesar and data from Josephus ("Antiquities of the Jews", Book 18, Chapter 2, paragraph 2; Chapter 4, paragraphs 2 and 3; and Chapter 6, paragraph 5), Jesus of Nazareth began his public preaching no earlier than 28 C.E. and he was killed at the latest in 36 C.E.. Modern calculations show that in this period of 8 years there were 7 lunar total eclipses, with only 2 of them fully visible from Jerusalem: one in 14 June 29 C.E. and the other in 27 July 36 C.E., Julian Calendar dates. The latter date was too late in the year, well after Pentecost. So the change of "the moon to blood" mentioned was probably the one witnessed over Jerusalem in the night of 14 June 29 C.E..

In Simon Peter's days the Greeks already had complex mathematical formulas to predict even the hour of eclipses, mainly thanks to the observations of the movements of the Moon and of its distance made by the greatest astronomer of Antiquity, Hipparchus. Yet even in the Middle Ages it was still possible to see in Western literature phrases like "Her wæs se mona swelce he wære mid blode begoten" in 734, and "eall blodig" in 1117, as can be read in "The Anglo-Saxon Chronicle". (The first sentence in the manuscripts "A" [Cambridge], "B" [London], "C" [London], "D" [London] and "E" [Oxford], at least, and the second in the manuscript "E" [Oxford], transcription and review by Tony Jebson,


In the Modern Age, the brilliant yet authoritarian Christopher Columbus decided once again to apply that thing of "knowledge is power". In 1504, he and his crew of over 50 Spaniards were isolated in the small bay of Santa Gloria (now Saint Ann), in Jamaica, for quite a long time by then. The situation worsened in February, when the natives refused to continue supplying food to the foreigners.

David Thomas, in his book "Christopher Columbus: Master of the Atlantic" (Andre Deutsch Ltd., London, 1991, p. 194) relates that Columbus summoned all local chieftains. He warned them that his god would punish them with hunger and disease if they did not help the Spaniards. And as proof of his intentions he would make a sign in heaven: a darkening of the Moon.

Some chieftains feared and others scoffed, but soon a dark shadow began to pass over the face of the Moon. Great fear seized the Indians. They implored Columbus to intercede with his god. The European retired to his cabin for about one hour, and then went back to the chiefs. He explained that the Spaniards were Christians, that they believed in a god who lived in heaven and rewarded the good and punished the bad. He informed them that the god was ready to withdraw his threat of punishment if they behaved well and provided food and other necessities to the Christians again, and that as a sign that he was willing to forgive the Indians, he would remove the shadow from over the Moon.

Of course, the trick was that Columbus had in his ship "Capitana" a copy of Johann Müller's calendar, published in Nuremberg back in 1474. It contained predictions of lunar eclipses for many years ahead. Columbus noticed that there was a prediction for 29 February 1504, precisely at the time of the dispute he wanted to settle.

The Indians, in their ignorance, accepted "the terms of the Christian god," and when the shadow was gone they marveled. From then on, the Spaniards always obtained whatever they wanted from these Indians.


As we read, the Babylonians perceived that there is a rare interval of 18 years and 11 days when eclipses usually occur. For example, the lunar eclipse seen on the date 2018 JUL 27 occurred 18 years and 11 days after that of the date 2000 JUL 16. The one occurred on 2019 JAN 21, was 18 years and 11 days after the one of 2001 JAN 9. The most recent one was on 2021 MAY 26, and once again, reviewing historical records, we see that it was also at 18 years and 11-odd days of another eclipse from the past, in this case the lunar eclipse of 2003 MAY 16:

1996 SEP 27

1997 MAR 24

1997 SEP 16

2000 JAN 21

2000 JUL 16

2001 JAN 9 ←

2003 MAY 16 ←

2003 NOV 9 ←

2004 MAY 4

2004 OCT 28

2007 MAR 3

2007 AUG 28

2008 FEB 21

2010 DEC 21

2011 JUN 15

2011 DEC 10

2014 APR 15

2014 OCT 8

2015 APR 4

2015 SEP 28

2018 JAN 31

2018 JUL 27 ← this eclipse occurred at 18 years and 11-odd days after one from the past.

2019 JAN 21 ← this eclipse occurred at 18 years and 11-odd days after one from the past.

2021 MAY 26 ← this eclipse occurred at 18 years and 11-odd days after one from the past.

Continuing our analysis of records at the top of this table, we see that there was a lunar eclipse on date 2004 MAY 4. With this data we can try to predict the next eclipse:

2004 + 18 years = 2022

MAY 4 + 11-odd days = MAY 15 / MAY 16, the evening or the early morning which contains the full moon.

Data from NASA shows the Moon in total eclipse at 04:12:42 hours on 16 May 2022, Universal Time. Genial!

And with this "magic", we adjourn. I wish you all clear skies.

Aldo Loup.

If you want to share this article with others, you may establish an Internet link, but you cannot copy any part of this page. Copyright 2007-2020. Reproduction prohibited. All rights reserved. Eclipse predictions by Fred Espenak, NASA's Goddard Space Flight Center.

Originally published in ABC Color, on 4 March 2007. Illustration: "The moon eclipse of Christopher Columbus." Credit: Camille Flammarion, "Astronomie Populaire", Charles Marpon & Ernest Flammarion, Editors, Paris, 1879-1880, Book II: "The Moon", Chapter IX: "Eclipses", p. 231, Fig. 86.