aa r X i v : . [ phy s i c s . pop - ph ] J a n F IRST VERSION PUBLISHED IN : Sternzeit 40 , No. 1 / 2015, p34–36 (ISSN: 0721-8168) arXiv: (side label) [physics:pop-ph]
Date: 21st January 2021
On the Erroneous Correlation between Earthquakes and Eclipses
Emil Khalisi
D–69126 Heidelberg, Germanye-mail: ekhalisi[at]khalisi[dot]com
Abstract.
A long-lasting belief is that the gravitational stress by the moon would be responsible for earth-quakes because of causing a tidal deformation of Earth’s crust. Even worse, earthquakes are sometimes saidto be correlated with eclipses. We review the origin of this wrong statement and show that the idea is owedto a fallacious perception of coincidence. In ancient times the two catastrophes were linked interpreting theannouncement of Doomsday, while in modern times a quasi-scientific essay disseminated such an interrelationshortly before the theory of tectonics.
Keywords:
Eclipses, Earthquakes, Tides, Tectonics, Moon.
Eclipses of the sun and moon come about as an interplay oflight and shadow. Nevertheless, one stumbles upon someneo-scientific views in books and internet that there wouldexist a relation between this optical phenomenon and earth-quakes. The argument is based on the position of the moonin space: at the syzygy, which is the only time for an eclipseto occur, the tidal forces on the earth’s crust are strongest,and, therefore, tensions discharge in a quake. Our attemptis to trace down the origin of this idea. We briefly clarifythe geophysical effects accountable for earthquakes at nextsection, then we elucidate the historical roots of the state-ment that eclipses and quakes would happen concurrently.Finally, we give an explanation why this non-existent rela-tion is still believed in.
The earth is considered a rigid body, but it is also exposedto drag forces that make it deform like a plastic body. Thephysical deformation is caused by both sun and moon exert-ing a stronger force on the facing side than on the avertedside. In principle, the tensions on the thin crust could trig-ger an earthquake. However, one should distinguish twoprocesses: tectonics and tides.Tectonic activity is the primary impetus for land- andseaquakes. The continental shelves float on the viscous up-per mantle and are driven by subjacent convection streams.They change their position on timescales of millions ofyears. The plates collide and get stuck, while moving pasteach other, and they are subject to a bent, compression,and stretching. At the contact boundaries tensions buildup. Once the local tensions get too high, they discharge ina sudden rupture releasing large amounts of energy. Thebasics of this theory were elaborated in the late 19th centuryand promoted by Alfred Wegener in 1912 [16].A completely different effect is the tidal force from ce- lestial objects. The moon generates gravitational tides onthe earth’s surface creating two tidal bulges. It pulls theterrestrial water masses from the fringes to its facing side,while on the far side the centrifugal force due to Earth’s ro-tation becomes preponderant. The range of the tidal upliftis between 50 to 100 cm for the open ocean. The effectapplies to the crust as well. For example, Central Europeelevates and sinks by some 45 to 50 cm [10].The sun exerts principally the same force on the earth,but its share is smaller, amounting for ≈
40% of the totalforce. At new or full moon, the forces of the sun and moonreinforce each other, and the deformation unfolds strongerthan at the quadratures. Actually, the earth is in a state ofconstant seismic tremor, but we take only cognisance of themore violent incidents. Small distortions could eventuallyinduce a crack, and the subsequent wave lets the continentalplate carry out a re-adjustment: the earth endures a quake.One might think that the phase of the moon has an effecton that, which would also be reflected in the occasion ofeclipses.
The first one to mention the coincidence of an eclipse withan earthquake was the Greek historian Thucydides in the4th century BCE. He was primarily concerned with the Pelo-ponnesian War between Athens and Sparta, but he incident-ally told that there were ten days between the solar eclipseof 21 March 424 BCE, that was seen partial in Athens (mag= 0.705), and an earthquake. It is not quite clear whetherthe historian wished to insinuate a connection between thetwo phenomena [1].The naturalist Aristotle discussed in his book
Meteoro-logica the reasons for earthquakes a century later. He re-futed three hypotheses of forerunners circulating at his timeand alluded to a lunar eclipse stating that both phenomenawould coincide sometimes [11]. His own concept rested onwinds produced by “exhalations” in the earth’s interior. The1 . Khalisi (2020): On the Erroneous Correlation between Earthquakes and Eclipses
Figure 1: The total solar eclipse of 29 CE was accompaniedby an earthquake in temporal proximity [4]. explanation reads somewhat muddled incorporating “miss-ing heat drift” from the moon during the time of the eclipse.From our present-day view Aristotle’s idea is wrong, either.The next scholar was Phlegon of Tralleis, a chronicler ofthe early 2nd century CE living in Asia Minor. He coveredvarious aspects of the Roman history in his book
Olympi-ades that closes with 137 CE. There, he took up an issueamong the early Christians. Phlegon wrote [6]:In the fourth year of the 202nd Olympiad (32–33 CE) an eclipse of the Sun took place greaterthan any previously known, and night came onat the sixth hour of the day, so that stars ac-tually appeared in the sky; and a great earth-quake took place in Bithynia and overthrew thegreater part of Nicaea.Because of a scribal error the message must read: first year of that Olympiad. The eclipse refers to 24 November29 CE, and it was widely seen in the Near East (Figure 1).His link to the earthquake emerges pivotal, as it slipped intothe biblical account of Crucifixion. In fact, there was no ec-lipse on the day of Crucifixion visible from Palestine, evenless an eclipse of the sun.A widespread 6.3 magnitude earthquake has been con-firmed to have taken place on the western shore of the DeadSea in Palestine at any time between 26–36 CE, as varvedsediments indicate [17]. The magnitude was probably suffi-cient energetic to cause local deformations in the sedimentlayers but not energetic enough to enter a widespread histor-ical record. This event does not need to be the same as inBithynia off the coast of the Black Sea reported by Phlegon.Both the eclipse and the earthquake were “borrowed” by the authors of that biblical chapter making the two phenomenaa type of allegory to enhance the fate send out by God. Afterhaving entered the Bible, eclipses and quakes coalesced andwere consolidated as portents. Similar accounts refer to theyears 968 and 1133 CE [12].Apart from the Euro-Asian peoples, a completely dif-ferent culture has also drawn a connection between earth-quakes and eclipses: the Aztecs. They exhibited great fearfrom tremors from below. There is the legend of “Five Suns”which is conveyed in a dozen sources and probably depic-ted on the famous calendar stone. It is interpreted as thecreation myth of various peoples of central Mexico beforethe Conquest. The tenet comprises that there have beenfour worlds (or “suns” or “eras”) before our present sun.The previous ones were destroyed by actions of deity fig-ures: a knock-out, hurricane, fire, and an immense flood[14]. Living under the fifth sun now, it will also perish someday. This destruction will be brought about by earthquakes.The Aztecs were convinced that the sun is under perman-ent threat and condemned to a cosmic catastrophe. Human-kind could put off this evil day by keeping it supplied withsacrifices. Thus, an extinguishing sun, like in the case ofan ongoing eclipse, was always feared as the end of theworld. We gleaned in our study of eclipses a good numberof years in the Aztec chronicles harbouring both an eclipseand earthquake [13]. Unfortunately, it is difficult to extracthow the two effects are enmeshed in the mind-set of the nat-ives, because many original documents were destroyed bythe Conquistadores. Notwithstanding such myths, it mightturn out that the geographical location in Central Americais predestined to fear earthquakes, while the sudden loss ofdaylight has always been a reason for panic in every cultureworldwide.Finally, some sort of “scientific” basis was laid in the19th century by a populariser of natural history, Rudolf Falb(1838–1903). He developed a concept of extraterrestrial in-fluences on geophysical phenomena mingling floods, earth-quakes, meteorology, and astronomy. In a once success-ful family magazine he enumerated some examples of syn-chronised occurrences [5]. There he linked up with a thesisof a seismologist, Alexis Perrey (1807–1882), who pion-eered this field of geophysical research. The latter suspec-ted a correlation between earthquakes and the position ofthe moon. At that time the theory of continental tectonicswas not born still. In absence of knowledge of a potentialterrestrial origin, it was only natural to look for a cause inthe tidal stresses from outside. Falb, however, expandedPerrey’s views into the idea of predicting earthquakes bythe aid of eclipses. The academic community vehementlyrejected such assignments straight away. Nevertheless, Falbattained considerable popularity through apparently correct“predictions” of some few events.
One of the first who criticised the catenation of the two phe-nomena was the astronomer Friedrich Karl Ginzel (1850–1926). He analysed the seismological data from Califor-2 . Khalisi (2020): On the Erroneous Correlation between Earthquakes and Eclipses
Figure 2: Strength of earthquakes for the years 1990 till 2005 versus the angle Sun–Earth–Moon (lunation phase) [2]. nia, one of the most active regions on Earth [7]. He foundthat there were 153 eclipses (solar and lunar) between 1850and 1888, and examined the positions of the moon withregard to perigee, apogee, and the lateral distance to theEarth’s equator, i.e. its declination. (Remember that thecycle of perigee/apogee, the anomalistic month, is not re-lated to lunar phases.) Ginzel arrived at the conclusion thatall tremors were statistically at random. They did not showany relation to the position of the moon, not even at thesyzygies. But the most serious critique concerned the man-ner how Falb obtained his result: he only quoted examplessupporting his theory without paying attention to the totalquantity.Even today many studies reveal unsteady despite tech-nological advances. An unnamed survey, appearing cred-ible though, is presented in Figure 2. It is based on a collec-tion of earthquakes with magnitudes > ◦ (vertical line) or180 ◦ , when the forces of the sun and moon sum up. But thedata do not exhibit that. They show even the contrary: therewas a quake here and there, but the quantity of events turnedout less than at other lunar phases. When including weakerevents, the distribution becomes even more arbitrary.Two recent studies yield contradicting results. SatoshiIde etal. state that for more than 10,000 earthquakes at ap-proximate magnitude 5.5 the incident began during the timeof high tidal stress and was more likely to grow to mag-nitude 8 or higher [9]. The authors refer to Sumatra in 2004,Chile in 2010, and Japan in 2011. On the other side, SusanHough looked at both the date of the year and the lunar phase for 204 large earthquakes [8]. To avoid “clusters” ofincidents within the data that might be aftershocks of a pre-vious one, she chose to compare the dates as far back as1600 CE. Her analysis did unveil some clustering, but onrandomising the data there was no statistical significance:no correlation between earthquakes and tides.The literature on this issue seems non-exhaustive. Anoverview of studies until the 1990s was undertaken by Die-ter Emter [3]. He found almost a direct split between re-searchers who find such a connection, and those who donot. Sometimes the outcome depends on the method of in-vestigation. Applying statistics to the datasets can actuallycause all sorts of headaches that have more to do with math-ematical treatment than science.Many re-analyses prove not representative, again. Sur-prisingly, a multitude of published diagrams on the inter-net come from astrologers and doom prognosticators. Dayswithout a quake are actually very rare. It is estimated thataround 500,000 earthquakes with a magnitude larger than2.0 occur each year, detectable with current instrumentation[15]. About 100,000 of these are strong enough to be felt,and 100 cause damage. So, someone could choose almostany calendric date and his “prophecy” will be right.Predictions of earthquakes are still not possible today.In particular, a reproducible prediction cannot be made fora specific day or month. All attempts are no more than arandom guess. Researchers can only give a probability foran interval of time.The gravitational attraction of the moon is rather smallon terrestrial rocks, and the correlation between earth-quakes and tides remains unproven. Such arguments willhold for the Galilean satellites of Jupiter and Enceladusof Saturn, but not for the Earth. Aside from tides, the hy-3 . Khalisi (2020): On the Erroneous Correlation between Earthquakes and Eclipses pothesis about a correlation of eclipses and earthquakespersists to this day. If the position of our moon should everturn out significant, then the connection with an eclipsewould be irrelevant, meaning: the earthquake will happenwithout the obscuration of celestial bodies. We tried to reproduce the statement of an interrelationbetween earthquakes and eclipses. We believe that the an-swer goes back to rather quasi-religious illusions than tohard facts.In old times, eclipses were considered as dreadfulevents. When the most important luminary in the skysuddenly failed to shine, dramatic turmoils were going onand a whole society became upset [12]. The scene of un-expected darkness remained in memory for many years.An earthquake, however, costs many people their lives anddestroyed entire villages. If both calamities were to takeplace in temporal proximity, the tragedy was associatedwith a “punishment announced by the gods”. The fate fromcelestial prophecies became manifested hereinafter. Forastrologers this was a welcome sign of validation of theirdoctrine. They cling more than ever to the putative connec-tion. The scribes would transmit that with some decorationto raise the effect or to make their account more important.Thus, many reports on the proximity of both disasterspile up because of psychological selection effects than real-ity. Sooner or later there will be another earthquake close toan eclipse, and the self-proclaimed prophets will have theirjoy.
Acknowledgements
This paper is an excerpt from the Habilitation submitted tothe University of Heidelberg, Germany, in February 2020.A blueprint was published in the German magazine for as-tronomy
Sternzeit previously. The author dispenses withpeer reviews for this re-publication. The entire work wasaccomplished under disgusting circumstances on account ofjudicial fraud. That abuse of power by officials is a nationalshame.
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