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82-410: Scholarly interest in earthquakes can be traced back to antiquity. Early speculations on the natural causes of earthquakes were included in the writings of Thales of Miletus ( c.  585 BCE ), Anaximenes of Miletus ( c.  550 BCE ), Aristotle ( c.  340 BCE ), and Zhang Heng (132 CE). In 132 CE, Zhang Heng of China's Han dynasty designed the first known seismoscope . In

164-560: A "fighting together", with the Lydians. This has sometimes been interpreted as an alliance. Croesus was defeated before the city of Sardis by Cyrus the Great , who subsequently spared Miletus because it had taken no action. Cyrus was so impressed by Croesus’ wisdom and his connection with the sages that he spared him and took his advice on various matters. The Ionian cities should be demoi, or "districts". He counselled them to establish

246-469: A Greek. Diogenes continues, by delivering more conflicting reports: one that Thales married and either fathered a son (Cybisthus or Cybisthon) or adopted his nephew of the same name; the second that he never married, telling his mother as a young man that it was too early to marry, and as an older man that it was too late. Plutarch had earlier told this version: Solon visited Thales and asked him why he remained single; Thales answered that he did not like

328-531: A fellow of St John's College in 1914, retaining his fellowship until his death 75 years later. At the University of Cambridge he taught mathematics, then geophysics and finally became the Plumian Professor of Astronomy . In 1940, he married fellow mathematician and physicist, Bertha Swirles (1903–1999), and together they wrote Methods of Mathematical Physics . One of his major contributions

410-527: A mantle of silicates, surrounding a core of iron. In 1906 Richard Dixon Oldham identified the separate arrival of P waves , S-waves and surface waves on seismograms and found the first clear evidence that the Earth has a central core. In 1909, Andrija Mohorovičić , one of the founders of modern seismology, discovered and defined the Mohorovičić discontinuity . Usually referred to as the "Moho discontinuity" or

492-452: A particular location within a particular time-span, and they are routinely used in earthquake engineering . Public controversy over earthquake prediction erupted after Italian authorities indicted six seismologists and one government official for manslaughter in connection with a magnitude 6.3 earthquake in L'Aquila, Italy on April 5, 2009 . A report in Nature stated that the indictment

574-600: A single seat of government, and pointed out Teos as the fittest place for it; "for that," he said, "was the centre of Ionia . Their other cities might still continue to enjoy their own laws, just as if they were independent states." Miletus, however, received favorable terms from Cyrus. The others remained in an Ionian League of twelve cities (excluding Miletus), and were subjugated by the Persians. Early Greeks, and other civilizations before them, often invoked idiosyncratic explanations of natural phenomena with reference to

656-517: A special meeting in L'Aquila the week before the earthquake occurred, scientists and officials were more interested in pacifying the population than providing adequate information about earthquake risk and preparedness. In locations where a historical record exists it may be used to estimate the timing, location and magnitude of future seismic events. There are several interpretative factors to consider. The epicentres or foci and magnitudes of historical earthquakes are subject to interpretation meaning it

738-562: A very short time frame in a seismic cycle . Engineering seismology is the study and application of seismology for engineering purposes. It generally applied to the branch of seismology that deals with the assessment of the seismic hazard of a site or region for the purposes of earthquake engineering. It is, therefore, a link between earth science and civil engineering . There are two principal components of engineering seismology. Firstly, studying earthquake history (e.g. historical and instrumental catalogs of seismicity) and tectonics to assess

820-493: Is about an angle intercepted by two parallel lines, forming a pair of similar triangles . Modern scholars are skeptical that anyone in Thales's time was producing mathematical proofs to the standard of later Greek mathematics, though not enough direct evidence remains to draw firm conclusions. While Thales may have discovered some basic geometric relations and provided some justification for them, attribution to him of formal proofs

902-412: Is also possible that he was of mixed ancestry, given his father had a Carian name and his mother had a Greek name. Diogenes Laërtius seems to also reference an alternative account: "Most writers, however, represent him as a genuine Milesian and of a distinguished family". Encyclopedia Britannica (1952) concluded that Thales was most likely a native Milesian of noble birth and that he was certainly

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984-601: Is believed the Babylonians knew the theorem for special cases. The theorem is mentioned and proved as part of the 31st proposition in the third book of Euclid 's Elements . Dante's Paradiso refers to Thales's theorem in the course of a speech. The story is told in Diogenes Laërtius , Pliny the Elder , and Plutarch , sourced from Hieronymus of Rhodes , that when Thales visited Egypt , he measured

1066-454: Is both "applied to those whose boasts exceed what they are" and "a warning to pay no attention to the opinion of the multitude." Diogenes Laërtius relates several stories of an expensive, gold tripod or bowl that is to go to the most wise . In one version (that Laërtius credits to Callimachus in his Iambics ) Bathycles of Arcadia states in his will that an expensive bowl " 'should be given to him who had done most good by his wisdom.' So it

1148-437: Is considered possible that Thales visited Egypt, since Miletus had a permanent colony there (namely Naucratis ). It is also said Thales had close contacts with the priests of Thebes who instructed him, or even that he instructed them in geometry. It is also possible Thales knew about Egypt from accounts of others, without actually visiting it. Aside from Egypt, the other mathematically advanced, ancient civilization before

1230-472: Is controversial." Others historians, such as D. R. Dicks, take issue with the idea of Babylonian influence on Greek mathematics. For until around the time of Hipparchus (c. 190–120 BC) their sexagesimal system was unknown. Herodotus wrote the Greeks learnt the gnomon from the Babylonians. Thales's follower Anaximander is credited with introducing the gnomon to the Greeks. Herodotus also wrote that

1312-400: Is his own thinking, his statement that Thales held it as water is generally accepted as genuinely originating with Thales. Writing centuries later, Diogenes Laërtius also states that Thales taught "Water constituted ( ὑπεστήσατο , 'stood under') the principle of all things." According to Aristotle: That from which is everything that exists and from which it first becomes and into which it

1394-703: Is now thought to represent speculative rationalization and reconstruction by later authors, rather than concrete accomplishments of Thales himself or his contemporaries. According to one author, while visiting Egypt, Thales observed that when the Egyptians drew two intersecting lines, they would measure the vertical angles to make sure that they were equal. Thales concluded that one could prove that all vertical angles are equal if one accepted some general notions such as: all straight angles are equal, equals added to equals are equal, and equals subtracted from equals are equal. Pamphila says that, having learnt geometry from

1476-906: Is often neglected when credit is given for the WKB approximation . Jeffreys received the Gold Medal of the Royal Astronomical Society in 1937, the Royal Society 's Copley Medal in 1960, and the Royal Statistical Society 's Guy Medal in Gold in 1962. In 1948, he received the Charles Lagrange Prize from the Académie royale des Sciences, des Lettres et des Beaux-Arts de Belgique . He

1558-413: Is possible that 5–6 Mw earthquakes described in the historical record could be larger events occurring elsewhere that were felt moderately in the populated areas that produced written records. Documentation in the historic period may be sparse or incomplete, and not give a full picture of the geographic scope of an earthquake, or the historical record may only have earthquake records spanning a few centuries,

1640-402: Is rendered at last, its substance remaining under it, but transforming in qualities, that they say is the element and principle of things that are. …For it is necessary that there be some nature ( φύσις ), either one or more than one, from which become the other things of the object being saved... [The first philosophers] do not all agree as to the number and the nature of these principles. Thales

1722-576: Is the unity of substance. Not merely the empirical claim that all is water, but the deeper philosophical claim that all is one. For example, Friedrich Nietzsche , in his Philosophy in the Tragic Age of the Greeks , wrote: Greek philosophy seems to begin with an absurd notion, with the proposition that water is the primal origin and the womb of all things. Is it really necessary for us to take serious notice of this proposition? It is, and for three reasons. First, because it tells us something about

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1804-651: The 1857 Basilicata earthquake , the 1906 San Francisco earthquake, the 1964 Alaska earthquake , the 2004 Sumatra-Andaman earthquake , and the 2011 Great East Japan earthquake . Seismic waves produced by explosions or vibrating controlled sources are one of the primary methods of underground exploration in geophysics (in addition to many different electromagnetic methods such as induced polarization and magnetotellurics ). Controlled-source seismology has been used to map salt domes , anticlines and other geologic traps in petroleum -bearing rocks , faults , rock types, and long-buried giant meteor craters . For example,

1886-555: The Chicxulub Crater , which was caused by an impact that has been implicated in the extinction of the dinosaurs , was localized to Central America by analyzing ejecta in the Cretaceous–Paleogene boundary , and then physically proven to exist using seismic maps from oil exploration . Seismometers are sensors that detect and record the motion of the Earth arising from elastic waves. Seismometers may be deployed at

1968-610: The Hyades , supposed by the ancients to indicate the approach of rain when they rose with the Sun. According to Seneca , Thales explained the flooding of the Nile as due to the river being beaten back by the etesian wind. Harold Jeffreys Sir Harold Jeffreys , FRS (22 April 1891 – 18 March 1989) was a British geophysicist who made significant contributions to mathematics and statistics. His book, Theory of Probability , which

2050-674: The University of Durham ) and with the University of London External Programme . Jeffreys subsequently won a scholarship to study the Mathematical Tripos at St John's College, Cambridge , where he established a reputation as an excellent student: obtaining first-class marks for his papers in Part One of the Tripos, he was a Wrangler in Part Two, and in 1915 he was awarded the prestigious Smith's Prize . Jeffreys became

2132-454: The VAN method . Most seismologists do not believe that a system to provide timely warnings for individual earthquakes has yet been developed, and many believe that such a system would be unlikely to give useful warning of impending seismic events. However, more general forecasts routinely predict seismic hazard . Such forecasts estimate the probability of an earthquake of a particular size affecting

2214-554: The archonship of Damasius at Athens about 582 BC and that Thales was the first sage. The sages were associated with the Delphic maxims , a quote or maxim attributed to each one inscribed on the Temple of Apollo at Delphi . Thales has arguably the most famous of all, gnothi seauton or know thyself . According to the 10th-century Byzantine encyclopedia the Suda , the proverb

2296-438: The seked from the height of the stick and its distance from the point of insertion to the line of sight. Thales was also a noted astronomer, acknowledged in antiquity for describing the position of Ursa Minor , and he thought the constellation might be useful as a guide for navigation at sea. He calculated the duration of the year and the timings of the equinoxes and solstices . He is additionally attributed with calculating

2378-540: The " Moho ," it is the boundary between the Earth 's crust and the mantle . It is defined by the distinct change in velocity of seismological waves as they pass through changing densities of rock. In 1910, after studying the April 1906 San Francisco earthquake , Harry Fielding Reid put forward the " elastic rebound theory " which remains the foundation for modern tectonic studies. The development of this theory depended on

2460-546: The 17th century, Athanasius Kircher argued that earthquakes were caused by the movement of fire within a system of channels inside the Earth. Martin Lister (1638–1712) and Nicolas Lemery (1645–1715) proposed that earthquakes were caused by chemical explosions within the Earth. The Lisbon earthquake of 1755 , coinciding with the general flowering of science in Europe , set in motion intensified scientific attempts to understand

2542-408: The 20th century the 1960 Valdivia earthquake and the 1964 Alaska earthquake . Since then, the normal modes of the Earth have given us some of the strongest constraints on the deep structure of the Earth. One of the first attempts at the scientific study of earthquakes followed the 1755 Lisbon earthquake. Other notable earthquakes that spurred major advancements in the science of seismology include

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2624-668: The Earth's surface, in shallow vaults, in boreholes, or underwater . A complete instrument package that records seismic signals is called a seismograph . Networks of seismographs continuously record ground motions around the world to facilitate the monitoring and analysis of global earthquakes and other sources of seismic activity. Rapid location of earthquakes makes tsunami warnings possible because seismic waves travel considerably faster than tsunami waves. Seismometers also record signals from non-earthquake sources ranging from explosions (nuclear and chemical), to local noise from wind or anthropogenic activities, to incessant signals generated at

2706-533: The Egyptians, Thales was the first to inscribe in a circle a right-angled triangle, whereupon he sacrificed an ox . This is sometimes cited as history's first mathematical discovery. Due to the variations among testimonies, such as the story of the ox sacrifice being accredited to Pythagoras upon discovery of the Pythagorean theorem rather than Thales, some historians (such as D. R. Dicks) question whether such anecdotes have any historical worth whatsoever. It

2788-536: The Eminent Philosophers . While it is all we have, Diogenes wrote some eight centuries after Thales's death and his sources often contained "unreliable or even fabricated information". It is known Thales was from Miletus , a mercantile city settled at the mouth of the Maeander river . The dates of Thales's life are not exactly known, but are roughly established by a few datable events mentioned in

2870-416: The Greeks was Babylonia, another commonplace attribution of travel for a mathematically-minded philosopher. At least one ancient historian, Josephus , claims Thales visited Babylonia. Historians Roger L. Cooke and B.L. Van der Waerden come down on the side of Babylonian mathematics influencing the Greeks, citing the use of e. g. the sexagesimal system (or base 60). Cooke notes "This relation, however,

2952-606: The behaviour and causation of earthquakes. The earliest responses include work by John Bevis (1757) and John Michell (1761). Michell determined that earthquakes originate within the Earth and were waves of movement caused by "shifting masses of rock miles below the surface". In response to a series of earthquakes near Comrie in Scotland in 1839, a committee was formed in the United Kingdom in order to produce better detection methods for earthquakes. The outcome of this

3034-541: The considerable progress of earlier independent streams of work on the behavior of elastic materials and in mathematics. An early scientific study of aftershocks from a destructive earthquake came after the January 1920 Xalapa earthquake . An 80 kg (180 lb) Wiechert seismograph was brought to the Mexican city of Xalapa by rail after the earthquake. The instrument was deployed to record its aftershocks. Data from

3116-405: The discovery that a circle is bisected by its diameter, that the base angles of an isosceles triangle are equal and that vertical angles are equal. Two fundamental theorems of elementary geometry are customarily called Thales's theorem : one of them has to do with a triangle inscribed in a circle and having the circle's diameter as one side; the other, also called the intercept theorem ,

3198-511: The earth to a resolution of several hundred kilometers. This has enabled scientists to identify convection cells and other large-scale features such as the large low-shear-velocity provinces near the core–mantle boundary . Forecasting a probable timing, location, magnitude and other important features of a forthcoming seismic event is called earthquake prediction . Various attempts have been made by seismologists and others to create effective systems for precise earthquake predictions, including

3280-800: The earthquakes that could occur in a region and their characteristics and frequency of occurrence. Secondly, studying strong ground motions generated by earthquakes to assess the expected shaking from future earthquakes with similar characteristics. These strong ground motions could either be observations from accelerometers or seismometers or those simulated by computers using various techniques, which are then often used to develop ground motion prediction equations (or ground-motion models) [1] . Seismological instruments can generate large amounts of data. Systems for processing such data include: Thales Thales of Miletus ( / ˈ θ eɪ l iː z / THAY -leez ; ‹See Tfd› Greek : Θαλῆς ; c.  626/623   – c.  548/545 BC )

3362-425: The entire Earth "ring" like a resonant bell. This ringing is a mixture of normal modes with discrete frequencies and periods of approximately an hour or shorter. Normal mode motion caused by a very large earthquake can be observed for up to a month after the event. The first observations of normal modes were made in the 1960s as the advent of higher fidelity instruments coincided with two of the largest earthquakes of

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3444-406: The existence of a single ultimate substance . Thales theorized that this single substance was water . Thales thought the Earth floated on water. In mathematics, Thales is the namesake of Thales's theorem , and the intercept theorem can also be known as Thales's theorem. Thales was said to have calculated the heights of the pyramids and the distance of ships from the shore. In science, Thales

3526-447: The first among them. Also, while the other Seven Sages were strictly law-givers and statesmen and not speculative philosophers, Plutarch noted "it would seem that Thales was the only wise man of the time who carried his speculations beyond the realm of the practical." Thales's most famous idea was his philosophical and cosmological thesis that all is water, which comes down to us through a passage from Aristotle 's Metaphysics . In

3608-602: The first person in the western world to apply deductive reasoning to geometry, making him the West's "first mathematician." He is also credited with the West's oldest definition of number : a "collection of units", "following the Egyptian view". The evidence for the primacy of Thales comes to us from a book by Proclus , who lived a thousand years afterward but is believed to have had a copy of Eudemus 's lost book History of Geometry (4th century BC). Proclus wrote that Thales

3690-414: The first waves to appear on a seismogram as they are the fastest moving waves through solids. S-waves are transverse waves that move perpendicular to the direction of propagation. S-waves are slower than P-waves. Therefore, they appear later than P-waves on a seismogram. Fluids cannot support transverse elastic waves because of their low shear strength, so S-waves only travel in solids. Surface waves are

3772-475: The foundation of modern instrumental seismology and carried out seismological experiments using explosives. He is also responsible for coining the word "seismology." In 1889 Ernst von Rebeur-Paschwitz recorded the first teleseismic earthquake signal (an earthquake in Japan recorded at Pottsdam Germany). In 1897, Emil Wiechert 's theoretical calculations led him to conclude that the Earth's interior consists of

3854-406: The founder of this type of philosophy says that it is water. Aristotle further adds: Presumably he derived this assumption from seeing that the nutriment of everything is moist, and that heat itself is generated from moisture and depends upon it for its existence (and that from which a thing is generated is always its first principle). He derived his assumption from this; and also from the fact that

3936-432: The global seismographic monitoring has been for the detection and study of nuclear testing . Because seismic waves commonly propagate efficiently as they interact with the internal structure of the Earth, they provide high-resolution noninvasive methods for studying the planet's interior. One of the earliest important discoveries (suggested by Richard Dixon Oldham in 1906 and definitively shown by Harold Jeffreys in 1926)

4018-402: The height of the pyramids by their shadows at the moment when his own shadow was equal to his height. According to Plutarch, it pleased the pharoah Amasis . More practically, Thales was said to have the ability to measure the distances of ships at sea. These stories indicate familiarity with the intercept theorem, and for this reason the 26th proposition in the first book of Euclid's Elements

4100-521: The idea of having to worry about children. Nevertheless, several years later, anxious for family, he adopted his nephew Cybisthus. The culture of Archaic Greece was heavily influenced by those of the Levant and Mesopotamia . It is said Thales was engaged in trade and visited either Egypt or Babylonia . However, there is no strong evidence that Thales ever visited countries in the Near East , and

4182-406: The interior of the materials; surface waves that travel along surfaces or interfaces between materials; and normal modes , a form of standing wave. There are two types of body waves, pressure waves or primary waves (P-waves) and shear or secondary waves ( S waves ). P-waves are longitudinal waves that involve compression and expansion in the direction that the wave is moving and are always

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4264-402: The issue is disputed among scholars. Visits to such places were a commonplace attribution to various philosophers by later writers, especially when these writers tried to explain the origin of their mathematical knowledge, such as with Thales or Pythagoras or Eudoxus . Several ancient authors assume that Thales, at one point in his life, visited Egypt , where he learned about geometry. It

4346-480: The ocean floor and coasts induced by ocean waves (the global microseism ), to cryospheric events associated with large icebergs and glaciers. Above-ocean meteor strikes with energies as high as 4.2 × 10 J (equivalent to that released by an explosion of ten kilotons of TNT) have been recorded by seismographs, as have a number of industrial accidents and terrorist bombs and events (a field of study referred to as forensic seismology ). A major long-term motivation for

4428-434: The ocean processes responsible for the global background seismic microseism . By the 1960s, Earth science had developed to the point where a comprehensive theory of the causation of seismic events and geodetic motions had come together in the now well-established theory of plate tectonics . Seismic waves are elastic waves that propagate in solid or fluid materials. They can be divided into body waves that travel through

4510-672: The position of the Pleiades . Plutarch indicates that in his day (c. AD 100) there was an extant work, the Astronomy , composed in verse and attributed to Thales. While some say he left no writings, others say that he wrote On the Solstice and On the Equinox . The Nautical Star-guide has also been attributed to him, but this was disputed even in ancient times. No writing attributed to him has survived. Lobon of Argus asserted that

4592-398: The practice of dividing the day into 12 parts, and the polos , came to the Greeks from the Babylonians. Yet this too is disputed, for example by historian L. Zhmud, who points out the gnomon was known to both Egyptians and Babylonians, the division of the day into twelve parts (and by analogy the year) was known to the Egyptians already in the 2nd millennium BC , and the idea of the polos

4674-480: The primal origin of all things; second, because it does so in language devoid of image or fable, and finally, because contained in it, if only embryonically, is the thought, "all things are one." Megiston topos: apanta gar chorei ( Μέγιστον τόπος· ἄπαντα γὰρ χωρεῖ. ) The greatest is space, for it holds all things. —attributed to Thales Thales was known for introducing the theoretical and practical use of geometry to Greece, and has been described as

4756-400: The result of P- and S-waves interacting with the surface of the Earth. These waves are dispersive , meaning that different frequencies have different velocities. The two main surface wave types are Rayleigh waves , which have both compressional and shear motions, and Love waves , which are purely shear. Rayleigh waves result from the interaction of P-waves and vertically polarized S-waves with

4838-439: The seeds of everything have a moist nature, whereas water is the first principle of the nature of moist things." The 1870 book Dictionary of Greek and Roman Biography and Mythology noted: In his dogma that water is the origin of things, that is, that it is that out of which every thing arises, and into which every thing resolves itself, Thales may have followed Orphic cosmogonies, while, unlike them, he sought to establish

4920-413: The seismograph would eventually determine that the mainshock was produced along a shallow crustal fault. In 1926, Harold Jeffreys was the first to claim, based on his study of earthquake waves, that below the mantle, the core of the Earth is liquid. In 1937, Inge Lehmann determined that within Earth's liquid outer core there is a solid inner core . In 1950, Michael S. Longuet-Higgins elucidated

5002-564: The sources. According to the historian Herodotus , writing in the 5th century BC, Thales predicted a solar eclipse in 585 BC. Assuming one's acme (or floruit ) occurred at the age of 40, the chronicle of Apollodorus of Athens , written during the 2nd century BC, therefore placed Thales's birth about the year 625 BC. While the probability is that Thales was as Greek as most Milesians, Herodotus described Thales as "a Phoenician by remote descent". Diogenes Laërtius references Herodotus, Duris , and Democritus , who all agree "that Thales

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5084-465: The stars were balls of dirt on fire. He seemed to correctly gather that the moon reflects the Sun's light. A crater on the Moon is named in his honor. Rather than assuming that earthquakes were the result of supernatural whims, Thales explained them by theorizing that the Earth floats on water and that earthquakes occur when the Earth is rocked by waves. He is attributed with the first observation of

5166-476: The surface and can exist in any solid medium. Love waves are formed by horizontally polarized S-waves interacting with the surface, and can only exist if there is a change in the elastic properties with depth in a solid medium, which is always the case in seismological applications. Surface waves travel more slowly than P-waves and S-waves because they are the result of these waves traveling along indirect paths to interact with Earth's surface. Because they travel along

5248-564: The surface of the Earth, their energy decays less rapidly than body waves (1/distance vs. 1/distance), and thus the shaking caused by surface waves is generally stronger than that of body waves, and the primary surface waves are often thus the largest signals on earthquake seismograms . Surface waves are strongly excited when their source is close to the surface, as in a shallow earthquake or a near-surface explosion, and are much weaker for deep earthquake sources. Both body and surface waves are traveling waves; however, large earthquakes can also make

5330-470: The truth and preserved it." It is only through an appendix to the third edition of Jeffreys' book Scientific Inference that we know about Mary Cartwright 's method of proving that the number π is irrational . Jeffreys, like many of his peers, staunchly opposed the concept of continental drift as put forth by Alfred Wegener and Arthur Holmes . This opposition persisted even into the 1960s among his colleagues at Cambridge. For him, continental drift

5412-519: The truth of the assertion. Hence, Aristotle, immediately after he has called him the originator of philosophy brings forward the reasons which Thales was believed to have adduced in confirmation of that assertion; for that no written development of it, or indeed any book by Thales, was extant, is proved by the expressions which Aristotle uses when he brings forward the doctrines and proofs of the Milesian. (p. 1016) Most agree that Thales's stamp on thought

5494-496: The will of anthropomorphic gods and heroes . Instead, Thales aimed to explain natural phenomena via rational hypotheses that referenced natural processes themselves— Logos rather than mythos . Many, most notably Aristotle, regard him as the first philosopher in the Greek tradition . Rather than theologoi or mythologoi , Aristotle referred to the first philosophers as physiologoi , or natural philosophers, and Thales as

5576-433: The work, Aristotle reported Thales's theory that the arche or originating principle of nature was a single material substance : water. Aristotle then proceeded to proffer a number of conjectures based on his own observations to lend some credence to why Thales may have advanced this idea (though Aristotle did not hold it himself). While Aristotle's conjecture on why Thales held water as the originating principle of matter

5658-477: The writings of Thales amounted to two hundred lines. Thales thought the Earth must be a flat disk or mound of land and dirt which is floating in an expanse of water. Heraclitus Homericus states that Thales drew his conclusion from seeing moist substance turn into air, slime and earth. It seems likely that Thales viewed the land as coming from the water on which it floated and the oceans that surround it, perhaps inspired by observing silt deposits. He thought

5740-497: Was knighted in 1953. From 1939 to 1952 he was established as Director of the International Seismological Summary further known as International Seismological Centre . The textbook Probability Theory: The Logic of Science, written by the physicist and probability theorist Edwin T. Jaynes , is dedicated to Jeffreys. The dedication reads, "Dedicated to the memory of Sir Harold Jeffreys, who saw

5822-649: Was an Ancient Greek pre-Socratic philosopher from Miletus in Ionia , Asia Minor . Thales was one of the Seven Sages , founding figures of Ancient Greece . Many regard him as the first philosopher in the Greek tradition , breaking from the prior use of mythology to explain the world and instead using natural philosophy . He is thus otherwise referred to as the first to have engaged in mathematics , science , and deductive reasoning . The first philosophers followed him in explaining all of nature as based on

5904-528: Was an astronomer who reportedly predicted the weather and a solar eclipse . The discovery of the position of the constellation Ursa Major is also attributed to Thales, as well as the timings of the solstices and equinoxes . He was also an engineer , known for having diverted the Halys River . The main source concerning the details of Thales's life and career is the doxographer Diogenes Laërtius , in his third-century-AD work Lives and Opinions of

5986-419: Was attributed to Thales. They also indicate that he was familiar with the Egyptian seked , or seqed , the ratio of the run to the rise of a slope ( cotangent ). According to Kirk & Raven, all you need for this feat is three straight sticks pinned at one end and knowledge of your altitude. One stick goes vertically into the ground. A second is made level. With the third you sight the ship and calculate

6068-575: Was first published in 1939, played an important role in the revival of the objective Bayesian view of probability . Jeffreys was born in Fatfield , County Durham, England, the son of Robert Hal Jeffreys, headmaster of Fatfield Church School, and his wife, Elizabeth Mary Sharpe, a school teacher. He was educated at his father's school and at Rutherford Technical College, then studied at Armstrong College in Newcastle upon Tyne (at that time part of

6150-461: Was given to Thales, went the round of all the sages, and came back to Thales again. And he sent it to Apollo at Didyma , with this dedication...'Thales the Milesian, son of Examyas [dedicates this] to Delphinian Apollo after twice winning the prize from all the Greeks. ' " According to Diogenes Laërtius, Thales gained fame as a counselor when he advised the Milesians not to engage in a symmachia,

6232-460: Was not used outside of Greece at this time. Thales is recognized as one of the Seven Sages of Greece, semi-legendary wise statesmen and founding figures of Ancient Greece. While which seven one chooses may change, the seven has a canonical four which includes Thales, Solon of Athens, Pittacus of Mytilene , and Bias of Priene . Diogenes Laërtius tells us that the Seven Sages were created in

6314-635: Was on the Bayesian approach to probability (also see Jeffreys prior ), as well as the idea that the Earth's planetary core was liquid. By 1924 Jeffreys had developed a general method of approximating solutions to linear, second-order differential equations, including the Schrödinger equation . Although the Schrödinger equation was developed two years later, Wentzel, Kramers, and Brillouin were apparently unaware of this earlier work, so Jeffreys

6396-409: Was that the outer core of the earth is liquid. Since S-waves do not pass through liquids, the liquid core causes a "shadow" on the side of the planet opposite the earthquake where no direct S-waves are observed. In addition, P-waves travel much slower through the outer core than the mantle. Processing readings from many seismometers using seismic tomography , seismologists have mapped the mantle of

6478-430: Was the first to visit Egypt and bring the Egyptian study of mathematics to Greece, and that Thales "himself discovered many propositions and disclosed the underlying principles of many others to his successors, in some case his method being more general, in others more empirical." In addition to Proclus, Hieronymus of Rhodes (3rd century BC) also cites Thales as the first Greek mathematician. Proclus attributes to Thales

6560-413: Was the production of one of the first modern seismometers by James David Forbes , first presented in a report by David Milne-Home in 1842. This seismometer was an inverted pendulum, which recorded the measurements of seismic activity through the use of a pencil placed on paper above the pendulum. The designs provided did not prove effective, according to Milne's reports. From 1857, Robert Mallet laid

6642-523: Was the son of Examyas and Cleobulina, and belonged to the Thelidae who are Phoenicians and amongst the noblest descendants of Cadmus and Agenor " who had been banished from Phoenicia and that Thales was enrolled as a citizen in Miletus along with Neleus . However, Friedrich Nietzsche and others interpret this quote as meaning only that his ancestors were seafaring Cadmeians from Boeotia . It

6724-739: Was widely seen in Italy and abroad as being for failing to predict the earthquake and drew condemnation from the American Association for the Advancement of Science and the American Geophysical Union . However, the magazine also indicated that the population of Aquila do not consider the failure to predict the earthquake to be the reason for the indictment, but rather the alleged failure of the scientists to evaluate and communicate risk. The indictment claims that, at

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