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Spherical Earth

Spherical Earth

Overview
The concept of a spherical
Sphere
A sphere is a perfectly round geometrical object in three-dimensional space, such as the shape of a round ball. Like a circle in two dimensions, a perfect sphere is completely symmetrical around its center, with all points on the surface lying the same distance r from the center point...

 Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

dates back to ancient Greek philosophy
Greek philosophy
Ancient Greek philosophy arose in the 6th century BCE and continued through the Hellenistic period, at which point Ancient Greece was incorporated in the Roman Empire...

 from around the 6th century BC, but remained a matter of philosophical speculation until the 3rd century BC when Hellenistic astronomy established the spherical shape of the earth
Shape of the Earth
Shape of the Earth may refer to:* Figure of the Earth, scientific measurement of the Earth's shape.* Flat Earth, a model of the Earth as a flat plane or disk.* Spherical Earth, a model of the earth as a sphere or oblate spheroid.-See:...

 as a physical given. The Hellenistic paradigm was gradually adopted throughout the Old World
Old World
The Old World consists of those parts of the world known to classical antiquity and the European Middle Ages. It is used in the context of, and contrast with, the "New World" ....

 during Late Antiquity and the Middle Ages.
A practical demonstration of Earth's sphericity was achieved by Ferdinand Magellan
Ferdinand Magellan
Ferdinand Magellan was a Portuguese explorer. He was born in Sabrosa, in northern Portugal, and served King Charles I of Spain in search of a westward route to the "Spice Islands" ....

 and Juan Sebastian Elcano
Juan Sebastián Elcano
Juan Sebastián Elcano was a Basque Spanish explorer who completed the first circumnavigation of the world. As Ferdinand Magellan's second in command, Elcano took over after Magellan's death in the Philippines.-Early life:Elcano was born to Domingo Sebastián Elcano I and Catalina del Puerto...

's expedition's circumnavigation
Age of Discovery
The Age of Discovery, also known as the Age of Exploration and the Great Navigations , was a period in history starting in the early 15th century and continuing into the early 17th century during which Europeans engaged in intensive exploration of the world, establishing direct contacts with...

 (1519−1521).

The concept of a spherical Earth displaced earlier beliefs in a flat Earth
Flat Earth
The Flat Earth model is a belief that the Earth's shape is a plane or disk. Most ancient cultures have had conceptions of a flat Earth, including Greece until the classical period, the Bronze Age and Iron Age civilizations of the Near East until the Hellenistic period, India until the Gupta period ...

: In early Mesopotamian mythology, the world was portrayed as a flat disk floating in the ocean and surrounded by a spherical sky, and this forms the premise for early world maps like those of Anaximander
Anaximander
Anaximander was a pre-Socratic Greek philosopher who lived in Miletus, a city of Ionia; Milet in modern Turkey. He belonged to the Milesian school and learned the teachings of his master Thales...

 and Hecataeus of Miletus.
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Encyclopedia
The concept of a spherical
Sphere
A sphere is a perfectly round geometrical object in three-dimensional space, such as the shape of a round ball. Like a circle in two dimensions, a perfect sphere is completely symmetrical around its center, with all points on the surface lying the same distance r from the center point...

 Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

dates back to ancient Greek philosophy
Greek philosophy
Ancient Greek philosophy arose in the 6th century BCE and continued through the Hellenistic period, at which point Ancient Greece was incorporated in the Roman Empire...

 from around the 6th century BC, but remained a matter of philosophical speculation until the 3rd century BC when Hellenistic astronomy established the spherical shape of the earth
Shape of the Earth
Shape of the Earth may refer to:* Figure of the Earth, scientific measurement of the Earth's shape.* Flat Earth, a model of the Earth as a flat plane or disk.* Spherical Earth, a model of the earth as a sphere or oblate spheroid.-See:...

 as a physical given. The Hellenistic paradigm was gradually adopted throughout the Old World
Old World
The Old World consists of those parts of the world known to classical antiquity and the European Middle Ages. It is used in the context of, and contrast with, the "New World" ....

 during Late Antiquity and the Middle Ages.
A practical demonstration of Earth's sphericity was achieved by Ferdinand Magellan
Ferdinand Magellan
Ferdinand Magellan was a Portuguese explorer. He was born in Sabrosa, in northern Portugal, and served King Charles I of Spain in search of a westward route to the "Spice Islands" ....

 and Juan Sebastian Elcano
Juan Sebastián Elcano
Juan Sebastián Elcano was a Basque Spanish explorer who completed the first circumnavigation of the world. As Ferdinand Magellan's second in command, Elcano took over after Magellan's death in the Philippines.-Early life:Elcano was born to Domingo Sebastián Elcano I and Catalina del Puerto...

's expedition's circumnavigation
Age of Discovery
The Age of Discovery, also known as the Age of Exploration and the Great Navigations , was a period in history starting in the early 15th century and continuing into the early 17th century during which Europeans engaged in intensive exploration of the world, establishing direct contacts with...

 (1519−1521).

The concept of a spherical Earth displaced earlier beliefs in a flat Earth
Flat Earth
The Flat Earth model is a belief that the Earth's shape is a plane or disk. Most ancient cultures have had conceptions of a flat Earth, including Greece until the classical period, the Bronze Age and Iron Age civilizations of the Near East until the Hellenistic period, India until the Gupta period ...

: In early Mesopotamian mythology, the world was portrayed as a flat disk floating in the ocean and surrounded by a spherical sky, and this forms the premise for early world maps like those of Anaximander
Anaximander
Anaximander was a pre-Socratic Greek philosopher who lived in Miletus, a city of Ionia; Milet in modern Turkey. He belonged to the Milesian school and learned the teachings of his master Thales...

 and Hecataeus of Miletus. Other speculations on the shape of Earth include a seven-layered ziggurat
Ziggurat
Ziggurats were massive structures built in the ancient Mesopotamian valley and western Iranian plateau, having the form of a terraced step pyramid of successively receding stories or levels.Notable ziggurats include the Great Ziggurat of Ur near Nasiriyah, Iraq; the Ziggurat of Aqar Quf near...

 or cosmic mountain, alluded to in the Avesta
Avesta
The Avesta is the primary collection of sacred texts of Zoroastrianism, composed in the Avestan language.-Early transmission:The texts of the Avesta — which are all in the Avestan language — were composed over the course of several hundred years. The most important portion, the Gathas,...

 and ancient Persian writings (see seven climes), or a wheel, bowl, or four-cornered plane alluded to in the Rigveda
Rigveda
The Rigveda is an ancient Indian sacred collection of Vedic Sanskrit hymns...

.

The realization that the figure of the Earth
Figure of the Earth
The expression figure of the Earth has various meanings in geodesy according to the way it is used and the precision with which the Earth's size and shape is to be defined. The actual topographic surface is most apparent with its variety of land forms and water areas. This is, in fact, the surface...

 is more accurately described as an ellipsoid
Earth ellipsoid
An Earth ellipsoid is a mathematical figure approximating the shape of the Earth, used as a reference frame for computations in geodesy, astronomy and the geosciences...

 dates to the 18th century (Maupertius
Pierre Louis Maupertuis
Pierre-Louis Moreau de Maupertuis was a French mathematician, philosopher and man of letters. He became the Director of the Académie des Sciences, and the first President of the Berlin Academy of Science, at the invitation of Frederick the Great....

).
In the early 19th century, the flattening of the earth ellipsoid was determined to be of the order of 1/300 (Delambre, Everest
George Everest
Colonel Sir George Everest was a Welsh surveyor, geographer and Surveyor-General of India from 1830 to 1843.Sir George was largely responsible for completing the section of the Great Trigonometric Survey of India along the meridian arc from the south of India extending north to Nepal, a distance...

). The modern value as determined by the US DoD
United States Department of Defense
The United States Department of Defense is the U.S...

 World Geodetic System
World Geodetic System
The World Geodetic System is a standard for use in cartography, geodesy, and navigation. It comprises a standard coordinate frame for the Earth, a standard spheroidal reference surface for raw altitude data, and a gravitational equipotential surface that defines the nominal sea level.The latest...

 since the 1960s is close to 1/298.25.

Classical Greece


Though the earliest evidence of a spherical Earth comes from ancient Greek sources, there is no account of how the sphericity of the Earth was discovered. A plausible explanation is that it was "the experience of travellers that suggested such an explanation for the variation in the observable altitude
Altitude
Altitude or height is defined based on the context in which it is used . As a general definition, altitude is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The reference datum also often varies according to the context...

 and the change in the area of circumpolar stars, a change that was quite drastic between Greek settlements" around the eastern Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...

, particularly those between the Nile Delta
Nile Delta
The Nile Delta is the delta formed in Northern Egypt where the Nile River spreads out and drains into the Mediterranean Sea. It is one of the world's largest river deltas—from Alexandria in the west to Port Said in the east, it covers some 240 km of Mediterranean coastline—and is a rich...

 and the Crimea
Crimea
Crimea , or the Autonomous Republic of Crimea , is a sub-national unit, an autonomous republic, of Ukraine. It is located on the northern coast of the Black Sea, occupying a peninsula of the same name...

.

According to Diogenes Laertius
Diogenes Laertius
Diogenes Laertius was a biographer of the Greek philosophers. Nothing is known about his life, but his surviving Lives and Opinions of Eminent Philosophers is one of the principal surviving sources for the history of Greek philosophy.-Life:Nothing is definitively known about his life...

, "[ Pythagoras
Pythagoras
Pythagoras of Samos was an Ionian Greek philosopher, mathematician, and founder of the religious movement called Pythagoreanism. Most of the information about Pythagoras was written down centuries after he lived, so very little reliable information is known about him...

 ] was the first [Greek] who called the earth round; though Theophrastus
Theophrastus
Theophrastus , a Greek native of Eresos in Lesbos, was the successor to Aristotle in the Peripatetic school. He came to Athens at a young age, and initially studied in Plato's school. After Plato's death he attached himself to Aristotle. Aristotle bequeathed to Theophrastus his writings, and...

 attributes this to Parmenides
Parmenides
Parmenides of Elea was an ancient Greek philosopher born in Elea, a Greek city on the southern coast of Italy. He was the founder of the Eleatic school of philosophy. The single known work of Parmenides is a poem, On Nature, which has survived only in fragmentary form. In this poem, Parmenides...

, and Zeno
Zeno of Elea
Zeno of Elea was a pre-Socratic Greek philosopher of southern Italy and a member of the Eleatic School founded by Parmenides. Aristotle called him the inventor of the dialectic. He is best known for his paradoxes, which Bertrand Russell has described as "immeasurably subtle and profound".- Life...

 to Hesiod
Hesiod
Hesiod was a Greek oral poet generally thought by scholars to have been active between 750 and 650 BC, around the same time as Homer. His is the first European poetry in which the poet regards himself as a topic, an individual with a distinctive role to play. Ancient authors credited him and...

."

Pythagoras
Early Greek philosophers alluded to a spherical Earth, though with some ambiguity. Pythagoras
Pythagoras
Pythagoras of Samos was an Ionian Greek philosopher, mathematician, and founder of the religious movement called Pythagoreanism. Most of the information about Pythagoras was written down centuries after he lived, so very little reliable information is known about him...

 (6th century BC) was among those said to have originated the idea, but this may reflect the ancient Greek practice of ascribing every discovery to one or another of their ancient wise men. Some idea of the sphericity of the Earth seems to have been known to both Parmenides
Parmenides
Parmenides of Elea was an ancient Greek philosopher born in Elea, a Greek city on the southern coast of Italy. He was the founder of the Eleatic school of philosophy. The single known work of Parmenides is a poem, On Nature, which has survived only in fragmentary form. In this poem, Parmenides...

 and Empedocles
Empedocles
Empedocles was a Greek pre-Socratic philosopher and a citizen of Agrigentum, a Greek city in Sicily. Empedocles' philosophy is best known for being the originator of the cosmogenic theory of the four Classical elements...

 in the 5th century BC, and although the idea cannot reliably be ascribed to Pythagoras, it may, nevertheless have been formulated in the Pythagorean school
Pythagoreanism
Pythagoreanism was the system of esoteric and metaphysical beliefs held by Pythagoras and his followers, the Pythagoreans, who were considerably influenced by mathematics. Pythagoreanism originated in the 5th century BCE and greatly influenced Platonism...

 in the 5th century BC. After the 5th century BC, no Greek writer of repute thought the world was anything but round.

Herodotus
In The Histories, written 431–425 BC, Herodotus
Herodotus
Herodotus was an ancient Greek historian who was born in Halicarnassus, Caria and lived in the 5th century BC . He has been called the "Father of History", and was the first historian known to collect his materials systematically, test their accuracy to a certain extent and arrange them in a...

 dismisses a report of the sun observed shining from the north. This arises when discussing the circumnavigation of Africa undertaken by Phoenicia
Phoenicia
Phoenicia , was an ancient civilization in Canaan which covered most of the western, coastal part of the Fertile Crescent. Several major Phoenician cities were built on the coastline of the Mediterranean. It was an enterprising maritime trading culture that spread across the Mediterranean from 1550...

ns under Necho II
Necho II
Necho II was a king of the Twenty-sixth dynasty of Egypt .Necho II is most likely the pharaoh mentioned in several books of the Bible . The Book of Kings states that Necho met King Josiah of the Kingdom of Judah at Megiddo and killed him...

 c. 610–595 BC. (The Histories, 4.43) His dismissive comment attests to a widespread ignorance of the ecliptic
Ecliptic
The ecliptic is the plane of the earth's orbit around the sun. In more accurate terms, it is the intersection of the celestial sphere with the ecliptic plane, which is the geometric plane containing the mean orbit of the Earth around the Sun...

's inverted declination
Declination
In astronomy, declination is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. Declination in astronomy is comparable to geographic latitude, but projected onto the celestial sphere. Declination is measured in degrees north and...

 in a southern hemisphere
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...

.

Plato
Plato
Plato
Plato , was a Classical Greek philosopher, mathematician, student of Socrates, writer of philosophical dialogues, and founder of the Academy in Athens, the first institution of higher learning in the Western world. Along with his mentor, Socrates, and his student, Aristotle, Plato helped to lay the...

 (427–347 BC) travelled to southern Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

 to study Pythagorean mathematics. When he returned to Athens
Athens
Athens , is the capital and largest city of Greece. Athens dominates the Attica region and is one of the world's oldest cities, as its recorded history spans around 3,400 years. Classical Athens was a powerful city-state...

 and established his school, Plato also taught his students that Earth was a sphere though he offered no justifications. If man could soar high above the clouds, Earth would resemble "one of those balls which have leather coverings in twelve pieces, and is decked with various colours, of which the colours used by painters on earth are in a manner samples."
In Timaeus
Timaeus (dialogue)
Timaeus is one of Plato's dialogues, mostly in the form of a long monologue given by the title character, written circa 360 BC. The work puts forward speculation on the nature of the physical world and human beings. It is followed by the dialogue Critias.Speakers of the dialogue are Socrates,...

, his one work that was available throughout the Middle Ages in Latin, we read that the Creator "made the world in the form of a globe, round as from a lathe, having its extremes in every direction equidistant from the centre, the most perfect and the most like itself of all figures", though the word "world" normally refers to the universe.

Aristotle

Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...

 (384–322 BC) was Plato's prize student and "the mind of the school." Aristotle observed "there are star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...

s seen in Egypt
Egypt
Egypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...

 and [...] Cyprus
Cyprus
Cyprus , officially the Republic of Cyprus , is a Eurasian island country, member of the European Union, in the Eastern Mediterranean, east of Greece, south of Turkey, west of Syria and north of Egypt. It is the third largest island in the Mediterranean Sea.The earliest known human activity on the...

 which are not seen in the northerly regions."
Since this could only happen on a curved surface, he too believed Earth was a sphere "of no great size, for otherwise the effect of so slight a change of place would not be quickly apparent." (De caelo, 298a2–10)

Aristotle provided physical and observational arguments supporting the idea of a spherical Earth:
  • Every portion of the Earth tends toward the center until by compression and convergence they form a sphere. (De caelo, 297a9–21)
  • Travelers going south see southern constellations rise higher above the horizon; and
  • The shadow of Earth on the Moon during a lunar eclipse
    Lunar eclipse
    A lunar eclipse occurs when the Moon passes behind the Earth so that the Earth blocks the Sun's rays from striking the Moon. This can occur only when the Sun, Earth, and Moon are aligned exactly, or very closely so, with the Earth in the middle. Hence, a lunar eclipse can only occur the night of a...

     is round. (De caelo, 297b31–298a10)


The concepts of symmetry, equilibrium and cyclic repetition permeated Aristotle's work. In his Meteorology
Meteorology (Aristotle)
Meteorology is a treatise by Aristotle which contains his theories about the earth sciences. These include early accounts of water evaporation, weather phenomena, and earthquakes....

 he divided the world into five climatic zones: two temperate areas separated by a torrid zone near the equator
Equator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....

, and two cold inhospitable regions, "one near our upper or northern pole and the other near the ... southern pole," both impenetrable and girdled with ice (Meteorologica, 362a31–35). Although no humans could survive in the frigid zones, inhabitants in the southern temperate regions could exist.

Hellenistic era


Eratosthenes
Eratosthenes
Eratosthenes
Eratosthenes of Cyrene was a Greek mathematician, poet, athlete, geographer, astronomer, and music theorist.He was the first person to use the word "geography" and invented the discipline of geography as we understand it...

 (276–194 BC) estimated Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

's circumference around 240 BC. He had heard that in Syene the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

 was directly overhead at the summer solstice
Solstice
A solstice is an astronomical event that happens twice each year when the Sun's apparent position in the sky, as viewed from Earth, reaches its northernmost or southernmost extremes...

 whereas in Alexandria
Alexandria
Alexandria is the second-largest city of Egypt, with a population of 4.1 million, extending about along the coast of the Mediterranean Sea in the north central part of the country; it is also the largest city lying directly on the Mediterranean coast. It is Egypt's largest seaport, serving...

 it still cast a shadow. Using the differing angles the shadows made as the basis of his trigonometric calculations he estimated a circumference of around 250,000 stades
Ancient Greek units of measurement
Ancient Greek units of measurement would later create the foundation of Egyptian, and formed the basis of the later Roman system.Generally speaking, standards of measurement within the ancient Greek world varied according to location and epoch. Systems of ancient weights and measures evolved as...

. The length of a 'stade' is not precisely known, but Eratosthenes' figure only has an error of around five to fifteen percent. Eratosthenes used rough estimates and round numbers, but depending on the length of the stadion, his result is within a margin of between 2% and 20% of the actual meridional circumference
Circumference
The circumference is the distance around a closed curve. Circumference is a special perimeter.-Circumference of a circle:The circumference of a circle is the length around it....

, 40008 kilometres (24,859.9 mi). Note that Eratosthenes
Eratosthenes
Eratosthenes of Cyrene was a Greek mathematician, poet, athlete, geographer, astronomer, and music theorist.He was the first person to use the word "geography" and invented the discipline of geography as we understand it...

 could only measure the circumference of the Earth by assuming that the distance to the Sun is so great that the rays of sunlight
Sunlight
Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon.When the direct solar radiation is not blocked...

 are essentially parallel
Parallel (geometry)
Parallelism is a term in geometry and in everyday life that refers to a property in Euclidean space of two or more lines or planes, or a combination of these. The assumed existence and properties of parallel lines are the basis of Euclid's parallel postulate. Two lines in a plane that do not...

.

Seleucus of Seleucia
Seleucus of Seleucia
Seleucus of Seleucia
Seleucus of Seleucia was a Hellenistic astronomer and philosopher. Coming from Seleucia on the Tigris, the capital of the Seleucid empire, or, alternatively, Seleukia on the Red Sea, he is best known as a proponent of heliocentrism and for his theory of the origin of tides.- Heliocentric theory...

 (c. 190 BC), who lived in the Seleucia
Seleucia
Seleucia was the first capital of the Seleucid Empire, and one of the great cities of antiquity standing in Mesopotamia, on the Tigris River.Seleucia may refer to:...

 region of Mesopotamia
Mesopotamia
Mesopotamia is a toponym for the area of the Tigris–Euphrates river system, largely corresponding to modern-day Iraq, northeastern Syria, southeastern Turkey and southwestern Iran.Widely considered to be the cradle of civilization, Bronze Age Mesopotamia included Sumer and the...

, stated that the Earth is spherical (and actually orbits the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

, influenced by the heliocentric theory
Heliocentrism
Heliocentrism, or heliocentricism, is the astronomical model in which the Earth and planets revolve around a stationary Sun at the center of the universe. The word comes from the Greek . Historically, heliocentrism was opposed to geocentrism, which placed the Earth at the center...

 of Aristarchus of Samos
Aristarchus of Samos
Aristarchus, or more correctly Aristarchos , was a Greek astronomer and mathematician, born on the island of Samos, in Greece. He presented the first known heliocentric model of the solar system, placing the Sun, not the Earth, at the center of the known universe...

).

Posidonius
Posidonius
Posidonius
Posidonius "of Apameia" or "of Rhodes" , was a Greek Stoic philosopher, politician, astronomer, geographer, historian and teacher native to Apamea, Syria. He was acclaimed as the greatest polymath of his age...

 (c. 135 – 51 BC) put faith in Eratosthenes's method, though by observing the star Canopus
Canopus
Canopus |Alpha]] Carinae) is the brightest star in the southern constellation of Carina and Argo Navis, and the second brightest star in the night-time sky, after Sirius. Canopus's visual magnitude is −0.72, and it has an absolute magnitude of −5.53.Canopus is a supergiant of spectral...

, rather than the sun in establishing the Earth's circumference. In Ptolemy's Geographia, his result was favoured over that of Erastosthenes. Posidonius furthermore expressed the distance of the sun in earth radii.

Roman Empire


From its Greek origins, the idea of a spherical earth, along with much of Greek astronomical thought
Greek astronomy
Greek astronomy is astronomy written in the Greek language in classical antiquity. Greek astronomy is understood to include the ancient Greek, Hellenistic, Greco-Roman, and Late Antiquity eras. It is not limited geographically to Greece or to ethnic Greeks, as the Greek language had become the...

, slowly spread across the globe and ultimately became the adopted view in all major astronomical traditions:

In the west, the idea came naturally to the Romans through the lengthy process of cross-fertilization with Hellenistic civilization
Hellenistic civilization
Hellenistic civilization represents the zenith of Greek influence in the ancient world from 323 BCE to about 146 BCE...

. Many Roman authors such as Cicero
Cicero
Marcus Tullius Cicero , was a Roman philosopher, statesman, lawyer, political theorist, and Roman constitutionalist. He came from a wealthy municipal family of the equestrian order, and is widely considered one of Rome's greatest orators and prose stylists.He introduced the Romans to the chief...

 and Pliny
Pliny the Elder
Gaius Plinius Secundus , better known as Pliny the Elder, was a Roman author, naturalist, and natural philosopher, as well as naval and army commander of the early Roman Empire, and personal friend of the emperor Vespasian...

 refer in their works to the rotundity of the earth as a matter of course.

Strabo

It has been suggested that seafarers probably provided the first observational evidence that the Earth was not flat, based on observations of the horizon
Horizon
The horizon is the apparent line that separates earth from sky, the line that divides all visible directions into two categories: those that intersect the Earth's surface, and those that do not. At many locations, the true horizon is obscured by trees, buildings, mountains, etc., and the resulting...

. This argument was put forward by the geographer Strabo
Strabo
Strabo, also written Strabon was a Greek historian, geographer and philosopher.-Life:Strabo was born to an affluent family from Amaseia in Pontus , a city which he said was situated the approximate equivalent of 75 km from the Black Sea...

 (c. 64 BC – 24 AD), who suggested that the spherical shape of the Earth was probably known to seafarers around the Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...

 since at least the time of Homer
Homer
In the Western classical tradition Homer , is the author of the Iliad and the Odyssey, and is revered as the greatest ancient Greek epic poet. These epics lie at the beginning of the Western canon of literature, and have had an enormous influence on the history of literature.When he lived is...

, citing a line from the Odyssey
Odyssey
The Odyssey is one of two major ancient Greek epic poems attributed to Homer. It is, in part, a sequel to the Iliad, the other work ascribed to Homer. The poem is fundamental to the modern Western canon, and is the second—the Iliad being the first—extant work of Western literature...

as indicating that the poet Homer
Homer
In the Western classical tradition Homer , is the author of the Iliad and the Odyssey, and is revered as the greatest ancient Greek epic poet. These epics lie at the beginning of the Western canon of literature, and have had an enormous influence on the history of literature.When he lived is...

 was already aware of this as early as the 7th or 8th century BC. Strabo
Strabo
Strabo, also written Strabon was a Greek historian, geographer and philosopher.-Life:Strabo was born to an affluent family from Amaseia in Pontus , a city which he said was situated the approximate equivalent of 75 km from the Black Sea...

 cited various phenomena observed at sea as suggesting that the Earth was spherical. He observed that elevated lights or areas of land were visible to sailors at greater distances than those less elevated, and stated that the curvature of the sea was obviously responsible for this.

Claudius Ptolemy
Claudius Ptolemy (90–168 AD) lived in Alexandria
Alexandria
Alexandria is the second-largest city of Egypt, with a population of 4.1 million, extending about along the coast of the Mediterranean Sea in the north central part of the country; it is also the largest city lying directly on the Mediterranean coast. It is Egypt's largest seaport, serving...

, the centre of scholarship in the 2nd century. In the Almagest
Almagest
The Almagest is a 2nd-century mathematical and astronomical treatise on the apparent motions of the stars and planetary paths. Written in Greek by Claudius Ptolemy, a Roman era scholar of Egypt,...

, which remained the standard work of astronomy for 1,400 years, he advanced many arguments for the sphericity of the Earth. Among them was the observation that when sailing towards mountain
Mountain
Image:Himalaya_annotated.jpg|thumb|right|The Himalayan mountain range with Mount Everestrect 58 14 160 49 Chomo Lonzorect 200 28 335 52 Makalurect 378 24 566 45 Mount Everestrect 188 581 920 656 Tibetan Plateaurect 250 406 340 427 Rong River...

s, they seem to rise from the sea, indicating that they were hidden by the curved surface of the sea. He also gives separate arguments that the Earth is curved north-south and that it is curved east-west.

He also produced an eight-volume Geographia
Geographia (Ptolemy)
The Geography is Ptolemy's main work besides the Almagest...

dealing with the earth. The first part of the Geographia is a discussion of the data and of the methods he used. As with the model of the solar system in the Almagest, Ptolemy put all this information into a grand scheme. He assigned coordinates to all the places and geographic features he knew, in a grid
Grid (spatial index)
In the context of a spatial index, a grid is a regular tessellation of a manifold or 2-D surface that divides it into a series of contiguous cells, which can then be assigned unique identifiers and used for spatial indexing purposes...

 that spanned the globe (although most of this has been lost). Latitude
Latitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...

 was measured from the equator
Equator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....

, as it is today, but Ptolemy preferred to express it as the length of the longest day rather than degrees of arc
Degree (angle)
A degree , usually denoted by ° , is a measurement of plane angle, representing 1⁄360 of a full rotation; one degree is equivalent to π/180 radians...

 (the length of the midsummer
Midsummer
Midsummer may simply refer to the period of time centered upon the summer solstice, but more often refers to specific European celebrations that accompany the actual solstice, or that take place on a day between June 21 and June 24, and the preceding evening. The exact dates vary between different...

 day increases from 12h to 24h as you go from the equator to the polar circle
Polar circle
A polar circle is either the Arctic Circle or the Antarctic Circle. On Earth, the Arctic Circle is located at a latitude of  N, and the Antarctic Circle is located at a latitude of  S....

). He put the meridian
Meridian (geography)
A meridian is an imaginary line on the Earth's surface from the North Pole to the South Pole that connects all locations along it with a given longitude. The position of a point along the meridian is given by its latitude. Each meridian is perpendicular to all circles of latitude...

 of 0 longitude
Longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....

 at the most western land he knew, the Canary Islands
Canary Islands
The Canary Islands , also known as the Canaries , is a Spanish archipelago located just off the northwest coast of mainland Africa, 100 km west of the border between Morocco and the Western Sahara. The Canaries are a Spanish autonomous community and an outermost region of the European Union...

.

Geographia indicated the countries of "Serica
Seres
Seres was the ancient Greek and Roman name for the inhabitants of eastern Central Asia. It meant "of silk," or people of the "land where silk comes from." The country of the Seres was Serica....

" and "Sinae" (China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

) at the extreme right, beyond the island of "Taprobane" (Sri Lanka
Sri Lanka
Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka is a country off the southern coast of the Indian subcontinent. Known until 1972 as Ceylon , Sri Lanka is an island surrounded by the Indian Ocean, the Gulf of Mannar and the Palk Strait, and lies in the vicinity of India and the...

, oversized) and the "Aurea Chersonesus" (Southeast Asian peninsula
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...

).

Ptolemy also devised and provided instructions on how to create maps both of the whole inhabited world (oikoumenè) and of the Roman provinces. In the second part of the Geographia he provided the necessary topographic lists, and captions for the maps. His oikoumenè spanned 180 degrees of longitude from the Canary Islands in the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

 to China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

, and about 81 degrees of latitude from the Arctic to the East Indies
East Indies
East Indies is a term used by Europeans from the 16th century onwards to identify what is now known as Indian subcontinent or South Asia, Southeastern Asia, and the islands of Oceania, including the Malay Archipelago and the Philippines...

 and deep into Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

. Ptolemy was well aware that he knew about only a quarter of the globe.

Late Antiquity
Knowledge of the spherical shape of the Earth was received in scholarship of Late Antiquity
Late Antiquity
Late Antiquity is a periodization used by historians to describe the time of transition from Classical Antiquity to the Middle Ages, in both mainland Europe and the Mediterranean world. Precise boundaries for the period are a matter of debate, but noted historian of the period Peter Brown proposed...

 as a matter of course, in both Neoplatonism
Neoplatonism
Neoplatonism , is the modern term for a school of religious and mystical philosophy that took shape in the 3rd century AD, based on the teachings of Plato and earlier Platonists, with its earliest contributor believed to be Plotinus, and his teacher Ammonius Saccas...

 and Early Christianity
Early Christianity
Early Christianity is generally considered as Christianity before 325. The New Testament's Book of Acts and Epistle to the Galatians records that the first Christian community was centered in Jerusalem and its leaders included James, Peter and John....

.
Theological doubt informed by the flat Earth
Flat Earth
The Flat Earth model is a belief that the Earth's shape is a plane or disk. Most ancient cultures have had conceptions of a flat Earth, including Greece until the classical period, the Bronze Age and Iron Age civilizations of the Near East until the Hellenistic period, India until the Gupta period ...

 model implied in the Hebrew Bible
Hebrew Bible
The Hebrew Bible is a term used by biblical scholars outside of Judaism to refer to the Tanakh , a canonical collection of Jewish texts, and the common textual antecedent of the several canonical editions of the Christian Old Testament...

 inspired some early Christian scholars such as Lactantius
Lactantius
Lucius Caecilius Firmianus Lactantius was an early Christian author who became an advisor to the first Christian Roman emperor, Constantine I, guiding his religious policy as it developed, and tutor to his son.-Biography:...

, John Chrysostom
John Chrysostom
John Chrysostom , Archbishop of Constantinople, was an important Early Church Father. He is known for his eloquence in preaching and public speaking, his denunciation of abuse of authority by both ecclesiastical and political leaders, the Divine Liturgy of St. John Chrysostom, and his ascetic...

 and Athanasius of Alexandria
Athanasius of Alexandria
Athanasius of Alexandria [b. ca. – d. 2 May 373] is also given the titles St. Athanasius the Great, St. Athanasius I of Alexandria, St Athanasius the Confessor and St Athanasius the Apostolic. He was the 20th bishop of Alexandria. His long episcopate lasted 45 years Athanasius of Alexandria [b....

, but this remained an eccentric current and learned Christian authors like Basil of Caesarea
Basil of Caesarea
Basil of Caesarea, also called Saint Basil the Great, was the bishop of Caesarea Mazaca in Cappadocia, Asia Minor . He was an influential 4th century Christian theologian...

, Aurelius Ambrosius and Augustine of Hippo
Augustine of Hippo
Augustine of Hippo , also known as Augustine, St. Augustine, St. Austin, St. Augoustinos, Blessed Augustine, or St. Augustine the Blessed, was Bishop of Hippo Regius . He was a Latin-speaking philosopher and theologian who lived in the Roman Africa Province...

 were clearly aware of the sphericity of the Earth. "Flat Earthism" lingered longest in Syriac Christianity
Syriac Christianity
Syriac or Syrian Christianity , the Syriac-speaking Christians of Mesopotamia, comprises multiple Christian traditions of Eastern Christianity. With a history going back to the 1st Century AD, in modern times it is represented by denominations primarily in the Middle East and in Kerala, India....

, which tradition laid greater importance on a literalist interpretation of the Old Testament, and authors from that tradition such as Cosmas Indicopleustes
Cosmas Indicopleustes
Cosmas Indicopleustes was an Alexandrian merchant and later hermit, probably of Nestorian tendencies. He was a 6th-century traveller, who made several voyages to India during the reign of emperor Justinian...

 presented the Earth as flat as late as in the 6th century. This last remnant of the ancient model of the cosmos disappeared during the 7th century, and from the 8th century and the beginning medieval period
Early Middle Ages
The Early Middle Ages was the period of European history lasting from the 5th century to approximately 1000. The Early Middle Ages followed the decline of the Western Roman Empire and preceded the High Middle Ages...

, "no cosmographer worthy of note has called into question the sphericity of the Earth."

Spread to the East


With the rise of Greek culture in the east
Hellenistic period
The Hellenistic period or Hellenistic era describes the time which followed the conquests of Alexander the Great. It was so named by the historian J. G. Droysen. During this time, Greek cultural influence and power was at its zenith in Europe and Asia...

, Hellenistic astronomy filtered eastwards to ancient India
Ancient India
Ancient India may refer to:* The ancient history of India, which generally includes the ancient history of the Asian Subcontinent, including:*Science and technology in ancient India**Indian mathematics**Astronomy**List of Indian inventions...

 where its profound influence became apparent in the early centuries AD. The Greek concept of a spherical earth surrounded by the spheres of planets, vehemently supported by astronomers like Varahamihira
Varahamihira
Varāhamihira , also called Varaha or Mihira, was an Indian astronomer, mathematician, and astrologer who lived in Ujjain...

 and Brahmagupta
Brahmagupta
Brahmagupta was an Indian mathematician and astronomer who wrote many important works on mathematics and astronomy. His best known work is the Brāhmasphuṭasiddhānta , written in 628 in Bhinmal...

, supplanted the long-standing Indian cosmological belief into a flat and circular earth disk. The works of the classical Indian astronomer and mathematician
Indian mathematics
Indian mathematics emerged in the Indian subcontinent from 1200 BCE until the end of the 18th century. In the classical period of Indian mathematics , important contributions were made by scholars like Aryabhata, Brahmagupta, and Bhaskara II. The decimal number system in use today was first...

, Aryabhata
Aryabhata
Aryabhata was the first in the line of great mathematician-astronomers from the classical age of Indian mathematics and Indian astronomy...

 (476–550 AD), deal with the sphericity of the Earth and the motion of the planets. The final two parts of his Sanskrit
Sanskrit
Sanskrit , is a historical Indo-Aryan language and the primary liturgical language of Hinduism, Jainism and Buddhism.Buddhism: besides Pali, see Buddhist Hybrid Sanskrit Today, it is listed as one of the 22 scheduled languages of India and is an official language of the state of Uttarakhand...

 magnum opus, the Aryabhatiya
Aryabhatiya
Āryabhaṭīya or Āryabhaṭīyaṃ, a Sanskrit astronomical treatise, is the magnum opus and only extant work of the 5th century Indian mathematician, Āryabhaṭa.- Structure and style:...

, which were named the Kalakriya ("reckoning of time") and the Gola ("sphere"), state that the Earth is spherical and that its circumference is 4,967 yojana
Yojana
A Yojana is a Vedic measure of distance used in ancient India. The exact measurement is disputed amongst scholars with distances being given between 6 to 15 kilometers ....

s, which in modern units yields 39,968 km, close to the value already calculated by Eratosthenes
Eratosthenes
Eratosthenes of Cyrene was a Greek mathematician, poet, athlete, geographer, astronomer, and music theorist.He was the first person to use the word "geography" and invented the discipline of geography as we understand it...

 in the 3rd century BC.
Aryabhata also stated that the apparent rotation of the celestial objects was due to the actual rotation of the Earth. The Aryabhatiya in turn influenced medieval Islamic scholarship.

Middle Ages


Knowledge of the sphericity of the Earth survived into the medieval corpus of knowledge by direct transmission of the texts of Greek antiquity (Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...

), and via authors such as Isidore of Seville
Isidore of Seville
Saint Isidore of Seville served as Archbishop of Seville for more than three decades and is considered, as the historian Montalembert put it in an oft-quoted phrase, "le dernier savant du monde ancien"...

 and Beda Venerabilis.
It became increasingly traceable with the rise of scholasticism
Scholasticism
Scholasticism is a method of critical thought which dominated teaching by the academics of medieval universities in Europe from about 1100–1500, and a program of employing that method in articulating and defending orthodoxy in an increasingly pluralistic context...

 and medieval learning
Medieval university
Medieval university is an institution of higher learning which was established during High Middle Ages period and is a corporation.The first institutions generally considered to be universities were established in Italy, France, and England in the late 11th and the 12th centuries for the study of...

.
Spread of this knowledge beyond the immediate sphere of Greco-Roman scholarship was necessarily gradual, associated with the pace of Christianisation of Europe. For example, the first evidence of knowledge of the spherical shape of the Earth in Scandinavia
Scandinavia
Scandinavia is a cultural, historical and ethno-linguistic region in northern Europe that includes the three kingdoms of Denmark, Norway and Sweden, characterized by their common ethno-cultural heritage and language. Modern Norway and Sweden proper are situated on the Scandinavian Peninsula,...

 is a 12th-century Old Icelandic translation of Elucidarius.

A non-exhaustive list of more than a hundred Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 and vernacular writers from Late Antiquity
Late Antiquity
Late Antiquity is a periodization used by historians to describe the time of transition from Classical Antiquity to the Middle Ages, in both mainland Europe and the Mediterranean world. Precise boundaries for the period are a matter of debate, but noted historian of the period Peter Brown proposed...

 and the Middle Ages
Middle Ages
The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...

 who were aware that the earth was spherical, has been compiled by Reinhard Krüger, professor for Romance literature at the University of Stuttgart
University of Stuttgart
The University of Stuttgart is a university located in Stuttgart, Germany. It was founded in 1829 and is organized in 10 faculties....

.

Late Antiquity
Ampelius, Chalcidius, Macrobius, Martianus Capella
Martianus Capella
Martianus Minneus Felix Capella was a pagan writer of Late Antiquity, one of the earliest developers of the system of the seven liberal arts that structured early medieval education...

,
Basil of Caesarea
Basil of Caesarea
Basil of Caesarea, also called Saint Basil the Great, was the bishop of Caesarea Mazaca in Cappadocia, Asia Minor . He was an influential 4th century Christian theologian...

, Ambrose of Milan
Ambrose
Aurelius Ambrosius, better known in English as Saint Ambrose , was a bishop of Milan who became one of the most influential ecclesiastical figures of the 4th century. He was one of the four original doctors of the Church.-Political career:Ambrose was born into a Roman Christian family between about...

, Aurelius Augustinus, Paulus Orosius, Jordanes
Jordanes
Jordanes, also written Jordanis or Jornandes, was a 6th century Roman bureaucrat, who turned his hand to history later in life....

, Cassiodorus
Cassiodorus
Flavius Magnus Aurelius Cassiodorus Senator , commonly known as Cassiodorus, was a Roman statesman and writer, serving in the administration of Theodoric the Great, king of the Ostrogoths. Senator was part of his surname, not his rank.- Life :Cassiodorus was born at Scylletium, near Catanzaro in...

, Boethius, Visigoth king Sisebut.

Early Middle Ages
Isidore of Seville
Isidore of Seville
Saint Isidore of Seville served as Archbishop of Seville for more than three decades and is considered, as the historian Montalembert put it in an oft-quoted phrase, "le dernier savant du monde ancien"...

, Beda Venerabilis, Theodulf of Orléans
Theodulf of Orléans
Theodulf of Orléans , was the Bishop of Orléans during the reign of Charlemagne and Louis the Pious...

, Vergilius of Salzburg
Vergilius of Salzburg
Vergilius of Salzburg was an Irish churchman, an early astronomer and bishop of Salzburg. His obituary calls him the geometer.-Biography:...

,
Irish monk Dicuil
Dicuil
Dicuil, Irish monk and geographer, born in the second half of the 8th century.-Background:The exact dates of Dicuil's birth and death unknown...

, Rabanus Maurus
Rabanus Maurus
Rabanus Maurus Magnentius , also known as Hrabanus or Rhabanus, was a Frankish Benedictine monk, the archbishop of Mainz in Germany and a theologian. He was the author of the encyclopaedia De rerum naturis . He also wrote treatises on education and grammar and commentaries on the Bible...

, King Alfred of England
Alfred the Great
Alfred the Great was King of Wessex from 871 to 899.Alfred is noted for his defence of the Anglo-Saxon kingdoms of southern England against the Vikings, becoming the only English monarch still to be accorded the epithet "the Great". Alfred was the first King of the West Saxons to style himself...

, Remigius of Auxerre
Remigius of Auxerre
Remigius of Auxerre was a Benedictine monk during the Carolingian period, a teacher of Latin grammar, and a prolific author of commentaries on classical Greek and Latin texts...

, Johannes Scotus Eriugena
Johannes Scotus Eriugena
Johannes Scotus Eriugena was an Irish theologian, Neoplatonist philosopher, and poet. He is known for having translated and made commentaries upon the work of Pseudo-Dionysius.-Name:...

, Leo of Naples , Gerbert d’Aurillac (Pope Sylvester II).

High Middle Ages
Notker the German of Sankt-Gallen, Hermann of Reichenau
Hermann of Reichenau
Hermann of Reichenau , also called Hermannus Contractus or Hermannus Augiensis or Herman the Cripple, was an 11th century scholar, composer, music theorist, mathematician, and astronomer. He composed the Marian prayer Alma Redemptoris Mater...

, Hildegard von Bingen, Petrus Abaelardus, Honorius Augustodunensis
Honorius Augustodunensis
Honorius Augustodunensis , commonly known as Honorius of Autun, was a very popular 12th-century Christian theologian who wrote prolifically on many subjects. He wrote in a non-scholastic manner, with a lively style, and his works were approachable for the lay community in general...

, Gautier de Metz
Gautier de Metz
Gautier de Metz ) was a French priest and poet.About 1246, he wrote L'Image du monde , a work in poem form about creation, the Earth and the universe, wherein facts are mixed with fantasy. A chapter discussed astrology...

, Adam of Bremen
Adam of Bremen
Adam of Bremen was a German medieval chronicler. He lived and worked in the second half of the eleventh century. He is most famous for his chronicle Gesta Hammaburgensis Ecclesiae Pontificum .-Background:Little is known of his life other than hints from his own chronicles...

, Albertus Magnus
Albertus Magnus
Albertus Magnus, O.P. , also known as Albert the Great and Albert of Cologne, is a Catholic saint. He was a German Dominican friar and a bishop, who achieved fame for his comprehensive knowledge of and advocacy for the peaceful coexistence of science and religion. Those such as James A. Weisheipl...

, Thomas Aquinas
Thomas Aquinas
Thomas Aquinas, O.P. , also Thomas of Aquin or Aquino, was an Italian Dominican priest of the Catholic Church, and an immensely influential philosopher and theologian in the tradition of scholasticism, known as Doctor Angelicus, Doctor Communis, or Doctor Universalis...

, Berthold of Regensburg, Guillaume de Conches, Philippe de Thaon , Abu-Idrisi
Muhammad al-Idrisi
Abu Abd Allah Muhammad al-Idrisi al-Qurtubi al-Hasani al-Sabti or simply Al Idrisi was a Moroccan Muslim geographer, cartographer, Egyptologist and traveller who lived in Sicily, at the court of King Roger II. Muhammed al-Idrisi was born in Ceuta then belonging to the Almoravid Empire and died in...

, Bernardus Silvestris, Petrus Comestor
Petrus Comestor
-Biography:Born in Troyes, he was first attached to the Church of Notre-Dame in that city and habitually signed himself as "Presbyter Trecensis". Before 1148 he became dean of the chapter and received a benefice in 1148. About 1160 he formed one of the Chapter of Notre-Dame at Paris, and about the...

, Thierry de Chartres, Gautier de Châtillon, Alexander Neckam
Alexander Neckam
Alexander Neckam was an English scholar and teacher.-Biography:Born at St Albans, Hertfordshire, England, Neckam's mother, Hodierna, nursed the prince with her own son, who thus became Richard's foster-brother...

, Alain de Lille
Alain de Lille
Alain de Lille , French theologian and poet, was born, probably in Lille, some years before 1128.-Life:...

, Averroes
Averroes
' , better known just as Ibn Rushd , and in European literature as Averroes , was a Muslim polymath; a master of Aristotelian philosophy, Islamic philosophy, Islamic theology, Maliki law and jurisprudence, logic, psychology, politics, Arabic music theory, and the sciences of medicine, astronomy,...

, Snorri Sturluson
Snorri Sturluson
Snorri Sturluson was an Icelandic historian, poet, and politician. He was twice elected lawspeaker at the Icelandic parliament, the Althing...

, Moshe ben Maimon, Lambert de Saint-Omer , Gervasius of Tilbury, Robert Grosseteste
Robert Grosseteste
Robert Grosseteste or Grossetete was an English statesman, scholastic philosopher, theologian and Bishop of Lincoln. He was born of humble parents at Stradbroke in Suffolk. A.C...

, Johannes de Sacrobosco
Johannes de Sacrobosco
Johannes de Sacrobosco or Sacro Bosco was a scholar, monk, and astronomer who taught at the University of Paris and wrote the authoritative mediaeval astronomy text Tractatus de Sphaera.-Origins:Although described as English, his birthplace is unknown because Sacrobosco is...

, Thomas de Cantimpré, Peire de Corbian, Vincent de Beauvais, Robertus Anglicus
Robertus Anglicus
Robertus Anglicus was an English astronomer of the thirteenth century. He taught at the University of Montpellier, and possibly also at Paris. He is known as the author of a 1271 commentary on the De Sphera Mundi of Johannes de Sacrobosco. It includes a significant reference to the state of the...

, Juan Gil de Zámora , Ristoro d'Arezzo, Roger Bacon
Roger Bacon
Roger Bacon, O.F.M. , also known as Doctor Mirabilis , was an English philosopher and Franciscan friar who placed considerable emphasis on the study of nature through empirical methods...

, Jean de Meung, Brunetto Latini
Brunetto Latini
Brunetto Latini was an Italian philosopher, scholar and statesman.-Life:...

, Alfonso X of Castile
Alfonso X of Castile
Alfonso X was a Castilian monarch who ruled as the King of Castile, León and Galicia from 1252 until his death...

.

Late Middle Ages
Marco Polo
Marco Polo
Marco Polo was a Venetian merchant traveler from the Venetian Republic whose travels are recorded in Il Milione, a book which did much to introduce Europeans to Central Asia and China. He learned about trading whilst his father and uncle, Niccolò and Maffeo, travelled through Asia and apparently...

, Dante Alighieri
Dante Alighieri
Durante degli Alighieri, mononymously referred to as Dante , was an Italian poet, prose writer, literary theorist, moral philosopher, and political thinker. He is best known for the monumental epic poem La commedia, later named La divina commedia ...

, Meister Eckhart
Meister Eckhart
Eckhart von Hochheim O.P. , commonly known as Meister Eckhart, was a German theologian, philosopher and mystic, born near Gotha, in the Landgraviate of Thuringia in the Holy Roman Empire. Meister is German for "Master", referring to the academic title Magister in theologia he obtained in Paris...

, Enea Silvio Piccolomini (Pope Pius II), Perot de Garbelei  (divisiones mundi), Cecco d'Ascoli
Cecco d'Ascoli
Cecco d'Ascoli is the popular name of Francesco degli Stabili , a famous Italian encyclopaedist, physician and poet. Cecco is the diminutive of Francesco.-Life:Born in Ancarano, in the modern Abruzzo region, he devoted himself to the study of mathematics and astrology...

, Fazio degli Uberti , Levi ben Gershon, Konrad of Megenberg
Konrad of Megenberg
Konrad of Megenberg was a German Catholic scholar, and a versatile writer.- Biography :...

, Nicole Oresme, Petrus Aliacensis, Alfonso de la Torre , Toscanelli
Paolo dal Pozzo Toscanelli
Paolo dal Pozzo Toscanelli was an Italian mathematician, astronomer, and cosmographer.-Life:Paolo dal Pozzo Toscanelli was born in Florence, the son of the physician Dominic Toscanelli. Educated in mathematics at the University of Padua, he left in 1424 with the title of a doctor of...

, Brochard the German , Jean de Mandeville, Christine de Pizan
Christine de Pizan
Christine de Pizan was a Venetian-born late medieval author who challenged misogyny and stereotypes prevalent in the male-dominated medieval culture. As a poet, she was well known and highly regarded in her own day; she completed 41 works during her 30 year career , and can be regarded as...

, Geoffrey Chaucer
Geoffrey Chaucer
Geoffrey Chaucer , known as the Father of English literature, is widely considered the greatest English poet of the Middle Ages and was the first poet to have been buried in Poet's Corner of Westminster Abbey...

, William Caxton
William Caxton
William Caxton was an English merchant, diplomat, writer and printer. As far as is known, he was the first English person to work as a printer and the first to introduce a printing press into England...

, Martin Behaim
Martin Behaim
Martin Behaim , was a German mariner, artist, cosmographer, astronomer, philosopher, geographer and explorer in service to the King of Portugal.-Biography:The Behaim family had immigrated to Nuremberg because of religious persecution around...

, Christopher Columbus
Christopher Columbus
Christopher Columbus was an explorer, colonizer, and navigator, born in the Republic of Genoa, in northwestern Italy. Under the auspices of the Catholic Monarchs of Spain, he completed four voyages across the Atlantic Ocean that led to general European awareness of the American continents in the...

.
|}

Christian world


Isidore of Seville
Bishop Isidore of Seville
Isidore of Seville
Saint Isidore of Seville served as Archbishop of Seville for more than three decades and is considered, as the historian Montalembert put it in an oft-quoted phrase, "le dernier savant du monde ancien"...

 (560–636) taught in his widely read encyclopedia, the Etymologies
Etymologiae
Etymologiae is an encyclopedia compiled by Isidore of Seville towards the end of his life. It forms a bridge between a condensed epitome of classical learning at the close of Late Antiquity and the inheritance received, in large part through Isidore's work, by the early Middle Ages...

, that the Earth was round. While some writers have thought he referred to a spherical Earth; this and other writings make it clear that he considered the Earth to be disk or wheel-shaped.
He didn't admit the possibility of people dwelling at the antipodes, considering them as legendary and noting that there was no evidence for their existence.

Bede the Venerable

The monk Bede
Bede
Bede , also referred to as Saint Bede or the Venerable Bede , was a monk at the Northumbrian monastery of Saint Peter at Monkwearmouth, today part of Sunderland, England, and of its companion monastery, Saint Paul's, in modern Jarrow , both in the Kingdom of Northumbria...

 (c. 672–735) wrote in his influential treatise on computus, The Reckoning of Time, that the Earth was round, explaining the unequal length of daylight from "the roundness of the Earth, for not without reason is it called 'the orb of the world' on the pages of Holy Scripture and of ordinary literature. It is, in fact, set like a sphere in the middle of the whole universe." (De temporum ratione, 32). The large number of surviving manuscripts of The Reckoning of Time, copied to meet the Carolingian requirement that all priests should study the computus, indicates that many, if not most, priests were exposed to the idea of the sphericity of the Earth. Ælfric of Eynsham
Ælfric of Eynsham
Ælfric of Eynsham was an English abbot, as well as a consummate, prolific writer in Old English of hagiography, homilies, biblical commentaries, and other genres. He is also known variously as Ælfric the Grammarian , Ælfric of Cerne, and Ælfric the Homilist...

 paraphrased Bede into Old English, saying "Now the Earth's roundness and the Sun's orbit constitute the obstacle to the day's being equally long in every land."

Bede was lucid about earth's sphericity, writing "We call the earth a globe, not as if the shape of a sphere were expressed in the diversity of plains and mountains, but because, if all things are included in the outline, the earth's circumference will represent the figure of a perfect globe... For truly it is an orb placed in the center of the universe; in its width it is like a circle, and not circular like a shield but rather like a ball, and it extends from its center with perfect roundness on all sides."

Anania Shirakatsi
The 7th-century Armenian scholar Anania Shirakatsi
Anania Shirakatsi
Anania Shirakatsi was an Armenian mathematician, astronomer and geographer. He is commonly attributed to having written the Geography .-Life:Scholars are split on where exactly Anania was born...

  described the world as "being like an egg with a spherical yolk (the globe) surrounded by a layer of white (the atmosphere) and covered with a hard shell (the sky)."

High Middle Ages
During the High Middle Ages
High Middle Ages
The High Middle Ages was the period of European history around the 11th, 12th, and 13th centuries . The High Middle Ages were preceded by the Early Middle Ages and followed by the Late Middle Ages, which by convention end around 1500....

, the astronomical knowledge in Christian Europe is extended beyond what was transmitted directly from ancient authors by transmission of learning from Medieval Islamic astronomy. An early recipient of such learning was Gerbert d'Aurillac, the later Pope Silvester II.

Saint Hildegard (Hildegard von Bingen, 1098–1179), depicts the spherical earth several times in her work Liber Divinorum Operum. http://brunelleschi.imss.fi.it/galileopalazzostrozzi/object/HildegardOfBingenLiberDivinorumOperum.html

Johannes de Sacrobosco
Johannes de Sacrobosco
Johannes de Sacrobosco or Sacro Bosco was a scholar, monk, and astronomer who taught at the University of Paris and wrote the authoritative mediaeval astronomy text Tractatus de Sphaera.-Origins:Although described as English, his birthplace is unknown because Sacrobosco is...

 (c. 1195 – c. 1256 AD) wrote a famous work on Astronomy called Tractatus de Sphaera, based on Ptolemy, in which he considers the Earth to be spherical.

Late Middle Ages

Dante's Divine Comedy, written in Italian in the early 14th century, portrays Earth as a sphere, discussing implications such as the different stars visible in the southern hemisphere
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...

, the altered position of the sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

, and the various timezones of the Earth. Also, the Elucidarium of Honorius Augustodunensis
Honorius Augustodunensis
Honorius Augustodunensis , commonly known as Honorius of Autun, was a very popular 12th-century Christian theologian who wrote prolifically on many subjects. He wrote in a non-scholastic manner, with a lively style, and his works were approachable for the lay community in general...

 (c. 1120), an important manual for the instruction of lesser clergy, which was translated into Middle English
Middle English
Middle English is the stage in the history of the English language during the High and Late Middle Ages, or roughly during the four centuries between the late 11th and the late 15th century....

, Old French
Old French
Old French was the Romance dialect continuum spoken in territories that span roughly the northern half of modern France and parts of modern Belgium and Switzerland from the 9th century to the 14th century...

, Middle High German
Middle High German
Middle High German , abbreviated MHG , is the term used for the period in the history of the German language between 1050 and 1350. It is preceded by Old High German and followed by Early New High German...

, Old Russian, Middle Dutch
Middle Dutch
Middle Dutch is a collective name for a number of closely related West Germanic dialects which were spoken and written between 1150 and 1500...

, Old Norse
Old Norse
Old Norse is a North Germanic language that was spoken by inhabitants of Scandinavia and inhabitants of their overseas settlements during the Viking Age, until about 1300....

, Icelandic
Icelandic language
Icelandic is a North Germanic language, the main language of Iceland. Its closest relative is Faroese.Icelandic is an Indo-European language belonging to the North Germanic or Nordic branch of the Germanic languages. Historically, it was the westernmost of the Indo-European languages prior to the...

, Spanish
Spanish language
Spanish , also known as Castilian , is a Romance language in the Ibero-Romance group that evolved from several languages and dialects in central-northern Iberia around the 9th century and gradually spread with the expansion of the Kingdom of Castile into central and southern Iberia during the...

, and several Italian dialects, explicitly refers to a spherical Earth. Likewise, the fact that Bertold von Regensburg (mid-13th century) used the spherical Earth as a sermon
Sermon
A sermon is an oration by a prophet or member of the clergy. Sermons address a Biblical, theological, religious, or moral topic, usually expounding on a type of belief, law or behavior within both past and present contexts...

ic illustration shows that he could assume this knowledge among his congregation. The sermon was held in the vernacular German, and thus was not intended for a learned audience.

Portuguese
Portugal
Portugal , officially the Portuguese Republic is a country situated in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of Europe, and is bordered by the Atlantic Ocean to the West and South and by Spain to the North and East. The Atlantic archipelagos of the...

 exploration of Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

 and Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...

, Columbus
Christopher Columbus
Christopher Columbus was an explorer, colonizer, and navigator, born in the Republic of Genoa, in northwestern Italy. Under the auspices of the Catholic Monarchs of Spain, he completed four voyages across the Atlantic Ocean that led to general European awareness of the American continents in the...

 voyage to the Americas
Americas
The Americas, or America , are lands in the Western hemisphere, also known as the New World. In English, the plural form the Americas is often used to refer to the landmasses of North America and South America with their associated islands and regions, while the singular form America is primarily...

 (1492) and finally Ferdinand Magellan
Ferdinand Magellan
Ferdinand Magellan was a Portuguese explorer. He was born in Sabrosa, in northern Portugal, and served King Charles I of Spain in search of a westward route to the "Spice Islands" ....

's circumnavigation of the earth (1519–21) provided practical proofs for the global shape of the earth, while European colonists planted the idea in the American colonies.

Islamic world


Islamic astronomy inherited the idea of a spherical earth from the Greek astronomical tradition
Greek astronomy
Greek astronomy is astronomy written in the Greek language in classical antiquity. Greek astronomy is understood to include the ancient Greek, Hellenistic, Greco-Roman, and Late Antiquity eras. It is not limited geographically to Greece or to ethnic Greeks, as the Greek language had become the...

. The Islamic theoretical framework largely relied on the fundamental contributions of Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...

 (De caelo) and Ptolemy
Ptolemy
Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...

 (Almagest
Almagest
The Almagest is a 2nd-century mathematical and astronomical treatise on the apparent motions of the stars and planetary paths. Written in Greek by Claudius Ptolemy, a Roman era scholar of Egypt,...

), both of which worked with the premise that the earth was spherical and at the center of the universe (geocentric model
Geocentric model
In astronomy, the geocentric model , is the superseded theory that the Earth is the center of the universe, and that all other objects orbit around it. This geocentric model served as the predominant cosmological system in many ancient civilizations such as ancient Greece...

).

Early Islamic scholars recognized earth's sphericity, leading Muslim mathematicians
Islamic mathematics
In the history of mathematics, mathematics in medieval Islam, often termed Islamic mathematics or Arabic mathematics, covers the body of mathematics preserved and developed under the Islamic civilization between circa 622 and 1600...

 to develop spherical trigonometry
Spherical trigonometry
Spherical trigonometry is a branch of spherical geometry which deals with polygons on the sphere and the relationships between the sides and the angles...

 in order to further mensuration and to calculate the distance and direction from any given point on the Earth to Mecca
Mecca
Mecca is a city in the Hijaz and the capital of Makkah province in Saudi Arabia. The city is located inland from Jeddah in a narrow valley at a height of above sea level...

. This determined the Qibla
Qibla
The Qiblah , also transliterated as Qibla, Kiblah or Kibla, is the direction that should be faced when a Muslim prays during salah...

, or Muslim direction of prayer.

Al-Ma'mun
Around 830 AD, Caliph Al-Ma'mun
Al-Ma'mun
Abū Jaʿfar Abdullāh al-Māʾmūn ibn Harūn was an Abbasid caliph who reigned from 813 until his death in 833...

 commissioned a group of Muslim astronomers
Islamic astronomy
Islamic astronomy or Arabic astronomy comprises the astronomical developments made in the Islamic world, particularly during the Islamic Golden Age , and mostly written in the Arabic language. These developments mostly took place in the Middle East, Central Asia, Al-Andalus, and North Africa, and...

 and Muslim geographers
Islamic geography
Geography and cartography in medieval Islam refers to the advancement of geography, cartography and the earth sciences in the medieval Islamic civilization....

 to measure the distance from Tadmur (Palmyra
Palmyra
Palmyra was an ancient city in Syria. In the age of antiquity, it was an important city of central Syria, located in an oasis 215 km northeast of Damascus and 180 km southwest of the Euphrates at Deir ez-Zor. It had long been a vital caravan city for travellers crossing the Syrian desert...

) to al-Raqqah
Ar Raqqah
Ar-Raqqah , also spelled Rakka, is a city in north central Syria located on the north bank of the Euphrates, about 160 km east of Aleppo. It is the capital of the Ar-Raqqah Governorate and one of the main cities of the historical Diyār Muḍar, the western part of the Jazīra...

, in modern Syria. They found the cities to be separated by one degree of latitude
Latitude
In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...

 and the meridian arc
Meridian arc
In geodesy, a meridian arc measurement is a highly accurate determination of the distance between two points with the same longitude. Two or more such determinations at different locations then specify the shape of the reference ellipsoid which best approximates the shape of the geoid. This...

 distance between them to be 66 miles and thus calculated the Earth's circumference to be 24,000 miles.

Another estimate given by his astronomers was 56 Arabic miles (111.8 km) per degree, which corresponds to a circumference of 40,248 km, very close to the currently modern values of 111.3 km per degree and 40,068 km circumference, respectively.

Al-Farghānī
Al-Farghānī (Latinized as Alfraganus) was a Persian astronomer of the 9th century involved in measuring the diameter of the Earth, and commissioned by Al-Ma'mun. His estimate given above for a degree (56 Arabic miles) was much more accurate than the 60 Roman miles (89.7 km) given by Ptolemy. Christopher Columbus
Christopher Columbus
Christopher Columbus was an explorer, colonizer, and navigator, born in the Republic of Genoa, in northwestern Italy. Under the auspices of the Catholic Monarchs of Spain, he completed four voyages across the Atlantic Ocean that led to general European awareness of the American continents in the...

 uncritically used Alfraganus's figure as if it were in Roman miles instead of in Arabic miles, in order to prove a smaller size of the Earth than that propounded by Ptolemy.

Biruni

Abu Rayhan Biruni (973-1048) used a new method to accurately compute the Earth's circumference
Circumference
The circumference is the distance around a closed curve. Circumference is a special perimeter.-Circumference of a circle:The circumference of a circle is the length around it....

, by which he arrived at a value that was close to modern values for the Earth's circumference. His estimate of 6,339.9 km for the Earth radius
Earth radius
Because the Earth is not perfectly spherical, no single value serves as its natural radius. Distances from points on the surface to the center range from 6,353 km to 6,384 km...

 was only 16.8 km less than the modern value of 6,356.7 km. In contrast to his predecessors who measured the Earth's circumference by sighting the Sun simultaneously from two different locations, Biruni developed a new method of using trigonometric
Trigonometry
Trigonometry is a branch of mathematics that studies triangles and the relationships between their sides and the angles between these sides. Trigonometry defines the trigonometric functions, which describe those relationships and have applicability to cyclical phenomena, such as waves...

 calculations based on the angle between a plain
Plain
In geography, a plain is land with relatively low relief, that is flat or gently rolling. Prairies and steppes are types of plains, and the archetype for a plain is often thought of as a grassland, but plains in their natural state may also be covered in shrublands, woodland and forest, or...

 and mountain
Mountain
Image:Himalaya_annotated.jpg|thumb|right|The Himalayan mountain range with Mount Everestrect 58 14 160 49 Chomo Lonzorect 200 28 335 52 Makalurect 378 24 566 45 Mount Everestrect 188 581 920 656 Tibetan Plateaurect 250 406 340 427 Rong River...

 top which yielded more accurate measurements of the Earth's circumference and made it possible for it to be measured by a single person from a single location.
Biruni's method was intended to avoid "walking across hot, dusty deserts" and the idea came to him when he was on top of a tall mountain in India. From the top of the mountain, he sighted the angle to the horizon which, along with the mountain's height (which he calculated beforehand), allowed him to calculate the curvature of the Earth.
He also made use of algebra
Algebra
Algebra is the branch of mathematics concerning the study of the rules of operations and relations, and the constructions and concepts arising from them, including terms, polynomials, equations and algebraic structures...

 to formulate trigonometric equations and used the astrolabe
Astrolabe
An astrolabe is an elaborate inclinometer, historically used by astronomers, navigators, and astrologers. Its many uses include locating and predicting the positions of the Sun, Moon, planets, and stars, determining local time given local latitude and longitude, surveying, triangulation, and to...

 to measure angles.

John J. O'Connor and Edmund F. Robertson write in the MacTutor History of Mathematics archive
MacTutor History of Mathematics archive
The MacTutor History of Mathematics archive is a website maintained by John J. O'Connor and Edmund F. Robertson and hosted by the University of St Andrews in Scotland...

:

Circumnavigation of the globe



The first direct demonstration of Earth's sphericity came in the form of the first circumnavigation in history, an expedition captained by Portuguese explorer Ferdinand Magellan
Ferdinand Magellan
Ferdinand Magellan was a Portuguese explorer. He was born in Sabrosa, in northern Portugal, and served King Charles I of Spain in search of a westward route to the "Spice Islands" ....

. The expedition was financed by the Spanish Crown. On August 10, 1519, the five ships under Magellan's command departed from Seville
Seville
Seville is the artistic, historic, cultural, and financial capital of southern Spain. It is the capital of the autonomous community of Andalusia and of the province of Seville. It is situated on the plain of the River Guadalquivir, with an average elevation of above sea level...

. They crossed the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

, passed through the Strait of Magellan
Strait of Magellan
The Strait of Magellan comprises a navigable sea route immediately south of mainland South America and north of Tierra del Fuego...

, crossed the Pacific, and arrived in Cebu
Cebu
Cebu is a province in the Philippines, consisting of Cebu Island and 167 surrounding islands. It is located to the east of Negros, to the west of Leyte and Bohol islands...

, where Magellan was killed by Philippine natives in a battle. His second in command, the Spaniard Juan Sebastián Elcano
Juan Sebastián Elcano
Juan Sebastián Elcano was a Basque Spanish explorer who completed the first circumnavigation of the world. As Ferdinand Magellan's second in command, Elcano took over after Magellan's death in the Philippines.-Early life:Elcano was born to Domingo Sebastián Elcano I and Catalina del Puerto...

, continued the expedition and, on September 6, 1522, arrived at Seville, completing the circumnavigation. Charles I of Spain, in recognition of his feat, gave Elcano a coat of arms
Coat of arms
A coat of arms is a unique heraldic design on a shield or escutcheon or on a surcoat or tabard used to cover and protect armour and to identify the wearer. Thus the term is often stated as "coat-armour", because it was anciently displayed on the front of a coat of cloth...

 with the motto Primus circumdedisti me (in Latin, "You went around me first").

A circumnavigation alone does not prove that the earth is spherical. It could be cylindric or irregularly globular or one of many other shapes. Still, combined with trigonometric evidence of the form used by Eratosthenes 1,700 years prior, the Magellan expedition removed any reasonable doubt in educated circles in Europe.

Ming China


In the 17th century, the idea of a spherical earth, now considerably advanced by Western Astronomy
Scientific revolution
The Scientific Revolution is an era associated primarily with the 16th and 17th centuries during which new ideas and knowledge in physics, astronomy, biology, medicine and chemistry transformed medieval and ancient views of nature and laid the foundations for modern science...

, ultimately spread to Ming China, when Jesuit missionaries
Jesuit China missions
The history of the missions of the Jesuits in China is part of the history of relations between China and the Western world. The missionary efforts and other work of the Society of Jesus, or Jesuits, between the 16th and 17th century played a significant role in continuing the transmission of...

, who held high positions as astronomers at the imperial court, successfully challenged the Chinese belief that the earth was flat and square.

Summary of evidence for a spherical earth


These are given in an order which approximates how they were observed historically:
  1. When at sea it is possible to see high mountains or elevated lights in the distance before lower lying ground and the masts of boats before the hull. It is also possible to see further by climbing higher in the ship, or, when on land, on high cliffs.
  2. The sun is lower in the sky as you travel north, but stars such as Polaris, the north star, are higher in the sky. Other bright stars such as Canopus
    Canopus
    Canopus |Alpha]] Carinae) is the brightest star in the southern constellation of Carina and Argo Navis, and the second brightest star in the night-time sky, after Sirius. Canopus's visual magnitude is −0.72, and it has an absolute magnitude of −5.53.Canopus is a supergiant of spectral...

    , visible in Egypt, disappear from the sky.
  3. The earth throws a circular shadow on the moon during a lunar eclipse
    Lunar eclipse
    A lunar eclipse occurs when the Moon passes behind the Earth so that the Earth blocks the Sun's rays from striking the Moon. This can occur only when the Sun, Earth, and Moon are aligned exactly, or very closely so, with the Earth in the middle. Hence, a lunar eclipse can only occur the night of a...

    .
  4. The times reported for lunar eclipses (which are seen simultaneously) are many hours later in the east (e.g. India) than in the west (e.g. Europe). Local times are confirmed later by travel using chronometers and telegraphic communication.
  5. When you travel far south, to Ethiopia or India, the sun throws a shadow south at certain times of the year. Even further (e.g. Argentina) and the shadow is always in the south.
  6. It is possible to circumnavigate the world; that is, to travel around the world and return to where you started.
  7. Travelers who circumnavigate the earth observe the gain or loss of a day relative to those who did not. See also International Date Line
    International Date Line
    The International Date Line is a generally north-south imaginary line on the surface of the Earth, passing through the middle of the Pacific Ocean, that designates the place where each calendar day begins...

    .
  8. An artificial satellite can circle the earth continuously and even be geostationary.
  9. The earth appears as a disc on photographs taken from space, regardless of the vantage point.


Several of these arguments have alternative explanations by themselves. e.g. the shadow thrown by a lunar eclipse could be caused by a disk-shaped earth. Similarly the north-south movement of stars in the sky with travel could mean they are much closer to earth. However, the arguments strengthen each together.

Geodesy



Geodesy
Geodesy
Geodesy , also named geodetics, a branch of earth sciences, is the scientific discipline that deals with the measurement and representation of the Earth, including its gravitational field, in a three-dimensional time-varying space. Geodesists also study geodynamical phenomena such as crustal...

, also called geodetics, is the scientific discipline that deals with the measurement and representation of the Earth, its gravitation
Gravitation
Gravitation, or gravity, is a natural phenomenon by which physical bodies attract with a force proportional to their mass. Gravitation is most familiar as the agent that gives weight to objects with mass and causes them to fall to the ground when dropped...

al field and geodynamic phenomena (polar motion
Polar motion
Polar motion of the earth is the movement of Earth's rotational axis across its surface. This is measured with respect to a reference frame in which the solid Earth is fixed...

, Earth tide
Tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....

s, and crustal motion) in three-dimensional time-varying space.

Geodesy is primarily concerned with positioning and the gravity field and geometrical aspects of their temporal variations, although it can also include the study of Earth's magnetic field
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...

. Especially in the German
German language
German is a West Germanic language, related to and classified alongside English and Dutch. With an estimated 90 – 98 million native speakers, German is one of the world's major languages and is the most widely-spoken first language in the European Union....

 speaking world, geodesy is divided into geomensuration ("Erdmessung" or "höhere Geodäsie"), which is concerned with measuring the Earth on a global scale, and surveying
Geophysical survey
Geophysical survey is the systematic collection of geophysical data for spatial studies. Geophysical surveys may use a great variety of sensing instruments, and data may be collected from above or below the Earth's surface or from aerial or marine platforms. Geophysical surveys have many...

 ("Ingenieurgeodäsie"), which is concerned with measuring parts of the surface.

The Earth's shape can be thought of in at least two ways;
  • as the shape of the geoid
    Geoid
    The geoid is that equipotential surface which would coincide exactly with the mean ocean surface of the Earth, if the oceans were in equilibrium, at rest , and extended through the continents . According to C.F...

    , the mean sea level of the world ocean; or
  • as the shape of Earth's land surface as it rises above and falls below the sea.


As the science of geodesy
Geodesy
Geodesy , also named geodetics, a branch of earth sciences, is the scientific discipline that deals with the measurement and representation of the Earth, including its gravitational field, in a three-dimensional time-varying space. Geodesists also study geodynamical phenomena such as crustal...

 measured Earth more accurately, the shape of the geoid was first found not to be a perfect sphere but to approximate an oblate spheroid
Spheroid
A spheroid, or ellipsoid of revolution is a quadric surface obtained by rotating an ellipse about one of its principal axes; in other words, an ellipsoid with two equal semi-diameters....

, a specific type of ellipsoid. More recent measurements have measured the geoid to unprecedented accuracy, revealing mass concentrations beneath Earth's surface.

See also

  • Celestial sphere
    Celestial sphere
    In astronomy and navigation, the celestial sphere is an imaginary sphere of arbitrarily large radius, concentric with the Earth and rotating upon the same axis. All objects in the sky can be thought of as projected upon the celestial sphere. Projected upward from Earth's equator and poles are the...

  • Earth radius
    Earth radius
    Because the Earth is not perfectly spherical, no single value serves as its natural radius. Distances from points on the surface to the center range from 6,353 km to 6,384 km...

  • Figure of the Earth
    Figure of the Earth
    The expression figure of the Earth has various meanings in geodesy according to the way it is used and the precision with which the Earth's size and shape is to be defined. The actual topographic surface is most apparent with its variety of land forms and water areas. This is, in fact, the surface...

  • Flat Earth
    Flat Earth
    The Flat Earth model is a belief that the Earth's shape is a plane or disk. Most ancient cultures have had conceptions of a flat Earth, including Greece until the classical period, the Bronze Age and Iron Age civilizations of the Near East until the Hellenistic period, India until the Gupta period ...

  • Geographical distance
    Geographical distance
    Geographical distance is the distance measured along the surface of the earth. The formulae in this article calculate distances between points which are defined by geographical coordinates in terms of latitude and longitude.-An abstraction:...

  • Myth of the Flat Earth
    Myth of the Flat Earth
    The myth of the Flat Earth is the modern misconception that the prevailing cosmological view during the Middle Ages saw the Earth as flat, instead of spherical....

  • Physical geodesy
    Physical geodesy
    Physical geodesy is the study of the physical properties of the gravity field of the Earth, the geopotential, with a view to their application in geodesy.-Measurement procedure:...

  • Terra Australis
    Terra Australis
    Terra Australis, Terra Australis Ignota or Terra Australis Incognita was a hypothesized continent appearing on European maps from the 15th to the 18th century...

  • WGS 84

External links