They say that this is...
However, the hypothesis that our planet is spherical has existed for a very long time. This idea was first expressed in the 6th century BC by the ancient Greek philosopher and mathematician Pythagoras. Another philosopher, Aristotle, who lived in Ancient Greece two centuries later, he gave clear evidence of sphericity: after all, during lunar eclipses, the Earth casts a shadow of exactly a round shape on the Moon!
Gradually, the idea that the Earth is a ball hanging in space and not relying on anything spread more and more widely. Centuries have passed, people have long known that the Earth is not flat and does not rest on whales or elephants ... We went around the world, crossed our ball literally in all directions, flew around it on an airplane, photographed from space. We even know why not only ours, but also all other planets, and the Sun, and the stars, and the Moon, and other large satellites are precisely “round”, and not of any other shape. After all, they are large, have a huge mass. Them own strength gravitation - gravity - tends to give the celestial bodies the shape of a ball.
Even if some force appeared, greater than gravity, which would give the Earth the shape of, say, a suitcase, it would still end in the same way: as soon as the action of this force ceased, the gravitational force would begin to collect the Earth into a ball again, “pulling” protruding parts until all points of the surface are on equal distance from the center.
Let's keep thinking about this...
Not a ball!
Back in the 17th century, the famous physicist and mathematician Newton made a bold assumption that the Earth is not a ball at all, or rather, not quite a ball. Assumed - and mathematically proved it.
Newton "drilled" (of course, mentally!) to the center of the planet two communicating channels: one from the North Pole, the other from the equator, and "filled" them with water. Calculations showed that the water settled at different levels. After all, in a polar well, only gravity acts on water, and in an equatorial well, centrifugal force still opposes it. The scientist argued that in order for both columns of water to exert the same pressure on the center of the Earth, that is, for them to have equal weight, the water level in the equatorial well should have been higher - according to Newton's calculations, by 1/230 of the average radius of the planet. In other words, the distance from the center to the equator is greater than to the pole.
To check Newton's calculations, the Paris Academy of Sciences sent two expeditions in 1735-1737: to Peru and to Lapland. The members of the expedition had to measure the arcs of the meridian - 1 degree each: one - in the equatorial latitudes, in Peru, the other - in the polar latitudes, in Lapland. After processing the expedition data, the leader of the northern one, surveyor Pierre-Louis Maupertuis, announced that Newton was right: the Earth is compressed at the poles! This discovery of Maupertuis was immortalized by Voltaire in ... an epigram:
Envoy of physics, brave sailor,
Overcoming mountains and seas.
Dragging a quadrant in the midst of snow and swamps,
Almost turned into a lopar.
You learned after many losses.
What Newton knew without leaving the door.
In vain Voltaire was so caustic: how can science exist without experimental confirmation of its theories?!
Be that as it may, now we know for sure that the Earth is flattened at the poles (if you like, stretched at the equator). It is stretched, however, quite a bit: the polar radius is 6357 km, and the equatorial one is 6378 km, only 21 km more.
Looks like a pear?
However, is it possible to call the Earth, if not a ball, but an “oblate” ball, namely, an ellipsoid of revolution? After all, as we know, its relief is uneven: there are mountains, there are also depressions. In addition, it is affected by the forces of attraction of other celestial bodies, primarily the Sun and the Moon. Let their influence be small, but still the Moon is capable of bending the shape of the liquid shell of the Earth - the World Ocean - by several meters, creating ebbs and flows. So - in different points radii of "rotation" are different!
In addition, in the north there is a "liquid" ocean, and in the south - a "solid" continent covered with ice - Antarctica. It turns out that the Earth has not quite the correct shape, it resembles a pear, elongated to the North Pole. And by and large, its surface is so complex that it does not lend itself to a strict mathematical description at all. Therefore, scientists have proposed a special name for the shape of the Earth - the geoid. The geoid is an irregular stereometric figure. Its surface approximately coincides with the surface of the World Ocean and continues on the mainland. The same “altitude above sea level”, which is indicated in atlases and dictionaries, is measured precisely from this geoid surface.
Well, scientifically:
Geoid(from other Greek γῆ - Earth and other Greek εἶδος - view, literally - “something like the Earth”) - a convex closed surface coinciding with the surface of water in the seas and oceans in a calm state and perpendicular to the direction of gravity at any point in it. A geometric body that deviates from a figure of revolution An ellipsoid of revolution and reflects the properties of the gravity potential on the Earth (near the earth's surface), an important concept in geodesy.
1. World Ocean
2. Earth ellipsoid
3. Sheer lines
4. Body of the Earth
The geoid is defined as the equipotential surface of the earth's gravity field (level surface), approximately coinciding with the average water level of the World Ocean in an undisturbed state and conditionally continued under the continents. The difference between the real mean sea level and the geoid can reach 1 m.
By definition of an equipotential surface, the surface of the geoid is perpendicular to the plumb line everywhere.
A geoid is not a geoid!
To be completely honest, it is worth admitting that due to the difference in temperature in different parts of the planet and the salinity of the oceans and seas, atmospheric pressure and other factors, the surface of the water surface does not coincide in shape even with the geoid, but has deviations. For example, at the latitude of the Panama Canal, the difference between the levels of the Pacific and Atlantic oceans is 62 cm.
Strong earthquakes also affect the shape of the globe. One such 9-magnitude earthquake occurred on December 26, 2004 in South-East Asia, in Sumatra. University of Milan professors Roberto Sabadini and Giorgio Dalla Via believe that it left a "scar" on the planet's gravitational field, causing the geoid to sag significantly. To test this assumption, the Europeans intend to send a new GOCE satellite into orbit, equipped with modern highly sensitive equipment. We hope that soon he will send us accurate information about the shape of the Earth today.
and a little more interesting about the Earth: for example, when did you find out that the Earth is round? or When the Earth was first photographed from space. But you know, for example, Why are the continents and parts of the world called so? and it was recently reported that
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Original taken from masterok
in
Long-lost continent found at the bottom of the Indian Ocean
In early 2013, geologists found evidence that under the ocean, between Madagascar and India, the submerged remains of an ancient microcontinent are scattered.
The proof was a find in Mauritius - a volcanic island lying about 900 km east of Madagascar. The oldest basalts there are about 8.9 million years old, says geologist Bjorn Jamtveit from the University of Oslo (Norway). But a careful analysis of sand from two local beaches revealed about twenty zircons - zirconium silicate crystals that are highly resistant to erosion and chemical changes. They are much older.
These zircons were formed in granites and other volcanic rocks at least 660 million years ago. One of the crystals is at least 1.97 billion years old.
Mr. Yamtveit and his colleagues suggest that the rocks containing these zircons originated in fragments of ancient continental crust under Mauritius. It seems that relatively recent volcanic eruptions have brought fragments of the crust to the surface, where the zircons have been eroded into the sand.
Researchers also suspect that under the bottom Indian Ocean lies many fragments of that continental crust. An analysis of the Earth's gravitational field has revealed several areas where the oceanic crust is much thicker than usual - 25–30 km instead of the usual 5–10 km.
This anomaly may be the remnants of the land, which scientists propose to call Mauritia (Mauritia). It likely split from Madagascar when tectonic rifting and stretching of the seafloor caused the Indian subcontinent to move from the southern Indian Ocean in a northeasterly direction. The subsequent stretching and thinning of the crust in this area led to the subsidence of fragments of Mauritia, which at that time consisted of an island or archipelago. with total area about three crits.
Scientists chose sand for analysis, not local breeds, to ensure that zircons inadvertently lodged in the crushing equipment from previous examinations did not contaminate fresh samples.
“We found zircon in the sand,” says University of Oslo professor Trond Torsvik, who led the study, “which is normally found in continental crust. Moreover, the zircons we found are very, very ancient.”
The nearest outcrop of continental crust where Mauritian zircons can still be found is deep underwater. In addition, zircons were mined in places in Mauritius where people almost never go and could hardly bring them with them. At the same time, the crystals are too large to be carried there by the wind.
Approximately 85 million years ago, the BBC quoted Professor Torsvik as saying, when India began to separate from Madagascar, the microcontinent broke down and went under water. Only minor remnants of it have survived, for example, the Seychelles.
“We need data of a seismological nature to get information about the geological structure of the rock at the bottom of the ocean,” Professor Torsvik explained.
“Or you can start excavations at the bottom of the ocean, but it will cost enormous money,” he stressed.
Rodinia is a supercontinent believed to have formed about a billion years ago. At that time, the Earth consisted of one giant piece of land and one giant ocean. Rodinia is considered the oldest known supercontinent, but its position and outlines are still the subject of controversy among scientists and experts.
Here is the most common version:
Once upon a time we could (if we lived at that time, of course) walk from Australia to North America. Many creatures living at that time made such transitions more than once. While heavy iron-bearing rocks sank deeper, forming a core over several hundred million years, light stony rocks, rising to the surface, formed a crust. Gravitational contraction and radioactive decay further heated the interior of the Earth. In connection with the increase in temperature from the surface to the center of our planet, foci of tension arose at the boundary with the crust (where the convective rings of mantle matter converge into an upward flow.)
Under the influence of mantle currents, lithospheric plates are in constant motion, hence volcanoes, earthquakes and continental drift arise. The continents are constantly moving relative to each other, but since the rate of their displacement is about 1 centimeter per year, we do not notice this movement. Nevertheless, if we compare the positions of the continents in billions of years, the shifts become tangible. The theory of continental drift was first put forward in 1912 by the German geographer Alfred Wegener, when he noticed that the borders of Africa and South America are similar, like pieces of the same mosaic. Later, after exploring the bottom of the ocean, his theory was confirmed. In addition, it was concluded that the North and South magnetic poles have changed places 16 times over the past 10 million years! Our planet was formed gradually: much that was before disappeared, and now there is something that was absent in the past. Not immediately free oxygen appeared on the planet. Before the Proterozoic, despite the fact that life already existed on the planet, the atmosphere consisted only of carbon dioxide, hydrogen sulfide, methane and ammonia. Scientists have found the oldest deposits, clearly not subjected to oxidation.
For example, river pebbles from pyrite, which reacts well with oxygen. If this did not happen, then there was no oxygen by that time. In addition, 2 billion years ago, there were no potential sources capable of producing oxygen at all. To this day, photosynthetic organisms are the only source of oxygen in the atmosphere. At the beginning of the Earth's history, the oxygen produced by Archean anaerobic microorganisms was almost immediately spent on the oxidation of dissolved compounds, rocks and gases in the atmosphere. Molecular oxygen was almost non-existent; by the way, it was poisonous to most of the organisms that existed at that time. By the beginning of the Paleoproterozoic era, all surface rocks and gases in the atmosphere had already been oxidized, and oxygen remained in the atmosphere for free form, which led to an oxygen catastrophe. Its significance is that it has globally changed the position of communities on the planet.
If earlier most of the Earth was inhabited by anaerobic organisms, that is, those that do not need oxygen and for which it is poisonous, now these organisms have faded into the background. The first place was occupied by those who used to be in the minority: aerobic organisms, which previously existed only in a negligible space of accumulation of free oxygen, were now able to "settle" throughout the planet, with the exception of those small plots where oxygen was scarce. An ozone screen formed over the nitrogen-oxygen atmosphere, and cosmic rays almost stopped penetrating the Earth's surface. This results in a reduction in the greenhouse effect and global change climate. 1.1 billion years ago, there was one giant continent on our planet - Rodinia (from Russian Rodina) and one ocean - Mirovia (from Russian world). This period is called the "Ice World", as it was very cold on our planet at that time. Rodinia is considered the oldest continent on the planet, but there are suggestions that other continents existed before it.
Rodinia broke up 750 million years ago, apparently due to upward heat flows in the Earth's mantle, which blew up parts of the supercontinent, stretching the crust and causing it to break in these places. Although living organisms existed before the break of Rodinia, but only in the Cambrian period did animals begin to appear with a mineral skeleton that came to replace soft bodies. This time is sometimes called the "Cambrian explosion", at the same moment the next supercontinent - Pangea (Greek Πανγαία - all-earth) was formed. Most recently, 150-220 million years ago (and for the Earth this is a very insignificant age), Pangea broke up into Gondwana, "collected" from modern South America, Africa, Antarctica, Australia and the Hindustan island, and Laurasia - the second supercontinent, consisting of Eurasia and North America. After tens of millions of years, Laurasia split into Eurasia and North America which are known to exist to this day. And after another 30 million years, Gondwana split into Antarctica, Africa, South America, Australia and India, which is a subcontinent, that is, it has its own continental plate. The movement of the continents continues to this day.
Presumably, our continents will collide again and form a new supercontinent, which has already been given a name - Pangea Ultima. The term Pangea Ultima and the very theory of the appearance of the mainland were coined by the American geologist Christopher Scotese, who, using various methods movement calculation lithospheric plates, found that the merger could occur somewhere in 200 million years. The last Pangea, as this continent is sometimes called in Russia, will be almost entirely covered with deserts, and in the northwest and southeast there will be huge mountain ranges. .
January 31st, 2014
Like a flat worn coin
The planet rested on three whales.
And they burned smart scientists in bonfires -
The ones that said, "It's not about the whales."
N. Olev
Going out into the street and looking around, anyone can be convinced: the Earth is flat. There are, of course, uplands and depressions, mountains and ravines. But on the whole it is clearly visible: flat, sloping along the edges. The ancients figured this out a long time ago. They saw the caravan disappearing over the horizon. Climbing the mountain, observers noticed that the horizon was expanding. From this followed the inevitable conclusion: the surface of the Earth is a hemisphere. In Thales, the Earth floats like a piece of wood in an endless ocean.
When did these ideas change? In the 19th century, a false thesis was established, which is still being replicated today, that people considered the Earth to be flat before the great geographical discoveries.
So, in the manual for teachers “Lessons on the world around us” in 2007, it says: “For a long time, ancient people considered the Earth to be flat, lying on three whales or three elephants and covered with a dome of the sky ... They laughed at scientists who put forward a hypothesis about the spherical shape of the Earth, they persecuted the church. The navigator Christopher Columbus was the first to believe in this hypothesis... The teacher can tell the children that the first person who saw with his own eyes that the Earth is not flat was cosmonaut Yuri Gagarin.”
In fact, already in the III century BC. the ancient Greek scientist Eratosthenes of Cyrene (c. 276-194 BC) not only firmly knew that the Earth is a ball, but also managed to measure the radius of the Earth, having received a value of 6311 km - with an error of no more than 1 percent!
Around 250 BC, a Greek scholar Eratosthenes first accurately measured the globe. Eratosthenes lived in Egypt in the city of Alexandria. He guessed to compare the height of the Sun (or its angular distance from a point overhead, zenith, which is called - zenith distance) at the same time in two cities - Alexandria (in northern Egypt) and Syene (now Aswan, in southern Egypt). Eratosthenes knew that on the day of the summer solstice (June 22) the Sun was at noon illuminates the bottom of deep wells. Therefore, at this time the Sun is at its zenith. But in Alexandria at this moment the Sun is not at its zenith, but is separated from it by 7.2 °.
Eratosthenes obtained this result by changing the zenith distance of the Sun with the help of his simple goniometric tool - the scaphis. This is just a vertical pole - a gnomon, fixed at the bottom of a bowl (hemisphere). The skafis is installed so that the gnomon assumes a strictly vertical position (directed to the zenith). The pole illuminated by the sun casts a shadow on the inner surface of the skafis divided into degrees.
So at noon on June 22 in Siena, the gnomon does not cast a shadow (the Sun is at its zenith, its zenith distance is 0 °), and in Alexandria, the shadow from the gnomon, as can be seen on the scale of the skafis, marked a division of 7.2 °. At the time of Eratosthenes, the distance from Alexandria to Syene was considered equal to 5000 Greek stadia (about 800 km). Knowing all this, Eratosthenes compared an arc of 7.2 ° with the entire circle of 360 ° degrees, and a distance of 5000 stages with the entire circle. the globe(denoted by the letter X) in kilometers. Then from the proportion it turned out that X = 250,000 stages, or about 40,000 km (imagine this is true!).
If you know that the circumference of a circle is 2πR, where R is the radius of the circle (and π ~ 3.14), knowing the circumference of the globe, it is easy to find its radius (R):
It is remarkable that Eratosthenes was able to measure the Earth very accurately (after all, even today it is believed that the average radius of the Earth 6371 km!).
And a hundred years before him, Aristotle (384-322 BC) gave three classical proofs of the sphericity of the Earth.
Firstly, during lunar eclipses, the edge of the shadow cast by the Earth on the Moon is always an arc of a circle, and the only body capable of giving such a shadow at any position and direction of the light source is a ball.
Secondly, the ships, moving away from the observer into the sea, are not gradually lost from sight due to the long distance, but almost instantly, as it were, “sink”, disappearing below the horizon line.
And, thirdly, some stars can only be seen from certain parts of the Earth, and for other observers they are never visible.
But Aristotle was not the discoverer of the sphericity of the Earth, but only provided irrefutable evidence of a fact that was known even to Pythagoras of Samos (c. 560-480 BC). Pythagoras himself, perhaps, relied on the evidence not of a scientist, but of a simple sailor, Skilacus of Caryanda, who in 515 BC. made a description of his voyages in the Mediterranean.
But what about the church?
There was a decision to condemn the heliocentric system, approved in 1616 by Pope Paul V. But there was no persecution of supporters of the sphericity of the Earth in Christian churches. The fact that "earlier" the church represented the Earth standing on whales or elephants was invented in the 19th century.
By the way, for what they really burned Giordano Bruno.
And yet the church was noted in the question of the shape of the Earth.
Of the 265 people who on September 20, 1519 set off on a trip around the world under the leadership of Magellan, only 18 sailors returned on the last of the ships on September 6, 1522, sick and exhausted. Instead of honors, the team received a public repentance for one lost day as a result of moving through time zones around the Earth in a westerly direction. So Catholic Church punished the heroic team for a mistake in celebrating church dates.
This paradox of round-the-world travel was not recognized in society for a long time. In Jules Verne's novel Around the World in 80 Days, Phileas Fogg almost lost his entire fortune due to ignorance. In the "Science and Life" of the 80s, the conflicts of the teams that returned from the "round the world" are described with the accounting department, which does not want to pay for an extra day of business trip.
Misconceptions and primitive ideas are tenacious not only in the church.
It is probably worth noting one more point, the fact is that the figure of the Earth is different from the ball.
Scientists began to guess about this back in the 18th century, but what the Earth really is - is it compressed at the poles or at the equator - it was difficult to find out. To understand this, the French Academy of Sciences had to equip two expeditions. In 1735, one of them went to carry out astronomical and geodetic work in Peru and did this in the equatorial region of the Earth for about 10 years, while the other, Lapland, worked in 1736–1737 near the Arctic Circle. As a result, it turned out that the length of the arc of one degree of the meridian is not the same at the poles of the Earth and at its equator. The degree of the meridian turned out to be longer at the equator than at high latitudes(111.9 km and 110.6 km). This can only happen if the Earth is compressed at the poles and is not a ball, but a body close in shape to spheroid. At the spheroid polar radius less equatorial(for the terrestrial spheroid, the polar radius is shorter than the equatorial one by almost 21 km).
It is useful to know that the great Isaac Newton (1643-1727) anticipated the results of the expeditions: he correctly concluded that the Earth is compressed, because our planet rotates around its axis. In general, the faster the planet rotates, the greater must be its compression. Therefore, for example, the compression of Jupiter is greater than that of the Earth (Jupiter manages to make a revolution around the axis with respect to the stars in 9 hours and 50 minutes, and the Earth only in 23 hours and 56 minutes).
And further. The true figure of the Earth is very complex and differs not only from a ball, but also from a spheroid. rotation. True, in this case we are talking about the difference not in kilometers, but ... meters! Scientists are engaged in such a thorough refinement of the figure of the Earth to this day, using for this purpose specially carried out observations with artificial satellites Earth. So it is quite possible that someday you will have to take part in solving the problem that Eratosthenes took up a long time ago. This is very what people need a business.
What is the best way to remember the figure of our planet? I think that for now it is enough if you imagine the Earth in the form of a ball with an “additional belt” put on it, a kind of “slap” on the equator region. Such a distortion of the figure of the Earth, turning it from a sphere into a spheroid, has considerable consequences. In particular, due to the attraction of the "additional belt" by the Moon, the earth's axis describes a cone in space in about 26,000 years. This movement of the earth's axis is called precessional. As a result, the role of the North Star, which now belongs to α Ursa Minor, is alternately played by some other stars (for example, α Lyra - Vega will become it in the future). In addition, because of this precessional) movements of the earth's axis Zodiac signs more and more do not coincide with the corresponding constellations. In other words, 2000 years after the era of Ptolemy, the “sign of Cancer”, for example, no longer coincides with the “constellation of Cancer”, etc. However, modern astrologers try not to pay attention to this ...
And where did this stupid idea of \u200b\u200ba flat Earth on three elephants / whales come from?
Nprime Thales believed that the Earth floats in water, like a piece of wood. Anaximander imagined the Earth in the form of a cylinder (at the same time he indicated that its diameter was exactly three times its height), on the upper end of which people live. Anaximenes believed that the Sun and Moon were as flat as the Earth, but corrected Anaximander, pointing out that the Earth, although flat, was not round, but rectangular in plan, and did not float in water, but was supported compressed air. Hecataeus, based on the ideas of Anaximander, compiled geographical map. Anaxagoras and Empedocles did not object to this to the founders, considering such ideas not contrary to physical laws. Leucippus, considering the Earth to be flat, and the atoms falling perpendicular to this plane in one direction, could not understand how then the atoms could connect with each other, forming bodies - and said that no, the atoms in their fall must somehow, deviate even a little. Democritus, in defense of the flat Earth, cited the following argument: if the Earth were a ball, then the sun, setting and rising, would be crossed by the horizon along an arc of a circle, and not in a straight line, as it really is. Epicurus solved the problem of the fall of atoms on the flat Earth, which tormented Leucippus, by attributing to the atoms a free will, by virtue of which they deviate and unite at will.
Obviously, these ancient Greek scientists-atheists-materialists relied on the mythological ideas set forth in poetic language by Homer and Hesiod in the 7th-8th centuries BC. Similar myths about a flat Earth were among the Hindus, Sumerians, Egyptians, and Scandinavians. But I don’t want to go even further there - I’m writing about something completely different. As a curiosity, one can note the book "Christian Topography" by Cosmas Indikoplova, written between 535 and 547, in which the author represents the Earth as a flat rectangle covered with a convex roof of the sky - a kind of casket-chest. This book was immediately criticized by Cosmas's contemporary John the Grammarian (c. 490-570), who then cited the same quotations from the Bible as the justification for the sphericity of the Earth, as I did. The official Church, however, did not interfere in this dispute about the shape of the Earth, it was much more worried about the heretical views of the arguing - Cosmas was a Nestorian, and John was a tritheist and monophysite. Basil the Great disapproved of such disputes, considering their very subject not related to matters of faith.
If you look for elephants / whales, then first of all you can turn to the once popular work of Slavic folk spiritual literature - the Pigeon Book, where there is a verse: "The earth is founded on seven whales." The folk tradition about the Pigeon Book goes back to the “book with seven seals” in the 5th chapter of the Revelation of John the Theologian, and the verse about whales is borrowed from the apocrypha “The Conversation of the Three Hierarchs”. The outstanding collector of Slavic folklore A.N. Afanasyev wrote: “There is a legend among our common people that the world stands on the back of a colossal whale, and when this monster, suppressed by the weight of the earth’s circle, moves its tail, then there is an earthquake. Others argue that from time immemorial, four whales served as a support for the earth, that one of them died, and his death was the cause of the global flood and other upheavals in the universe; when the other three also die, at that time the end of the world will come. An earthquake happens because the whales, after lying on their sides, turn to the other side. They also say that in the beginning there were seven whales; but when the earth became heavy with the sins of men, four went into the depths of Ethiopia, and in the days of Noah all go there. And so there was a general flood.” Some linguists suspect that, in fact, marine animals have nothing to do with it, but we are talking about fixing the Earth along its four edges, since in the Old Slavic language the root “kit” meant “edge”. In this case, we again return to Kosma Indikoplov, whose curious book about a rectangular Earth was very popular in Russia with the common people.
"Flat Earth Societies"
Well, in order to amuse the weary reader in the end, I will point out such a curiosity, but complete insanity, as the existence of the “Flat Earth Society” in our enlightened time. However, the Flat Earth Society existed from 1956 to beginning of XXI centuries and totaled in their better times up to 3,000 members. They considered photographs of the Earth from space fakes, other facts - a conspiracy of the authorities and scientists.
The origins of the Flat Earth Society were the English inventor Samuel Rowbotham (1816-1884), who in the 19th century proved the flat shape of the Earth. His followers founded the Universal Zethetic Society. In the United States, Rowbotham's ideas were adopted by John Alexander Dowie, who founded the Christian Catholic Apostolic Church in 1895. In 1906, Dowie's deputy Wilbur Glenn Voliva became head of the church and championed and promoted a flat earth until his death in 1942. In 1956, Samuel Shenton revived the World Zetetic Society under the name International Flat Earth Society. Charles Johnson succeeded him as president of the society in 1971. During the three decades of Johnson's presidency, the number of supporters of the society increased significantly: from a few members to approximately 3,000 people from different countries. The Society distributed newsletters, leaflets, and similar literature advocating the flat earth model. In the face of its leaders, the society claimed that the landing of a man on the moon was a hoax filmed in Hollywood according to the script of Arthur Clarke or Stanley Kubrick. Charles Johnson died in 2001 and this moment the continued existence of the International Flat Earth Society is in doubt. According to the statements of the supporters of the society, all the governments of the Earth have entered into a world conspiracy to deceive the people. When Samuel Shenton was shown photographs of the Earth from orbit and asked what he thought of them, he replied: "It is easy to see how photographs of this sort can fool the ignorant person."
Even at a time when scientists learned how to clone animals, sent a man into space and learned that gravitational waves oscillate in space and time, there are still people who refute the fact that the Earth is a sphere (albeit a little irregular shape), and continue to claim that it is flat, despite numerous evidence to the contrary (including pictures taken in space).
Fortunately, the ancient Greeks were able to disprove the flat-earth claim long before the advent of satellites and rockets, and it only took common sense, not any technology, to do so. 
The idea of a spherical earth
More than 2,300 years ago, there lived a great thinker named Aristotle, who became best known for his controversy with Plato. Aristotle was not only well versed in politics, poetry, theatre, music, natural sciences and philosophy, but he was also a child prodigy in astronomy. Other ancient Greek thinkers hinted at the idea of a spherical earth in vaguely poetic terms (Plato and Pythagoras among them), but Aristotle was the first to articulate it. 
What is Aristotle's treatise about?
In the treatise "On Heaven", written in 350 BC. e., he explained: “Again, our observations of the stars make it clear not only that the Earth is round, but also that this circle large sizes, because even a slight change in position to the south or north causes a clear change in the horizon. 
“Indeed, in Egypt and in the vicinity of Cyprus, you can see some stars that are not visible in northern regions; and stars that cannot be seen in the north are well distinguished in these regions. All this indicates that the Earth is round in shape, as well as that it is a large sphere. 
Eratosthenes' calculations
So we understand how this idea came about, but we have Eratosthenes to thank for developing this theory. Eratosthenes was a librarian, mathematician, poet, historian, astronomer and "father of geography". 
Around 250 B.C. e. he noted that the wells and pillars in the city of Syene (now Aswan in Egypt) cast no shadow at midday on the summer solstice, as the Sun was directly overhead. But at the same time and on the same day in Alexandria, located about 800 kilometers from Siena, these shadows were long and elongated. 
Eratosthenes knew that the Sun is a massive object, and its rays that hit the Earth must be relatively parallel. So why were the shadows so different? He decided that this would be impossible if the Earth were flat, therefore, it must have a spherical shape. In fact, Eratosthenes was able to figure out that the angle of the sun's rays is approximately 7 degrees, thanks to which he was able to make a surprisingly accurate estimate of the size of our planet.
Needless to say, the rejection of this idea is not something new in modern era celebrities and social networks. The idea of a spherical Earth has been tried to be refuted before, and this was done by both brilliant medieval Islamic scientists and pseudoscientists of the 19th century.
During the life of Columbus, people believed that the Earth was flat. They believed that in Atlantic Ocean huge monsters live, capable of swallowing their ships, and there are terrible waterfalls on which their ships will perish. Columbus had to fight these strange notions to convince people to go sailing with him. He was convinced that the earth was round.
— Emma Miler Bolenius, author of American textbooks, 1919
One of the longest-lived myths children grow up believing in [ author - American - approx.transl.], is that Columbus was the only one of the people of his time who believed that the Earth was round. The rest believed that she was flat. “How brave the navigators of 1492 must have been,” you think, “to go to the end of the world and not be afraid to fall off it!”
Indeed, there are many ancient references to the earth in the form of a disk. And if of all the celestial bodies only the Sun and the Moon were known to you, you could independently come to the same conclusion.
If you go outside at sunset, a day or two after the new moon, you can see something like this.
A thin crescent of the Moon, the illuminated part of which coincides with the part of the sphere that could be illuminated by the Sun.
If you had a scientific mind and curiosity, you could go out on the following days and watch what happens next.
Not only does the moon change position by about 12 degrees every night as it moves further away from the sun, it's getting brighter! You could (fairly) conclude that the Moon revolves around the Earth, and that the change in phases is due to the light from the Sun shining on different parts of the round Moon.
ancient and modern views the phases of the moon coincide in this.
But about twice a year during a full moon, something happens that allows us to determine the shape of the Earth: moon eclipse! During full moon The Earth passes between the Sun and the Moon, and the shadow of the Earth becomes visible on the surface of the Moon.
And if you look at this shadow, it becomes clear that it is bent and has the shape of a disk!
True, it cannot be deduced from this whether the Earth is a flat disk or a round sphere. One can only see that the Earth's shadow is round.
But, despite the popular myth, the question of the shape of the Earth was decided not in the 15th or 16th centuries (when Magellan made a trip around the world), but about 2000 years ago, in ancient world. And what is most surprising, for this it took only the Sun.
If you track the path of the Sun in the daytime sky while living in the northern hemisphere, you will notice that it rises in the eastern part of the sky, rises to a maximum in the south, and then declines and sets in the west. And so on any day of the year.
But the paths throughout the year are slightly different. The sun rises much higher and shines for more hours in summer, and in winter it rises lower and shines less. For illustration, look at the photo of the solar path, taken during the winter solstice in Alaska.
If you plot the path of the Sun across the daytime sky, you will find that the lowest path, and the shortest in time, is at the winter solstice - usually December 21 - and the highest path (and longest) is at the summer solstice, usually 21 June.
If you make a camera capable of photographing the path of the Sun across the sky over the course of a year, you end up with a set of arcs, the tallest and longest being taken on the summer solstice, and the lowest and shortest on the winter solstice.
In the ancient world, the greatest scholars of Egypt, Greece and the entire Mediterranean worked in the Library of Alexandria. One of them was the ancient Greek astronomer Eratosthenes.
While living in Alexandria, Eratosthenes received amazing letters from the city of Siena in Egypt. There, in particular, it was said that on the day of the summer solstice:
The shadow of a man looking into a deep well will cover the reflection of the Sun at noon.
In other words, the Sun will be directly overhead, not deviating a single degree to the south, north, east or west. And if you had a completely vertical object, it wouldn't cast shadows.
But Eratosthenes knew that this was not the case in Alexandria. The sun approaches its highest point at noon during the summer solstice in Alexandria closer than on other days, but vertical objects there also cast a shadow.
And like any good scientist, Eratosthenes set up an experiment. By measuring the length of the shadow cast by a vertical stick on the day of the summer solstice, he was able to measure the angle between the Sun and the vertical direction in Alexandria.
He got one fiftieth of a circle, or 7.2 degrees. But at the same time in Siena, the angle between the Sun and the vertical stick was zero degrees! Why could this happen? Perhaps, thanks to a brilliant insight, Eratosthenes realized that Sun rays can be parallel, but the Earth can be curved!
If then he could find out the distance from Alexandria to Syene, knowing the difference in angles, he could calculate the circumference of the Earth! If Eratosthenes were the supervisor of a graduate student, he would have sent him on his way to measure the distance!
But instead he had to rely on the then known distance between the two cities. And most exact method measurements were...
Camel travel. One can understand the criticism of such accuracy. And yet, he considered the distance between Syene and Alexandria to be 5,000 stadia. The only question is the length of the stage. The answer depends on whether Eratosthenes, a Greek who lived in Egypt, used the Attic or Egyptian stages, which historians are still arguing about. The Attic stadia was used more often and is 185 meters long. Using this value, you can get the circumference of the Earth equal to 46,620 km, which is 16% more than the real value.
But the Egyptian stadia is only 157.5 meters, and perhaps this is what Eratosthenes had in mind. In this case, you get 39,375, which is different from contemporary meaning at 40,041 km by only 2%!
Regardless of the numbers, Eratosthenes became the world's first geographer, invented the concepts of latitude and longitude used to this day, and built the first models and maps based on a spherical Earth.
And although much has been lost over the millennia that have passed since then, the ideas of a spherical Earth and knowledge of its approximate circumference have not disappeared. Today, anyone can repeat the same experiment with two places at the same longitude, and by measuring the lengths of the shadows, get the circumference of the Earth! Not bad, considering that the first direct photographic proof of the Earth's curvature would not come until 1946!
By knowing the shape and size of the Earth, as early as 240 BC, we have been able to figure out a lot of wonderful things, including the size and distance of the Moon! Therefore, we give credit to Eratosthenes for discovering that the Earth is round and for the first accurate calculation of its size!
If there is one thing that Columbus should be remembered for in relation to the size and shape of the Earth, it is for using too small values for its circumference! His estimates of the distances by which he convinced that a ship could pass from Europe directly to India (if the Americas did not exist) were incredibly small! And if there were no Americas, they and the team would die of starvation before reaching Asia!
The sky and stars have long attracted the attention of people. They were observed, admired, and scientists built various hypotheses. And once it was noticed that every star in the sky from time to time changes its position, that is, it moves. This important fact made scientists think that the Earth or the sky somehow move, “rotate”.
Who discovered that the earth revolves around the sun?
- Ancient scientists timidly assumed that the Earth and some other planets revolve around the Sun. Around the second century AD, the scientist Claudius Ptolemy expressed the view that the Earth does not revolve around the Sun. She allegedly remains in place, but the luminary and the sky are mobile. The opinion of the scientist for a long time settled in the minds of the people. By the way, the theory of the scientist about the so-called geocentrism (the central and dominant position of the Earth) echoed the ideas of the famous Aristotle. But let's not completely condemn Ptolemy, because he is one of the few who believed that the planet Earth has the shape of a ball. There were also suggestions that it was not the Earth that revolved around the Sun, but Mercury and Venus.
- As time went. Aristarchus, who lived in the third century AD, spoke about the movement of the Earth relative to the Sun. In the fifth century, the scholar of Aryabhata adhered to the heliocentric theory (as opposed to geocentric), he even gave his arguments. But it has also not been clearly proven that it is the Earth that revolves around the Sun.
- In the Renaissance, bright thoughts were also expressed about the motion of the Earth relative to the Sun (Nicholas of Cusa, Leonardo da Vinci).
However, heliocentrism was firmly established only in the sixteenth century. This happened thanks to the Polish astronomer Nicolaus Copernicus, who proved that the Earth revolves around the Sun. In the middle of the century, he publishes a book where he rejects geocentric theories. Copernicus clearly speaks of the following movements of the planet Earth:
- Movement around its axis (one revolution occurs in one day).
- The movement of the Earth around the Sun (such a revolution lasts exactly one year).
- The motion of the Earth is declinatory (also in one year).
But still, there were flaws in the theory of Nicolaus Copernicus, and it cannot be called with exact certainty heliocentric. The scientist considered the center of the system of planets not the Sun, but the orbit of the Earth. But still, the contribution of Copernicus was very important for the development of further ideas about the solar system.
Development of theory after Copernicus
Interest and attention to the observations and conclusions of Copernicus began to show only towards the end of the sixteenth century. Giordano Bruno became one of the outstanding supporters of the theory of heliocentrism. By the way, he was executed (burned at the stake of the Inquisition) for his views. But where there are supporters of the theory, there are also opponents. Opponents of the Copernican theory argued and refuted. But these arguments were easily demolished by Newton's discoveries of gravity and some others.
Johannes Kepler (Germany) and Galileo Galilei (Italy) were bright followers of heliocentrism. The first clearly established that the center of the planetary system is the Sun. The scientist left a trace in history in the form of laws and tables. Galileo confirmed the theory of Copernicus and refuted the opinions of his opponents. It is known that they wanted to execute the Italian scientist, but Galileo retracted his words. There is a legend that after the words of renunciation, the scientist uttered the famous phrase: “And yet it spins!”
Despite the fact that Copernicus proved that the Earth revolves around the Sun, some scientists continued to insist on their own. There was also a geo-heliocentric theory. According to her, many planets revolved around the Sun, but in the aggregate, all celestial bodies still moved around the Earth. Yet justice and truth prevailed. This happened at the end of the seventeenth century, thanks to the perseverance and inquisitive mind of prominent scientists. Now the Sun has undoubtedly begun to be considered the center of a system of planets. And the system is now called Solar.
It should also be noted that the Earth revolves around the Sun counterclockwise. This manifests itself for us as a change of seasons. That is, our planet makes a complete revolution around the Sun in one year.
The theory that we know and have now was proven with great difficulty. She "suffered" a lot of obstacles because of her religious views. Many scholars who stood firmly for the truth were executed. We can only marvel at their courage and deep love for science.
