The motion of the Earth around the Sun and the effect of this in respect of temporal orientation - Essay Example

The motion of the Earth around the Sun and the effect of this in respect of temporal orientation “Eppur si muove…” [yet it is moving] were the last words of Galilei’s, the renowned mathematician from the University of Padova. However, he was not the first to state the Earth is moving around the Sun. Aristarkhos, an ancient Greek mathematician, represented also a heliocentric view of the Universe. We owe a lot to Galileo Galilei, Tycho de Brahe, Johannes Kepler and Isaac Newton for the acceptance of heliocentric concept. Galilei made this theory widely known. Tycho Brache’s observations of the planetary movements and Kepler’s works on the same subject contrasted with geocentric theory held by the majority of scientists and the Church of that time. Newton’s gravitation principle supported the heliocentric viewpoint by clear and unambiguous explanations and offered a useful tool for making very precise predictions. The heliocentric concept proposed by Copernicus is often referred to as “Copernicus’ revolution.” In the 18th and 19th century scientists discovered the Sun to be only one star among from an infinitesimal number of stars and in the 20th century it revealed that Milky Way is only one galaxy among the myriads of similar galaxies. Nowadays Einstein’s theory of relativity is universally accepted. Relying on the equivalence principle, it has become unnecessary to determine the centre of the Cosmos. In other words, one can elect either the Sun or the Earth to be the centre (or reference point) of the solar system. All we know, everything is in motion in the Universe. The Earth is spinning around its axis and moves on an orbit around the Sun. These motions cause the alternation of days and nights and that of seasons. Observing from the Earth it appears as if the Sun were moving in the sky, following a regular path on the celestial heaven. We call Ecliptic the apparent way the Sun makes in a year in the sky. More precisely, it is the intersection of the celestial sphere with the ecliptic plane. The ecliptic plane contains the Earth’s mean orbital plane in the solar system. Except for two, most planets in the solar system are moving almost on the same plane, therefore these planets appear from the Earth always close to the Ecliptic. The two exceptions are Mercury and Pluto whose orbital planes deviate from the ecliptic plane by 7° and 17°, resp. The Equator of the Earth does not align with the ecliptic plane, but makes an angle of approx. 23,27°. This causes the alternation of seasons, because a particular area gets different amount of sunshine during the annual movement of the Earth. At first it seems reasonable, seasons differ from one another because the Earth’s distance from the Sun is always different. When the Earth is closest to the Sun, it is five million kilometres closer (perihelion) than on its farthest point (aphelion) from the Sun. Each year we are in the farthest distance from the Sun on July 3, and in the nearest distance on January 3. That is, the Sun is the farthest from us in summer and the closest to us in winter. Consequently, we cannot explain the occurrence of seasons by our planet’s distance from the Sun. The reason for this is the axial tilt, in other words, the inclination of the angle made between the Earth’s rotational axis and its orbital plane. The alternation of seasons is caused by the fact that the axial tilt and the direction to which the axis points remain invariable all over the year. North Pole constantly points to Polaris in Ursa Minor. If we turn to Polaris at any points of the Northern Hemisphere, we invariably turn to the North. Seasons come about in the following way: On March 22, each year the Sun is above exactly the Equator. This is one of the two days when both daylight and nightlight last for twelve hours all over the world and on the Northern Hemisphere it is vernal equinox. Although the North Pole still points to Polaris, it is shifting towards the Sun during the three months that follow the equinox. In the first quarter of the year the Sun is rising higher and higher each day. Therefore the days get longer and the nights shorter in spring as long as on June 22, the North Pole points to the Sun. It does not face the Sun, however, only makes a 66,5° angle with it. On the Northern celestial sphere the Sun rises at its highest peak on this day. We call it summer solstice. From then on the North Pole is gradually moving away from the Sun. On the Northern Hemisphere days will be shorter and shorter as we are approaching autumnal equinox. In the next six months following autumnal equinox the Sun will rise higher and higher on the Southern Hemisphere and moves low on the Northern Hemisphere. Here it sinks to its lowest point on December 22. This is winter solstice. Winter starts on this day in the North and summer begins in the South. If the Axis tilt were exactly perpendicular to the orbital plane of the Earth (i.e. the inclination angle were 0), the Sun would hang above the Equator on each day of the year. It would be a constant equinox, that is, the days and nights would equally last for twelve hours. At noon the Sun would be at the same height and it would radiate the same amount of heat every day. It does not mean the temperature would be similar everywhere on the earth. It means the temperature would not change on a particular area. It would be the hottest on the Equator and the coldest on the two Poles. Changes in the weather would not be so significant as they are today. ------- BIBLIOGRAPHY: Fred Hoyle: From Stonehenge to modern cosmology, 1972 (Hungarian translation 1978) Neil F. Comins: What if the Moon didn’t exist?, 1994 (Hungarian translation 1994) Wikipedia: Ecliptic, Hungarian version Wikipedia: Axial tilt, Hungarian version History of Physics, edited by Péter Török (in the Hungarian language) The Beginnings of Civilization When contemplating the history of human civilization, we have to raise the question: what is civilization? Does it mean high culture or does it simply refer to some craftsmen’s art and skill in doing something? Is it some groups of people who organise their society on high standard? Does it mean doing something in a more sophisticated way than the rest of creatures do on the Earth? We could hardly answer these questions in simple terms. To seek the best reply, we had better consult an encyclopaedia. According to Webster’s New Collegiate Dictionary [G. & C. Merriam Co., 1977] civilization is: “a relatively high level of cultural and technological development”. More specifically, it is “the stage of cultural development at which writing and the keeping of written records is attained”. Some other source describes civilization as “an established or developed stage of human society”. True, but it is too general to construe this definition. While some definitions highlight the differences, e.g. writing, some others lay emphasis on the common features. The most common feature of various civilizations is their complexity. Every society has accumulated enough knowledge and experiences to be widely used throughout the whole society. “Civilization means the very productive interaction between people, where cultural potentials and certain sources are accumulated in significant extents.” [John M. Roberts: Before history: The first civilisations”] “The history of civilisation starts at around 3500 BC., with the first well traceable civilisation in Mesopotamia.” – says Mr. Roberts. His view is supported by The Times History of the World [Reader’s Digest, Hungarian translation 2002]. Around 6000 years ago more complex societies emerged in place of the sporadic settlements of the Neolithic age. The first urban civilizations were born starting a new page in the history of mankind. These settlements developed on four different parts of the world: in the river valleys of the Tigris and the Euphrates, the Nile and the Indus as well as in the valley of the river Yang-tze. Their common characteristic was that these settlements developed into megalopolises offering a model for sophisticated organisations of the society. These megalopolises extended their authorities also to the countryside. Certain division of labour, some written language and the class of educated people (usually clergymen) developed in these cities. Huge public buildings, temples and fortresses were erected and kings descending from gods were acknowledged. The simultaneous existence of civilized and barbarous groups was already apparent. Wondering nomad people meant a continuous threat to their settled fellow-beings who lived on higher city standards. Due to the improvement of irrigation, the alimentation of dense urban populations became feasible. At the same time, intricate administrations were installed to regulate city life. Wealth grew parallel with urban development, commerce expanded leading to the appearance of the first empires. The Mesopotamian civilization of Sumer is generally recognised to be the world’s first civilisation. The first megalopolises were established in Mesopotamia in the second half of the 4th millenary, BC. In Uruk, Ur, Tell Ukair and Susa huge, richly ornamented buildings were erected approx. in 3500 years B.C. Supposedly writing started in Uruk at that time. Ancient Egypt 3200 – 343 BC is one of the world’s three oldest civilizations. By starting using the flood of the Nile for irrigation, a civilisation prevailing for more than 25 centuries emerged. Despite its history of unifying and splitting up the empire during those centuries, the language, religion and culture of the Egyptian civilization shows such a continuity which is second to none in the ancient Middle-East. In around 1600 BC the fertile regions of Middle-East became a battle field of kingdoms rivalling with one another. In the 12th century, Assyria was ruling the region until Babylon conquered it. Babylon was brought to heel by the Persians. The geographical and climatic conditions favoured for human beings to settle on the territory of Chine. The first traces of human habitats are more than half a million years old. The first Chinese civilization appeared in the Bronze Age, i.e. around 1600 BC. This civilization worked out its own writing, philosophy, and a solid structure of society and economy. India gives room for one of the most ancient civilizations of the world, which was born in the Indus Valley. Harappan and then the Vedic culture served as a basis for the Hindu society, their religion, Hinduism as well as Buddhism and Jainism. The first Greek Bronze Age started in around 3000 BC. On the island of Crete the traces of the first Aegean civilization remote back to approx. 2600 BC. Aegean is the general term for prehistoric civilizations in Greece. The name of Troy, Mycenae and Cnossus had been renown from the oeuvres of Homer but we did not know that they had been closer to the cultures of Asia Minor than those of Greece until H. Schliemann and Sir Arthur Evans excavated the ruins of these cities at the end of the 19th century. The Greek civilization was spread along with the conquest of Persia by Alexander the Great in the 4th century AD around the Mediterranean-sea. Ancient Rome stemmed from an Etruscan city-state approx. in the 9th century BC that got incorporated in the Roman Republic. During its 12-century existence, Rome shifted from a monarchy to an oligarchic republic and to an empire. It conquered Western-Europe and the territories surrounding the Mediterranean-sea. The Roman Empire assumed Christianity in the 4th century. The West-Roman Empire perished in 476 AD in the Western part of the Mediterranean-sea. We call Western civilization the one spread in Western- and Central-Europe starting from Christian, Latin-speaking part of the Roman Empire. The western half of the empire broke into independent kingdoms in the 5th century AD, while the eastern - Byzantine Empire - came to rule after 476 AD, the date for the “fall of Rome”. [Wikipedia: Civilizáció; Wikipedia: Civilisation] Prehistoric Cave Art of Lascaux in France and Altamira in Spain The most interesting and most mysterious relics left to us by the human beings who lived in the Age of Upper Palaeolithic are by all means their artefacts. The oldest certified findings are 35000 thousand years old. After this date the findings came to light in abundance and then suddenly conscious art was born almost with no precedents and at a surprisingly high technical and artistic level. As it emerged, this art disappeared all of a sudden – with no precedent. However, the bases of visual arts applied here have survived and are still in use. Cave art in Africa is 27000 years old and the one in Australia is at least 20000 years old. The art of the Palaeolithic is not limited to Europe, but the best known ones are from here. In the Valley of Ardèche (France) 300 pictures of animals are painted or carved on the walls of Chauvet Cave. Radio-carbon tests prove that these pictures are more than 30000 years old, thus they are the oldest paintings discovered up till now. The majority of artefacts from this early age were found in the South-West of France and in the North of Spain. They are ranked in three groups: small stone, bone or clay-stone figurines (mainly female figures); ornamented objects (often tools and weapons); and cave paintings on the walls and ceiling. The majority of the figures decorating cave walls or weapons represent some animals. It is evident, that these beautifully portrayed animals took an important part in the lives of people at that time. There is great probability that the paintings and drawings in the French caves follow a well-conceived order. Obviously the art of the Age of Upper-Palaeolithic had similar functions as writing has today, but probably we will not be able to understand their proper meaning. Probably they were attached to some religious rituals or witching practices. The fact that the European paintings can be found in the darkest and most remote parts of the caves implies that they were made or watched in the frame of some unusual rites. The first Palaeolithic cave paintings were found in Altamira Cave, Spain in 1879. Probably the 12 thousand-year old bulls were painted as part of some ritual. In Europe more than 200 caves are known at present where Palaeolithic paintings are available. The majority of paintings originate from the Magdalenian Period, i.e.15000 – 10000 BC and 90% of them are in France and Spain. The most beautiful paintings showing cows, horses and bulls decorate the Cave of Lascaux in the valley of Dordogne. The Cave of Lascaux is one of the most remarkable caves including pictures from the Prehistoric Age. The paintings and carvings remote back to the Magdalenian Period, i.e. they are approximately 15000 – 17000 years old. Rock paintings in Lascaux witness the complete mastery of graphis arts used even today: engraving, sculpture, painting and drawing. The materials used for colouring are in powder form or in little blocks. Some of which show signs of scraping. Lascaux Cave is one of the painted caves in the Valley of Vézère, France. The caves are declared a World Heritage Site by UNESCO. Lascaux Cave was discovered in 1940. Some years later the cave was opened to the public. By 1955 the paintings showed the signs of perishing therefore attempts were made to preserve their state. In 1963 the cave was closed to public in order to prevent further deteriorations. Lascaux II is a replica of two of the cave halls - the Great Hall of the Bulls and the Painted Gallery. Rooms in the cave include The Great Hall of the Bulls, the Lateral Passage, the Shaft of the Dead Man, the Chamber of Engravings, the Painted Gallery, and the Chamber of Felines. The cave was not used for human habitation; it was rather a sanctuary where Palaeolithic people visit only on special occasions. The Cave of Altamira includes one of the most beautiful paintings of prehistoric times. Altamira Cave is located in Cantabria, Spain. It is famous for its drawings and polychrome paintings of buffalos, mammoths, wide boars, a large doe and human hands. For a long time these painted were supposed to be faked pictures. Artefacts for Upper Solutrean (approx. 18500 years ago) and Lower Magdalenean (between 16500 – 14000 years ago) were found in the cave floor in abundance. Around 13000 years ago a rockfall shut off the cave entrance preventing the paintings from early deterioration. The cave was not habitated by human beings, only the entrance was used where natural daylight lit the mouth of the cave. Similarly to Lascaux, paintings can be found along the walls of the cave, even in the dark and remote corners. The artists used charcole and ochre or heamatite to paint pictures. They often scratched or diluted these dyes to interpret alternations in dark and light shades. They also exploited the natural contours in the walls to create three dimensional effect to their pictures. Altamira Cave is declared a World Heritage Site by UNESCO. ----- Bibliography: [John M. Roberts: Before history: The first civilisations”] The Times History of the World [Reader’s Digest, Hungarian translation 2002]. Wikipedia: Lascaux (both in English & Hungarian) Wikipedia: Altamira (both in English & Hungarian) Read More