Emanation is a theological doctrine which regards individuals as outpourings of the divine essence comparable with the efflux of light from the sun. It denies the personality of both God and man.
Traces of the doctrine are found in the system of Zoroaster. It had a powerful influence on the ancient Egyptian philosophy, as also on that of the Greeks, as may be seen in Pythagoras. It was subsequently developed by Plotinus, the Gnostics, Manicheans, Pantheists, and other sects. Research Emanation
The Harmony of the Spheres was an hypothesis of Pythagoras and his school, according to which the motions of the heavenly bodies produced a music imperceptible by the ears of mortals. He supposed these motions to conform to certain fixed laws, which could be expressed in numbers corresponding to the numbers which give the harmony of sounds. Research Harmony of the Spheres
The Renaissance was that change in the outlook of Europe which took place during the centuries from the fourteenth to the sixteenth. In its broadest sense the Renaissance affected every department of human life. But in its narrower sense it refers to the revival of the learning of ancient Greece, and to the effects of that revival on the arts and literature of modern peoples. The Church in the Middle Ages had taught men to revere authority and to find in her teaching an answer to all the problems of life, whereas the Greeks taught men to inquire and to explore rather than to accept, and to enjoy rather than to suffer. It was this attitude of mind, more than anything else, which shook the medieval world to its foundations. The views of the ancient Greeks, now re-born into the world, were in sharp contrast with the ideals of the Middle Ages. From these ideals many men for a time turned with a feeling of contempt.
The Renaissance was a many-sided movement: it deeply influenced learning and education, art and architecture, science and invention, geography and exploration, and, above all, religion. After the fall of Rome, a knowledge of Greek had rapidly died out in the West and no provision was made for its teaching similar to that made for Latin. In Italy, owing to the closeness of its relations with the East, the number of scholars, monks, and others, who learnt some Greek was greater than elsewhere. It is not, surprising, therefore, that the revival of learning received its main impulse from Italy. From the time of Petrarch and Boccaccio, Italian scholars became more and more devoted to ancient studies, and they began to visit Constantinople, where Greek learning had been preserved. There they hunted out, copied, and eagerly studied the precious manuscripts of the past, and these opened up a new world of thought. Further, from the time that the Turks' crossed from Asia into Europe, some of the Greeks themselves began to travel westwards and to accept well-paid teaching posts in the wealthy Italian cities. And, though the revival began in Italy, the new ideas were rapidly circulated by the new printing presses invented at the time, and every nation in due course played its part in the Renaissance.
The great and wealthy city of Florence was the centre of the Italian Renaissance. Cosimo de Medici, a merchant prince who became ruler of the city, was a patron of the New Learning, and he encouraged Greek scholars to settle in Florence. His grandson, Lorenzo de Medici, known as The Magnificent, loved to gather round him the learned men of the day; he spent 60,000 pounds a year on books; and he caused 200 rare manuscripts to be brought from the East to the Medici library. Rome was second only to Florence as a centre of the New Learning. The Popes themselves became great patrons of learning. Nicholas V founded the Vatican Library. When the son of Lorenzo de Medici became Pope as Leo X, the Renaissance in Rome reached its highest point. Leo made Rome, as he said, ' the capital of the world in literature, as it is in everything else'. He provided a hundred professors for his Greek college in Rome, and he brought his father's library to the Holy City. The library was afterwards restored to Florence by his cousin Clement VII, another member of this remarkable Medici family. The New Learning influenced England from the time of Edward IV, and it made great headway in the reigns of Henry VII and Henry VIII when the scholars known as the Oxford Reformers were flourishing.
The first Englishman to bring Greek manuscripts to England was William Selling. One of his pupils was Thomas Linacre, who went to Florence and shared the instruction given to the young Medici princes; he read in the Vatican Library, and made the acquaintance of Aldo at Venice. Another Oxford teacher who drew his inspiration from Italian sources was William Grocyn, one of the first men to give lectures on Greek literature at his University.
One of Grocyn's pupils was John Colet, who visited Italy in 1496 and returned to lecture on the Gospels in the Greek original at Oxford. He and Sir Thomas More, were friends of Erasmus, a Dutch scholar of international fame. Lady Margaret Beaufort, mother of Henry VII, was herself a patroness of the New Learning. She founded two Cambridge colleges, Christ's and St. John's, and two Lady Margaret Professorships of Divinity, one at Oxford and one at Cambridge. The Revival of Learning was one aspect of the Renaissance; the outburst of artistic energy in the fifteenth and sixteenth centuries was another. The painters of the new period broke away from the conventional art of the Middle Ages and began again to draw from living models. As with the artists, so with the sculptors. Donatello 'went straight with his mighty chisel to original sources - to youth and manhood, and the love of living'. The great figures of that age - Botticelli, Leonardo da Vinci, Michelangelo, Raphael, Titian - still dominate the history of European art. Examples of their works, and of many other Italian artists of the Renaissance, as well as of the Northern artists - Holbein, Durer, and others - are to be seen in the magnificent collection at the National Gallery.
It was natural that men who sought their inspiration from the Greeks should turn with renewed interest to classical architecture. The ruins of ancient Rome provided examples ready to hand; and soon churches planned like classical temples were rising in every city in Italy. St. Peter's, Rome, was designed by Bramante, and the famous dome added by Michelangelo. But great as was the enthusiasm for this architecture Renaissance architecture did not establish itself in England until the end of the reign of Queen Elizabeth I, though Henry VII's tomb at WestminsterAbbey is an example of the Florentine art of the period.
The Renaissance period, filled as it was with a love of experiment, naturally produced a renewed interest in science. With the exception of isolated geniuses like Friar Roger Bacon, there were no medieval scientists worthy of the name. Practically no scientific discoveries had been made for centuries. Modern Science begins its history with the Renaissance and owes a good deal to Leonardo da Vinci. He was the first of a long line of experimenters whose work has continued to the present day. The greatest shock to the medieval notions of the universe was given by Copernicus. For two thousand years mankind with few exceptions had believed that the earth was the centre of the universe, and that the sun revolved round our planet every twenty-four hours. Such had been the teaching of Ptolemy, the Greek scientist. Another Greek, Pythagoras, had questioned it, and advanced the extraordinary notion that the sun, not the earth, was the centre of the universe; but there were few who accepted his theory until Copernicus turned his attention to the 'solar system'. Through slits cut in the walls of his house, Copernicus watched the movements of the planets. Just before he died in 1543 he published a book - 'The Revolutions of the Heavenly Bodies' - giving to the world the results of his observations.
Twenty years later the famous Galileo was born at Pisa, and it was he who perfected the telescope. He lived to popularise the theory of Copernicus, but he was nearly put to death for his pains and was forced by the Court of Inquisition to recant. The Italian Galileo, and the English Newton who discovered the laws of gravity, were the two greatest scientists of the seventeenth century. In the realm of geographical discovery, no age in the world' s history was more momentous than the Age of the Renaissance. Columbus, who discovered America; Vasco De Gama, who found the Cape Route to India; Cabot, Cartier, and Cortez, the discoverers of Newfoundland, Canada, and Mexico; Balboa, who first sailed on the Pacific; Magellan, whose ship was the first to sail round the world - all these and many more make the fifteenth and sixteenth centuries an era without parallel in the annals of discovery.
The new ideas which came surging into the world during the Renaissance acted in many respects as disruptive forces. This was particularly true in the realm of religion. An unquestioning acceptance of authority - i.e. of the teaching of the Catholic Church - was the keynote of the medieval attitude to life, but an eager, inquiring generation began to question this attitude. Men, too, were shocked by the moral decay of the Church and of the Papacy; voices were raised demanding reforms. Some reformers, like Colet and Erasmus, tried to reconcile the new ideas with the Church of Rome and worked to reform it; others, of whom Luther was the greatest, rejected altogether its authority.
The revolution in European history known as the Reformation was an indirect result of the Renaissance - of the New Learning which invited comparison between the present and the past; of the invention of printing which scattered broadcast the new ideas; and again, of the growing idea of the Nation and with it the supremacy of the State. Research Renaissance
Eudoxus was a Greek mathematician and astronomer. He was born at Cnidus, Asia Minor around 400 BC and died in 347 BC. In his early life he attended lectures by Plato and later devised the hypothesis of concentric spheres to explain the stationary points and retrogradations in the motions of the planets. According to Pliny and Strabo it was Eudoxus who first fixed the length of the year at 365.25 days, while Vitruvius ascribes to him the invention of the sundial. He was also a philosopher and was much admired by Marcus Cicero. In mathematics Eudoxus' early success was in the removal of many of the limitations imposed by Pythagoras on the theory of proportion. He also established a test for the equality of two ratios. The model of planetary motion was published in a book called On Rates.
Further astronomical observations were included in two other works, The Mirror and Phaenomena. In a series of geographical books with the overall title of A Tour of the Earth, Eudoxus described the political, historical, and religious customs of the countries of the eastern Mediterranean. He devised the first system to account for the motions of celestial bodies, believing them to be carried around the Earth on sets of spheres. Work attributed to Eudoxus includes methods to calculate the area of a circle and to derive the volume of a pyramid or a cone. Eudoxus probably regarded the celestial spheres as a mathematical device for ease of computation rather than as physically real, but the idea was taken up by Aristotle and became entrenched in astronomical thought until the time of Tycho Brahe. Research Eudoxus
Iamblichus was a neo-Platonic philosopher. He was a native of Chalcis in Coele-Syria, and spent his life in Syria, dieing sometime before 333. He was an ardent student of the philosophy of Plato and Pythagoras and was also versed in the lore of the Chaldaeans and Egyptians. His philosophy was a syncretism of Platonic and Pythagorean doctrines, mixed with Oriental mysticism, his cardinal thesis being that communion with the Deity was possible for man by means of theurgic rites, such as initiations and mysteries. Research Iamblichus
In Greek mythology Abaris was a Scythian priest to the god Apollo. Apollo gave him a golden arrow - known as the dart of Abaris - which rendered him invisible, enabled Abaris to ride through the air, and also cured diseases and gave oracles. Abaris gave the arrow to Pythagoras. Research Abaris
Astronomy is that science which investigates the motions, distances, magnitudes, and various phenomena of the heavenly bodies. That part of the science which gives a description of the motions, figures, periods of revolution, and other phenomena of the heavenly bodies is called descriptive astronomy; that part which teaches how to observe the motions, figures, periodical revolutions, distances, etc, of the heavenly bodies, and how to use the necessary instruments, is called practical astronomy; and that part which explains the causes of their motions, and demonstrates the laws by which those causes operate, is termed physical astronomy. In the 19th century new fields of investigation developed. The first of these - celestial photography - furnished us with invaluable light-pictures of the sun, moon, and other bodies, and recorded the existence of myriads of stars invisible even by the then best telescopes; while the second, spectrumanalysis, revealed a knowledge of the physical constituents of the universe, revealing for the first time for instance that in the sun there exist many of the elements familiar to us on the earth. It has also been applied to the determination of the velocity with which stars are approaching to, or receding from, our system; and to the measurement of movements taking place within the solar atmospheric envelopes. From analysis of some of the unresolved nebulae the inference was drawn that they are not star-swarms but simply cosmical vapour; whence a second inference results favourable to the hypothesis of the gradual condensation of nebulae, and the successive evolutions of suns and systems.
The most remote period to which we can go back in tracing the history of astronomy refers us to a time about 2500 BC, when the Chinese are said to have recorded the simultaneous conjunction of Saturn, Jupiter, Mars, and Mercury with the moon. This remarkable phenomenon is found, by calculating backward, to have taken place 2460 BC Astronomy has also an undoubtedly high antiquity in India. The mean annual motion of Jupiter and Saturn was observed so early as 3062 years BC; tables of the sun, moon, and planets were formed, and eclipses calculated. In the time of Alexander the Great, the Chaldeans or Babylonians had carried on astronomical observations for 1900 years. They regarded comets as bodies travelling in extended orbits, and predicted their return; and there is reason to believe that they were acquainted with the true system of the universe. The priests of Egypt gave astronomy a religious character; but their knowledge of the science is testified to only by their ancient zodiacs and the position of their pyramids with relation to the cardinal points.
It was among the Greeks that astronomy took a more scientific form. Thales of Miletus (born in 639 BC) predicted a solar eclipse, and his successors held opinions which are in many respects wonderfully in accordance with modern ideas. Pythagoras (about 500 BC) promulgated the theory that the sun is the centre of the planetary system. Great progress was made in astronomy under the Ptolemies, and we find Timochares and Aristyllus employed about 300 BC in making useful planetary observations. But Aristarchus of Samos (born in 267 BC) is said, on the authority of Archimedes, to have far surpassed them, by teaching the double motion of the earth around its axis and around the sun. A hundred years later Hipparchus determined more exactly the length of the solar year, the eccentricity of the ecliptic, the precession of the equinoxes, and even undertook a catalogue of the stars. It was in the second century after Christ that Claudius Ptolemy, a famous mathematician of Pelusium in Egypt, propounded the system that bears his name, viz that the earth was the centre of the universe, and that the sun, moon, and planets revolved around it in the following order: nearest to the earth was the sphere of the moon; then followed the spheres of Mercury, Venus, the Sun, Mars, Jupiter, and Saturn; then came the sphere of the fixed stars; these were succeeded by two crystalline spheres and an outer sphere named the primum mobile or first motion, which last was again circumscribed by the coelum empyreum, of a cubic shape, wherein happy souls found their abode.
The Arabs began to make scientific astronomical observations about the middle of the eighth century, and for 400 years they prosecuted the science with assiduity. Ibn-Yunis (around 1000 AD) made important observations of the disturbances and eccentricities of Jupiter and Saturn. In the sixteenth century Nicholas Copernicus, born in 1473, introduced the system that bears his name, and which gives to the sun the central place in the solar system, and shows all the other bodies, the earth included, revolving around him. This arrangement of the universe came at length to be generally received on account of the simplicity it substituted for the complexities and contradictions of the theory of Ptolemy. The observations and calculations of Tycho Brahe, a Danish astronomer, born in 1546, continued over many years, were of the highest value, and claim for him the title of regenerator of practical astronomy. His assistant and pupil, Johann Kepler, born in 1571, was enabled, principally by the aid he received from his master's labours, to arrive at those laws which have made his name famous: 1. That the planets move, not in circular, but in elliptical orbits, of which the sun occupies a focus. 2. That the radiusvector, or imaginary straight line joining the sun and any planet, moves over equal spaces in equal times. 3. That the squares of the times of the revolutions of the planets are as the cubes of their mean distances from the sun, Galileo, who died in 1642, advanced the science by his observations and by the new revelations he made through his telescopes, which established the truth of the Copernican theory.
Isaac Newton, born in 1642, carried physical astronomy suddenly to comparative perfection. Accepting Kepler's laws as a statement of the facts of planetary motion he deduced from them his theory of gravitation. The science was enriched towards the close of the eighteenth century by the discovery by Herschel of the planetUranus and its satellites, the resolution of the Milky Way into myriads of stars, and the unravelling of the mystery of nebulae and of double and triple stars. The splended analytical researches of Lalande, Lagrange, Delambre, and Laplace, mark the same period. The nineteenth century opened with the discovery of the first four minor planets; and the existence of another planet (Neptune) more distant from the sun than Uranus, was, in 1845, simultaneously and independently predicted by Leverrier and Adams. Of later years the sun attracted a number of observers, the spectroscope and photography having been especially fruitful in this field of investigation. From transit observations carried out at the end of the 19th century the former calculated distance of the sun has been corrected, and is now given as 92,560,000 miles. The two satellites of Mars, and of others belonging to Jupiter were also discovered towards the end of the 19th century.
The objects with which astronomy has chiefly to deal are the earth, the sun, the moon, the planets, the fixed stars, comets, nebulae, and meteors. The stellar universe is composed of an unknown host of stars, many millions in number, the most noticeable of which have been formed into groups called constellations. The nebulae are cloud-like patches of light scattered all over the heavens. Some of them have been resolved into star-clusters, but many of them are but masses of incandescent gas. Of the so-called fixed stars, many are now known to be by no means fixed, but revolve in company with another or others. Variable stars and non-luminous stars are also known. The fixed stars preserve, at least to unaided vision, an unalterable relation to each other, because of their vast distance from the earth. Their apparent movement from east to west is the result of the earth's revolution on its axis in twenty-four hours from west to east. The planets have not only an apparent, but also a real and proper motion, since, like our earth, they revolve around the sun in their several orbits and periods.
The mid-20th century saw great leaps in astronomical research with rockets, derived from the German terror weapons of the Second World War, being used to send probes and men into space for closer examination of the heavenly bodies. A retroreflector left on the Moon's surface by Apollo astronauts during the NASAApollo missions returns a high-power laser beam emitted from the Earth, enabling researchers to carry out regular monitoring and measure the distance between the Earth and the Moon to an accuracy of a few centimetres.
We now know something of the planets in our solar system. We know that Mercury is too hot to retain an atmosphere, and that Venus' brilliant white appearance is the result of its being completely enveloped by thick clouds of carbon dioxide. Below the upper clouds Venus has a hostileatmosphere containing clouds of sulphuric acid droplets. The cloud cover shields the planet's surface from direct sunlight, but the energy that does filter through warms the surface, the heat being trapped by the dense clouds, resulting in a very high surface temperature of almost 480 degrees Centigrade. Radar can penetrate the thick Venusian clouds which obscure the surface from telescopes, and has been used to map the planet's surface. Yet, despite advances, the origins of the universe, the stars planets, and the planets' asteroids remains a matter of conjecture, theory and debate. Research Astronomy
In geometry, the hypotenuse or hypothenuse is the longest side in a right-angled triangle, namely that one which subtends or is opposite to the right angle. One of the most important propositions of Euclid's Elements is the forty-seventh of the first book, discovered by Pythagoras, which proves that the square described on the hypotenuse is equal to the sum of the squares described on the other two sides. Research Hypotenuse
Croton or Crotona was an ancient Greek republic in Magna Graecia or South Italy, famous for its athletes, among whom the chief was Milo. It is still more celebrated as the city where Pythagoras taught between 540 and 530 BC.
Abbreviations
Research Emanation
