Research Results For 'Eclipse'

ALGOL

Algol is a star in the constellation of Perseus. It was catalogued by Ptolemy as the Lucida of the Gorgon. It is the model 'eclipse star' varying in brightness over a two day period through the interpositions of a revolving dark satellite. The light-changes of Algol were noticed by Montanari in 1669 and methodically observed and explained by Goodricke in 1783.
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ECLIPSE

An eclipse is the interception or obscuration of the light of the sun, moon or other heavenly body by the intervention of another and non-luminous heavenly body. Stars and planets may suffer eclipse, but the principal eclipses are those of the sun and the moon.

An Eclipse of the Moon is an obscuration of the light of the moon occasioned by an interposition of the earth between the sun and the moon; consequently, all eclipses of the moon happen at full moon; for it is only when the moon is on that side of the earth which is turned away from the sun, and directly opposite, that it can come within the earth's shadow. Further, the moon must at that time be in the same plane as the earth's shadow; that is, the plane of the ecliptic in which the latter always moves. But as the moon's orbit makes an angle of more than 5 degrees with the plane of the ecliptic, it frequently happens that though the moon is in opposition it does not come within the shadow of the earth.

An Eclipse of the Sun is an occultation of the whole or part of the face of the sun occasioned by an interposition of the moon between the earth and the sun; thus all eclipses of the sun happen at the time of new moon. As the earth is not always at the same distance from the moon, and as the moon is a comparatively small body, if an eclipse should happen when the earth is so far from the moon that the moon's shadow falls short of the earth, a spectator situated on the earth in a direct line between the centres of the sun and moon, would see a ring of light round the dark body of the moon; such an eclipse is called annular; when this happens there can be no total eclipse anywhere, because the moon's umbra does not reach the earth. An eclipse can never be annular longer than 12 minutes 24 seconds, nor total longer than 7 minutes 58 seconds; nor can the entire duration of an eclipse of the sun ever exceed 2 hours.

An eclipse of the sun begins on the western side of his disc and ends on the eastern; and an eclipse of the moon begins on the eastern side of her disc and ends on the western. The average number of eclipses in a year is four, two of the sun and two of the moon; and as the sun and moon are as long below the horizon of any particular place as they are above it, the average number of visible eclipses in a year is two, one of the sun and one of the moon.
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DIXON'S MILK SNAKE

The Dixon's Milk Snake (Lampropeltis triangulum dixoni) is an American species of Milk snake first described in 1983 and named after J R Dixon. The Dixon's Milk Snake has very broad black rings which almost eclipse the red in places, interspersed by bands of very pale yellow. The head and snout are black in colour, and the nape pale yellow.
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ALBERT EINSTEIN

Albert Einstein was a German Swiss mathematical physicist. He was born in 1879, and died 1955. His first job was in a patent office in Berne, where, finding the work undemanding, he turned his attention to problems in theoretical physics and in 1905 successfully used the quantum theory to explain the photoelectric effect, for which he received the Nobel Prize for Physics in 1921. In 1905 he also published a paper on molecular motion, and a paper in which he put forward the special theory of relativity, describing the effects of motion on observed values of length, mass, and time. One consequence of his theory is that mass, m, is equivalent to energy, E, a concept expressed by the equation E = mc2, where c is the speed of light. This equation is the basis of all calculations of the energy released by nuclear reactions. He extended his ideas in the general theory of relativity which was published in 1915, and which is concerned with gravitation and the effects of accelerated motion.

The first independent verification of general relativity was obtained in 1919 when the bending of light was observed during an eclipse. Einstein also made important contributions to quantum mechanics. However, he was unable to accept as final the probabilistic description of physics which quantum theory involved. In 1913 he returned to his native Germany to take up a professorship at the University of Berlin, but as a Jew he experienced Nazi persecution, and in 1932 was forced to leave the country. After a brief stay in Britain he settled in the USA, and eventually became an American citizen.
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ANGELO SECCHI

Angelo Secchi was an Italian astronomer. He was born in 1818 at Reggio in the Emilia and died in 1878. He entered the Jesuit order in 1833 and was driven into exile by the revolution of 1848, to find refuge in Washington. On his return he was appointed director of the Roman College Observatory by Pius IX. He made an extensive series of double-star observations and successfully photographed the total eclipse of the sun in Spain in 1860. In 1863 he established the present system of classifying stellar spectra, which he completed by the discovery of carbon stars in 1867.
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CAPTAIN JAMES COOK

Captain James Cook was an English sailor and explorer. He was born in 1728 and died in 1779, killed by the natives of Hawaii. The son of Yorkshire peasants, he was apprenticed to a shopkeeper, but acquiring a love of the sea became a sailor, joining the Royal Navy in 1755 and in 1759 becoming the sailing-master of the ship 'Mercury' which surveyed the St Lawrence River and the coast of Newfoundland.

Some observations on a solar eclipse, communicated to the Royal Society, brought him into notice, and he was appointed commander of a scientific expedition to the Pacific, with the rank of lieutenant in the navy. During this expedition he successively visited Tahiti, New Zealand, discovered New South Wales, and returned by the Cape of Good Hope to Britain in 1771. In 1772 Captain Cook, now raised to the rank of a commander in the navy, commanded a second expedition to the Pacific and Southern Oceans, which resulted like the former in many interesting observations and discoveries. He returned to Britain in 1774.

Two years later he again set out on an expedition to ascertain the possibility of a north-west passage. On this voyage he explored the western coast of North America, and discovered the Sandwich Islands, on one of which, Hawaii, he was killed by the natives, on February the 14th, 1779. Captain Cook wrote and published a complete account of his second voyage of discovery, and an unfinished one of the third voyage, afterwards completed and published by Captain James King.
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EDWIN DUNKIN

Edwin Dunkin was an English astronomer. He was born in 1821 and died in 1898. He was educated at private schools, and in 1838 joined the staff of the Royal Observatory at Greenwich. He became chief assistant in 1881, but resigned the post three years later. During his period of service he represented the astronomer-royal in many important expeditions, being sent to Christiania in 1851 to observe the total eclipse of that year, and having charge of the pendulum experiments undertaken in 1854 near South Shields to determine the mean density of the earth. He was president of the Royal Astronomical Society from 1884 to 1886. Among his published works are: On the Movement of the Solar System in Space determined from the Proper Motions of 1167 Stars (1863); On the Probable Error of Transit Observations (1860-64); The Midnight Sky: Familiar Notes on the Stars and Planets (1869); Obituary Notices of Astronomers (1879); and many papers in scientific journals.
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THALES OF MILETUS

Thales of Miletus was the earliest of the Greek scientists. He was born in 624 BC and died in 565 BC. He created a sensation by predicting an eclipse of the sun which was visible at Miletus in 585 BC. He looked upon water as the basis of all material things and in his mathematical works was the first to enunciate natural laws.
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BROWNING A-BOLT II ECLIPSE VARMINT

The Browning A-bolt II Eclipse Varmint is an American bolt-action sporting and hunting rifle produced in blued steel with a laminated hardwood stock with a thumb hole. The Browning A-bolt II Eclipse Varmint is produced in .308 Winchester, .22-250 Remington and .223 Remington calibres and takes a 4- or 6-round magazine depending upon calibre. The Browning A-bolt II Eclipse Varmint has a 26 inch barrel fitted with the Boss system to regulate vibration and improve accuracy, no sights are fitted but instead a mounting for a telescopic sight.
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ASTRONOMY

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, spectrum analysis, 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 radius vector, 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 planet Uranus 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 NASA Apollo 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 hostile atmosphere 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.
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