Research Results For 'Orbit'

APHELION

The aphelion is the point at which an object travelling around the sun in an elliptical orbit is at its furthest from the sun.
Research Aphelion

APOLLO PROJECT

The Apollo Project was the US space project to land a person on the moon in order to prove to the world the ideological superiority of the American system over that of Communist Russia. It was reportedly achieved by Apollo 11 in July 1969. The three-stage vehicle to carry the astronauts to the moon was code named Saturn, and the contract to develop the Apollo three-man spacecraft was awarded to North American Aviation Incorporated in 1961 by NASA. The first launch into orbit of an Apollo command module was made by Saturn SA-6 on May the 28th 1964, and the first manned flight was made after a fire during ground tests killed the three astronauts - Virgil Grissom, Edward White and Roger Chaffee - on January the 27th 1967.

Controversy surrounds the supposed moon landing, with theories abounding that in 1969 it was technically impossible to land on the moon, and as a result NASA faked the moon landing, filming the 'landing' at the top secret military base, Area 51, in the Nevada desert while the astronauts actually orbited the earth for eight days before returning. This theory was later illustrated in the film 'Capricorn One' which told the fictional story of a faked landing on the planet Mars.
Research Apollo Project

BIELA'S COMET

Biela's Comet was discovered by M. Biela, an Austrian officer, in 1826. Its orbit was calculated at 6 years and 38 weeks and the comet was seen again in 1832, 1839, 1846 and 1852. On the last two sightings it appeared in two distinct parts. It has not been seen since, however in 1872 and 1879 when the earth passed through the comets orbit immense flights of meteors were seen which were connected with the break-up of the comet.
Research Biela's Comet

COMET

Some comets are only visible by the aid of the telescope, while others can be seen by the naked eye. In the latter case they usually appear like stars accompanied with a train of light, sometimes short and sometimes extending over half the sky, mostly single and more or less curved, but sometimes forked. In a comet which appeared in 1744 the train was divided into several branches, spreading out from the head like a fan. The train is not stationary relatively to the head, but is subject to remarkable movements. The direction in which it points is always opposite to the sun, and as the , comet passes its perihelion the train changes its apparent position with extraordinary velocity. The head of the comet is itself of different degrees of luminosity, there being usually a central core, called the nucleus, of greater brilliancy than the surrounding envelope, called the coma.

Comets were long regarded as supernatural objects, and usually as portents of impending calamity. Tycho Brahe was the first who expressed a rational opinion on the subject, coming to the conclusion that the comet of 1577 was a heavenly body at a greater distance from the earth than that of the moon. The general law of the motion of bodies, as well as his own observations on the comet of 1680, led Isaac Newton to conclude that the orbits of the comets must, like those of the planets, be ellipses, having the sun in one focus, but far more eccentric; and having their aphelions, or greater distances from the sun, far remote in the regions of space.

This idea was taken up by Halley, who collated the observations which had been made of all the twenty-four comets of which notice had been taken previous to 1680. The results were very interesting. With but few exceptions the comets had passed within less than the earth's shortest distance from the sun, some of them within less than one-third of it, and the average about one-half. Out of the number, too, nearly two-thirds had had their motions retrograde, or moved in the opposite direction to the planets. While Halley was engaged on these comparisons and deductions the comet of 1682 made its appearance, and he found that there was a wonderful resemblance between it and three other comets that he found recorded - the comets of 1456, of 1531, and of 1607. The times of the appearance of these comets had been at very nearly regular intervals, the average period being between seventy-five and seventy-six years. Their distances from the sun, when in perihelion, or when nearest to that luminary, had been nearly the same, being nearly six-tenths of that of the earth, and not varying more than one-sixtieth from each other.

The inclination of their orbits to that of the earth had also been nearly the same, between 17 degrees and 18 degrees; and their motions had all been retrograde. Putting these facts together, Halley concluded that the comets of 1456, 1531,1607, and 1682 were reappearances of one and the same comet, which revolved in an elliptic orbit round the sun, performing its circuit in a period varying from a little more than seventy-six years to a little less than seventy-five; or having, as far as the observations had been carried, a variation of about fifteen months in the absolute duration of its year, measured according to that of the earth. For this variation in the time of its revolution Halley accounted upon the supposition that the form of its orbit had been altered by the attraction of the remote planets Jupiter and Saturn as it passed near to them; and thence he concluded that the period of its next appearance would be lengthened, but that it would certainly reappear in 1758 or early in 1759. As the time of its expected reappearance approached, Clairaut calculated that it would be retarded 100 days by the attraction of Saturn, and 518 by that of Jupiter, so that it would not come to the perihelion, or point of its orbit nearest the 500 sun, until the 13th of April, 1759.

It actually reached its perihelion on the 13th of March, 1759, being thirty days earlier than he had calculated. Along with the period of this comet and its perihelion distance, the magnitude and form of its path were also calculated. Estimating the mean distance of the earth from the sun at 95,000,000 miles (the number which was at that time considered as the true one), the mean distance of the comet was calculated to be 1,705,250,000 miles; its greatest distance from the sun, 3,355,400,000; its least distance, 55,100,000; and the transverse or largest diameter of its orbit, 3,410,500,000. This comet, therefore, is a body belonging to the solar system, and quite beyond the attraction of any body which does not belong to that system; and as this is determined of one comet, analogy points it out as being the case with them all. In 1835 it again returned, being first seen at Rome, on August the 5th, and from that time continued to be observed until the end of the year in Europe, and through a great part of spring 1836 in the southern hemisphere.

The comet denominated Encke's comet, which has made repeated appearances, was first observed in 1818, and was identified with a comet observed in 1786, also with a comet discovered in 1795 by Miss Herschel in the constellation Cygnus, and with another seen in 1805. Its orbit is an ellipse of comparatively small dimensions, wholly within the orbit of Jupiter; its period is 1260 days, or about three years and three-tenths. It has been frequently observed since.

Another comet, the history of which is of the utmost importance in the latest theories regarding the connection of these bodies and the periodic showers of shooting-stars, is one known as Biela's comet, discovered in 1826. It revolved about the sun in about 6.75 years, and was identified as the same comet which was observed in 1772 and in 1806. Its returns were noted in 1832, 1839, and 1845. In 1846 it divided into two, returned double in 1852, but has not since been seen, the Supposition being that it has been dissipated, and that it was represented by a great shower of meteors that were seen in November 1872. One of the most remarkable comets of recent times was that known as Donati's, discovered by Dr. Donati of Florence in 1858. It was very brilliant in England in the autumn of that year, and on the 18th of October was near coming into collision with Venus, The year 1881 was remarkable for the number of comets recorded. During that year no fewer than seven comets, including the well-known short-period comet Encke's, were observed.
Research Comet

DAY

A day is either the interval of time during which the sun is continuously above the horizon, or the time occupied by a revolution of the earth on its axis, embracing this interval (the period of light) as well as the interval of darkness. The day in the latter sense may be measured in more than one way. If we measure it by the apparent movement of the stars, caused by the rotation of the earth on its axis, we must call day the period between the time when a star is on the meridian and when it again returns to the meridian: this is a sidereal day. It is uniformly equal to 23 hours, 56 minutes, 4.098 seconds. But more important than this is the solar day, or the interval between two passages of the sun across the meridian of any place. The latter is about 4 minutes longer than the former, owing to the revolution of the earth round the sun, and it is not of uniform length, owing to the varying speed at which the earth moves in its orbit and to the obliquity of the ecliptic. For convenience an average of the solar day is taken, and this gives us the mean solar or civil day of 24 hours, the difference between which the actual solar day at any time is the equation of time.

The length of the days and nights at any place varies with the latitude and season of the year, owing to the inclination of the earth's axis. In the first place, the days and nights are equal (twelve hours each) all over the world on the 21st of March and the 21st of September, which dates are called the vernal (spring) and autumnal equinoxes. Again, the days and nights are always of equal length at the equator, which, for this reason, is sometimes called the equinoctial line. With these exceptions, we find the difference between the duration of the day and the night varying more and more as we recede from the equator, and at the poles the year consists of one day of six months' duration, and one night of the same.

The Babylonians began the day at sun-rising; theJews at sun-setting; the Egyptians and Romans at midnight, as do most modern peoples. The civil day in most countries is divided into two portions of twelve hours each. The abbreviations PM. and AM. (the first signifying post meridiem, Latin for afternoon; the latter ante meridiem, forenoon) are requisite, in consequence of this division of the day. The Italians in some places reckon the day from sunset to sunset, and enumerate the hours up to twenty-four; the Chinese divide it into twelve parts of two hours each.

For astronomical purposes the day is divided into twenty-four hours instead of two parts of twelve hours. Formerly it began at noon, but since the 1st of January 1885, the day of twenty-four hours begins at midnight at Greenwich Observatory; and this reckoning is now generally adopted for astronomical purposes elsewhere than at Greenwich. The Greenwich day practically determines the date for all the world. At mid-day at Greenwich the date (day of the week and month) is everywhere the same, though there are all possible differences in naming the hour of the day. But mid-day at Greenwich is the only instant at which we ever have the same date all over the world. The meridian of midnight, which is then at 180 degrees east or west, goes on revolving, gradually bringing a new date to every place to the west of that line, but obviously not bringing that new date to the places immediately to the east of that line until twenty-four hours after. From this it follows that whereas places on the one side of the globe never have a different date except when midnight lies between them, places on the opposite side of the globe, and on different sides of the meridian of 180 degrees east Or west never have the same date except when midnight lies between them. The actual difference of time between Wellington in New Zealand and Honolulu in Hawaii is only about two hours; yet a person at Wellington may date a letter 9 o'clock AM 26th June, while another writing at the same instant at Honolulu dates his 11 o'clock AM 25th June.

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.
Research Eclipse

NEPTUNE

Neptune is the eighth planet from the sun. It has eight satellites, the largest being Triton and Nereid, and a faint planar system of rings or ring fragments. It has a mean distance from the sun of 4497 million km and takes 164.8 years to orbit the sun and 14 hours to rotate.
Research Neptune

TELESTO

Telesto is a small satellite of Saturn. Telesto moves in an almost circular orbit of radius 294,660 km in a period of 1.888 days. Two other Saturnian satellites, Tethys and Calypso, have very similar orbits. Telesto is not spherical but rather ellipsoidal, with a mean diameter of 30 km.
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TETHYS

Tethys is a satellite of Saturn. It was discovered by Giovanni Domenico Cassini in 1684. It has a nearly circular equatorial orbit at 294,660 km from the planet's centre. Its diameter is 1,060 km and its density is 1,200 kg/m3, indicating a predominantly icy composition. All parts of its surface are heavily cratered. Two outstanding topographic features are the giant Odysseus crater, 400 km in diameter, and a trench or large valley, Ithaca Chasma, about 100 km in width and several kilometres deep.
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URANUS

Uranus is one of the outer planets of the solar system. It was discovered on March the 13th, 1781, by Sir William Herschel - and named Georgium Sidus - who also detected, on January the 11th, 1787, two of the Uranian satellites, Oberon and Titania. The mean distance of the planet from the sun is 1,782,000,000 miles, its period of revolution round the sun 84 years, its diameter 31,700 m., and though sixty-four times as big as the earth it is only fifteen times as heavy. Its period of rotation on its own axis is uncertain. Certain markings on its disk caused Brenner in 1896 to deduce a period of 8 hours 27 mins. Other estimates make the period approximately ten hours. Two further satellites have been discovered, Ariel and Umbriel, both by Lassell in 1851. The satellites are remarkable for revolving in a plane nearly at right angles to the orbit of the planet, and for having a retrograde motion. The spectrum of the planet indicates that the atmosphere contains a quantity of free hydrogen, and it is probable that the planet is still at a high temperature. Due to the irregularities in the orbit of Uranus, the remarkable mathematical and consequent telescopic discovery of Neptune was made.
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