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Sound

Sound

Sound is produced by the vibrations of an object or mechanism and transmitted in the form of waves—alternating increase and decrease in pressures. It radiates outward through a material medium of molecules, more or less like the ripples spreading out on water after some he7vy object has been thrown into it. The frequency of sound is determined by the number of times the vibrating waves undulate per second. The Slower the cycle, the lower the pitch.

Alifye - Theory of Space - Sound

Ultra Sonics

The human ear cannot generally hear sounds frequencies higher than 20,000 vibrations per second or 20,000 1-1Z., Sounds of frequencies higher than 20.000 HZ which are inaudible are called ultra – sonic. Bats produce very high sound when they fly they are at ultra – sonic frequencies from 20 000 to 100.000 cannot hear them.

Speed of Sound

The speed of sound varies according to the nature of the carrier media. The speed of sound is around 1088 feet per second. In water, sound travels about 5 times faster than in air. In iron and steel, it is even faster, about 3 times faster than the speed in water.

Speed of sound through some media is:
Ice — cold water        4938 ft per second
Brick                          11960 ft per second
Granite                      1296 ft. per second
Hardwood                 12620 ft. per second
Glass                         16410 to 19690 ft per second

Alifye - Speed of Sound - Super Sonic - Theory of Space

Super - Sonic

Super — sonic speed is greater than the speed of sound i.e 760 miles per hour. This is a unit, worked out by Ernst Mach and therefore named after him. Mach is the ratio of the speed of flight to the speed of sound under the same conditions of pressure and density. When a plane moves at the speed of sound, it is Mach I. When a plane move at twice the speed of sound (supersonic), it is Mach2. When it is less than the speed of sound it is sub — sonic and therefore lesser than Mach I. At half the speed of sound it is Mach '/2.

Sound Barrier

It is the point at which the speed of the flight equals the speed of sound. When a plane flies faster than sound. it is said to cross the sound barrier.

Sonic Booms

When a plane passes the sound barrier, speed produces shock waves in the atmosphere which produce booms like thunder clips. These are called sonic booms. They trouble the ears of the people of the areas over which the aircraft is flying at supersonic speed. But these do not trouble the passengers inside the aircraft because it is flying faster than the shock waves learning them behind.

Decibel

The loudness of the. sound. reflects the pressure of the sound waves. This pressure is expressed in decibels. A decibel may be regarded as the smallest difference between sounds detectable by the human ear. Th. e human ear can safely respond to pressures up to 120 decibels. Any intensity higher than this is painful, and can conceivably damage the delicate nerves of the ear.

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Satellites

Satellites

Alifye - Satellites - Space & Astronomy

Artificial Satellite

It is a man-made object orbiting a planet or the Su the Earth's first artificial satellite, Sputnik 1. was. launched by the USSR on Oct. 4, 1957. The first U.S satellite was Explorer I launched on January 31, 1958. Artificial satellites have also been launched to move round the Moon, Mars, Venus and the Sun.

Communications Satellite  

It is a satellite that relays E.Mail, Fa,x, Internet. telephone, telex and T.V. transmission between ground stations on Earth. The first active communications satellite was Telstar launched in 1962. These satellites eliminate the need for expensive cables or chains of radio relay stations. These are more flexible than long distance can ventional communication links because a satellite can link any two points on Earth that are visible from the satellite. Each communications satellite or comsat) is placed in orbit above Earth's equator at the height of 35680 km. and takes 24 hours to circle the Earth - the same time as is taken by the Earth to spin round its own axis once. Therefore in relation to the Earth it seems stationary and is called synchronous orbit orgeostationary, They receive transmission from ground stations, amplify them and rebroadcast them back to Earth.

Cosmos Satellites

These are a series of Russian unmanned Earth satellite. which were successors to the sputniks. used for scientific tests. The first was launched on March 16, 1962. 

Discoverer Satellites

These were an early series of U.S satellites, launched between 1959 and 1962. These showed that manned spacecraft could safely return from orbit. These satellites were also used to test a prototype of modern rnilitam `spysatellites', which eject capsules containing film for recovery on Earth.

Ecliptic

Ecliptic is the Earth's path round the Sun. On the celestial sphere. the Sun appears to move along the ecliptic during the year, this is the effect of the Earth moving in orbit round the Sun. 

Escape Velocity

Escape Velocity is the speed that an object like rocket. must reach to escape permanently from the body of a planet. The escape velocity from the surface of the Earth is nearly 11 km., per second or 40.000 km, per hour.

Explorer Satellites

Explorer Satellites A series of U.S scientific satellites designed to study the Earth, its surroundings in space, and astronomical objects such as the Sun and Stars. The first Explorer was launched on January 31, 1958.

Satellites

Satellites Natural satellites, also termed moons, are small planets which revolve round the larger once. In the solar system, moons orbit six of the nine known planets.

Skylab

Skylab was a U.S space station in which astronauts set up duration records for living and working in space. The skylab space station was launched in May 1973. Three separate three — men crews boarded the station for periods of up to three months each; fell back to Earth near Australia about two years back. 

Weightlessness

Weightlessness is the condition encountered in space in which the ,astronaut, his craft. and object inside it seem to hang without weight. The term Zero gravity is incorrect because the craft is still within the gravitational pull of the Earth and Sun,

Zodiac 

Zodiac is a band of 12 constellations through which the Sun passes Zodiac do not coincide \Nri th the constellations named after the each .ear- These signs of Zodiac used by the astrologers. 

Pulsars

Pulsars are fast rotating neutron stars. They send out radio Pulsars - gaff frequency, at the remarkably short radio period of 0.033 Waves in re second. 

Quasars

Quasars or Quasi Stellar Radio sources are part star and part radio objects. They combine the characteristics of stars and radio galaxies. Many of the Quasars are radio quiet. These are compact blue objects that emitted radiation strongly in the ultra – violet as well as the radio portion of the spectrum. They exhibit many peculiarities like fluctuating brightness and large red shifts. Quasars are small objects compared to galaxies but all of them emit radiation for in excess of their size or brightness. Some are believed to emit energy which is greater than the combined energy emitted by a hundred galaxies like the Milky way. They fluctuate in brightness at intervals. Since they emit enormous energy, their life times are son. Many of them die out in less than a billion years. All of them are removed from Earth by distances of billions of light years.

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Black Holes

Black Holes:

When a star with a mass more than 20 times that of the Sun explodes as a supernova, it may leave behind a core so massive that even a neutron star is not its final state. The object's gravity may be so great that it goes on collapsing for ever, crushing the matter within it to an unimaginable state. As the object's density gets greater and greater, the force of gravity rises even more until nothing can escape — not even light. The object has become a 'black hole'. At the centre of the black — hole, the remains of the former star would be crushed to infinite density. in zero volume.

Alifye - Space and Astronomy - Black Holes

Black holes are invisible because they emit no light. However, objects can fall into a black hole, when they cross its‘ gravitational boundary. Once inside they can never escape. A black hole twice the Sun's mass makes a gravitational well 13 km. in diameter in space.

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Stars

Stars:

Stars form from gigantic clouds of gas and dust which are scattered throughout the spiral arms of our galaxy and in other galaxies. Many of these clouds appear to be dark. One such dark cloud is the Coal. Sack nebula in the constellation_ of the Southern cross. A cloud starts to form into stars when it becomes dense enough to collapse under the inward pull of its own gravity. As the cloud falls together, it separates into knots and clumps, each of which will eventually form an individual star. These stars — in — the - making are visible as small, dark blocks against the background of brightly glowing nebulae. A typical block known as a globule, is about the diameter of the solar system. At the dense central core of the still shrinking globule is formed the embryo star which is known as a protostar: At first the protostarshines a dul red, releasing heat which is produced by friction as material from the globule cascades down upon its surface. Eventually, the pressure' and temperature at the protostar's centre rise sufficiently for nuclear reaction to begin. These nuclear reactions mark the true birth of, new star. It is estimated that a star of the mass of the Sun takes about 10 million years to pass from the globule stage to the point when nuclear reactions begin.

Alifye - The Solar System - Stars

Since most of the original cloud consists of hydrogen and are made up Largely of hydrogen and helium. At atoms are crushed together to form helium. The conversion of hydrogen to helium releases energy which keeps the star life. Such stars are in the stable prime of their lives. This is the stage that the Sun and most other visible stars have reached today.

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Effects Of Moon On Earth:

Effects Of Moon On Earth:

Eclipses:

The shadows the Earth and Moon throw in space cause total or partial eclipses of the Moon and Sun.

Lunar Eclipse:

Earth revolves round the Sun and the Moon revolves round the Earth, being its satellite. Clearly many a time the Earth comes between the Sun and the full Moon casting a shadow on the Moon. This is called an eclipse of the Moon.

Solar Eclipse:

A solar eclipse can take place when the Moon comes between the Sun and the Earth. It occurs only at new Moon because. Moon's orbit is not in the same plane as that of the Earth.

Tides:

Another effect of the Moon on Earth is caused by Moon's gravity. Invisible fin of gravity from both Sun and Moon draw the Earth's water together into tidal bulges, which surge up and down 'he shore lines everyday. As the Moon is nearer than the Sun it has more than twice the Sun's influence on the Earth's tides.

Spring Tides:

Twice a month, at new and full moon, the tidal pulls of the Moon and Sun coincide because they happen to be in the same line and produce so called spring tides which are about 20% higher than normal.

Neap Tides:

In between the new and full Moon i.e at the Moon's first and last quarter, the Moon and Sun are pulling at right angles. Then the net tidal force is 20% less than average, producing neap tides.

Alifye - The  Moon - Effects of Moon on Earth

Asteroids.  

In addition to the principal planets and their satellites, there are many other bodies which roam about the Sun. These bodies are asteroids, comets and meteoroids. The asteroids are sometimes known as planetoids, small planets which move around the Sun between the large gap of Jupiter and Mars. This gap is about 547 million km. and is known as the asteroid belt. These are thousands of rock — and — metal bodies ranging from hundreds of kms. to a few metres across. They are believed to be debris left over from the formation of the inner planets of the solar system. Their total number may be about 100,000. Among the brightest are Pallas (560 km. across),and Besta (500 km. across). The combined mass of all asteroids is probably about one thousandth. that of the Earth. I hey are too small to retain any atmosphere. and none of them is likely to harbour any form of life. Some asteroids have eccentric orbits that take them well ~ beyond the orbits between Mars and Jupiter. Hidalgo can retreat from the Sun as far as the orbit of Saturn, while Icarus approaches even closer to the Sun than Mercury does.

Alifye - Effects of Moon - Adroids

Comets.   

The word comet is derived from the Latin word "Long —haired". The comets are the tail — stars and are the objects of the solar system. On average about 5 new comets are discovered every year. Most comets are very faint. A comet is a body of gas and dust traveling in an elongated orbit round the Stilt. When far from the Sun. a comet's gases are frozen. It shines only by reflected sunlight, and appears very faint. But as the comet approaches the Sun, its gases warm up and evaporates, releasing material which forms a long, flowing tail. This always points away from the Sun. and may be as lorig as 160 million km. The direction of the tail and its glow are caused by the comet's gases reacting with atomic particles that stream out from the Sun. The brightest of the periodic comets is Halley's which orbits the Sun in 76 years. It will next appear in 2062. Comets are insubstantial bodies. The largest comet is probably less than a millionth of the Earth's weight.

Alifye - Effects Of Moon - Comets

Meteoroids.   

The word meteoroid is a broad one and includes meteors, fireballs, meteorites and micrometeorites. The source of meteorids is not known. Meteors, popularly knosyn as the "shootng stars" are believed to be the debris from comets. These are particles from space which burn up by friction in the Earth's atmosphere. Most meteors are between the size of a grain of sand and that of pea, and as they burn up they appear as bright streaks in the sky. Millions of meteorids pass into our atmosphere but only two or three a day can reach the Earth. Rest are burnt in the atmosphere. These meterods are kTows as meteorites. These are chunks of rock or metal from space large enough to pass though the atmosphere of planet without burning up and to reach its surface. These are believed to be fragments broken off asteroids. Some are big enough to carve a crater when they hit the planets surface e.g. on the Moon. Mars and Mercury.

Alifye - Effects of Moon - Meteoroids

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The Moon

The Moon:

The Moon is the Earth's only natural satellite. Compared to •satellites of other planets, it is very large in relation to its parent planet. It is a quarter of the Earth's diameter measuring 3476 Km. Its distance from the Earth is 384,405 km. It orbits the Earth once a month, keeping the same face turned towards Earth as it does so. Its surface is pitted with craters caused by Meteorites. Moon is the same age as the Earth about 4,600 million years. The moon is a not a self - luminous body. The Earth and Moon travel around a common center of gravity in space.

Alifye - The Solar System - The Moon

The result is that the Earth weaves slightly from side to side in its elliptical path round the Sun with the Moon orbiting it once a month. As the Moon orbits the Earth different amount of its sunlight surface are visible from the Earth. This produces the cycle known as 'Phases of the Moon. We can see the full - Moon and no- Moon once in a month. and for rest of the days it appears in its phases. The average daily delay in Moon - rise and Moon - set is about 50 minutes. The Moon is lacking \eater and it has no atmosphere. A very light 'rain' of cosmic dust continually falls._ the glare of the Sun. lunar rocks reach a temperature of 110 C, More than the boiling point of water. But in shadows the temperature goes down to less than --- l 00 C.

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Pluto

Pluto:  

Diameter at equator--- about 6,000Icm.
Means distance from Sun- 5.900 million km.
Orbits Sun in ---- 247.7 \tars.
Rotates on axis in--- 6 days 9 hours
Number of satellites- 0.
Mass--- 0.1 times that of Earth.
Surface gravity-- not known.

Alifye - The Solar System - Pluto

It is farthest from Sun—the outermost planet. Its distance from the Sun varies widely from the average. At its closest_ it crosses the path of Neptune. making Neptune the outermost planet. It will be closer to the Sun than Neptune between January 1977 and march 1999.

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Neptune

Neptune:

Diameter at equator--- 49500km.
Means distance from Sun- 4496.6 million km.

Orbits Sun in --- 164.8 years.
Rotates on axis in--- 16 hours.
Number of satellites- 2.
Mass--- 17.2 times that of Earth.
Surface gravity---- 1.18 times that of Earth.

Alifye - Solar System - Naptune

It is a large planet lying near the edge of the solar system. Under its cloudy blanket there is believed to be a core of rock sheathed with ice stretching for, about two - thirds its diameter.

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