Earth.

Earth.

Before the Earth had taken shape, all was vague and amorphous.
It was the great Beginning.
The great Beginning produced Emptiness-the void.
The Universe found shape from the Void.


Earth has a solid surface, abundant waters, and oxygen-rich atmosphere.
All this have combined to create conditions suitable for life.
The Earth is a globe with an equatorial radius of about 4000 miles.
Compared with the other planets of the solar system, it is only of intermediate size and is substantially smaller than the giant planets Jupiter, Saturn, Uranus, and Neptune.

The Earth rotates on its axis.
On account of the rotation of the Earth on its axis that is the entire mass of the globe standing north to south rotates on an axis round the Sun. Therefore we see that
the Sun rises, the Sun sets and we see stars in the horizon in the night. That makes day and night.

At the Equator, the circumference of the Earth is 24000 miles. Therefore the Earth
rotates around its axis at a speed of 1000 miles an hour. This is the speed of rotation at the Equator. It gets smaller as you go up or down the Equator.
For example, at 40 degree latitude north, is 780 miles an hour.

Now this rotating Earth at the same times revolves on its orbit of a grand circular track
taking a round around the Sun. This process of revolution on its orbit round the Sun,
for the Earth it takes a time of 365 days that is how years happen. The Earth revolves
on its orbit round the Sun at a speed of 67000 miles per hour.

Therefore the Earth rotates round its axis and revolves around the Sun on its orbit.
It completes its one round around the Sun on its orbit takes one year.
It completes its round on its axis in a day that is how day and night are formed.

The Earth is bisected at the Equator in two halves. Each half has 90 latitudes.
Each latitude has a distance of 67 miles between each.

The Earth is divided into longitudes with a time difference of four
minutes between each.

The Earth is slanted 23.5 degree east of North Pole at present for 4000 years.
The Earth will be straight at North Pole for next span of 4000 years.
The Earth will again slant 23.5 degree west of North Pole thereafter.


This cycle continues every 4000 years.
The land area- between East Africa and western India remains cut and ocean
takes over the land in the present span of 4000 years.
In the next span East Africa and Western India gets linked by land as ocean moves away. Atlantis country will reappear on West Europe, Atlantic Ocean in next 4000 years span.
Presently it is submerged into Atlantic Ocean due to slanting earth.





The Moon is a complimentary in the process of Earth motions. Earth and the Moon raise tides in the bodies of one another, resulting in the dissipation of energy into heat, which in turn leads to the slowing of the Earth's spin velocity on its axis and the recession of the Moon.

The outstanding feature of the Earth as a planet is the presence of liquid water. Water is vital not only for the biosphere but also for the geologic processes of erosion, transport, and deposition that shape the Earth's surface. Yet, if the Earth were closer to the Sun, the water would be vaporized; if farther, it would turn to ice.

Two-thirds of the terrestrial surface is covered by oceans. It was long thought that the continents, constituting the remaining one-third of the surface, had been fixed in position throughout the Earth's history. Gradually some Earth scientists dared to suggest that there had been major continental displacements, and finally, during the 1960s, investigators developed the full picture of seafloor spreading and plate tectonics. The continents, though constantly in motion, are in fact the oldest portions of the Earth's surface, for the seafloor is created at ridges and consumed at trenches on a geologically short time scale.

That the Earth has a magnetic field has been known at least since the 11th century when the directional properties of suspended magnetic rock were first used for navigation. Over the centuries the characteristics of this changing field have become better understood, until it now appears that the only plausible cause is some system of motions in the Earth's liquid outer core. These motions, which may be thermally driven like the slow convection currents in the mantle, constitute an electromagnetic dynamo whose electric currents sustain the field. Many problems remain: Why, for example, should the field have reversed polarity at irregular intervals through geologic time? But again, the existence of the field is in all likelihood simply further evidence of the Earth's dynamic structure.



Some other planets, notably Jupiter and Mercury, are known to have magnetic fields. It is interesting that Jupiter and Mercury differ appreciably in density and therefore composition, but both planets must have the internal motions necessary to constitute a dynamo. The Moon probably once had a magnetic field, but its internal dynamo apparently ceased long ago as the fluid interior froze.


The Earth's magnetic field shields the planet from the most direct effects of the ionized gas that constitutes the solar wind, carving out a cavity known as the magnetosphere. The existence of the magnetosphere has in all likelihood played a fundamental role in determining the nature of the Earth's atmosphere and its climate and therefore in the development of life. Yet, the verification of the magnetosphere's existence is a fairly recent accomplishment.


Earth is the third planet outward from the Sun. Its single most outstanding feature is that its near-surface environments are the only places in the universe known to harbour life.

Humans for the first time saw the Earth as a complete globe in December 1968 when Apollo 8 carried astronauts around the Moon. In December 1990 the Galileo spacecraft, outfitted with an array of remote-sensing instruments, studied the Earth during the first of its two gravity-assisted flybys en route to the planet Jupiter. The information about the Earth gathered from Galileo was meagre compared with that obtained by the swarm of artificial satellites that have orbited the globe throughout the space age, but it provided some unique portraits of the Earth as a planet. Viewed from another planet, the Earth would appear bright and bluish in colour. Most readily apparent would be its atmospheric features, chiefly the swirling white cloud patterns of mid-latitude and tropical storms, ranged in roughly latitudinal belts around the planet. The Polar Regions also would appear a brilliant white owing to the clouds above and the snow and ice below. Beneath the changing patterns of clouds are the much darker, blue-black oceans, interrupted by occasional tawny patches of desert lands. The green landscapes that harbour most human life would not be easily seen from space; not only do they constitute a modest fraction of the land area, which itself is a small fraction of the Earth's surface, but they are often obscured by clouds. Over the course of the seasons, some seasonal changes in the storm patterns and cloud belts on Earth would be observed. Also prominent would be the growth and recession of the winter snowcap across land areas of the Northern Hemisphere.

The planet orbits the Sun in a path that is presently more nearly a circle than are the orbits of most other planets. The direction of the Earth's revolution—counter clockwise as viewed down from the north--is in the same sense (direction) as the rotation of the Sun; the Earth's spin, or rotation about its axis, is also in the same "direct" sense. The length of a day (23 hours, 56 minutes, and 4 seconds) is typical of other planetary objects. Jupiter and most asteroids have days less than half as long, while Mercury and Venus have days more nearly comparable with their orbital periods. The slant (inclination) of the Earth's axis to its orbit (23.5), also typical, is responsible for the change of seasons. Compared with the other eight planets of the solar system, the Earth is relatively small. Although it is the largest of the inner planets, it is considerably smaller than the gas giants of the outer solar system. The Earth has a single satellite, the Moon. The Moon is one of the bigger natural satellites in the solar system and is in fact relatively large compared with the Earth itself. Some people consider the Earth-Moon system a double planet, with some similarities to the Pluto-Charon system.

The Earth's gravitational field is manifested as the attractive force acting upon a free body at rest, causing it to accelerate in the general direction of the centre of the planet. Departures from the spherical shape and the effect of planetary rotation cause gravity to vary with latitude over the terrestrial surface. Gravity typically is not measured at sea level, so corrections must be made for its decrease in value with increasing elevation. Such height-related gravity anomalies may be corrected for by using free-air or Bouguer reductions. In the Bouguer reduction, the effect of the attraction of the additional mass located above sea level is taken into account, while in the free-air reduction this mass effect is ignored. The Bouguer anomaly can be used to indicate variations of density within the Earth by measuring the corresponding variation in gravity.

The Earth's gravity keeps the Moon in its orbit around the planet and also generates tides in the body of the Moon. Such deformations are manifested in the form of slight bulges at the lunar surface, detectable only by sensitive instruments. The Moon, owing to its relatively large mass, exerts a gravitational force that likewise causes tides on the Earth. These are most readily observable as the daily rises and falls of the ocean water, although tidal deformations occur in the solid Earth as well as in its atmosphere.

In short, our Earth has solid surface, abundant waters, and oxygen-rich atmosphere have combined to create conditions suitable for life. The Earth is a nearly spherical body with an equatorial radius of slightly more than 4000 miles. Compared with the other planets of the solar system, it is only of intermediate size and is substantially smaller than the giant planets Jupiter, Saturn, Uranus, and Neptune. This fact has been of great importance in determining the history of the Earth's rotation, for the Earth and the Moon raise tides in the bodies of one another, resulting in the dissipation of energy into heat, which in turn leads to the slowing of the Earth's spin velocity on its axis and the recession of the Moon. In fact, if the present rates of slowing and recession are linearly extrapolated backward in time, the Moon is found to have been impossibly close to the Earth at a time within the geologic record--a seemingly unexplainable paradox. Only very recently has it been shown that the present distribution of continents and oceans produces an anomalously high rate of slowing, and so the Moon need never have been extremely close to the Earth.

The outstanding feature of the Earth as a planet is the presence of liquid water. Water is vital not only for the biosphere but also for the geologic processes of erosion, transport, and deposition that shape the Earth's surface. Yet, if the Earth were closer to the Sun, the water would be vaporized; if farther, it would turn to ice. Two-thirds of the terrestrial surface is covered by oceans. It was long thought that the continents, constituting the remaining one-third of the surface, had been fixed in position throughout the Earth's history. Gradually some Earth scientists dared to suggest that there had been major continental displacements, and finally, during the 1960s, investigators developed the full picture of seafloor spreading and plate tectonics. The continents, though constantly in motion, are in fact the oldest portions of the Earth's surface, for the seafloor is created at ridges and consumed at trenches on a geologically short time scale. Other planets, notably Mars and Venus, have surface features that suggest some elements of plate tectonics, but none is known to be undergoing the constant rejuvenation of the surface as is the Earth.


The fundamental laws of geologic succession, of the differences between igneous rocks and sedimentary rocks began to be understood toward the end of the 18th century.
At about the same time the measurement of the constant in Newton's law of gravitation showed that the specific gravity of the Earth was about 5.5, whereas that of a typical crustal rock was only about 2.7. Obviously, the interior must be much denser, and it became apparent that pressure alone could not explain the difference. Instead, there have to be differences in chemical composition, involving a decrease with depth of the light elements abundant in the crust (oxygen, silicon, and aluminum) and an increase of heavier elements such as iron. With reference again to the other planets of the solar system, it is seen that their densities tend to fall into two groups: the inner planets with densities close to that of the Earth, and the giant planets with appreciably lower densities. The members of the first group probably have iron cores (proposed for the Earth in the early years of the 20th century), while those of the second must contain large amounts of very light elements such as hydrogen.

If the Earth were completely static, it would be virtually impossible to obtain information about the interior apart from the mean density. Dynamism is, however, the mark of the Earth: tectonic plates move, probably driven by slow convection currents within the Earth's mantle; earthquakes occur; and, from the study of earthquake waves, the broad outlines of the interior can be established. The resulting picture of the Earth includes a solid inner core, a fluid outer core whose radius is more than half the planet's radius, a predominantly solid mantle, and a chemically distinct thin crust that contains most of the familiar geologic features. The rigid plates that are driven over the surface consist of the crust and some uppermost mantle, which together make up a mechanically distinct regime called the lithosphere.