(ESTD. BY GOVERNMENT OF TAMILNADU)


Earth


Earth is the third planet from the Sun and the fifth largest:

Orbit : 149,600,000 km (1.00 AU) from Sun
Diameter : 12,756.3 km
mass : 5.972e24 kg


Earth is the only planet whose English name does not derive from Greek/Roman mythology. The name derives from Old English and Germanic. In Roman Mythology, the goddess of the Earth was Tellus - the fertile soil (Greek: Gaia, terra mater - Mother Earth).

It was not until the time of Copernicus (the sixteenth century) that it was understood that the Earth is just another planet.

Earth is the only planet in the solar system known to harbor life. Our planet's rapid spin and molten nickel-iron core give rise to an extensive magnetic field, which, along with the atmosphere, shields us from nearly all of the harmful radiation coming from the Sun and other stars. Earth's atmosphere protects us from meteors, most of which burn up before they can strike the surface.

From our journeys into space, we have learned much about our home planet. The first American satellite, Explorer 1, discovered an intense radiation zone, now called the Van Allen radiation belts. This layer is formed from rapidly moving charged particles that are trapped by the Earth's magnetic field in a doughnut-shaped region surrounding the equator. Other findings from satellites show that our planet's magnetic field is distorted into a tear-drop shape by the solar wind. We also now know that our wispy upper atmosphere, once believed calm and uneventful, seethes with activity -- swelling by day and contracting by night. Affected by changes in solar activity, the upper atmosphere contributes to weather and climate on Earth.

Besides affecting Earth's weather, solar activity gives rise to a dramatic visual phenomenon in our atmosphere. When charged particles from the solar wind become trapped in Earth's magnetic field, they collide with air molecules above our planet's magnetic poles. These air molecules then begin to glow and are known as the auroras or the northern and southern lights.

From the studies We have seen the physical natures of various objects in the solar system, from the Sun to the cometary nuclei residing in the far reaches of our system. We have found that none of them are capable of sustaining life. The only paradise for the living beings is the beautiful blue planet, Earth. The oxygen rich air, optimum warmth, light, sparkling water, the green cover of plants and its varied life forms make this planet a heaven. It is our responsibility to protect our lively home Earth.