THE EARTH-OUR HOME

From the perspective we get on Earth, our planet appears to be big and sturdy with an endless ocean of air. From space, astronauts often get the impression that the Earth is small with a thin, fragile layer of atmosphere. For a space traveler, the distinguishing Earth features are the blue waters, brown and green land masses and white clouds set against a black background.

Many dream of traveling in space and viewing the wonders of the universe. In reality all of us are space travelers. Our spaceship is the planet Earth, traveling at the speed of 108,000 kilometers (67,000 miles) an hour.

Earth is the 3rd planet from the Sun at a distance of about 150 million kilometers (93.2 million miles). It takes 365.256 days for the Earth to travel around the Sun and 23.9345 hours for the Earth rotate a complete revolution. It has a diameter of 12,756 kilometers (7,973 miles), only a few hundred kilometers larger than that of Venus. Our atmosphere is composed of 78 percent nitrogen, 21 percent oxygen and 1 percent other constituents.

Earth is the only planet in the solar system known to harbor life. For a long time, our scientists thought other planets supported life but, with modern telescopes such as the Hubbel, we have found that no other planet in our system has an atmosphere or water to support the kind of life we call biological.

Earth Statistics

Equatorial radius (km) ............................. 6,378.14

Mean distance from the Sun (km) ................. 149,600,000

Rotational period (days) ............................ 0.99727

Rotational period (hours) ........................... 23.9345

Orbital period (days) ............................... 365.256

Atmospheric composition Nitrogen ............................................ 77% Oxygen .............................................. 21% Other ................................................ 2%

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