Introduction
Our planet, Earth, is 4.5 to 4.6 billion years old.
Being the third planet from the Sun and the fifth largest planet in this
universe, it has a diameter of 12,756.3km and a mass of 5.972 x 1024
kg.
The orbit of earth around the sun is 149,600,000 km (1.00 AU). It makes a
revolution around the sun in 365 days and a rotation on its axis in 24hrs.
Atmosphere
The Earth's atmosphere is made up of 77% nitrogen, 21% oxygen, with traces of argon, carbon dioxide and water.Clouds formed by water droplets envelope the planet.
Terrain
Compared to other planets, the terrain of Earth is relatively flat. The Omlpus Mons on Mars is 3 times taller than the highest mountain (Mount Everest) on Earth.
Moons
Earth has only one natural satellite, the Moon. But thousands of small artificial satellites have also been placed in orbit around the Earth. The orbit of the Moon about Earth is 384km and the mass is 17387.35 x 1022kg.
Special Feature
71% of the Earth's surface is covered with water and it
is the only planet on which water can exist in liquid form on the surface
(though there may be liquid ethane or methane on Titan's surface and liquid
water beneath the surface of Europa).
The heat capacity of the oceans is very important in keeping the Earth's
temperature relatively stable. Liquid water is also responsible for most of the
erosion and weathering of the Earth's continents, a process unique in the solar
system today.