Articles of September 2009

1. Earth also called the Blue Planet came into existence 4.54 billion years ago. Earth is the third planet in the solar system. It is the largest of the terrestrial planets (non-gas planets) in the Solar System in terms of diameter, mass and density. Between approximately 4.1 and 3.8 billion years ago, asteroid impacts during the Late Heavy Bombardment caused significant changes to the surface environment.

2. It is believed life appeared on its surface within a billion years. Since then, Earth's biosphere has radically changed the atmosphere and other abiotic conditions on the planet permitting life on land. It enabled the proliferation of aerobic organisms as well as the formation of the ozone layer which, together with Earth's magnetic field, blocks harmful radiation.

3. It is estimated that world will continue to support life for another 1.5 billion years, after which the rising luminosity of the Sun will eliminate the biosphere. Hence the future of the planet is closely tied to that of the Sun. The Sun, as part of its evolution, will become a red giant. Models predict that the Sun will expand out to about 250 times its present radius, roughly 1 AU (150,000,000 km)

4. The Moon is the earth's only known natural satellite which started revolving around it about 4.53 billion years ago. It helps creates ocean tides, stabilizes the axial tilt and gradually slows the planet's rotation. The Moon revolves with the Earth around a common barycenter every 27.32 days relative to the background stars. When combined with the Earth–Moon system's common revolution around the Sun, the period of the synodic month, from new moon to new moon, is 29.53 days.