The Earth was formed nearly 4.7 billion years ago. The Earth’s shape is Geoid, not perfectly spherical. The Earth’s equatorial diameter is about 12,756 km, which is a bit larger than the polar diameter; about 12,714 km Surface Area of the Earth is 510,065,600 km sq of which 148,939,100 km2 (29.2 %) is land and 361,126,400 km2 (70.8 %) is water.

The Earth rotates on its axis, an imaginary straight line through its centre. The two points where the axis of rotation intersects the Earth’s surface are called as the poles, one of them is called the North Pole and the other is known as the South Pole. One rotation with respect to Sun is completed in 24 hours, known as a solar day.

The Earth rotates in counter-clock direction or from left to right-or eastward direction. Rotation serves three reasons. First, the axis of rotation serves as a reference in setting up the geographic grid of latitude and longitude. Second, it provided a good measure of the passage of time, 24 hours or 1440 minutes or 86,400 seconds a day. Third, it greatly influenced the physical and life processes on Earth.