Earth is one of the planets in the solar system. It has air, water and a temperature that is neither too cold nor too hot for living things. These are the things that enable us to live on Earth. Earth, like other bodies in space, is moving at all time. Earth moves very fast, but we do not feel that it is moving at all. How does Earth move? How do we know that it really moves?
Spin a top. Observe it turn about its nail. The nail is the axis of the spinning top. An axis is a straight lineabout which a body spins or rotates. A top that is spinning very fast seems to be not moving at all. You may not be aware of it, but Earth is spinning very fast. Earth has an axis which is not vertical to the plane of the movement of planets around the sun, it is slightly tilted. The spinning of Earth about its axis is called rotation . All things on the planets surface rotate with it, but they do not fall off into space because Earth's gravity pulls them toward Earth.
When we wake up in the morning, we see the sun as it rises above the horizon in the east. Then, it appears to gradually move upward. At noontime, the sun reaches its highest point. After this, it gradually goes lower until it hides behind the horizon in the west. The sun may appear to be moving across the sky in an east to west direction, but actually it is the rotation of Earth that makes it appear so. The sun appears to move from east to west because Earth is rotating in the opposite direction - west to east.
Scientist says that the diameter of Earth isabout 12, 700 kilometers . To complete one rotation, earth must have traveled from one end of the diameter to the same end. We cannot feel earth rotating, but the rising and setting of the sun tell us that Earth is turning on its axis. There are twelve hours between sunrise and sunset. This period is daytime . There are twelve hours between sunset and the next sunrise. This period is nighttime . The time between one sunrise and the next sunrise is 24 hours, or one day. It takes Earth 24 hours or one day to make one complete rotation.
As Earth rotates on its axis, it also turns on its path or orbit around the sun. Earth's movement around the sun is called revolution . Just as Earth rotates from west to east, it also revolves around the sun from west to east. The distance that Earth travels around the sun is more than 950 million kilometers . It travels with a speed of about 107,000 kilometers per hour . At this rate, it takes 365 ¼ days to complete one revolution. This is called a natural year . Our calendar is based on a year of 365 days. This is ¼ day less than a natural year. However, every four years a day is added to the month of February so the number of days becomes 366. A year with 366 day is a leap year . This is a year in which February has 29 days instead of 28.
note: originally posted at Exposeknowledge.com under the same author.
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