Bài 14: Earth Rotation and Revolution

Lesson 14: Earth Rotation and Revolution

     The term Earth rotation refers to the spinning of our planet on its axis. Because of rotation, the Earth's surface moves at the equator at a speed of about 467 m per second or slightly over 1675 km per hour. If you could look down at the Earth's North Pole from space you would notice that the direction of rotation is counter-clockwise (Figure 1). The opposite is true if the Earth is viewed from the South Pole. One rotation takes exactly twenty-four hours and is called a mean solar day. The Earth’s rotation is responsible for the daily cycles of day and night. At any one moment in time, one half of the Earth is in sunlight, while the other half is in darkness. The edge dividing the daylight from night is called the circle of illumination. The Earth’s rotation also creates the apparent movement of the Sun across the horizon.

Figure 1: The movement of the Earth about its axis is known as rotation. The direction of this movement varies with the viewer’s position. From the North Pole the rotation appears to move in a counter-clockwise fashion. Looking down at the South Pole the Earth’s rotation appears clockwise.


Rotation (n): the act or process of moving or turning around a central point
     • the rotation of the Earth around its axis
     • the rotation of the Moon around the Earth
Revolution (n): a : the action of moving around something in a path that is similar to a circle (rotation)
     • (count noun): the revolution of the Earth around the Sun
     • (noncount noun): The period of revolution of the Earth around the Sun is equal to one year.

Term (n): a word or phrase that has an exact meaning
     • That's an outdated term that no one uses anymore.
     • scientific/technical terms (thuật ngữ khoa học/ kỹ thuật)
     • remote sensing is a scientific term
Terms (n/ pl): the particular kinds of words used to describe someone or something
     • He spoke about them in glowing terms.
     • The law had been understood in broad terms.
     • in economic terms (các điều khoản kinh tế)
Spin (v.) to turn or cause someone or something to turn around repeatedly
     • The Earth spins [=rotates] on its axis once a day

Notes on grammar

Spinning: When we use a verb in -ing form more like a noun, it is usually a gerund. Like a verb, a gerund can also have an object itself. In this fire, the whole expression [gerund + object] can be the subject, object or complement of the sentence.

The :
 definite article. "The" is used many times in this lesson
     Used in different ways, students must read in grammar book to understand how to use.

     Used to refer to things that occur in nature
     + The planets revolve around the sun.
     Used to refer in a general way to a specific type of activity
     + the law
     + the arts and sciences
     + the publishing industry

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