Rotation and Revolution

Front

Axis Noun

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[ak-sis]

Back

Axis

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An imaginary line extending from the North Pole to the South Pole, around which the Earth rotates.

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Example: This diagram shows the Earth spinning on its axis, an imaginary tilted line. This rotation is what causes the cycle of day and night.

Front

Rotation Noun

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[roh-tey-shuhn]

Back

Rotation

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The spinning motion of a celestial body, such as the Earth, on its own axis, which causes day and night.

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Example: This diagram shows the Earth spinning, or rotating, on an imaginary line called an axis, which is tilted at an angle of 23.45 degrees.

Front

Revolution Noun

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[rev-uh-loo-shuhn]

Back

Revolution

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The movement of one object in an orbit around another object, such as the Earth moving around the Sun.

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Example: This diagram shows the Earth moving in an elliptical path, or orbit, around the Sun, which is the definition of revolution.

Front

Seasons Noun

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[see-zuhns]

Back

Seasons

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The natural divisions of the year based on temperature and daylight, caused by Earth's axial tilt during its revolution.

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Example: This diagram shows that seasons are caused by the tilt of Earth's axis, which stays pointed in the same direction as Earth revolves around the Sun.

Front

Direct Sun's Rays Noun

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[di-rekt suhns reyz]

Back

Direct Sun's Rays

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Sunlight that strikes Earth's surface in a concentrated, direct line, resulting in higher temperatures and more intense energy.

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Example: This diagram shows how the Earth's curve causes sunlight to strike the equator directly, concentrating heat, while hitting higher latitudes at a low angle.

Front

Indirect Sun's Rays Noun

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[in-di-rekt suhns reyz]

Back

Indirect Sun's Rays

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Sunlight that strikes Earth's surface at an angle, spreading energy over a larger area and resulting in lower temperatures.

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Example: This diagram shows that due to Earth's curved surface, sunlight strikes the poles at a low angle, spreading the energy out and making the rays indirect.

Front

Hemisphere Noun

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[hem-i-sfeer]

Back

Hemisphere

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One half of a sphere; Earth is divided into Northern and Southern hemispheres by the equator.

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Example: This diagram shows Earth divided into halves, or hemispheres. The Equator separates the Northern and Southern, and the Prime Meridian separates the Eastern and Western.