Seasons and Earth's Tilt

Front

Rotation Noun

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[roh-tey-shuhn]

Back

Rotation

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The spinning motion of an object on its own internal axis, which for Earth causes the cycle of day and night.

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Example: This diagram shows the Earth spinning on its tilted axis, which is called rotation. Sunlight illuminates one side (day) while the other is in shadow (night).

Front

Revolution Noun

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[rev-uh-loo-shuhn]

Back

Revolution

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The motion of one celestial body as it travels in an orbit around another, such as Earth's yearly journey around the Sun.

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Example: This diagram shows Earth's year-long journey, or revolution, around the Sun. This orbit, combined with the planet's constant tilt, causes the changing seasons.

Front

Orbit Noun

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[awr-bit]

Back

Orbit

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The specific, curved path that a celestial object follows as it revolves around another object due to gravitational attraction.

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Example: The Earth travels in an elliptical path, its orbit, around the Sun, getting closer at perihelion and farther away at aphelion.

Front

Axis Noun

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[ak-sis]

Back

Axis

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An imaginary line passing through the center of a celestial body, around which the object rotates or spins.

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Example: This diagram shows the Earth's axis, the imaginary line it rotates on. The axis is shown tilted at 23.4 degrees, which is the cause of the seasons.

Front

Tilt Noun

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[tilt]

Back

Tilt

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The inclination of a planet's rotational axis relative to its orbital plane, which is the primary cause of seasons.

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Example: This diagram shows the Earth's axis is tilted, causing sunlight to hit different parts of the planet more directly or indirectly, which explains why we have seasons.

Front

Hemisphere Noun

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[hem-i-sfeer]

Back

Hemisphere

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One half of a sphere, used to describe the division of Earth into Northern and Southern halves by the equator.

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Example: The Earth is divided by the Equator (0° latitude) into the Northern Hemisphere and the Southern Hemisphere, which experience opposite seasons due to Earth's tilt.

Front

Equator Noun

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[i-kwey-ter]

Back

Equator

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An imaginary line drawn around the middle of a planet, dividing it into the Northern and Southern hemispheres.

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Example: This diagram shows the Earth with the Equator, an imaginary line circling its middle, dividing it into the Northern and Southern Hemispheres.

Front

Direct Sunlight Noun

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[di-rekt suhn-lahyt]

Back

Direct Sunlight

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Solar radiation that strikes a planet's surface at a high angle, concentrating energy and resulting in warmer temperatures.

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Example: This diagram shows the sun's path across the sky in different seasons. The higher path in summer results in more direct sunlight and shorter shadows.

Front

Indirect Sunlight Noun

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[in-di-rekt suhn-lahyt]

Back

Indirect Sunlight

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Solar radiation that strikes a planet's surface at a low angle, spreading energy over a larger area and causing cooler temperatures.

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Example: This image shows that indirect light is sunlight that does not travel in a straight path from the sun to an object, such as light in a room away from a window.

Front

Seasons Noun

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[see-zuhns]

Back

Seasons

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Distinct periods of the year caused by a planet's axial tilt, characterized by specific weather patterns and daylight hours.

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Example: This diagram shows that as the Earth orbits the Sun, its constant tilt causes different hemispheres to receive more direct sunlight, resulting in seasons.