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22.2 The Earth-Moon-Sun System

22.2 The Earth-Moon-Sun System. Learning Objectives :. Describe the movements of Earth known as rotation, revolution, and precession. Explain how the moon goes through phases. Explain how eclipses occur . 22.2 The Earth-Moon-Sun System. California State Standards:.

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22.2 The Earth-Moon-Sun System

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  1. 22.2 The Earth-Moon-Sun System Learning Objectives: • Describe the movements of Earth known as rotation, revolution, and precession. • Explain how the moon goes through phases. • Explain how eclipses occur.

  2. 22.2 The Earth-Moon-Sun System California State Standards: • Astronomy and planetary exploration reveal the solar system’s structure, scale, and change over time.

  3. Motions of Earth Rotation What is … Rotation ? The turning, or spinning, of a body on its axis. What are the . . . 2 measurements for rotation: 1. Mean solar day is the time interval from one noon to the next, about 24 hours. 2. Sidereal dayis the time it takes for Earth to make one complete rotation (360º) with respect to a star other than the sun—23 hours, 56 minutes, 4 seconds.

  4. Motions of Earth Revolution What is … Revolution ? The motion of a body, such as a planet or moon, along a path around some point in space. What is … Perihelion? The time in January when Earth is closest to the sun. What is … Aphelion? The time in July when Earth is farthest from the sun.

  5. Motions of Earth Precession What is . . . Precession ? traces out a cone over a period of 26,000 years.

  6. Motions of Earth Earth’s Axis and Seasons The plane of the ecliptic is an imaginary plane that connects Earth’s orbit with the celestial sphere. Because of the inclination of Earth’s axis to the plane of the ecliptic, Earth has its yearly cycle of seasons.

  7. Motions of the Earth-Moon System Earth–Sun Motion The solar system speeds in the direction of the star Vega. The sun revolves around the galaxy. Earth is presently approaching one of its nearest galactic neighbors, the Great Galaxy in Andromeda. What is …Perigee? The point at which the moon is closest to Earth. What is …Apogee ? The point at which the moon is farthest from Earth.

  8. Phases of the Moon The phases of the moon are the progression of changes in the moon’s appearance during the month. Lunar phases are a result of the motion of the moon and the sunlight that is reflected from its surface.

  9. Lunar Motions The synodic month - based on the cycle of the moon’s phases. It lasts 29 1/2 days. The sidereal month - true period of the moon’s revolution around Earth. It lasts 27 1/3 days. The difference of two days between the synodic and sidereal cycles is due to the Earth–moon system also moving in an orbit around the sun. The moon’s period of rotation about its axis and its revolution around Earth are the same, 27 1/3 days. It causes the same lunar hemisphere to always face Earth.

  10. Lunar Motions

  11. Eclipses Solar eclipses occur when the moon moves in a line directly between Earth and the sun, casting a shadow on Earth.

  12. Eclipses Lunar eclipses occur when the moon passes through Earth’s shadow. During a new-moon or full-moon phase, the moon’s orbit must cross the plane of the ecliptic for an eclipse to take place.

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