The Moon Earth’s Satellite
Origin of the Moon • Three early Theories: • Moon was a space object captured by Earth’s gravity. • Material around the Earth condenses to form the moon. • Earth ejected moltenmaterial that became the moon.
The Impact Theory • Current Theory • Based on data gathered by the Apollo missions • The moon formed from condensing gas and debris thrown off when Earth collided with a Mars sized object.
Rotation • The moon rotates on its axis. • Click the word rotation to see an animated view. Rotation
An axis is an imaginary line that passes through the moon from top to bottom. Axis
Rotation is spinning around an axis. • 1 Rotation = 27.3 days
Why can’t we see the Moon rotate? • The Moon rotates around its axis every 27.3 days. The Moon revolves around the Earth every 29.5 days. Because the two motions take about the same amount of time, the same side of the Moon always faces Earth.
Why does the Moon Shine? • The moon appears to shine because it reflects sunlight. The moon does not produce any light, it only reflectslight.
Phases of the Moon • Moon phases are different forms that the Moon takes in its appearance from Earth. • The phase depends on the relative positions of the Moon, Earth and the Sun.
New Moon • A New Moon occurs when the Moon is between the Earth and the Sun. The lighted half of the Moon is facing the Sun and the far side faces Earth. The Moon is in the sky, but it cannot be seen. The new moon rises and sets with the Sun. What we see
Waxing Phase • Waxing means that the portion of the Moon that we can see appears to be growing.
Full Moon • A full Moon occurs when all of the Moon’s surface facing Earth reflects light. What we see
Waning Phase • Waning means that the portion of the Moon that we can see appears to be shrinking.
Crescent and Gibbous Moons • Gibbous • Crescent
Third or Last Quarter First Quarter
Lunar Cycle • One Lunar Cycle lasts about 29.5 days.