1. Chapter 25 Earth’s Moon

2. 25.1 Origin & Properties of the Moon 4 theories of origin: 1) Earth and moon formed simultaneously 2) Fission: Earth spun so fast that a chunk spun off into orbit 3) Capture: moon formed elsewhere and was caught by Earth’s gravity

3. Origin of the Moon 4) Impact Theory – planet sized object collided with Earth and debris settled into orbit, pulled together and formed the moon ** This is the currently accepted theory!

5. Features of the Moon Maria: large, dark areas formed from early lava flowsMaria: large, dark areas formed from early lava flows Terrae (highlands): older, lighter areas of the moon with more cratersTerrae (highlands): older, lighter areas of the moon with more craters Impact Craters: formed from meteoritesImpact Craters: formed from meteorites –Weathered and eroded by micrometeorites –No atmosphere!

6. 25.2 The moon’s motions Orbits the Earth in 27 1/3 daysOrbits the Earth in 27 1/3 days Orbit shape is ellipticalOrbit shape is elliptical Perigee=nearest to EarthPerigee=nearest to Earth Apogee=farthest from EarthApogee=farthest from Earth We see the same side of the moon because the Moon’s orbit around Earth takes just as long as one rotation on its axis!We see the same side of the moon because the Moon’s orbit around Earth takes just as long as one rotation on its axis! –Orbital period = rotational period

7. Moon’s Phases http://www.youtube.com/watch?v=AQRNzepe4wI

8. Lunar Eclipse Moon enters Earth’s shadowMoon enters Earth’s shadow –Can only occur at a full moon phase –Umbra=total shadow –Penumbra=partial shadow Moon appears orangeMoon appears orange

9. Solar Eclipse Occurs when moon comes between the sun and EarthOccurs when moon comes between the sun and Earth Occurs only at the new moon phaseOccurs only at the new moon phase Total time = 7.5 minTotal time = 7.5 min Moon is dark, but sun’s corona is visible around the moon making a gold ringMoon is dark, but sun’s corona is visible around the moon making a gold ring