Earth, Moon, and Sun: Phases and Motion

1. Unit 9: Earth, Sun, & Moon Phases

2. moon • The ________ is Earth’s only natural satellite. It is also Earth’s closest neighbor in space.

3. gravitational, inertia 2. Moons orbit planets for the same reason that planets orbit the Sun--because of ________ attraction and ______.

4. tides 3. The Moon’s gravitational force causes Earth’s ______, the regular rise and fall of water levels along the shore.

5. revolution, 365 1/4 4. Earth is moving at 30 km/s (19mi/s) as it orbits the Sun. A __________________________ is a complete pass around the Sun, taking ___________________ days, or one year.

6. axis, rotation 5. Earth is also spinning on the ________ at about 1600 km/h (1000 mph). One _______ is a complete spin on the axis.

7. 24 6. Earth makes one rotation every day or _____________ hours.

8. daylight, darkness 7. At any point in time, half of Earth’s surface faces the Sun and is in _____________. The other half of Earth’s surface faces away from the sun and is in _________.

9. tilt 8. The _________________ of Earth’s axis affects the lengths of the day. If the axis were not tilted, day and night would each be 12 hours long.

10. east, west 9. If you watch objects in the sky, such as the Sun, they appear to rise in the ________________, move across the sky, and set in the ______________. The Sun is not actually moving though.

11. Apparent motion, rotation 10. _____________ ____________ is the way something appears, or seems, to move. Earth’s _______________ causes the apparent motion of many objects in space.

12. revolves, orbit 11. Earth ________________________ around the Sun. To revolve means to move around an object. The path a revolving object follows is its ____________________.

13. ellipse 12. Earth’s orbit is shaped like an __________, or a slightly flattened circle.

14. seasons 13. Recall that Earth’s axis is tilted and it takes 365 ½ days to make a full revolution. The ______________ result from both Earth’s tilted axis and its revolution around the Sun.

15. winter, summer 14. As Earth revolves around the Sun, the tilted axis points in the same direction. When the Northern Hemisphere is tilted away from the Sun, it is _________ in the Northern Hemisphere. At the same time, it is _____________ in the Southern Hemisphere because it is angled toward the Sun.

16. opposite 15. Because the tilt of Earth’s axis always points in the same direction, the seasons in the Northern and Southern Hemispheres are always _____________________.

17. dos not, sun 16. Unlike stars, the Moon __________ _____________ make its own light, it reflects the light from the _________.

18. 29, month 17. The Moon completes one orbit in just over __________ days. This is almost as long as an average ___________.

19. phases 18. During the Moon’s orbit, we see different amounts of the moon lit by the Sun. The apparent shapes of the Moon in the sky are called ______________________. The Moon cycles through all of its phases during one complete orbit.

20. waxing, waning, new moon As the Moon appears to get larger, it is ___________. As it appears to get smaller, it is _________. During the ________ __________ phase, the Moon cannot be observed at all.