1. The Earth-Moon-Sun System
Chapter 7
The Earth-Moon-Sun System

2. I. Earth in Space A. Review Vocabulary: Orbit  curved path of one object, such as the Moon, around another object, such as Earth. B. Sphere  a three-dimensional, round object whose surface is the same distance from the center in all directions. C. Gravity  the attractive force between two objects that depends on the masses of the objects and the distance between them.

4. D. Earth’s magnetic field protects us from harmful radiation from the Sun. E. What do Scientists think caused the magnetic field around Earth? Earth’s rotation and movement of matter in the core set up a strong magnetic field around Earth. F. Earth’s magnetic pole is tilted about 11.5° from Earth’s geographical axis of rotation.

6. G. What is polar wandering
G. What is polar wandering? The locations of Earth’s magnetic poles change over time; large-scale movement are thought to be caused by movements in Earth’s crust and upper mantle. H. Particles from the Sun’s solar wind interact with Earth’s magnetic field at the polar regions to create light known as the aurora.

8. I. In the northern hemisphere, this light is called the aurora borealis. J. In the southern hemisphere, this light is called the aurora australis.

9. K. The average distance between the Earth and the Sun is 149,600,000 kilometers. L. The shape of Earth’s orbit around the Sun is an ellipse. M. Ellipse  an elongated, closed curve with two foci.

10. N. When is Earth closest to the Sun. January 3 O
N. When is Earth closest to the Sun? January 3 O. When is Earth farthest to the Sun? July 4 P. Earth is different than other planets because it can support life. Q. By absorbing carbon dioxide, oceans protect Earth from experiencing a greenhouse effect like that on Venus.

11. Greenhouse Effect → atmospheric warming caused by the emission of infrared waves by gases in Earth’s atmosphere.

12. II. Time and Seasons A. The Earth spins and makes on complete turn on its axis in about 24 hours. B. Time Zone → an area 15° wide in which the time is the same. C. Rotation → the spinning of Earth on its axis; used to measure time in days.

14. D. The apparent movement of the Sun from noon one day to noon the next day is called a solar day. E. Revolution → the movement of Earth in its orbit around the Sun; used to measure time in years. F. Ecliptic → the yearly path of Earth around the Sun.

16. G. What causes Earth's seasons? The tilt of Earth’s rotational axis.
H. Earth's axis is tilted at an angle of 23.5°.
Earth's geographic north pole points toward the star Polaris.
J. During summer in the northern hemisphere, the Sun's rays strike the Earth at a (higher, lower) angle, which causes the rays to be more intense and warms Earth's surface.

18. K. During winter in the northern hemisphere, the Sun's rays strike the Earth at a (higher, lower) angle, which causes the rays to be less intense and Earth's surface is cooler. L. The hemisphere that is tilted toward the Sun is having summer. M. The hemisphere that is tilted away from the Sun is having winter.

19. N. When does Earth's northern hemisphere experience more hours of daylight? June 21 O. When does Earth's northern hemisphere experience the least amount of daylight hours? December 21 P. Equinox → occurs twice a year when Earth’s axis of rotation is perpendicular to a line connecting the center of the Earth to the center of the Sun. Q. The vernal (spring) equinox occurs on March 20 or 21. R. The autumnal (fall) equinox occurs on September 22 or 23.

20. S. Solstice → occurs twice a year when Earth’s axis of rotation is tilted directly toward or away from the Sun. T. The summer solstice occurs on June 21 or 22. U. The winter solstice occurs on December 21 or 22. V. In the southern hemisphere, the equinoxes and solstices are reversed.

22. III. Earth's Moon A. How long does it take the Moon to make one revolution around the Earth and line up with the same star again? 27.3 days (a sidereal month) B. Because the Earth also revolves around the Sun, it takes the Moon more than 2 days to line up with the Earth and Sun again. C. A complete lunar phase cycle takes 29.5 days, known as a synodic month.

24. D. Does the Moon rotate on its axis. Yes E
D. Does the Moon rotate on its axis? Yes E. How many days does it take the Moon to make one complete rotation on its axis? 27.3 days F. What is the result of the Moon rotating on its axis and orbiting the Earth in the same amount of time? We always see the same side of the Moon.

25. G. Tide  the rise and fall of the surface level of the ocean. 1
G. Tide  the rise and fall of the surface level of the ocean. 1. What causes the tides? A giant wave produced by the gravitational pulls of the Sun and the Moon. 2. The height of this wave is only 1 or 2 meters high, but the wavelength is thousands of kilometers long.

26. 3. As the crest of the wave approaches the shore, the level of the water (rises, drops), this is called high tide.
4. About 6 hours later, the trough of the wave approaches the shore, the level of the water (rises, drops), this is called low tide.
Does the Sun have an effect on the tides? Yes
6. Why does the Moon have a greater affect on Earth’s tides than the Sun? Because the Moon is closer to Earth than the Sun.

27. Spring Tide  a higher high tide and a lower low tide; occurs when the Sun, Earth and Moon are lined up.
8. Neap Tide  a lower high and a higher low tide; occurs when the Sun, Earth and Moon form a right angle.

29. H. Moon Phases  the changing appearance of the Moon as viewed from Earth, depending on the relative positions of the Sun, the Moon, Earth, and the observer. 1. Why does the Moon shine? It reflects light from the Sun. 2. Describe the new moon phase: The side of the Moon facing away from Earth is lighted and the side of the Moon facing Earth receives no light from the Sun.

30. 3. Waxing  the lighted portion that we see appears (smaller, larger) each night. 4. Describe the full moon phase: We see the entire lighted side of the Moon. 5. Waning  the lighted portion that we see appears (smaller, larger) each night.

32. I. Eclipses occur when Earth or the Moon temporarily blocks sunlight from reaching the other object. 1. Eclipses can only occur when the Sun, Earth and Moon perfectly line up. 2. Why do eclipses only occur a few times each year and not every month? The Moon’s orbit is tilted about 5° from the plane of Earth’s orbit around the Sun.

33. 3. Solar Eclipse  occurs during new moon, when the Moon passes directly between the Sun and Earth, casting a shadow on part of Earth. 4. Umbra  the darkest portion of the Moon’s shadow. People in this area will experience a total solar eclipse. 5. Penumbra  the lighter portion of the Moon’s shadow. People in this area will experience a partial solar eclipse.

34. Solar Eclipse

35. 6. Lunar Eclipse  occurs during a full moon, when the Moon enters Earth’s umbra and Earth casts a curved shadow on the Moon’s surface.
7. When the Moon is completely in Earth’s umbra, why does it appear a dark red color? Light from the Sun is scattered and refracted by Earth’s atmosphere.

36. Lunar Eclipse

37. Who gets to see a solar eclipse?
Only people in the umbra will experience a total solar eclipse.
Who gets to see a lunar eclipse? Anyone on the nighttime side of Earth.

38. J. The Moon’s Surface 1. How did the Moon’s craters form
J. The Moon’s Surface 1. How did the Moon’s craters form? Formed by the impact of meteorites, asteroids, and comets. 2. Maria  relativelt flat, dark-colored regions on the Moon’s surface. 3. Maria have (igneous, sedimentary, metamorphic) rocks, this means that the Moon’s interior was once molten.

39. 4. Regolith  a layer of debris on the Moon’s surface formed by the accumulation of meteoric material.

40. K. The Moon’s Interior 1. It is believed that the Moon’s interior separated into layers when it cooled. 2. Apollo astronauts left seismographs to measure moonquakes.
3. List the layers of the Moon’s interior: Core, Lower Mantle, Upper Mantle, Crust

41. L. Exploring the Moon 1. What was the name of the spacecraft that was placed in lunar orbit? What was its purpose? Clementine. It compiled a detailed map of the Moon’s surface. 2. What is the name of the oldest identifiable impact feature? The South Pole-Aitken Basin 3. What is interesting about the side of the Moon facing Earth? The crust on the side facing Earth is much thinner than the far side.

42. 4. Mascons  concentrations of mass located under impact basins. 5
4. Mascons  concentrations of mass located under impact basins. 5. What is the Moon’s core like? Small, iron-rich
6. What were the names of the two spacecraft that found evidence of water-ice on the Moon? Clementine and Lunar Prospector

43. M. Giant Impact Theory 1. The Moon formed about 4
M. Giant Impact Theory 1. The Moon formed about 4.6 billion years ago when a Mars-sized object collided with Earth. 2. The violent collision melted and vaporized some of Earth’s crust and mantle and hurled it into space. 3. Some material fell back to Earth, some esacped into interplanetary space, and some orbited Earth as a ring of hot gas and debris.

45. 4. Solid particles eventually condensed from the cooling gas and the Moon began to form.