MasteringAstronomy Assignment #4

Visual Activity: Exploring the Cause of the Greenhouse Effect

On a cloudless day, what happens to most of the visible light headed toward Earth?
It reaches Earth’s surface, where some is reflected and some is absorbed.

On a day with complete cloud cover, what happens to the visible light headed toward Earth?
The clouds reflect much of it back to space, though some still reaches the surface

What happens to the energy that the ground absorbs in the form of visible sunlight?
It is returned upward in the form of infrared light.

The greenhouse effect raises Earth’s surface temperature (from what it would be otherwise) because the infrared light radiated by Earth’s surface __________.
is temporarily absorbed by greenhouse gases and then reemitted in random directions



Internal Structure of Earth
Part A
We currently believe that Earth’s structure is made up of six main regions. Three of these regions can be directly observed and three cannot. Label the six major regions of Earth in the following image.

Part B
Although scientists cannot directly observe Earth’s mantle or core, they can learn about these regions indirectly by observing the behavior of seismic waves from earthquakes. Seismic waves come in two basic forms (see figure). Pressure (P) waves move material back-and-forth in the direction of the waves' motion. Compressing and expanding a slinky will produce this sort of oscillation. Shear (S) waves, on the other hand, move material side-to-side in directions perpendicular to the waves' motion. The oscillations of a jump rope, a guitar string, and the ocean surface are all examples of shear waves.

Part C
By sensing the different types of seismic waves from earthquakes, it is possible to create a model of Earth's interior that satisfies scientific observations. Scientists station seismographs all around Earth to record earthquakes. By analyzing the data, scientists can determine which stations detect which kinds of waves from a particular earthquake. In the following figure, an earthquake on one side of Earth has produced longitudinal pressure waves (P-waves) and perpendicular shear waves (S-waves). The P-waves can travel through liquid, but the S-waves cannot. Given the interior structure depicted in the figure, label the types of waves that would be detected by stations at the four different positions.

Part D
To understand how Earth’s interior structure was formed, we need to go back in time to its formation during the birth of the solar system. Astronomers believe that when Earth and the other terrestrial planets formed, a process called differentiation occurred. Rank the steps of the differentiation process in order from the initial stage to the final stage.

Gravitational Interactions between Earth and the Moon

Part A
The Moon and Earth interact through their mutual gravitational forces. The Moon's rotation rate and the ocean tides on Earth are consequences of the gravitational tidal forces exerted by each body on the other. Considering the Moon, rank the gravitational tidal force exerted on it by Earth for three different lunar locations.

Part B
Due to gravitational tidal forces from Earth, the Moon has a deformation of its shape known as a tidal bulge. Likewise, Earth has a tidal bulge owing to the Moon's gravity. The image choices show both tidal bulges, where the arrows denote the direction of gravitational attraction. Which image choice shows the correct relative alignments for the tidal bulges of both Earth and the Moon?

Part C
Besides creating a tidal bulge on the Moon, Earth's gravitational tidal force also affects the Moon's rotation by exerting a force that keeps one side of the Moon's tidal bulge facing Earth as it orbits. This particular phenomenon is called tidal locking, where the Moon's rotation and orbital periods are synchronized. A similar force is exerted by the Moon on Earth's rotation, but to a much smaller extent. Comparing the rotation and orbital period of the Moon with those of Earth, rank the periods from longest to shortest.


Earth's Magnetosphere

Part A
According to the current understanding of Earth's magnetic field and how magnetic fields are generated, which two components in Earth's internal structure are required in order to generate a magnetic field?
Rapidly rotating core
Conducting liquid core

Part B
Earth's magnetosphere acts as a protective shield against the dangerous, high-energy solar wind. The magnetosphere can be visualized as a large sheath surrounding Earth and extending out into space. Two important structures, known as the Van Allen belts, compose the inner regions of the magnetosphere and directly affect the auroral events seen on Earth. Label the appropriate regions of the inner magnetosphere.

Part C
An auroral event occurs due to the interaction between the solar wind, Earth's magnetosphere, and Earth's atmosphere. The following steps describe the process of events leading to the formation of an aurora. Rank the steps in sequence from first to last, in order of how they must occur.

Vocabulary in Context: Plate Tectonics


Conceptual Self-Test
At Earth's geographic North Pole, a magnetic compass needle would point (approximately)
toward Kansas City

If Earth had no Moon, then tides would
occur with the same frequency, but would not be as strong.

Which of the following statements is true?
Because of the tides, the Moon is spiraling away from Earth.