Ch 2 Homework B

The reason we do not have a solar eclipse at every new moon is that

The Moon's orbit is inclined relative to Earth's orbit around the Sun.

Again consider the position of the Moon in Waxing Crescent. How much of the Moon's surface is covered by Earth's shadow?

None

During the time that a planet is in its period of apparent retrograde motion, __________.

Over many days or weeks, the planet moves westward relative to the stars, rather than the usual eastward relative to the stars

Suppose you look up in the sky and the Moon appears as a Waning Gibbous. Which of the following diagrams correctly shows the Moon's location in its orbit around Earth for this phase?

Position 6

If you wanted to document the apparent retrograde motion of Mars, you would need to measure and record Mars's ______ over a period of ______.

Position among the constellations, Several months

Consider a time when Mars is in the middle of one of its periods of apparent retrograde motion. During this time, Mars appears ______ in our night sky and crosses the meridian around ______.

Brightest, Midnight

The following figures show a top view of Earth, sunlight, and six different positions of the Moon as it orbits Earth. Note that the distances shown are not drawn to scale. Rank each of the six lunar positions from left to right based on the amount of the Moon's illuminated surface that is visible from Earth, from greatest to least. (If two diagrams have an equal amount of illumination as seen from Earth, put one on top of the other.)

- Full - Waning Gibbous - Quarter(s) - Waxing Crescent - New

The following figures show a top view of Earth, sunlight, and six different positions of the Moon as it orbits Earth. Note that the distances shown are not drawn to scale. Rank each of the six lunar positions from left to right based on the amount of the Moon's illuminated surface that is visible from Earth, from greatest to least. (If two diagrams have an equal amount of illumination as seen from Earth, put one on top of the other.)

- Full Moon - Waning Gibbous - Quarter(s) - Waxing Crescent - New Moon

Shown following are five different phases of the Moon as seen by an observer in the Northern Hemisphere. Imagine that tonight the Moon is in the waxing gibbous phase as shown here. Rank the pictured phases from left to right based on the order in which you would see them over the subsequent four weeks, from first seen to last.

- Waning Gibbous - Third Quarter - Waning Crescent - Waxing Crescent - First Quarter

Shown following are five different phases of the Moon as seen by an observer in the Northern Hemisphere. Imagine that tonight the Moon is in the waxing gibbous phase. Rank the pictured phases from left to right based on the order in which you would see them over the subsequent four weeks, from first seen to last.

- Waning Gibbous - Third Quarter - Waning Crescent - Waxing Crescent - First Quarter

Although the Causes of Lunar Phases video is very useful for learning about phases of the Moon, it is inaccurate in some ways. Which of the following correctly identify inaccuracies with this video?

-The astronaut is too big compared to the Moon. -The Moon is too big compared to its orbit. -Earth is too big compared to the Moon's orbit. -The Moon is too big compared to Earth.

Listed following are locations and times at which different phases of the Moon are visible from Earth's Northern Hemisphere. Match these to the appropriate moon phase.

-Waxing Crescent Moon: Visible near western horizon about an hour after sunset. Sets 2-3 hours after the Sun sets. -Waning Crescent Moon: Visible near eastern horizon just before sunrise. Occurs about 3 days before new moon. -Full Moon: Rises at about the time the Sun sets. Visible due south at midnight. Occurs 14 days after the new moon.

What is an annular eclipse?

A solar eclipse in which the Moon does not appear large enough to fully block the Sun

When is the next opportunity to see a total solar eclipse in the United States?

April 8, 2024

Watch the Causes of Lunar Phases video. To understand phases of the Moon, you must imagine the view from Earth looking out to the Moon as it orbits. At what position(s) in its orbit would we see all of the Moon's daylight side and none of its night side?

At the point on the far left

Look again at the Causes of Lunar Phases video. At what position(s) in the Moon's orbit would we see exactly half of the Moon's daylight face and exactly half of its night face?

At the two points at the top and bottom

What is really happening in space during the periods when we see Mars going through apparent retrograde motion?

Earth is passing by Mars in its orbit around the Sun.

At most times, Mars appears to move ______ relative to the stars. The exceptions are during its periods of apparent retrograde motion, when Mars appears to move ______ relative to the stars.

Eastward, Westward

Play the Moon Orbit video through to where you see the Moon orbiting Earth at correctly scaled sizes. Notice that Earth's daylight side (white) is on the right in this view, and its night side (gray) is on the left. Where along its orbit would the Moon also have its daylight side on the right and its night side on the left?

Everywhere along its orbit

Consider the Moon when it is in the position shown in the moon phase diagram below (Waxing Crescent). How much of the Moon's total surface is illuminated by sunlight at this time?

Exactly Half

The following figures show a top view of Earth, sunlight, and six different positions of the Moon as it orbits Earth. Note that the distances shown are not drawn to scale. Rank each of the six lunar positions based on the amount of the Moon's total surface that is illuminated by sunlight. If two (or more) diagrams have an equal amount of surface illuminated by sunlight, put one on top of the other. (Assume that conditions for an eclipse are not met in any of these diagrams.)

Exactly half of the Moon's surface is illuminated by sunlight at all times!

If there is going to be a total lunar eclipse tonight, then you know that the Moon's phase is...

Full

Suppose you see a crescent moon; how much of the Moon's entire surface (the full globe of the Moon) is in daylight?

Half

Which of the following best summarizes the reason we see phases of the Moon?

Half the Moon is always illuminated by the Sun, but the phase we see depends on how much of this half we are looking at from Earth.

Start at the beginning of the Moon Orbit video, which shows the Sun and part of Earth's orbit. If we wanted to show the Moon's orbit on the scale of this starting frame, we would need to draw a circle that __________.

Is smaller than one of the green dashes that show Earth's orbit

What is stellar parallax?

It is the slight back-and-forth shifting of star positions that occurs as we view the stars from different positions in Earth's orbit of the Sun.

Sort each item into the correct bin based on whether it describes lunar eclipses or solar eclipses.

Lunar Eclipse: -Occurs when the Moon is on the direct opposite side of Earth from the Sun -Occurs when Earth's shadow falls on the Moon -Can occur only at full moon -Can be seen by anyone on Earth's night side at the time Solar Eclipse: -Occurs when the Moon's shadow falls on Earth -Can occur only at new moon -Can be seen only along a relatively narrow path on Earth -Occurs when the Moon comes directly between Earth and Sun

The Sun-centered system pictured in the lower window of the video offers a simple explanation for observations of apparent retrograde motion. Should these facts alone have been enough to convince the ancient Greeks that Earth really does go around the Sun?

No, because the Greeks had an Earth-centered model that also accounted for apparent retrograde motion

As you play the Moon Orbit video, notice how the arrows representing the Sun's rays are at first spread apart but become parallel as the video zooms in on the Moon's orbit. Why do the Sun's rays become parallel at the end of the video?

The Sun is so far away compared to the size of the Moon's orbit that all the rays reaching the orbit come from essentially the same direction.

Full Shadow (umbra)

The dark, central region of an object's shadow, in which light from the Sun is fully blocked

Partial Shadow (penumbra)

The larger, surrounding region of an object's shadow in which light from the Sun is only partially blocked

One week after full moon, the Moon's phase is

Third Quarter

Look again at the Causes of Lunar Phases video. As the Moon orbits, notice how the astronaut's head always points toward Earth. What do we see from Earth that occurs for the same reason? (Be sure you are viewing the first portion of the video, with the rotating Moon, not the hypothetical, non-rotating view, shown afterward.)

We always see the same face of the Moon.