mastering ch 2

How many arcminutes are in a full circle?

21600 arcminutes

Suppose that instead of being inclined to Earth's orbit around the Sun, the Moon's orbit was in the same plane as Earth's orbit around the Sun. (Click "Show Moon with flat orbit" to see this situation.) In this hypothetical situation, approximately how many solar eclipses would occur each year? 0 1 2 12 24

12

What is the Moon's angular size in arcseconds?

1800 arcseconds

In reality, the Moon's orbit about Earth is tilted (by about 5°) with respect to Earth's orbit about the Sun. As a result, the actual number of solar eclipses that occur each year is approximately _____. 0 2 12 24

2

Which of the following statements best describes the Mayans' view of the year 2012, according to the quotes attributed to Dr. Anthony Aveni, an astronomer and anthropologist at Colgate University?

2012 is the last year in a calendar of years, with no more significance than Dec. 31 on our calendar or 12:59 on our clocks.

Today, astronomers can detect and measure stellar parallax for thousands of the nearest stars, providing us with direct evidence that Earth really does orbit the Sun. Moreover, as the Parallax Angle animation shows, these measurements allow us to calculate distances to these relatively nearby stars. If we hope to use parallax to measure distances to even more-distant stars, which of the following telescopes would be most useful? An extremely large telescope built at the best observing site on Earth A telescope placed on the same orbit of the Sun as Earth, but on the opposite side of the Sun A larger version of the Hubble Space Telescope, placed in Earth orbit A telescope that orbits the Sun in the outer solar system

A telescope that orbits the Sun in the outer solar system

If you could change the layout of the solar system, which of the following would cause a lunar eclipse to occur at least once every month in this hypothetical situation? Make the Moon orbit Earth twice as fast. Change the Moon's orbital plane so it tilts the opposite way. Relocate the Moon to twice its current distance from Earth. Change the Moon's orbital plane so it is in the same plane as Earth's orbit around the Sun.

Change the Moon's orbital plane so it is in the same plane as Earth's orbit around the Sun.

When we see Saturn going through a period of apparent retrograde motion, it means: Saturn is temporarily moving backward in its orbit of the Sun. Earth is passing Saturn in its orbit, with both planets on the same side of the Sun. Saturn and Earth must be on opposite sides of the Sun.

Earth is passing Saturn in its orbit, with both planets on the same side of the Sun.

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.

As you saw in Part C, stellar parallax exists only because Earth orbits the Sun. Therefore, if the ancient Greeks had measured stellar parallax, they would have known that their belief in an Earth-centered universe was wrong. Why didn't the ancient Greeks measure stellar parallax? Their belief in an Earth-centered universe meant that they did not expect parallax, and therefore did not look for it. The Greeks thought all the stars were the same distance away, residing on a celestial sphere. Even for the nearest stars, parallax angles are too small to measure with the naked eye. Some Greeks actually did measure it, but they did not understand the importance of their measurements.

Even for the nearest stars, parallax angles are too small to measure with the naked eye.

Part of the premise Emmerich's film "2012" is that the Earth and its crust start to absorb neutrinos. These neutrinos cause a lot of problems, among them, earthquakes. Why is this idea scientifically implausible? Neutrinos don't have much energy, therefore they aren't very important. Neutrinos interact rarely with anything on Earth. Neutrinos are naturally generated during radioactive decay, and these neutrinos actually cause earthquakes.

Neutrinos interact rarely with anything on Earth.

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. Yes, but the Greeks did not realize it because they never even considered a Sun-centered model. Yes, but the Greeks were unable to detect apparent retrograde motion and therefore didn't know that it ruled out an Earth-centered universe. No, because apparent retrograde motion still happens in an Earth-centered system as the Sun passes by a planet in its orbit around Earth.

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 rays that reach Earth and the Moon come from only one very small spot on the Sun. 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. The video is incorrect; the Sun's rays actually converge on the Moon from all directions, not just as parallel rays. Rays from the Sun that start out going in different directions turn toward Earth as they travel away from the Sun.

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.

In the Introduction to Parallax animation, notice that the parallax is greater (the apparent movement is larger) for the person than for the trees, and that the mountains do not appear to shift at all. Why? The amount of parallax depends on an object's distance, with greater parallax for more distant objects. The amount of parallax depends on an object's size, with greater parallax for larger objects. The amount of parallax depends on an object's distance, with greater parallax for nearer objects. The amount of parallax depends on an object's size, with greater parallax for smaller objects.

The amount of parallax depends on an object's distance, with greater parallax for nearer objects.

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 Moon is too small compared to Earth. The astronaut is too big compared to the Moon. Earth is rotating much too fast relative to the speed of the Moon's orbit in the video. 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.

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.

What conditions must exist for a lunar eclipse to occur? The only condition is that the phase of the Moon must be new. The phase of the Moon must be new and the Moon must be passing through Earth's orbital plane. The only condition is that the phase of the Moon must be full. The phase of the Moon must be full and the Moon must be passing through Earth's orbital plane.

The phase of the Moon must be full and the Moon must be passing through Earth's orbital plane.

What conditions must exist for a solar eclipse to occur? The only condition is that the phase of the Moon must be new. The phase of the Moon must be new and the Moon must be passing through Earth's orbital plane. The only condition is that the phase of the Moon must be full. The phase of the Moon must be full and the Moon must be passing through Earth's orbital plane.

The phase of the Moon must be new and the Moon must be passing through Earth's orbital plane.

The Introduction to Parallax animation demonstrates the basic idea of parallax. Click the play button, and watch how the motion of the photographer (lower window) affects what the camera sees (upper window). Which of the following statements correctly describes what is really happening? (Note: You need not continue with the next button to answer this question.) The photographer, the person being photographed, and the trees are all moving at the same speed. The photographer is moving, but the person being photographed and the trees are staying still. The photographer is staying still, but the person being photographed and the trees are moving. The trees are moving more slowly than the person being photographed, who is moving more slowly than the photographer.

The photographer is moving, but the person being photographed and the trees are staying still.

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 two points on the far left and far right at the two points at the top and bottom at the point on the far left at the point on the far right

at the point on the far left

You've now seen that Earth's varying distance cannot be the cause of our seasons. So what is the cause of the seasons? Earth's speed varies in its orbit around the Sun, giving us summer when Earth is moving fastest and winter when Earth is moving slowest. The seasons are caused by variation in the amount of rainfall (or snowfall) in different places at different times of year. The tilt of Earth's axis causes the Northern Hemisphere to be closer to the Sun than the Southern Hemisphere in summer, and vice versa in winter. The tilt of Earth's axis causes different portions of the Earth to receive more or less direct sunlight at different times of year.

The tilt of Earth's axis causes different portions of the Earth to receive more or less direct sunlight at different times of year.

Based on what you have learned from your rankings in Parts A and B, which statement best describes how variation in the Earth-Sun distance affects the seasons? Summer occurs when Earth is closer to the Sun and winter occurs when Earth is farther from the Sun. No matter where you live or what the seasons, it is generally hotter when Earth is closer to the Sun and colder when Earth is farther from the Sun. The variation in Earth-Sun distance over the course of each year has virtually no effect on the seasons.

The variation in Earth-Sun distance over the course of each year has virtually no effect on the seasons.

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. We see different faces of the Moon at different times. We see phases of the Moon. Astronauts on the Moon sometimes appear to hang upside-down.

We always see the same face of the Moon.

Stellar parallax occurs in much the same way as parallax on Earth, with greater parallax for stars that are nearer. Explore the Parallax Angle animation, and watch how the motion of the star changes in the "View from Earth" window. Which statement best summarizes why stellar parallax occurs? Nearby stars move at higher speeds relative to the Sun than more distant stars. We view nearby stars from different positions on Earth as Earth rotates on its axis. We view nearby stars from different positions in Earth's orbit at different times of year. Nearby stars move in tiny circles as Earth orbits the Sun.

We view nearby stars from different positions in Earth's orbit at different times of year.

Which of the following predictions is the most likely to come to pass? The world will end in 2012, in a barrage of severe solar storms. The world will end in 2012, as tidal forces arising from alignments with the Galactic Center shred the Earth. The world will end in 2012, from something we haven't even imagined yet. When the world doesn't end in 2012, somebody will identify some other apocalyptic date in the future, and make millions from books, appearance fees, and movies. The world will end in 2012, with crust-rending earthquakes and giant volcanic eruptions.

When the world doesn't end in 2012, somebody will identify some other apocalyptic date in the future, and make millions from books, appearance fees, and movies.

How frequently does the Galactic Center (in the constellation Sagittarius) and the Sun align, that is, appear in the same constellation? about once a day only in 2012 about once a year

about once a year

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 point on the far right at the two points on the far left and far right at the two points at the top and bottom at the point on the far left

at the two points at the top and bottom

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

Based on their inability to detect stellar parallax, the ancient Greeks concluded that _________. they lacked the technology necessary for detecting stellar parallax Earth must be the center of the universe either Earth is the center of the universe or stars are extremely far away the stars must be extremely far away

either Earth is the center of the universe or stars are extremely far away

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? only at the two points on the far left and far right (the new and full moon positions) everywhere along its orbit only at the point on the far right (the new moon position) only at the two points at the top and bottom (the first- and third-quarter positions) only at the point on the far left (the full moon position)

everywhere along its orbit

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.

left eat right west

waning crescent moon

occurs about 3 days before new moon visible near eastern horizon just before sunrise

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

full moon

rises at about the time the Sun sets occurs 14 days after the new moon visible due south at midnight

waxing crescent moon

sets 2-3 hours after the Sun sets visible near western horizon about an hour after sunset

A week after full moon, the Moon's phase is: first quarter. third quarter. new.

third quarter.

The North Celestial Pole is 35 ∘ above your northern horizon. This tells you that: you are at latitude 35 ∘ N. you are at longitude 35 ∘ E. you are at latitude 35 ∘ S.

you are at latitude 35