Understanding Our Universe

Stacy Palen, Laura Kay, Bradford Smith

Chapter 2

Patterns in the Sky—Motions of Earth - all with Video Answers

Educators

Chapter Questions

Problem 1

The Sun, Moon, and stars
a. change their relative positions over time.
b. appear to move each day because the celestial sphere rotates about Earth.
c. rise north or south of west and set north or south of east, depending on their location on the celestial sphere.
d. always remain in the same position relative to each other.

Zachary Warner

Zachary Warner

Numerade Educator

Problem 2

Which stars we see at night depend on (select all that apply)
a. our location on Earth.
b. Earth's location in its orbit
c. the time of the observation.
d. the motion of stars relative to one another over the course of the year.

Zachary Warner

Numerade Educator

Problem 3

You see the Moon rising, just as the Sun is setting. What phase is it in?
a. full
b. new
c. first quarter
d. third quarter
e. waning crescent

Chris Johnson

Numerade Educator

Problem 4

If you were standing at Earth's North Pole, where would you see the north celestial pole?
a. at the zenith
b. on the eastern horizon
c. $23.5^{\circ}$ south of the zenith
d. none of the above; the north celestial pole can't be seen from there

Chris Johnson

Numerade Educator

Problem 5

Where on Earth can you stand and, over the course of a year, see the entire sky?
a. only at the North Pole
b. at either pole
c. at the equator
d. anywhere

Zachary Warner

Numerade Educator

Problem 6

The seasons are caused by ________________.

Chris Johnson

Numerade Educator

Problem 7

The tilt of Jupiter's rotational axis with respect to its orbital plane is $3^{\circ}$. If Earth's axis had this tilt, then the seasons on Earth
a. would be much more extreme.
b. would be much less extreme.
c. would be pretty much the same.
d. would occur much differently every year, depending on the alignments.

Chris Johnson

Numerade Educator

Problem 8

You see the first quarter Moon on the meridian. Where is the Sun?
a. on the western horizon
b. on the eastern horizon
c. below the horizon
d. on the meridian

Zachary Warner

Numerade Educator

Problem 9

You do not see eclipses every month because
a. all eclipses happen at night.
b. the Sun, Earth, and the Moon line up only twice a year.
c. the Sun, Earth, and the Moon line up only once a year.
d. eclipses happen randomly and are unpredictable.

Chris Johnson

Numerade Educator

Problem 10

If the Moon were in the same orbital plane, but twice as far from Earth, which of the following would happen? (Choose all that apply.)
a. The phases of the Moon would remain unchanged.
b. Total eclipses of the Sun would not be possible.
c. Total eclipses of the Moon would not be possible.
d. The Moon's cycle would take longer.

Chris Johnson

Numerade Educator

Problem 11

T/F: The celestial sphere is not an actual object in the sky.

Chris Johnson

Numerade Educator

Problem 12

T/F: Eclipses happen somewhere on Earth every month.

Chris Johnson

Numerade Educator

Problem 13

T/F: The phases of the Moon are caused by the relative position of Earth, the Moon, and the Sun.

Chris Johnson

Numerade Educator

Problem 14

T/F: If a star rises north of east, it will set south of west.

Chris Johnson

Numerade Educator

Problem 15

T/F: From the North Pole, all stars in the night sky are circumpolar stars.

Chris Johnson

Numerade Educator

Problem 16

The tilt of Earth's axis causes the seasons because
a. one hemisphere of Earth is closer to the Sun in summer.
b. the days are longer in summer.
c. the rays of light strike the ground more directly in summer.
d. both a and b
e. both b and c

Chris Johnson

Numerade Educator

Problem 17

On the vernal and autumnal equinoxes,
a. the entire Earth has 12 hours of daylight and 12 hours of darkness.
b. the Sun rises due east and sets due west.
c. the Sun is located on the celestial equator.
d. all of the above
e. none of the above

Chris Johnson

Numerade Educator

Problem 18

We always see the same side of the Moon because
a. the Moon does not rotate on its axis.
b. the Moon rotates once each revolution.
c. when the other side of the Moon is facing toward us, it is unlit.
d. when the other side of the Moon is facing Earth, it is on the opposite side of Earth.
e. none of the above

Chris Johnson

Numerade Educator

Problem 19

You see the Moon on the meridian at sunrise. The phase of the Moon is
a. waxing gibbous.
b. full.
c. new.
d. first quarter.
e. third quarter.

Chris Johnson

Numerade Educator

Problem 20

A lunar eclipse occurs when the ________ shadow falls on the ________.
a. Earth's; Moon
b. Moon's; Earth
c. Sun's; Moon
d. Sun's; Earth

Chris Johnson

Numerade Educator

Problem 21

You see the full Moon on the meridian. From this information, you can determine that the time where you are is
a. noon.
b. sunrise, about 6: 00 A.M.
c. sunset, about 6: 00 p.M.
d. midnight.

Zachary Warner

Numerade Educator

Problem 22

What do we call the group of constellations through which the Sun appears to move over the course of a year?
a. the celestial equator
b. the ecliptic
c. the line of nodes
d. the zodiac

Chris Johnson

Numerade Educator

Problem 23

If you were standing at Earth's South Pole, which stars would you see rising and setting?
a. all of them
b. all the stars north of the Arctic Circle
c. all the stars south of the Arctic Circle
d. none of them

Chris Johnson

Numerade Educator

Problem 24

On the summer solstice in the Northern Hemisphere, the Sun
a. rises due east, passes through its highest point on the meridian, and sets due west.
b. rises north of east, passes through its highest point on the meridian, and sets north of west.
c. rises north of east, passes through its highest point on the meridian, and sets south of west.
d. rises south of east, passes through its highest point on the meridian, and sets south of west.
e. none of the above

Zachary Warner

Numerade Educator

Problem 25

In the Tropics,
a. the Sun is directly overhead twice per year.
b. the Sun's rays strike Earth exactly perpendicularly at some times of year.
c. the seasons vary less than elsewhere on Earth.
d. all of the above

Zachary Warner

Numerade Educator

Problem 26

In your study group, two of your fellow students are discussing the phases of the Moon. One argues that the phases are caused by the shadow of Earth on the Moon. The other argues that the phases are caused by the orientation of Earth, the Moon, and the Sun. Explain how the photos in the chapter-opening illustration falsify one of these hypotheses.

Chris Johnson

Numerade Educator

Problem 27

Why is there no "east celestial pole" or "west celestial pole"?

Mayukh Banik

Numerade Educator

Problem 28

Polaris was used for navigation by seafarers such as Columbus as they sailed from Europe to the New World. When Magellan sailed the South Seas, he could not use Polaris for navigation. Explain why.

Zachary Warner

Numerade Educator

Problem 29

We tend to associate certain constellations with certain times of year. For example, we see the zodiacal constellation Gemini in the Northern Hemisphere's winter (Southern Hemisphere's summer) and the zodiacal constellation Sagittarius in the Northern Hemisphere's summer. Why do we not see Sagittarius in the Northern Hemisphere's winter (Southern Hemisphere's summer) or Gemini in the Northern Hemisphere's summer?

Chris Johnson

Numerade Educator

Problem 30

Describe the Sun's apparent daily motion on the celestial sphere at the vernal equinox.

Prabhat Tyagi

Numerade Educator

Problem 31

Why is winter solstice not the coldest time of year?

Chris Johnson

Numerade Educator

Problem 32

What is the approximate time of day when you see the full Moon near the meridian? At what time is the first quarter (waxing) Moon on the eastern horizon? Use a sketch to help explain your answers.

Chris Johnson

Numerade Educator

Problem 33

Assume that the Moon's orbit is circular. Suppose you are standing on the side of the Moon that faces Earth.
a. How would Earth appear to move in the sky as the Moon made one revolution around Earth?
b. How would the "phases of Earth" appear to you compared to the phases of the Moon as seen from Earth?

Chris Johnson

Numerade Educator

Problem 34

Astronomers are sometimes asked to serve as expert witnesses in court cases. Suppose you are called in as an expert witness, and the defendant states that he could not see the pedestrian because the full Moon was casting long shadows across the street at midnight. Is this claim credible? Why or why not?

Zachary Warner

Numerade Educator

Problem 35

From your own home, why are you more likely to witness a partial eclipse of the Sun rather than a total eclipse?

Zachary Warner

Numerade Educator

Problem 36

Why do we not see a lunar eclipse each time the Moon is full or witness a solar eclipse each time the Moon is new?

Zachary Warner

Numerade Educator

Problem 37

Why does the fully eclipsed Moon appear reddish?

Chris Johnson

Numerade Educator

Problem 38

In the Gregorian calendar, the length of a year is not 365 days, but actually about 365.24 days. How do we handle this extra quarter day to keep our calendars from getting out of sync?

Victor Salazar

Numerade Educator

Problem 39

Vampires are currently prevalent in popular fiction. These creatures have extreme responses to even a tiny amount of sunlight (the response depends on the author), but moonlight doesn't affect them at all. Is this logical? How is moonlight related to sunlight?

Keshav Singh

Numerade Educator

Problem 40

Suppose you are on a plane from Dallas, Texas, to Santiago, Chile. On the way there, you realize something amazing. You have just experienced the longest day of the year in the Northern Hemisphere and are about to experience the shortest day of the year in the Southern Hemisphere on the same day! On what day of the year are you flying? How do you explain this phenomenon to the person in the seat next to you?

David Morabito

Numerade Educator

Problem 41

Earth is spinning at $1,670 \mathrm{km} / \mathrm{h}$ at the equator. Use this number to find Earth's equatorial diameter.

Chris Johnson

Numerade Educator

Problem 42

The waxing crescent Moon appears to the east of the Sun and moves farther east each day. Does this mean it rises earlier each day or later? By how much?

Chris Johnson

Numerade Educator

Problem 43

Romance novelists sometimes say that as the hero rides off into the sunset, the full Moon is overhead. Is this correct? Why or why not? Draw a picture of the Sun, Moon, and Earth at full Moon phase to explain your answer.

Prabhu Ramji

Numerade Educator

Problem 44

Suppose you are on vacation in Australia, right on the Tropic of Capricorn. What is your latitude? What is the largest angle from the south celestial pole at which stars are circumpolar at your location?

Chris Johnson

Numerade Educator

Problem 45

The Moon's orbit is tilted by about $5^{\circ}$ relative to Earth's orbit around the Sun. What is the highest altitude in the sky that the Moon can reach, as seen in Philadelphia (latitude $40^{\circ}$ north)?

Chris Johnson

Numerade Educator

Problem 46

Imagine you are standing on the South Pole at the time of the southern summer solstice.
a. How far above the horizon will the Sun be at noon?
b. How far above (or below) the horizon will the Sun be at midnight?

Alexander Cheng

Alexander Cheng

Numerade Educator

Problem 47

Find out the latitude where you live. Draw and label a diagram showing that your latitude is the same as (a) the altitude of the north celestial pole and (b) the angle (along the meridian) between the celestial equator and your local zenith. What is the noontime altitude of the Sun as seen from your home at the times of winter solstice and summer solstice?

Chris Johnson

Numerade Educator

Problem 48

Let's say you use a protractor to estimate an angle of $40^{\circ}$ between your zenith and Polaris. Are you in the continental United States or Canada?

Chris Johnson

Numerade Educator

Problem 49

Suppose the tilt of Earth's equator relative to its orbit were $10^{\circ}$ instead of $23.5^{\circ} .$ At what latitudes would the Arctic and Antarctic circles and the tropics of Cancer and Capricorn be located?

Chris Johnson

Numerade Educator

Problem 50

Carefully draw a diagram of the Moon and its shadow at both its current distance and twice as far from Earth. If the Moon were twice as far from Earth, which of the following would happen?
a. Total eclipses of the Sun would not be possible.
b. Total eclipses of the Moon would not be possible.

Chris Johnson

Numerade Educator