Question 1

A science fiction writer, writing a story about inhabitants on Earth in 14,000 A.D. who have survived a disaster that included the loss of modern navigational aids, describes them traveling due north across barren wastes by walking toward Polaris, the pole star. What is wrong with this situation?

Accepted Answer

A)   Polaris will have moved away from due north since it is moving rapidly with respect to surrounding stars.
B)   Polaris will no longer be due north because of Earth's precession.
C)   By that time, Polaris will be due south, not due north, because of the reversal of Earth's spin axis.
D)   Polaris will no longer be visible since its lifetime is only a few thousand years.E) A) and B)
F) A) and C)

Question 2

What will be the elevation angle of the Sun above the horizon at midday on June 21 every year at latitude 66.5° S?

Accepted Answer

A)   90°, in the zenith
B)   23.5°
C)   The Sun will not appear above the horizon at all on this date at this location.
D)   0°E) A) and B)
F) A) and C)

Question 3

Which one of these is NOT a zodiac constellation?

Accepted Answer

A)   Pisces
B)   Cancer
C)   Ophiuchus
D)   CygnusE) A) and B)
F) C) and D)

Question 4

The phase of the Moon when Sun and Moon are separated by 6 hours of right ascension is always

Accepted Answer

A)   full Moon.
B)   new Moon.
C)   crescent.
D)   either first or third quarter.E) B) and C)
F) A) and B)

Question 5

Would a calendar based on a sidereal day be satisfactory?

Accepted Answer

A)   No. Noon on the clock would become earlier than the high point of the Sun by 4 minutes each day until eventually it would occur in the middle of the night.
B)   No. Noon on the clock would become later than the high point of the Sun by 4 minutes each day until eventually it would occur in the middle of the night.
C)   No. The seasons would be reversed.
D)   Yes, but, we would have to add an extra day every year.E) A) and D)
F) A) and C)

Question 6

On December 21 of this year, the Sun will be at what declination angle?

Accepted Answer

A)   90°
B)   +23.5°
C)   0°
D)   -23.5°E) B) and C)
F) A) and D) D

Question 7

If the stars Polaris and Arcturus are seen to be 71° apart, as shown in Figure 1-5, how far away from Polaris is the closest star in Ursa Major?

Accepted Answer

A)   0.25°
B)   2.5°
C)   25°
D)   250°E) B) and C)
F) A) and D)

Question 8

The angle subtended at an observer by a city transit bus (length 9 m)  at a distance of 1000 m is close to

Accepted Answer

A)   1000/9, or 111.1 arcseconds.
B)   ½ of a degree.
C)   9000 arcminutes.
D)   9/1000, or 0.009 arcseconds.E) B) and C)
F) A) and D)

Question 9

During a total lunar eclipse, the Moon is

Accepted Answer

A)   totally invisible since Earth blocks all light from reaching it.
B)   barely visible because of "zodiacal light," that is, sunlight reflected off dust grains in space.
C)   barely visible because it glows slightly by its own light.
D)   barely visible because of light passing through Earth's atmosphere.E) A) and C)
F) A) and B) D

Question 10

How long will it take for precession to move Earth's spin axis to a position perpendicular to the ecliptic plane?

Accepted Answer

A)   no time at all because the axis is in this position now
B)   a very long or even infinite time because it is very unlikely to happen
C)   13,000 years
D)   26,000 yearsE) A) and B)
F) A) and C)

Question 11

If the plane of the Moon's orbit were the same as the ecliptic plane, there would be a lunar eclipse

Accepted Answer

A)   twice per month.
B)   twice per year.
C)   every day.
D)   once per month.E) None of the above
F) All of the above

Question 12

Solar eclipses (when the Moon and Sun are precisely in line)  can be either total (Sun completely covered)  or annular (Sun not quite covered)  when viewed from the eclipse centerline. This is because

Accepted Answer

A)   the Moon has deep valleys on its surface.
B)   the Moon's orbit is inclined at several degrees to that of Earth.
C)   the Moon's distance from Earth varies from eclipse to eclipse.
D)   of the time of day at the viewing site; annular eclipses always occur in early mornings and early evenings.E) None of the above
F) A) and D)

Question 13

What was the approximate value of right ascension of the Sun this year on December 21?

Accepted Answer

A)   6 hours 0 minutes
B)   0 hours 0 minutes
C)   18 hours 0 minutes
D)   12 hours 0 minutesE) A) and B)
F) None of the above

Question 14

One-billionth divided by one-millionth is equal to

Accepted Answer

A)   10-15
B)   1015
C)   10-3
D)   103E) A) and B)
F) None of the above

Question 15

The true orbital period of Earth around the Sun, defined as the time taken to complete one orbit with respect to the background stars, is 1

Accepted Answer

A)   sidereal year.
B)   Gregorian year.
C)   tropical year.
D)   solar day.E) A) and B)
F) B) and D)

Question 16

Astronauts on the Moon look back at Earth, a distance of about 400,000 km. If the cities of Washington, D.C., and New York are separated by about 300 km, what will the angle between them be when viewed from the Moon?

Accepted Answer

A)   1.3°
B)   1300°
C)   2.5°
D)   2.5 arcminutesE) A) and D)
F) A) and B) D

Question 17

The motion of the Moon across the sky in 1 hour, as seen against the background of stars, is approximately

Accepted Answer

A)   its own diameter (1/2°) .
B)   1/10°.
C)   4°.
D)   13°.E) A) and D)
F) C) and D)

Question 18

Over an interval of 6 months, the tilt of Earth's spin axis with respect to the background stars will change by

Accepted Answer

A)   0°.
B)   23.5°.
C)   47°.
D)   180°.E) B) and C)
F) C) and D)

Question 19

Why are different phases of the Moon observable from Earth?

Accepted Answer

A)   The motion of the Moon in its orbit around Earth causes observers to see different amounts of Earth's shadow falling on the Moon.
B)   The motion of the Moon in its orbit around Earth causes observers to see different amounts of the sunlit side of the Moon.
C)   The distance of the Moon from Earth changes because of the elliptical orbit of the Moon, causing the sunlit side of the Moon to move relative to Earth.
D)   The rotation of the Moon around its own axis causes observers to see different amounts of the sunlit side of the Moon.E) A) and B)
F) A) and C)

Question 20

Which way does an observer move with respect to the stars because of the rotation of Earth?

Accepted Answer

A)   westward
B)   southward
C)   northward
D)   eastwardE) A) and B)
F) All of the above

Exam 1: Discovering the Night Sky

A science fiction writer, writing a story about inhabitants on Earth in 14,000 A.D. who have survived a disaster that included the loss of modern navigational aids, describes them traveling due north across barren wastes by walking toward Polaris, the pole star. What is wrong with this situation?

Correct AnswerverifiedShow Answer

What will be the elevation angle of the Sun above the horizon at midday on June 21 every year at latitude 66.5° S?

Correct AnswerverifiedShow Answer

Which one of these is NOT a zodiac constellation?

Correct AnswerverifiedShow Answer

The phase of the Moon when Sun and Moon are separated by 6 hours of right ascension is always

Correct AnswerverifiedShow Answer

Would a calendar based on a sidereal day be satisfactory?

Correct AnswerverifiedShow Answer

On December 21 of this year, the Sun will be at what declination angle?

Correct AnswerverifiedD

If the stars Polaris and Arcturus are seen to be 71° apart, as shown in Figure 1-5, how far away from Polaris is the closest star in Ursa Major?

Correct AnswerverifiedShow Answer

The angle subtended at an observer by a city transit bus (length 9 m) at a distance of 1000 m is close to

Correct AnswerverifiedShow Answer

During a total lunar eclipse, the Moon is

Correct AnswerverifiedD

How long will it take for precession to move Earth's spin axis to a position perpendicular to the ecliptic plane?

Correct AnswerverifiedShow Answer

If the plane of the Moon's orbit were the same as the ecliptic plane, there would be a lunar eclipse

Correct AnswerverifiedShow Answer

Solar eclipses (when the Moon and Sun are precisely in line) can be either total (Sun completely covered) or annular (Sun not quite covered) when viewed from the eclipse centerline. This is because

Correct AnswerverifiedShow Answer

What was the approximate value of right ascension of the Sun this year on December 21?

Correct AnswerverifiedShow Answer

One-billionth divided by one-millionth is equal to

Correct AnswerverifiedShow Answer

The true orbital period of Earth around the Sun, defined as the time taken to complete one orbit with respect to the background stars, is 1

Correct AnswerverifiedShow Answer

Astronauts on the Moon look back at Earth, a distance of about 400,000 km. If the cities of Washington, D.C., and New York are separated by about 300 km, what will the angle between them be when viewed from the Moon?

Correct AnswerverifiedD

The motion of the Moon across the sky in 1 hour, as seen against the background of stars, is approximately

Correct AnswerverifiedShow Answer

Over an interval of 6 months, the tilt of Earth's spin axis with respect to the background stars will change by

Correct AnswerverifiedShow Answer

Why are different phases of the Moon observable from Earth?

Correct AnswerverifiedShow Answer

Which way does an observer move with respect to the stars because of the rotation of Earth?

Correct AnswerverifiedShow Answer

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