Download FREE Sample Here

Full file at http://testbank360.eu/test-bank-astronomy-6th-edition-chaisson
Astronomy: A Beginner's Guide to the Universe, 6e (Chaisson/McMillan)
Chapter 0 Charting the Heavens: The Foundations of Astronomy
True/False Questions
1) Right ascension in the sky is very similar to latitude on the Earth.
Answer: FALSE
Diff: 1
Section Ref: 0.1
2) Latitude and right ascension are coordinate systems used to find objects on the celestial sphere.
Answer: FALSE
Diff: 1
Section Ref: 0.1
3) The celestial sphere is divided into 88 modern constellations.
Answer: TRUE
Diff: 1
Section Ref: 0.1
4) In the sky, declination is measured in degrees north or south of the celestial equator.
Answer: TRUE
Diff: 1
Section Ref: 0.1
5) The south celestial pole is located at a declination of -90 degrees.
Answer: TRUE
Diff: 1
Section Ref: 0.1
6) In general, the brightest star in a given constellation is designated as alpha.
Answer: TRUE
Diff: 1
Section Ref: 0.1
7) Constellations are close clusters of stars, all at about the same distance from the Sun.
Answer: FALSE
Diff: 1
Section Ref: 0.1
8) The closest terrestrial analog to hours of right ascension is angle of longitude.
Answer: TRUE
Diff: 2
Section Ref: 0.1
1
Copyright © 2010, 2007, 2004 Pearson Education, Inc.
Full file at http://testbank360.eu/test-bank-astronomy-6th-edition-chaisson
9) Over 20,000 stars are visible to the naked eye on the darkest, clearest nights.
Answer: FALSE
Diff: 2
Section Ref: 0.1
10) A star with a right ascension of 2.6 hrs will rise 2.6 hours after the vernal equinox.
Answer: TRUE
Diff: 3
Section Ref: More Prec. 0.1
11) A tropical year is the same as a sidereal year.
Answer: FALSE
Diff: 1
Section Ref: 0 2
12) The sidereal day is determined by the Earth's rotation with respect to the stars.
Answer: TRUE
Diff: 1
Section Ref: 0.2
13) The vernal equinox marks the beginning of spring in the northern hemisphere.
Answer: TRUE
Diff: 1
Section Ref: 0.2
14) There are 3,600 arc seconds in a degree.
Answer: TRUE
Diff: 2
Section Ref: More Prec. 0.1
15) An hour of right ascension corresponds to 60 degrees in the sky.
Answer: FALSE
Diff: 2
Section Ref: 0.2
16) From Earth, the Sun and Moon have about the same angular diameter.
Answer: TRUE
Diff: 1
Section Ref: 0.2
17) At the solstices, the Sun's declination will be 23.5 degrees from the equator.
Answer: TRUE
Diff: 2
Section Ref: 0.2
2
Copyright © 2010, 2007, 2004 Pearson Education, Inc.
Full file at http://testbank360.eu/test-bank-astronomy-6th-edition-chaisson
18) At the equinoxes, the declination of the Sun must be zero degrees.
Answer: TRUE
Diff: 2
Section Ref: 0.2
19) As it orbits the Earth, the Moon appears to move its own diameter (0.5 degrees) eastward every
hour.
Answer: TRUE
Diff: 3
Section Ref: 0.3
20) From full moon to third quarter moon takes about a week.
Answer: TRUE
Diff: 1
Section Ref: 0.3
21) Only people in the Moon's umbral shadow can see a total solar eclipse.
Answer: TRUE
Diff: 1
Section Ref: 0.3
22) If we are the Moon's penumbra, then we will see a partial lunar eclipse.
Answer: FALSE
Diff: 1
Section Ref: 0.3
23) There is a solar eclipse of some kind every new moon.
Answer: FALSE
Diff: 1
Section Ref: 0.3
24) Eighteen days past new moon, the Moon's phase is waning gibbous.
Answer: TRUE
Diff: 2
Section Ref: 0.3
25) A total solar eclipse will only occur when the new moon is both on the ecliptic and at its
greatest distance from Earth.
Answer: FALSE
Diff: 2
Section Ref: 0.3
26) The larger the parallax shift, the closer an object is to us.
Answer: TRUE
Diff: 1
Section Ref: 0.4
3
Copyright © 2010, 2007, 2004 Pearson Education, Inc.
Full file at http://testbank360.eu/test-bank-astronomy-6th-edition-chaisson
27) The parallax shift for all stars is very small.
Answer: TRUE
Diff: 1
Section Ref: 0.4
28) Increasing the baseline will increase the parallax angle.
Answer: TRUE
Diff: 3
Section Ref: 0.4
29) In the scientific method, it is not necessary to test your theory.
Answer: FALSE
Diff: 1
Section Ref: 0.5
Multiple-Choice Questions
1) Drawing on Eratosthenes' method, if two observers are due north and south of each other and are
separated by 400 km, what is the circumference of their spherical world if they see the same star on
their meridian at altitudes of 23 degrees and 47 degrees respectively, and at the exact same time?
A) 2,000 km
B) 4,000 km
C) 6,000 km
D) 8,000 km
E) 12,000 km
Answer: C
Diff: 3
Section Ref: 0.4
2) The star Wolf 1061 has a parallax of 2.34 arc seconds, while the star Ross 652 has a parallax of
1.70 arc seconds. What can you correctly conclude?
A) Both stars are outside the Milky Way galaxy.
B) Wolf 1061 must have a larger proper motion than Ross 652.
C) Ross 652 must have a larger proper motion than Wolf 1061.
D) Ross 652 is closer to Earth than Wolf 1061.
E) Wolf 1061 is closer to Earth than Ross 652.
Answer: E
Diff: 2
Section Ref: 0.4
4
Copyright © 2010, 2007, 2004 Pearson Education, Inc.
Full file at http://testbank360.eu/test-bank-astronomy-6th-edition-chaisson
3) The greatest distance above or below the ecliptic the Moon can move is
A) 5.2 degrees.
B) 23.5 degrees.
C) 27.3 degrees.
D) 29.5 degrees.
E) 30 degrees.
Answer: A
Diff: 3
Section Ref: 0.3
4) In an annular eclipse,
A) the Sun is totally blocked by the Moon.
B) the Moon is totally blocked by the Earth.
C) the Moon appears as a thin, bright ring.
D) the Sun appears as a thin, bright ring.
E) the Sun is partially blocked by the Earth.
Answer: D
Diff: 2
Section Ref: 0.3
5) If you are in the Earth's umbra, then
A) it must be a total solar eclipse.
B) it must be a lunar eclipse of some type.
C) it is night time.
D) the Sun is always visible.
E) the Moon is always visible.
Answer: C
Diff: 2
Section Ref: 0.3
6) The synodic month is
A) 29.5 days.
B) about two days shorter than the sidereal month.
C) based on the Moon's position relative to the stars.
D) the basis of the year we use in our modern calendar.
E) caused by both the Earth's and Moon's rotations.
Answer: A
Diff: 2
Section Ref: 0.3
5
Copyright © 2010, 2007, 2004 Pearson Education, Inc.
Full file at http://testbank360.eu/test-bank-astronomy-6th-edition-chaisson
7) If the Moon appears half lit, and is almost overhead about 6:00 AM, its phase is
A) waxing crescent.
B) first quarter.
C) full.
D) third quarter.
E) waning crescent.
Answer: D
Diff: 2
Section Ref: 0.3
8) If new moon fell on March 2nd, what is the Moon's phase on March 14th?
A) waxing crescent
B) first quarter
C) waxing gibbous
D) full
E) waning crescent
Answer: C
Diff: 2
Section Ref: 0.3
9) A solar eclipse can only happen during a
A) new moon.
B) solstice.
C) first quarter moon.
D) full moon.
E) perihelion passage of the Sun.
Answer: A
Diff: 2
Section Ref: 0.3
10) What will occur when the full moon is on the ecliptic?
A) a total lunar eclipse
B) a total solar eclipse
C) a partial solar eclipse
D) an annular lunar eclipse
E) a partial lunar eclipse if the Moon is at perigee
Answer: A
Diff: 1
Section Ref: 0.3
6
Copyright © 2010, 2007, 2004 Pearson Education, Inc.
Full file at http://testbank360.eu/test-bank-astronomy-6th-edition-chaisson
11) If you are in the Moon's umbral shadow, then you are witnessing
A) nighttime.
B) a total solar eclipse.
C) a total lunar eclipse.
D) a partial solar eclipse.
E) some kind of lunar eclipse.
Answer: B
Diff: 1
Section Ref: 0.3
12) The time for the Moon to orbit Earth, relative to the stars is
A) 23 hours, 56 minutes.
B) about 7 days.
C) 27.3 days.
D) 29.5 days.
E) 18 years, 11.3 days.
Answer: C
Diff: 1
Section Ref: 0.3
13) The interval from new Moon to first quarter is about a(n)
A) hour.
B) day.
C) week.
D) month.
E) year.
Answer: C
Diff: 1
Section Ref: 0.3
14) The star Thuban in Draco
A) lies as the center of the precession cycle.
B) was an excellent pole star in 3,000 BC.
C) is brighter than Polaris.
D) lies halfway between the bowls of the Big and Little Dippers.
E) is used to locate the vernal equinox.
Answer: B
Diff: 3
Section Ref: 0.2
7
Copyright © 2010, 2007, 2004 Pearson Education, Inc.
Full file at http://testbank360.eu/test-bank-astronomy-6th-edition-chaisson
15) If Scorpius is now prominent in the summer sky, in 13,000 years it will be best seen
A) at the same season; the heavens do not change.
B) in the autumn.
C) in the winter sky.
D) in the spring sky.
E) It will not be visible then at all. All of its stars will have vanished by then.
Answer: C
Diff: 3
Section Ref: 0.2
16) If Taurus is now rising at sunset, which constellation will rise at sunset next month?
A) Scorpius
B) Aquarius
C) Gemini
D) Aries
E) Pisces
Answer: C
Diff: 3
Section Ref: 0.2
17) The fact that the Earth has moved along its orbit in the time it took to rotate once is the reason
for
A) the difference between solar and sidereal time.
B) precession.
C) seasons.
D) the position of the Celestial Equator.
E) Earth's 23.5-degree tilt.
Answer: A
Diff: 3
Section Ref: 0 2
18) When the Moon is directly opposite the Sun in the sky, its phase is
A) new.
B) waxing or waning crescent.
C) first or third quarter.
D) waxing or waning gibbous.
E) full.
Answer: E
Diff: 2
Section Ref: 0 2
8
Copyright © 2010, 2007, 2004 Pearson Education, Inc.
Full file at http://testbank360.eu/test-bank-astronomy-6th-edition-chaisson
19) You note that a particular star is directly overhead. It will be directly overhead again in
A) 1 hour.
B) 12 hours.
C) 23 hours 56 minutes.
D) 24 hours.
E) 24 hours 4 minutes.
Answer: C
Diff: 2
Section Ref: 0 2
20) While watching a star, you see it moves 15 degrees across the sky. How long have you been
watching it?
A) 1 hour
B) 3 hours
C) 15 minutes
D) 15 seconds
E) 1 minute
Answer: A
Diff: 2
Section Ref: 0 2
21) That Polaris will not always be the pole star is due to
A) the sidereal day being shorter than the solar day.
B) precession shifting the celestial pole.
C) the Moon following the ecliptic, instead of the equator.
D) the Earth's revolution being slightly less than exactly 365.25 days.
E) the Solar winds blowing the Earth farther away from the Sun.
Answer: B
Diff: 2
Section Ref: 0.2
22) From the horizon to the observer's zenith is an angle of
A) 30 degrees for observers at a latitude of 30 degrees North.
B) 90 degrees for everyone on the Earth.
C) 23.5 degrees for observers at the Tropics of Cancer and Capricorn.
D) 66.5 degrees for everyone on the Earth.
E) 0.0 degrees for an observer at the Earth's north pole.
Answer: B
Diff: 1
Section Ref: 0.2
9
Copyright © 2010, 2007, 2004 Pearson Education, Inc.
Full file at http://testbank360.eu/test-bank-astronomy-6th-edition-chaisson
23) This diagram explains
A) the difference between solar time and sidereal time.
B) precession.
C) the solar day's relation to the Moon.
D) the sidereal day's relation to the seasons.
E) the reason for the solstices.
Answer: A
Diff: 1
Section Ref: 0 2
24) The 26,000 year cycle that changes the poles and equinoxes is called
A) a retrograde loop.
B) the Earth's rotation.
C) precession.
D) regression.
E) revolution.
Answer: C
Diff: 1
Section Ref: 0.2
10
Copyright © 2010, 2007, 2004 Pearson Education, Inc.
Full file at http://testbank360.eu/test-bank-astronomy-6th-edition-chaisson
25) The twelve constellations the solar system bodies move through are the
A) equatorial constellations.
B) signs of the zodiac.
C) nodes of the ecliptic.
D) galactic equator.
E) stages of heaven.
Answer: B
Diff: 1
Section Ref: 0.2
26) A star with a right ascension of 1.0 hours will rise
A) 1.0 hours before the vernal equinox.
B) 13.0 hours before the vernal equinox.
C) 1.0 hours after the vernal equinox.
D) 11.0 hours after the vernal equinox.
E) at the same time as the vernal equinox.
Answer: C
Diff: 3
Section Ref: 0.1
27) What are constellations?
A) Groups of galaxies gravitationally bound and close together in the sky.
B) Groups of stars making an apparent pattern in the celestial sphere.
C) Groups of stars gravitationally bound and appearing close together in the sky.
D) Ancient story boards, useless to modern astronomers.
E) Apparent groupings of stars and planets visible on a given evening.
Answer: B
Diff: 2
Section Ref: 0.1
28) A star with a declination of +60.0 degrees will be
A) east of the vernal equinox.
B) west of the vernal equinox.
C) north of the celestial equator.
D) south of the celestial equator.
E) None of these answers are correct.
Answer: C
Diff: 2
Section Ref: 0.1
11
Copyright © 2010, 2007, 2004 Pearson Education, Inc.
Full file at http://testbank360.eu/test-bank-astronomy-6th-edition-chaisson
29) Into how many constellations is the celestial sphere divided?
A) 12
B) 44
C) 57
D) 88
E) 110
Answer: D
Diff: 1
Section Ref: 0.1
30) In general, what is true of the alpha star in a constellation?
A) It is the brightest star in the constellation.
B) It is the easternmost star in the constellation.
C) It is the westernmost star in the constellation.
D) It is the reddest star in the constellation.
E) It is the star that is closest to Earth.
Answer: A
Diff: 1
Section Ref: 0.1
Fill-in-the-Blank Questions
1) Like latitude on Earth, ________ in the sky is measured in degrees north and south of the
equator.
Answer: declination
Diff: 1
Section Ref: 0.1
2) The twelve constellations through which the Sun passes are signs of the ________.
Answer: zodiac
Diff: 1
Section Ref: 0.2
3) The time interval of 365.242 days is defined as the ________.
Answer: tropical year
Diff: 1
Section Ref: 0.2
4) The time for the Moon to orbit the Earth, relative to the distant stars is the ________.
Answer: sidereal month
Diff: 1
Section Ref: 0.3
5) The apparent annual path the Sun takes through the sky is called the ________.
Answer: ecliptic
Diff: 1
Section Ref: 0.3
12
Copyright © 2010, 2007, 2004 Pearson Education, Inc.
Full file at http://testbank360.eu/test-bank-astronomy-6th-edition-chaisson
6) If the Moon rises at sunset, then its phase must be ________.
Answer: full
Diff: 2
Section Ref: 0.3
7) If the Moon is on the ecliptic, new, and at its farthest distance from Earth, we will get an
________ solar eclipse.
Answer: annular
Diff: 2
Section Ref: 0.3
8) Our seasons are a consequence of the Earth's 23.5 degree ________.
Answer: axial tilt
Diff: 1
Section Ref: 0.3
9) Over the course of the year, the Sun's noon altitude varies by ________ degrees.
Answer: 47
Diff: 2
Section Ref: 0.3
10) That we do not get eclipses every new and full Moon is due to the ________ degree tilt of the
Moon's orbit, relative to the ecliptic.
Answer: 5.2 (or just 5)
Diff: 2
Section Ref: 0.3
11) A distance of ten trillion kilometers in astronomy is called a ________.
Answer: light year
Diff: 1
Section Ref: 0.4
12) The apparent angular shift of any object across a distant background, when viewed from two
different places, is called ________ shift.
Answer: parallax or parallactic
Diff: 1
Section Ref: 0.4
13) Sirius has a parallax of 0.38", while Alpha Centauri's is 0.77". Alpha Centauri is about
________ as Sirius.
Answer: twice as close
Diff: 1
Section Ref: 0.4
14) If one star has a parallax ten times larger than another's, the first star is ________.
Answer: ten times closer than the second
Diff: 1
Section Ref: 0.4
13
Copyright © 2010, 2007, 2004 Pearson Education, Inc.
Full file at http://testbank360.eu/test-bank-astronomy-6th-edition-chaisson
15) If two observatories on opposite sides of the Earth were to measure the position of a star to
calculate its parallax, then the diameter of the Earth would be the ________.
Answer: baseline
Diff: 2
Section Ref: 0.4
16) One of the requirements of the Scientific Method is that an experiment must be ________.
Answer: repeatable
Diff: 1
Section Ref: 0.5
Short Answer Questions
1) What do both latitude on Earth and declination in the sky measure?
Answer: Angular distance in degrees above or below the geographical and celestial equators.
Diff: 1
Section Ref: 0.1
2) How is right ascension similar to longitude on Earth?
Answer: Both measure positions east or west from a fixed point; Greenwich on Earth, the vernal
equinox in the sky.
Diff: 1
Section Ref: 0.1
3) What are the minimum and maximum values for declination in the sky for both north and south?
Answer: From the equator at 0 degrees, to +90 degrees for the north celestial pole, and down to
-90 degrees for the south celestial pole.
Diff: 1
Section Ref: 0.1
4) How are right ascension in the sky and longitude on Earth different?
Answer: Right ascension is measured in units of time eastward from the vernal equinox, while
longitude is measured in degrees east or west of the Greenwich meridian.
Diff: 2
Section Ref: 0.1
5) Define the celestial sphere.
Answer: An imaginary hollow sphere, with Earth at its center, on which all the stars (and other
celestial bodies) are fixed. As the sphere rotates around the Earth, the stars move across our sky.
Diff: 2
Section Ref: 0.1
6) What are the minimum and maximum values for right ascension in the sky?
Answer: From 0 to 24 hours, going eastward from the vernal equinox.
Diff: 2
Section Ref: 0.1
14
Copyright © 2010, 2007, 2004 Pearson Education, Inc.
Full file at http://testbank360.eu/test-bank-astronomy-6th-edition-chaisson
7) Which is longer, the sidereal or solar day? By how much?
Answer: The solar day is approximately four minutes longer than the sidereal day.
Diff: 1
Section Ref: 0.2
8) At the solstice, what is the maximum distance (angle) the Sun can be above or below the
equator?
Answer: +23.5 degrees in summer and -23.5 degrees in winter.
Diff: 1
Section Ref: 0.2
9) How far above or below the ecliptic can the Sun move?
Answer: The Sun follows the ecliptic eastward across the sky, never leaving it.
Diff: 1
Section Ref: 0.2
10) If intending to teach his students the constellations by season, why would an astronomy
instructor be advised to always assign the stars in the current western sky at the beginning of each
term?
Answer: As the Earth revolves around the Sun, the Sun appears to move one degree eastward per
day. These stars are, therefore, soon lost in the Sun's glare.
Diff: 2
Section Ref: 0.2
11) Which star shows the least motion in the northern sky over the course of an hour?
Answer: Polaris, the North Star, lies within a degree of the celestial pole, and does not move
noticeably with the naked eye over an entire night.
Diff: 2
Section Ref: 0.2
12) Pensacola, Florida lies at a latitude of 30 degrees north. Where is Polaris in its sky?
Answer: 30 degrees high in the north
Diff: 3
Section Ref: 0.2
13) How far above or below the equator can the Sun appear to move? Why?
Answer: The Earth's axial tilt means the Sun's declination can reach 23.5 degrees north or south of
the equator at the solstices.
Diff: 1
Section Ref: 0.3
14) What happens on March 20th, and what does the name signify?
Answer: The vernal equinox, because the days and nights are approximately equal in length.
Diff: 1
Section Ref: 0.3
15
Copyright © 2010, 2007, 2004 Pearson Education, Inc.
Full file at http://testbank360.eu/test-bank-astronomy-6th-edition-chaisson
15) Why are some solar eclipses total, and others annular?
Answer: The Moon's orbit is not a perfect circle. When the Moon is closer to Earth, it is big
enough to cover the Sun completely; when it is too far away it appears smaller, so a ring of sunlight
is still seen.
Diff: 2
Section Ref: 0.3
16) What is the length of the sidereal month, and how is it determined?
Answer: It takes 27.3 days for the Moon to revolve around us and return to the same background
of stars.
Diff: 2
Section Ref: 0.3
17) How long does the synodic month take, and how it this observed?
Answer: The phase cycle of the Moon takes 29.5 days to return to exactly the same phase.
Diff: 2
Section Ref: 0.3
18) How far above and below the celestial equator can the Sun move?
Answer: The Sun never appears more than 23.5 degrees above or the below the celestial equator.
Diff: 2
Section Ref: 0.3
19) The first quarter moon rises about noon today; what will its phase be, and when will it rise
tomorrow?
Answer: It will be waxing gibbous, and rise about 1 PM by the next day.
Diff: 2
Section Ref: 0.3
20) The last quarter moon rises tonight about midnight; when will it rise, and what will its phase be
tomorrow night?
Answer: It will rise about an hour later, about 1 AM, and be a waning crescent by then.
Diff: 2
Section Ref: 0.3
21) If the Moon rises exactly at sunset, what will its phase be? Why?
Answer: The phase will be full because it is rising opposite the Sun. If the Moon is directly
opposite the Sun in the sky, its phase will be full.
Diff: 2
Section Ref: 0.3
22) Why is Polaris not always the pole star, and when does it get another chance?
Answer: Precession of the equinoxes cycles around every 26,000 years.
Diff: 3
Section Ref: 0.3
16
Copyright © 2010, 2007, 2004 Pearson Education, Inc.
Full file at http://testbank360.eu/test-bank-astronomy-6th-edition-chaisson
23) If Sirius transits my local meridian tonight at 6:43 PM, when will it transit tomorrow?
Answer: At 6:39 PM tomorrow night, as the Earth spins once in a sidereal day.
Diff: 3
Section Ref: 0.3
Essay Questions
1) Compare and contrast latitude and declination. How does each relate to your position on Earth?
Answer: Both are measured in degrees north or south of the equator, and are used to find positions
on the Earth or in the sky. If you are at latitude 30 degrees north, then the stars that pass through
your zenith (directly overhead) will have a corresponding declination of +30 degrees.
Diff: 2
Section Ref: 0.1
2) Compare and contrast longitude and right ascension.
Answer: Longitude is measured in degrees both east and west of the Greenwich meridian, but
right ascension is measured in units of time as the Earth rotates, and goes only eastward from the
vernal equinox.
Diff: 3
Section Ref: 0.1
3) Compare hours of Right ascension to time zones on the Earth.
Answer: Like time zones, hours of RA are 15 degrees wide, and they run eastward across the sky
from the Vernal Equinox, much like the time zones originate from the Prime Meridian.
Diff: 3
Section Ref: 0.1
4) The Sun and stars rise in the east, and set in the west. Contrast ancient and modern explanations
for this observation.
Answer: The ancients thought there was a vast celestial sphere, spinning over our heads once a
day, and that the stars, Sun, Moon, and planets are all carried along for the ride. We now recognize
it is the Earth itself that rotates eastward, creating this apparent westward motion of celestial
bodies.
Diff: 2
Section Ref: 0.2
5) Contrast the sidereal and solar days.
Answer: The Earth rotates once on its axis every 23 hours, 56 minutes, and thus turns to face the
same distant star in that interval. But we are also revolving around the Sun at one degree eastward
per day, hence the Sun appears to have moved eastward from one day to the next, and it takes a full
24 hours to align with the Sun again.
Diff: 2
Section Ref: 0.2
17
Copyright © 2010, 2007, 2004 Pearson Education, Inc.
Full file at http://testbank360.eu/test-bank-astronomy-6th-edition-chaisson
6) Why can many more people witness a total lunar eclipse than a total solar eclipse?
Answer: For a total solar eclipse to be seen, the observer must be in the Moon's umbra, a shadow
only about a hundred miles across, while everyone on the night side of the Earth can look up to
witness the full moon moving though our shadow.
Diff: 2
Section Ref: 0.3
7) What conditions are necessary for a total solar eclipse?
Answer: The Moon must be at new phase (directly between Earth and the Sun), it must also be
both at the closer distance in its orbit and on the ecliptic (crossing a node). Only people on those
parts of the Earth where the Moon's umbral shadow passes will see a total solar eclipse.
Diff: 2
Section Ref: 0.3
8) What is the astronomical significance of 26,000 years?
Answer: The Earth wobbles on its rotational axis over this precession cycle, which also changes
the location of the poles, equinoxes, and solstices in the sky.
Diff: 2
Section Ref: 0.3
9) Describe how Eratosthenes measured the circumference of our planet.
Answer: Using the fact that the noon solstice Sun was directly overhead at Syene, on the Tropic of
Cancer, yet was 7 degrees south of his zenith in Alexandria, Eratosthenes realized this was due to
the curvature of the Earth, and that the 7 degrees was about 1/50th of the Earth's total
circumference, so the Earth must be about fifty times larger in circumference than the 800
kilometer separation between Alexandria and Syene, or about 40,000 kilometers around.
Diff: 3
Section Ref: 0.3
10) Which is longer, the sidereal or synodic month? Why?
Answer: The synodic month takes an extra two days, because the Earth is also revolving around
the Sun, so after 27.3 days the Moon returns to the same place among the stars, but the Earth has
revolved about 27 degrees ahead of where it was last month; it takes the Moon two days to catch up
to us.
Diff: 3
Section Ref: 0.3
11) We get a new and full moon every month. Why don't we get two eclipses every month?
Answer: The Moon's orbit is tilted 5.2 degrees to the Earth's orbit (the ecliptic), and the disks of
the Sun and Moon are only about .5 degrees wide. Most months the new and full moon pass too far
from the ecliptic for the Earth's and Moon's shadows to make eclipses occur.
Diff: 3
Section Ref: 0.3
18
Copyright © 2010, 2007, 2004 Pearson Education, Inc.