Download GLY 1001 Answers to Chapter 21 Review Questions

GLY 1001 Answers to Chapter 21 Review Questions
1. The close association of the positions of the celestial objects with recurring events on Earth,
such as the seasons, led the ancients to believe that all Earthly activity was controlled by the
celestial objects.
2. Retrograde motion occurs when Earth, which travels faster than Mars, passes Mars, which
makes Mars appear to be going backward. Rather than using one circle for an orbit, Ptolemy
placed the planet on a small circle (epicycle), which revolved around a large circle (deferent).
By trial and error he was able to select just the right combinations of circles to produce the
amount of retrograde motion observed for each planet.
3. Copernicus placed the Sun at the center of the solar system. Next to the theory of organic
evolution, this proposal perhaps most disrupted the human concept of our role in the
universe.
4. Tycho Brahe's greatest contribution to science was his accurate observations of Mars that
were later used by Kepler to determine the three laws of planetary motion.
5. Earth moves most rapidly in January (perihelion). Therefore, the longest solar days occur at
this orbital position, because it takes Earth more time to go from one high noon to the next.
6. (a) 31.6 years (1000)
(b)
7. (a) 2.9 AU (25)
(b) 4.6 AU (100)
8. No; however, he was the first to use it astronomically.
9. A rotating Earth is necessary in the Copernican system; however, it was believed that Earth
would fly apart if it rotated. Hence, if the Sun could rotate and remain intact, so could Earth.
10. (Diagrams will vary) Venus will be full when it is on the opposite side of the Sun from Earth,
a configuration that could not happen in the Ptolemaic system.
11. The orbits of the planets are the result of gravitation and inertia. (Inertia is the tendency of a
moving body to travel in a straight line unless acted on by an outside force.)
12. Constellations provide astronomers with a means of dividing the sky into identifiable regions.
13. Earth takes 23 hours and 56 minutes to make one rotation with respect to a star, a period of
time called the sidereal day. However, Earth must rotate another 4 minutes to return to the
noon position with respect to the Sun, a period of time called the mean solar day, which
averages about 24 hours.
14. 29.5 days, the synodic month
15. The left edge of the Moon will be illuminated during the crescent phase that precedes the
new-Moon phase; t he right-edge will be illuminated during the crescent phase that follows
the new-Moon phase.
16. First-quarter phase; full-Moon phase
17. The visible Moon will be waxing (growing) because the cycle is progressing from new Moon
to first-quarter phase.
18. The same lunar hemisphere always faces Earth.
19. The slow lunar rotation, along with the absence of an atmosphere, accounts for the high
surface temperature of 127°C (261°F) on the day-side of the Moon and the low surface
temperature of –173°C
(–280°F) on its night side.
20. The Moon is directly between Earth and the Sun during a solar eclipse. During a lunar eclipse
the Moon is in the shadow of Earth because Earth is directly between the Moon and the Sun.
In both cases the Moon must also be in the plane of the ecliptic.
21. The maximum number of eclipses in one year is seven; the minimum number is two.
22. A total eclipse of the Moon can last up to 4 hours and is visible to anyone on the side of Earth
facing the Moon. During a total solar eclipse, the Moon casts a shadow that is never wider
than 275 kilometers. Only those observing in this narrow region will see the Moon cover the
complete solar disk for about 7 minutes.
23. A total eclipse of the Moon can last up to 4 hours. A total eclipse of the Sun lasts for at most
7 minutes.
Answers to Earth System Questions
1. Because interplanetary space is essentially a vacuum, the difference between perihelion and
aphelion of about 3 million miles has little influence on the quantity of radiation received by
Earth. Considering that the primary cause of the seasons, the amount of solar energy received
by any place on Earth on any day, and hence temperature is due to the angle (intensity) of the
Sun’s rays and the length of daylight and not Earth’s distance from the Sun, any changes in
summer or winter temperatures would be minimal. Consequently, the overall impact on the
biosphere and hydrosphere would be negligible.
2. Perhaps the two most obvious interactions between the Earth and Moon are gravity and the
light cast on Earth during the brighter phases of the Moon. Without the gravitational
interaction there would be no tidal effects on Earth. Ocean tides would not exist; the heat
exchange between the ocean and atmosphere would be altered, and hence atmospheric
heating and circulation would be modified; the tidal influence on the solid Earth would not
exist; and because of the lack of ocean tides, ocean life, especially that in today’s tidal areas
and shallow waters, would be different. Without a Moon and the light it casts, the lives of
nocturnal animals would be altered as well as the migratory habits of some species.