[ 作业 – 0 ]
Background for the Industrial Revolution
Paragraph 1:
The Industrial Revolution had several roots, one of which was a commercial revolution that, beginning as far back as the sixteen century, accompanied Europe’s expansion overseas. Both exports and imports showed spectacular growth, particularly in England and France. An increasingly larger portion of the stepped-up commercial activity was the the result of trade with overseas colonies. Imports included a variety of new beverages, spices, and foodstuffs. At the same time, a growing export market took European textiles, hardware, firearms, ships, and ships’ goods around the world and brought money flowing back. Europe’s economic institutions, particularly those in England, were strong, had wealth available for new investment, and seemed almost to be waiting for some technological breakthrough that would expand their profit-making
potential
even more.
Paragraph 2:
That breakthrough came in Great Britain, where several economic advantages created a climate especially favorable to the encouragement of new technology. One was its geographic location at the crossroads of international trade. Internally,
Britain was endowed with easily navigable natural waterways, which helped its trade and communication with the world.
Beginning in the 1770’s, it enjoyed a boom in canal building, which helped make its domestic markets more accessible. Because water transportation was the cheapest means of carrying goods to market, canals reduced prices and thus increased consumer demand.
Great Britain also had rich deposits of coal
that fed the factories springing up in industrial areas and iron ore that provided the raw material for manufacture of railroad equipment, tools, and a variety of industrial and consumer goods.
1.Select the TWO answer choices that according to paragraph 2,
enabled the development of British technology
. To receive credit you must select TWO answer choices.
A. An accessible water
transportation
system
B. A mild
climate
and plenty of fresh
water
C. The availability of newly developed international
technology
D. A
fuel
supply that supported industrial growth.
Paragraph 3:
Another advantage was Britain’s large population of rural, agricultural wage earners, as well as cottage workers,
who had the potential of being more mobile than peasants of some other countries.
Eventually they found their way to the cities or mining communities and provided the human power upon which the Industrial Revolution was built. The British people were also consumers, the absence of internal tariffs, such as those that existed in France or Italy or between the German states, made Britain the largest free-trade area in Europe. Britain’s relatively stable government also helped created an atmosphere
conducive to
industrial progress.
2.Paragraph 3 suggests that the Industrial Revolution did
not
originate outside
Great Britain because
A. the
labor
force in other countries could not as easily
relocate to cities
B. worker in
other
countries preferred working
independently
rather than in groups
C. there was a
lack
of
cooperation
between agricultural and cottage workers in other countries
D.
governments
in other countries placed limits on economic gain
Paragraph 4:
Great Britain’s better-developed banking and credit system also helped speed the industrial process, as did the fact that is was the home of an impressive array of entrepreneurs and inventors. Among them were a large number of nonconformists whose religious principles encouraged thrift and industry rather than luxurious living and who tended to pour their profits back into their businesses, thus providing the basis for continued expansion.
Paragraph 5:
A precursor to the Industrial Revolution was a revolution in agriculture techniques. Ideas about agricultural reform developed first in Holland, where as early as the mid-seventeenth century, such modern methods as crop rotation, heavy fertilization, and diversification were all in use. Dutch peasant farmers were known throughout Europe for their agricultural innovations,
but
as British markets and opportunities grew, the English quickly learned from them. As early as the seventeenth century the Dutch were helping them drain marshes and fens where, with the help of advanced techniques, they grew new crops. By the mid-eighteenth century new agriculture methods as well as selective breading of livestock had caught on throughout the country.
3. Why does the author mention
Dutch farming methods
in paragraph 5?
A. To emphasize that Great Britain was
not
the
only country
capable of rapid agricultural progress
B. To demonstrate British
resourcefulness
in adopting economically profitable agricultural reforms
C. To give an
example
of a European country with a powerful peasant workforce
D. To suggest that the Dutch agricultural system was
influenced
by British farming methods
Paragraph 6:
Much of the increased production was
consumed
by Great Britain’s burgeoning population.
At the same time, people were moving to the city, partly because of the enclosure movement; that is, the fencing of common fields and pastures in order to provide more
compact
, efficient, privately held agricultural parcels that would produce more goods and greater profits.
In the sixteenth century enclosures were usually used for creating sheep pastures, but by the eighteenth century new farming techniques made it advantageous for large landowners to seek enclosures in order to improve agricultural production.
Between 1714 and 1820 over 6 million acres of English land were enclosed.
As a result, many small, independent farmers were forced to sell out simply because they could not compete.
Nonlandholding peasants and cottage workers, who worked for wages and grazed cows or pigs on the village common, were also hurt when the common was no longer available. It was such people who began to flock to the cities seeking employment and who found work in the factories that would transform the nation and, eventually, the world.
4. The word “
consumed
” in the passage is closest in meaning to
A. wasted
B. grown
C. stored
D. eaten
5. The author uses the word “
compact
” in the passage to indicate that after the enclosure movement, agricultural parcels would be
A. smaller
B. productive
C. convenient
D. numerous
6. Paragraph 6 suggests which of the following about land enclosure?
A. It entered a period of steady
decline
after 1820.
B. It was a farming
reform
caused by industrialization.
C. It included a range of
agricultural activities
by the eighteenth century.
D. It was primarily used to
provide sheep pastures
in the sixteen century.
7. According to paragraph 6, the growth of the workforce in British factories was influenced by
A. the
competition
for jobs between established and new city inhabitants
B. a decrease in the farming
profits
of large landowners
C. the
failure
of small independent farms
D. an
attempt
by large landowners to take control of the cities
8. The author presents information in the passage mainly by
A. contrasting the development of industrialism in different countries
B. explaining a new theory about the origins of the Industrial Revolution
C. analyzing the consequences of European industrialism
D. expanding the reasons why industrialism began in Great Britain
Paragraph 6:
Much of the increased production was consumed by Great Britain’s burgeoning population. At the same time, people were moving to the city, partly because of the enclosure movement; that is, the fencing of common fields and pastures in order to provide more compact, efficient, privately held agricultural parcels that would produce more goods and greater profits. In the sixteenth century enclosures were usually used for creating sheep pastures, but by the eighteenth century new farming techniques made it advantageous for large landowners to seek enclosures in order to improve agricultural production. Between 1714 and 1820 over 6 million acres of English land were enclosed. █ As a result, many small, independent farmers were forced to sell out simply because they could not compete. █Non-landholding peasants and cottage workers, who worked for wages and grazed cows or pigs on the village common, were also hurt when the common was no longer available. █ It was such people who began to flock to the cities seeking employment and who found work in the factories that would transform the nation and, eventually, the world.
█
Look at the four squares [█
]that indicate where the following sentence could be added to the passage
Cities would not only provide job opportunities but also profoundly affect social patterns, standards of living, political movements, and ideologies.
Where would the sentence best fit?
Directions:
An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage.
This question is worth 2 points.
The Industrial Revolution was the result of far-reaching economic changes in Great Britain and Europe.
Answer Choices
A.The expansion of international trade from the sixteenth century on greatly stabilized the European economy.
B. Canals in eighteenth-century Great Britain played a more important role than did railroads in increasing internal trade.
C. Intense consumer activity and sound government institutions enabled mechanized labor to develop in Great Britain.
D. British entrepreneurs invented a new system of banking that led to rapid economic growth.
E. A thriving cottage industry was able to successfully compete with the factory system.
F. An increasingly efficient agricultural industry freed British workers for factory employment.
[ 作业 – 1 ]
Olmec Art
Paragraph 1
The earliest Mesoamerican art and architecture
/
to combine
ideological
complexity, craft, and permanence
/
was
that
of the Olmecs, whose civilization flourished between about 1500 B.C. and 100 B.C. The early Olmecs established major ceremonial centers along the rich lowlands of the modern Mexican states of Veracruz and Tabasco.
At distant Teopantecuanitlan, the Olmecs established a
sacred precinct
, the first monumental evidence of the Olmecs in the highlands.
But the Olmecs had an advanced social and economic system, with networks for commerce extending far to the west and south.
The fertile gulf plain probably allowed for an agricultural surplus, controlled by only a handful of individuals.
From the art and architecture of their ceremonial centers (we know too little about Olmec domestic life to call their sites cities), it is clear that for the Olmecs,
social
stratification
was sufficiently advanced for their society
to place great importance on the records of specific individuals, particularly in the form of colossal heads (enormous stone sculptures of human heads and faces).
ideological adj. 意识形态的;思想体系的;观念形态的
sacred adj. 神圣的;神的;上帝的;受尊重的;受崇敬的
precinct n. 选区;警区;派出所;（建筑物等的）外围，围墙内区域;步行商业区;分区警察局
stratification n. 分层;成层
colossal adj. 巨大的;庞大的
1. The word “
that
” in the passage refers to
A. Mesoamerican art and architecture
B. the ideological complexity, craft, and permanence
C. the earliest civilization
D. the permanent art and architecture
2. Paragraph 1
supports
which of the following ideas about Olmec society
A. Major artists and successful traders had roughly
equal
status.
B. The most important
members
of Olmec society
resided
in the
highlands
.
C. More people were engaged in producing monumental
works of
art
than
were engaged in
agriculture
.
D. There was a
well-developed social structure
in which some individuals held more
power
than
others.
S： 推理题
supports
D：
SG：
Paragraph 2
Long before modern radiocarbon dating testified to the antiquity of this culture, archaeologists and art historians had become aware of the power of Olmec art through individual objects. Some even identified the Olmec culture as the oldest of Mesoamerican civilizations, perhaps a mother culture from which all others derived, as the art historian Miguel Covarrubias once thought. Eventually the antiquity of Olmec culture was confirmed, and today many important elements of Mesoamerican art and architecture can be seen to have had a probable Olmec origin: ball courts, pyramids, portraiture, and mirrors. Some later Mesoamerican deities probably derive from Olmec gods, and even the famous “Maya” calendar was already in use by peoples in the Olmec area at the dawn of Maya civilization.
3. The
author
put the word Maya in
quotation marks
in order to
indicate that
A. few Mesoamericans were familiar with the Maya calendar
B. the calendar commonly attributed to the Maya was not actually developed by them
C. the names of Mesoamerican gods were included in the Maya calendar
D. it is doubtful that the Olmec and the Maya used the same calendars
S：目的题
D：
S：
G：
Paragraph 3
One of the first important Olmec objects to come to modern attention was the Kunz axe, acquired in the 1860s in Oaxaca, Mexico.
The ceremonial
axe puzzled and intrigued investigators
for years
because
on the one hand, it was clearly neither Aztec nor Maya, the best-known ancient Mesoamerican cultures, and in fact it had no features that could be linked with any known civilization,
while
on the other hand, it had surely been made in Mesoamerica in antiquity.
4. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage?Incorrect choices change the meaning in important ways or leave out essential information.
antiquity n. 古董;文物;古物;古代(尤指古希腊和古罗马时期);古老;古迹;古
A. Because the Kunz axe could not be linked with known Mesoamerican cultures of antiquity, investigators concluded that it was neither Aztec nor Maya.
B. The ceremonial axe puzzled and intrigued investigators because it was neither Aztec nor Maya, nor was it from any other ancient Mesoamerican civilization.
C. On the one hand the ceremonial axe was puzzling because it was not Aztec or Maya, and on the other hand it was intriguing because no other Mesoamerican culture made ceremonial axes.
D. The Kunz axe puzzled investigators for years because,
although
it was clearly made in ancient Mesoamerica, it could not be attributed to any known Mesoamerican culture.
Paragraph 4
The axe (exhibits) many qualities of the style we now call Olmec
: precious blue-green translucent
jade
, worked to reveal a
figure
in both two and three dimensions.
More than half the axe is devoted to the creature’s face an open, toothless mouth, and closely set,
slanting
eyes which has often been likened to the face of a howling human infant.
The creature’s hands are worked in lower relief, and in them he grasps a miniature version of himself. Feet and toes are indicated only by incision (carved lines), and incision also marks the face, ears, and upper body, perhaps to suggest tattooing, ear ornaments, and a tunic. For over two millennia this large, precious axe was presumably kept as a treasure or heirloom. It was not until 1955, after several seasons of excavation at La Venta had produced many fine jade objects and a convincing series of radiocarbon dates in the first millennium B.C., that objects such as the Kunz axe were at last understood by scholars to
embody
the principles of the first great art style of Mesoamerica.
jade n. 玉;翡翠;玉器;碧玉;玉制品;绿玉色;翡翠色
figure n.（书中的）图，表;人物;人 v. 是…的部分;计算(数量或成本);认为，认定
devoted v. 献(身);奉献，投入
slanting adj. 斜的;歪的;不平的;不直的
5. The word “
embody
” in the passage is closest in meaning to
A. utilize
B. reveal
C. incorporate
D. clarify
6. It can be
inferred
from paragraph 4 that the author provides a very detailed description of the Kunz axe
because
A. the Kunz axe is
more like later Mesoamerican art
than
it is like
Olmec
art
B. the Kunz axe is a
characteristic example of
Olmec
artistic style and principles
C. the Kunz axe is the
single most important and valuable
piece of Olmec art so far discovered
D. the
face
of the creature represented on the Kunz axe
resembles
a human
infant
S： 推理题 inferred because 问原因
D：
SG：
Paragraph 5
Early scholars of the Olmec style noticed a pattern of imagery repeated on many of the carved stone objects. Many howling baby faces were found, and other faces seemed to combine the features of humans and jaguars (large cats). Today, while the presence of jaguar imagery is still acknowledged, scholars have discovered that aspects of many other tropical rainforest fauna can be identified in the carvings. The caiman (a kind of alligator), eagle, toad, jaguar, and snake all appear in the Olmec supernatural repertoire. Anthropologist Peter David Joralemon has suggested that most of the motifs and images can be allocated to a few Olmec deities.
The paw-wing motif, for example, can be shown to be an element of the winged dragon, itself perhaps derived from the eagle and caiman.
This whole intricate symbolic code appears to have been in use from the first appearance of the Olmecs, and to have been employed consistently for a thousand years.
7. In paragraph 5, the
author
uses the example of the
paw-wing motif
in order to
illustrate
A. how Olmec images may be related to a few Olmec deities
B. why jaguar imagery is the most important of Olmec animal imagery
C. the importance of the paw-wing motif in cultures before the Olmec
D. how images of animals from beyond the rainforest were represented in Olmec art
S：目的题
D：
S：
G：
8. According to paragraph 5, which of the following is
true
about the Olmec symbolic code
A. It included
only animals that have paws or wings
.
B. It did
not change significantly
from one century to the next.
C. It was
not
strongly connected to
Olmec
religion.
D. It developed gradually
over a thousand-year period
.
S： 排除题
true
D：
SG：
Paragraph 2
Long before modern radiocarbon dating testified to the antiquity of this culture, archaeologists and art historians had become aware of the power of Olmec art through individual objects.
[ ]
Some even identified the Olmec culture as the oldest of Mesoamerican civilizations, perhaps a mother culture from which all others derived, as the art historian Miguel Covarrubias once thought.
[ ]
Eventually the antiquity of Olmec culture was confirmed, and today many important elements of Mesoamerican art and architecture can be seen to have had a probable Olmec origin: ball courts, pyramids, portraiture, and mirrors.
[ ]
Some later Mesoamerican deities probably derive from Olmec gods, and even the famous “Maya” calendar was already in use by peoples in the Olmec area at the dawn of Maya civilization.
[ ]
9. Look at the four squares that indicate where the following sentence could be added to the passage.
But these opinions lacked proof.
Where would the sentence best fit Click on a square to add the sentence to the passage.
10. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.
The Olmec culture was identified as the oldest of Mesoamerican civilizations, perhaps a mother culture from which
all others derived.
Answer Choices
A. Between 1500 B.C. and 100 B.C., the Olmecs developed complex ceremonial centers, an extensive agricultural and trading economy, and a highly distinctive art.
B. Early in their history, the Olmec left the fertile gulf plain and moved to Teopantecuanitlan.
C. The frequent reappearance of Olmec images in the art of the Maya and Aztecs suggests that the Olmecs gave rise to these later civilizations.
D. The Kunz axe, once linked with Maya culture after being found at an ancient Maya site, was eventually attributed to Olmec artists.
E. Many cultural innovations are now attributed to the Olmecs that were once attributed to other Mesoamerican cultures, including the calendar used by the Maya.
F. Olmec art involved a complex symbolic code, including various animal images and the howling baby seen on the Kunz axe and elsewhere, that was used consistently for a thousand years.
[ 作业 – 2 ]
Determining the Ages of the Planets and the Universe
Paragraph 1
The planets of our solar system all revolve around the Sun in the
same direction
and
in
orbits
that lie in nearly the same plane.
This
is strong evidence that the planets formed simultaneously from a single disk of material that rotated in the same direction as the modern planets.
Paragraph 2
Precisely when the planets came into being has been a difficult issue to resolve.
While Earth’s
water
is necessary for life
, its abundance near the planet’s surface makes rapid erosion inevitable.
Continuous alteration of the crust by erosion and also by
igneous
(volcanic) and
metamorphic
(pressure and heat within Earth) processes makes unlikely any discovery of rocks nearly as old as Earth.
Thus, geologists have had to look beyond this planet in their efforts to date Earth’s origin. Fortunately, we do have samples of rock that appear to represent the primitive material of the solar system. These samples are meteorites, which originate as extraterrestrial objects, called meteors, that have been captured in Earth’s gravitational field and have then crashed into our planet.
1. According to paragraphs 1 and 2,
what evidence
leads astronomers to
believe
that all the
planets formed at approximately the same time
?
A. Samples of rocks from all the planets are the same age.
B. All the planets orbit the Sun in the same direction and in about the same plane.
C. All planets have the same igneous and metamorphic processes.
D. The gravitational field of each planet is about the same strength.
S：细节题 问原因
believe planets formed at approximately the same time
D：
S：
G：
2. Which of the following is
NOT
mentioned in paragraph 2 as a cause of
constant change
to Earth’s crust?
A. Water
B. Igneous processes
C. Metamorphic processes
D. Meteorites
S：排除题
NOT 问原因 constant change
D：
SG：
Paragraph 3
Some meteorites consist of rocky material and, accordingly, are called stony meteorites. Others are metallic and have been designated iron meteorites even though they contain lesser amounts of elements other than iron. Still others consist of mixtures of rocky and metallic material and thus are called stony-iron meteorites.
Meteors come in all sizes, from small particles to the small planets known as asteroids;
no asteroid, however, has struck Earth during recorded human history. Many meteorites appear to be fragments of larger bodies that have undergone collisions and broken into pieces. Iron meteorites are fragments of the interiors of these bodies, comparable to Earth’s core, and stony meteorites are from outer portions of these bodies, comparable to Earth’s mantle (the layer between the core and outer crust).
3. Which of the following can be
inferred
from paragraph 3 about
meteorites
?
A. Their
composition
can help
determine
the part of the larger body from which they broke off.
B. They are
difficult to distinguish
from rocks in Earth’s mantle.
C. Their
collisions with Earth have become more frequent
than in the past.
D. They are
older than
the rest of the solar system.
S：推理题
inferred
meteorites
D：
SG：
4. According to paragraph 3, which of the following is a characteristic of asteroids?
A. They are the largest meteors.
B. They are made mostly of iron and other metals.
C. They often collide with Earth.
D. They are the oldest meteors.
S：细节题 characteristic of asteroids
D：
S：
G：
Paragraph 4
Meteorites have been radiometrically dated by means of several decay systems, including rubidium-strontium, potassium-argon, and uranium-thorium.
The dates thus derived tend to cluster around 4.6 billion years, which suggests that this is the approximate age of the solar system.
After many meteorites had been dated, it was gratifying to find that the oldest ages obtained for rocks gathered on the surface of the Moon also were approximately 4.6 billion years. This must, indeed, be the age of the solar system. Ancient rocks can be found on the Moon because the lunar surface, unlike that of Earth, has no water to weather and erode rocks and is characterized by only weak movements of its crust.
5. Which of the following can be
inferred
from paragraph 4 about the
radiometric dating of meteorites
?
A. Scientists
tried several different radiometric
systems before finding one that worked.
B. The radiometric dating of different meteorites produced
similar results
.
C. Many
meteorites were damaged by
the radiometric dating.
D. Radiometric dating was
not as accurate as scientists expected
.
S：推理题
inferred
radiometric dating of meteorites
D：
SG：
6. According to paragraph 4, why are scientists confident that the age of the oldest meteorites they studied is also the age of the solar system?
A. Radiometric dating has been proven to be reliable.
B. The oldest rocks found on the surface of the Moon are the same age as the meteorites.
C. No meteorites have been found that are younger than 4.6 billion years old.
D. Meteorites on the Moon are the same age as those on other planets.
S：细节题 问原因
why
age
D：
S：
G：
Paragraph 5
Determining the age of the universe has been more complicated. Most stars in the universe are clustered into enormous disk-like galaxies. The distance between our galaxy, known as the Milky Way, and all others is increasing. In fact, all galaxies are moving away from one another, evidence that the universe is expanding. It is not the galaxies themselves that are expanding but the space between them. What is happening is analogous to
inflating a balloon with small coins attached to its surface
. The coins behave like galaxies: although they do not expand, the space between them does. Before the galaxies formed, matter that they contain was concentrated with infinite density at a single point from which it exploded in an event called the big bang. Even after it assembled into galaxies, matter continued to spread in all directions from the site of the big bang.
7. Why does the author refer to “inflating a balloon with small coins attached to its surface”?
A. To help explain how the universe can expand while the galaxies remain the same size
B. To imply that the universe must eventually stop expanding
C. To support the statement that most stars are found in disk-shaped galaxies
D. To help explain how the universe began as a single point of dense matter
S：The author 目的题
D：阴影
S：阴影标红
G：C 答案标红
Paragraph 6
The evidence that the universe is expanding makes it possible to estimate its age.
This evidence, called the redshift, is an increase in the wavelengths of light waves traveling through space—a shift toward the red end of the visible spectrum of wavelengths.
Expansion of the space between galaxies causes this shift by stretching light waves as they pass through it. The farther these light waves have traveled through space, the greater the redshift they have undergone. For this reason, light waves that reach Earth from distant galaxies have larger redshifts than those from nearby galaxies. Calculations based on these redshifts indicate that about 13.7 billion years ago all of the galaxies would have been at one spot, the site of the big bang. This, then, is the approximate date of the big bang and the age of the universe.
8. According to paragraph 6, how did astronomers learn that the
universe is expanding
?
A. By measuring the distance between galaxies
B. By observing the movement of stars within galaxies
C. By studying the wavelengths of light from distant galaxies
D. By comparing the sizes of different galaxies
S：细节题 how 问原因
universe is expanding
D：
S：
G：
Paragraph 3
[ ]
Some meteorites consist of rocky material and, accordingly, are called stony meteorites.
[ ]
Others are metallic and have been designated iron meteorites even though they contain lesser amounts of elements other than iron.
[ ]
Still others consist of mixtures of rocky and metallic material and thus are called stony-iron meteorites.
[ ]
Meteors come in all sizes, from small particles to the small planets known as asteroids; no asteroid, however, has struck Earth during recorded human history. Many meteorites appear to be fragments of larger bodies that have undergone collisions and broken into pieces. Iron meteorites are fragments of the interiors of these bodies, comparable to Earth’s core, and stony meteorites are from outer portions of these bodies, comparable to Earth’s mantle (the layer between the core and outer crust).
9. Look at the four squares
[ ]
that indicate where the following sentence could be added to the passage.
Several varieties of meteorites have been observed.
Where would the sentence best fit?
10. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some answer choices do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.
There is strong evidence that all the planets of our solar system were formed from the same disk of matter at the same time.
Answer Choices
A. Determining the age of the planets by examining rocks on Earth is difficult because Earth’s crust is constantly changing.
B. Meteorites found on Earth and rocks from the Moon’s surface are the best evidence for estimating the age of the planets.
C. The expansion of the universe makes it possible to estimate its age by measuring the amount of the redshift of light coming from distant galaxies.
D. All three kinds of meteorites are similar in composition to Earth in that they have an inner core, a rocky mantle, and an outer crust.
E. Radiometric dating of meteorites recovered from the Moon shows that they are older than those that are found on Earth.
F. The redshift phenomenon measures the rate at which the stars in a galaxy are moving away from each other.