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.

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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.

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1. According to paragraphs 1 and 2, what evidence leads astronomers to believe that all the planets formed at approximately the same time?? ??

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O Samples of rocks from all the planets are the same age.? ??

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O All the planets orbit the Sun in the same direction and in about the same plane.? ?

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O All planets have the same igneous and metamorphic processes.? ??

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O The gravitational field of each planet is about the same strength.

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2. Which of the following is NOT mentioned in paragraph 2 as a cause of constant change to Earth’s crust?? ??

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O Water? ??

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O Igneous processes? ??

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O Metamorphic processes? ??

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O Meteorites

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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).

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3. Which of the following can be inferred from paragraph 3 about meteorites?? ??

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O Their composition can help determine the part of the larger body from which they broke off.? ?

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O They are difficult to distinguish from rocks in Earth’s mantle.? ??

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O Their collisions with Earth have become more frequent than in the past.? ??

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O They are older than the rest of the solar system.

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4. According to paragraph 3, which of the following is a characteristic of asteroids?? ??

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O They are the largest meteors.? ?

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O They are made mostly of iron and other metals.? ??

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O They often collide with Earth.? ??

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O They are the oldest meteors.

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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.

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5. Which of the following can be inferred from paragraph 4 about the radiometric dating of meteorites?? ??

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O Scientists tried several different radiometric systems before finding one that worked.? ??

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O The radiometric dating of different meteorites produced similar results.? ?

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O Many meteorites were damaged by the radiometric dating.? ??

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O Radiometric dating was not as accurate as scientists expected.

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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?? ??

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O Radiometric dating has been proven to be reliable.? ??

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O The oldest rocks found on the surface of the Moon are the same age as the meteorites.? ?

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O No meteorites have been found that are younger than 4.6 billion years old.? ??

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O Meteorites on the Moon are the same age as those on other planets.

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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.

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7. Why does the author refer to “inflating a balloon with small coins attached to its surface”??

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O To help explain how the universe can expand while the galaxies remain the same size? ?

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O To imply that the universe must eventually stop expanding? ??

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O To support the statement that most stars are found in disk-shaped galaxies? ??

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O To help explain how the universe began as a single point of dense matter?

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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.

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8. According to paragraph 6, how did astronomers learn that the universe is expanding?? ??

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O By measuring the distance between galaxies? ??

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O By observing the movement of stars within galaxies? ??

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O By studying the wavelengths of light from distant galaxies? ?

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O By comparing the sizes of different galaxies

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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).?

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9. Look at the four squares [■] that indicate where the following sentence could be added to the passage.??

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Several varieties of meteorites have been observed.?

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Where would the sentence best fit? Click on a square [■] to add the sentence to the passage.

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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. Drag your choices to the spaces where they belong. To review the passage, click on View Text.?

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There is strong evidence that all the planets of our solar system were formed from the same disk of matter at the same time.

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Answer Choices

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O Determining the age of the planets by examining rocks on Earth is difficult because Earth’s crust is constantly changing.

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O Meteorites found on Earth and rocks from the Moon’s surface are the best evidence for estimating the age of the planets.

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O 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.

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O 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.

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O Radiometric dating of meteorites recovered from the Moon shows that they are older than those that are found on Earth.

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O The redshift phenomenon measures the rate at which the stars in a galaxy are moving away from each other.