Astronomy Ch. 1 Practice Test – Flashcards
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Which of the following has your "cosmic address" in the correct order?
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You, Earth, solar system, Milky Way Galaxy, Local Group, Local Supercluster, universe
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When we look at an object that is 1,000 light-years away we see it _________.
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as it was 1,000 years ago
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Suppose we look at two distant galaxies: Galaxy 1 is twice as far away as Galaxy 2. In that case _________.
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we are seeing Galaxy 1 as it looked at an earlier time in the history of the universe than Galaxy 2
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Could we see a galaxy that is 20 billion light-years away? (Assume that we mean a "lookback time" of 20 billion years.)
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No, because it would be beyond the bounds of our observable universe.
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Suppose we make a scale model of our solar system, with the Sun the size of a grapefruit. Which of the following best describes what the planets would look like?
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The planets are all much smaller than the Sun. Four planets are within about 20 meters of the Sun, while the rest planets are spread much farther apart.
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If you could count stars at a rate of about one per second, how long would it take to count all the stars in the Milky Way Galaxy?
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Several thousand years
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The total number of stars in the observable universe is about _________.
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the same as the number of grains of sand on all the beaches on Earth
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Using the ideas discussed in your textbook, in what sense are we "star stuff"?
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Nearly every atom from which we are made was once inside of a star.
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How are galaxies important to our existence?
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Galaxies recycle material from one generation of stars to the next, and without this recycling we could not exist.
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If we imagine the history of the universe compressed into one year, dinosaurs became extinct _________.
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yesterday morning
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Relative to the age of the universe, how old is our solar system?
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It is about one-third the age of the universe.
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How do the speeds at which we are moving with Earth's rotation and orbit compare to the speeds of more familiar objects?
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Earth's rotation carries most people around the axis faster than a commercial jet travels, and Earth's orbit carries us around the Sun faster than the Space Shuttle orbits Earth.
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Why do the patterns of the stars in our sky look the same from year to year?
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Because the stars in the constellations are so far away.
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Where is our solar system located within the Milky Way Galaxy?
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Roughly halfway between the center and the edge of the visible disk of the galaxy
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Astronomers infer that the universe is expanding because distant galaxies all appear to _________.
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be moving away from us, with more distant ones moving faster
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Which statement about motion in the universe is not true?
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The mysterious dark matter is the fastest-moving material in the universe.
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When did humans learn that the Earth is not the center of the universe?
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Within the past 500 years
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Which of the following is not a general difference between a planet and a star?
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All planets are made of rock and all stars are made of gas.
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Our solar system consists of _________.
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the Sun and all the objects that orbit it
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A typical galaxy is a _________.
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collection of a few hundred million to a trillion or more stars, bound together by gravity
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Which of the following best describes what we mean by the universe?
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The sum total of all matter and energy
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An astronomical unit (AU) is _________.
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the average distance between Earth and the Sun
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A light-year is _________.
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about 10 trillion kilometers
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A television advertisement claiming that a product is light-years ahead of its time does not make sense because _________.
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it uses "light-years" to talk about time, but a light-year is a unit of distance
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The term observable universe refers to _________.
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that portion of the universe that we can see in principle, given the current age of the universe
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On a scale in which the distance from Earth to the Sun is about 15 meters, the distance from Earth to the Moon is _________.
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small enough to fit within your hand
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On a scale where the Sun is about the size of a grapefruit and the Earth is about 15 meters away, how far away are the nearest stars besides the Sun?
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About the distance across the United States
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The number of stars in the Milky Way Galaxy is approximately _________.
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a few hundred billion
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What do astronomers mean by the Big Bang?
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The event that marked the beginning of the expansion of the universe
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What do we mean when we say that the universe is expanding?
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Average distances between galaxies are increasing with time.
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Based on observations of the universal expansion, the age of the universe is about _________.
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14 billion years
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What is the ecliptic plane?
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The plane of Earth's orbit around the Sun
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How long does it take the Earth to complete one orbit around the Sun?
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One year
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Consider a raisin cake expanding uniformly in an oven. Viewed from one of the raisins, you would see _____.
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all other raisins moving away from you, with more distant raisins moving faster
