Astronomy – Chapter 24 – Flashcards
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Why do some scientists think that Jupiter's existence may have been critical for life to evolve on Earth?
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It kicked out many comets from the inner solar system through gravitational encounters, thus ending the heavy bombardment phase of the solar system.
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Which of the following is the most important for maintaining a stable climate on Earth over the time it took for large organisms to evolve?
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plate tectonics
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Why do some scientists say that the Moon way have been important for the evolution of human life?
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It stabilized the earth's axis tilt and prevented large climate changes.
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What defines the habitable zone around a star?
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the region around a star where liquid water can exist on planetary surfaces
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At present, what is the primary way that the search for extraterrestrial intelligence (SETI) is carried out?
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by using radio telescopes to search for signals from extraterrestrial civilizations
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SETI (the Search for Extraterrestrial Intelligence) searches for communications from life in planets and moons
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around nearby stars.
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At about what fraction of the speed of light do today's spacecraft travel?
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1/10,000
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According to fossil evidence how far back in time did life on Earth exist?
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About 3.5 billion years or more
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What is a mutation?
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A change in a living cell's DNA
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Based on DNA studies, it seems that all life on Earth
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shares a common ancestor.
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How did oxygen (o2) get into Earth's atmosphere
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It was released by life through the process of photosynthesis.
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Which of the following is NOT considered crucial for life to exist on some world?
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Liquid water
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The Sun's habitable zone
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extends from some place a little beyond the orbit of Venus to some place near the orbit of Mars.
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The "rare Earth hypothesis" holds that Earth-like planets are probably quite rare. Which of the following statements best sums up the current status of the debate over this hypothesis?
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We do not have enough data to settle the debate, because counterarguments can be made for each argument suggesting Earth-like planets may be rare.
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Einstein's theory of relativity tells us that travelers who make a high-speed trip to a distant star and back will
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age less than people who stay behind on Earth
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Suppose it turns out that 1 in 1 million stars has a planet that at some point in its history is home to an advanced civilization. Then the total number of civilizations that have arisen in our galaxy would be closest to
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400,000
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