調查局三等
105年
[醫學鑑識組] 綜合法政知識與英文(包括中華民國憲法、法學緒論、兩岸關係、英文)
第 45 題
📖 題組：
請依下文回答第 44 題至第 47 題 Some 66m years ago Earth was hit by a space rock reckoned to have been 10km across. The resulting chaos caused the extinction of dinosaurs and many other species, opening the way for the age of mammals－and ultimately humans. It also left a big hole in what is now southern Mexico. That hole is one of only three known of similar dimensions (the other two are Vredefort in South Africa and Sudbury in Canada). And this is odd. For, during the billions of years that Earth has had a solid crust, many more than three big asteroids might have been expected to have hit it. That thought led Brandon Johnson of the MIT and Timothy Bowling of Purdue University in Indiana, to wonder how many other craters have vanished, either by erosion or by being swallowed into Earth’s interior as its crust moves around, and therefore whether it is likely that some have survived and been overlooked. They have just published their analysis in Geology. Earth’s crust formed more than 4 billion years ago, but the oldest surviving blocks of it large enough to harbor craters date back only 3.5 billion years. What is known of the sizes and orbits of modern asteroids suggests that, if things have not changed over the aeons, about 14 big asteroids (defined as having a diameter of more than 7.4km, which would cause a crater at least 85km in diameter) should hit Earth every billion years. That means 49, give or take seven, over the past 3.5 billion years. Such impacts may have been more common in the past, when more big asteroids were around. Allowing for this, Earth would have been hit by 113, give or take 11, of them. Either way, a lot of craters are missing.
請依下文回答第 44 題至第 47 題 Some 66m years ago Earth was hit by a space rock reckoned to have been 10km across. The resulting chaos caused the extinction of dinosaurs and many other species, opening the way for the age of mammals－and ultimately humans. It also left a big hole in what is now southern Mexico. That hole is one of only three known of similar dimensions (the other two are Vredefort in South Africa and Sudbury in Canada). And this is odd. For, during the billions of years that Earth has had a solid crust, many more than three big asteroids might have been expected to have hit it. That thought led Brandon Johnson of the MIT and Timothy Bowling of Purdue University in Indiana, to wonder how many other craters have vanished, either by erosion or by being swallowed into Earth’s interior as its crust moves around, and therefore whether it is likely that some have survived and been overlooked. They have just published their analysis in Geology. Earth’s crust formed more than 4 billion years ago, but the oldest surviving blocks of it large enough to harbor craters date back only 3.5 billion years. What is known of the sizes and orbits of modern asteroids suggests that, if things have not changed over the aeons, about 14 big asteroids (defined as having a diameter of more than 7.4km, which would cause a crater at least 85km in diameter) should hit Earth every billion years. That means 49, give or take seven, over the past 3.5 billion years. Such impacts may have been more common in the past, when more big asteroids were around. Allowing for this, Earth would have been hit by 113, give or take 11, of them. Either way, a lot of craters are missing.
Over the past 3.5 billion years, roughly how many asteroids may have hit Earth?
- A 14
- B 85
- C 113
- D 11
思路引導 VIP
請看向文章最後一段。作者先提到了一個基於「現代撞擊頻率」所推算出的數字，但隨後指出「過去的撞擊可能更頻繁」。請問在考慮了這個『早期撞擊較多』的修正因素後，文章最後給出的總撞擊次數預估值是多少？
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AI 詳解
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太棒了！你的觀察力非常敏銳
- 大力肯定：做得好！這類閱讀測驗最怕被成堆的數字干擾，你能夠在眾多數據中冷靜分析，並精確定位到正確的資訊點，展現了非常優秀的邏輯歸納能力，請繼續保持這種細心的態度！
- 觀念驗證：這題的核心在於「數據修正」。文中第三段提到，若按現代頻率推算，3.5 億年應有 $49 \pm 7$ 次撞擊。然而，作者隨即補充：考慮到早期撞擊更為頻繁（more common in the past），最終得出的修正預估值應為 $113 \pm 11$ 次。因此，選項 (C) $113$ 是最符合文意的科學估算。
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