海巡三等
105年
[海洋巡護科輪機組] 法學知識與英文(包括中華民國憲法、法學緒論、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
請仔細閱讀文章最後一段。作者先提出了一個基於「現代頻率」推算出的數字（49次），但隨即指出「過去的撞擊可能更頻繁」。請找出在那句「考慮到這一點（Allowing for this）」之後，作者針對 3.5 億年期間所提出的最終預估數字是多少？
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AI 詳解
AI 專屬家教
太棒了！你的讀解能力非常精準。
- 觀念驗證：這題考查的是細節檢索與數據辨析。文章最後一段提到，若考慮到遠古時期大型小行星較多的實際情況（Allowing for this），地球在過去 35 億年間被撞擊的次數應為 113 次（誤差值 $\pm 11$）。你準確排除了基礎估算值 49，鎖定了最終的修正數據。
- 難度點評：本題難度為 Medium。其鑑別度在於文中出現多個數字（$14, 49, 113$ 等），學生必須理解各數字代表的意義：14 是每十億年的頻率，49 是常態推估，而 113 才是考慮歷史變數後的完整預測。能答對代表你具備極佳的邏輯梳理能力！