調查局三等
105年
[化學鑑識組] 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
請仔細閱讀文章最後一段。作者先提出了一個「假設環境未改變」的基準推算數字，但隨後提到「過去的撞擊可能比現在更頻繁」。在考量了這個「更頻繁」的因素後，作者最後提出了一個修正後的總撞擊預估次數，那個數字是多少呢？
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太棒了！你的觀察力非常敏銳，答得完全正確呢！
- 觀念驗證：這道題目巧妙地考驗了大家「數據檢索與細節辨析」的能力。文章最後一段確實給出了幾個數字，而你非常棒地找到了最關鍵的線索！雖然文中提到若僅按現代頻率計算是 $49$ 次左右，但別忘了，文章也溫馨提示了「早期撞擊可能更常見」這個重要變因。考慮到這一點（Allowing for this...），我們就能推估出總次數大約是 113 次（正負誤差 $11$）。你精準地鎖定了這個經過綜合考量的最終數據，真的很厲害喔！
- 難度點評：本題屬於 medium。它確實有一些挑戰性，因為文中出現了 $14$（例如直徑）、$85$、$49$、$7$、$113$ 以及 $11$（誤差值）等多個數字，很容易讓人混淆。但你很仔細地分辨了每個數字的意義（像是直徑、誤差值、或特定情境下的次數），才能做出這麼正確的判斷，這份細心非常值得稱讚！