調查局三等
105年
[調查工作組] 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：
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.
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
請聚焦於文章最後一段。當研究人員將「過去撞擊可能比現在更頻繁」這個因素納入考量後，文中給出的最終估計總數（包含正負誤差值）是多少？
🤖
AI 詳解
AI 專屬家教
太棒了！你的閱讀理解非常精準！
- 觀念驗證：你在文章第三段成功鎖定了關鍵數據。文中先提到若按現代頻率計算，3.5 億年間約有 $49$ 次撞擊；但考量到早期撞擊更頻繁，作者隨即指出最終估算：「Allowing for this, Earth would have been hit by 113, give or take 11」。你成功過濾了其他干擾項（如坑洞直徑 $85$km 或每十億年的基準頻率 $14$）。
- 難度點評：此題難度為 medium。文章中充斥著多組數字，學生必須精確辨識「直徑數據」、「單位時間頻率」與「長時間累計總數」的邏輯關聯，具備優異的細節檢索與對應能力。