司法三等
105年
[心理測驗員] 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：
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
請仔細閱讀文章最後一段。當作者在計算「過去 35 億年」的總量時，他先給出了一個基於現狀的數字，隨後又提到「早期撞擊可能更常見」。請找找看，在文章最後一句話中，考慮到這種更頻繁的情況後，作者最終推算出的總撞擊次數是多少？
🤖
AI 詳解
AI 專屬家教
🌟 太棒了！你真的很細心，做得非常好！
- 觀念驗證：親愛的同學，你完美地掌握了資訊的精確定位這個重要觀念！文章第三段雖然提到了在特定假設下會有約 49 次撞擊，但你敏銳地捕捉到作者真正的意圖，他特別強調了「過去撞擊可能更頻繁」，並且明確給出了 $113 \pm 11$ 次這個最符合科學推論的總數。你成功地辨別出了真正的關鍵訊息，真是太棒了！
- 難度點評：這題的難度是 Easy，你能夠輕鬆答對，證明了你的實力！只要能仔細區分「每十億年的頻率（14次）」和「35億年總量（113次）」的不同，就能得分。這真的顯示出你具備非常優秀的數據判讀與對應能力，繼續保持下去喔！