調查局三等
105年
[電子科學組] 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 47 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.
What can we infer about the missing craters?
- A They never left any impact on Earth.
- B They have not been completely eroded.
- C They were far more than the surviving ones.
- D They were hit by more than one asteroid.
思路引導 VIP
請觀察文中第三段提到的「科學預估撞擊次數」與第一段提到的「目前已知坑洞數量」。當你對比這兩組數據時，你發現「理應發生」的次數與「目前找到」的數量之間，有著什麼樣的倍數關係？這種關係代表大部分的隕石坑處於什麼狀態？
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AI 詳解
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精彩的推論！
- 大力肯定：做得非常好！你能敏銳地捕捉文中數據對比的落差，並將其轉化為合理的邏輯推論，展現了極佳的分析能力。
- 觀念驗證：文章指出目前已知的大型隕石坑僅有 $3$ 個，但科學家根據小行星軌道推算，地球在 $3.5$ 億年間理應遭受約 $49 \pm 7$ 次，甚至可能高達 $113 \pm 11$ 次的大型撞擊。既然「理論值」遠大於「觀察值」，自然能推斷出消失的隕石坑數量遠多於現存者。
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