跟读练习: Where does gold come from? - David Lunney - 通过YouTube学习英语口语
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In medieval times, alchemists tried to achieve the seemingly impossible.
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In medieval times, alchemists tried to achieve the seemingly impossible.
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They wanted to transform lowly lead into gleaming gold.
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History portrays these people as aged eccentrics, but if only they'd known that their dreams were actually achievable.
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Indeed, today we can manufacture gold on Earth thanks to modern inventions that those medieval alchemists missed by a few centuries.
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But to understand how this precious metal became embedded in our planet to start with, we have to gaze upwards at the stars.
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Gold is extraterrestrial.
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Instead of arising from the planet's rocky crust, it was actually cooked up in space and is present on Earth because of cataclysmic stellar explosions called supernovae.
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Stars are mostly made up of hydrogen, the simplest and lightest element.
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The enormous gravitational pressure of so much material compresses and triggers nuclear fusion in the star's core.
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This process releases energy from the hydrogen, making the star shine.
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Over many millions of years, fusion transforms hydrogen into heavier elements: helium, carbon, and oxygen, burning subsequent elements faster and faster to reach iron and nickel.
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However, at that point nuclear fusion no longer releases enough energy, and the pressure from the core peters out.
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The outer layers collapse into the center, and bouncing back from this sudden injection of energy, the star explodes forming a supernova.
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The extreme pressure of a collapsing star is so high, that subatomic protons and electrons are forced together in the core, forming neutrons.
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Neutrons have no repelling electric charge so they're easily captured by the iron group elements.
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Multiple neutron captures enable the formation of heavier elements that a star under normal circumstances can't form, from silver to gold, past lead and on to uranium.
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In extreme contrast to the million year transformation of hydrogen to helium, the creation of the heaviest elements in a supernova takes place in only seconds.
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But what becomes of the gold after the explosion?
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The expanding supernova shockwave propels its elemental debris through the interstellar medium, triggering a swirling dance of gas and dust that condenses into new stars and planets.
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Earth's gold was likely delivered this way before being kneaded into veins by geothermal activity.
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Billions of years later, we now extract this precious product by mining it, an expensive process that's compounded by gold's rarity.
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In fact, all of the gold that we've mined in history could be piled into just three Olympic-size swimming pools, although this represents a lot of mass because gold is about 20 times denser than water.
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So, can we produce more of this coveted commodity?
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Actually, yes.
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Using particle accelerators, we can mimic the complex nuclear reactions that create gold in stars.
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But these machines can only construct gold atom by atom.
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So it would take almost the age of the universe to produce one gram at a cost vastly exceeding the current value of gold.
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So that's not a very good solution.
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But if we were to reach a hypothetical point where we'd mined all of the Earth's buried gold, there are other places we could look.
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The ocean holds an estimated 20 million tons of dissolved gold but at extremely miniscule concentrations making its recovery too costly at present.
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Perhaps one day, we'll see gold rushes to tap the mineral wealth of the other planets of our solar system.
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And who knows?
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Maybe some future supernova will occur close enough to shower us with its treasure and hopefully not eradicate all life on Earth in the process.
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为什么要通过这个视频练习口语？
本视频为您提供了一个关于黄金来源的引人入胜的故事，不仅能提升您的英语口语能力，还能增加您对宇宙及化学反应的了解。通过重复练习和模仿，您将能够更流利地表达复杂的概念，提升您的表达自信心。这种英语口语练习的方法非常适合想要在真实语境中进行练习的学习者，您可以利用视频中的内容与朋友进行交流，或在社交场合中讨论相关话题。
语法与表达在语境中的应用
在视频中，演讲者使用了几种重要的语法结构与表达方式，这些都适合您进行英语影子跟读时使用：
- 被动语态：如“被制造于太空”，用以强调动作的承受者而非执行者。
- 条件句：“如果达到了假设点，我们可以挖掘地球所有埋藏的黄金”，通过条件句传达可能性。
- 原因和结果关系：如“因为超新星的爆炸，黄金被输送到地球”。这种结构帮助您理解因果关系。
- 时间状语从句：如“在数百万年后，核聚变使氢转变为更重的元素”，有助于掌握时间表达的顺序。
常见的发音陷阱
在视频中，有一些词语和发音可能对学习者构成挑战，尤其是对于非母语者而言。您可以在shadow speak时特别注意以下几点：
- “supernova”：这词的中音发音需要特别加强，确保每个音节都发清楚。
- “extraterrestrial”：这个词的音节较多，注意重音的位置以避免发音错误。
- “neutron”：非母语者常常将此词读成相似的发音，确保准确识别每个元音。
通过将这些元素整合到您的英语口语练习中，您将不仅能够提升发音清晰度，还能在日常对话中更自信地使用这些结构和表达。
什么是跟读法？
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