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| 徐遐生教授 |
2009年邵逸夫天文獎得主
美國加州大學聖地牙哥分校物理系教授
英國皇家科學院院士
美國國家科學院院士
中央研究院院士 |
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Climate Change and Energy Solutions
氣候變遷和能源解決方案 |
The greatest challenge facing civilization in the twenty-first century is climate change induced by the net emission of carbon dioxide by human activity. We review the science behind this subject from an astronomer’s perspective, using well-understood principles underlying the balance of heating by the light from the Sun and the cooling of the Earth’s infrared radiation back to space. We investigate the evidence locked in Antarctic ice cores of past cycles of runaway warming and cooling (interglacial periods and ice ages) and their relationship to astronomical phenomena (the Milankovich cycle), and we point out why current events are different. We also discuss the alarming possibility that the Earth has already passed the tipping point for the melting of the polar ice. We then give order of magnitude arguments for the maximum amount of power that we can derive from alternative sources of energy. Compared to projected needs by mid-century, there are only five realistic energy choices to reduce or eliminate net carbon-dioxide emissions: (1) fossil fuel with carbon capture and sequestration, (2) biofuels, (3) solar photovoltaics/ solar thermal, (4) wind, and (5) nuclear. We point out the drawbacks of the first four. We then explain the basics of nuclear fission, concluding that reprocessing and breeding are necessary to remove public concerns about waste management, safety, and sustainability of the nuclear option. In particular, we point out why the long overlooked technologies of molten salt reactors coupled to the thorium fuel cycle is superior in terms of cost, passive safety, and weapons non-proliferation to the current usage of nuclear power. In particular, we discuss an approach using novel materials to build two-fluid molten salt reactors on a rapid enough schedule to make America and the world free of plutonium and net CO2 emission by mid-century. Of particular interest may be the possibility of leveraging the capacity of such facilities by coupling nuclear power to the production of artificial coal. The latter holds the promise of making existing coal-fired power plants not only carbon neutral, but even carbon negative. In this manner, it may be possible to reverse human-induced climate change and pass on to future generations a mode of living compatible with satisfying the economic aspirations of billions of people now living in poverty and a greener, more benign, and more bountiful planet.
二十一世紀對人類文明的最大挑戰就是氣候變遷，這是肇因於人類活動所產生的二氧化碳的淨排放。我從一個天文學者的觀點，來檢視這個議題背後的科學問題，應用熟知的物理原理，此原理用以說明太陽光照射而引起的生熱作用，正好平衡地球輻射紅外線至太空而致的冷卻作用。我們調查了深鎖在南極冰芯的證據，這是過去地球上冷熱失控的循環所留下的痕跡（即冰河的間隔期和冰河的持續期），以及它們和天文現象的關聯（即Milankovich循環）。我將指出為何現在的情況和以往不同。我也將討論正警示中的可能性：地球極地冰層的融化早已越過了臨界點。我將以數量級來估算我們從替代能源所能取得的最大能量。如果和本世紀中葉預估的能源需求相比，我們僅有下列五種實際的能源選項，可用於減少或消除二氧化碳的淨排放量：(1)可以捕捉或隔離碳的化石燃料；(2)生質能；(3)太陽的光伏能或熱能；(4)風能；(5)核能。我將指出前四種能源的缺點。然後我將解釋核分裂的基本原理，綜結出「再處理」和「滋生」是必要的核燃料處理方式，用於消除公眾對核廢料處理、核能安全、以及核能永續應用的疑慮。我要特別指出長久被忽略的核能技術—搭配釷燃料循環的熔鹽反應爐，不管就成本、被動安全性、和防範核武擴散而言，都優於現行的核能產生方式。我要特別討論一種利用新奇材料來建造雙流體的熔鹽反應爐的方法，可以在夠快的時間內，使美國和全世界免於使用鈽，並使二氧化碳的淨排放量為零。特別有趣的是，結合核能和人造煤的生產，有可能使這種核能設施的容量起了槓桿效應。後者有望使現有的燃煤火力發電廠，不只變成碳中性，甚至變成減碳。就此而言，這種核能生產的新方式有可能改變人類所誘發的氣候變遷，並使未來人類世代的生活模式，可以滿足以億計窮人對改善經濟的渴望，並兼顧維持一個綠色的、較為良性的、更為豐饒的星球。
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The Relation Among Physics, Chemistry, And Biology In The Natural World
在自然世界中的物理、化學、和生命科學之間的關連性 |
Physics, chemistry, and biology are taught in high school and college as if they were separate disciplines. However, the separation is more an accident of human history than a part of the natural world. The division was not so important when we humans were just learning to understand and control the seemingly chaotic elemental forces all around us, but as we have gained more and more power over the natural world, the failure to see the systems aspects of nature rather than just its component parts is proving ever more restrictive and dangerous. As an example of these deep connections, I review the history of human thought on the elemental building blocks of the universe and the forces that exist among them, from their beginnings in mystical thought to our current understanding of their origins in the early universe and the deep interiors of stars, and to the role that these same building blocks and forces play in the origin and sustenance of life on Earth. Despite this progress in scientific understanding, however, most people still project mystical ideas onto the natural world that they inhabit. Only if we have an appreciation of the true scope and scale of the marvelous processes that created the Earth and the life forms that exist on it, can we do long-range planning beyond election cycles and the brief lives of individual humans.
物理、化學、和生命科學的授課方式，通常在高中與大學裡都被當作是各自獨立的課程。然而，這三門學科的分離只是人類歷史上的一個意外，而非大自然的一部分。當我們人類只是想學著去理解和控制我們周遭看似混亂的基本作用力，這樣的分門別類並不嚴重。但是隨著我們累積更多凌駕大自然的力量時，不能看待自然界的系統面，而只是著意於其個別成份的分立面，愈發証實了我們對自然界認知的狹隘性和危險性。舉一個關聯很深的例子，我回顧人類思考宇宙基本組成單位和存在於它們之間作用力的歷史過程，從起始對這些組成單位的神秘思維，到現在我們對它們源自於早期宇宙的瞭解和對星球內部深處組成的認知，以及我們所知道的這些基本組成單位和交互作用力，對地球上生命的起源和持續所扮演的角色。不管科學認知的進展如何，如今還是有很多人對於自己居住的自然世界，仍然抱持著神秘的想法。只有當我們對創造地球和生命的不可思議的過程，能真正認識到它的廣度和規模，我們才能跳脫人類個體的短暫生命和循環，做出長遠的規劃。
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