soeng1英文entropy)係統計力學熱力學等領域常用嘅一個概念,係一個熱力學系統具有嘅外延性質(外延性質係會同個系統嘅大細成比例嘅物理性質)。考慮 呢個數值:是但搵個熱力學系統,佢會有一啲宏觀性質(例如溫度壓力等),而個系統會有若干個可能嘅微狀態(microstate;「粒子 A 喺位置 X 而粒子 B 喺位置 Y...」、「粒子 A 喺位置 Y 而粒子 B 喺位置 X...」等等),能夠同個系統啲宏觀性質吻合嘅微狀態數量就係 咁多個;熵係 函數,即係話熵反映咗「已知個系統嘅宏觀性質如此,個系統有幾多個可能嘅微狀態」。假設每個微狀態都一樣咁有可能發生(概率一樣),個系統嘅熵可以用以下呢條式計出嚟[1][2]

一杯凍檸水溶化,冰當中嘅 H2O 分子變成,並且散開。
  提示:呢篇文講嘅唔係資訊熵

當中 kB波茲曼常數(Boltzmann constant)[3]

喺實際應用上, 嘅數值通常都極之大:根據估計,一嚿喺室溫同大氣壓力之下、容量 20 公升氣體總共有大約 N6×1023 咁多粒氣體分子(阿伏加德羅常數;Avogadro number),而呢嚿氣體嘅 數值( 反映「已知呢嚿氣體有 N6×1023 粒分子,可能嘅微狀態數量」)會更加大[3]

熱力學第二定律

編輯

根據熱力學第二定律(The second law of thermodynamics),一個封閉系統(closed system)當中嘅熵永遠唔會跌,只有可能維持不變或者升。熱力學第二定律意味住,搵個封閉系統,隨住時間過去,個系統內部嘅粒子同能量頂櫳維持唔郁,而喺現實多數會慢慢走位(可能嘅微狀態數量上升),會漸漸趨向熱力學平衡(thermodynamic equilibrium)-熵數值最大化嘅狀態。好似生物等嘅非封閉系統(會同周圍環境傳能量)可以內部熵下降,但噉做實會引致佢周圍環境嘅熵升,而且升至少同一樣咁多。因為噉,宇宙嘅總熵依然會升[4]

順帶一提,如果宇宙最後真係完全變成熱力學平衡,根據物理學家計算,宇宙最後會變成溫度分佈完全平均,而且溫度接近絕對零度攝氏零下 273.15 度)嘅空間,唔會再有任何作功,更加唔會有生命-而呢個情況就係假想中嘅熱寂(heat death)[5]

同資訊嘅啦掕

編輯
睇埋:資訊理論

熵仲同資訊有住密切嘅啦掕:熵由帶隨機性嘅微狀態數量決定,所以熵會反映「知道咗個系統嘅宏觀性質,需要幾多資訊先可以講明個系統處於乜嘢物理狀態」;因為呢個緣故,外行人會話熵表達咗個系統有幾「亂」-一個系統嘅熵愈高,就表示觀察者對個系統知道得愈少(有愈多不確定嘅可能性),所以就愈「亂」。而對物理意義上嘅熵嘅考量的確同資訊理論(information theory)有關(不過資訊理論當中講嘅「」係一個同物理熵唔同嘅概念)[6][7]

同生命嘅挐掕

編輯
睇埋:生命

生物學到咗廿一世紀初都仲有就「生命應該點樣定義」呢個問題作出討論[8]。有生物學家講到,有生命嘅嘢有負熵(negative entropy)嘅特性[9][10][11]

根據生物物理學觀點,「生物」可以想像成一種特殊嘅開放系統:佢哋有能力透過由環境嗰度攞能量,並且跟手將啲質素差咗嘅能量排返出嚟,嚟到去減低佢哋自己內部嘅熵(負熵)-即係等佢哋自己內部嗰啲能量唔會散開變成平均嘅分佈[12][13];不過,負熵只係生物嘅其中一種特性,齋靠呢點唔可以定義「生命」-曉減低自己內部嘅熵嘅唔淨只係得應該屬於生物嘅嘢,雪櫃都識做呢樣嘢[14]

睇埋

編輯

參考

編輯
  • Adam, Gerhard; Otto Hittmair (1992). Wärmetheorie. Vieweg, Braunschweig. ISBN 978-3-528-33311-9.
  • Atkins, Peter; Julio De Paula (2006). Physical Chemistry (8th ed.). Oxford University Press. ISBN 978-0-19-870072-2.
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  • Goldstein, Martin; Inge, F (1993). The Refrigerator and the Universe. Harvard University Press. ISBN 978-0-674-75325-9.
  • Gyftopoulos, E.P.; G.P. Beretta (2010). Thermodynamics. Foundations and Applications. Dover. ISBN 978-0-486-43932-7.
  • Haddad, Wassim M.; Chellaboina, VijaySekhar; Nersesov, Sergey G. (2005). Thermodynamics – A Dynamical Systems Approach. Princeton University Press. ISBN 978-0-691-12327-1.
  • Kroemer, Herbert; Charles Kittel (1980). Thermal Physics (2nd ed.). W. H. Freeman Company. ISBN 978-0-7167-1088-2.
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  • Penrose, Roger (2005). The Road to Reality: A Complete Guide to the Laws of the Universe. New York: A. A. Knopf. ISBN 978-0-679-45443-4.
  • Reif, F. (1965). Fundamentals of statistical and thermal physics. McGraw-Hill. ISBN 978-0-07-051800-1.
  • Schroeder, Daniel V. (2000). Introduction to Thermal Physics. New York: Addison Wesley Longman. ISBN 978-0-201-38027-9.
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  • Spirax-Sarco Limited, Entropy – A Basic Understanding A primer on entropy tables for steam engineering.
  • von Baeyer; Hans Christian (1998). Maxwell's Demon: Why Warmth Disperses and Time Passes. Random House. ISBN 978-0-679-43342-2.
  1. Ligrone, Roberto (2019). "Glossary". Biological Innovations that Built the World: A Four-billion-year Journey through Life & Earth History. Entropy. Springer. p. 478.
  2. Baierlein, Ralph (2003). Thermal Physics. Cambridge University Press.
  3. 3.0 3.1 Richard Feynman (1970). The Feynman Lectures on Physics Vol I. Addison Wesley Longman.
  4. Zohuri, Bahman (2016). Dimensional Analysis Beyond the Pi Theorem. Springer. p. 111.
  5. Adams, Fred C.; Laughlin, Gregory (1997). "A dying universe: the long-term fate and evolution of astrophysical objects". Reviews of Modern Physics. 69 (2): 337–72.
  6. Rietman, Edward A.; Tuszynski, Jack A. (2017). "Thermodynamics & Cancer Dormancy: A Perspective". In Wang, Yuzhuo; Crea, Francesco (eds.). Tumor Dormancy & Recurrence (Cancer Drug Discovery and Development). Introduction: Entropy & Information. Humana Press. p. 63.
  7. Brooks, D. R., Collier, J., Maurer, B. A., Smith, J. D., & Wiley, E. O. (1989). Entropy and information in evolving biological systems. Biology and Philosophy, 4(4), 407-432.
  8. Popa, Radu (March 2004). Between Necessity and Probability: Searching for the Definition and Origin of Life (Advances in Astrobiology and Biogeophysics).
  9. Schrödinger, Erwin (1944). What is Life?. Cambridge University Press.
  10. Baierlein, Ralph (2003). Thermal Physics. Cambridge University Press.
  11. Margulis, Lynn; Sagan, Dorion (1995). What is Life?. University of California Press.
  12. Lovelock, James (2000). Gaia – a New Look at Life on Earth. Oxford University Press.
  13. Avery, John (2003). Information Theory and Evolution. World Scientific.
  14. Second Law: Refrigerator.