Lecture 4. What is Life? 1944 book by Erwin Schrodinger

Transcription

1 Lecture 4 What is Life? 1944 book by Erwin Schrodinger

2 What is What is Life?" A little general-reader book published by Erwin Schrodinger in 1944 An influential book on biology written by a theoretical physicist Prominent scientists who said they were inspired by the book include Crick and Watson, joint discoverers of the structure of DNA in 1953

3 Erwin Schrodinger ( ) Born in Vienna Father, botanists; mother, d. of chemistry professor 1914 Habilitation (Post PhD); 1921 Full Physics Prof. at Breslau 1925 Prof. in Berlin 1926 discovered Schrodinger equation Foundation of quantum mechanics 1933 Nobel Prize for Physics (with Dirac and Pauli) (1933)

4 Erwin Schrodinger (after 1933) 1933 Left Germany for opposition to Nazi s anti-semitism Declined permanent positions at Oxford (1933) and Princeton (1934) for personal reasons Returned to Austria 1936 Fled Austria 1938 to England/Holland Institute of Advanced Studies, Dublin, Ireland 1956 returned to Vienna

5 Background The book is based on lectures delivered at Trinity College, Dublin, in February 1943 Already known in biology: chromosome, nucleus, cross-over, mitosis, meiosis, genes are units of heredity Known in physics Statistical mechanics, quantum mechanics Delbruck*: "the gene is a polymer of atomic structures." *Physicist turned biologist Nobel prize in physiology and medicine 1969

6 Chapter I: Order from disorder Many physical laws on a large scale are due to chaos on a small scale Thermal motion Life greatly depends on order Master code of a living organism has to consist of a large number of atoms

7 Chapter II & III Hereditary Mechanism and Mutation Mutation is important to evolution Genes must be small and permanent Mutations are single, discrete events In modern terms: it is digital Survival rate small if mutations are simultaneous Mutation is caused by ionization Quantum mechanical, not classical

8 Chapter IV Quantum-mechanical evidence Genes are almost forever, why? Thermal motion generates ceaseless small changes If mutation can be caused by accumulation of small changes, then genes cannot be permanent Habsburger Lippe Therefore mutations are quantum changes Quantum, not classical

9 Chapter V The Aperiodic Crystal Genetic material is large molecule that does not repeat itself If there are n different bases and molecule is L bases long, then there are n L different molecule For example: =10 60 Mutation cause by ionization of molecule Delbruck model

10 Chapter VI Order and Disorder Physics: natural direction is from order to disorder Biology: order seems to be maintained forever Hence there may be other laws of physics Schrodinger did not really believe so

11 Chapter VII Is Life Based on the Law of Physic? Schrodinger emphasize again nature is order to disorder, but observes biology/life seems to be order to order, he therefore raises the question given above He answers is affirmative. Yes, because: Part of the reason is quantum physics Another part is because life operates near low temperature, with little thermal fluctuation

12 Epilogue On determinism and free will Schrodinger observes: The body functions according to Nature s law But his mind controls his motion Hence he command Nature s law Hence I am God Almighty Note: The 1956 Schrodinger book Mind and Matter has had only a small impact.

13 Impact of What is Life? Inspired many great scientists Francis Crick and James Watson Codiscoverer of structure of DNA; 1962 Nobel Physiology or Medicine Praised by others Max Delbruck 1968 Nobel Physiology or Medicine Criticized by others Linus Pauling 1953 Nobel Chemistry, 1962 Peace Max Perutz Teacher of Watson and Crick 1962 Nobel Chemistry Now generally viewed as ranking among the important books in biology; greatly inspired interdisciplinary research

14 How right was What is Life? Genetic material is a large, linear Aperiodic crystal Correct. It is a DNA sequence A gene is a few thousand atoms Correct Natural selection acts on quantum changes on aperiodic crystal, hence huge diversity Almost correct, change quantum to discrete Order to disorder countered by negative entropy Incorrect No fundamentally new physics needed to explain biology; importance of complexity Probably mostly correct

15 What is Life? The Next Fifty Years 1993 Conference in Dublin celebrating 50th anniversary of publication of What is Life? Book published 1995, MP Murphy & LAJ O Niell, Editors Articles by prominent scientist including M. Eigen, 1967 Nobel Chemistry J Maynard-Smith, game theory, sex evolution SJ Gould Wonderful Life R Penrose, Relativity, Penrose (aperiodic) tiling S Kauffman At Home in the Universe

16 Some remarks from The Next Fifty Years Evolution is more than Darwinian gradualism; contingency is also important (SJ Gould) Understanding genes is not sufficient to compute the egg (L Wolpert) Neither order-to-order nor code-embedding genome is necessary for the development of life (S Kauffman) RNA before genetic code (JM Smith & E Szathmary) New physics needed to understand Mind (R Penrose)

17 Readable links What is Life? (Schrodinger) (Wikipedia) Review on Genetics by KR Dronamraju Short 2004 review Human Nature Review by JF Derry What is Life? The next fifty years (MP Murphy & LAJ O Neil) 9X Short publisher s (Cambridge U Press) review New Scientist: Brilliant minds forecast the next 50 years +next+fifty+year Google search with comments and sample pages