1. Class 6 Summary Retracing our steps Class 6 Summary 1 review

2. Preface: Reductionism good for classical physics relativity quantum mechanics bad for nonlinear, chaotic systems weather prediction population dynamics Class 6 Summary 2 review

3. Ch. 1: Complexity Insect colonies The brain The immune system Economies The World-wide Web Class 6 Summary 3 review

4. Agent-based Modeling Class 6 Summary 4 review

5. Properties of Complex Systems Complex collective behavior Information processing Adaptation Class 6 Summary 5 review

6. Ch. 2 Dynamics, Chaos, and Prediction Class 6 Summary 6 Logistic population model review Simple and non-linear

7. Show us pictures! Class 6 Summary 7 review

8. Feigenbaum’s Constant Class 6 Summary 8 4.6692016 review

9. Ch. 2 Takeaway Simple, deterministic systems can generate apparent random behavior Long term prediction for such systems may be impossible in principle Such systems may show surprising regularities: period-doubling and Feigenbaum’s Constant Class 6 Summary 9 review

10. Ch. 3 Information Class 6 Summary 10

11. A big picture Class 6 Summary 11 reductionist mechanics thermodynamics statistical mechanics

12. Maxwell’s Demon Class 6 Summary 12 Appears to defy the Second Law of thermodynamics by decreasing entropy

13. Maxwell’s Demon and Entropy This issue is not completely settled. It appears that entropy increases because the demon acquires and subsequently erases information Class 6 Summary 13

14. Shannon’s theory Information channel is a stream of symbols Shannon entropy is expressed in terms of the probabilities of the symbols in the channel Class 6 Summary 14

15. Suppose the message is a single symbol with two possible values Class 6 Summary 15

16. New Horizons Class 6 Summary 16 12 watts 1000 bits/second 18 months

17. Ch. 4 Computation Class 6 Summary 17

18. Computation Hilbert’s Program: Is mathematics complete, consistent and decidable? (Entscheidungsproblem) Answers Goedel’s theorem Turing’s machine Class 6 Summary 18

19. Godel’s Theorem If arithmetic is consistent then there are true statements about arithmetic which cannot be proved. Mitchell’s example: This statement is not provable If false, then a false statement can be proved (really bad news). If true, then a true statement cannot be proved. Class 6 Summary 19

20. The Go-To Book Class 6 Summary 20

21. Class 6 Summary 21

22. A Turing machine Class 6 Summary 22 tape reader rules and state

23. Turing showed… There is no definite procedure for proving any mathematical statement true or false in a finite number of steps. Class 6 Summary 23

24. Class 6 Summary 24 Chapter 5 Evolution

25. “All great truths begin as blasphemies.” -- GBS “No idea in science has been more threatening to humans’ conceptions about themselves than Darwin’s theory of evolution; it arguably has been the most controversial idea in the history of science.” - MM Class 6 Summary 25

26. Jean-Baptiste Lamarck, 1744- 1829 Advocated inheritance of acquired characteristics example: wading birds Evolution had a “tendency to progression” Initially impressed Charles Darwin Class 6 Summary 26

27. Charles Darwin, 1809-1882 Class 6 Summary 27 1854?

28. Evolution by natural selection Offspring influenced by random mutations not acquired characteristics Competition for reproduction tests individuals Improvements passed to offspring Change is gradual Class 6 Summary 28

29. Gregor Mendel, 1822-1884 Class 6 Summary 29

30. Gregor Mendel, 1822-1884 Founder of modern genetics Disproved Lamarckian inheritance Discovered discrete “factors” in inheritance genes occur in pairs alleles are dominant and recessive Class 6 Summary 30

31. The Modern Synthesis Natural selection is the major mechanism of evolutionary change Evolution is a gradual process, driven by random mutation genetic recombination Speciation is the result of a microscopic process of selection Class 6 Summary 31

32. Challenges to the Modern Synthesis punctuated equilibria versus gradualism evolution by “jerks” evolution by “creeps” historical contingency including catastrophes biological constraints limitations on evolution Class 6 Summary 32

33. Stephen Jay Gould, 1941-2002 Class 6 Summary 33 punctuated equilibria science popularizer “living legend” developmental biology

34. Active debate Points of general agreement life has a single ancestor evolution continuing natural selection an important force no intelligent directing force Class 6 Summary 34

35. Ch. 6 Genetics, Simplified Class 6 Summary 35

36. Class 6 Summary 36 HC SVNT DRACONES

37. Chapter 7 Defining and Measuring Complexity Class 6 Summary 37

38. What is Complexity? no agreed-upon definition of complexity Wikipedia lists eight fields in which complexity is defined in different ways no single science of complexity Class 6 Summary 38

39. Some measures of Complexity Measures based on shortest encoding program: Kolmogrov effective complexity: Gell-Mann fractal dimensions: D hierarchy and near- decomposability Herbert Simon Class 6 Summary 39

40. Class 6 Summary 40 No satisfactory, universal, computable measure of complexity

41. A chronic issue Connecting reasonable concepts to quantitative measures Class 6 Summary 41

42. Chapter 8 Self-reproducing computer programs Class 6 Summary 42

43. The Fermi Paradox… Our sun is a typical star Billions of stars are billions of years older than the sun Plenty of time for advanced cultures to explore the Milky Way Class 6 Summary 43 Where are they?

44. John von Neumann, 1903-1957… interested in self-replicating machines von Neumann Universal Constructor Class 6 Summary 44

45. von Neumann probes… current state of the art: 3D printing Class 6 Summary 45

46. Artificial life Class 6 Summary 46 Jewish folklore Most famously, 16 th century Prague

47. Artificial life… Class 6 Summary 47

48. Artificial life (A-Life) Very contentious topic Two general forms Strong A-Life Weak A-Life Class 6 Summary 48

49. A-Life… Class 6 Summary 49 an adult hermaphrodite C. elegans worm www.openworm.org

50. Computer replication, evolution and Class 6 Summary 50 The Singularity

51. Class 6 Summary 51 Finis review