Areas of Knowledge

1. Areas of Knowledge SCIENCE

2. Science “ For thousands of years humans have had a miserable existence. A short life characterised by cold, hunger, disfiguring diseases and eventually a premature and painful death. In the last 100 years or so we have largely be spared this. People suffer less and live longer. In general people are better educated and can now live meaningful lives. This is not a miracle – it is due to Science.” Simon Porter

3. What is a scientist? Draw and/or describe your typical scientist

4. Googlethinks they look like this:

5. And can be defined like this: • A person who has studied science, especially one who is active in a particular field of investigation.www.mdanderson.org/patients_public/about_cancer/display.cfm • a person who uses observation, experimentation and theory to learn about a subject (Biologists, physicists, chemists, geologists and astronomers are all scientists.)education.jlab.org/beamsactivity/6thgrade/vocabulary/index.html • a person that knows a great deal about a branch of science. An ornithologist is a scientist that specializes in the study of birds.www.inhs.uiuc.edu/chf/pub/virtualbird/glossary.html • a person with advanced knowledge of one or more sciences wordnet.princeton.edu/perl/webwn What features did you identify?

6. What are the ideal characteristics of a scientist? • Collaborative • Observant • Creative • Open-minded • Risk-taking • Methodical • Analytical • ?? How about being a believer? Being perseverant? Being ethical?

7. CSI Whilst watching this episode – fill in the sheet. • Series 1 episode 10

8. Learn the Truthcard game Each group offers a card, which the Mr Porter takes or rejects according to an unknown rule Work out what the rule is to win a point for your team No random guessing – your group may only propose a theory once it has been discussed and agreed in the group. You can only suggest the answer when it is your turn

9. Let’s go!

10. The first three rules were: • Red, black, red, black, red… • Spade, heart, club, diamond, spade, heart, club, diamond… • Odd, even, Odd, even, Odd, even… It may have been hard to distinguish the first two patterns, because 2 is a specialised form of 1. They look the same, & once stuck in a theory you may have succumbed to confirmation bias What was needed to distinguish them? Experimenting, esp: falsification

11. The processes you are using: • Observing • Reasoning • Intuiting • Decision making • Teamwork • Cooperating and competing

12. Your processes refined: • Pattern spotting • Guessing the rule • Testing the rule = • Empirical observation • Forming an inductive, reasoned hypothesis • Testing by falsification Which is the most important part of the process?

13. Let’s try some more complex patterns

14. Try these patterns: 4. P, not P, P, not P, P, not P… 5. Card given by boy, girl, boy, girl… 6. Accepted if given from left hand, right hand, left hand… 7. Accepted if offered with a bribe… Simple rules, but hard to discern because: You were looking for the wrong thing: you looked in the cards, not in the circumstances. You made assumptions without realising. Paradigms were not the whole story.

15. What did this have to do with ToK? • The teacher was “Nature” • You were scientists, trying to understand “Nature”’s workings & rules • You cooperated & competed in order to succeed • You observed • You hypothesised, by using inductive reasoning & intuition • You tested, most successfully by falsification • You modified your theories • Simple appearances hid complex patterns, and vice versa • Your paradigms got in the way of knowledge Just like SCIENCE and scientists!

16. What isthe scientific method? How do scientists gain their knowledge?

17. Remember the characteristics of scientists • Collaborative • Observant • Creative • Open-minded • Risk-taking • Methodical • Analytical • ??

18. Remember the processes used in the card game • Pattern spotting • Guessing the rule • Testing the rule = • Empirical observation • Forming an inductive, reasoned hypothesis • Testing by falsification

19. Draw and label a diagram or flow-chart of the model scientific method Key elements must be: • observation of empirical and measurable evidence, • experimentation (esp falsification, the process by which we eliminate failures and falsehoods), and • Logical, rational and coherent theoretical explanations

20. How does your model compare with this one? Theory confirmed and published as knowledge Prediction and experimental testing Inductive hypothesis Experimental data or observation Theory is falsified and discarded What are the problems or issues with this model?

21. What are the problems or issues with this model? • Paradigms and perception problems with observation (see next slide) • Subjectivity rather than objectivity in observations • Confirmation bias (Millikan’s oil drop – following slide)) What is the essential component of the scientific method?

22. The extra chromosomes! • “The Bizarre Case of Chromosomes that Never Was” by Robert Mathews is a fascinating article that explores the human nature of conformity. In 1932, the American zoologist Theophilus Painter, published a study where he claimed that they are 24 pairs of chromosomes in the human body. Painter did so fully confident in his findings. As other scientist repeated Painter’s study they claimed to also find 24 pairs of chromosomes. However there were a few scientists who claimed to see as few as 19 and others 23. These scientists then thought their findings were just wrong because they knew that there was went to be 24. That is until 1956, when scientist finally discovered a way to place cells on microscope slides, which helped separate the chromosomes clearly. When scientists did this they found that there was in fact only 23 chromosomes in the human body. Researchers even went back to textbooks and looked at the photographs of chromosomes. They found that the photograph clearly showed 23 pairs of chromosomes, however the caption stated that there were 24 pairs.

23. Charge on an electron • Robert Millikan performed a ground breaking experiment between 1900 and 1913 to measure the change on an electron. There is some controversy over the use of selectivity in Millikan's results raised by the historian Gerald Holton. Holton (1978) pointed out that Millikan disregarded a large set of the oil drops gained in his experiments without apparent reason.

24. models of scientific change:Karl Popper http://en.wikipedia.org/wiki/Karl_Popper • Each theory builds progressively on the theories preceding it 3 2 1

25. models of scientific change:Thomas Kuhn http://en.wikipedia.org/wiki/Thomas_Samuel_Kuhn • Paradigms encompass some parts of previous theories, but reject other parts 3 2 1

26. models of scientific change:Paul Feyerabendhttp://en.wikipedia.org/wiki/Paul_Feyerabend • Theories have little to do with previous theories, and are incoherent or inconsistent. 2 3 1 It could be argued that the scientific method itself has been developed over time, ‘scientifically’!

27. An example – quantum physics

28. Light emitted cathode anode Low pressure gas electric current Atomic spectra When a gas is heated to a high temperature, or if an electric current is passed through the gas, it begins to glow.

29. Emission spectrum If we look at the light emitted (using a spectroscope) we see a series of sharp lines of different colours. This is called an emission spectrum.

30. Absorption Spectrum Similarly, if light is shone through a cold gas, there are sharp dark lines in exactly the same place the bright lines appeared in the emission spectrum. Light source gas Some wavelengths missing!

31. Why? Scientists had known about these lines since the 19th century, and they had been used to identify elements (including helium in the sun), but scientists could not explain them.

32. Rutherford At the start of the 20th century, Rutherford viewed the atom much like a solar system, with electrons orbiting the nucleus.

33. Rutherford Radiating energy However, under classical physics, the accelerating electrons (centripetal acceleration) should constantly have been losing energy by radiation (this obviously doesn’t happen).

34. Niels Bohr In 1913, a Danish physicist called Niels Bohr realised that the secret of atomic structure lay in its discreteness, that energy could only be absorbed or emitted at certain values. At school they called me “Bohr the Bore”!

35. The Bohr Model We say that the energy of the electron (and thus the atom) can exist in a number of states n=1, n=2, n=3 etc. (Similar to the “shells” or electron orbitals that chemists talk about!) n = 1 n = 2 n = 3

36. High energy n levels are very close to each other n = 5 n = 4 n = 3 n = 2 n = 1 (the ground state) The Bohr Model We can show the energy levels on a diagram 0 Energy eV Electron can’t have less energy than this -13.6

37. 0 Energy eV n = 5 n = 4 n = 3 n = 2 -13.6 n = 1 (the ground state) Atomic transitions If an electron is a level above the ground state, it can make a transition to a lower state. Thus an atom in state n = 2 can go to n = 1 (an electron jumps from orbit n = 2 to n = 1) Wheeee! electron

38. 0 Energy eV n = 5 n = 4 n = 3 n = 2 -13.6 n = 1 (the ground state) Atomic transitions Every time an electron makes a transition, a singlephoton of light is emitted ( a little “packet” of light energy) electron

39. 0 Energy eV n = 5 n = 4 n = 3 n = 2 -13.6 n = 1 (the ground state) Atomic transitions The energy of the photon is equal to the difference in energy (ΔE) between the two states. electron ΔE

40. 0 Energy eV n = 5 n = 4 n = 3 n = 2 -13.6 n = 1 (the ground state) The Lyman Series Transitions down to the n = 1 state give a series of spectral lines in the UV region called the Lyman series. Lyman series of spectral lines (UV)

41. 0 Energy eV n = 5 n = 4 n = 3 n = 2 -13.6 n = 1 (the ground state) The Balmer Series Transitions down to the n = 2 state give a series of spectral lines in the visible region called the Balmer series. Balmer series of spectral lines (visible) UV

42. 0 Energy eV n = 5 n = 4 n = 3 n = 2 -13.6 n = 1 (the ground state) The Pashen Series Transitions down to the n = 3 state give a series of spectral lines in the infra-red region called the Pashen series. Pashen series (IR) visible UV

43. Emission Spectrum of Hydrogen The emission and absorption spectrum of hydrogen is thus predicted to contain a line spectrum at very specific wavelengths, a fact verified by experiment. Which is the emission spectrum and which is the absorption spectrum?

44. Limitations of the Bohr Model • Can only treat atoms or ions with one electron • Does not predict the intensities of the spectral lines • Inconsistent with the uncertainty principle (see later!) • Does not predict the observed splitting of the spectral lines

45. Light as particles and waves In 1905 Einstein showed that the photoelectric effect could be understood if light were thought of as a stream of particles (photons). This seemed to contradict some other experiments that shows light travels as waves. I got my Nobel prize for that.

46. Louis de Broglie (in 1923) If light can behave both as a wave and a particle, I wonder if a particle can also behave as a wave?

47. Louis de Broglie I’ll try messing around with some of Einstein’s formulae and see what I can come up with.

48. I can imagine a photon of light. If it had a “mass” of mp, then its momentum would be given by p = mpc where c is the speed of light.

49. Now Einstein has a lovely formula that he discovered linking mass with energy (E = mc2) and he also used Planck’s formula E = hf. What if I put them equal to each other? mc2 = hf

50. mc2 = hf So for my photon mp = hf/c2 So if p = mpc = hf/c