Monday, December 15, 14. The Natural Sciences

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Alexander McKenzie
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1 The Natural Sciences

2 Problems with the scientific method: 1 - The problem of induction Induction is the process of inferring a general law or principle from the observation of particular instances. Induction lies at the heart of the natural sciences. Example: When I heated water on Friday, it boiled at 100 C When I heated water on Saturday, it boiled at 100 C When I heated water on Saturday, it boiled at 100 C Therefore: Water boils at 100 C The problem of induction is that past experience does not guarantee a particular outcome because we can never be certain that one event causes another or that the two events are simply correlated.

3 Problems with the scientific method: 1 - The problem of induction Math is used to quantify the likelihood, or probability, that an observed relationship is correlative and not causal.

4 Null hypothesis There is no relationship between two measured phenomena P value Statistical measure of the probability of rejecting the null hypothesis when it is, in fact, true Statistical significance - The p value threshold beyond which it is assumed that the null hypothesis can be rejected. This threshold is arbitrary! Bayesian statistics - Statistical measures which investigate probabilities of a an event given the occurrence of another event Pr(A given B) = Pr(B given A)Pr(A)/Pr(B)

The Monty Haul problem There are three doors. Behind one is a prize and behind the other two there are goats. What is your chance of choosing the prize? There are three doors. Behind one is a prize and behind the other two there are goats. You choose door A.

5 The Monty Haul problem There are three doors. Behind one is a prize and behind the other two there are goats. What is your chance of choosing the prize? There are three doors. Behind one is a prize and behind the other two there are goats. You choose door A. I reveal that there is a goat behind door B. What is your chance of winning if you switch your choice to door C?

6 Problems with the scientific method: 2. Confirmation bias Confirmation bias - The tendency to search for or interpret information that confirms one s beliefs or hypotheses

7 From a study published in the Journal of Clinical Psychopharmacology, 2012 Of the industry-supported studies, 97.4 percent reported results that were positive toward the medicine that the study was designed to test, and 2.6 percent reported mixed results. No industry-sponsored studies with negative results were found. In contrast, when industry was not the source of funding, 68.7 percent of the presentations were positive, and 24.1 percent contained mixed results, while 7.2 percent contained negative results. This 'presentation bias', in which mostly good news about medicines gets reported at meetings, echoes the 'publication bias' that has been seen in research published in major journals, says Srijan Sen, M.D., Ph.D. (accessed on at

8 From a study By the British Medical Journal Group in 2003 Results that are unfavourable to the sponsor that is, trials that find a drug is less clinically effective or cost effective or less safe than other drugs used to treat the same condition can pose considerable financial risks to companies. Pressure to show that the drug causes a favourable outcome may result in biases in design, outcome, and reporting of industry sponsored research. A recent systematic review of the impact of financial conflicts on biomedical research found that studies financed by industry, although as rigorous as other studies, always found outcomes favourable to the sponsoring company. (accessed on at

9 What examples or sources of confirmation bias can be seen in the Timmer Article and the NPR piece?

10 Problems with the scientific method: 3. The observer effect The observer effect - The act of observation changes what is observed Measuring the temperature of a glass of water Observing the behavior of animals in the wild Observation of sub atomic particles

11 In quantum mechanics we learn that the behavior of the very smallest objects (like electrons, for example) is very unlike the behavior of everyday things like baseballs. When we throw a baseball at a wall, we can predict where it will be during its flight, where it will hit the wall, how it will bounce, and what it will do afterward. When we fire an electron at a plate with two closely spaced slits in it, and detect the electron on a screen behind these slits, the behavior of the electron is the same as that of a wave in that it can actually go though both holes at once. This may seem odd, but its true. If we repeat this experiment lots of times with lots of electrons, we see that some positions on the screen will have been hit by many electrons and some will have been hit by none. The observed "interference pattern" for these electrons is evidence of their dual wave-particle nature, and is well described by thinking of each electron as a superposition of two "states", one that goes through one slit, one that goes through the other. To add to this already mysterious behavior, this interference will only happen if both possible paths that the electron can take are not distinguishable. In other words, if we could somehow tell which slit the electron went through each time, we would no longer get the interference. The act of making a measurement of the electrons path fundamentally changes the outcome of the experiment (Accessed on at

12 Problems with the scientific method: 4. Background assumptions The background assumptions regarding how the world works can often impact how we interpret the data from scientific observations.

13 Retrograde Motion

Einstein and quantum theory In 1905, Einstein s Special theory of relativity opened the door for the study of quantum mechanics, which holds that the behavior of sub atomic particles is probabilistic

14 Einstein and quantum theory In 1905, Einstein s Special theory of relativity opened the door for the study of quantum mechanics, which holds that the behavior of sub atomic particles is probabilistic and not deterministic. But Eisntein would spend much of the rest of his career in an effort to reject quantum theory... Quantum mechanics is very worthy of regard. But an inner voice tells me that this not yet the right track. The theory yields much, but it hardly brings us closer to the Old One's secrets. I, in any case, am convinced that He does not play dice. (To Max Born, December 4, In Born, Born Einstein Letters, 91. Quoted from Alice Calaprice, ed., The Expanded Quotable Einstein. Princeton University Press, p.245.) It seems hard to sneak a look at God's cards. But that he plays dice and uses 'telepathic' methods (as the present quantum theory requires of him) is something that I cannot believe for a single moment. (To Cornelius Lanczos, March 21, 1942, Einstein Archive, As translated in Albert Einstein: The Human Side. H. Dukas and B. Hoffmann, eds., Princeton: Princeeton Univeristy Press, 1979, p. 68.) (Accessed on at

15 Three models of how science works Inductive verification Falsification - Popper Regular v. Revolutionary science - Kuhn

16 A. Inductive verifiability "What Descartes did was a good step. You have added much several ways, and especially in taking the colours of thin plates into philosophical consideration. If I have seen a little further it is by standing on the shoulders of Giants." Letter from Isaac Newton to Robert Hooke, 1676

17 B. Falsification - Karl Popper Biography Demarcation = Falsifiability

18 I shall certainly admit a system as empirical or scientific only if it is capable of being tested by experience. These considerations suggest that not the verifiability but the falsifiability of a system is to be taken as a criterion of demarcation. In other words: I shall not require of a scientific system that it shall be capable of being singled out, once and for all, in a positive sense; but I shall require that its logical form shall be such that it can be singled out, by means of empirical tests, in a negative sense: it must be possible for an empirical scientific system to be refuted by experience. --Karl Popper, The Logic of Scientific Discovery, p. 18

19 B. Falsification - Karl Popper The process of hypothesis testing is deductive not inductive

20 Hypothesis - Lightning (a) only occurs when humidity is greater than 90% (b) (all a are b ) Observation - Lightening occurs when humidity is at 20% (some a are not b) Therefore: The hypothesis is not true - Lightning does occur when humidity is less than 90% (it is completely certain that the statement all a are b is not true)

21 It should be noted that positive decision can only temporarily support the theory, for subsequent negative decisions may always overthrow it. So long as the theory withstands detailed and severe tests and is not superseded by another theory in the course of scientific progress, we may say that it has proved its mettle or that it is corroborated by past experience. Karl Popper, The Logic of Scientific Discovery, pp. 10

22 B. Falsification - Karl Popper Hypotheses are creative not logical

23 My view of the matter... is that there is no logical method of having new ideas, or a logical reconstruction of this process. My view may be expressed by saying that every discovery contains an irrational element or a creative intuition... In a similar way Einstein speaks of the the search for those highly universal laws... from which a picture of the worlds can be obtained by pure deduction. There is no logical path he says, leading to these... laws. They can only be reached by intuition, based upon something like intellectual love of the objects of experience. Karl Popper, The Logic of Scientific Discovery, pp. 8-9

24 "Any physical theory is always provisional, in the sense that it is only a hypothesis: you can never prove it. No matter how many times the results of experiments agree with some theory, you can never be sure that the next time the results will not contradict the theory. On the other hand, you can disprove a theory by finding even a single observation that disagrees with the predictions of the theory. As philosopher of science Karl Popper has emphasized, a good theory is characterized by the fact that it makes a number of predictions that could in principle be disproved or falsified by observation. Each time new experiments are observed to agree with the predictions the theory survives, and our confidence in it is increased; but if ever a new observation is found to disagree, we have to abandon or modify the theory." Steven Hawking, A Brief History of Time, 10

25 C. Regular v. Revolutionary science - Thomas Kuhn Biography

26 C. Regular v. Revolutionary science - Thomas Kuhn Normal science and paradigms

27 These are the traditions which the historian describes under such rubrics as Ptolomaic astronomy (or Copernican), Aristotelian dynamics (or Newtonian ), corpuscular optics (or wave optics), and so on. The study of paradigms, including many that are far more specialized than those named illustratively above, is what mainly prepares the student for membership in the particular scientific community with which he will later practice. Because he joins men who learned the bases of their field from the same concrete models, his subsequent practice will seldom evoke overt disagreement over fundamentals. Men whose research is based on shared paradigms are committed to the same rules and standards for scientific practice. That commitment and the apparent consensus it produces are prerequisites for normal science, i.e., for the genesis and continuation of a particular research tradition. --Thomas Kuhn, The Structure of Scientific Revolutions, pp.10-11

28 "The man who is striving to solve a problem defined by existing knowledge and technique is not just looking around. He knows what he wants to achieve, and he designs his instruments and directs his thoughts accordingly." --Thomas Kuhn, The Structure of Scientific Revolutions, chapter IV

29 C. Regular v. Revolutionary science - Thomas Kuhn Paradigm shifts and Revolutions

C. Regular v. Revolutionary science - Thomas Kuhn Paradigm Crisis - When discoveries reveal a contradiction between existing theory and observed nature.

30 C. Regular v. Revolutionary science - Thomas Kuhn Paradigm Crisis - When discoveries reveal a contradiction between existing theory and observed nature. Crises are resolved in three ways: Normal science resolves the contradiction The problem is acknowledged, but explained by a lack of adequate tools An alternate paradigm emerges

31 "The normal scientific tradition that emerges from a scientific revolution is not only incompatible but actually incommensurable with that which has gone before. --Thomas Kuhn, The Structure of Scientific Revolutions, chapter IV

32 Led by a new paradigm, scientists adopt new instruments and look in new places. Even more important, during revolutions, scientists see new and different things when looking when looking with familiar instruments in places they have looked before. It is rather as if the professional community had been suddenly transported to another planet where familiar objects are seen in a different light and are joined by unfamiliar ones as well. Of course, nothing of quite that sort does occur: there is not geographical transplantation; outside the laboratory everyday affairs usually continue as before. Nevertheless, paradigm changes do cause scientists to see the world of their research engagements differently. In so far as their only recourse to that world is through what they see and do, we may want to say that after a revolution scientists are responding to a different world. --Thomas Kuhn, The Structure of Scientific Revolutions, p. 111

The Natural Sciences

The Natural Sciences What distinguishes scientific and nonscientific approaches to knowledge: The problem of demarcation v. Science v. Pseudo Science Criticism/ review/ challenge Observation Hypothesis