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SMU CFB 3333 - Lecture Notes

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http www physics smu edu pseudo IF YOU WERE NOT HERE LAST WEEK PLEASE COME TO THE FRONT OF THE CLASS AND SEE PROF COTTON http www physics smu edu pseudo Any sufficiently advanced technology is indistinguishable from magic Arthur C Clarke Profiles of The Future 1961 Clarke s third law English physicist science fiction author 1917 2008 The Bible shows the way to go to heaven not the way the heavens go Galileo Galilei By denying scientific principles one may maintain any paradox Galileo Galilei http www physics smu edu pseudo The Scientific Method continued Supplementary Material for CFB3333 PHY3333 Professors John Cotton and Stephen Sekula January 23 2012 Based on the following information on the web http www physics smu edu pseudo SciMeth http www physics smu edu pseudo But first some MAGIC http www physics smu edu pseudo A round of applause for SCALISE IL MAGNIFICO Wonder at his powers of levitation Gasp as he commands the elements of nature http www physics smu edu pseudo GLOSSARY OF CRITICAL DEFINITIONS http www physics smu edu pseudo FACT The National Academy of Sciences definition of fact An observation that has been repeatedly confrmed and for all practical purposes is accepted as true In science fact can only mean confirmed to such a degree that it would be perverse to withhold provisional assent I suppose that apples might start to rise tomorrow but the possibility does not merit equal time in physics classrooms Stephen Jay Gould EXAMPLE At Standard Temperature and Pressure lead is more dense than water http www physics smu edu pseudo THEORY The National Academy of Sciences definition of theory A well substantiated explanation of some aspect of the natural world that can incorporate facts laws inferences and tested hypotheses Theories are not easily discarded new discoveries are first assumed to fit into the existing theoretical framework It is only when after repeated experimental tests the new phenomenon cannot be accommodated that scientists seriously question the theory and attempt to modify it EXAMPLE Einstein s Special Theory of Relativity which assumes that the speed of light is the same for all observers and all observers observe the same events even if they disagree on why they occurred it predicts that time slows down for observers in motion space contracts according to observers in motion the speed of light is the fastest that anything can travel and that mass is another form of energy These predictions have all been confirmed repeatedly by every test applied so far http www physics smu edu pseudo CONSTRUCT A construct is a non testable statement to account for a set of observations The living organisms on Earth may be accounted for by the statement God made them or the statement They evolved The first statement is a construct the second a theory Most biologists would even call evolution a fact Michael Shermer Why People Believe Weird Things pg 20 http www physics smu edu pseudo OCCAM S RAZOR Occam s razor is a logical principle attributed to the mediaeval philosopher William of Occam or Ockham 1285 1349 The principle states that one should not make more assumptions than the minimum needed This principle is often called the principle of parsimony It underlies all scientific modeling and theory building It admonishes us to choose from a set of otherwise equivalent models of a given phenomenon the simplest one In any given model Occam s razor helps us to shave off those concepts variables or constructs that are not really needed to explain the phenomenon By doing that developing the model will become much easier and there is less chance of introducing inconsistencies ambiguities and redundancies http www physics smu edu pseudo OCCAM S RAZOR EXAMPLE The structure of the Solar System is a good example of the application of Occam s Razor The geocentric Earth centered system requires planets circling about empty points with epicycles added to account for the non uniform motions Copernicus heliocentric Sun centered model solved the problems without need for epicycles and the associated assumptions Adding epicycles is now modern jargon for complicating an explanation beyond the point of confidence it may be time to stop trying to make the old explanation work and start looking for a new hypothesis Occam s Razor is a heuristic which means that it does not have a theoretical base It is something that is usually good to do Important to be aware that heuristics can fail theoretically derived rules normally don t http www physics smu edu pseudo HAS OCCAM S RAZOR EVER FAILED Sure Almost every time The Universe is complicated and the simplest explanation is probably not correct Then why use Occam s Razor Because one should only add new assumptions when forced to do so by the evidence not on a whim Occam s Razor keeps Science on track by not allowing it to wander too far afield http www physics smu edu pseudo ASSUMPTIONS An ASSUMPTION is something taken to be true without proof Assumptions are necessary because nobody knows everything An assumption is not necessarily a guess sometimes an assumption is made based on some knowledge of the situation You might call it an educated guess This is in contrast to what is known as a WAG wildass guess in which the guesser really knows nothing and is making random propositions http www physics smu edu pseudo SKEPTIC A skeptic asks for evidence before accepting a claim Anecdotes and everyone knows it aren t enough Skeptics are open minded enough to look at evidence and decide whether to accept the claim but not so open minded that their brains fall out Take careful note of the phrase Extraordinary claims require extraordinary evidence It s from Carl Sagan Whenever someone makes a really far out claim DON T just take it at face value Ask for some real evidence in support of the claim http www physics smu edu pseudo DENIER A Denier is often confused with a Skeptic THEY ARE NOT THE SAME THING A DENIER is someone for whom there is never enough evidence There are many many many kinds of deniers Holocaust Deniers AIDS HIV Deniers Global Climate Change Deniers Evolution Deniers 9 11 Deniers Presidential Birth Certificate Deniers http www physics smu edu pseudo CYNIC A cynic questions everybody s motives figuring all actions are self interested and or self serving A real cynic is annoying There are however some times when a cynical approach is useful even helpful We mean simply that there are some times that a cynical approach will get you the


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