02 development of the scientific method
September 04, 2013
http://www.youtube.com/watch?v=AEIn3T6nDAo
Development of the scientific method
Galileo Galilei (1564­1642). One of Galileo's greatest contributions was to recognize that the role of the scientist was not to explain "why" things happened as they do in nature, but only to describe them. In one of his "Dialogues" he asks a colleague why objects fall when released. When the colleague replies that everyone knows that gravity makes them fall, Galileo replies that he has not explained anything, just given it a name
This leads us to Galileo's second major contribution, the description of natural phenomena using mathematics and the appeal to nature through experimentation to see if the description is correct. Francis Bacon (1561­1626) takes credit for providing much of the philosophical basis for our modern scientific method. Bacon's approach was basically experimental, qualitative and inductive.
René Descartes (1596­1650), from France, proposed a different approach to the development of science. Instead of starting with raw facts, ..a combination of pure reason and mathematical logic …. Analytic…breaking down a problem into its parts and arranging them logically,... It is termed "reductionism",.... (Deductive!!)
A Brief History and Philosophy of Physics by Alan J. Slavin, Department of Physics, Trent University, August 1994
But what is inductive reasoning?
Inductive reasoning is making conclusions based on patterns you observe.
The conclusion you reach is called a conjecture
Shapes and inductive reasoning:
Example Which shape is next A, B,C,D or E
This cat is black. That cat is black A third cat is black. Therefore all cats are are black.2
Deductive reasoning, or deduction, starts with a general case and deduces specific instances.
Deduction starts with an assumed hypothesis or theory. This assumption may be well­
accepted or it may be rather more shaky ­­ nevertheless, for the argument it is not questioned.
Example
All men are mortal. Joe is a man. Therefore Joe is mortal. If the first two statements are true, then the conclusion must be true.2
Descartes' "mathematical­deductive" approach was diametrically opposed to Bacon's "qualitative­inductive" method, whereas modern science uses a combination of the two.
Summary
Galileo ­
Bacon ­ Descartes ­ Our current approach is a combination of all these ideas
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02 development of the scientific method
September 04, 2013
History of Measurement
http://www.historyworld.net/wrldhis/PlainTextHistories.asp?historyid=ac07
an inch
http://physics.nist.gov/cuu/Units/history.html
metric system
Scientific Method ­ many interpretations here is one http://teacher.nsrl.rochester.edu/phy_labs/AppendixE/AppendixE.html
High School Labs
Purpose of our labs will be to test the validity of some accepted theories. How do we do this 1. Observations ­ qualitative observations are made without inference ­ not the time for reasoning (inductive or deductive) (Bacon)
­ quantitative observations are made with a measurement uncertainty (this will allow for a proper logical argument about the validity of the results
­ Descartes) instrumental ­ based on the limitation of the instrument procedural ­ based on the limitation of the procedure http://www2.selu.edu/Academics/Faculty/rallain/plab194/error.html
http://antoine.frostburg.edu/cgi­bin/senese/tutorials/sigfig/index.cgi
Measurements and Significant Digits
Two axioms
­No measurement is exact
­All counted values are exact
In any measured value, the experimenter is allowed to guess at one digit ­ this determines the "certainty" of the measure. Some measures are given with the uncertainty.
The diameter of the orange is
.
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02 development of the scientific method
September 04, 2013
2. Data manipulation ­ The quantitative observations are manipulated according to the logically developed background theory. At the same time, since we are testing this theory, ideally we are attempting to compare two values which theory says should be equal. Add uncertainties when adding/subtracting, add % values when multiplying/dividing see pg 756
The guess digit reflects the number of digits that the audience should consider as significant. (significant digits) Any calculation using this measure should honour the uncertainty in the measure by not recording too many digits in the outcome. The general rule is to not include more significant digits than the least precise measure in the question but this is only a simple rule.
In theory when multiplying and dividing when adding and subtracting
3. Results summary ­ This apparent obvious task is not obvious. Bacon's inductive reasoning suggest the search for patterns. In addition to patterns, statistical tools can be used to create a numerical representation of how close your determined values were to theory. (Descartes) Precision and accuracy are the two important concepts.
4. Discussion ­ Here is where the reasoning takes place. You have collected unbiased data (Bacon). You have manipulated it according to a logically developed theory (Descartes) and have determined in an unbiased fashion, an acceptable range of error in any difference (Descartes). Now you want to challenge the validity of this theory according to the ideals of the scientific method. 3
02 development of the scientific method
September 04, 2013
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