physics 270 – experimental physics. “the scientific method”
TRANSCRIPT
Physics 270 – Experimental Physics
“The Scientific Method”
Science as a Collection of Facts
Fact 1 Fact 2 Fact 3 …
One possible definition: activities aimed at understanding the natural world
Scientists have shared values and perspectives that characterize a scientific approach to understanding nature: a demand for naturalistic explanations supported by empirical evidence that are testable against the natural world.
Other shared elements include observations, rational argument, inference, skepticism, peer review and reproducibility of work.
Observations of phenomena Experiments Empirical formulas Models Laws / Theory
Let’s do some experiments!
Simplify the phenomenaby creating a model system
on which calculationscan be carried out to
study the phenomena.
Develop multiple approaches since you aren’t sure which one will work.
GoalStart
Painting by Rene Magritte
In science results are presented using precise(though technical) arguments,
…with…testable consequencesfalsifiabilityreproducibility
Experimental VerificationAnd Reproducibility
“Truth” in scienceDescriptions of some aspect of nature in terms of a model. Any view of the natural world that a scientist devises is just a model loaded with assumptions and approximations of that world.
Models, in general, have limited applicability.
As data and technology improve, models are replacedby others which explain a larger range of phenomena.
ReductionReduce a complicated problem into its constituents and aims to understand that complex problem through the study of its components
Wholisma phenomena must be viewed as a
whole in order to understand its structure
Reductionism versus Reductionism versus WholismWholism
Reductionist Example: The Structure of Proteins
Proteins consist of amino acids.These are assembled into ribosomes.The order of assembly is determined by RNA after it is copied from DNA.DNA consists of 4 units called nucleotides.
The structure of proteins is very complicated, but here the problem has been reduced to the assemblage of simpler building blocks.
Holistic Example: An ant hill
Complex physical, chemical, and biological structure built and sustained by millions of ants.
Cannot be understood by braking the ants into tiny parts.
Its essence is in the complexity of the whole.
Deduction – logical development of the consequences of an explanation
starts with theoretical model ⇒ testable prediction ⇒ observations under specific
conditions⇒ confirmation or rejection of
the prediction and/or the model
• Enrico Fermi proposed the existence of the neutrino in 1930 because the observed decay products from beta decay seemed to violate mass and energy conservation.
• In 1956, Cowen and co-workers detected its existence.
Induction – generalization of observed patterns
starts with observations⇒observed patterns⇒development of model⇒testable predictions⇒competition of models⇒theory
Deduction versus Deduction versus InductionInduction
• John Snow in 1854 observed that patients who had contracted cholera had been drinking water from a particular pump in London.
• He suspected that the cholera was spread by contaminated water.
• Led to Louis Pasteur’s formulation of germ theory in 1857.
• Bacteria and viruses were later confirmed by direct observation, establishing their connection to disease.
http://espanol.video.yahoo.com/watch/327162/2140779
Circular Reasoning – Begging the question
Appeal to emotion Argument from authority Sweeping Generalization Irrelevant Conclusion Denying the antecedent
FallaciesFallacies
For a given measureable parameter, there exists a true value of that parameter for a set of circumstances at a given time.
We do not know what it is, nor do we have any independent means of knowing it.
Precision versus Accuracy
Probabilistic versus Deterministic Models