Lectures and laboratories activities on the nature of Physics and concepts and models in optic: 1. Scientific sentences Alberto Stefanel Research Unit in Physics Education University of Udine
Which of the followings are scientific questions? Our life continues after death? If I open my fingers what happens to the pen I hold? If in the sky there are black clouds, it is better to take an umbrella? What happens tossing a coin? Today it is better than yesterday?
How do establish that a question is a scientific question? The problem of the identification of a borderline criterion, theproblem of demarcation(popper): distinguishing: - the scientific from the unscientific - science by pseudo-science - physics by metaphysics
The greeknaturalphylosophersfoundedthe question of the scientific methodology: whatand how Which questions are important about knowledge on nature? Talete, Anassimandro, Anassimene, Eraclito, Parmenides..: existence of a prime principle of all things Talete 625-547 b.c.) (thisand the otherpicturesof phylosofer are from (Wikipedia) Archéor principle of all natural process ( water, air, fire, infinite ) Now the problem of physics is to find the ultimate constituents of the universe (quark, fermion, boson fields)
Pitagoras: the arché coincides with the number (integer number) Plato and the «World of Ideas» Knowledge research process = recall the ideas world Pitagoras 575-495 b.c. The science of today: the mathematization of the language Parmenides 515 a.c: - Unitarityof the being - Un-changebilityof the being Plato 429-348 b.c. The physics of today: the principles of conservation
Subject of knowledge: - what we can perceive with sense How speak about: -Using an universal methodology (foundation of the method) Aristotles 384-322 a.c Aristoteles described the method of natural philosophy: - Find the causes of changes - Identify the universals - apodictic certainty - Structure of argumentation: definitions, axioms, logical connection (syllogism)
The method of Aristotelesinfluenced the science development (The elements of Euclide, the PhilosophiaeNaturalisPrincipia of Newton) but at the same time the conceptions of Aristoteleshindered the born of the scientific vision of the world Why? Because of the methodology of analysis about the things. The paper sheet example Slowly fall down Fast fall down The same for all the two
Galileo Galilei 1564 1642 Mathematic as language of science (neopitagorism, neoplatonism) «Philosophy is written in this very big book open in front of us, but we need to learn his language. It is written in mathematical language and the characters are triangles, circles and other geometrical figures.» Technique: important as well as the reasoning Mech-lab of the Naval academy of Venice Personal mechanic-lab directed by Marcantonio Mazzoleno Mental experiment: - accidental things can be eliminated - The effects of inherent and crucial aspects can be better appreciated performing ideal/thought experiments Leaving a ball from the taller trees of a ship.
Neopositivism and logical empirism( «Vienna Circle» 1920) Moritz Shlick, Phisicistand phylosopherform Max Plank institute, Rudolph Carnap, O. Neurath, Assumption of Neo -positivism: coincidence of human rationality and scientific rationality Neo-positivism refuse meta-physic The analysis of language is the only way to express rationality The true knowledge is the objective knowledge Objectivism (physics): inter-subjective sharing about empirical phenomenological evidence Meta-physics: cannot express this accord on the empirical data, because do not exist empirical data in metaphysics.
The criteria of the borderline of the scientific knowledge of the scientific discourse Ludwig Wittgenstein: the principle of verification (verificationism) The true knowledge cannot emerge from empirical data but any logical conclusion is without content if there is no relation with empirical data. Wittgenstein establish, therefore (principle of verification): The only sentences having scientific meaning are that than can be empirically verified. What is objective: is the method of analysis on the natural world
Popper s Criticism to the verification principle The verification principle would establish a borderline criteria between what it is possible to verify empirically and what cannot be verified.. but any empirical data cannot be never verified (the physical law are verified one time, two times, 10 times.but not in all the cases) The verification principle for that is not a good criteria to individuate the borderline
Falsification principle (Popper) Logically to verify a theory, a law we need to perform an infinite numbers of experiments Logically to falsify a Theory, a law we need just a single negative results The metaphysical theory are not part of science because they cannot be falsified Ok: it is a logically consistent criterion But any consolidated theory is never abandoned just because there is a single negative experimental results
Thomas Kuhn We need to look at historical evolution of science to understand how it works (science as cultural result of the community of scientist) Scientific revolution: singularity periods in which the scientific community leaves an hold theory and adopts a new one (the new paradigm) Between two revolution: normal science development (construction of the core of theories)
Stage 0 Stage 1 Pre-paradigmatic period Acceptance of the paradigm Stage 2 Normal science period Stage 3 Emergence of anomalies interpretative difficulties Change in the scientist leader the old supporters of the old paradigm die, the young supporters of the new paradigm assume the leadership of the scientific community Stage 4 Crisis of the old paradigm Stage 5 Scientific revolution
Paul Feyerabendwas concerned that science itself had no need of a demarcation criterion Feyerabendargued that, within the history of scientific practice, no rule or method can be found that has not been violated or circumvented at some point in order to advance scientific knowledge And moreoverer that Old and new theories are un-commensurable one with respect to the other BothLakatosand Feyerabendsuggest that science is not an autonomous form of reasoning, but is inseparable from the larger body of human thought and inquiry
Today the debate continue but less interest than before Paul R. Thagard (pragmatical definition) - The theory has been less progressive than alternative theories over a long period of time, and faces many unsolved problems; and... - The community of practitioners makes little attempt to develop the theory towards solutions of the problems, shows no concern for attempts to evaluate the theory in relation to others, and is selective in considering confirmations and disconfirmations. Astrology: science during the 17th century, later "pseudoscience" Larry Laudan. None of the past attempts would be accepted by a majority of philosophers ; demarcation criteria a pseudo-problem that would best be replaced by focusing on the distinction between reliable and unreliable knowledge,
Science theory: - Ensemble of knowledge (historically determined) related to a well specified and defined field or phenomenological context of the nature - That can be subject to falsification - on which there Is a sufficient large accord in the community of scientist (of the related field) Scientific sentence/problem/question -A sentence/problem on with a person can put a research question (I can give answer following a reproducible sequence of actions and obtaining a quantitative results compatible with those obtained by the previous one)
Physics We can describe in a formalized way (part of the) phenomena occurring to a system (an object, a living.what do you want observe) from different perspectives, how it: - moves or reacts to an external forces (mechanics mechanical properties) - changes is temperature (thermodynamics thermal properties) - reacts when it interacts with light (Optics optical properties) - reacts to an electric, magnetic or EM field (electromagnetism electric and magnetic properties)