The experimental method In Physics

The birth of physical science, as it is currently understood, is placed in the 17th century. Before then many scholars had ventured with the study of nature and its forms, and in some fields even good levels of knowledge were reached (for example, Assyrians, Sumerians and Egyptians from the second millennium BC studied the planets and constellations and had elaborated lunar and solar calendars). The study of science, however, had always been proper to philosophical investigation, which studied natural phenomena through logical reasoning, but without resorting to experimental tests. Already in the fifth century. BC the Greek philosopher Democritus (about 460-370 BC) hypothesized that matter was made up of indivisible particles, which he called atoms.

 A little later Aristotle (384-322 BC ) organized scientific knowledge in the form of propositions and logical connections and conceived physics as a complex of sciences (including astronomy, medicine, botany and zoology) which dealt with the study of natural phenomena. The philosophical investigation of nature only aimed to find the reasons for the phenomena, but not to establish how these phenomena occurred. Aristotelian theories in the scientific field were made their own by the Catholic Church and became a dogma. In the 1600s the Pisan scientist Galileo Galilei (1564-1642), who laid the foundations of classical mechanics, questioned some fundamental principles (he supported, for example, the theory according to which the Earth rotates around the Sun and not vice versa and for this was persecuted and condemned by the Church). Galileo is known above all because he outlined a new way of proceeding in scientific investigation, now known as an experimental method. Galileo never wrote a treatise on the method, and never clarified what exactly were the links between what he called “sensible experiences” (experiments) and “mathematical demonstrations” (the laws that regulate phenomena, written in mathematical form ), but the procedures that he followed in the investigation of nature have been derived indirectly from his writings and still constitute the basis of any serious scientific methodology.

The phases of the experimental method

The phases through which the experimental method (or scientific method) is articulated, which marks the transition between modern science and the science of classical antiquity, can essentially be traced back to the following three: observation of phenomena, formulation of theory and experimental verification.

Observation is the first level of knowledge of phenomena. The collection of the observed data must take place using measurable quantities , since only through the measurement it is possible to correspond to each phenomenon a number. It is therefore necessary to proceed to the measurement of the phenomena and in this lies the first innovation compared to classical science, where the observation of the phenomena was mainly qualitative. The observation must instead provide a quantitative point of view of the phenomenon that is observed, therefore it must take into consideration strictly measurable quantities, isolating the phenomenon from external influences that could modify the measures.

The second phase concerns the formulation of the theory, which links the quantities observed through mathematical relationships (read). The theory does not derive directly from the observations, but is elaborated to explain them and must be subsequently verified through the experiment. A scientific theory is made up of a set of hypotheses capable of interpreting a large number of experimental data. The theory has the task of elaborating in a systematic form the general principles from which to deduce the laws that govern matter, written in mathematical form. A theory cannot be fully explained through an experiment, but it must be at least in part, or rather its consequences must be. The verification of a part of it is valid in support of the whole theory, if there is a congruent logical-mathematical system that binds its various parts. Furthermore, a theory must be able to predict the results of experiments still to be performed.

The logical procedure leading from the hypothesis to the conclusions is called the deductive method.

The experimental verification represents the third and final phase of the method. In this phase, through the use of controlled experiences in the laboratory, the scientist must verify the hypotheses of which the theory is composed. If the experiment, repeated several times, confirms the validity of the hypothesis, this is considered true. On the other hand, it is difficult to establish where the error occurred if the hypothesis is false, because the possible sources of error in an experiment are manifold.

One possibility however relates to the fact that the hypothesis is wrong, and therefore to be abandoned. This point is very important in modern science, since it establishes that no theory represents an absolute truth, but each must be verified and, if it is wrong, it must be replaced with a new theory, which is better suited to the experimental results than the old one or which explains more cases. In certain circumstances in modern physics the old theory, although not explaining more experimental evidence, has not been abandoned, but has remained valid in relation to its level of depth, while it is replaced by a new, more complete theory, for a level of depth higher (is the case of quantum mechanics, which replaces classical mechanics in the case of

The use of models in physics

Since physical phenomena are often extremely complex, and their reproduction in the laboratory would be impossible under controlled conditions, models are often used. A model is a simplification of physical reality, the purpose of which is to provide an analogy, or an image of the phenomenon to be observed, which reproduces its behavior and which is reproducible in the laboratory. Often a model provides only a structural similarity with the behavior of the phenomenon in nature, but it is very useful for understanding its mechanisms. It can be said that light waves behave like straight beams, and through this simplification explain some of the behaviors of light radiation, but to fully explain it a more complete theory is needed

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