An experiment (from the Latin experimentum “that which has been brought into experience; trial, proof, test, sample”, from experiri ) in the sense of science is a methodical investigation for the empirical acquisition of information ( data ). In contrast to the mere observation or the demonstration of an effect, influencing variables are changed in the experiment. Experiments are needed and carried out in many sciences, for example in natural sciences , engineering , medicine , psychology and sociology . Usually counts or measurements are an important part of the experiment.
The experiment is an essential part of the scientific progress process. With the development of the self-image of science , methodology and instruments , it not only became more and more important for society, but it also changed its character. Galileo Galilei is often seen as the founder of modern measuring research using experiments . In addition, experiments have also become a didactic method .
The Arab mathematician, optician and astronomer Alhazen carried out some of the first experimental experiments with a scientific character . He gained his knowledge of optics through his experiments with the "camera obscura" - stimulated in particular by Ptolemy's mathematical and optical discussions - but at the same time he was the first to write scientific-methodological considerations on inductive-experimental experiments:
“We should, that is, accept the inquiry into its principles and premisses, beginning our investigation with an inspection of the things that exist and a survey of the conditions of visible objects. We should distinguish the properties of particulars, and gather by induction what pertains to the eye when vision takes place and what is found in the manner of sensation to be uniform, unchanging, manifest and not subject to doubt. After which we should ascend in our inquiry and reasonings, gradually and orderly, criticizing premisses and exercising caution in regard to conclusions - our aim in all that we make subject to inspection and review being to employ justice, not to follow prejudice, and to take care in all that we judge and criticize that we seek the truth and not to be swayed by opinion. We may in this way eventually come to the truth that gratifies the heart and gradually and carefully reach the end at which certainty appears; while through criticism and caution we may seize the truth that dispels disagreement and resolves doubtful matters. For all that, we are not free from that human turbidity which is in the nature of man; but we must do our best with what we possess of human power. From God we derive support in all things. "
A strictly checked test execution with sensitivity for the subjectivity and falsifiability of the results by "human nature" is not enough, one must also be critical of the traditional results and theories:
“It is thus the duty of the man who studies the writings of scientists, if learning the truth is his goal, to make himself an enemy of all that he reads, and, applying his mind to the core and margins of its content, attack it from every side. He should also suspect himself as he performs his critical examination of it, so that he may avoid falling into either prejudice or leniency. "
For an objective experiment, it is essential to compare traditional results with experimental findings and, if necessary, to have the courage to reject the traditional documents. In this process, however, it should not be forgotten that humans - as a conditional factor - tend towards subjective opinions and hypotheses and must lead to objectivity through thorough experimentation and self-criticism.
Definition and basic properties
The experiment represents a “question to nature” (in the social sciences: to social reality). This question may be based on a particular hypothesis that one wishes to test; In this sense, Carl Friedrich von Weizsäcker even spoke of an "interrogation" of nature. However, the experiment can also simply consist in bringing about a situation that has not been observed up to that point without a specific hypothesis and being “surprised” by the result. Such experiments are carried out, for example, when the investigation possibilities have expanded, for example through the introduction of a more precise measurement method or the commissioning of a particle accelerator with higher energy. The results can then be discoveries .
Every experiment requires an experimental set-up ; if test persons or other living objects are involved, one speaks of research design . Sometimes the arrangement itself is referred to as "the experiment", especially e.g. For example, if it is designed and manufactured for only one possible experiment and this constitutes the bulk of the experimental work.
Some experiments are inadmissible or at least controversial from an ethical point of view or because dangers have not been sufficiently considered. This is especially true in medicine (see human experimentation , animal experimentation ), but also for example for nuclear weapon tests and genetic engineering .
A distinction must be made between mere scientific observation - for example in astronomy , geology , biology - in which the observed system is not interfered with. Experiment and scientific observation have in common that they are generally based on a theory with subsequent hypotheses and that they are carried out according to plan.
Special features in the individual sciences
Physics, chemistry and related subjects
The experimental situation in the natural sciences can i. A. Manufactured and controlled arbitrarily. Accordingly, reproducibility of the results - replication with the same result by other researchers, at a different location, at a different time - is required as a criterion of credibility.
In many scientific experiments, certain quantities are systematically changed as independent variables of a situation, and the resulting changes in other quantities, the dependent variables, are measured. Other, fundamentally variable variables, which are not varied in the respective experiment, are often referred to as parameters or influencing variables . The classical physics assumed the influence of the observation itself on the observed object can always take appropriate measures be kept negligibly small. The insight that every observer specifically influences the observation result, for example by introducing measurement inaccuracies, has led to the concept of personal equation in the field of astronomy , for example . However, in experiments with quantum objects , the influence of observation cannot be avoided.
An experiment only makes direct statements about the situation prepared with the test arrangement. However, on the concept of consistency and theories are reviewed, the statements of principle unobservable meet as in theoretical physics and cosmology occur.
According to Karl Popper's critical rationalism , (hypo-) theses cannot be proven (verified), but only refuted (falsified). If the experiment does not refute the hypothesis, this can be interpreted as support for the hypothesis, provided the results are relevant to the hypothesis (see falsifiability ).
Since the experiment only provides information about the special case presented, it is controversial whether there are laws of nature in the sense of all-valid generalizations. In the sense of the empirical theory of regularity , the “laws” of nature are merely habitual experiences that have to be confirmed again in every experiment. Axioms and paradigms are expedient assumptions. They are no longer explicitly checked, but play such a large role in subsequent experiments that a discrepancy would be noticed immediately.
Thought experiments are experiments that are carried out in thought, not in reality, in order to gain knowledge within the framework of a theory. Sometimes a thought experiment can later be carried out as a real experiment with improved experimental possibilities.
Experiments in engineering and technology are sometimes similar in design and properties to experiments in scientific research, for example experiments in materials testing , which are used to determine material parameters such as strength or hardness .
In engineering, however, tests are more important than experiments . In contrast to experiments, tests are not causally oriented (“which consequences arise from given causes?”), But are often final oriented (“by which means is a given purpose achieved?”). While experiments refer to theories, are in principle open-ended - even if there are assumptions about the outcome - and are carried out under the ideal framework conditions possible, i.e. with the least possible influence of the environment, realistic framework conditions are chosen for tests. For example, the functionality of the planned technology is tested using prototypes . After a bridge has been completed, a load test is carried out to determine whether the bridge can actually withstand the loads.
If tests are not feasible for economic or ethical reasons, simulations are used. These can be very different depending on the subject. Frequently and universally applicable is z. B. the finite element method .
Psychology, social sciences
In psychological and social science experiments, the influencing variables are i. A. less precisely controllable. Strict reproducibility cannot be required here; instead, validity and reliability are considered. The control of confounding factors is a crucial part of the experiment.
The principle of “ randomization ” developed by RA Fisher as a consequence of the “ceteris paribus clause” is characteristic of a rigorous experiment : The experimental treatment conditions are assigned to the test groups, and to these the test persons at random (“randomized”). This excludes bogus declarations after which z. For example, behavior is described as an effect of the experimental treatment that actually existed beforehand - it was not the new teaching method that led to the better results, the test subjects in this test group had a learning advantage even before the study. The degree to which it is actually randomized is a characteristic used to distinguish the types of experiment. This limitation is of particular concern for experiments in clinical , educational , industrial and organizational psychology . Often, however, a complete randomization is not possible, since groups of clients, students or employees are given for organizational reasons.
The different types of experiments can be distinguished from one another as follows:
- Laboratory experiments versus field experiments: Laboratory experiments enable extensive control of possible interfering variables. Field experiments take place in the "natural" environment.
- Randomized experiments versus quasi-experiments : see research design
Biology, medicine, pharmacology
As far as experiments in biology, medicine, pharmacology, etc. work with groups of individuals, the terms of research design mentioned above are also important here. In medicine, such experiments are usually referred to as clinical studies . In drug development, for example, they are used to determine the dose-effect relationship , but also the side effects .
Didactics of the natural sciences
Experiments serve not only to gain new knowledge in research, but also to convey already known knowledge to learners in schools, universities and vocational training. A distinction is made between demonstration experiments, which are presented and explained by the teacher, and practical experiments, which are carried out and evaluated by the students themselves.
The rules for setting up and carrying out scientific experiments and for their documentation, ie suitable written presentation (see test protocol ) are sometimes referred to as experimentation.
- In an experiment, observation differs from unsystematic perception in that it is aimed at observer independence. In every experiment it can be ruled out that the expectations - or even the mere presence - of the experimenter influences the results of the experiment. Effects that can lead to misinterpretations, such as the confounding effect in psychology or an artifact (social research) , but also gravitational forces that a person exerts on a physical test arrangement, must be avoided by the specific test arrangement.
- The documentation must be sufficiently meaningful. You should u. A. Name and discuss known or possible uncertainties and measurement errors. It should not only provide information about facts and prevailing conditions, but also about hypotheses and intentions; at least nothing essential should be left out. Which facts are essential and which are not differs from discipline to discipline. While the clothing of the experimenter can obviously be left to his choice in a physical experiment, it can influence the behavior of the test subject in psychological experiments (e.g. make the experimenter appear to be formidable or the opposite).
- All observed processes must be documented, including failed attempts (no result ) and those that produce a result other than the expected result, because these can also or precisely provide information and sometimes lead to new hypotheses. The misappropriation of individual test data that would influence the result can happen almost unconsciously; this is especially important in experiments that build a statistical argument .
Development of experimental sub-sciences
Advances in theory, experimentation and interdisciplinarity have led to the development of sub-areas specifically geared towards experiments in some disciplines, such as experimental physics , experimental psychology , experimental economics or experimental archeology . Numerical mathematics can also be viewed as an experimental discipline.
The astronomy had to do without in the past experiments, except for experiments to improve the monitoring technology. Today space travel can be described as experimental astronomy . Every space mission has an experimental character. For example, the first generation of GPS satellites provide protection on board in the event that the general theory of relativity is incorrect.
For a long time, biology was a purely observational science. Today, however, the biological experiment makes it possible, for example, to directly determine the determining effects on an investigated process. Processes that run too slowly or too quickly in nature can also be made observable in experiments by accelerating or slowing down.
- Alhazen - Attempts (965-1039) on optics with the "Camera Obscura"
- Galileo Galilei - Attempts (1623) to free fall
- Otto von Guericke (1663) - Magdeburg hemispheres (effects of air pressure)
- Ole Rømer - first (1676) realistic measurement of the speed of light
- Benjamin Franklin - Proof (1752) that lightning strikes from a thunderstorm are electrical effects
- In 1780 Luigi Galvani discovered galvanism , that muscles can be stimulated by electrical voltage
- Cavendish experiment (1797) to measure the gravitational constant
- Thomas Young - double slit experiment (1802) for the detection of wave properties of light
- Michael Faraday - Experimental series (1831) on electricity and magnetism
- Crossing experiments (1865) with peas by Gregor Mendel
- Michelson-Morley experiment (1881) to measure the independence of the speed of light from the motion of the earth
- Heinrich Hertz - Evidence (1886) of the transmission of electromagnetic waves
- Wilhelm Conrad Röntgen - Discovery (1895) of X-rays
- Blackening of a film by radioactivity ( Becquerel 1896)
- Millikan experiment (1910) to measure the elementary charge by Robert Andrews Millikan
- Ernest Rutherford's scattering experiments (1910), with which he demonstrated the atomic nucleus
- Ivan Pavlov's experiment in conditioning dogs (conditioned reflex )
- Uranium fission (1938) by Otto Hahn and Lise Meitner
- Thor Heyerdahl's replicas of historic ships and his voyages (1947) to research early transportation
- Miller-Urey experiment (1953) Creation of life, amino acids from the primordial atmosphere
- Stanley Milgram's experiment (1961) to investigate a person's willingness to obey a (pseudo) authority ( Milgram experiment )
- Benjamin Libet's Experiment (1979) on the so-called free will .
- Psychological experiment to inattentional blindness (also called Inattentional Blindness and blindness due to inattention known) by Simons and Chabris (1998)
- The nondeterministic experiments according to Paul Watzlawick
- At the LHC, the search for the Higgs boson had its first successes in 2012.
The experiment in art
It is part of the very essence of European art to deal intensively with natural science. In fact, a separation between science and art is not old; Up until the Renaissance , both were considered indispensable components of a humanistic education.
One aspect of the relationship between experiment and art is that artists of all epochs have tried to artistically implement the latest findings, i.e. to work directly on the interpretation of the results. Examples are:
- The invention of the central perspective can actually be assigned to art, and it was only after Albrecht Dürer's Underweysung of measurement with the zirckel un richtscheyt that it became an area of investigation of descriptive geometry .
- The work of Leonardo da Vinci is outstanding , whose works can be interpreted as a direct application of his inventions and experiments.
- The artistic theme appears to be the depiction of viewers - a second-order observation - in the post- Enlightenment period , when Romanticism tried to create a counterbalance to a cosmos that was strictly separated from and superior to humans, as in Caspar David Friedrich's work , in which the viewer of the works can very often observe people in the foreground who are looking at a landscape or the like themselves - often placed in such a way that they can see more than he can.
- Émile Zola viewed his novels ( Le roman expérimental , 1880) as experimental arrangements with, as it were, sociological cognitive value. With this he founded naturalism in literature.
- Eadweard Muybridge's photographic explorations of movement represent both a scientific and an artistic experiment.
- The series of works by René Magritte and MC Escher can be seen as epistemological experiments, albeit without a methodical evaluation.
On the other hand, creating art in its urge for the new is experimental in itself. In contrast to the scientific experiment, the artistic is not necessarily reproducible, in some cases it even deliberately refuses to accept this requirement. Its purpose is to find new ways of expression, of the medium, of seeing or doing things in a way that has not been seen or done before. The creativity makes it possible to develop new forms, combinations perspectives. So in a similar way it represents basic research and tries to expand or check the concept of art . The artistic experiment can also fail, for example because of one's own claims or rejection of the audience.
Examples can be found in experimental film , in parts of contemporary art , in avant-garde or new music , but also in literature . In the postmodern era, parts of the mainstream also contain experimental elements (for example in music videos ). At the same time, decidedly experimental works are rejected by a large part of the audience ( culture industry ) and struggle with financial difficulties, exceptions such as Kubrick's film 2001: A Space Odyssey are rare.
What both forms have in common, however, is that they explicitly represent a question of the world and are a totality of observer, object and observation . And with the strictly scientific research, they share the high demands on ingenuity and inspiration .
Bernd Löbach-Hinter: "Art and Science", Volume 4 - "Experimental Art" (524 pages), Designbuch Verlag, Cremlingen 2016, ISBN 978-3-923971-84-8
The experiment in the law
Legal solutions to problems are often sought experimentally, i. H. designed in anticipation of the productive imagination, then checked and, if they fail the test, corrected. In this search for possible solutions, the previous law specifies the starting conditions and the horizon of understanding for experimental practice, i. H. for tentative advancement in the development of law. Here, the desire to adapt the law to changes in living conditions must always be weighed against the interest in legal certainty, i.e. against the interest not to jeopardize traditional principles of disposition. The considered "improvements" of the law must be checked to see whether they have a sufficient chance of being followed and enforced, and whether the required behavior (e.g. a speed limit in road traffic) is suitable for the legal political end purpose (e.g. to achieve a significant reduction in accidents). Undesirable side effects of a regulation must also be considered (extensive tenant protection law can, for example, lead to fewer rental apartments being built). In addition, the rules under consideration must be capable of consensus for the majority's rational sense of justice. They must also not contradict the legal context or the zeitgeist , i. H. are related to the main ideas of the respective culture.
- Berg, Gunhild: Experimentieren, in: Ute Fritsch u. Jörg Rogge (ed.): About the practice of cultural studies. A concise dictionary. Bielefeld 2013, pp. 138–144.
- Berg, Gunhild: On the boom of the term “experiment” in the natural, social and human sciences, in: Michael Eggers (Ed.): History of science as conceptual history. Terminological changes in the development process of modern science. Bielefeld 2009, pp. 51–82.
- Steven Schwartz: How Pavlov got the dog. The 15 classic experiments in psychology. ISBN 3-407-85102-2 .
- Klaus Hentschel : Myths about famous experiments and experimenters: The fairy tale of the magician in a white coat. In: Physics in Our Time. 34 (5), 2003, , pp. 225-231.
- Séverine Marguin, Henrike Rabe, Wolfgang Schäffner, Friedrich Schmidgall (eds.): Experimentieren. Insights into practices and experimental setups between science and design. transcript, Bielefeld 2019, ISBN 978-3-8376-4638-2 . ( Open access )
- Hans-Jörg Rheinberger : Experiment. Difference. Font. On the history of epistemic things. Basiliken-Presse, Marburg an der Lahn 1992.
- Reto Rössler: About the attempt - experiment and essay. Components for the history of circulation of an implicit genre of the Enlightenment. Berlin (Kulturverlag Kadmos) 2017, ISBN 978-3-86599-332-8 [= study of the DFG project 'Trial' and 'Experiment'. Concepts of experimentation between science and literature (1700–1960) at the University of Innsbruck]
- Reto U. Schneider : The book of crazy experiments. Munich 2006, ISBN 978-3-442-15393-0 .
- Helmar Schramm et al. (Ed.): Spectacular experiments. Evidence Production Practices in the 17th Century. Berlin, New York 2006, ISBN 978-3-11-019300-8 .
- Nieding, G. & Ohler, P. (2004). Laboratory Experimental Methods. In R. Mangold, P. Vorderer & G. Bente, (Eds.). Textbook of media psychology (Chapter 15). Göttingen: Hogrefe.
- Weber, Marcel: Philosophy of Experimental Biology (Cambridge Studies in Philosophy and Biology) , ed.M. Ruse, Cambridge / New York, Cambridge University Press, 2005, ISBN 978-0-521-14344-8
- Reinhold Zippelius : The experimental method in law , academy treatise Mainz, 1991, ISBN 3-515-05901-6
- Literature on experiment in the catalog of the German National Library
- Experiment in Physics. Entry in Edward N. Zalta (Ed.): Stanford Encyclopedia of Philosophy .
- DFG research project on the knowledge history of the experiment
- Speer, A. (2017): Kindler Kompakt. Middle Ages Philosophy. Springer-Verlag GmbH Germany, p. 57 ff.
- Ibn al-Haytham (965-1039) in “Optics”, p. 5
- Ibn al-Haytham (965-1039) in “Dubitationes in Ptolemaeum”, p. 3
- “Reason must go to nature with its principles, according to which only agreed phenomena can apply to laws, in one hand, and with the experiment that it devised based on these, in the other, to nature, in order to be instructed by it , but not in the quality of a pupil who lets himself be told everything the teacher wants, but of an appointed judge who compels the witnesses to answer the questions he puts before them. " Immanuel Kant : Critique of pure reason , Preface to the 2nd edition (1787), B xiii, quoted from the work edition, ed. by Wilhelm Weischedel, Volume 3, 4th edition Frankfurt 1982, p. 23.
- Brockhaus Encyclopedia, 19th edition, Mannheim 1988, keyword “Experiment”.
- Puthz, Volker: Experiment or observation in teaching biology, 132/12, pp. 11-13.
- Herbert Spencer: The Study of Sociology. D. Appleton & Co. New York, 1882 (1873). P. 9f.
- Hans Poser: Homo Creator - Technology as a Philosophical Challenge , Springer, 2016, pp. 176, 307.
- acatech: Technikwissenschaften - Erkennen, Gestalten, Responsen , Springer, 2013, pp. 27–29 (especially p. 29).
- Nieding, G. & Ohler, P. (2004). Laboratory Experimental Methods. In R. Mangold, P. Vorderer & G. Bente, (Eds.). Textbook of media psychology (Chapter 15). Göttingen: Hogrefe.
- interviewers and interviewees in opinion research , cf. Hartmut Esser: Social regularities of respondent behavior. Meisenheim 1975.
- Reinhold Zippelius , The experimental method in law. 1991.
- Reinhold Zippelius, Basic Concepts of Legal and State Sociology, 3rd edition, §§ 4 III, 11.
- Reinhold Zippelius, Basic Concepts of Legal and State Sociology, 3rd edition, § 10.
- Reinhold Zippelius, Basic Concepts of Legal and State Sociology, 3rd edition, § 7 II, III
- Reinhold Zippelius, Philosophy of Law, 6th edition 2011, § 17 I.