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119-518: In Aristotelian physics , the term was applied to four spherical natural places , concentrically nested around the center of the Earth, as described in the lectures Physica and Meteorologica . They were believed to explain the motions of the four terrestrial elements : Earth , Water , Air , and Fire . In modern texts and in Earth system science , geosphere refers to the solid parts of

238-435: A hypothesis , which is an expectation about how a particular process or phenomenon works. However, an experiment may also aim to answer a "what-if" question, without a specific expectation about what the experiment reveals, or to confirm prior results. If an experiment is carefully conducted, the results usually either support or disprove the hypothesis. According to some philosophies of science , an experiment can never "prove"

357-457: A 'true experiment' is a method of social research in which there are two kinds of variables . The independent variable is manipulated by the experimenter, and the dependent variable is measured. The signifying characteristic of a true experiment is that it randomly allocates the subjects to neutralize experimenter bias , and ensures, over a large number of iterations of the experiment, that it controls for all confounding factors. Depending on

476-484: A constantly operative efficient cause as long as it continues. This commitment appears most starkly to modern eyes in Aristotle’s discussion of projectile motion: what keeps the projectile moving after it leaves the hand? "Impetus", "momentum", much less "inertia", are not possible answers. There must be a mover, distinct (at least in some sense) from the thing moved, which is exercising its motive capacity at every moment of

595-420: A critique of Aristotelian physics where he negated Aristotle's idea that a constant force produces uniform motion, as he realized that a force applied continuously produces acceleration , a fundamental law of classical mechanics and an early foreshadowing of Newton's second law of motion . Like Newton, he described acceleration as the rate of change of speed . In the 14th century, Jean Buridan developed

714-491: A desired chemical compound). Typically, experiments in these fields focus on replication of identical procedures in hopes of producing identical results in each replication. Random assignment is uncommon. In medicine and the social sciences , the prevalence of experimental research varies widely across disciplines. When used, however, experiments typically follow the form of the clinical trial , where experimental units (usually individual human beings) are randomly assigned to

833-410: A disease), and informed consent . For example, in psychology or health care, it is unethical to provide a substandard treatment to patients. Therefore, ethical review boards are supposed to stop clinical trials and other experiments unless a new treatment is believed to offer benefits as good as current best practice. It is also generally unethical (and often illegal) to conduct randomized experiments on

952-424: A hurled body also acquires an inclination (or "motive power") for movement away from whatever caused it to move, an inclination that secures its continued motion. This impressed virtue would be temporary and self-expending, meaning that all motion would tend toward the form of Aristotle's natural motion. In The Book of Healing (1027), the 11th-century Persian polymath Avicenna developed Philoponean theory into

1071-417: A hypothesis, it can only add support. On the other hand, an experiment that provides a counterexample can disprove a theory or hypothesis, but a theory can always be salvaged by appropriate ad hoc modifications at the expense of simplicity. An experiment must also control the possible confounding factors —any factors that would mar the accuracy or repeatability of the experiment or the ability to interpret

1190-410: A logical/ mental derivation. In this process of critical consideration, the man himself should not forget that he tends to subjective opinions—through "prejudices" and "leniency"—and thus has to be critical about his own way of building hypotheses. Francis Bacon (1561–1626), an English philosopher and scientist active in the 17th century, became an influential supporter of experimental science in

1309-632: A man may exercise for the sake of his health: and so "health", and not just the hope of achieving it, is the cause of his action (this distinction is not trivial). But the eyelids are for the sake of the eye (to protect it: PA II.1 3) and the eye for the sake of the animal as a whole (to help it function properly: cf. An II.7). According to Aristotle, the science of living things proceeds by gathering observations about each natural kind of animal, organizing them into genera and species (the differentiae in History of Animals ) and then going on to study

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1428-405: A number in the neighborhood of fifty spheres. An unmoved mover is assumed for each sphere, including a "prime mover" for the sphere of fixed stars . The unmoved movers do not push the spheres (nor could they, being immaterial and dimensionless) but are the final cause of the spheres' motion, i.e. they explain it in a way that's similar to the explanation "the soul is moved by beauty". Unlike

1547-503: A particular factor is manipulated. Experiments vary greatly in goal and scale but always rely on repeatable procedure and logical analysis of the results. There also exist natural experimental studies . A child may carry out basic experiments to understand how things fall to the ground, while teams of scientists may take years of systematic investigation to advance their understanding of a phenomenon. Experiments and other types of hands-on activities are very important to student learning in

1666-418: A strictly controlled test execution with a sensibility for the subjectivity and susceptibility of outcomes due to the nature of man is necessary. Furthermore, a critical view on the results and outcomes of earlier scholars is necessary: 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

1785-405: A test does not produce a measurable positive result. Most often the value of the negative control is treated as a "background" value to subtract from the test sample results. Sometimes the positive control takes the quadrant of a standard curve . An example that is often used in teaching laboratories is a controlled protein assay . Students might be given a fluid sample containing an unknown (to

1904-465: A thing is that of which it is made. For a table, that might be wood; for a statue, that might be bronze or marble. "In one way we say that the aition is that out of which. as existing, something comes to be, like the bronze for the statue, the silver for the phial, and their genera" (194b2 3—6). By "genera", Aristotle means more general ways of classifying the matter (e.g. "metal"; "material"); and that will become important. A little later on, he broadens

2023-535: A treatment or control condition where one or more outcomes are assessed. In contrast to norms in the physical sciences, the focus is typically on the average treatment effect (the difference in outcomes between the treatment and control groups) or another test statistic produced by the experiment. A single study typically does not involve replications of the experiment, but separate studies may be aggregated through systematic review and meta-analysis . There are various differences in experimental practice in each of

2142-757: Is a stub . You can help Misplaced Pages by expanding it . Aristotelian physics Aristotelian physics is the form of natural philosophy described in the works of the Greek philosopher Aristotle (384–322 BC). In his work Physics , Aristotle intended to establish general principles of change that govern all natural bodies, both living and inanimate, celestial and terrestrial – including all motion (change with respect to place), quantitative change (change with respect to size or number), qualitative change, and substantial change (" coming to be " [coming into existence , 'generation'] or "passing away" [no longer existing, 'corruption']). To Aristotle, 'physics'

2261-457: Is a point to describing the world in such teleologically loaded terms: it makes sense of things in a way that atomist speculations do not. And further, Aristotle’s talk of species-forms is not as empty as his opponents would insinuate. He doesn't simply say that things do what they do because that's the sort of thing they do: the whole point of his classificatory biology, most clearly exemplified in PA ,

2380-432: Is a procedure similar to the actual experimental test but is known from previous experience to give a positive result. A negative control is known to give a negative result. The positive control confirms that the basic conditions of the experiment were able to produce a positive result, even if none of the actual experimental samples produce a positive result. The negative control demonstrates the base-line result obtained when

2499-534: Is a uniform circular motion at a given rate (relative to the diurnal motion of the outermost sphere of fixed stars). The concentric, aetherial, cheek-by-jowl " crystal spheres " that carry the Sun, Moon and stars move eternally with unchanging circular motion. Spheres are embedded within spheres to account for the "wandering stars" (i.e. the planets , which, in comparison with the Sun, Moon and stars, appear to move erratically). Mercury, Venus, Mars, Jupiter, and Saturn are

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2618-557: Is about universal forms , in so far as they have been successfully understood, based on our memory of having encountered instances of those forms directly. Aristotle’s theory of cognition rests on two central pillars: his account of perception and his account of thought. Together, they make up a significant portion of his psychological writings, and his discussion of other mental states depends critically on them. These two activities, moreover, are conceived of in an analogous manner, at least with regard to their most basic forms. Each activity

2737-406: Is clearly impossible, when testing the hypothesis "Stars are collapsed clouds of hydrogen", to start out with a giant cloud of hydrogen, and then perform the experiment of waiting a few billion years for it to form a star. However, by observing various clouds of hydrogen in various states of collapse, and other implications of the hypothesis (for example, the presence of various spectral emissions from

2856-484: Is closely related to essence and definition . He says for example that the ratio 2:1, and number in general, is the cause of the octave . "Another [cause] is the form and the exemplar: this is the formula (logos) of the essence (to ti en einai) , and its genera, for instance the ratio 2:1 of the octave" ( Phys 11.3 194b26—8)... Form is not just shape... We are asking (and this is the connection with essence, particularly in its canonical Aristotelian formulation) what it

2975-519: Is everywhere the cause of order. While consistent with common human experience, Aristotle's principles were not based on controlled, quantitative experiments, so they do not describe our universe in the precise, quantitative way now expected of science. Contemporaries of Aristotle like Aristarchus rejected these principles in favor of heliocentrism , but their ideas were not widely accepted. Aristotle's principles were difficult to disprove merely through casual everyday observation, but later development of

3094-410: Is generated and destroyed. Will this be, or not? Yes, if this happens; otherwise not ( Metaphysics VI, 1027a29). Aristotle argues against the indivisibles of Democritus (which differ considerably from the historical and the modern use of the term " atom "). As a place without anything existing at or within it, Aristotle argued against the possibility of a vacuum or void. Because he believed that

3213-470: Is likewise a concentric shell surrounding that of water; bubbles rise in water. Finally, the natural place of fire is higher than that of air but below the innermost celestial sphere (carrying the Moon). In Book Delta of his Physics (IV.5), Aristotle defines topos (place) in terms of two bodies, one of which contains the other: a "place" is where the inner surface of the former (the containing body) touches

3332-926: Is possible depends on the observed correlation between explanatory variables in the observed data. When these variables are not well correlated, natural experiments can approach the power of controlled experiments. Usually, however, there is some correlation between these variables, which reduces the reliability of natural experiments relative to what could be concluded if a controlled experiment were performed. Also, because natural experiments usually take place in uncontrolled environments, variables from undetected sources are neither measured nor held constant, and these may produce illusory correlations in variables under study. Much research in several science disciplines, including economics , human geography , archaeology , sociology , cultural anthropology , geology , paleontology , ecology , meteorology , and astronomy , relies on quasi-experiments. For example, in astronomy it

3451-607: Is the adult plant, for a ball at the top of a ramp, it is coming to rest at the bottom, for an eye, it is seeing, for a knife, it is cutting. Goals have an explanatory function: that is a commonplace, at least in the context of action-ascriptions. Less of a commonplace is the view espoused by Aristotle, that finality and purpose are to be found throughout nature, which is for him the realm of those things which contain within themselves principles of movement and rest (i.e. efficient causes); thus it makes sense to attribute purposes not only to natural things themselves, but also to their parts:

3570-441: Is the definition of the animal’s substantial being ( GA I.1 715a4: ho logos tês ousias ). The final cause is the adult form, which is the end for the sake of which development takes place. The four elements make up the uniform materials such as blood, flesh and bone, which are themselves the matter out of which are created the non-uniform organs of the body (e.g. the heart, liver and hands) "which in turn, as parts, are matter for

3689-417: Is the step in the scientific method that helps people decide between two or more competing explanations—or hypotheses . These hypotheses suggest reasons to explain a phenomenon or predict the results of an action. An example might be the hypothesis that "if I release this ball, it will fall to the floor": this suggestion can then be tested by carrying out the experiment of letting go of the ball, and observing

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3808-460: Is there any definite cause for an accident, but only chance (τύχη, týche ), namely an indefinite (ἀόριστον, aóriston ) cause" ( Metaphysics V, 1025a25). It is obvious that there are principles and causes which are generable and destructible apart from the actual processes of generation and destruction; for if this is not true, everything will be of necessity: that is, if there must necessarily be some cause, other than accidental, of that which

3927-526: Is to be some thing. And it is a feature of musical harmonics (first noted and wondered at by the Pythagoreans) that intervals of this type do indeed exhibit this ratio in some form in the instruments used to create them (the length of pipes, of strings, etc.). In some sense, the ratio explains what all the intervals have in common, why they turn out the same. The efficient cause of a thing is the primary agency by which its matter took its form. For example,

4046-620: Is to show what sorts of function go with what, which presuppose which and which are subservient to which. And in this sense, formal or functional biology is susceptible of a type of reductionism. We start, he tells us, with the basic animal kinds which we all pre-theoretically (although not indefeasibly) recognize (cf. PA I.4): but we then go on to show how their parts relate to one another: why it is, for instance, that only blooded creatures have lungs, and how certain structures in one species are analogous or homologous to those in another (such as scales in fish, feathers in birds, hair in mammals). And

4165-492: Is triggered by its object – each, that is, is about the very thing that brings it about. This simple causal account explains the reliability of cognition: perception and thought are, in effect, transducers, bringing information about the world into our cognitive systems, because, at least in their most basic forms, they are infallibly about the causes that bring them about ( An III.4 429a13–18). Other, more complex mental states are far from infallible. But they are still tethered to

4284-415: Is won at the expense of any serious empirical content. Mechanism, at least as practiced by Aristotle’s contemporaries and predecessors, may have been explanatorily inadequate – but at least it was an attempt at a general account given in reductive terms of the lawlike connections between things. Simply introducing what later reductionists were to scoff at as "occult qualities" does not explain – it merely, in

4403-506: The Earth's rotation and, in his analysis of what might occur if the Earth were rotating, developed a hypothesis similar to Galileo 's notion of "circular inertia". He described it in terms of the following observational test : Experiment An experiment is a procedure carried out to support or refute a hypothesis , or determine the efficacy or likelihood of something previously untried. Experiments provide insight into cause-and-effect by demonstrating what outcome occurs when

4522-510: The English renaissance . He disagreed with the method of answering scientific questions by deduction —similar to Ibn al-Haytham —and described it as follows: "Having first determined the question according to his will, man then resorts to experience, and bending her to conformity with his placets, leads her about like a captive in a procession." Bacon wanted a method that relied on repeatable observations, or experiments. Notably, he first ordered

4641-515: The Local Void adjacent to our own galaxy ) have the opposite effect: ultimately, bodies off-center are ejected from the void due to the gravity of the material outside. According to Aristotle, there are four ways to explain the aitia or causes of change. He writes that "we do not have knowledge of a thing until we have grasped its why, that is to say, its cause." Aristotle held that there were four kinds of causes. The material cause of

4760-808: The Physics is largely concerned with an analysis of motion, particularly local motion, and the other concepts that Aristotle believes are requisite to that analysis. There are clear differences between modern and Aristotelian physics, the main being the use of mathematics , largely absent in Aristotle. Some recent studies, however, have re-evaluated Aristotle's physics, stressing both its empirical validity and its continuity with modern physics. Aristotle divided his universe into "terrestrial spheres" which were "corruptible" and where humans lived, and moving but otherwise unchanging celestial spheres . Aristotle believed that four classical elements make up everything in

4879-416: The branches of science . For example, agricultural research frequently uses randomized experiments (e.g., to test the comparative effectiveness of different fertilizers), while experimental economics often involves experimental tests of theorized human behaviors without relying on random assignment of individuals to treatment and control conditions. One of the first methodical approaches to experiments in

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4998-448: The natural and human sciences. Experiments typically include controls , which are designed to minimize the effects of variables other than the single independent variable . This increases the reliability of the results, often through a comparison between control measurements and the other measurements. Scientific controls are a part of the scientific method . Ideally, all variables in an experiment are controlled (accounted for by

5117-416: The scientific method challenged his views with experiments and careful measurement, using increasingly advanced technology such as the telescope and vacuum pump . In claiming novelty for their doctrines, those natural philosophers who developed the "new science" of the seventeenth century frequently contrasted "Aristotelian" physics with their own. Physics of the former sort, so they claimed, emphasized

5236-422: The sublunary orb's changeable, terrestrial matter, dragging the rarefied fire and air along underneath as it rotates. Like Homer 's æthere (αἰθήρ)  – the "pure air" of Mount Olympus  – was the divine counterpart of the air breathed by mortal beings (άήρ, aer ). The celestial spheres are composed of the special element aether , eternal and unchanging, the sole capability of which

5355-464: The theory of impetus as an alternative to the Aristotelian theory of motion. The theory of impetus was a precursor to the concepts of inertia and momentum in classical mechanics. Buridan and Albert of Saxony also refer to Abu'l-Barakat in explaining that the acceleration of a falling body is a result of its increasing impetus. In the 16th century, Al-Birjandi discussed the possibility of

5474-495: The Earth ; it is used along with atmosphere , hydrosphere , and biosphere to describe the systems of the Earth (the interaction of these systems with the magnetosphere is sometimes listed). In that context, sometimes the term lithosphere is used instead of geosphere or solid Earth. The lithosphere, however, only refers to the uppermost layers of the solid Earth (oceanic and continental crustal rocks and uppermost mantle). Since space exploration began, it has been observed that

5593-409: The Sun, Moon, planets and stars – are embedded in perfectly concentric " crystal spheres " that rotate eternally at fixed rates. Because the celestial spheres are incapable of any change except rotation, the terrestrial sphere of fire must account for the heat, starlight and occasional meteorites . The lowest, lunar sphere is the only celestial sphere that actually comes in contact with

5712-425: The accuracy of the hypotheses. Experiments can be also designed to estimate spillover effects onto nearby untreated units. The term "experiment" usually implies a controlled experiment, but sometimes controlled experiments are prohibitively difficult, impossible, unethical or illegal. In this case researchers resort to natural experiments or quasi-experiments . Natural experiments rely solely on observations of

5831-410: The advantage that outcomes are observed in a natural setting rather than in a contrived laboratory environment. For this reason, field experiments are sometimes seen as having higher external validity than laboratory experiments. However, like natural experiments, field experiments suffer from the possibility of contamination: experimental conditions can be controlled with more precision and certainty in

5950-571: The amount of some cell or substance in the blood, physical strength or endurance, etc.) and not based on a subject's or a professional observer's opinion. In this way, the design of an observational study can render the results more objective and therefore, more convincing. By placing the distribution of the independent variable(s) under the control of the researcher, an experiment—particularly when it involves human subjects —introduces potential ethical considerations, such as balancing benefit and harm, fairly distributing interventions (e.g., treatments for

6069-433: The answers, for Aristotle, are to be found in the economy of functions, and how they all contribute to the overall well-being (the final cause in this sense) of the animal. According to Aristotle, perception and thought are similar, though not exactly alike in that perception is concerned only with the external objects that are acting on our sense organs at any given time, whereas we can think about anything we choose. Thought

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6188-654: The cause ceases, so does the effect. The cause, according to Aristotle, must be a power (i.e., force) that drives the body as long as the external agent remains in direct contact. Aristotle went on to say that the velocity of the body is directly proportional to the force imparted and inversely proportional to the resistance of the medium in which the motion takes place. This gives the law in today's notation velocity ∝ imparted power resistance {\displaystyle {\text{velocity}}\propto {\frac {\text{imparted power}}{\text{resistance}}}} This law presented three difficulties that Aristotle

6307-478: The causes (in Parts of Animals and Generation of Animals , his three main biological works). The four causes of animal generation can be summarized as follows. The mother and father represent the material and efficient causes, respectively. The mother provides the matter out of which the embryo is formed, while the father provides the agency that informs that material and triggers its development. The formal cause

6426-441: The centuries that followed, people who applied the scientific method in different areas made important advances and discoveries. For example, Galileo Galilei (1564–1642) accurately measured time and experimented to make accurate measurements and conclusions about the speed of a falling body. Antoine Lavoisier (1743–1794), a French chemist, used experiment to describe new areas, such as combustion and biochemistry and to develop

6545-400: The changer of the thing changed". Aristotle’s examples here are instructive: one case of mental and one of physical causation, followed by a perfectly general characterization. But they conceal (or at any rate fail to make patent) a crucial feature of Aristotle’s concept of efficient causation, and one which serves to distinguish it from most modern homonyms. For Aristotle, any process requires

6664-425: The contained body. This definition remained dominant until the beginning of the 17th century, even though it had been questioned and debated by philosophers since antiquity. The most significant early critique was made in terms of geometry by the 11th-century Arab polymath al-Hasan Ibn al-Haytham ( Alhazen ) in his Discourse on Place . Terrestrial objects rise or fall, to a greater or lesser extent, according to

6783-509: The control measurements) and none are uncontrolled. In such an experiment, if all controls work as expected, it is possible to conclude that the experiment works as intended, and that results are due to the effect of the tested variables. In the scientific method , an experiment is an empirical procedure that arbitrates competing models or hypotheses . Researchers also use experimentation to test existing theories or new hypotheses to support or disprove them. An experiment usually tests

6902-551: 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. Thus, a comparison of earlier results with the experimental results is necessary for an objective experiment—the visible results being more important. In the end, this may mean that an experimental researcher must find enough courage to discard traditional opinions or results, especially if these results are not experimental but results from

7021-437: The covariates that can be identified. Researchers attempt to reduce the biases of observational studies with matching methods such as propensity score matching , which require large populations of subjects and extensive information on covariates. However, propensity score matching is no longer recommended as a technique because it can increase, rather than decrease, bias. Outcomes are also quantified when possible (bone density,

7140-483: The data in light of them (though this may be rare when social phenomena are under examination). For an observational science to be valid, the experimenter must know and account for confounding factors. In these situations, observational studies have value because they often suggest hypotheses that can be tested with randomized experiments or by collecting fresh data. Fundamentally, however, observational studies are not experiments. By definition, observational studies lack

7259-516: The design and analysis of experiments occurred in the early 20th century, with contributions from statisticians such as Ronald Fisher (1890–1962), Jerzy Neyman (1894–1981), Oscar Kempthorne (1919–2000), Gertrude Mary Cox (1900–1978), and William Gemmell Cochran (1909–1980), among others. Experiments might be categorized according to a number of dimensions, depending upon professional norms and standards in different fields of study. In some disciplines (e.g., psychology or political science ),

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7378-407: The discipline, experiments can be conducted to accomplish different but not mutually exclusive goals: test theories, search for and document phenomena, develop theories, or advise policymakers. These goals also relate differently to validity concerns . A controlled experiment often compares the results obtained from experimental samples against control samples, which are practically identical to

7497-495: The effect of the treatment (exposure) from the effects of the other covariates, most of which have not been measured. The mathematical models used to analyze such data must consider each differing covariate (if measured), and results are not meaningful if a covariate is neither randomized nor included in the model. To avoid conditions that render an experiment far less useful, physicians conducting medical trials—say for U.S. Food and Drug Administration approval—quantify and randomize

7616-413: The effects of substandard or harmful treatments, such as the effects of ingesting arsenic on human health. To understand the effects of such exposures, scientists sometimes use observational studies to understand the effects of those factors. Even when experimental research does not directly involve human subjects, it may still present ethical concerns. For example, the nuclear bomb experiments conducted by

7735-412: The efficient cause of a baby is a parent of the same species and that of a table is a carpenter, who knows the form of the table. In his Physics II, 194b29—32, Aristotle writes: "there is that which is the primary originator of the change and of its cessation, such as the deliberator who is responsible [sc. for the action] and the father of the child, and in general the producer of the thing produced and

7854-419: The eternal and unchanging celestial aether , each of the four terrestrial elements are capable of changing into either of the two elements they share a property with: e.g. the cold and wet ( water ) can transform into the hot and wet ( air ) or the cold and dry ( earth ). Any apparent change from cold and wet into the hot and dry ( fire ) is actually a two-step process, as first one of the property changes, then

7973-470: The experiment is to measure the response to the stimulus by a test method . In the design of experiments , two or more "treatments" are applied to estimate the difference between the mean responses for the treatments. For example, an experiment on baking bread could estimate the difference in the responses associated with quantitative variables, such as the ratio of water to flour, and with qualitative variables, such as strains of yeast. Experimentation

8092-414: The experimental sample except for the one aspect whose effect is being tested (the independent variable ). A good example would be a drug trial. The sample or group receiving the drug would be the experimental group ( treatment group ); and the one receiving the placebo or regular treatment would be the control one. In many laboratory experiments it is good practice to have several replicate samples for

8211-441: The extent of the ionosphere or plasmasphere is highly variable, and often much larger than previously appreciated, at times extending to the boundaries of the Earth's magnetosphere . This highly variable outer boundary of geogenic matter has been referred to as the "geopause" (or magnetopause ), to suggest the relative scarcity of such matter beyond it, where the solar wind dominates. This geophysics -related article

8330-499: The first coherent alternative to Aristotelian theory. Inclinations in the Avicennan theory of motion were not self-consuming but permanent forces whose effects were dissipated only as a result of external agents such as air resistance, making him "the first to conceive such a permanent type of impressed virtue for non-natural motion". Such a self-motion ( mayl ) is "almost the opposite of the Aristotelian conception of violent motion of

8449-429: The first scholars to use an inductive-experimental method for achieving results. In his Book of Optics he describes the fundamentally new approach to knowledge and research in an experimental sense: We should, that is, recommence 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

8568-443: The following solution to the third problem in the case of a shot arrow. The bowstring or hand imparts a certain 'power of being a movent' to the air in contact with it, so that this  imparted force is transmitted to the next layer of air, and so on, thus keeping the arrow in motion until the power gradually dissipates. In his Physics Aristotle examines accidents (συμβεβηκός, symbebekòs ) that have no cause but chance. "Nor

8687-439: The functioning body as a whole ( PA II. 1 646a 13—24)". [There] is a certain obvious conceptual economy about the view that in natural processes naturally constituted things simply seek to realize in full actuality the potentials contained within them (indeed, this is what is for them to be natural); on the other hand, as the detractors of Aristotelianism from the seventeenth century on were not slow to point out, this economy

8806-449: The ground in similar times. Apart from the natural tendency of terrestrial exhalations to rise and objects to fall , unnatural or forced motion from side to side results from the turbulent collision and sliding of the objects as well as transmutation between the elements ( On Generation and Corruption ). Aristotle phrased this principle as: "Everything that moves is moved by something else. (Omne quod moventur ab alio movetur.)" When

8925-402: The groups and that the groups should respond in the same manner if given the same treatment. This equivalency is determined by statistical methods that take into account the amount of variation between individuals and the number of individuals in each group. In fields such as microbiology and chemistry , where there is very little variation between individuals and the group size is easily in

9044-427: The heavenly bodies "were accountable to the laws of physics ". During his debate with Avicenna , al-Biruni also criticized the Aristotelian theory of gravity firstly for denying the existence of levity or gravity in the celestial spheres ; and, secondly, for its notion of circular motion being an innate property of the heavenly bodies . Hibat Allah Abu'l-Barakat al-Baghdaadi (1080–1165) wrote al-Mu'tabar ,

9163-452: The lab. Yet some phenomena (e.g., voter turnout in an election) cannot be easily studied in a laboratory. An observational study is used when it is impractical, unethical, cost-prohibitive (or otherwise inefficient) to fit a physical or social system into a laboratory setting, to completely control confounding factors, or to apply random assignment. It can also be used when confounding factors are either limited or known well enough to analyze

9282-410: The light of stars), we can collect data we require to support the hypothesis. An early example of this type of experiment was the first verification in the 17th century that light does not travel from place to place instantaneously, but instead has a measurable speed. Observation of the appearance of the moons of Jupiter were slightly delayed when Jupiter was farther from Earth, as opposed to when Jupiter

9401-403: The manipulation required for Baconian experiments . In addition, observational studies (e.g., in biological or social systems) often involve variables that are difficult to quantify or control. Observational studies are limited because they lack the statistical properties of randomized experiments. In a randomized experiment, the method of randomization specified in the experimental protocol guides

9520-429: The manner of Molière’s famous satirical joke, serves to re-describe the effect. Formal talk, or so it is said, is vacuous. Things are not however quite as bleak as this. For one thing, there’s no point in trying to engage in reductionist science if you don’t have the wherewithal, empirical and conceptual, to do so successfully: science shouldn't be simply unsubstantiated speculative metaphysics. But more than that, there

9639-503: The material, formal, efficient, and final causes of things. As regards living things, Aristotle's biology relied on observation of what he considered to be ‘natural kinds’, both those he considered basic and the groups to which he considered these belonged. He did not conduct experiments in the modern sense, but relied on amassing data, observational procedures such as dissection , and making hypotheses about relationships between measurable quantities such as body size and lifespan. nature

9758-454: The mean for each group is expected to be the same. For any randomized trial, some variation from the mean is expected, of course, but the randomization ensures that the experimental groups have mean values that are close, due to the central limit theorem and Markov's inequality . With inadequate randomization or low sample size, the systematic variation in covariates between the treatment groups (or exposure groups) makes it difficult to separate

9877-490: The millions, these statistical methods are often bypassed and simply splitting a solution into equal parts is assumed to produce identical sample groups. Once equivalent groups have been formed, the experimenter tries to treat them identically except for the one variable that he or she wishes to isolate. Human experimentation requires special safeguards against outside variables such as the placebo effect . Such experiments are generally double blind , meaning that neither

9996-460: The modern sense is visible in the works of the Arab mathematician and scholar Ibn al-Haytham . He conducted his experiments in the field of optics—going back to optical and mathematical problems in the works of Ptolemy —by controlling his experiments due to factors such as self-criticality, reliance on visible results of the experiments as well as a criticality in terms of earlier results. He was one of

10115-452: The modern sense of the word). Instead, they are abstractions used to explain the varying natures and behaviors of actual materials in terms of ratios between them. Motion and change are closely related in Aristotelian physics. Motion, according to Aristotle, involved a change from potentiality to actuality . He gave example of four types of change, namely change in substance, in quality, in quantity and in place. Aristotle proposed that

10234-413: The only planets (including minor planets ) which were visible before the invention of the telescope, which is why Neptune and Uranus are not included, nor are any asteroids . Later, the belief that all spheres are concentric was forsaken in favor of Ptolemy 's deferent and epicycle model. Aristotle submits to the calculations of astronomers regarding the total number of spheres and various accounts give

10353-529: The other three terrestrial elements. Other, lighter objects, he believed, have less earth, relative to the other three elements in their composition. The four classical elements were not invented by Aristotle; they were originated by Empedocles . During the Scientific Revolution , the ancient theory of classical elements was found to be incorrect, and was replaced by the empirically tested concept of chemical elements . According to Aristotle,

10472-422: The other. These properties are predicated of an actual substance relative to the work it is able to do; that of heating or chilling and of desiccating or moistening. The four elements exist only with regard to this capacity and relative to some potential work. The celestial element is eternal and unchanging, so only the four terrestrial elements account for "coming to be" and "passing away" – or, in

10591-425: The parts of a natural whole exist for the sake of the whole. As Aristotle himself notes, "for the sake of" locutions are ambiguous: " A is for the sake of B " may mean that A exists or is undertaken in order to bring B about; or it may mean that A is for B’s benefit ( An II.4 415b2—3, 20—1); but both types of finality have, he thinks, a crucial role to play in natural, as well as deliberative, contexts. Thus

10710-525: The projectile type, and it is rather reminiscent of the principle of inertia , i.e. Newton's first law of motion ." The eldest Banū Mūsā brother, Ja'far Muhammad ibn Mūsā ibn Shākir (800-873), wrote the Astral Motion and The Force of Attraction . The Persian physicist, Ibn al-Haytham (965-1039) discussed the theory of attraction between bodies. It seems that he was aware of the magnitude of acceleration due to gravity and he discovered that

10829-408: The projectile’s flight (see Phys VIII. 10 266b29—267a11). Similarly, in every case of animal generation, there is always some thing responsible for the continuity of that generation, although it may do so by way of some intervening instrument ( Phys II.3 194b35—195a3). The final cause is that for the sake of which something takes place, its aim or teleological purpose: for a germinating seed, it

10948-539: 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

11067-473: The qualitative at the expense of the quantitative, neglected mathematics and its proper role in physics (particularly in the analysis of local motion), and relied on such suspect explanatory principles as final causes and "occult" essences. Yet in his Physics Aristotle characterizes physics or the "science of nature" as pertaining to magnitudes ( megethê ), motion (or "process" or "gradual change" – kinêsis ), and time ( chronon ) ( Phys III.4 202b30–1). Indeed,

11186-460: The range of the material cause to include letters (of syllables), fire and the other elements (of physical bodies), parts (of wholes), and even premises (of conclusions: Aristotle re-iterates this claim, in slightly different terms, in An. Post II. 11). The formal cause of a thing is the essential property that makes it the kind of thing it is. In Metaphysics Book Α Aristotle emphasizes that form

11305-417: The ratio of the four elements of which they are composed. For example, earth, the heaviest element, and water, fall toward the center of the cosmos; hence the Earth and for the most part its oceans, will have already come to rest there. At the opposite extreme, the lightest elements, air and especially fire, rise up and away from the center. The elements are not proper substances in Aristotelian theory (or

11424-409: The reagents for the protein assay but no protein. In this example, all samples are performed in duplicate. The assay is a colorimetric assay in which a spectrophotometer can measure the amount of protein in samples by detecting a colored complex formed by the interaction of protein molecules and molecules of an added dye. In the illustration, the results for the diluted test samples can be compared to

11543-747: The results of the observational studies are inconsistent and also differ from the results of experiments. For example, epidemiological studies of colon cancer consistently show beneficial correlations with broccoli consumption, while experiments find no benefit. A particular problem with observational studies involving human subjects is the great difficulty attaining fair comparisons between treatments (or exposures), because such studies are prone to selection bias , and groups receiving different treatments (exposures) may differ greatly according to their covariates (age, height, weight, medications, exercise, nutritional status, ethnicity, family medical history, etc.). In contrast, randomization implies that for each covariate,

11662-422: The results of the standard curve (the blue line in the illustration) to estimate the amount of protein in the unknown sample. Controlled experiments can be performed when it is difficult to exactly control all the conditions in an experiment. In this case, the experiment begins by creating two or more sample groups that are probabilistically equivalent, which means that measurements of traits should be similar among

11781-407: The results. Formally, a hypothesis is compared against its opposite or null hypothesis ("if I release this ball, it will not fall to the floor"). The null hypothesis is that there is no explanation or predictive power of the phenomenon through the reasoning that is being investigated. Once hypotheses are defined, an experiment can be carried out and the results analysed to confirm, refute, or define

11900-421: The results. Confounding is commonly eliminated through scientific controls and/or, in randomized experiments , through random assignment . In engineering and the physical sciences , experiments are a primary component of the scientific method. They are used to test theories and hypotheses about how physical processes work under particular conditions (e.g., whether a particular engineering process can produce

12019-500: The science classroom. Experiments can raise test scores and help a student become more engaged and interested in the material they are learning, especially when used over time. Experiments can vary from personal and informal natural comparisons (e.g. tasting a range of chocolates to find a favorite), to highly controlled (e.g. tests requiring complex apparatus overseen by many scientists that hope to discover information about subatomic particles). Uses of experiments vary considerably between

12138-504: The scientific method as we understand it today. There remains simple experience; which, if taken as it comes, is called accident, if sought for, experiment. The true method of experience first lights the candle [hypothesis], and then by means of the candle shows the way [arranges and delimits the experiment]; commencing as it does with experience duly ordered and digested, not bungling or erratic, and from it deducing axioms [theories], and from established axioms again new experiments. In

12257-461: The speed at which two identically shaped objects sink or fall is directly proportional to their weights and inversely proportional to the density of the medium through which they move. While describing their terminal velocity , Aristotle must stipulate that there would be no limit at which to compare the speed of atoms falling through a vacuum , (they could move indefinitely fast because there would be no particular place for them to come to rest in

12376-444: The speed of an object's motion is proportional to the force being applied (or, in the case of natural motion, the object's weight) and inversely proportional to the density of the medium, he reasoned that objects moving in a void would move indefinitely fast – and thus any and all objects surrounding the void would immediately fill it. The void, therefore, could never form. The " voids " of modern-day astronomy (such as

12495-417: The statistical analysis, which is usually specified also by the experimental protocol. Without a statistical model that reflects an objective randomization, the statistical analysis relies on a subjective model. Inferences from subjective models are unreliable in theory and practice. In fact, there are several cases where carefully conducted observational studies consistently give wrong results, that is, where

12614-463: The student) amount of protein. It is their job to correctly perform a controlled experiment in which they determine the concentration of protein in the fluid sample (usually called the "unknown sample"). The teaching lab would be equipped with a protein standard solution with a known protein concentration. Students could make several positive control samples containing various dilutions of the protein standard. Negative control samples would contain all of

12733-436: The terms of Aristotle's On Generation and Corruption (Περὶ γενέσεως καὶ φθορᾶς), "generation" and "corruption". The Aristotelian explanation of gravity is that all bodies move toward their natural place. For the elements earth and water, that place is the center of the ( geocentric ) universe; the natural place of water is a concentric shell around the Earth because earth is heavier; it sinks in water. The natural place of air

12852-412: The terrestrial spheres: earth , air , fire and water . He also held that the heavens are made of a special weightless and incorruptible (i.e. unchangeable) fifth element called " aether ". Aether also has the name "quintessence", meaning, literally, "fifth being". Aristotle considered heavy matter such as iron and other metals to consist primarily of the element earth, with a smaller amount of

12971-461: The test being performed and have both a positive control and a negative control . The results from replicate samples can often be averaged, or if one of the replicates is obviously inconsistent with the results from the other samples, it can be discarded as being the result of an experimental error (some step of the test procedure may have been mistakenly omitted for that sample). Most often, tests are done in duplicate or triplicate. A positive control

13090-403: The theory of conservation of mass (matter). Louis Pasteur (1822–1895) used the scientific method to disprove the prevailing theory of spontaneous generation and to develop the germ theory of disease . Because of the importance of controlling potentially confounding variables, the use of well-designed laboratory experiments is preferred when possible. A considerable amount of progress on

13209-523: 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. According to his explanation,

13328-443: The variables of the system under study, rather than manipulation of just one or a few variables as occurs in controlled experiments. To the degree possible, they attempt to collect data for the system in such a way that contribution from all variables can be determined, and where the effects of variation in certain variables remain approximately constant so that the effects of other variables can be discerned. The degree to which this

13447-561: The void). Now however it is understood that at any time prior to achieving terminal velocity in a relatively resistance-free medium like air, two such objects are expected to have nearly identical speeds because both are experiencing a force of gravity proportional to their masses and have thus been accelerating at nearly the same rate. This became especially apparent from the eighteenth century when partial vacuum experiments began to be made, but some two hundred years earlier Galileo had already demonstrated that objects of different weights reach

13566-422: The volunteer nor the researcher knows which individuals are in the control group or the experimental group until after all of the data have been collected. This ensures that any effects on the volunteer are due to the treatment itself and are not a response to the knowledge that he is being treated. In human experiments, researchers may give a subject (person) a stimulus that the subject responds to. The goal of

13685-491: The world, in so far as they rest on the unambiguous and direct contact perception and thought enjoy with their objects. The Aristotelian theory of motion came under criticism and modification during the Middle Ages . Modifications began with John Philoponus in the 6th century, who partly accepted Aristotle's theory that "continuation of motion depends on continued action of a force" but modified it to include his idea that

13804-416: Was a broad field including subjects which would now be called the philosophy of mind , sensory experience , memory , anatomy and biology . It constitutes the foundation of the thought underlying many of his works . Key concepts of Aristotelian physics include the structuring of the cosmos into concentric spheres, with the Earth at the centre and celestial spheres around it. The terrestrial sphere

13923-467: Was aware of. The first is that if the imparted power is less than the resistance, then in reality it will not move the body, but Aristotle's relation says otherwise. Second, what is the source of the increase in imparted power required to increase the velocity of a freely falling body? Third, what is the imparted power that keeps a projectile in motion after it leaves the agent of projection? Aristotle, in his book Physics, Book 8, Chapter 10, 267a 4, proposed

14042-503: Was closer to Earth; and this phenomenon was used to demonstrate that the difference in the time of appearance of the moons was consistent with a measurable speed. Field experiments are so named to distinguish them from laboratory experiments, which enforce scientific control by testing a hypothesis in the artificial and highly controlled setting of a laboratory. Often used in the social sciences, and especially in economic analyses of education and health interventions, field experiments have

14161-536: Was made of four elements , namely earth, air, fire, and water, subject to change and decay. The celestial spheres were made of a fifth element, an unchangeable aether . Objects made of these elements have natural motions: those of earth and water tend to fall; those of air and fire, to rise. The speed of such motion depends on their weights and the density of the medium. Aristotle argued that a vacuum could not exist as speeds would become infinite. Aristotle described four causes or explanations of change as seen on earth:

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