about science
scientists, see Natural science. For other uses, see Science (disambiguation). Montage of some highly influential scientists from a variety of scientific fields. From left to right: Top row - Archimedes, Aristotle, Ibn al-Haytham, Leonardo da Vinci, Galileo Galilei, Antonie van Leeuwenhoek; Second row - Isaac Newton, James Hutton, Antoine Lavoisier, John Dalton, Charles Darwin, Gregor Mendel; Third row - Louis Pasteur, James Clerk Maxwell, Henri Poincaré, Sigmund Freud, Nikola Tesla, Max Planck; Fourth row - Ernest Rutherford, Marie Curie, Albert Einstein, Niels Bohr, Erwin Schrödinger, Enrico Fermi; Bottom row - J. Robert Oppenheimer, Alan Turing, Richard Feynman, E. O. Wilson, Jane Goodall, Stephen Hawking Part of a series on Science Formal sciences[show] Physical sciences[show] Life sciences[show] Social and behavioural sciences[show] Applied sciences[show] Interdisciplinarity[show] Philosophy and history of science[show] Science portal Category v t e Science (from Latin scientia, meaning "knowledge") is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe.[1] In an older and closely related meaning (found, for example, in Aristotle), "science" refers to the body of reliable knowledge itself, of the type that can be logically and rationally explained (see History and philosophy below).[2] Since classical antiquity science as a type of knowledge was closely linked to philosophy. In the early modern era the words "science" and "philosophy" were sometimes used interchangeably in the English language. By the 17th century, natural philosophy (which is today called "natural science") was considered a separate branch of philosophy.[3] However, "science" continued to be used in a broad sense denoting reliable knowledge about a topic, in the same way it is still used in modern terms such as library science or political science. In modern use, "science" more often refers to a way of pursuing knowledge, not only the knowledge itself. It is "often treated as synonymous with 'natural and physical science', and thus restricted to those branches of study that relate to the phenomena of the material universe and their laws, sometimes with implied exclusion of pure mathematics. This is now the dominant sense in ordinary use."[4] This narrower sense of "science" developed as scientists such as Johannes Kepler, Galileo Galilei and Isaac Newton began formulating laws of nature such as Newton's laws of motion. In this period it became more common to refer to natural philosophy as "natural science". Over the course of the 19th century, the word "science" became increasingly associated with scientific method, a disciplined way to study the natural world, including physics, chemistry, geology and biology. It is in the 19th century also that the term scientist was created by the naturalist-theologian William Whewell to distinguish those who sought knowledge on nature from those who sought knowledge on other disciplines. The Oxford English Dictionary dates the origin of the word "scientist" to 1834. This sometimes left the study of human thought and society in a linguistic limbo, which was resolved by classifying these areas of academic study as social science. Similarly, several other major areas of disciplined study and knowledge exist today under the general rubric of "science", such as formal science and applied science. Contents [show] History and philosophy History Main article: History of science Both Aristotle and Kuan Tzu (4th C. BCE), in an example of simultaneous scientific discovery, mention that some marine animals were subject to a lunar cycle, and increase and decrease in size with the waxing and waning of the moon. Aristotle was referring specifically to the sea urchin, pictured above.[5] Science in a broad sense existed before the modern era, and in many historical civilizations, but modern science is so distinct in its approach and successful in its results that it now defines what science is in the strictest sense of the term. Much earlier than the modern era, another important turning point was the development of the classical natural philosophy in the ancient Greek-speaking world. Pre-philosophical Science in its original sense is a word for a type of knowledge (Latin scientia, Ancient Greek epistemē), rather than a specialized word for the pursuit of such knowledge. In particular it is one of the types of knowledge which people can communicate to each other and share. For example, knowledge about the working of natural things was gathered long before recorded history and led to the development of complex abstract thinking, as shown by the construction of complex calendars, techniques for making poisonous plants edible, and buildings such as the pyramids. However no consistent distinction was made between knowledge of such things which are true in every community, and other types of communal knowledge such as mythologies and legal systems. Philosophical study of nature See also: Nature (philosophy) Before the invention or discovery of the concept of "nature" (Ancient Greek phusis), by the Pre-Socratic philosophers, the same words tend to be used to describe the natural "way" in which a plant grows,[6] and the "way" in which, for example, one tribe worships a particular god. For this reason it is claimed these men were the first philosophers in the strict sense, and also the first people to clearly distinguish "nature" and "convention".[7] Science was therefore distinguished as the knowledge of nature, and the things which are true for every community, and the name of the specialized pursuit of such knowledge was philosophy — the realm of the first philosopher-physicists. They were mainly speculators or theorists, particularly interested in astronomy. In contrast, trying to use knowledge of nature to imitate nature (artifice or technology, Greek technē) was seen by classical scientists as a more appropriate interest for lower class artisans.[8] Philosophical turn to human things A major turning point in the history of early philosophical science was the controversial but successful attempt by Socrates to apply philosophy to the study of human things, including human nature, the nature of political communities, and human knowledge itself. He criticized the older type of study of physics as too purely speculative, and lacking in self-criticism. He was particularly concerned that some of the early physicists treated nature as if it could be assumed that it had no intelligent order, explaining things merely in terms of motion and matter. The study of human things had been the realm of mythology and tradition, and Socrates was executed. Aristotle later created a less controversial systematic programme of Socratic philosophy, which was teleological, and human-centred. He rejected many of the conclusions of earlier scientists. For example in his physics the sun goes around the earth, and many things have it as part of their nature that they are for humans. Each thing has a formal cause and final cause and a role in the rational cosmic order. Motion and change is described as the actualization of potentials already in things, according to what types of things they are. While the Socratics insisted that philosophy should be used to consider the practical question of the best way to live for a human being, they did not argue for any other types of applied science. Aristotle maintained the sharp distinction between science and the practical knowledge of artisans, treating theoretical speculation as the highest type of human activity, practical thinking about good living as something less lofty, and the knowledge of artisans as something only suitable for the lower classes. In contrast to modern science, Aristotle's influential emphasis was upon the "theoretical" steps of deducing universal rules from raw data, and did not treat the gathering of experience and raw data as part of science itself.[9] Medieval science During late antiquity and the early Middle Ages, the Aristotelian approach to inquiries on natural phenomenon was used. Some ancient knowledge was lost, or in some cases kept in obscurity, during the fall of the Roman Empire and periodic political struggles. However, the general fields of science, or Natural Philosophy as it was called, and much of the general knowledge from the ancient world remained preserved though the works of the early encyclopedists like Isidore of Seville. During the early medieval period, Syrian Christians from Eastern Europe such as Nestorians and Monophysites were the ones that translated much of the important Greek science texts from Greek to Syriac and the later on they translated many of the works into Arabic and other languages under Islamic rule.[10] This was a major line of transmission for the development of Islamic science which provided much of the activity during the early medieval period. In the later medieval period, Europeans recovered some ancient knowledge by translations of texts and they built their work upon the knowledge of Aristotle, Ptolemy, Euclid, and others works. In Europe, men like Roger Bacon learned Arabic and Hebrew and argued for more experimental science. By the late Middle Ages, a synthesis of Catholicism and Aristotelianism known as Scholasticism was flourishing in Western Europe, which had become a new geographic center of science. Renaissance, and early modern science Main article: Scientific revolution Galileo is considered one of the fathers of modern science.[11] By the late Middle Ages, especially in Italy there was an influx of texts and scholars from the collapsing Byzantine empire. Copernicus formulated a heliocentric model of the solar system unlike the geocentric model of Ptolemy's Almagest. All aspects of scholasticism were criticized in the 15th and 16th centuries; one author who was notoriously persecuted was Galileo, who made innovative use of experiment and mathematics. However the persecution began after Pope Urban VIII blessed Galileo to write about the Copernican system. Galileo had used arguments from the Pope and put them in the voice of the simpleton in the work "Dialogue Concerning the Two Chief World Systems" which caused great offense to him.[12] In Northern Europe, the new technology of the printing press was widely used to publish many arguments including some that disagreed with church dogma. René Descartes and Francis Bacon published philosophical arguments in favor of a new type of non-Aristotelian science. Descartes argued that mathematics could be used in order to study nature, as Galileo had done, and Bacon emphasized the importance of experiment over contemplation. Bacon also argued that science should aim for the first time at practical inventions for the improvement of all human life. Bacon questioned the Aristotelian concepts of formal cause and final cause, and promoted the idea that science should study the laws of "simple" natures, such as heat, rather than assuming that there is any specific nature, or "formal cause", of each complex type of thing. This new modern science began to see itself as describing "laws of nature". This updated approach to studies in nature was seen as mechanistic. Age of Enlightenment In the 17th and 18th centuries, the project of modernity, as had been promoted by Bacon and Descartes, led to rapid scientific advance and the successful development of a new type of natural science, mathematical, methodically experimental, and deliberately innovative. Newton and Leibniz succeeded in developing a new physics, now referred to as Newtonian physics, which could be confirmed by experiment and explained in mathematics. Leibniz also incorporated terms from Aristotelian physics, but now being used in a new non-teleological way, for example "energy" and "potential". But in the style of Bacon, he assumed that different types of things all work according to the same general laws of nature, with no special formal or final causes for each type of thing. It is, during this period that the word science gradually became more commonly used to refer to the pursuit of a type of knowledge, and especially knowledge of nature — coming close in meaning to the old term "natural philosophy". 19th century Distinguished Men of Science.[13] Use a cursor to see who is who.[14] Both John Herschel and William Whewell systematised methodology: the latter coined the term scientist. When Charles Darwin published On the Origin of Species he established descent with modification as the prevailing evolutionary explanation of biological complexity. His theory of natural selection provided a natural explanation of how species originated, but this only gained wide acceptance a century later. John Dalton developed the idea of atoms. The laws of Thermodynamics and the electromagnetic theory were also established in the 19th century, which raised new questions which could not easily be answered using Newton's framework. 20th century Einstein's Theory of Relativity and the development of quantum mechanics led to the replacement of Newtonian physics with a new physics which contains two parts, that describe different types of events in nature. The extensive use of scientific innovation during the wars of this century, led to the space race and widespread public appreciation of the importance of modern science. Philosophy of science Main article: Philosophy of science Further information: Intersubjective verifiability and Subjunctive possibility Working scientists usually take for granted a set of basic assumptions that are needed to justify a scientific method: (1) that there is an objective reality shared by all rational observers; (2) that this objective reality is governed by natural laws; (3) that these laws can be discovered by means of systematic observation and experimentation. Philosophy of science seeks a deep understanding of what these underlying assumptions mean and whether they are valid. Most contributions to the philosophy of science have come from philosophers, who frequently view the beliefs of most scientists as superficial or naive—thus there is often a degree of antagonism between working scientists and philosophers of science. John Locke The belief that all observers share a common reality is known as realism. It can be contrasted with anti-realism, the belief that there is no valid concept of absolute truth such that things that are true for one observer are true for all observers. The most commonly defended form of anti-realism is idealism, the belief that the mind or spirit is the most basic essence, and that each mind generates its own reality.[15] In an idealistic world-view, what is true for one mind need not be true for other minds. There are different schools of thought in philosophy of science. The most popular position is empiricism, which claims that knowledge is created by a process involving observation and that scientific theories are the result of generalizations from such observations.[16] Empiricism generally encompasses inductivism, a position that tries to explain the way general theories can be justified by the finite number of observations humans can make and the hence finite amount of empirical evidence available to confirm scientific theories. This is necessary because the number of predictions those theories make is infinite, which means that they cannot be known from the finite amount of evidence using deductive logic only. Many versions of empiricism exist, with the predominant ones being bayesianism[17] and the hypothetico-deductive method.[18] Empiricism has stood in contrast to rationalism, the position originally associated with Descartes, which holds that knowledge is created by the human intellect, not by observation.[19] A significant twentieth century version of rationalism is critical rationalism, first defined by Austrian-British philosopher Karl Popper. Popper rejected the way that empiricism describes the connection between theory and observation. He claimed that theories are not generated by observation, but that observation is made in the light of theories and that the only way a theory can be affected by observation is when it comes in conflict with it.[20] Popper proposed falsifiability as the landmark of scientific theories, and falsification as the empirical method, to replace verifiability[21] and induction by purely deductive notions.[22] Popper further claimed that there is actually only one universal method, and that this method is not specific to science: The negative method of criticism, trial and error.[23] It covers all products of the human mind, including science, mathematics, philosophy, and art [24] Another approach, instrumentalism, colloquially termed "shut up and calculate", emphasizes the utility of theories as instruments for explaining and predicting phenomena.[25] It claims that scientific theories are black boxes with only their input (initial conditions) and output (predictions) being relevant. Consequences, notions and logical structure of the theories are claimed to be something that should simply be ignored and that scientists shouldn't make a fuss about (see interpretations of quantum mechanics). Finally, another approach often cited in debates of scientific skepticism against controversial movements like "scientific creationism", is methodological naturalism. Its main point is that a difference between natural and supernatural explanations should be made, and that science should be restricted methodologically to natural explanations.[26] That the restriction is merely methodological (rather than ontological) means that science should not consider supernatural explanations itself, but should not claim them to be wrong either. Instead, supernatural explanations should be left a matter of personal belief outside the scope of science. Methodological naturalism maintains that proper science requires strict adherence to empirical study and independent verification as a process for properly developing and evaluating explanations for observable phenomena.[27] The absence of these standards, arguments from authority, biased observational studies and other common fallacies are frequently cited by supporters of methodological naturalism as criteria for the dubious claims they criticize not to be true science. Basic and applied research Although some scientific research is applied research into specific problems, a great deal of our understanding comes from the curiosity-driven undertaking of basic research. This leads to options for technological advance that were not planned or sometimes even imaginable. This point was made by Michael Faraday when, allegedly in response to the question "what is the use of basic research?" he responded "Sir, what is the use of a new-born child?".[28] For example, research into the effects of red light on the human eye's rod cells did not seem to have any practical purpose; eventually, the discovery that our night vision is not troubled by red light would lead search and rescue teams (among others) to adopt red light in the cockpits of jets and helicopters.[29] In a nutshell: Basic research is the search for knowledge. Applied research is the search for solutions to practical problems using this knowledge. Finally, even basic research can take unexpected turns, and there is some sense in which the scientific method is built to harness luck. Experimentation and hypothesizing DNA determines the genetic structure of all known life Based on observations of a phenomenon, scientists may generate a model. This is an attempt to describe or depict the phenomenon in terms of a logical, physical or mathematical representation. As empirical evidence is gathered, scientists can suggest a hypothesis to explain the phenomenon.[30] Hypotheses may be formulated using principles such as parsimony (also known as "Occam's Razor") and are generally expected to seek consilience—fitting well with other accepted facts related to the phenomena.[31] This new explanation is used to make falsifiable predictions that are testable by experiment or observation. When a hypothesis proves unsatisfactory, it is either modified or discarded.[32] Experimentation is especially important in science to help establish causational relationships (to avoid the correlation fallacy). Operationalization also plays an important role in coordinating research in/across different fields. Once a hypothesis has survived testing, it may become adopted into the framework of a scientific theory. This is a logically reasoned, self-consistent model or framework for describing the behavior of certain natural phenomena. A theory typically describes the behavior of much broader sets of phenomena than a hypothesis; commonly, a large number of hypotheses can be logically bound together by a single theory. Thus a theory is a hypothesis explaining various other hypotheses. In that vein, theories are formulated according to most of the same scientific principles as hypotheses. While performing experiments, scientists may have a preference for one outcome over another, and so it is important to ensure that science as a whole can eliminate this bias.[33][34] This can be achieved by careful experimental design, transparency, and a thorough peer review process of the experimental results as well as any conclusions.[35][36] After the results of an experiment are announced or published, it is normal practice for independent researchers to double-check how the research was performed, and to follow up by performing similar experiments to determine how dependable the results might be.[37] Certainty and science A scientific theory is empirical, and is always open to falsification if new evidence is presented. That is, no theory is ever considered strictly certain as science accepts the concept of fallibilism. The philosopher of science Karl Popper sharply distinguishes truth from certainty. He writes that scientific knowledge "consists in the search for truth", but it "is not the search for certainty ... All human knowledge is fallible and therefore uncertain."[38] Although science values legitimate doubt, The Flat Earth Society is still widely regarded as an example of taking skepticism too far New scientific knowledge very rarely results in vast changes in our understanding. According to psychologist Keith Stanovich, it may be the media's overuse of words like "breakthrough" that leads the public to imagine that science is constantly proving everything it thought was true to be false.[39] While there are such famous cases as the theory of relativity that required a complete reconceptualization, these are extreme exceptions. Knowledge in science is gained by a gradual synthesis of information from different experiments, by various researchers, across different domains of science; it is more like a climb than a leap.[40] Theories vary in the extent to which they have been tested and verified, as well as their acceptance in the scientific community.[41] For example, heliocentric theory, the theory of evolution, and germ theory still bear the name "theory" even though, in practice, they are considered factual.[42] Philosopher Barry Stroud adds that, although the best definition for "knowledge" is contested, being skeptical and entertaining the possibility that one is incorrect is compatible with being correct. Ironically then, the scientist adhering to proper scientific method will doubt themselves even once they possess the truth.[43] The fallibilist C. S. Peirce argued that inquiry is the struggle to resolve actual doubt and that merely quarrelsome, verbal, or hyperbolic doubt is fruitless[44]—but also that the inquirer should try to attain genuine doubt rather than resting uncritically on common sense.[45] He held that the successful sciences trust, not to any single chain of inference (no stronger than its weakest link), but to the cable of multiple and various arguments intimately connected.[46] Stanovich also asserts that science avoids searching for a "magic bullet"; it avoids the single-cause fallacy. This means a scientist would not ask merely "What is the cause of...", but rather "What are the most significant causes of...". This is especially the case in the more macroscopic fields of science (e.g. psychology, cosmology).[47] Of course, research often analyzes few factors at once, but these are always added to the long list of factors that are most important to consider.[47] For example: knowing the details of only a person's genetics, or their history and upbringing, or the current situation may not explain a behaviour, but a deep understanding of all these variables combined can be very predictive. Scientific practice Astronomy became much more accurate after Tycho Brahe devised his scientific instruments for measuring angles between two celestial bodies, before the invention of the telescope. Brahe's observations were the basis for Kepler's laws. "If a man will begin with certainties, he shall end in doubts; but if he will be content to begin with doubts, he shall end in certainties." —Francis Bacon (1605) The Advancement of Learning, Book 1, v, 8 A skeptical point of view, demanding a method of proof, was the practical position taken as early as 1000 years ago, with Alhazen, Doubts Concerning Ptolemy, through Bacon (1605), and C. S. Peirce (1839–1914), who note that a community will then spring up to address these points of uncertainty. The methods of inquiry into a problem have been known for thousands of years,[48] and extend beyond theory to practice. The use of measurements, for example, are a practical approach to settle disputes in the community. John Ziman points out that intersubjective pattern recognition is fundamental to the creation of all scientific knowledge.[49] Ziman shows how scientists can identify patterns to each other across centuries: Needham 1954 (illustration facing page 164) shows how today's trained Western botanist can identify Artemisia alba from images taken from a 16th c. Chinese pharmacopia,[50] and Ziman refers to this ability as 'perceptual consensibility'.[51] Ziman then makes consensibility, leading to consensus, the touchstone of reliable knowledge.[52] Measurement Main article: Measurement Measurement is often used in science to make definitive comparisons and reduce confusion. Even in cases of clear qualitative difference, increased precision through measurement is often preferred in order to aid in replication. For example, different colors may be reported based on wavelengths of light, instead of vague (qualitative) terms such as "green" and "blue" which are often interpreted differently by different people. Measurements are most commonly made in the SI system, which contains seven fundamental units: kilogram, meter, candela, second, ampere, kelvin, and mole. Six of these units are artifact-free (defined without reference to a particular physical object which serves as a standard); the definition of one remaining unit, the kilogram is still embodied in an artifact which rests at the BIPM outside Paris. Eventually, it is hoped that new SI definitions will be uniformly artifact-free. Artifact-free definitions fix measurements at an exact value related to a physical constant or other invariable phenomenon in nature, in contrast to standard artifacts which can be damaged or otherwise change slowly over time. Instead, the measurement unit can only ever change through increased accuracy in determining the value of the constant it is tied to. The seven base units in the SI system. Arrows point from units to those that depend on them; as the accuracy of the former increase, so will the accuracy of the latter. The first proposal to tie an SI base unit to an experimental standard independent of fiat was by Charles Sanders Peirce (1839–1914),[53] who proposed to define the meter in terms of the wavelength of a spectral line.[54] This directly influenced the Michelson-Morley experiment; Michelson and Morley cite Peirce, and improve on his method.[55] SI definitions See also: New SI definitions Base quantity Base unit Symbol Current SI constants New SI constants (proposed) time second s hyperfine splitting in Cesium-133 same as current SI length meter m speed of light in vacuum, c same as current SI mass kilogram kg mass of International Prototype Kilogram (IPK) Planck's constant, h electric current ampere A permeability of free space, permittivity of free space charge of the electron, e temperature kelvin K triple point of water, absolute zero Boltzmann's constant, k amount of substance mole mol molar mass of Carbon-12 Avogadro constant NA luminous intensity candela cd luminous efficacy of a 540 THz source same as current SI [56] Mathematics and formal sciences Main article: Mathematics Data from the famous Michelson–Morley experiment Mathematics is essential to the sciences. One important function of mathematics in science is the role it plays in the expression of scientific models. Observing and collecting measurements, as well as hypothesizing and predicting, often require extensive use of mathematics. Arithmetic, algebra, geometry, trigonometry and calculus, for example, are all essential to physics. Virtually every branch of mathematics has applications in science, including "pure" areas such as number theory and topology. Statistical methods, which are mathematical techniques for summarizing and analyzing data, allow scientists to assess the level of reliability and the range of variation in experimental results. Statistical analysis plays a fundamental role in many areas of both the natural sciences and social sciences. Computational science applies computing power to simulate real-world situations, enabling a better understanding of scientific problems than formal mathematics alone can achieve. According to the Society for Industrial and Applied Mathematics, computation is now as important as theory and experiment in advancing scientific knowledge.[57] Whether mathematics itself is properly classified as science has been a matter of some debate. Some thinkers see mathematicians as scientists, regarding physical experiments as inessential or mathematical proofs as equivalent to experiments. Others do not see mathematics as a science, since it does not require an experimental test of its theories and hypotheses. Mathematical theorems and formulas are obtained by logical derivations which presume axiomatic systems, rather than the combination of empirical observation and logical reasoning that has come to be known as scientific method. In general, mathematics is classified as formal science, while natural and social sciences are classified as empirical sciences.[58] Scientific method Main article: Scientific method A scientific method seeks to explain the events of nature in a reproducible way.[59] An explanatory thought experiment or hypothesis is put forward, as explanation, from which stem predictions. The predictions are to be posted before a confirming experiment or observation is sought, as proof that no tampering has occurred. Disproof of a prediction is evidence of progress.[60][61] This is done partly through observation of natural phenomena, but also through experimentation, that tries to simulate natural events under controlled conditions, as appropriate to the discipline (in the observational sciences, such as astronomy or geology, a predicted observation might take the place of a controlled experiment). Taken in its entirety, a scientific method allows for highly creative problem solving while minimizing any effects of subjective bias on the part of its users (namely the confirmation bias).[62] In the nineteenth century, the measurement of Earth's gravity was primarily dependent on pendulums for gravimetric surveys. An improved pendulum, designed by Friedrich Bessel, was manufactured by Repsold and Sons, Hamburg, Germany. The American C.S. Peirce was tasked with gravimetric research by the U.S. Coast and Geodetic Survey. Peirce developed a theory of the systematic errors in the mount of the Repsold pendulum. He was asked to present his theory for improving pendulums to a Special Committee of the International Geodetic Association. While underway to a conference of the IGA in Europe, September 1877, Peirce wrote an essay in French on scientific method, "How to Make Our Ideas Clear"[63] and translated "The Fixation of Belief"[64] into French.[65] In these essays, he notes that our beliefs clash with real life, causing what Peirce denotes as the "irritation of doubt", for which he then lists multiple methods of coping, among them, scientific method.[66] "Model-making, the imaginative and logical steps which precede the experiment, may be judged the most important part of scientific method because skill and insight in these matters are rare. Without them we do not know what experiment to do. But it is the experiment which provides the raw material for scientific theory. Scientific theory cannot be built directly from the conclusions of conceptual models." —Herbert George Andrewartha (1907-92), Australian zoologist and entomologist, Introduction to the study of animal population 1961, 181[67]
scientists, see Natural science. For other uses, see Science (disambiguation). Montage of some highly influential scientists from a variety of scientific fields. From left to right: Top row - Archimedes, Aristotle, Ibn al-Haytham, Leonardo da Vinci, Galileo Galilei, Antonie van Leeuwenhoek; Second row - Isaac Newton, James Hutton, Antoine Lavoisier, John Dalton, Charles Darwin, Gregor Mendel; Third row - Louis Pasteur, James Clerk Maxwell, Henri Poincaré, Sigmund Freud, Nikola Tesla, Max Planck; Fourth row - Ernest Rutherford, Marie Curie, Albert Einstein, Niels Bohr, Erwin Schrödinger, Enrico Fermi; Bottom row - J. Robert Oppenheimer, Alan Turing, Richard Feynman, E. O. Wilson, Jane Goodall, Stephen Hawking Part of a series on Science Formal sciences[show] Physical sciences[show] Life sciences[show] Social and behavioural sciences[show] Applied sciences[show] Interdisciplinarity[show] Philosophy and history of science[show] Science portal Category v t e Science (from Latin scientia, meaning "knowledge") is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe.[1] In an older and closely related meaning (found, for example, in Aristotle), "science" refers to the body of reliable knowledge itself, of the type that can be logically and rationally explained (see History and philosophy below).[2] Since classical antiquity science as a type of knowledge was closely linked to philosophy. In the early modern era the words "science" and "philosophy" were sometimes used interchangeably in the English language. By the 17th century, natural philosophy (which is today called "natural science") was considered a separate branch of philosophy.[3] However, "science" continued to be used in a broad sense denoting reliable knowledge about a topic, in the same way it is still used in modern terms such as library science or political science. In modern use, "science" more often refers to a way of pursuing knowledge, not only the knowledge itself. It is "often treated as synonymous with 'natural and physical science', and thus restricted to those branches of study that relate to the phenomena of the material universe and their laws, sometimes with implied exclusion of pure mathematics. This is now the dominant sense in ordinary use."[4] This narrower sense of "science" developed as scientists such as Johannes Kepler, Galileo Galilei and Isaac Newton began formulating laws of nature such as Newton's laws of motion. In this period it became more common to refer to natural philosophy as "natural science". Over the course of the 19th century, the word "science" became increasingly associated with scientific method, a disciplined way to study the natural world, including physics, chemistry, geology and biology. It is in the 19th century also that the term scientist was created by the naturalist-theologian William Whewell to distinguish those who sought knowledge on nature from those who sought knowledge on other disciplines. The Oxford English Dictionary dates the origin of the word "scientist" to 1834. This sometimes left the study of human thought and society in a linguistic limbo, which was resolved by classifying these areas of academic study as social science. Similarly, several other major areas of disciplined study and knowledge exist today under the general rubric of "science", such as formal science and applied science. Contents [show] History and philosophy History Main article: History of science Both Aristotle and Kuan Tzu (4th C. BCE), in an example of simultaneous scientific discovery, mention that some marine animals were subject to a lunar cycle, and increase and decrease in size with the waxing and waning of the moon. Aristotle was referring specifically to the sea urchin, pictured above.[5] Science in a broad sense existed before the modern era, and in many historical civilizations, but modern science is so distinct in its approach and successful in its results that it now defines what science is in the strictest sense of the term. Much earlier than the modern era, another important turning point was the development of the classical natural philosophy in the ancient Greek-speaking world. Pre-philosophical Science in its original sense is a word for a type of knowledge (Latin scientia, Ancient Greek epistemē), rather than a specialized word for the pursuit of such knowledge. In particular it is one of the types of knowledge which people can communicate to each other and share. For example, knowledge about the working of natural things was gathered long before recorded history and led to the development of complex abstract thinking, as shown by the construction of complex calendars, techniques for making poisonous plants edible, and buildings such as the pyramids. However no consistent distinction was made between knowledge of such things which are true in every community, and other types of communal knowledge such as mythologies and legal systems. Philosophical study of nature See also: Nature (philosophy) Before the invention or discovery of the concept of "nature" (Ancient Greek phusis), by the Pre-Socratic philosophers, the same words tend to be used to describe the natural "way" in which a plant grows,[6] and the "way" in which, for example, one tribe worships a particular god. For this reason it is claimed these men were the first philosophers in the strict sense, and also the first people to clearly distinguish "nature" and "convention".[7] Science was therefore distinguished as the knowledge of nature, and the things which are true for every community, and the name of the specialized pursuit of such knowledge was philosophy — the realm of the first philosopher-physicists. They were mainly speculators or theorists, particularly interested in astronomy. In contrast, trying to use knowledge of nature to imitate nature (artifice or technology, Greek technē) was seen by classical scientists as a more appropriate interest for lower class artisans.[8] Philosophical turn to human things A major turning point in the history of early philosophical science was the controversial but successful attempt by Socrates to apply philosophy to the study of human things, including human nature, the nature of political communities, and human knowledge itself. He criticized the older type of study of physics as too purely speculative, and lacking in self-criticism. He was particularly concerned that some of the early physicists treated nature as if it could be assumed that it had no intelligent order, explaining things merely in terms of motion and matter. The study of human things had been the realm of mythology and tradition, and Socrates was executed. Aristotle later created a less controversial systematic programme of Socratic philosophy, which was teleological, and human-centred. He rejected many of the conclusions of earlier scientists. For example in his physics the sun goes around the earth, and many things have it as part of their nature that they are for humans. Each thing has a formal cause and final cause and a role in the rational cosmic order. Motion and change is described as the actualization of potentials already in things, according to what types of things they are. While the Socratics insisted that philosophy should be used to consider the practical question of the best way to live for a human being, they did not argue for any other types of applied science. Aristotle maintained the sharp distinction between science and the practical knowledge of artisans, treating theoretical speculation as the highest type of human activity, practical thinking about good living as something less lofty, and the knowledge of artisans as something only suitable for the lower classes. In contrast to modern science, Aristotle's influential emphasis was upon the "theoretical" steps of deducing universal rules from raw data, and did not treat the gathering of experience and raw data as part of science itself.[9] Medieval science During late antiquity and the early Middle Ages, the Aristotelian approach to inquiries on natural phenomenon was used. Some ancient knowledge was lost, or in some cases kept in obscurity, during the fall of the Roman Empire and periodic political struggles. However, the general fields of science, or Natural Philosophy as it was called, and much of the general knowledge from the ancient world remained preserved though the works of the early encyclopedists like Isidore of Seville. During the early medieval period, Syrian Christians from Eastern Europe such as Nestorians and Monophysites were the ones that translated much of the important Greek science texts from Greek to Syriac and the later on they translated many of the works into Arabic and other languages under Islamic rule.[10] This was a major line of transmission for the development of Islamic science which provided much of the activity during the early medieval period. In the later medieval period, Europeans recovered some ancient knowledge by translations of texts and they built their work upon the knowledge of Aristotle, Ptolemy, Euclid, and others works. In Europe, men like Roger Bacon learned Arabic and Hebrew and argued for more experimental science. By the late Middle Ages, a synthesis of Catholicism and Aristotelianism known as Scholasticism was flourishing in Western Europe, which had become a new geographic center of science. Renaissance, and early modern science Main article: Scientific revolution Galileo is considered one of the fathers of modern science.[11] By the late Middle Ages, especially in Italy there was an influx of texts and scholars from the collapsing Byzantine empire. Copernicus formulated a heliocentric model of the solar system unlike the geocentric model of Ptolemy's Almagest. All aspects of scholasticism were criticized in the 15th and 16th centuries; one author who was notoriously persecuted was Galileo, who made innovative use of experiment and mathematics. However the persecution began after Pope Urban VIII blessed Galileo to write about the Copernican system. Galileo had used arguments from the Pope and put them in the voice of the simpleton in the work "Dialogue Concerning the Two Chief World Systems" which caused great offense to him.[12] In Northern Europe, the new technology of the printing press was widely used to publish many arguments including some that disagreed with church dogma. René Descartes and Francis Bacon published philosophical arguments in favor of a new type of non-Aristotelian science. Descartes argued that mathematics could be used in order to study nature, as Galileo had done, and Bacon emphasized the importance of experiment over contemplation. Bacon also argued that science should aim for the first time at practical inventions for the improvement of all human life. Bacon questioned the Aristotelian concepts of formal cause and final cause, and promoted the idea that science should study the laws of "simple" natures, such as heat, rather than assuming that there is any specific nature, or "formal cause", of each complex type of thing. This new modern science began to see itself as describing "laws of nature". This updated approach to studies in nature was seen as mechanistic. Age of Enlightenment In the 17th and 18th centuries, the project of modernity, as had been promoted by Bacon and Descartes, led to rapid scientific advance and the successful development of a new type of natural science, mathematical, methodically experimental, and deliberately innovative. Newton and Leibniz succeeded in developing a new physics, now referred to as Newtonian physics, which could be confirmed by experiment and explained in mathematics. Leibniz also incorporated terms from Aristotelian physics, but now being used in a new non-teleological way, for example "energy" and "potential". But in the style of Bacon, he assumed that different types of things all work according to the same general laws of nature, with no special formal or final causes for each type of thing. It is, during this period that the word science gradually became more commonly used to refer to the pursuit of a type of knowledge, and especially knowledge of nature — coming close in meaning to the old term "natural philosophy". 19th century Distinguished Men of Science.[13] Use a cursor to see who is who.[14] Both John Herschel and William Whewell systematised methodology: the latter coined the term scientist. When Charles Darwin published On the Origin of Species he established descent with modification as the prevailing evolutionary explanation of biological complexity. His theory of natural selection provided a natural explanation of how species originated, but this only gained wide acceptance a century later. John Dalton developed the idea of atoms. The laws of Thermodynamics and the electromagnetic theory were also established in the 19th century, which raised new questions which could not easily be answered using Newton's framework. 20th century Einstein's Theory of Relativity and the development of quantum mechanics led to the replacement of Newtonian physics with a new physics which contains two parts, that describe different types of events in nature. The extensive use of scientific innovation during the wars of this century, led to the space race and widespread public appreciation of the importance of modern science. Philosophy of science Main article: Philosophy of science Further information: Intersubjective verifiability and Subjunctive possibility Working scientists usually take for granted a set of basic assumptions that are needed to justify a scientific method: (1) that there is an objective reality shared by all rational observers; (2) that this objective reality is governed by natural laws; (3) that these laws can be discovered by means of systematic observation and experimentation. Philosophy of science seeks a deep understanding of what these underlying assumptions mean and whether they are valid. Most contributions to the philosophy of science have come from philosophers, who frequently view the beliefs of most scientists as superficial or naive—thus there is often a degree of antagonism between working scientists and philosophers of science. John Locke The belief that all observers share a common reality is known as realism. It can be contrasted with anti-realism, the belief that there is no valid concept of absolute truth such that things that are true for one observer are true for all observers. The most commonly defended form of anti-realism is idealism, the belief that the mind or spirit is the most basic essence, and that each mind generates its own reality.[15] In an idealistic world-view, what is true for one mind need not be true for other minds. There are different schools of thought in philosophy of science. The most popular position is empiricism, which claims that knowledge is created by a process involving observation and that scientific theories are the result of generalizations from such observations.[16] Empiricism generally encompasses inductivism, a position that tries to explain the way general theories can be justified by the finite number of observations humans can make and the hence finite amount of empirical evidence available to confirm scientific theories. This is necessary because the number of predictions those theories make is infinite, which means that they cannot be known from the finite amount of evidence using deductive logic only. Many versions of empiricism exist, with the predominant ones being bayesianism[17] and the hypothetico-deductive method.[18] Empiricism has stood in contrast to rationalism, the position originally associated with Descartes, which holds that knowledge is created by the human intellect, not by observation.[19] A significant twentieth century version of rationalism is critical rationalism, first defined by Austrian-British philosopher Karl Popper. Popper rejected the way that empiricism describes the connection between theory and observation. He claimed that theories are not generated by observation, but that observation is made in the light of theories and that the only way a theory can be affected by observation is when it comes in conflict with it.[20] Popper proposed falsifiability as the landmark of scientific theories, and falsification as the empirical method, to replace verifiability[21] and induction by purely deductive notions.[22] Popper further claimed that there is actually only one universal method, and that this method is not specific to science: The negative method of criticism, trial and error.[23] It covers all products of the human mind, including science, mathematics, philosophy, and art [24] Another approach, instrumentalism, colloquially termed "shut up and calculate", emphasizes the utility of theories as instruments for explaining and predicting phenomena.[25] It claims that scientific theories are black boxes with only their input (initial conditions) and output (predictions) being relevant. Consequences, notions and logical structure of the theories are claimed to be something that should simply be ignored and that scientists shouldn't make a fuss about (see interpretations of quantum mechanics). Finally, another approach often cited in debates of scientific skepticism against controversial movements like "scientific creationism", is methodological naturalism. Its main point is that a difference between natural and supernatural explanations should be made, and that science should be restricted methodologically to natural explanations.[26] That the restriction is merely methodological (rather than ontological) means that science should not consider supernatural explanations itself, but should not claim them to be wrong either. Instead, supernatural explanations should be left a matter of personal belief outside the scope of science. Methodological naturalism maintains that proper science requires strict adherence to empirical study and independent verification as a process for properly developing and evaluating explanations for observable phenomena.[27] The absence of these standards, arguments from authority, biased observational studies and other common fallacies are frequently cited by supporters of methodological naturalism as criteria for the dubious claims they criticize not to be true science. Basic and applied research Although some scientific research is applied research into specific problems, a great deal of our understanding comes from the curiosity-driven undertaking of basic research. This leads to options for technological advance that were not planned or sometimes even imaginable. This point was made by Michael Faraday when, allegedly in response to the question "what is the use of basic research?" he responded "Sir, what is the use of a new-born child?".[28] For example, research into the effects of red light on the human eye's rod cells did not seem to have any practical purpose; eventually, the discovery that our night vision is not troubled by red light would lead search and rescue teams (among others) to adopt red light in the cockpits of jets and helicopters.[29] In a nutshell: Basic research is the search for knowledge. Applied research is the search for solutions to practical problems using this knowledge. Finally, even basic research can take unexpected turns, and there is some sense in which the scientific method is built to harness luck. Experimentation and hypothesizing DNA determines the genetic structure of all known life Based on observations of a phenomenon, scientists may generate a model. This is an attempt to describe or depict the phenomenon in terms of a logical, physical or mathematical representation. As empirical evidence is gathered, scientists can suggest a hypothesis to explain the phenomenon.[30] Hypotheses may be formulated using principles such as parsimony (also known as "Occam's Razor") and are generally expected to seek consilience—fitting well with other accepted facts related to the phenomena.[31] This new explanation is used to make falsifiable predictions that are testable by experiment or observation. When a hypothesis proves unsatisfactory, it is either modified or discarded.[32] Experimentation is especially important in science to help establish causational relationships (to avoid the correlation fallacy). Operationalization also plays an important role in coordinating research in/across different fields. Once a hypothesis has survived testing, it may become adopted into the framework of a scientific theory. This is a logically reasoned, self-consistent model or framework for describing the behavior of certain natural phenomena. A theory typically describes the behavior of much broader sets of phenomena than a hypothesis; commonly, a large number of hypotheses can be logically bound together by a single theory. Thus a theory is a hypothesis explaining various other hypotheses. In that vein, theories are formulated according to most of the same scientific principles as hypotheses. While performing experiments, scientists may have a preference for one outcome over another, and so it is important to ensure that science as a whole can eliminate this bias.[33][34] This can be achieved by careful experimental design, transparency, and a thorough peer review process of the experimental results as well as any conclusions.[35][36] After the results of an experiment are announced or published, it is normal practice for independent researchers to double-check how the research was performed, and to follow up by performing similar experiments to determine how dependable the results might be.[37] Certainty and science A scientific theory is empirical, and is always open to falsification if new evidence is presented. That is, no theory is ever considered strictly certain as science accepts the concept of fallibilism. The philosopher of science Karl Popper sharply distinguishes truth from certainty. He writes that scientific knowledge "consists in the search for truth", but it "is not the search for certainty ... All human knowledge is fallible and therefore uncertain."[38] Although science values legitimate doubt, The Flat Earth Society is still widely regarded as an example of taking skepticism too far New scientific knowledge very rarely results in vast changes in our understanding. According to psychologist Keith Stanovich, it may be the media's overuse of words like "breakthrough" that leads the public to imagine that science is constantly proving everything it thought was true to be false.[39] While there are such famous cases as the theory of relativity that required a complete reconceptualization, these are extreme exceptions. Knowledge in science is gained by a gradual synthesis of information from different experiments, by various researchers, across different domains of science; it is more like a climb than a leap.[40] Theories vary in the extent to which they have been tested and verified, as well as their acceptance in the scientific community.[41] For example, heliocentric theory, the theory of evolution, and germ theory still bear the name "theory" even though, in practice, they are considered factual.[42] Philosopher Barry Stroud adds that, although the best definition for "knowledge" is contested, being skeptical and entertaining the possibility that one is incorrect is compatible with being correct. Ironically then, the scientist adhering to proper scientific method will doubt themselves even once they possess the truth.[43] The fallibilist C. S. Peirce argued that inquiry is the struggle to resolve actual doubt and that merely quarrelsome, verbal, or hyperbolic doubt is fruitless[44]—but also that the inquirer should try to attain genuine doubt rather than resting uncritically on common sense.[45] He held that the successful sciences trust, not to any single chain of inference (no stronger than its weakest link), but to the cable of multiple and various arguments intimately connected.[46] Stanovich also asserts that science avoids searching for a "magic bullet"; it avoids the single-cause fallacy. This means a scientist would not ask merely "What is the cause of...", but rather "What are the most significant causes of...". This is especially the case in the more macroscopic fields of science (e.g. psychology, cosmology).[47] Of course, research often analyzes few factors at once, but these are always added to the long list of factors that are most important to consider.[47] For example: knowing the details of only a person's genetics, or their history and upbringing, or the current situation may not explain a behaviour, but a deep understanding of all these variables combined can be very predictive. Scientific practice Astronomy became much more accurate after Tycho Brahe devised his scientific instruments for measuring angles between two celestial bodies, before the invention of the telescope. Brahe's observations were the basis for Kepler's laws. "If a man will begin with certainties, he shall end in doubts; but if he will be content to begin with doubts, he shall end in certainties." —Francis Bacon (1605) The Advancement of Learning, Book 1, v, 8 A skeptical point of view, demanding a method of proof, was the practical position taken as early as 1000 years ago, with Alhazen, Doubts Concerning Ptolemy, through Bacon (1605), and C. S. Peirce (1839–1914), who note that a community will then spring up to address these points of uncertainty. The methods of inquiry into a problem have been known for thousands of years,[48] and extend beyond theory to practice. The use of measurements, for example, are a practical approach to settle disputes in the community. John Ziman points out that intersubjective pattern recognition is fundamental to the creation of all scientific knowledge.[49] Ziman shows how scientists can identify patterns to each other across centuries: Needham 1954 (illustration facing page 164) shows how today's trained Western botanist can identify Artemisia alba from images taken from a 16th c. Chinese pharmacopia,[50] and Ziman refers to this ability as 'perceptual consensibility'.[51] Ziman then makes consensibility, leading to consensus, the touchstone of reliable knowledge.[52] Measurement Main article: Measurement Measurement is often used in science to make definitive comparisons and reduce confusion. Even in cases of clear qualitative difference, increased precision through measurement is often preferred in order to aid in replication. For example, different colors may be reported based on wavelengths of light, instead of vague (qualitative) terms such as "green" and "blue" which are often interpreted differently by different people. Measurements are most commonly made in the SI system, which contains seven fundamental units: kilogram, meter, candela, second, ampere, kelvin, and mole. Six of these units are artifact-free (defined without reference to a particular physical object which serves as a standard); the definition of one remaining unit, the kilogram is still embodied in an artifact which rests at the BIPM outside Paris. Eventually, it is hoped that new SI definitions will be uniformly artifact-free. Artifact-free definitions fix measurements at an exact value related to a physical constant or other invariable phenomenon in nature, in contrast to standard artifacts which can be damaged or otherwise change slowly over time. Instead, the measurement unit can only ever change through increased accuracy in determining the value of the constant it is tied to. The seven base units in the SI system. Arrows point from units to those that depend on them; as the accuracy of the former increase, so will the accuracy of the latter. The first proposal to tie an SI base unit to an experimental standard independent of fiat was by Charles Sanders Peirce (1839–1914),[53] who proposed to define the meter in terms of the wavelength of a spectral line.[54] This directly influenced the Michelson-Morley experiment; Michelson and Morley cite Peirce, and improve on his method.[55] SI definitions See also: New SI definitions Base quantity Base unit Symbol Current SI constants New SI constants (proposed) time second s hyperfine splitting in Cesium-133 same as current SI length meter m speed of light in vacuum, c same as current SI mass kilogram kg mass of International Prototype Kilogram (IPK) Planck's constant, h electric current ampere A permeability of free space, permittivity of free space charge of the electron, e temperature kelvin K triple point of water, absolute zero Boltzmann's constant, k amount of substance mole mol molar mass of Carbon-12 Avogadro constant NA luminous intensity candela cd luminous efficacy of a 540 THz source same as current SI [56] Mathematics and formal sciences Main article: Mathematics Data from the famous Michelson–Morley experiment Mathematics is essential to the sciences. One important function of mathematics in science is the role it plays in the expression of scientific models. Observing and collecting measurements, as well as hypothesizing and predicting, often require extensive use of mathematics. Arithmetic, algebra, geometry, trigonometry and calculus, for example, are all essential to physics. Virtually every branch of mathematics has applications in science, including "pure" areas such as number theory and topology. Statistical methods, which are mathematical techniques for summarizing and analyzing data, allow scientists to assess the level of reliability and the range of variation in experimental results. Statistical analysis plays a fundamental role in many areas of both the natural sciences and social sciences. Computational science applies computing power to simulate real-world situations, enabling a better understanding of scientific problems than formal mathematics alone can achieve. According to the Society for Industrial and Applied Mathematics, computation is now as important as theory and experiment in advancing scientific knowledge.[57] Whether mathematics itself is properly classified as science has been a matter of some debate. Some thinkers see mathematicians as scientists, regarding physical experiments as inessential or mathematical proofs as equivalent to experiments. Others do not see mathematics as a science, since it does not require an experimental test of its theories and hypotheses. Mathematical theorems and formulas are obtained by logical derivations which presume axiomatic systems, rather than the combination of empirical observation and logical reasoning that has come to be known as scientific method. In general, mathematics is classified as formal science, while natural and social sciences are classified as empirical sciences.[58] Scientific method Main article: Scientific method A scientific method seeks to explain the events of nature in a reproducible way.[59] An explanatory thought experiment or hypothesis is put forward, as explanation, from which stem predictions. The predictions are to be posted before a confirming experiment or observation is sought, as proof that no tampering has occurred. Disproof of a prediction is evidence of progress.[60][61] This is done partly through observation of natural phenomena, but also through experimentation, that tries to simulate natural events under controlled conditions, as appropriate to the discipline (in the observational sciences, such as astronomy or geology, a predicted observation might take the place of a controlled experiment). Taken in its entirety, a scientific method allows for highly creative problem solving while minimizing any effects of subjective bias on the part of its users (namely the confirmation bias).[62] In the nineteenth century, the measurement of Earth's gravity was primarily dependent on pendulums for gravimetric surveys. An improved pendulum, designed by Friedrich Bessel, was manufactured by Repsold and Sons, Hamburg, Germany. The American C.S. Peirce was tasked with gravimetric research by the U.S. Coast and Geodetic Survey. Peirce developed a theory of the systematic errors in the mount of the Repsold pendulum. He was asked to present his theory for improving pendulums to a Special Committee of the International Geodetic Association. While underway to a conference of the IGA in Europe, September 1877, Peirce wrote an essay in French on scientific method, "How to Make Our Ideas Clear"[63] and translated "The Fixation of Belief"[64] into French.[65] In these essays, he notes that our beliefs clash with real life, causing what Peirce denotes as the "irritation of doubt", for which he then lists multiple methods of coping, among them, scientific method.[66] "Model-making, the imaginative and logical steps which precede the experiment, may be judged the most important part of scientific method because skill and insight in these matters are rare. Without them we do not know what experiment to do. But it is the experiment which provides the raw material for scientific theory. Scientific theory cannot be built directly from the conclusions of conceptual models." —Herbert George Andrewartha (1907-92), Australian zoologist and entomologist, Introduction to the study of animal population 1961, 181[67]
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