The scale of the universe mapped to the branches of science and the hierarchy of science.[1]

Science (from Latin scientia, meaning "knowledge")[2][3]:58 is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe.[a]

Contemporary science is typically subdivided into the natural sciences which study nature in the broadest sense, the social sciences which study people and societies, and the formal sciences like mathematics which study abstract concepts. Some do not consider formal sciences to be true science as theories within these disciplines cannot be tested with physical observations,[4]:54although others dispute this view.[5] Either way, mathematics is a crucial tool for modern science and nowadays all science students need to take at least some basic mathematics courses during their studies. Disciplines which use science like engineering and medicine may also be considered to be applied sciences.[6] Science is related to research, and is normally organized by a university, a college, or a research institute.

From classical antiquity through the 19th century, science as a type of knowledge was more closely linked to philosophy than it is now and, in fact, in the West the term "natural philosophy" encompassed fields of study that are today associated with science such as physics, astronomy, medicine, among many others.[7]:3[b] In the 17th and 18th centuries scientists increasingly sought to formulate knowledge in terms of laws of nature. As a slow process over centuries, the word "science" became increasingly associated with what is today known as the scientific method, a structured way to study the natural world.[8][9]

Science in a broad sense existed before the modern era and in many historical civilizations.[c] [10] Modern science is distinct in its approachand successful in its results, so it now defines what science is in the strictest sense of the term.[11]

Science in its original sense was a word for a type of knowledge rather than a specialized word for the pursuit of such knowledge. In particular, it was the type 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 thought. This is shown by the construction of complex calendars, techniques for making poisonous plants edible, public works at national scale, such which those which harnessed the floodplain of the Yangtse with reservoirs,[12] dams, and dikes, and buildings such as the Pyramids. However, no consistent conscientious 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.

Maize, known in some English-speaking countries as corn, is a large grainplant domesticated by indigenous peoplesin Mesoamerica in prehistoric times.

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,[13] 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."[14]:209 Science was therefore distinguished as the knowledge of nature and 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.[15]

The early Greek philosophers of the Milesian school, which was founded by Thales of Miletusand later continued by his successors Anaximander and Anaximenes, were the first to attempt to explain natural phenomena without relying on the supernatural.[16] The Pythagoreans developed a complex number philosophy[17]:467–468 and contributed significantly to the development of mathematical science.[17]:465 The theory of atoms was developed by the Greek philosopher Leucippus and his student Democritus.[18][19] The Greek doctor Hippocrates established the tradition of systematic medical science[20][21] and is known as "The Father of Medicine".[22]

Aristotle, 384–322 BCE, one of the early figures in the development of the scientific method[23].

A turning point in the history of early philosophical science was Socrates' example of applying philosophy to the study of human things, including human nature, the nature of political communities, and human knowledge itself. The Socratic method as documented by Plato's dialogues is a dialectic method of hypothesis elimination: better hypotheses are found by steadily identifying and eliminating those that lead to contradictions. This was a reaction to the Sophist emphasis on rhetoric. The Socratic method searches for general, commonly held truths that shape beliefs and scrutinizes them to determine their consistency with other beliefs.[24] Socrates criticized the older type of study of physics as too purely speculative and lacking in self-criticism. Socrates was later, in the words of his Apology, accused "because he corrupts the youth and does not believe in the gods the state believes in, but in other new spiritual beings". Socrates refuted these claims,[25] but was sentenced to death.[26]: 30e

Aristotle later created a systematic programme of teleological philosophy: Motion and change is described as the actualization of potentials already in things, according to what types of things they are. 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, a final cause, and a role in a cosmic order with an unmoved mover. While the Socratics insisted that philosophy should be used to consider the practical question of the best way to live for a human being (a study Aristotle divided into ethics and political philosophy), they did not argue for any other types of applied science. Aristotle maintained that man knows a thing scientifically "when he possesses a conviction arrived at in a certain way, and when the first principles on which that conviction rests are known to him with certainty".[27]

The Greek astronomer Aristarchus of Samos (310–230 BCE) was the first to propose the heliocentric model of the universe, with the sun in the center and all the planets orbiting it.[28] Aristarchus's model was widely rejected because it was believed to violate the laws of physics,[28] but the inventor and mathematician Archimedes of Syracuse defended it in.[28] Archimedes himself made major contributions to the beginnings of calculus[29] and has sometimes been credited as its inventor,[29] although his proto-calculus lacked several defining features.[29] Pliny the Elder was a Roman writer and polymath, who wrote the seminal encyclopedia Natural History,[30][31][32] dealing with history, geography, medicine, astronomy, earth science, botany, and zoology.[30] Other scientists or proto-scientists in Antiquity were Theophrastus, Euclid, Herophilos, Hipparchus, Ptolemy, and Galen.

During late antiquity, in the Byzantine empire many Greek classical texts were preserved. Many Syriac translations were done by groups such as the Nestorians and Monophysites.[33] They played a role when they translated Greek classical texts into Arabic under the Caliphate, during which many types of classical learning were preserved and in some cases improved upon.[33][d] In addition, the neighboring Sassanid Empire established the medical Academy of Gondeshapur where Greek, Syriac and Persian physicians established the most important medical center of the ancient world during the 6th and 7th centuries.[34]

De potentiis anime sensitive, Gregor Reisch (1504) Margarita philosophica. Medieval science postulated a ventricle of the brain as the location for our common sense,[35]where the forms from our sensory systems commingled.

Because of the collapse of the Western Roman Empire due to the Migration Period a decline in intellectual level found place in the western part of Europe in the 400s. In contrast, the Byzantine Empire resisted the attacks from the barbarians, and preserved and improved the learning. John Philoponus, a byzantine scholar in the 500s, was the first scholar ever to question Aristotle's teaching of physics and noting its flaws. John Philoponus' criticism of Aristotelian principles of physics served as an inspiration for Galileo Galilei ten centuries later as Galileo cited Philoponus substantially in his works when Galileo also argued why Aristotelian physics was flawed during the Scientific Revolution.[36][37]

During late antiquity and the early Middle Ages, the Aristotelian approach to inquiries on natural phenomena was used. Aristotle's four causes prescribed that four "why" questions should be answered in order to explain things scientifically.[38] Some ancient knowledge was lost, or in some cases kept in obscurity, during the fall of the Western 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 through the works of the early Latin encyclopedists like Isidore of Seville. However, Aristotle's original texts were eventually lost in Western Europe, and only one text by Plato was widely known, the Timaeus, which was the only Platonic dialogue, and one of the few original works of classical natural philosophy, available to Latin readers in the early Middle Ages. Another original work that gained influence in this period was Ptolemy's Almagest, which contains a geocentric description of the solar system.

In the Byzantine empire, many Greek classical texts were preserved. Many Syriac translations were done by groups such as the Nestorians and Monophysites.[33] They played a role when they translated Greek classical texts into Arabic under the Caliphate, during which many types of classical learning were preserved and in some cases improved upon.[33][e]

The House of Wisdom was established in Abbasid-era Baghdad, Iraq,[39] where the Islamic study of Aristotelianism flourished. Al-Kindi(801–873) was the first of the Muslim Peripatetic philosophers, and is known for his efforts to introduce Greek and Hellenistic philosophy to the Arab world.[40] The Islamic Golden Age flourished form this time until the Mongol invasions of the 13th century. Ibn al-Haytham(Alhazen), as well as his predecessor Ibn Sahl, was familiar with Ptolemy's Optics, and used experiments as a means to gain knowledge.[f][41][42]:463–65 Furthermore, doctors and alchemists such as the Persians Avicenna and Al-Razi also greatly developed the science of Medicine with the former writing the Canon of Medicine, a medical encyclopedia used until the 18th century[43] and the latter discovering multiple compounds like alcohol.[44] Avicenna's canon is considered to be one of the most important publications in medicine and they both contributed significantly to the practice of experimental medicine, using clinical trials and experiments to back their claims.[45][46]

In the Classical antiquity Greek and Roman taboos had meant that dissection was usually banned in ancient times, but in Middle Ages it changed: medical teachers and students at Bologna began to open human bodies, and Mondino de Luzzi (ca. 1275–1326) produced the first known anatomy textbook based on human dissection.[47][48]

By the eleventh century most of Europe had become Christian; stronger monarchies emerged; borders were restored; technological developments and agricultural innovations were made which increased the food supply and population. In addition, classical Greek texts started to be translated from Arabic and Greek into Latin, giving a higher level of scientific discussion in Western Europe.[49]

By 1088, the first university in Europe (the University of Bologna) had emerged from its clerical beginnings. Demand for Latin translations grew (for example, from the Toledo School of Translators); western Europeans began collecting texts written not only in Latin, but also Latin translations from Greek, Arabic, and Hebrew. Manuscript copies of Alhazen's Book of Optics also propagated across Europe before 1240,[50]:Intro. p. xx as evidenced by its incorporation into Vitello's Perspectiva. Avicenna's Canon was translated into Latin.[51] In particular, the texts of Aristotle, Ptolemy,[g] and Euclid, preserved in the Houses of Wisdom and also in the Byzantine Empire,[52] were sought amongst Catholic scholars. The influx of ancient texts caused the Renaissance of the 12th century and the flourishing of a synthesis of Catholicismand Aristotelianism known as Scholasticism in western Europe, which became a new geographic center of science. An experiment in this period would be understood as a careful process of observing, describing, and classifying.[53] One prominent scientist in this era was Roger Bacon. Scholasticism had a strong focus on revelation and dialectic reasoning, and gradually fell out of favour over the next centuries.

Galen (129–c. 216) noted the optic chiasm is X-shaped. (Engraving from Vesalius, 1543)

Alhazen disproved Ptolemy's theory of vision,[54] but did not make any corresponding changes to Aristotle's metaphysics. The scientific revolution ran concurrently to a process where elements of Aristotle's metaphysics such as ethics, teleology and formal causality slowly fell out of favour. Scholars slowly came to realize that the universe itself might well be devoid of both purpose and ethical imperatives. Many of the restrictions described by Aristotle and later favoured by the Catholic Church were thus challenged. This development from a physics infused with goals, ethics, and spirit, toward a physics where these elements do not play an integral role, took centuries.

Albrecht Durer (1525) Man drawing a lute, using Perspectivist techniques, as well as Alhazen's technique of taut strings to visualize a light ray.

New developments in optics played a role in the inception of the Renaissance, both by challenging long-held metaphysical ideas on perception, as well as by contributing to the improvement and development of technology such as the camera obscura and the telescope. Before what we now know as the Renaissance started, Roger Bacon, Vitello, and John Peckham each built up a scholastic ontology upon a causal chain beginning with sensation, perception, and finally apperception of the individual and universal forms of Aristotle.[55]A model of vision later known as perspectivism was exploited and studied by the artists of the Renaissance. This theory utilizes only three of Aristotle's four causes: formal, material, and final.[56]

Galileo Galilei, regarded as the father of modern science.[57]: Vol. 24, No. 1, p. 36

In the sixteenth century, Copernicus formulated a heliocentricmodel of the solar system unlike the geocentric model of Ptolemy's Almagest. This was based on a theorem that the orbital periods of the planets are longer as their orbs are farther from the centre of motion, which he found not to agree with Ptolemy's model.[58]

Kepler and others challenged the notion that the only function of the eye is perception, and shifted the main focus in optics from the eye to the propagation of light.[59][60]:102 Kepler modelled the eye as a water-filled glass sphere with an aperture in front of it to model the entrance pupil. He found that all the light from a single point of the scene was imaged at a single point at the back of the glass sphere. The optical chain ends on the retina at the back of the eye.[h] Kepler is best known, however, for improving Copernicus' heliocentric model through the discovery of Kepler's laws of planetary motion. Kepler did not reject Aristotelian metaphysics, and described his work as a search for the Harmony of the Spheres.

Galileo made innovative use of experiment and mathematics. However, he became persecuted 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 greatly offended him.[61]

In Northern Europe, the new technology of the printing press was widely used to publish many arguments, including some that disagreed widely with contemporary ideas of nature. René Descartes and Francis Bacon published philosophical arguments in favor of a new type of non-Aristotelian science. Descartes emphasized individual thought and argued that mathematics rather than geometry should be used in order to study nature. Bacon emphasized the importance of experiment over contemplation. Bacon further 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. Bacon also argued that science should aim for the first time at practical inventions for the improvement of all human life.

Isaac Newton, shown here in a 1689 portrait, made seminal contributions to classical mechanics, gravity, and optics. Newton shares credit with Gottfried Leibniz for the development of calculus.

As a precursor to the Age of Enlightenment, Isaac Newton and Gottfried Wilhelm Leibnizsucceeded in developing a new physics, now referred to as classical mechanics, which could be confirmed by experiment and explained using mathematics. Leibniz also incorporated terms from Aristotelian physics, but now being used in a new non-teleological way, for example, "energy" and "potential" (modern versions of Aristotelian "energeia and potentia"). This implied a shift in the view of objects: Where Aristotle had noted that objects have certain innate goals that can be actualized, objects were now regarded as devoid of innate goals. In the style of Francis Bacon, Leibniz 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 a type of pursuit of a type of knowledge, especially knowledge of nature – coming close in meaning to the old term "natural philosophy."

Science during the Enlightenment was dominated by scientific societies and academies, which had largely replaced universities as centres of scientific research and development. Societies and academies were also the backbone of the maturation of the scientific profession. Another important development was the popularization of science among an increasingly literate population. Philosophes introduced the public to many scientific theories, most notably through the Encyclopédie and the popularization of Newtonianism by Voltaire as well as by Émilie du Châtelet, the French translator of Newton's Principia.

Some historians have marked the 18th century as a drab period in the history of science;[62]however, the century saw significant advancements in the practice of medicine, mathematics, and physics; the development of biological taxonomy; a new understanding of magnetism and electricity; and the maturation of chemistry as a discipline, which established the foundations of modern chemistry.

Enlightenment philosophers chose a short history of scientific predecessors – Galileo, Boyle, and Newton principally – as the guides and guarantors of their applications of the singular concept of nature and natural law to every physical and social field of the day. In this respect, the lessons of history and the social structures built upon it could be discarded.[63]

Early in the 19th century, John Dalton suggested the modern atomic theory, based on Democritus's original idea of individible particles called atoms.

Charles Darwin in 1854, by then working towards publication of On the Origin of Species.

Both John Herschel and William Whewell systematized methodology: the latter coined the term scientist.[64] When Charles Darwin published On the Origin of Species he established evolution as the prevailing 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.

The laws of conservation of energy, conservation of momentum and conservation of mass suggested a highly stable universe where there could be little loss of resources. With the advent of the steam engine and the industrial revolution, there was, however, an increased understanding that all forms of energy as defined by Newton were not equally useful; they did not have the same energy quality. This realization led to the development of the laws of thermodynamics, in which the cumulative energy quality of the universe is seen as constantly declining: the entropy of the universe increases over time.

The electromagnetic theory was also established in the 19th century, and raised new questions which could not easily be answered using Newton's framework. The phenomena that would allow the deconstruction of the atom were discovered in the last decade of the 19th century: the discovery of X-raysinspired the discovery of radioactivity. In the next year came the discovery of the first subatomic particle, the electron.

Combustion and chemical reactions were studied by Michael Faraday and reported in his lectures before the Royal Institution: The Chemical History of a Candle, 1861.

A simulated event in the CMS detector of the Large Hadron Collider, featuring a possible appearance of the Higgs boson.

Einstein's theory of relativity and the development of quantum mechanics led to the replacement of classical mechanics with a new physics which contains two parts that describe different types of events in nature.

In the first half of the century, the development of antibiotics and artificial fertilizer made global human population growth possible. At the same time, the structure of the atom and its nucleus was discovered, leading to the release of "atomic energy" (nuclear power). In addition, the extensive use of technological innovation stimulated by the wars of this century led to revolutions in transportation (automobiles and aircraft), the development of ICBMs, a space race, and a nuclear arms race.

The molecular structure of DNA was discovered in 1953. The discovery of the cosmic microwave background radiation in 1964 led to a rejection of the Steady State theory of the universe in favour of the Big bang theory of Georges Lemaître.

The development of spaceflight in the second half of the century allowed the first astronomical measurements done on or near other objects in space, including manned landings on the Moon. Space telescopes lead to numerous discoveries in astronomy and cosmology.

Widespread use of integrated circuits in the last quarter of the 20th century combined with communications satellites led to a revolution in information technology and the rise of the global internet and mobile computing, including smartphones. The need for mass systematization of long, intertwined causal chains and large amounts of data led to the rise of the fields of systems theory and computer-assisted scientific modelling, which are partly based on the Aristotelian paradigm.[65]

Harmful environmental issues such as ozone depletion, acidification, eutrophication and climate change came to the public's attention in the same period, and caused the onset of environmental science and environmental technology. In a 1967 article, Lynn Townsend White Jr.blamed the ecological crisis on the historical decline of the notion of spirit in nature.[66]

With the discovery of the Higgs boson in 2012, the last particle predicted by the Standard Model of particle physics was found. In 2015, gravitational waves, predicted by general relativity a century before, were first observed.[67][68]

The Human Genome Project was completed in 2003, determining the sequence of nucleotide base pairs that make up human DNA, and identifying and mapping all of the genes of the human genome. [69] Induced pluripotent stem cells were developed in 2006, a technology allowing adult cells to be transformed into stem cells capable of giving rise to any cell type found in the body, potentially of huge importance to the field of regenerative medicine.[70]

The scientific method seeks to objectively explain the events of nature in a reproducible way.[i] An explanatory thought experiment or hypothesis is put forward as explanation 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.[3] This new explanation is used to make falsifiablepredictions that are testable by experiment or observation. 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.[j][k] 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). Experimentation is especially important in science to help establish causal relationships (to avoid the correlation fallacy).

When a hypothesis proves unsatisfactory, it is either modified or discarded.[71] If the hypothesis survived testing, it may become adopted into the framework of a scientific theory, 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. In addition to testing hypotheses, scientists may also generate a model, an attempt to describe or depict the phenomenon in terms of a logical, physical or mathematical representation and to generate new hypotheses that can be tested, based on observable phenomena.[72]

While performing experiments to test hypotheses, 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.[73][74] This can be achieved by careful experimental design, transparency, and a thorough peer review process of the experimental results as well as any conclusions.[75][76] 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.[77] Taken in its entirety, the scientific method allows for highly creative problem solving while minimizing any effects of subjective bias on the part of its users (especially the confirmation bias).[78]

Calculus, the mathematics of continuous change, underpins many of the sciences.

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. For example, arithmetic, algebra, geometry, trigonometry, and calculus are all essential to physics. Virtually every branch of mathematics has applications in science, including "pure" areas such as number theoryand 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.[79]

Other formal sciences include information theory, systems theory, decision theory and theoretical linguistics. Such sciences involve the study of well defined abstract systems and depend heavily on mathematics. They do not involve empirical procedures, their results are derived logically from their definitions and are analytic in nature.[80]

Parts of the natural and social sciences which are based on empirical results but which depend heavily on mathematical development include mathematical finance, mathematical physics, mathematical chemistry, mathematical biology and mathematical economics.

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 because 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 the scientific method. In general, mathematics is classified as formal science, while natural and social sciences are classified as empirical sciences.[81]

The scientific community is the group of all interacting scientists. It includes many sub-communities working on particular scientific fields, and within particular institutions; interdisciplinary and cross-institutional activities are also significant.

The somatosensory system is located throughout our bodies but is integrated in the brain.

Scientific fields are commonly divided into two major groups: natural sciences, which study natural phenomena (including biological life), and social sciences, which study human behavior and societies. These are both empirical sciences, which means their knowledge must be based on observable phenomena and capable of being tested for its validity by other researchers working under the same conditions.[82] There are also related disciplines that are grouped into interdisciplinary applied sciences, such as engineering and medicine. Within these categories are specialized scientific fields that can include parts of other scientific disciplines but often possess their own nomenclature and expertise.[83]

Mathematics, which is classified as a formal science,[84][85] has both similarities and differences with the empirical sciences (the natural and social sciences). It is similar to empirical sciences in that it involves an objective, careful and systematic study of an area of knowledge; it is different because of its method of verifying its knowledge, using a priori rather than empirical methods.[86] The formal sciences, which also include statistics and logic, are vital to the empirical sciences. Major advances in formal science have often led to major advances in the empirical sciences. The formal sciences are essential in the formation of hypotheses, theories, and laws,[87] both in discovering and describing how things work (natural sciences) and how people think and act (social sciences).

Apart from its broad meaning, the word "science" sometimes may specifically refer to fundamental sciences (maths and natural sciences) alone. Science schools or faculties within many institutions are separate from those for medicine or engineering, each of which is an applied science.

Learned societies for the communication and promotion of scientific thought and experimentation have existed since the Renaissanceperiod.[88] The oldest surviving institution is the Italian Accademia dei Lincei which was established in 1603.[89] The respective National Academies of Science are distinguished institutions that exist in a number of countries, beginning with the British Royal Society in 1660[90]and the French Académie des Sciences in 1666.[91]

International scientific organizations, such as the International Council for Science, have since been formed to promote cooperation between the scientific communities of different nations. Many governments have dedicated agencies to support scientific research. Prominent scientific organizations include the National Science Foundation in the U.S., the National Scientific and Technical Research Council in Argentina, CSIRO in Australia, Centre national de la recherche scientifique in France, the Max Planck Society and Deutsche Forschungsgemeinschaft in Germany, and CSIC in Spain.

An enormous range of scientific literature is published.[92] Scientific journals communicate and document the results of research carried out in universities and various other research institutions, serving as an archival record of science. The first scientific journals, Journal des Sçavans followed by the Philosophical Transactions, began publication in 1665. Since that time the total number of active periodicals has steadily increased. In 1981, one estimate for the number of scientific and technical journals in publication was 11,500.[93] The United States National Library of Medicine currently indexes 5,516 journals that contain articles on topics related to the life sciences. Although the journals are in 39 languages, 91 percent of the indexed articles are published in English.[94]

Most scientific journals cover a single scientific field and publish the research within that field; the research is normally expressed in the form of a scientific paper. Science has become so pervasive in modern societies that it is generally considered necessary to communicate the achievements, news, and ambitions of scientists to a wider populace.

Science magazines such as New Scientist, Science & Vie, and Scientific American cater to the needs of a much wider readership and provide a non-technical summary of popular areas of research, including notable discoveries and advances in certain fields of research. Science books engage the interest of many more people. Tangentially, the science fiction genre, primarily fantastic in nature, engages the public imagination and transmits the ideas, if not the methods, of science.

Recent efforts to intensify or develop links between science and non-scientific disciplines such as literature or more specifically, poetry, include the Creative Writing Science resource developed through the Royal Literary Fund.[95]

Marie Curie was the first person to be awarded two Nobel Prizes: Physicsin 1903 and Chemistry in 1911[96].

Science has historically been a male-dominated field, with some notable exceptions.[l] Women faced considerable discrimination in science, much as they did in other areas of male-dominated societies, such as frequently being passed over for job opportunities and denied credit for their work.[m] For example, Christine Ladd (1847–1930) was able to enter a PhD program as "C. Ladd"; Christine "Kitty" Ladd completed the requirements in 1882, but was awarded her degree only in 1926, after a career which spanned the algebra of logic (see truth table), color vision, and psychology. Her work preceded notable researchers like Ludwig Wittgenstein and Charles Sanders Peirce. The achievements of women in science have been attributed to their defiance of their traditional role as laborers within the domestic sphere.[97]

In the late 20th century, active recruitment of women and elimination of institutional discrimination on the basis of sex greatly increased the number of women scientists, but large gender disparities remain in some fields; over half of new biologists are female, while 80% of PhDs in physics are given to men.[citation needed] Feminists claim this is the result of culture rather than an innate difference between the sexes, and some experiments have shown that parents challenge and explain more to boys than girls, asking them to reflect more deeply and logically.[98]: 258–61. In the early part of the 21st century, in America, women earned 50.3% bachelor's degrees, 45.6% master's degrees, and 40.7% of PhDs in science and engineering fields with women earning more than half of the degrees in three fields: Psychology (about 70%), Social Sciences (about 50%), and Biology (about 50-60%). However, when it comes to the Physical Sciences, Geosciences, Math, Engineering, and Computer Science, women earned less than half the degrees.[99]However, lifestyle choice also plays a major role in female engagement in science; women with young children are 28% less likely to take tenure-track positions due to work-life balance issues,[100] and female graduate students' interest in careers in research declines dramatically over the course of graduate school, whereas that of their male colleagues remains unchanged.[101]

President Clinton meets the 1998 U.S. Nobel Prize winners in the White House.

Science policy is an area of public policy concerned with the policies that affect the conduct of the scientific enterprise, including research funding, often in pursuance of other national policy goals such as technological innovation to promote commercial product development, weapons development, health care and environmental monitoring. Science policy also refers to the act of applying scientific knowledge and consensus to the development of public policies. Science policy thus deals with the entire domain of issues that involve the natural sciences. In accordance with public policy being concerned about the well-being of its citizens, science policy's goal is to consider how science and technology can best serve the public.

State policy has influenced the funding of public works (such as the civil engineering works in hydraulic engineering of Sunshu Ao (孫叔敖 7th c. BCE), Ximen Bao (西門豹 5th c.BCE), and Shi Chi (4th c. BCE) ) and science for thousands of years. These works date at least from the time of the Mohists, who inspired the study of logic during the period of the Hundred Schools of Thought, and the study of defensive fortifications (such as the Great Wall of China, which took 2000 years to complete) during the Warring States period in China. In Great Britain, governmental approval of the Royal Society in the 17th century recognized a scientific community which exists to this day. The professionalization of science, begun in the 19th century, was partly enabled by the creation of scientific organizations such as the National Academy of Sciences, the Kaiser Wilhelm Institute, and state funding of universities of their respective nations. Public policy can directly affect the funding of capital equipment and intellectual infrastructure for industrial research by providing tax incentives to those organizations that fund research. Vannevar Bush, director of the Office of Scientific Research and Development for the United States government, the forerunner of the National Science Foundation, wrote in July 1945 that "Science is a proper concern of government."[102]

Science and technology research is often funded through a competitive process in which potential research projects are evaluated and only the most promising receive funding. Such processes, which are run by government, corporations, or foundations, allocate scarce funds. Total research funding in most developed countries is between 1.5% and 3% of GDP.[103] In the OECD, around two-thirds of research and development in scientific and technical fields is carried out by industry, and 20% and 10% respectively by universities and government. The government funding proportion in certain industries is higher, and it dominates research in social science and humanities. Similarly, with some exceptions (e.g. biotechnology) government provides the bulk of the funds for basic scientific research. In commercial research and development, all but the most research-oriented corporations focus more heavily on near-term commercialisation possibilities rather than "blue-sky" ideas or technologies (such as nuclear fusion).

The mass media face a number of pressures that can prevent them from accurately depicting competing scientific claims in terms of their credibility within the scientific community as a whole. Determining how much weight to give different sides in a scientific debate may require considerable expertise regarding the matter.[105] Few journalists have real scientific knowledge, and even beat reporters who know a great deal about certain scientific issues may be ignorant about other scientific issues that they are suddenly asked to cover.[106][107]

Many issues damage the relationship of science to the media and the use of science and scientific arguments by politicians. As a very broad generalisation, many politicians seek certainties and facts whilst scientists typically offer probabilities and caveats. However, politicians' ability to be heard in the mass media frequently distorts the scientific understanding by the public. Examples in the United Kingdom include the controversy over the MMR inoculation, and the 1988 forced resignation of a Government Minister, Edwina Currie, for revealing the high probability that battery farmed eggs were contaminated with Salmonella.[108]

John Horgan, Chris Mooney, and researchers from the US and Canada have described Scientific Certainty Argumentation Methods (SCAMs), where an organization or think tank makes it their only goal to cast doubt on supported science because it conflicts with political agendas.[109][110][111] Hank Campbell and microbiologist Alex Berezow have described "feel-good fallacies" used in politics, especially on the left, where politicians frame their positions in a way that makes people feel good about supporting certain policies even when scientific evidence shows there is no need to worry or there is no need for dramatic change on current programs.[112]: Vol. 78, No. 1. 2–38

Various activities are developed to facilitate communication between the general public and science/scientists, such as science outreach, public awareness of science, science communication, science festivals, citizen science, science journalism, public science, and popular science. See Science and the public for related concepts.

Science is represented by the 'S' in STEM fields.

Working scientists usually take for granted a set of basic assumptions that are needed to justify the 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.[11] Philosophy of science seeks a deep understanding of what these underlying assumptions mean and whether they are valid.

The belief that scientific theories should and do represent metaphysical reality is known as realism. It can be contrasted with anti-realism, the view that the success of science does not depend on it being accurate about unobservable entities such as electrons. One form of anti-realism is idealism, the belief that the mind or consciousness is the most basic essence, and that each mind generates its own reality.[n] In an idealistic world view, what is true for one mind need not be true for other minds.

The Sand Reckoner is a work by Archimedes in which he sets out to determine an upper bound for the number of grains of sand that fit into the universe. In order to do this, he had to estimate the size of the universe according to the contemporary model, and invent a way to analyze extremely large numbers.

There are different schools of thought in philosophy of science. The most popular position is empiricism,[o] which holds that knowledge is created by a process involving observation and that scientific theories are the result of generalizations from such observations.[113] 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 hence the 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[114] and the hypothetico-deductive method.[115]:236

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.[115]:20 Critical rationalism is a contrasting 20th-century approach to science, 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.[115]:63–67 Popper proposed replacing verifiability with falsifiability as the landmark of scientific theories and replacing induction with falsification as the empirical method.[115]:68 Popper further claimed that there is actually only one universal method, not specific to science: the negative method of criticism, trial and error.[116] It covers all products of the human mind, including science, mathematics, philosophy, and art.[117]

Another approach, instrumentalism, colloquially termed "shut up and multiply,"[118] emphasizes the utility of theories as instruments for explaining and predicting phenomena.[119] It views scientific theories as black boxes with only their input (initial conditions) and output (predictions) being relevant. Consequences, theoretical entities, and logical structure are claimed to be something that should simply be ignored and that scientists shouldn't make a fuss about (see interpretations of quantum mechanics). Close to instrumentalism is constructive empiricism, according to which the main criterion for the success of a scientific theory is whether what it says about observable entities is true.

Paul Feyerabend advanced the idea of epistemological anarchism, which holds that there are no useful and exception-free methodological rules governing the progress of science or the growth of knowledge and that the idea that science can or should operate according to universal and fixed rules are unrealistic, pernicious and detrimental to science itself.[120] Feyerabend advocates treating science as an ideology alongside others such as religion, magic, and mythology, and considers the dominance of science in society authoritarian and unjustified. He also contended (along with Imre Lakatos)[discuss] that the demarcation problem of distinguishing science from pseudoscienceon objective grounds is not possible and thus fatal to the notion of science running according to fixed, universal rules.[120] Feyerabend also stated that science does not have evidence for its philosophical precepts, particularly the notion of uniformity of law and process across time and space.[121]

Finally, another approach often cited in debates of scientific skepticism against controversial movements like "creation science" 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.[p] 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.[122] The absence of these standards, arguments from authority, biased observational studies and other common fallacies are frequently cited by supporters of methodological naturalism as characteristic of the non-science they criticize.

The DNA double helix is a molecule that encodes the genetic instructions used in the development and functioning of all known living organisms and many viruses.

A scientific theory is empirical[o][123] 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.[q] The philosopher of science Karl Popper sharply distinguished truth from certainty. He wrote 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."[124]:4

New scientific knowledge 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.[125]:119–38 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 branches of science; it is more like a climb than a leap.[125]:123 Theories vary in the extent to which they have been tested and verified, as well as their acceptance in the scientific community.[r] For example, heliocentric theory, the theory of evolution, relativity theory, and germ theory still bear the name "theory" even though, in practice, they are considered factual.[126] 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 approaches will doubt themselves even once they possess the truth.[127] 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[128] – but also that the inquirer should try to attain genuine doubt rather than resting uncritically on common sense.[129] 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.[130]

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, physical cosmology).[125]:141–47 Research often analyzes few factors at once, but these are always added to the long list of factors that are most important to consider.[125]:141–47 For example, knowing the details of only a person's genetics, or their history and upbringing, or the current situation may not explain a behavior, but a deep understanding of all these variables combined can be very predictive.

An area of study or speculation that masquerades as science in an attempt to claim a legitimacy that it would not otherwise be able to achieve is sometimes referred to as pseudoscience, fringe science, or junk science.[s] Physicist Richard Feynman coined the term "cargo cult science" for cases in which researchers believe they are doing science because their activities have the outward appearance of science but actually lack the "kind of utter honesty" that allows their results to be rigorously evaluated.[131] Various types of commercial advertising, ranging from hype to fraud, may fall into these categories.

There can also be an element of political or ideological bias on all sides of scientific debates. Sometimes, research may be characterized as "bad science," research that may be well-intended but is actually incorrect, obsolete, incomplete, or over-simplified expositions of scientific ideas. The term "scientific misconduct" refers to situations such as where researchers have intentionally misrepresented their published data or have purposely given credit for a discovery to the wrong person.[132]

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.

Although encyclopedias such as Pliny's (fl. 77 AD) Natural History offered purported fact, they proved unreliable. A skeptical point of view, demanding a method of proof, was the practical position taken to deal with unreliable knowledge. As early as 1000 years ago, scholars such as Alhazen (Doubts Concerning Ptolemy), Roger Bacon, Witelo, John Pecham, Francis Bacon (1605), and C. S. Peirce (1839–1914) provided the community to address these points of uncertainty. In particular, fallacious reasoning can be exposed, such as "affirming the consequent."

"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, "The Advancement of Learning", Book 1, v, 8

The methods of inquiry into a problem have been known for thousands of years,[133] and extend beyond theory to practice. The use of measurements, for example, is 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.[134]:44 Ziman shows how scientists can identify patterns to each other across centuries; he refers to this ability as "perceptual consensibility."[135]:46 He then makes consensibility, leading to consensus, the touchstone of reliable knowledge.[135]:104

Anthropogenic pollution has an effect on the Earth's environment and climate.

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?".[136] 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.[125]:106–10 In a nutshell, basic research is the search for knowledge and 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.

Due to the increasing complexity of information and specialization of scientists, most of the cutting-edge research today is done by well-funded groups of scientists, rather than individuals.[137] D.K. Simonton notes that due to the breadth of very precise and far reaching tools already used by researchers today and the amount of research generated so far, creation of new disciplines or revolutions within a discipline may no longer be possible as it is unlikely that some phenomenon that merits its own discipline has been overlooked. Hybridizing of disciplines and finessing knowledge is, in his view, the future of science.[137]

Discoveries in fundamental science can be world-changing. For example:

• "GCSE Science textbook". Wikibooks.org

• Euroscience:
  • "ESOF: Euroscience Open Forum". Archived from the original on June 10, 2010.
• Science Development in the Latin American docta
• Classification of the Sciences in Dictionary of the History of Ideas. (Dictionary's new electronic format is badly botched, entries after "Design" are inaccessible. Internet Archive old version).
• "Nature of Science" University of California Museum of Paleontology
• United States Science Initiative Selected science information provided by US Government agencies, including research & development results
• How science works University of California Museum of Paleontology

• Science
• Knowledge