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Contemporary science is typically subdivided into the natural sciences which study the material world, the social sciences which study people and societies, and the formal sciences like mathematics. Some do not consider formal sciences to be true science as theories within these disciplines cannot be tested with physical observations,:54 although others dispute this view. Disciplines which use science like engineering and medicine may also be considered to be applied sciences. 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.: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.
In modern science, it is regarded as good scientific practice to aim for principles such as objectivity and reproducibility, which means that improvised methodology or bizarre interpretations should be downplayed, at least unless the scientist rightfully suspects a paradigm change. It is seen as advantageous to not deviate too far from the scientific method, which nonetheless is far more stringently applied in e.g. the medical sciences than in sociology. The optimal way to conduct modern science is under constant debate in the philosophy of science. The English term "science" often refers to a particularly formal kind of empiricalresearch, whereas equivalent concepts in other languages may not distinguish as clearly between this and rationalist academic research. The acceptance of the influence of continental philosophy in modern science may differ between countries and between individual universities. Advances in modern science are sometimes used to develop new technology, but also examine limits to technological development.
Main article: History of science
Science in a broad sense existed before the modern era and in many historical civilizations.[c]Modern science is distinct in its approach and successful in its results, so it now defines what science is in the strictest sense of the term.
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, 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.
Main article: History of science in classical antiquity
See also: Nature (philosophy)
Before the invention or discovery of the concept of "nature" (ancient Greekphusis) by the Pre-Socratic philosophers, the same words tend to be used to describe the natural "way" in which a plant grows, 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.":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.
The early Greek philosophers of the Milesian school, which was founded by Thales of Miletus and later continued by his successors Anaximander and Anaximenes, were the first to attempt to explain natural phenomena without relying on the supernatural. The Pythagoreans developed a complex number philosophy:467–468 and contributed significantly to the development of mathematical science.:465 The theory of atoms was developed by the Greek philosopher Leucippus and his student Democritus. The Greek doctor Hippocrates established the tradition of systematic medical science and is known as "The Father of Medicine".
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. 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, but was sentenced to death.: 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".
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. Aristarchus's model was widely rejected because it was believed to violate the laws of physics, but the inventor and mathematician Archimedes of Syracuse defended it in. Archimedes himself made major contributions to the beginnings of calculus and has sometimes been credited as its inventor, although his proto-calculus lacked several defining features.Pliny the Elder was a Roman writer and polymath, who wrote the seminal encyclopedia Natural History, dealing with history, geography, medicine, astronomy, earth science, botany, and zoology. Other scientists or proto-scientists in Antiquity were Theophrastus, Euclid, Herophilos, Hipparchus, Ptolemy, and Galen.
Further information: Science in the medieval Islamic world
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. 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 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 science texts were preserved in Syriac translations done by groups such as the Nestorians and Monophysites. Many of these were later on translated into Arabic under the Caliphate, during which many types of classical learning were preserved and in some cases improved upon.[d]
The House of Wisdom was established in Abbasid-era Baghdad, Iraq, 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. 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.[e]:463–65
In the later medieval period, the first universities started emerging in Europe, and 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,:Intro. p. xx as evidenced by its incorporation into Vitello's Perspectiva. In particular, the texts of Aristotle, Ptolemy,[f] and Euclid, preserved in the Houses of Wisdom, were sought amongst Catholic scholars. The influx of ancient texts caused the Renaissance of the 12th century and the flourishing of a synthesis of Catholicism and 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. 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.
Renaissance and early modern science
Main article: Scientific revolution
Alhazen disproved Ptolemy's theory of vision, 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.
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. 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.
In the sixteenth century, Copernicus formulated a heliocentric model 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.
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.: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.[g] 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.
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.
Age of Enlightenment
As a precursor to the Age of Enlightenment, Isaac Newton and Gottfried Wilhelm Leibniz succeeded 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; 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.
Early in the 19th century, John Dalton suggested the modern atomic theory, based on Democritus's original idea of individible particles called atoms.
Both John Herschel and William Whewell systematized methodology: the latter coined the term scientist. 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-rays inspired the discovery of radioactivity. In the next year came the discovery of the first subatomic particle, the electron.
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.
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.
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.
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. 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.
Main article: Scientific method
The scientific method seeks to objectively explain the events of nature in a reproducible way.[h] 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. This new explanation is used to make falsifiable predictions 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.[i][j] 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. 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.
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. This can be achieved by careful experimental design, transparency, and a thorough peer review process of the experimental results as well as any conclusions. 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. 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).
Mathematics and formal sciences
Main articles: Mathematics and Formal science
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