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| History | |
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Sir Isaac Newton (1643–1727)
Albert Einstein (1879-1955)
Main article: History of physics
As noted below, the means used to understand the behavior of natural phenomena and their effects evolved from philosophy, progressively replaced by natural philosophy then natural science, to eventually arrive at the modern conception of physics.[citation needed]
Natural philosophy has its origins in Greece during the Archaic period, (650 BCE – 480 BCE), when Pre-Socratic philosophers like Thales refused supernatural, religious or mythological explanations for natural phenomena and proclaimed that every event had a natural cause.[8] They proposed ideas verified by reason and observation and many of their hypotheses proved successful in experiment,[9] for example atomism.
Natural science was developed in China, India and in Islamic caliphates, between the 4th and 10th century BCE.[citation needed] Quantitative descriptions became popular among physicists and astronomers, for example Archimedes in the domains of mechanics, statics and hydrostatics. Experimental physics had its debuts with experimentation concerning statics by medieval Muslim physicists like al-Biruni and Alhazen.[10][11]
Classical physics became a separate science when early modern Europeans used these experimental and quantitative methods to discover what are now considered to be the laws of physics.[12][13] Kepler, Galileo and more specifically Newton discovered and unified the different laws of motion.[14] During the industrial revolution, as energy needs increased, so did research, which led to the discovery of new laws in thermodynamics, chemistry and electromagnetics.
Solvay Conference of 1927, with prominent physicists such as Albert Einstein, Niels Bohr, Marie Curie, Erwin Schrödinger and Paul Dirac.
Modern physics started with the works of Einstein both in relativity and quantum physics.[citation needed]
Tags:Science,Mechanics,Chemistry,Logic,Natural Science,Energy,Natural Philosophy,Thermodynamics,Sir Isaac Newton,Albert Einstein,Philosophy,Archaic Period,Pre-socratic Philosophers,Thales,Atomism,Quantitative,Archimedes,Statics,Alhazen,Early Modern Europeans,Kepler,Galileo,Newton,Electromagnetics,Solvay Conference,Niels Bohr,Marie Curie,Erwin Schrödinger,Einstein,Relativity,Isaac Newton,Phenomena, | |
| Philosophy | |
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For more details on this topic, see Philosophy of physics.
In many ways, physics stems from ancient Greek philosophy. From Thales' first attempt to characterize matter, to Democritus' deduction that matter ought to reduce to an invariant state, the Ptolemaic astronomy of a crystalline firmament, and Aristotle's book Physics (an early book on physics, which attempted to analyze and define motion from a philosophical point of view), various Greek philosophers advanced their own theories of nature. Physics was known as natural philosophy until the late 18th century.
By the 19th century physics was realized as a discipline distinct from philosophy and the other sciences. Physics, as with the rest of science, relies on philosophy of science to give an adequate description of the scientific method.[15] The scientific method employs a priori reasoning as well as a posteriori reasoning and the use of Bayesian inference to measure the validity of a given theory.[16]
The development of physics has answered many questions of early philosophers, but has also raised new questions. Study of the philosophical issues surrounding physics, the philosophy of physics, involves issues such as the nature of space and time, determinism, and metaphysical outlooks such as empiricism, naturalism and realism.[17]
Many physicists have written about the philosophical implications of their work, for instance Laplace, who championed causal determinism,[18] and Erwin Schrödinger, who wrote on quantum mechanics.[19] The mathematical physicist Roger Penrose has been called a Platonist by Stephen Hawking,[20] a view Penrose discusses in his book, The Road to Reality.[21] Hawking refers to himself as an "unashamed reductionist" and takes issue with Penrose's views.[22]
Tags:Astronomy,Scientific Method,Philosophy Of Science,Matter,Nature,Ancient Greek Philosophy,Democritus,Ptolemaic Astronomy,Firmament,A Priori Reasoning,A Posteriori,Bayesian Inference,Space,Time,Determinism,Empiricism,Naturalism,Realism,Laplace,Causal Determinism,Quantum Mechanics,Roger Penrose,Platonist,Stephen Hawking,The Road To Reality, | |
| Core theories | |
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Further information: Branches of physics, Classical physics, Modern physics, Outline of physics
Though physics deals with a wide variety of systems, certain theories are used by all physicists. Each of these theories were experimentally tested numerous times and found correct as an approximation of nature (within a certain domain of validity). For instance, the theory of classical mechanics accurately describes the motion of objects, provided they are much larger than atoms and moving at much less than the speed of light. These theories continue to be areas of active research, and a remarkable aspect of classical mechanics known as chaos was discovered in the 20th century, three centuries after the original formulation of classical mechanics by Isaac Newton (1642–1727).
These central theories are important tools for research into more specialized topics, and any physicist, regardless of his or her specialization, is expected to be literate in them. These include classical mechanics, quantum mechanics, thermodynamics and statistical mechanics, electromagnetism, and special relativity.
Tags:Special Relativity,Electromagnetism,Atoms,Speed Of Light,Chaos,Classical Mechanics,Statistical Mechanics, | |
| Fundamental physics | |
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The basic domains of physics
While physics aims to discover universal laws, its theories lie in explicit domains of applicability. Loosely speaking, the laws of classical physics accurately describe systems whose important length scales are greater than the atomic scale and whose motions are much slower than the speed of light. Outside of this domain, observations do not match their predictions. Albert Einstein contributed the framework of special relativity, which replaced notions of absolute time and space with spacetime and allowed an accurate description of systems whose components have speeds approaching the speed of light. Max Planck, Erwin Schrödinger, and others introduced quantum mechanics, a probabilistic notion of particles and interactions that allowed an accurate description of atomic and subatomic scales. Later, quantum field theory unified quantum mechanics and special relativity. General relativity allowed for a dynamical, curved spacetime, with which highly massive systems and the large-scale structure of the universe can be well described. General relativity has not yet been unified with the other fundamental descriptions; several candidates theories of quantum gravity are being developed.
Tags:Spacetime,Universe,Absolute Time And Space,Max Planck,Quantum Field Theory,General Relativity, | |
| Relation to other fields | |
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This parabola-shaped lava flow illustrates the application of Mathematics in Physics – in this case, Galileo's law of falling bodies.
Mathematics and Ontology are used in Physics. Physics is used in Chemistry and Cosmology.
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| Prerequisites | |
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Mathematics is the language used for compact description of the order in nature, especially the laws of Physics. This was noted and advocated by Pythagoras,[23] Plato,[24] Galileo,[25] and Newton.
Physics theories use Mathematics[26] to obtain order and provide precise formulas, precise or estimated solutions, quantitative results and predictions. Experiment results in physics are numerical measurements. Technologies based on Mathematics, like computation have made computational physics an active area of research.
The distinction between Mathematics and Physics is clear-cut, but not always obvious, especially in Mathematical Physics.
Ontology is a prerequisite for Physics, but not for Mathematics. It means Physics is ultimately concerned with descriptions of the real world, while Mathematics is concerned with abstract patterns, even beyond the real world. Thus Physics statements are synthetic, while Math statements are analytic. Mathematics contains hypothesis, while Physics contains theories. Mathematics statements have to be only logically true, while predictions of Physics statements must match observed and experimental data.
The distinction is clear-cut, but not always obvious. For example, Mathematical Physics is the application of Mathematics in Physics. Its methods are Mathematical, but its subject is Physical.[27] The problems in this field start with a "Math model of a Physical situation" and a "Math description of a Physical law". Every math statement used for solution has a hard-to-find Physical meaning. The final Mathematical solution has an easier-to-find meaning, because it is what the solver is looking for.
Physics is a branch of fundamental science, not practical science.[28] Physics is also called "the fundamental science" because the subject of study of all branches of natural science like Chemistry, Astronomy, Geology and Biology are constrained by laws of physics.[29] For example, Chemistry studies properties, structures, and reactions of matter (chemistry's focus on the atomic scale distinguishes it from physics). Structures are formed because particles exert electrical forces on each other, properties include physical characteristics of given substances, and reactions are bound by laws of physics, like conservation of energy, mass and charge.
Physics is applied in industries like engineering and medicine.
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| Application and influence | |
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Archimedes' screw, a simple machine for lifting
The application of physical laws in lifting liquids
Main article: Applied physics
Applied physics is a general term for physics research which is intended for a particular use. An applied physics curriculum usually contains a few classes in an applied discipline, like geology or electrical engineering. It usually differs from engineering in that an applied physicist may not be designing something in particular, but rather is using physics or conducting physics research with the aim of developing new technologies or solving a problem.
The approach is similar to that of applied mathematics. Applied physicists can also be interested in the use of physics for scientific research. For instance, people working on accelerator physics might seek to build better particle detectors for research in theoretical physics.
Physics is used heavily in engineering. For example, Statics, a subfield of mechanics, is used in the building of bridges and other structures. The understanding and use of acoustics results in better concert halls; similarly, the use of optics creates better optical devices. An understanding of physics makes for more realistic flight simulators, video games, and movies, and is often critical in forensic investigations.
With the standard consensus that the laws of physics are universal and do not change with time, physics can be used to study things that would ordinarily be mired in uncertainty. For example, in the study of the origin of the Earth, one can reasonably model Earth's mass, temperature, and rate of rotation, over time. It also allows for simulations in engineering which drastically speed up the development of a new technology.
But there is also considerable interdisciplinarity in the physicist's methods and so many other important fields are influenced by physics, e.g. the fields of econophysics and sociophysics.
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| Scientific method | |
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Physicists use a scientific method to test the validity of a physical theory, using a methodical approach to compare the implications of the theory in question with the associated conclusions drawn from experiments and observations conducted to test it. Experiments and observations are collected and compared with the predictions and hypotheses made by a theory, thus aiding in the determination or the validity/invalidity of the theory.
Theories which are very well supported by data and have never failed any competent empirical test are often called scientific laws, or natural laws. Of course, all theories, including those called scientific laws, can always be replaced by more accurate, generalized statements if a disagreement of theory with observed data is ever found.[30]
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| Theory and experiment | |
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Main articles: Theoretical physics and Experimental physics
The astronaut and Earth are both in free-fall
Lightning is an electric current
Theorists seek to develop mathematical models that both agree with existing experiments and successfully predict future results, while experimentalists devise and perform experiments to test theoretical predictions and explore new phenomena. Although theory and experiment are developed separately, they are strongly dependent upon each other. Progress in physics frequently comes about when experimentalists make a discovery that existing theories cannot explain, or when new theories generate experimentally testable predictions, which inspire new experiments.
Physicists who work at the interplay of theory and experiment are called phenomenologists. Phenomenologists look at the complex phenomena observed in experiment and work to relate them to fundamental theory.
Theoretical physics has historically taken inspiration from philosophy; electromagnetism was unified this way.[31] Beyond the known universe, the field of theoretical physics also deals with hypothetical issues,[32] such as parallel universes, a multiverse, and higher dimensions. Theorists invoke these ideas in hopes of solving particular problems with existing theories. They then explore the consequences of these ideas and work toward making testable predictions.
Experimental physics informs, and is informed by, engineering and technology. Experimental physicists involved in basic research design and perform experiments with equipment such as particle accelerators and lasers, whereas those involved in applied research often work in industry, developing technologies such as magnetic resonance imaging (MRI) and transistors. Feynman has noted that experimentalists may seek areas which are not well explored by theorists.[33]
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| Scope and aims | |
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Physics involves modeling the natural world with theory, usually quantitative. Here, the path of a particle is modeled with the mathematics of calculus to explain its behavior: the purview of the branch of physics known as mechanics.
Physics covers a wide range of phenomena, from elementary particles (such as quarks, neutrinos and electrons) to the largest superclusters of galaxies. Included in these phenomena are the most basic objects composing all other things. Therefore physics is sometimes called the "fundamental science".[29] Physics aims to describe the various phenomena that occur in nature in terms of simpler phenomena. Thus, physics aims to both connect the things observable to humans to root causes, and then connect these causes together.
For example, the ancient Chinese observed that certain rocks (lodestone) were attracted to one another by some invisible force. This effect was later called magnetism, and was first rigorously studied in the 17th century. A little earlier than the Chinese, the ancient Greeks knew of other objects such as amber, that when rubbed with fur would cause a similar invisible attraction between the two. This was also first studied rigorously in the 17th century, and came to be called electricity. Thus, physics had come to understand two observations of nature in terms of some root cause (electricity and magnetism). However, further work in the 19th century revealed that these two forces were just two different aspects of one force – electromagnetism. This process of "unifying" forces continues today, and electromagnetism and the weak nuclear force are now considered to be two aspects of the electroweak interaction. Physics hopes to find an ultimate reason (Theory of Everything) for why nature is as it is (see section Current research below for more information).
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Contemporary research in physics can be broadly divided into condensed matter physics; atomic, molecular, and optical physics; particle physics; astrophysics; geophysics and biophysics. Some physics departments also support research in Physics education.
Since the twentieth century, the individual fields of physics have become increasingly specialized, and today most physicists work in a single field for their entire careers. "Universalists" such as Albert Einstein (1879–1955) and Lev Landau (1908–1968), who worked in multiple fields of physics, are now very rare.[34]
Table of the major fields of physics, along with their subfields and the theories they employ
Field
Subfields
Major theories
Concepts
Astrophysics
Astronomy, Astrometry, Cosmology, Gravitation physics, High-energy astrophysics, Planetary astrophysics, Plasma physics, Solar Physics, Space physics, Stellar astrophysics
Big Bang, Cosmic inflation, General relativity, Newton's law of universal gravitation, Lambda-CDM model, Magnetohydrodynamics
Black hole, Cosmic background radiation, Cosmic string, Cosmos, Dark energy, Dark matter, Galaxy, Gravity, Gravitational radiation, Gravitational singularity, Planet, Solar system, Star, Supernova, Universe
Atomic, molecular, and optical physics
Atomic physics, Molecular physics, Atomic and Molecular astrophysics, Chemical physics, O Tags: | |
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