# Theoretical physics

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Higgs boson The Higgs boson is named after Peter Higgs, one of six physicists who, in 1964, proposed the mechanism that suggested the existence of such a particle. Although Higgs's name has come to be associated with this theory, several researchers between about 1960 and 1972 each independently developed different parts of it. In mainstream media the Higgs boson has often been called the "God particle", from a 1993 book on the topic; the nickname is strongly disliked by many physicists, including Higgs, who regard it as inappropriate sensationalism.[17][18] In 2013 two of the original researchers, Peter Higgs and François Englert, were awarded the Nobel Prize in Physics for their work and prediction[19] (Englert's co-researcher Robert Brout had died in 2011). A non-technical summary "Higgs" terminology Overview If this field did exist, this would be a monumental discovery for science and human knowledge, and is expected to open doorways to new knowledge in many fields. History

Units of measurement For example, length is a physical quantity. The metre is a unit of length that represents a definite predetermined length. When we say 10 metres (or 10 m), we actually mean 10 times the definite predetermined length called "metre". The definition, agreement, and practical use of units of measurement have played a crucial role in human endeavour from early ages up to this day. In trade, weights and measures is often a subject of governmental regulation, to ensure fairness and transparency. In physics and metrology, units are standards for measurement of physical quantities that need clear definitions to be useful. Science, medicine, and engineering often use larger and smaller units of measurement than those used in everyday life and indicate them more precisely. In the social sciences, there are no standard units of measurement and the theory and practice of measurement is studied in psychometrics and the theory of conjoint measurement. History Systems of units Guidelines

Standard Model The Standard Model of particle physics is a theory concerning the electromagnetic, weak, and strong nuclear interactions, as well as classifying all the subatomic particles known. It was developed throughout the latter half of the 20th century, as a collaborative effort of scientists around the world.[1] The current formulation was finalized in the mid-1970s upon experimental confirmation of the existence of quarks. Since then, discoveries of the top quark (1995), the tau neutrino (2000), and more recently the Higgs boson (2013), have given further credence to the Standard Model. Because of its success in explaining a wide variety of experimental results, the Standard Model is sometimes regarded as a "theory of almost everything". Historical background The Higgs mechanism is believed to give rise to the masses of all the elementary particles in the Standard Model. Overview Particle content Fermions Gauge bosons Higgs boson Main article: Higgs boson E.S.

Experiment Even very young children perform rudimentary experiments in order to learn about the world. An experiment is an orderly procedure carried out with the goal of verifying, refuting, or establishing the validity of a hypothesis. Controlled experiments provide insight into cause-and-effect by demonstrating what outcome occurs when a particular factor is manipulated. Controlled experiments vary greatly in their goal and scale, but always rely on repeatable procedure and logical analysis of the results. A child may carry out basic experiments to understand the nature of gravity, while teams of scientists may take years of systematic investigation to advance the understanding of a phenomenon. Overview In the scientific method, an experiment is an empirical method that arbitrates between competing models or hypotheses.[1][2] Experimentation is also used to test existing theories or new hypotheses in order to support them or disprove them.[3][4] History G. Types of experiment

Complex analysis Murray R. Spiegel described complex analysis as "one of the most beautiful as well as useful branches of Mathematics". Complex analysis is particularly concerned with the analytic functions of complex variables (or, more generally, meromorphic functions). Because the separate real and imaginary parts of any analytic function must satisfy Laplace's equation, complex analysis is widely applicable to two-dimensional problems in physics. History Complex analysis is one of the classical branches in mathematics with roots in the 19th century and just prior. Complex functions For any complex function, both the independent variable and the dependent variable may be separated into real and imaginary parts: and where are real-valued functions. In other words, the components of the function f(z), can be interpreted as real-valued functions of the two real variables, x and y. Holomorphic functions See also: analytic function, holomorphic sheaf and vector bundles. Major results

State of matter Historically, the distinction is made based on qualitative differences in properties. Matter in the solid state maintains a fixed volume and shape, with component particles (atoms, molecules or ions) close together and fixed into place. Matter in the liquid state maintains a fixed volume, but has a variable shape that adapts to fit its container. The four fundamental states Solid A crystalline solid: atomic resolution image of strontium titanate. In a solid the particles (ions, atoms or molecules) are closely packed together. In crystalline solids, the particles (atoms, molecules, or ions) are packed in a regularly ordered, repeating pattern. Liquid Structure of a classical monatomic liquid. A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. Gas The spaces between gas molecules are very big. A gas is a compressible fluid. Plasma Like a gas, plasma does not have definite shape or volume. Glass

Physics Various examples of physical phenomena Physics is one of the oldest academic disciplines, perhaps the oldest through its inclusion of astronomy.[8] Over the last two millennia, physics was a part of natural philosophy along with chemistry, certain branches of mathematics, and biology, but during the Scientific Revolution in the 17th century, the natural sciences emerged as unique research programs in their own right.[b] Physics intersects with many interdisciplinary areas of research, such as biophysics and quantum chemistry, and the boundaries of physics are not rigidly defined. New ideas in physics often explain the fundamental mechanisms of other sciences[6] while opening new avenues of research in areas such as mathematics and philosophy. Physics also makes significant contributions through advances in new technologies that arise from theoretical breakthroughs. History Ancient astronomy Astronomy is the oldest of the natural sciences. Natural philosophy Classical physics Modern physics

Physical quantity A physical quantity (or "physical magnitude") is a physical property of a phenomenon, body, or substance, that can be quantified by measurement.[1] Extensive and intensive quantities An extensive quantity is equal to the sum of that quantity for all of its constituent subsystems; examples include volume, mass, and electric charge. For instance, if an object has mass m1 and another has mass m2 then a system simply comprising those two objects will have a mass of m1 + m2. An intensive quantity is independent of the extent of the system; quantities such as temperature, pressure, and density are examples. There are also physical quantities that can be classified as neither extensive nor intensive, for example an extensive quantity with a nonlinear operator applied, such as the square of volume.[2] Symbols, nomenclature General: Symbols for quantities should be chosen according to the international recommendations from ISO/IEC 80000, the IUPAP red book and the IUPAC green book. Units

Newton's laws of motion First law: When viewed in an inertial reference frame, an object either remains at rest or continues to move at a constant velocity, unless acted upon by an external force.[2][3]Second law: F = ma. The vector sum of the forces F on an object is equal to the mass m of that object multiplied by the acceleration vector a of the object.Third law: When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body. The three laws of motion were first compiled by Isaac Newton in his Philosophiæ Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy), first published in 1687.[4] Newton used them to explain and investigate the motion of many physical objects and systems.[5] For example, in the third volume of the text, Newton showed that these laws of motion, combined with his law of universal gravitation, explained Kepler's laws of planetary motion. Overview Newton's first law Impulse

Observation Observation is the active acquisition of information from a primary source. In living beings, observation employs the senses. In science, observation can also involve the recording of data via the use of instruments. Observation in science The scientific method requires observations of nature to formulate and test hypotheses.[1] It consists of these steps:[2][3] Asking a question about a natural phenomenonMaking observations of the phenomenonHypothesizing an explanation for the phenomenonPredicting a logical consequence of the hypothesisTesting the hypothesis by an experiment, an observational study, or a field studyCreating a conclusion with data gathered in the experiment, or forming a revised/new hypothesis and repeating the process Senses are limited, and are subject to errors in perception such as optical illusions. Observational paradoxes Biases Several of the more important ways observations can be affected by human psychology are given below. Confirmation bias

Newton's law of universal gravitation Newton's law of universal gravitation states that any two bodies in the universe attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. (Separately it was shown that large spherically symmetrical masses attract and are attracted as if all their mass were concentrated at their centers.) This is a general physical law derived from empirical observations by what Isaac Newton called induction.[2] It is a part of classical mechanics and was formulated in Newton's work Philosophiæ Naturalis Principia Mathematica ("the Principia"), first published on 5 July 1687. (When Newton's book was presented in 1686 to the Royal Society, Robert Hooke made a claim that Newton had obtained the inverse square law from him – see History section below.) History Early History Plagiarism dispute In this way arose the question as to what, if anything, Newton owed to Hooke. Vector form

Physical system Complexity in physical systems The complexity of a physical system is equal to the probability of it being in a particular state vector. If one considers a classical Newtonian ball situation with a number of perfectly moving physical bodies bouncing off the walls of a container, the system-state probability does not change over time. In a physical system, a lower probability state vector is equivalent to a higher complexity. In mathematical systems, one can consider the complexity of particular states more easily. See also References Jump up ^ An Essay on the Investigation of the First Principles of Nature. External links

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