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With time for uninterrupted concentration, he works out the binomial theorem, differential and integral calculus, the relationship between light and colour and the concept of gravity. The student is the year-old Isaac Newton. The famous detail of the falling apple in the garden of Woolsthorpe Manor, as the moment of truth in relation to gravity, provides the perfect seed for a popular legend. But the story is first told in the next century, by Voltaire , who claims to have had it from Newton's step-niece.

In reality it is the moon which prompts Newton's researches into gravity. Meanwhile his discoveries in relation to light and colour bring him his first fame. Returning to Cambridge in , and discussing there his new discoveries, Newton wins an immediate reputation. In , when still short of his twenty-seventh birthday, he is elected the Lucasian professor of mathematics. His lectures and researches are mainly at this stage to do with optics.

He invents for his purposes a new and more powerful form of telescope using mirrors the reflecting telescope, which becomes the principle of all the most powerful instruments until the introduction of radio astronomy. In he presents a telescope of this kind to the Royal Society and is elected a member. Later in this same year he describes for the Society his experiments with the prism. In this famous piece of research Newton directs a shaft of sunlight through a prism. He finds that it spreads out and splits into separate colours covering the full range of the spectrum.

If he directs these coloured rays through a reverse prism, the light emerging is once again white. However if he isolates any single colour, by sending it to the second prism through a narrow slot, it will emerge as that same colour, unchanged. It has often previously been observed that light passing through a medium such as a bowl of water can change colour, but it has been assumed that this colour is imparted by the glass or water. Newton's reversible experiment proves that the phenomenon is an aspect of light itself. Different wavelengths of light have different angles of refraction, with the result that the prism separates them.

White light, containing all the wave lengths, can be transformed back and forth. Light of a single wave length and colour can only remain itself. It follows from this that the perceived colour of different substances derives from the particular wavelengths of light which they reflect to the eye; or, in Newton's words, that 'natural bodies are variously qualified to reflect one sort of light in greater plenty than another'.

The sciences of colour and of spectrum analysis begin with this work, which Newton eventually publishes in as Opticks.

In Edmund Halley visits Newton in Cambridge. Hearing his ideas on the motion of celestial bodies, he urges him to develop them as a book.

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When lack of funds in the Royal Society seems likely to delay the project, Halley pays the entire cost of printing himself. The book, one of the most influential in the history of science, derives from the young Newton's speculations about the moon during his time at Woolsthorpe Manor two decades earlier. The question which stimulated his thoughts was this: what prevents the moon from flying out of its orbit round the earth, just as a ball being whirled on a string will fly away if the string breaks? The ball, in such an event, flies off at a tangent. Newton reasons that the moon can be seen as perpetually falling from such a tangent into its continuing orbit round the earth.

He calculates mathematically by how much, on such an analogy, the moon is falling every second. He then uses these figures to calculate, on the same principle, the probable speed of a body falling in the usual way in our own surroundings. He finds that theory and reality match, in his own words, 'pretty nearly'.

The word gravity is already in use at this time, to mean the quality of heaviness which causes an object to fall. Newton demonstrates its existence now as a universal law: 'Any two particles of matter attract one another with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between them. The researches of William Gilbert , at the start of the 17th century, lead eventually to simple machines with which enthusiasts can generate an electric charge by means of friction. The current generated will give a stimulating frisson to a lady's hand, or can be discharged as a spark.

In an amateur scientist, Ewald Georg von Kleist, dean of the cathedral in Kamien, makes an interesting discovery. After partly filling a glass jar with water, and pushing a metal rod through a cork stopper until it reaches the water, he attaches the end of the nail to his friction machine. After a suitable amount of whirring, the friction machine is disconnected.

When Kleist touches the top of the nail he can feel a slight shock, proving that static electricity has remained in the jar. It is the first time that electricity has been stored in this way, for future discharge, in the type of device known as a capacitor. In the same principle is discovered by Pieter van Musschenbroek, a physicist in the university of Leyden. As a professional, he makes much use of the new device in laboratory experiments.

Though sometimes called a Kleistian jar, it becomes more commonly known as the Leyden jar. Within a year or two an improvement is made which gives the capacitor its lasting identity. The water in the vessel is replaced by a lining of metal foil, with which the metal rod projecting from the jar is in contact. Another layer of metal foil is wrapped round the outside of the jar.

The two foils are charged with equal amounts of electricity, one charge being positive and the other negative. The principle of plates bearing opposite charges, and separated only by a narrow layer of insulation, remains constant in the development of capacitors - much used in modern technology. In the Royal Society in London awards its highest honour, the Copley medal, to William Watson for his researches into electricity.

It is the fashionable subject of the moment, and is about to become more so with the development of the Leyden jar. In Watson sets up an ambitious experiment to discover the speed at which electricity travels. He arranges an electrical circuit more than two miles long, linking the positive and negative metal foils of a Leyden jar. There seems to be no measurable difference between the completion of the circuit and the moment when an observer at the middle of the loop feels the shock.

Watson concludes that electricity is 'instantaneous'. His conclusion is not an accurate description of the flow of electricity, but the experiment is nonetheless impressive. As the leading figure in electrical research, Watson is now in touch with an enthusiastic experimenter on the other side of the Atlantic, Benjamin Franklin.

Watson and Franklin independently arrive at a new and correct concept of electricity - that instead of being created by friction between two surfaces, it is something transferred from one to the other, electrically charging both. They see electricity as the flow of a substance which can be neither created nor destroyed. The total quantity of electricity in an insulated system remains constant.

Franklin, a scientist with a popular touch, coins several of the terms which are now standard - positive and negative, conductor, battery in the sense of a series of Leyden jars linked for simultaneous charge or discharge. His papers on the subject, gathered and published in as Experiments and Observations on Electricity , become the first and perhaps only electrical best-seller.

Widely read in successive English editions, and translated into French, German and Italian, this short book makes Franklin an international celebrity. His reputation is further enhanced, in the following year, when he devises history's most dramatic, and dangerous, electrical experiment. The new Leyden jars are powerful enough to generate a spark which is both visible and audible. It occurs to many that this effect may be the same as that generated in nature in the form of lightning. Franklin invents a way of testing this idea. In Philadelphia, in , he adds a metal tip to a kite and flies it on a wet string into a thunder cloud.

The bottom of the string is attached to a Leyden jar. The point is made when the Leyden jar is successfully charged. For the popular audience Franklin makes the effect visible. He attracts sparks from a key attached to the line. His fame soars. But the next two people attempting the experiment are killed. In conducting his experiment, Franklin already has in mind a practical application if the science proves correct.

He reasons that if celestial electricity can be attracted to a metal point, then a rod projecting from the top of a church steeple, connected by a metal strip to the earth, could serve as a conductor for any stroke of lightning and thus save the building from harm. When the British army proposes to construct a magazine at Purfleet for the storage of gunpowder, William Watson recommends that this highly explosive building be protected by one of Benjamin Franklin's lightning conductors.

The proposal is accepted. The science of electricity finds the first of its myriad eventual roles in everyday life. Joseph Black notices that when ice melts it absorbs a certain amount of heat without any rise in temperature. Heat of this kind as Cavendish later perceives consists of greater activity among the molecules, in a form of energy which will be transferred again if the water freezes. Black calls this phenomenon latent heat, and teaches it in his lectures at the university of Glasgow from An important discovery in itself, it also enables him to be the first to distinguish between heat energy transferred from a warmer to a colder object and temperature the amount of energy present at a given moment.

This History is as yet incomplete. In , Bernoulli solved the differential equation for the vibrations of an elastic bar clamped at one end. Bernoulli's treatment of fluid dynamics and his examination of fluid flow was introduced in his work Hydrodynamica. Rational mechanics dealt primarily with the development of elaborate mathematical treatments of observed motions, using Newtonian principles as a basis, and emphasized improving the tractability of complex calculations and developing of legitimate means of analytical approximation.

A representative contemporary textbook was published by Johann Baptiste Horvath. By the end of the century analytical treatments were rigorous enough to verify the stability of the solar system solely on the basis of Newton's laws without reference to divine intervention—even as deterministic treatments of systems as simple as the three body problem in gravitation remained intractable. In , John Michell suggested that some objects might be so massive that not even light could escape from them. In , Leonhard Euler solved the ordinary differential equation for a forced harmonic oscillator and noticed the resonance phenomenon.

In , Colin Maclaurin discovered his uniformly rotating self-gravitating spheroids. In , Benjamin Robins published his New Principles in Gunnery , establishing the science of aerodynamics. British work, carried on by mathematicians such as Taylor and Maclaurin, fell behind Continental developments as the century progressed. Meanwhile, work flourished at scientific academies on the Continent, led by such mathematicians as Bernoulli, Euler, Lagrange, Laplace, and Legendre. In , Jean le Rond d'Alembert published his Traite de Dynamique , in which he introduced the concept of generalized forces for accelerating systems and systems with constraints, and applied the new idea of virtual work to solve dynamical problem, now known as D'Alembert's principle , as a rival to Newton's second law of motion.

In , Pierre Louis Maupertuis applied minimum principles to mechanics. In , Euler solved the partial differential equation for the vibration of a rectangular drum. In , Euler examined the partial differential equation for the vibration of a circular drum and found one of the Bessel function solutions.

In , John Smeaton published a paper on experiments relating power, work , momentum and kinetic energy , and supporting the conservation of energy. In , Antoine Lavoisier states the law of conservation of mass. The rational mechanics developed in the 18th century received a brilliant exposition in both Lagrange's work and the Celestial Mechanics — of Pierre-Simon Laplace.

During the 18th century, thermodynamics was developed through the theories of weightless "imponderable fluids" , such as heat "caloric" , electricity , and phlogiston which was rapidly overthrown as a concept following Lavoisier's identification of oxygen gas late in the century. Assuming that these concepts were real fluids, their flow could be traced through a mechanical apparatus or chemical reactions.

This tradition of experimentation led to the development of new kinds of experimental apparatus, such as the Leyden Jar ; and new kinds of measuring instruments, such as the calorimeter , and improved versions of old ones, such as the thermometer. Experiments also produced new concepts, such as the University of Glasgow experimenter Joseph Black 's notion of latent heat and Philadelphia intellectual Benjamin Franklin 's characterization of electrical fluid as flowing between places of excess and deficit a concept later reinterpreted in terms of positive and negative charges.

Franklin also showed that lightning is electricity in The accepted theory of heat in the 18th century viewed it as a kind of fluid, called caloric ; although this theory was later shown to be erroneous, a number of scientists adhering to it nevertheless made important discoveries useful in developing the modern theory, including Joseph Black —99 and Henry Cavendish — Opposed to this caloric theory, which had been developed mainly by the chemists, was the less accepted theory dating from Newton's time that heat is due to the motions of the particles of a substance.

This mechanical theory gained support in from the cannon-boring experiments of Count Rumford Benjamin Thompson , who found a direct relationship between heat and mechanical energy. While it was recognized early in the 18th century that finding absolute theories of electrostatic and magnetic force akin to Newton's principles of motion would be an important achievement, none were forthcoming. This impossibility only slowly disappeared as experimental practice became more widespread and more refined in the early years of the 19th century in places such as the newly established Royal Institution in London.

Meanwhile, the analytical methods of rational mechanics began to be applied to experimental phenomena, most influentially with the French mathematician Joseph Fourier 's analytical treatment of the flow of heat, as published in At the end of the century, the members of the French Academy of Sciences had attained clear dominance in the field. The Royal Society and the French Academy of Sciences were major centers for the performance and reporting of experimental work. Experiments in mechanics, optics, magnetism , static electricity , chemistry , and physiology were not clearly distinguished from each other during the 18th century, but significant differences in explanatory schemes and, thus, experiment design were emerging.

Chemical experimenters, for instance, defied attempts to enforce a scheme of abstract Newtonian forces onto chemical affiliations, and instead focused on the isolation and classification of chemical substances and reactions. In , Alessandro Volta invented the electric battery known of the voltaic pile and thus improved the way electric currents could also be studied. A year later, Thomas Young demonstrated the wave nature of light—which received strong experimental support from the work of Augustin-Jean Fresnel —and the principle of interference.

In , Peter Ewart supported the idea of the conservation of energy in his paper On the measure of moving force. In , William Hamilton began his analysis of Hamilton's characteristic function. In , Michael Faraday built an electricity-powered motor, while Georg Ohm stated his law of electrical resistance in , expressing the relationship between voltage, current, and resistance in an electric circuit.

A year later, botanist Robert Brown discovered Brownian motion : pollen grains in water undergoing movement resulting from their bombardment by the fast-moving atoms or molecules in the liquid. In , Gaspard Coriolis introduced the terms of work force times distance and kinetic energy with the meanings they have today. In , Carl Jacobi discovered his uniformly rotating self-gravitating ellipsoids the Jacobi ellipsoid. In , John Russell observed a nondecaying solitary water wave soliton in the Union Canal near Edinburgh and used a water tank to study the dependence of solitary water wave velocities on wave amplitude and water depth.

In , William Hamilton stated Hamilton's canonical equations of motion. In the same year, Gaspard Coriolis examined theoretically the mechanical efficiency of waterwheels, and deduced the Coriolis effect. In , Julius Robert von Mayer , an amateur scientist, wrote a paper on the conservation of energy but his lack of academic training led to its rejection. In , Christian Doppler proposed the Doppler effect. In , Hermann von Helmholtz formally stated the law of conservation of energy. There were important advances in continuum mechanics in the first half of the century, namely formulation of laws of elasticity for solids and discovery of Navier—Stokes equations for fluids.

In the 19th century, the connection between heat and mechanical energy was established quantitatively by Julius Robert von Mayer and James Prescott Joule , who measured the mechanical equivalent of heat in the s. In , Joule published results from his series of experiments including the paddlewheel experiment which show that heat is a form of energy, a fact that was accepted in the s. The relation between heat and energy was important for the development of steam engines, and in the experimental and theoretical work of Sadi Carnot was published.

Carnot captured some of the ideas of thermodynamics in his discussion of the efficiency of an idealized engine. Sadi Carnot's work provided a basis for the formulation of the first law of thermodynamics —a restatement of the law of conservation of energy —which was stated around by William Thomson , later known as Lord Kelvin, and Rudolf Clausius. Kelvin and Clausius also stated the second law of thermodynamics , which was originally formulated in terms of the fact that heat does not spontaneously flow from a colder body to a hotter.

Other formulations followed quickly for example, the second law was expounded in Thomson and Peter Guthrie Tait 's influential work Treatise on Natural Philosophy and Kelvin in particular understood some of the law's general implications. The second Law was the idea that gases consist of molecules in motion had been discussed in some detail by Daniel Bernoulli in , but had fallen out of favor, and was revived by Clausius in In , Joule and Thomson demonstrated that a rapidly expanding gas cools, later named the Joule—Thomson effect or Joule—Kelvin effect.

In , James Clerk Maxwell discovered the distribution law of molecular velocities. Maxwell showed that electric and magnetic fields are propagated outward from their source at a speed equal to that of light and that light is one of several kinds of electromagnetic radiation, differing only in frequency and wavelength from the others.

In , Maxwell worked out the mathematics of the distribution of velocities of the molecules of a gas. The wave theory of light was widely accepted by the time of Maxwell's work on the electromagnetic field, and afterward the study of light and that of electricity and magnetism were closely related. In James Maxwell published his papers on a dynamical theory of the electromagnetic field, and stated that light is an electromagnetic phenomenon in the publication of Maxwell's Treatise on Electricity and Magnetism.

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The encapsulation of heat in particulate motion, and the addition of electromagnetic forces to Newtonian dynamics established an enormously robust theoretical underpinning to physical observations. The prediction that light represented a transmission of energy in wave form through a " luminiferous ether ", and the seeming confirmation of that prediction with Helmholtz student Heinrich Hertz 's detection of electromagnetic radiation , was a major triumph for physical theory and raised the possibility that even more fundamental theories based on the field could soon be developed.

In , Heinrich Hertz discovered the photoelectric effect. Research on the electromagnetic waves began soon after, with many scientists and inventors conducting experiments on their properties. In the mid to late s Guglielmo Marconi developed a radio wave based wireless telegraphy system [57] see invention of radio. The atomic theory of matter had been proposed again in the early 19th century by the chemist John Dalton and became one of the hypotheses of the kinetic-molecular theory of gases developed by Clausius and James Clerk Maxwell to explain the laws of thermodynamics.

The kinetic theory in turn led to a revolutionary approach to science, the statistical mechanics of Ludwig Boltzmann — and Josiah Willard Gibbs — , which studies the statistics of microstates of a system and uses statistics to determine the state of a physical system. Interrelating the statistical likelihood of certain states of organization of these particles with the energy of those states, Clausius reinterpreted the dissipation of energy to be the statistical tendency of molecular configurations to pass toward increasingly likely, increasingly disorganized states coining the term " entropy " to describe the disorganization of a state.

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The statistical versus absolute interpretations of the second law of thermodynamics set up a dispute that would last for several decades producing arguments such as " Maxwell's demon " , and that would not be held to be definitively resolved until the behavior of atoms was firmly established in the early 20th century. At the end of the 19th century, physics had evolved to the point at which classical mechanics could cope with highly complex problems involving macroscopic situations; thermodynamics and kinetic theory were well established; geometrical and physical optics could be understood in terms of electromagnetic waves; and the conservation laws for energy and momentum and mass were widely accepted.

So profound were these and other developments that it was generally accepted that all the important laws of physics had been discovered and that, henceforth, research would be concerned with clearing up minor problems and particularly with improvements of method and measurement.

However, around serious doubts arose about the completeness of the classical theories—the triumph of Maxwell's theories, for example, was undermined by inadequacies that had already begun to appear—and their inability to explain certain physical phenomena, such as the energy distribution in blackbody radiation and the photoelectric effect , while some of the theoretical formulations led to paradoxes when pushed to the limit. Prominent physicists such as Hendrik Lorentz , Emil Cohn , Ernst Wiechert and Wilhelm Wien believed that some modification of Maxwell's equations might provide the basis for all physical laws.

These shortcomings of classical physics were never to be resolved and new ideas were required. At the beginning of the 20th century a major revolution shook the world of physics, which led to a new era, generally referred to as modern physics. In , J. Thomson discovered the electron , and new radioactive elements found by Marie and Pierre Curie raised questions about the supposedly indestructible atom and the nature of matter.

Marie and Pierre coined the term " radioactivity " to describe this property of matter, and isolated the radioactive elements radium and polonium. Ernest Rutherford and Frederick Soddy identified two of Becquerel's forms of radiation with electrons and the element helium.

Rutherford identified and named two types of radioactivity and in interpreted experimental evidence as showing that the atom consists of a dense, positively charged nucleus surrounded by negatively charged electrons. Classical theory, however, predicted that this structure should be unstable. Classical theory had also failed to explain successfully two other experimental results that appeared in the late 19th century. One of these was the demonstration by Albert A. Michelson and Edward W.

Morley —known as the Michelson—Morley experiment —which showed there did not seem to be a preferred frame of reference, at rest with respect to the hypothetical luminiferous ether , for describing electromagnetic phenomena. Studies of radiation and radioactive decay continued to be a preeminent focus for physical and chemical research through the s, when the discovery of nuclear fission opened the way to the practical exploitation of what came to be called "atomic" energy.

In a young, year-old German physicist then a Bern patent clerk named Albert Einstein — , showed how measurements of time and space are affected by motion between an observer and what is being observed. To say that Einstein's radical theory of relativity revolutionized science is no exaggeration. Although Einstein made many other important contributions to science, the theory of relativity alone represents one of the greatest intellectual achievements of all time. Although the concept of relativity was not introduced by Einstein, his major contribution was the recognition that the speed of light in a vacuum is constant, i.

This does not impact a person's day-to-day life since most objects travel at speeds much slower than light speed. For objects travelling near light speed, however, the theory of relativity shows that clocks associated with those objects will run more slowly and that the objects shorten in length according to measurements of an observer on Earth. Einstein argued that the speed of light was a constant in all inertial reference frames and that electromagnetic laws should remain valid independent of reference frame—assertions which rendered the ether "superfluous" to physical theory, and that held that observations of time and length varied relative to how the observer was moving with respect to the object being measured what came to be called the " special theory of relativity ".

In another paper published the same year, Einstein asserted that electromagnetic radiation was transmitted in discrete quantities " quanta " , according to a constant that the theoretical physicist Max Planck had posited in to arrive at an accurate theory for the distribution of blackbody radiation —an assumption that explained the strange properties of the photoelectric effect. The special theory of relativity is a formulation of the relationship between physical observations and the concepts of space and time.

The theory arose out of contradictions between electromagnetism and Newtonian mechanics and had great impact on both those areas. The original historical issue was whether it was meaningful to discuss the electromagnetic wave-carrying "ether" and motion relative to it and also whether one could detect such motion, as was unsuccessfully attempted in the Michelson—Morley experiment. Einstein demolished these questions and the ether concept in his special theory of relativity.

However, his basic formulation does not involve detailed electromagnetic theory. It arises out of the question: "What is time? Einstein had the genius to question it, and found that it was incomplete. Instead, each "observer" necessarily makes use of his or her own scale of time, and for two observers in relative motion, their time-scales will differ. This induces a related effect on position measurements. Space and time become intertwined concepts, fundamentally dependent on the observer. Each observer presides over his or her own space-time framework or coordinate system.

There being no absolute frame of reference, all observers of given events make different but equally valid and reconcilable measurements. What remains absolute is stated in Einstein's relativity postulate: "The basic laws of physics are identical for two observers who have a constant relative velocity with respect to each other. Special Relativity exerted another long-lasting effect on dynamics.

Although initially it was credited with the "unification of mass and energy", it became evident that relativistic dynamics established a firm distinction between rest mass , which is an invariant observer independent property of a particle or system of particles, and the energy and momentum of a system. The latter two are separately conserved in all situations but not invariant with respect to different observers. The term mass in particle physics underwent a semantic change , and since the late 20th century it almost exclusively denotes the rest or invariant mass.

See mass in special relativity for additional discussion. By , Einstein was able to generalize this further, to deal with all states of motion including non-uniform acceleration, which became the general theory of relativity. In this theory Einstein also specified a new concept, the curvature of space-time, which described the gravitational effect at every point in space.

In fact, the curvature of space-time completely replaced Newton's universal law of gravitation. According to Einstein, gravitational force in the normal sense is a kind of illusion caused by the geometry of space. The presence of a mass causes a curvature of space-time in the vicinity of the mass, and this curvature dictates the space-time path that all freely-moving objects must follow. It was also predicted from this theory that light should be subject to gravity - all of which was verified experimentally. This aspect of relativity explained the phenomena of light bending around the sun, predicted black holes as well as properties of the Cosmic microwave background radiation — a discovery rendering fundamental anomalies in the classic Steady-State hypothesis.

For his work on relativity, the photoelectric effect and blackbody radiation, Einstein received the Nobel Prize in The gradual acceptance of Einstein's theories of relativity and the quantized nature of light transmission, and of Niels Bohr's model of the atom created as many problems as they solved, leading to a full-scale effort to reestablish physics on new fundamental principles.

Expanding relativity to cases of accelerating reference frames the " general theory of relativity " in the s, Einstein posited an equivalence between the inertial force of acceleration and the force of gravity, leading to the conclusion that space is curved and finite in size, and the prediction of such phenomena as gravitational lensing and the distortion of time in gravitational fields.

Although relativity resolved the electromagnetic phenomena conflict demonstrated by Michelson and Morley, a second theoretical problem was the explanation of the distribution of electromagnetic radiation emitted by a black body ; experiment showed that at shorter wavelengths, toward the ultraviolet end of the spectrum, the energy approached zero, but classical theory predicted it should become infinite.

This glaring discrepancy, known as the ultraviolet catastrophe , was solved by the new theory of quantum mechanics. Quantum mechanics is the theory of atoms and subatomic systems. Approximately the first 30 years of the 20th century represent the time of the conception and evolution of the theory. The basic ideas of quantum theory were introduced in by Max Planck — , who was awarded the Nobel Prize for Physics in for his discovery of the quantified nature of energy.

The quantum theory which previously relied in the "correspondence" at large scales between the quantized world of the atom and the continuities of the " classical " world was accepted when the Compton Effect established that light carries momentum and can scatter off particles, and when Louis de Broglie asserted that matter can be seen as behaving as a wave in much the same way as electromagnetic waves behave like particles wave—particle duality.

In , Einstein used the quantum theory to explain the photoelectric effect, and in the Danish physicist Niels Bohr used the same constant to explain the stability of Rutherford's atom as well as the frequencies of light emitted by hydrogen gas. The quantized theory of the atom gave way to a full-scale quantum mechanics in the s.

New principles of a "quantum" rather than a "classical" mechanics, formulated in matrix-form by Werner Heisenberg , Max Born , and Pascual Jordan in , were based on the probabilistic relationship between discrete "states" and denied the possibility of causality.

Also in the s, the Indian scientist Satyendra Nath Bose 's work on photons and quantum mechanics provided the foundation for Bose—Einstein statistics , the theory of the Bose—Einstein condensate. The spin—statistics theorem established that any particle in quantum mechanics may be either a boson statistically Bose—Einstein or a fermion statistically Fermi—Dirac.

It was later found that all fundamental bosons transmit forces, such as the photon that transmits electromagnetism. Fermions are particles "like electrons and nucleons" and are the usual constituents of matter. Fermi—Dirac statistics later found numerous other uses, from astrophysics see Degenerate matter to semiconductor design. As the philosophically inclined continued to debate the fundamental nature of the universe, quantum theories continued to be produced, beginning with Paul Dirac 's formulation of a relativistic quantum theory in However, attempts to quantize electromagnetic theory entirely were stymied throughout the s by theoretical formulations yielding infinite energies.

Meanwhile, new theories of fundamental particles proliferated with the rise of the idea of the quantization of fields through " exchange forces " regulated by an exchange of short-lived "virtual" particles , which were allowed to exist according to the laws governing the uncertainties inherent in the quantum world. Notably, Hideki Yukawa proposed that the positive charges of the nucleus were kept together courtesy of a powerful but short-range force mediated by a particle with a mass between that of the electron and proton.

This particle, the " pion ", was identified in as part of what became a slew of particles discovered after World War II. Initially, such particles were found as ionizing radiation left by cosmic rays , but increasingly came to be produced in newer and more powerful particle accelerators. Einstein deemed that all fundamental interactions in nature can be explained in a single theory.

Unified field theories were numerous attempts to "merge" several interactions. One of formulations of such theories as well as field theories in general is a gauge theory , a generalization of the idea of symmetry. Eventually the Standard Model see below succeeded in unification of strong, weak, and electromagnetic interactions. All attempts to unify gravitation with something else failed. The interaction of these particles by scattering and decay provided a key to new fundamental quantum theories.

Murray Gell-Mann and Yuval Ne'eman brought some order to these new particles by classifying them according to certain qualities, beginning with what Gell-Mann referred to as the " Eightfold Way ". While its further development, the quark model , at first seemed inadequate to describe strong nuclear forces , allowing the temporary rise of competing theories such as the S-Matrix , the establishment of quantum chromodynamics in the s finalized a set of fundamental and exchange particles, which allowed for the establishment of a " standard model " based on the mathematics of gauge invariance , which successfully described all forces except for gravitation , and which remains generally accepted within its domain of application.

The formulation of the unification of the electromagnetic and weak interactions in the standard model is due to Abdus Salam , Steven Weinberg and, subsequently, Sheldon Glashow. Electroweak theory was later confirmed experimentally by observation of neutral weak currents , [64] [65] [66] [67] and distinguished by the Nobel Prize in Physics. Since the s, fundamental particle physics has provided insights into early universe cosmology , particularly the Big Bang theory proposed as a consequence of Einstein's general theory of relativity.

However, starting in the s, astronomical observations have also provided new challenges, such as the need for new explanations of galactic stability " dark matter " and the apparent acceleration in the expansion of the universe " dark energy ". While accelerators have confirmed most aspects of the Standard Model by detecting expected particle interactions at various collision energies, no theory reconciling general relativity with the Standard Model has yet been found, although supersymmetry and string theory were believed by many theorists to be a promising avenue forward.

The Large Hadron Collider , however, which began operating in , has failed to find any evidence whatsoever that is supportive of supersymmetry and string theory. Cosmology may be said to have become a serious research question with the publication of Einstein's General Theory of Relativity in although it did not enter the scientific mainstream until the period known as the " Golden age of general relativity ". About a decade later, in the midst of what was dubbed the " Great Debate ", Hubble and Slipher discovered the expansion of universe in the s measuring the redshifts of Doppler spectra from galactic nebulae.

A rival, called the steady state theory was devised by Hoyle , Gold , Narlikar and Bondi. Cosmic background radiation was verified in the s by Penzias and Wilson , and this discovery favoured the big bang at the expense of the steady state scenario. Later work was by Smoot et al. The s the same decade of the COBE measurements also saw the proposal of inflation theory by Guth. Recently the problems of dark matter and dark energy have risen to the top of the cosmology agenda. On July 4, , physicists working at CERN's Large Hadron Collider announced that they had discovered a new subatomic particle greatly resembling the Higgs boson , a potential key to an understanding of why elementary particles have mass and indeed to the existence of diversity and life in the universe.

This is a big moment for particle physics and a crossroads — will this be the high water mark or will it be the first of many discoveries that point us toward solving the really big questions that we have posed? Peter Higgs was one of six physicists, working in three independent groups, who, in , invented the notion of the Higgs field "cosmic molasses". Although they have never been seen, Higgslike fields play an important role in theories of the universe and in string theory.

Under certain conditions, according to the strange accounting of Einsteinian physics, they can become suffused with energy that exerts an antigravitational force. Such fields have been proposed as the source of an enormous burst of expansion, known as inflation, early in the universe and, possibly, as the secret of the dark energy that now seems to be speeding up the expansion of the universe. With increased accessibility to and elaboration upon advanced analytical techniques in the 19th century, physics was defined as much, if not more, by those techniques than by the search for universal principles of motion and energy, and the fundamental nature of matter.

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Fields such as acoustics , geophysics , astrophysics , aerodynamics , plasma physics , low-temperature physics , and solid-state physics joined optics , fluid dynamics , electromagnetism , and mechanics as areas of physical research. In the 20th century, physics also became closely allied with such fields as electrical , aerospace and materials engineering, and physicists began to work in government and industrial laboratories as much as in academic settings. Using a whole body of mathematical methods not only those inherited from the antique theory of ratios and infinitesimal techniques, but also the methods of the contemporary algebra and fine calculation techniques , Islamic scientists raised statics to a new, higher level.

The classical results of Archimedes in the theory of the centre of gravity were generalized and applied to three-dimensional bodies, the theory of ponderable lever was founded and the 'science of gravity' was created and later further developed in medieval Europe. The phenomena of statics were studied by using the dynamic approach so that two trends — statics and dynamics — turned out to be inter-related within a single science, mechanics.

Numerous fine experimental methods were developed for determining the specific weight, which were based, in particular, on the theory of balances and weighing. The classical works of al-Biruni and al-Khazini can by right be considered as the beginning of the application of experimental methods in medieval science. It played an important part in the prehistory of classical mechanics in medieval Europe. Without it classical mechanics proper could probably not have been created. From Wikipedia, the free encyclopedia.

Further information: History of astronomy. Further information: History of science and technology in China and History of Indian science and technology. Main articles: Physics in medieval Islam and Science in the medieval Islamic world. See also: List of Muslim scientists. Further information: Theory of impetus. Main article: Galileo Galilei.

Main articles: Isaac Newton and History of classical mechanics. Further information: History of thermodynamics. Further information: History of statistical mechanics. See also: Modern physics. Further information: History of special relativity. Further information: History of general relativity. Further information: History of quantum mechanics. Further information: History of subatomic physics and List of unsolved problems in physics. Main article: Unified field theory. This section needs expansion. You can help by adding to it. January Main article: Standard Model.

Main article: Physical cosmology.


  • History of physics.
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Main article: List of important publications in physics. Almagest Geographia Apotelesmatika. Physics portal Science portal. History of optics History of electrical engineering History of electromagnetism List of physicists Nobel Prize in physics List of Nobel laureates in Physics Timeline of fundamental physics discoveries. Levinova , "Statics", p. Routledge, , page Aimant et Boussole", Isis , Vol. Cambridge University Press. BBC News. Alhazen or Al-Haytham; — was perhaps one of the greatest physicists of all times and a product of the Islamic Golden Age or Islamic Renaissance 7th—13th centuries.

He made significant contributions to anatomy, astronomy, engineering, mathematics , medicine, ophthalmology, philosophy, physics, psychology, and visual perception and is primarily attributed as the inventor of the scientific method, for which author Bradley Steffens describes him as the "first scientist".