History of physics 13758 225799086 2008-07-15T13:30:45Z SmackBot 433328 Date the maintenance tags or general fixes {{histOfScience}} Since antiquity, human beings have sought to understand the workings of nature: why unsupported objects drop to the ground, why different [[materials science|materials]] have different properties, the character of the [[universe]] such as the form of the [[Earth]] and the behavior of celestial objects such as the [[Sun]] and the [[Moon]], and so forth. Typically the behavior and nature of the world was explained by invoking the actions of [[deity|gods]]. Eventually explanations were proposed based on [[philosophy|philosophical]] speculation. Rarely verified by systematic [[experiment]]al testing, many of them were wrong, but this is part of the [[dialectic]]al nature of scientific inquiry, and even modern theories of [[quantum mechanics]] and [[Theory of relativity|relativity]] are merely considered "theories that have not been broken yet". The growth of '''[[physics]]''' has brought not only fundamental changes in ideas about the [[nature|material world]], [[mathematics]] and [[philosophy]], but also, through [[technology]], a transformation of [[society]]. Physics is considered both a body of knowledge and the practice that makes and transmits it. [[Experimental physics]] began in the [[Middle Ages]] with experimental investigations into [[optics]], [[statics]] and [[dynamics]]. The [[Scientific Revolution]], beginning around [[1543]], is considered a convenient boundary between ancient thought and [[classical mechanics]]. The emergence of physics as a science distinct from [[natural philosophy]] began with the Scientific Revolution of the 16th and 17th centuries, and continued through the dawn of modern physics in the early 20th century. The year [[1900]] marks the beginnings of a more modern physics. Today, the [[science]] shows no sign of completion, as more issues are raised, with questions rising from the [[age of the universe]], to the nature of the [[vacuum]], to the ultimate nature of the properties of [[subatomic particle]]s. [[Laws of physics|Partial theories]] are currently the best that physics has to offer, at the present time. The list of [[unsolved problems in physics]] is large. ==Antiquity== {{see|History of science in early cultures|History of science in Classical Antiquity|History of astronomy}} The first records of the recognition that astronomical phenomena are periodic and of the application of mathematics to their prediction is [[Babylonian astronomy|Babylonian]]. Tablets dating back to the [[Old Babylonian period]] ([[2nd millennium BC]]) document the application of mathematics to the variation in the length of daylight over a solar year. Centuries of Babylonian observations of celestial phenomena are recorded in the series of [[cuneiform]] tablets known as the ''Enūma Anu Enlil''..<ref>{{Harvtxt|Pingree|1998}}<br>{{Harvtxt|Rochberg|2004}}<br>{{Harvtxt|Evans|1998}}</ref> [[Babylonian influence on Greek astronomy|Babylonian astronomy]] was the basis for much of what was done in Greece, in India, in Sassanian Iran, in Byzantium, in Syria, in Islam, in Central Asia, and in Western Europe.<ref name=dp1998>{{Harvtxt|Pingree|1998}}</ref> Further investigations into early ideas in physics began with eminent [[Ancient Greece|Greek]] [[pre-Socratic]] philosophers such as [[Thales]], [[Anaximander]], possibly [[Pythagoras]], [[Heraclitus]], [[Anaxagoras]], [[Empedocles]] and [[Philolaus]], many of whom were involved in various schools. For example, Anaximander and Thales belonged to the [[Milesian school]]. [[Image:Francesco Hayez 001.jpg|thumb|150px|left|[[Aristotle]], founder of [[Aristotelian physics]] ]] [[Plato]], briefly and [[Aristotle]] at length, continued these studies of nature in their works, the earliest surviving complete treatises dealing with [[natural philosophy]]. [[Democritus]], a contemporary, was of the school of [[Atomism|Atomists]] who attempted to characterize the nature of matter. Similar atomic philosophy would develop in ancient India. Due to the absence of advanced experimental equipment such as [[telescope]]s and accurate time-keeping devices, experimental testing of physical hypotheses was impossible or impractical. There were exceptions and there are [[anachronism]]s. Greek thinkers like Archimedes proposed calculating the volume of objects like [[sphere]]s and [[cone (geometry)|cones]] by dividing them into very thin disks and adding up the volume of each disk, using methods resembling [[integral calculus]]. It was also [[Archimedes]] who derived many correct quantitative descriptions of mechanics and also hydrostatics when, so the story goes, he noticed that his own body displaced a volume of water while he was getting into a bath one day. In doing so [[Archimedes]] would be the first to uncover a [[law of nature]]. Another remarkable example was that of [[Eratosthenes]], who deduced that the [[Earth]] was a sphere, and accurately calculated its circumference using the shadows of vertical sticks to measure the angle between two widely separated points on the Earth's surface. Modern knowledge of many early ideas in physics, and the extent to which they were experimentally tested, is unknown. Almost all direct record of these ideas was lost when the [[Library of Alexandria]] was destroyed, around [[400]] AD. Perhaps the most remarkable idea we know of from this era was the deduction by [[Aristarchus of Samos]] that the Earth was a planet that traveled around the Sun once a year, and rotated on its axis once a day (accounting for the seasons and the cycle of day and night), and that the stars were other, very distant suns which also had their own accompanying planets (and possibly, lifeforms upon those planets). [[Image:Baghdad Battery-NASA Publication.PNG|right|thumb|[[Baghdad Battery]] from ancient [[Mesopotamia]] ]] The discovery of the [[Antikythera mechanism]], which is considered to be the earliest [[analog computer]], points to a detailed understanding of movements of these astronomical objects, as well as a use of [[gear]]-trains that pre-dates any other known civilization's use of gears, except that of [[ancient China]]. The discovery of the [[Baghdad Battery]] also suggests that a primitive form of [[electricity]] may have been known in [[Mesopotamia]] during the [[Parthia]]n or [[Sassanid Empire|Sassanid]] periods. A primitive [[Steam engine|steam-powered]] device, [[Hero of Alexandria|Hero]]'s [[aeolipile]], was only a curiosity which did not solve the problem of transforming its rotational energy into a more usable form, not even by gears. The [[Archimedes screw]] is still in use today, to lift water from rivers onto irrigated farmland. The simple machines were unremarked, with the exception (at least) of Archimedes' elegant proof of the law of the [[lever]]. Ramps were in use several millennia before Archimedes, to build the Pyramids. A particularly important ancient contribution that would allow physics to develop into a science came from [[History of India|India]]. It was the introduction of the [[Hindu-Arabic numerals]]. Modern physics can hardly be imagined without a system of arithmetic in which simple calculation is easy enough to make large calculations even possible. The modern [[Positional notation|positional]] [[numeral system]] (the [[Hindu-Arabic numeral system]]) and the number [[0 (number)|zero]] were first developed in India. ==Physics in the Middle Ages== ===Islamic world=== {{main|Islamic physics}} {{see|Book of Optics|Islamic science|List of Muslim scientists}} Like the later [[Scientific revolution]] in the [[Western world|West]], Islamic science was built on a foundation laid in antiquity, in this case, the intellectual patrimony of the [[Byzantines]], [[Persians]] and [[India]]ns they conquered. The Arab and Persian scholars of the [[Islamic Golden Age]] made advances by building on previous work in astronomy, mathematics, and physics while developing new fields like modern [[optics]],<ref name=Verma>R. L. Verma, "Al-Hazen: father of modern optics", ''Al-Arabi'', 8 (1969): 12-13.</ref> [[experimental physics]],<ref name=Thiele>Rüdiger Thiele (2005). "In Memoriam: Matthias Schramm", ''Arabic Sciences and Philosophy'' '''15''', p. 329–331. [[Cambridge University Press]].</ref> and [[hydrodynamics]].<ref name=Rozhanskaya>Mariam Rozhanskaya and I. S. Levinova (1996), "Statics", p. 642, in {{Harvard reference |last1=Morelon |first1=Régis |last2=Rashed |first2=Roshdi |year=1996 |title=[[Encyclopedia of the History of Arabic Science]] |volume=3 |publisher=[[Routledge]] |isbn=0415124107 |pages=614-642}}: {{quote|"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), Arabic 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 apporach so that two trends - statics and dynamics - turned out to be inter-related withina single science, mechanics. The combination of the dynamic apporach with Archimedean hydrostatics gave birth to a direction in science which may be called medieval hydrodynamics. [...] 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]]."}}</ref> [[Image:Ibn haithem portrait.jpg|thumb|right|200px|[[Ibn al-Haytham]] (Alhazen), considered the "father of modern [[optics]]" and a pioneer of [[scientific method]] and [[experimental physics]] ]] The most important scientific development during the [[Middle Ages]] was the pioneering development of the [[experiment]]al [[scientific method]] by [[Ibn al-Haytham]] (commonly Latinized ''Alhazen'', ''ca.'' 965–1040), as recorded in his ''[[Book of Optics]]''.<ref name=Gorini>Rosanna Gorini (2003). "Al-Haytham the Man of Experience. First Steps in the Science of Vision", ''International Society for the History of Islamic Medicine''. Institute of Neurosciences, Laboratory of Psychobiology and Psychopharmacology, Rome, Italy: {{quote|"According to the majority of the historians al-Haytham was the pioneer of the modern scientific method. With his book he changed the meaning of the term [[optics]] and established experiments as the norm of proof in the field. His investigations are based not on abstract theories, but on experimental evidences and his experiments were systematic and repeatable."}}</ref> Alhazen, who is regarded as the "father of modern [[optics]]",<ref name=Verma/> and a pioneer of the [[scientific method]]<ref name=Gorini/> and [[experimental physics]],<ref name=Thiele/> developed a broad theory that explained vision, using [[geometry]] and [[anatomy]], which stated that each point on an illuminated area or object radiates light rays in every direction, but that only one ray from each point, which strikes the eye perpendicularly, can be seen. The other rays strike at different angles and are not seen. He built a [[camera obscura]] and used the example of the [[pinhole camera]], which produces an inverted image, to support his argument.<ref>David C. Lindberg, "The Theory of Pinhole Images from Antiquity to the Thirteenth Century," ''Archive for History of the Exact Sciences'', 5(1968):154-176.</ref> This contradicted [[Ptolemy]]'s [[Emission theory (vision)|emission theory of vision]] that objects are seen by rays of light emanating from the eyes.<ref>D. C. Lindberg, "Alhazen's Theory of Vision and its Reception in the West", ''Isis'', 58 (1967), p. 322.</ref> Alhazen held light rays to be streams of minute particles<ref name=Rashed>Roshdi Rashed (2007). "The Celestial Kinematics of Ibn al-Haytham", ''Arabic Sciences and Philosophy'' '''17''', p. 19. [[Cambridge University Press]].</ref> travelling at a finite speed.<ref name=Hamarneh>{{Citation |last=Hamarneh |first=Sami |year=1972 |title=Review: Hakim Mohammed Said, ''Ibn al-Haitham'' |journal=[[Isis (journal)|Isis]] |volume=63 |issue=1 |pages=118–119 [119] |doi=10.1086/350861 }}</ref> He improved Ptolemy's theory of the [[refraction]] of light, and went on to discover the [[Snell's law|law of refraction]].<ref>[[George Sarton]], ''Introduction to the History of Science'', "The Time of Al-Biruni": {{quote|[Ibn al-Haytham] was not only the greatest Muslim physicist, but by all means the greatest of [[Middle Ages|mediaeval times]].}} {{quote|Ibn Haytham's writings reveal his fine development of the experimental faculty. His tables of corresponding [[Angle of incidence|angles of incidence]] and refraction of light passing from one medium to another show how closely he had approached discovering the [[Snell's law|law of constancy of ratio of sines]], later attributed to [[Willebrord Snellius|Snell]]. He accounted correctly for twilight as due to [[atmospheric refraction]], estimating the sun's depression to be 19 degrees below the horizon, at the commencement of the phenomenon in the mornings or at its termination in the evenings.}}</ref><ref>{{cite web|author=Dr. A. Zahoor and Dr. Z. Haq|date=1997|url=http://www.cyberistan.org/islamic/Introl1.html|title=Quotations from Famous Historians of Science|publisher=Cyberistan|accessdate=2008-01-23}}</ref> He also carried out the first experiments on the dispersion of light into its constituent colors.<ref name=Deek>Dr. Mahmoud Al Deek. "Ibn Al-Haitham: Master of Optics, Mathematics, Physics and Medicine", ''Al Shindagah'', November-December 2004.</ref> His major work ''[[Book of Optics]]'' was translated into [[Latin]] in the [[Middle Ages]], as well as his book dealing with the colors of sunset. He dealt at length with the theory of various physical phenomena like shadows, eclipses, and the rainbow. He also attempted to explain [[binocular vision]] and the [[moon illusion]].<ref name=Hamarneh/> Through these extensive researches on optics, he is considered the "father of modern [[optics]]".<ref name=Verma/> Alhazen also correctly argued that we see objects because the sun's rays of light, which he believed to be streams of tiny particles<ref name=Rashed/> traveling in straight lines, are reflected from objects into our eyes.<ref>J. J. O'Connor and E. F. Robertson (2002). [http://www-groups.dcs.st-and.ac.uk/~history/HistTopics/Light_1.html Light through the ages: Ancient Greece to Maxwell], ''[[MacTutor History of Mathematics archive]]''.</ref> He understood that light must travel at a large but finite velocity, and that refraction is caused by the velocity being different in different substances.<ref name=Hamarneh/> He also studied spherical and parabolic mirrors, and understood how refraction by a lens will allow images to be focused and magnification to take place.<ref name=Bizri>{{Citation |last=El-Bizri |first=Nader |year=2006 |contribution=Ibn al-Haytham or Alhazen |editor-last=Meri |editor-first=Josef W. |title=Medieval Islamic Civilization: An Encyclopaedia |volume=II |pages=343–345 |publisher=[[Routledge]], [[New York]] & [[London]] }}</ref> He understood mathematically why a spherical mirror produces [[spherical aberration]]. [[Avicenna]] (980-1037) agreed that the [[speed of light]] is finite, as he "observed that if the perception of light is due to the emission of some sort of particles by a luminous source, the speed of light must be finite."<ref>[[George Sarton]], ''Introduction to the History of Science'', Vol. 1, p. 710</ref> [[Abū Rayhān al-Bīrūnī]] (973-1048) also agreed that light has a finite speed, and he was the first to discover that the speed of light is much faster than the [[speed of sound]].<ref name=Biruni>{{MacTutor|id=Al-Biruni|title=Al-Biruni}}</ref> [[Qutb al-Din al-Shirazi]] (1236-1311) and [[Kamāl al-Dīn al-Fārisī]] (1260-1320) gave the first correct explanations for the [[rainbow]] phenomenon.<ref>{{MacTutor|id=Al-Farisi|title=Al-Farisi}}</ref> [[Image:Abu-Rayhan Biruni 1973 Afghanistan post stamp.jpg|thumb|left|[[Abū al-Rayhān al-Bīrūnī]], a pioneer of [[hydrodynamics]] and experimental [[mechanics]] ]] In [[mechanics]], the eldest [[Banū Mūsā]] brother, [[Ja'far Muhammad ibn Mūsā ibn Shākir|Muhammad ibn Musa]], in his ''Astral Motion'' and ''The Force of Attraction'', hypothesized that there was a [[force]] of [[Gravitation|attraction]] between heavenly bodies in the 9th century.<ref>K. A. Waheed (1978). ''Islam and The Origins of Modern Science'', p. 27. Islamic Publication Ltd., Lahore.</ref> [[Abū Rayhān al-Bīrūnī]] (973-1048), and later [[al-Khazini]], developed [[experiment]]al [[scientific method]]s for mechanics, especially the fields of [[statics]] and [[dynamics]], particularly for determining [[specific weight]]s, such as those based on the theory of [[balance]]s and [[Weighing scale|weighing]]. Muslim physicists unified statics and dynamics into the science of mechanics, and they combined the fields of [[hydrostatics]] with dynamics to give birth to [[hydrodynamics]]. They applied the mathematical theories of [[ratio]]s and [[infinitesimal]] techniques, and introduced [[algebra]]ic and fine [[calculation]] techniques into the field of statics. They were also generalized the theory of the [[centre of gravity]] and applied it to [[Three-dimensional space|three-dimensional]] bodies. They also founded the theory of the [[wiktionary:ponderable|ponderable]] [[lever]] and created the "science of [[gravity]]" which was later further developed in medieval Europe.<ref name=Rozhanskaya/> Al-Biruni also theorized that [[acceleration]] is connected with non-uniform motion.<ref name=Biruni/> [[Image:Avicenna Persian Physician.jpg|thumb|right|[[Avicenna]], a pioneer of the [[inertia]] and [[momentum]] concepts]] In the early 11th century, [[Ibn al-Haytham]] discussed the theory of [[Gravitation|attraction]] between [[mass]]es, and it seems that he was aware of the [[Magnitude (mathematics)|magnitude]] of [[acceleration]] due to [[gravity]],<ref name=Bizri/> and he stated that the heavenly bodies "were accountable to the [[Physical law|laws of physics]]".<ref>Duhem, Pierre (1908, 1969). ''To Save the Phenomena: An Essay on the Idea of Physical theory from Plato to Galileo'', p. 28. University of Chicago Press, Chicago.</ref> also enunciated the law of [[inertia]] when he stated that a body moves [[perpetual motion|perpetually]] unless an external force stops it or changes its direction of motion.<ref name=Bizri>Dr. [[Nader El-Bizri]], "Ibn al-Haytham or Alhazen", in Josef W. Meri (2006), ''Medieval Islamic Civilization: An Encyclopaedia'', Vol. II, p. 343-345, [[Routledge]], New York, London.</ref> He also developed the concept of [[momentum]],<ref>Seyyed [[Hossein Nasr]], "The achievements of Ibn Sina in the field of science and his contributions to its philosophy", ''Islam & Science'', December 2003.</ref> though he did not quantify this concept mathematically. His contemporary [[Avicenna]] also developed the concept of [[momentum]], referring to [[Theory of impetus|impetus]] as being proportional to [[weight]] times [[velocity]],<ref name=Sayili>A. Sayili (1987), "Ibn Sīnā and Buridan on the Motion of the Projectile", ''Annals of the New York Academy of Sciences'' '''500''' (1), p. 477–482: {{quote|"Thus he considered impetus as proportional to weight times velocity. In other words, his conception of impetus comes very close to the concept of momentum of Newtonian mechanics."}}</ref> for which he is considered a pioneer of the concept of momentum.<ref>Seyyed [[Hossein Nasr]], "Islamic Conception Of Intellectual Life", in Philip P. Wiener (ed.), ''Dictionary of the History of Ideas'', Vol. 2, p. 65, Charles Scribner's Sons, New York, 1973-1974.</ref> His theory of motion was also consistent with the concept of [[inertia]] in [[classical mechanics]].<ref name=Sayili/> In 1121, [[al-Khazini]], in his treatise ''The Book of the Balance of Wisdom'', further elaborated an idea proposed by the [[Greeks]] that all bodies are attracted towards the [[Centre (geometry)|center]] of the earth.<ref>N. Khanikoff (1858-1860), ed. and trans., "Analysis and Extracts of ... Book of the Balance of Wisdom, An Arabic Work on the Water-Balance, Written by 'Al-Khâzinî in the Twelfth Century", ''Journal of the American Oriental Society'' '''6''': 1-128 [39]: {{quote|"But the ideas of the Arab philosophers with regard to gravitation are, in my opinion, much more remarkable; I will not call it universal gravitation, for our author expressly exempts the heavenly bodies from the influence of this force, but terrestrial gravitation. That this great law of nature did not present itself to their minds in the form of a mutual attraction of all existing bodies, as Newton enunciated it five centuries later, is quite natural, for at the time when the principles exhibited by our author were brought forward, the earth was still regarded as fixed immovably in the centre of the universe, and even the centrifugal force had not yet been discovered. But what is more astonishing is the fact that, having inherited from the Greeks the doctrine that all bodies are attracted toward the centre of the earth, and that this attraction acts in the direct ratio of the mass, having moreover not failed to perceive that attraction is a function of the distance of the bodies attracted from the centre of attraction, and having even been aware that, if the centre of the earth were surrounded by concentric spheres, all bodies of equal mass placed upon those spherical surfaces would press equally upon the same surfaces, and differently upon each sphere – that, in spite of all this, they held that weight was directly as the mass and the distance from the centre of the earth, without even suspecting, so far as it appears, that this attraction might be mutual between the body attracting and the bodies attracted, and that the law as enunciated by them was inconsistent with the principle which they admitted, that the containing surface of a liquid in equilibrium is a spherical surface."}}</ref> Al-Khazini also developed the concept of [[gravitational potential energy]]<ref>Mariam Rozhanskaya and I. S. Levinova (1996), "Statics", p. 621, in {{Harvard reference |last1=Morelon |first1=Régis |last2=Rashed |first2=Roshdi |year=1996 |title=[[Encyclopedia of the History of Arabic Science]] |volume=3 |publisher=[[Routledge]] |isbn=0415124107 |pages=614-642}}</ref> and was one of the first to clearly differentiate between [[force]], [[mass]], and [[weight]].<ref>Salah Zaimeche PhD (2005), [http://www.muslimheritage.com/uploads/Merv.pdf Merv], p. 5-7. Foundation for Science Technology and Civilization</ref> [[Ibn Bajjah|Avempace]] (d. 1138) argued that there is always a [[Reaction (physics)|reaction]] force for every force exerted,<ref name = "pines">[[Shlomo Pines]] (1964), "La dynamique d’Ibn Bajja", in ''Mélanges Alexandre Koyré'', I, 442-468 [462, 468], Paris <br>([[cf.]] Abel B. Franco (October 2003), "Avempace, Projectile Motion, and Impetus Theory", ''Journal of the History of Ideas'' '''64''' (4): 521-546 [543])</ref> though he did not refer to the reaction force as being equal to the exerted force.<ref>Abel B. Franco (October 2003), "Avempace, Projectile Motion, and Impetus Theory", ''Journal of the History of Ideas'' '''64''' (4):521-546 [543])</ref> His theory of motion had an influence on later physicists like [[Galileo Galilei]].<ref>Ernest A. Moody (1951). "Galileo and Avempace: The Dynamics of the Leaning Tower Experiment (I)", ''Journal of the History of Ideas'' '''12''' (2), p. 163-193.</ref> His contemporary [[Hibat Allah Abu'l-Barakat al-Baghdaadi]] was the first to negate [[Aristotle]]'s idea that a constant [[force]] produces uniform [[Motion (physics)|motion]], and he instead argued that a force applied continuously produces [[acceleration]], an important concept in [[classical mechanics]].<ref>{{cite encyclopedia | last = [[Shlomo Pines]] | title = Abu'l-Barakāt al-Baghdādī , Hibat Allah | encyclopedia = [[Dictionary of Scientific Biography]] | volume = 1 | pages = 26-28 | publisher = Charles Scribner's Sons | location = New York | date = 1970 | isbn = 0684101149 }} <br> ([[cf.]] Abel B. Franco (October 2003). "Avempace, Projectile Motion, and Impetus Theory", ''Journal of the History of Ideas'' '''64''' (4), p. 521-546 [528].)</ref> He also described acceleration as the rate of change of [[velocity]].<ref>A. C. Crombie, ''Augustine to Galileo 2'', p. 67.</ref> [[Averroes]] (1126–1198) defined and measured [[force]] as "the rate at which [[Mechanical work|work]] is done in changing the [[Kinetic energy|kinetic]] condition of a material [[Physical body|body]]"<ref>Ernest A. Moody (June 1951). "Galileo and Avempace: The Dynamics of the Leaning Tower Experiment (II)", ''Journal of the History of Ideas'' '''12''' (3), p. 375-422 [375].</ref> and correctly argued "that the effect and measure of force is change in the kinetic condition of a materially [[Friction|resistant]] [[mass]]."<ref>Ernest A. Moody (June 1951). "Galileo and Avempace: The Dynamics of the Leaning Tower Experiment (II)", ''Journal of the History of Ideas'' '''12''' (3), p. 375-422 [380].</ref> In the early 16th century, [[al-Birjandi]] developed a hypothesis similar to "circular inertia."<ref name=Ragep>F. Jamil Ragep (2001), "Tusi and Copernicus: The Earth's Motion in Context", ''Science in Context'' '''14''' (1-2), p. 145–163. [[Cambridge University Press]].</ref> The Muslim developments in mechanics laid the foundations for the later development of [[classical mechanics]] in early modern Europe.<ref>Mariam Rozhanskaya and I. S. Levinova (1996), "Statics", p. 642, in {{Harv|Morelon|Rashed|1996|pp=614-642}}: {{quote|"Arabic statics was an essential link in the progress of world 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."}}</ref> ===Medieval Europe=== {{main|History of science in the Middle Ages|History of science in the Renaissance}} Following the collapse of the [[Western Roman Empire]], the knowledge of [[classical antiquity]] was preserved in its monasteries, in the [[Byzantine Empire]], and in the [[Islamic world]].<ref>{{Harvtxt|Burke|2007}}</ref> Works lost in Western Christendom but preserved in the Islamic world led [[cleric]]al scholars such as [[Michael the Scot]] to learn Arabic in order to study them. Their [[Latin translations of the 12th century|translations]] made available to medieval Europe not only the works of the ancients, but also contemporary work. Works both ancient and contemporary also became known in medieval Europe through such points of contact as the [[Republic of Venice]], [[al-Andalus]], and returning [[Crusaders]]. By providing a locus for the exchange of ideas and scholarly collaboration, the birth of the [[medieval university]] was key to the intellectual revitalization of Europe. By the [[13th century]], precursors of the modern [[scientific method]] can be seen on [[Robert Grosseteste]]'s emphasis on [[mathematics]] as a way to understand nature and on the [[empiricism|empirical]] approach admired by [[Roger Bacon]]. Bacon conducted experiments into optics, although much of it was similar to what had been done and was being done at the time by Arab scholars. He did make a major contribution to the development of science in medieval Europe by writing to the [[Pope]] to encourage the study of natural science in university courses and compiling several volumes recording the state of scientific knowledge in many fields at the time. He described the possible construction of a [[telescope]], but there is no strong evidence of his having made one. He recorded the manner in which he conducted his experiments in precise detail so that others could reproduce and independently test his results - a cornerstone of the [[scientific method]], and a continuation of the work of researchers like [[Al Battani]]. In the [[14th century]], some scholars, such as [[Jean Buridan]] and [[Nicole Oresme]], started to question the received wisdom of [[Aristotle]]'s mechanics. In particular, Buridan developed the [[theory of impetus]], which was an important step towards the modern concept of [[inertia]]. In his turn, Oresme showed that the reasons proposed by the physics of Aristotle against the movement of the earth were not valid and adduced the argument of simplicity for the theory that the earth moves, and ''not'' the heavens. In the whole of his argument in favor of the earth's motion Oresme is both more explicit and much clearer than that given two centuries later by [[Copernicus]]. He was also the first to assume that color and light are of the same nature and the discoverer of the curvature of light through [[atmospheric refraction]]; even though, up to now, the credit for this latter achievement has been given to [[Hooke]]. In the 14th century Europe was rocked by the [[Black Death]] which led to much social upheaval. In spite of this pause, the [[15th century]] saw the artistic flourishing of the [[Renaissance]]. The rediscovery of ancient texts was improved when many [[Byzantine Empire|Byzantine]] scholars had to seek refuge in the West after the [[fall of Constantinople]] in [[1453]]. Meanwhile, the invention of [[printing]] was to make learning more accessible and allow a faster propagation of new ideas. All that paved the way to the [[Scientific Revolution]], which may also be understood as a resumption of the process of scientific change halted around the middle of the 14th century. ==Early modern physics== [[Image:Mikolaj Kopernik.jpg|thumb|150px|left|[[Nicolaus Copernicus]] (1473–1543), considered the "[[People known as the father or mother of something|father of modern astronomy]]" <!-- do not enter nationality claims here-->]] {{main|Scientific Revolution}} The [[early modern period]] is seen as a flowering of the [[Renaissance]], in what is often known as the "[[Scientific Revolution]]", viewed as a foundation of [[modern science]]. Historians like Howard Margolis hold that the Scientific Revolution began in [[1543]], when <!-- do not enter nationality claims here-->[[Nicolaus Copernicus]] received the first copy of his ''[[De Revolutionibus Orbium Coelestium|De Revolutionibus]]'', printed in [[Nuremberg]] (Nürnberg) by [[Johannes Petreius]]. Most of its contents had been written years prior, but the publication had been delayed. Copernicus died soon after receiving the copy. [[Image:Galileo.arp.300pix.jpg|thumb|150px|right|[[Galileo Galilei]], considered the "father of modern physics"]] Further significant advances were made over the following century by [[Galileo Galilei]], [[Christiaan Huygens]], [[Johannes Kepler]], and [[Blaise Pascal]]. During the early [[seventeenth century]], Galileo made extensive use of experimentation to validate physical theories, which is the key idea in the modern [[scientific method]]. Galileo formulated and successfully tested several results in [[dynamics (mechanics)|dynamics]], in particular the Law of [[Inertia]]. In Galileo's ''[[Two New Sciences]]'', a dialogue between the characters Simplicio and Salviati discuss the motion of a ship (as a moving frame) and how that ship's cargo is indifferent to its motion. Huygens used the motion of a boat along a Dutch canal to illustrate an early form of the conservation of momentum. [[Image:GodfreyKneller-IsaacNewton-1689.jpg|thumb|150px|left|Sir [[Isaac Newton]], famous for the [[Newton's laws of motion|laws of motion]] and [[Newton's law of universal gravitation|law of gravity]] ]] The scientific revolution is considered to have culminated with the publication of the ''[[Philosophiae Naturalis Principia Mathematica]]'' in [[1687]] by the mathematician, physicist, alchemist and inventor Sir [[Isaac Newton]] ([[1643]]-[[1727]]). In [[1687]], [[Isaac Newton|Newton]] published the ''[[Philosophiae Naturalis Principia Mathematica|Principia]]'', detailing two comprehensive and successful physical theories: [[Newton's laws of motion]], from which arise [[classical mechanics]]; and [[Newton's law of universal gravitation]], which describes the [[fundamental force]] of [[gravity]]. Both theories agreed well with experiment.{{Fact|date=July 2008}} The Principia also included several theories in [[fluid dynamics]]. From the late [[seventeenth century]] onward, [[thermodynamics]] was developed by physicist and chemist [[Robert Boyle|Boyle]], [[Thomas Young (scientist)|Young]], and many others. In [[1733]], [[Daniel Bernoulli|Bernoulli]] used statistical arguments with classical mechanics to derive thermodynamic results, initiating the field of [[statistical mechanics]]. In [[1798]], [[Benjamin Thompson|Thompson]] demonstrated the conversion of mechanical work into heat, and in [[1847]] [[James Joule|Joule]] stated the law of conservation of [[energy]], in the form of heat as well as mechanical energy. [[Ludwig Boltzmann]], in the nineteenth century, is responsible for the modern form of statistical mechanics. Classical mechanics was re-formulated and extended by [[Leonhard Euler]], French mathematician [[Joseph Louis Lagrange|Joseph-Louis Comte de Lagrange]], Irish mathematical physicist [[William Rowan Hamilton]], and others, who produced new results in mathematical physics. The law of universal gravitation initiated the field of [[astrophysics]], which describes [[astronomy|astronomical]] phenomena using physical theories. Newton's Law of gravitation also helped put [[celestial mechanics]] on proper scientific and mathematical footing. After Newton defined [[classical mechanics]], the next great field of inquiry within physics was the nature of [[electricity]]. Observations in the [[seventeenth century|seventeenth]] and [[eighteenth century]] by scientists such as [[Robert Boyle]], [[Stephen Gray (scientist)|Stephen Gray]], and [[Benjamin Franklin]] created a foundation for later work. These observations also established our basic understanding of electrical charge and [[electric current|current]]. By [[1808]] [[John Dalton]] had discovered that atoms of different elements have different weights and proposed the modern [[Atomic theory|theory of the atom]]. It was [[Hans Christian Ørsted]] who first proposed the connection between electricity and magnetism after observing the deflection of a compass needle by a nearby electric current. By the early 1830s [[Michael Faraday]] had demonstrated that magnetic fields and electricity could generate each other. In [[1864]] [[James Clerk Maxwell]] presented to the [[Royal Society]] a set of equations that described this relationship between electricity and magnetism. [[Maxwell's equations]] also predicted correctly that [[light]] is an [[Electromagnetic radiation|electromagnetic wave]]. The Scientific Revolution began in the late 16th century with only a few researchers, and evolved into an enterprise which continues to the present day. Starting with astronomy, the principles of [[natural philosophy]]] crystallized into fundamental [[law of physics|laws of physics]] which were enunciated and improved in the succeeding centuries. By the 19th century, the sciences had segmented into multiple fields with specialized researchers and the field of physics, although logically pre-eminent, no longer could claim sole ownership of the entire field of scientific research. === 16th century === In the [[16th century]] [[Nicolaus Copernicus]] revived [[Aristarchus of Samos|Aristarchus']] [[heliocentric]] model of the [[solar system]] in Europe (which survived primarily in a passing mention in ''[[The Sand Reckoner]]'' of [[Archimedes]]). When this model was published at the end of his life, it was with a preface by [[Andreas Osiander]] that piously represented it as only a mathematical convenience for calculating the positions of planets, and not an account of the true nature of the planetary orbits. In England [[William Gilbert]] (1544-1603) studied [[magnetism]] and [[electricity]], and published a seminal work, ''[[De Magnete]]'' (1600), in which he thoroughly presented his numerous experimental results. [[Gilbert]] who designed the [[versorium]]: a device that detected the presence of statically charged objects. === 17th century === In the early 17th century, the invention of the [[telescope]] and [[microscope]], which is claimed to have been invented by three individuals ([[Hans Lippershey]], [[Jacob Metius]], and [[Zacharias Jansen]]) would have profound implications on the history of [[science]], in particular [[astronomy]] and [[physics]]. In the early [[17th century]] [[Johannes Kepler]] formulated a model of the solar system based upon the five [[Platonic solid]]s, in an attempt to explain why the orbits of the planets had the relative sizes they did. His access to extremely accurate astronomical observations by [[Tycho Brahe]] enabled him to determine that his model was inconsistent with the observed orbits. After a heroic seven-year effort to more accurately model the motion of the planet [[Mars (planet)|Mars]] (during which he laid the foundations of modern [[integral calculus]]) he concluded that the planets follow not circular orbits, but [[ellipse|elliptical]] orbits with the Sun at one focus of the ellipse. This breakthrough overturned a millennium of dogma based on [[Ptolemy]]'s idea of "perfect" circular orbits for the "perfect" heavenly bodies. Kepler then went on to formulate his [[Laws of Kepler|three laws of planetary motion]]. He also proposed the first known model of planetary motion in which a force emanating from the Sun deflects the planets from their "natural" motion, causing them to follow curved orbits. In 1643, [[Evangelista Torricelli]] invented the [[barometer]], which arose from solving an important practical problem. Torricelli discovered [[Torricelli's Law]], regarding the speed of a fluid flowing out of an opening, which was later shown to be a particular case of [[Bernoulli's principle]]. Torecielli also devised an equation sometimes called [[Torricelli's equation]], which is used in the study of [[kinematics]]. In 1660, [[Robert Hooke]], an English scientist, formulated [[Hooke's law]] of [[elasticity (physics)|elasticity]], which describes the linear variation of [[tension]] with extension in an elastic spring. An important device, the [[vernier scale|vernier]], which allows the accurate mechanical measurement of angles and distances was invented by a Frenchman, [[Pierre Vernier]] in [[1631]]. It is in widespread use in scientific laboratories and machine shops to this day. [[Otto von Guericke]] constructed the first air pump in [[1650]] and demonstrated the physics of the vacuum and atmospheric pressure using the [[Magdeburg hemispheres]]. Later, he turned his interests to [[static electricity]], and he invented a mechanical device consisting of a sphere of sulfur that could be turned on a crank and repeatedly charged and discharged to produce electric sparks. In [[1656]] the Dutch physicist and astronomer, [[Christian Huygens]] invented a [[mechanical clock]] using a [[pendulum]] that swung through an elliptical arc, powered by a falling counterweight, to usher in the era of accurate timekeeping. Huygens also formulated Newton's second law of motion, but in quadratic form. Huygens greatest contribution comes from his early theory that light travels in waves ([[Wave–particle duality]]), and for his development of [[Huygens–Fresnel principle]], along with French physicist [[Augustin-Jean Fresnel]]. This mathematical principle provided a method of analysis that could be applied to problems of wave propagation, and it would have applications in the later development of [[quantum mechanics]]. The first quantitative estimate of the [[speed of light]] was made in [[1676]] by [[Ole Rømer]], by timing the motions of Jupiter's satellite [[Io (moon)|Io]] with a telescope. During the early [[17th century]], [[Galileo Galilei]] made extensive use of experimentation to validate physical theories, which is the key idea in the [[scientific method]]. Galileo's use of experiment, and the insistence of Galileo and Kepler that observational results must always take precedence over theoretical results (in which they followed the precepts of [[Aristotle]] if not his practice), brushed away the acceptance of dogma, and gave birth to an era where scientific ideas were openly discussed and rigorously tested. Galileo formulated and successfully tested several results in [[dynamics (mechanics)|dynamics]], including the correct law of accelerated motion, the parabolic trajectory, the relativity of unaccelerated motion, and an early form of the Law of [[Inertia]]. A French mathematician and scientist [[Blaise Pascal]] invented the [[hydraulic press]], and an early [[calculator]]. Pascal also formulated Pascal's law, which states that for all points at the same absolute height in a connected body of an incompressible fluid at rest, the fluid pressure is the same, even if additional pressure is applied on the fluid at some place. Pascal also wrote many important papers on the [[scientific method]]. [[René Descartes]], French mathematician, philosopher, and natural scientist, invented analytic geometry, and discovered the law of conservation of momentum. He outlined his views on the universe in his [[Principles of Philosophy]]. In [[1687]], [[Isaac Newton]] published the ''[[Philosophiae Naturalis Principia Mathematica]],'' detailing two comprehensive and successful physical theories: [[Newton's laws of motion]], from which arise [[classical mechanics]]; and [[gravity|Newton's Law of Gravitation]], which describes the [[fundamental force]] of [[gravity]]. Newton's theory of gravity would be so successful that it would be used by [[William Herschel]] a century later to discover a new planet in the [[solar system]], [[Uranus]]. Both theories agreed well with experiment. The Law of Gravitation initiated the field of [[astrophysics]] and [[celestial mechanics]], which describes [[astronomy|astronomical]] phenomena using physical theories. In the Principia Mathematica Newton also enunciated the principles of [[conservation of momentum]] and the conservation of [[angular momentum]]. Later on in life Newton would move on to formulate the [[law of cooling]] and developed a theory of light based on his experiments with decomposing light through a [[prism (optics)|prism]]. Newton would also invent a [[reflecting telescope]] and along with [[Gottfried Leibniz]] would move on to independently of one another invent [[calculus]], which has many important applications in physics. The 17th century would also witness the beginning of the [[metric system]], which would result in the formation of set of standards for weight and measurements. Early work in developing the metric system were pioneered by [[John Wilkins]], [[Gabriel Mouton]], and [[Antoine Lavoisier]] among others. === 18th century === [[Image:Table of Mechanicks, Cyclopaedia, Volume 2.png|thumb|right|300px|''Table of Mechanicks'', 1728 ''[[Cyclopaedia]]''.]] From the [[18th century]] onwards, [[thermodynamics|thermodynamic]] concepts were developed by [[Robert Boyle]], [[Thomas Young (scientist)|Thomas Young]], and many others, concurrently with the development of the steam engine, onward into the next century.{{Fact|date=February 2007}} In [[1733]], [[Daniel Bernoulli]] used statistical arguments with classical mechanics to derive thermodynamic results, initiating the field of [[statistical mechanics]]. [[Bernoulli]] would also lay the foundation of [[kinetic molecular theory]] in 1738, with the publication of ''Hydrodynamica''. In ''Hydrodynamica'', [[Bernoulli]] would state that all gases consist of [[molecules]] that are constantly in motion, moving in all directions, and impacting on surfaces. It was these movements and impacts that resulted in [[pressure]], and that [[heat]] is the [[kinetic energy]] of these moving molecules. Another pioneer of kinetic molecular theory during the 18th century was [[Mikhail Lomonosov]]. Kinetic molecular theory would have wide ranging applications in physics, in particular [[thermodynamics]], and [[chemistry]]. [[Bernoulli]] would also move on to develop what become known as [[Bernoulli's principle]]. It states that when an [[ideal fluid]] that has no work acting on it, an increase in velocity will result in a simultaneous decrease in [[pressure]] or a change in the fluids [[gravitational potential energy]]. The principle plays a central role in [[fluid dynamics]] and would have considerable impact on the development of [[aerodynamics]] in the 19th and 20th century. During the beginning of the 18th century methods were slowly taking shape in order to provide a standard set of measures to determine [[temperature]]. One set of measure was put forward by [[Anders Celsius]] in [[1742]]. A peculiarity of [[Celsius]] scale was that melting point of an object was set at 0 degrees Celsius and was not until a famous [[botanist]], [[Carl Linnaeus]], would have the scale inverted to read [[boiling point]] being at 100 degrees Celsius. Another method for determining [[temperature]] was put forward by [[Gabriel Fahrenheit]], in [[1724]]. Both methods are named after their respective originators and both are used interchangeably by scientists all over the world to the present date. In [[1746]] an important step in the development of electricity was taken in the invention of the [[Leyden jar]], a capacitor, that could store and discharge electrical charge in a controlled way. In the 18th century many of the fundamental concepts about the nature of electricity were discovered. In 1733, [[C. F. du Fay]], discovered the existence of two types of electricity and named them "vitreous" and "resinous" (later known as positive and negative charge respectively). [[William Watson (scientist)|William Watson]], in 1747 discovered that a discharge of static electricity was equivalent to an electric current. [[Charles Augustin de Coulomb]] formulated [[Coulomb law]], which gives the definition of the electrostatic force of attraction and repulsion. Nearing the 18th century [[André-Marie Ampère]] discovered the relationship that relates the circulating magnetic field in a closed loop to the electric current passing through the loop. [[Carl Friedrich Gauss]] would develop [[Gauss's law]] which is used in the electrostatic application of the generalized [[Gauss's theorem]] giving the equivalence relation between any flux, e.g. of liquids, electric or gravitational, flowing out of any closed surface and the result of inner sources and sinks, such as electric charges or masses enclosed within the closed surface. Nearing the end of the century the relationship that exists between magnetism and electricity continued to described which resulted in the formulation of the fundamental equation of the [[Biot-Savart Law]], which is an equation in electromagnetism that describes the magnetic field vector B in terms of the magnitude and direction of the source electric current, the distance from the source electric current, and the magnetic permeability weighting factor. In the mid 18th century [[Henry Cavendish]] made important discoveries concerning [[electricity]]. Among Cavendish's discoveries were the concept of [[electric potential]], an early unit of [[capacitance]], a formula for the [[capacitance]] of a plate capacitor, concept of the [[dielectric constant]] of a material, and Laws for the division of current in parallel circuits, now attributed to [[Charles Wheatstone]]. Cavendish also devised a method that allowed for the first time in obtaining a numerical value for gravity. Benjamin Thompson]] demonstrated the conversion of unlimited mechanical work into heat.<Ref>Asimov, p. 243</ref> Other pioneers were [[Robert Boyle]], who in 1675 stated that electric attraction and repulsion can act across a vacuum; [[Stephen Gray]], who in 1729 classified materials as conductors and insulators and [[Luigi Galvani]] discovered that muscle and nerve cells produce electricity. [[Benjamin Franklin]] effectively used them (together with von Guericke's generator) in his researches into the nature of [[electricity]] in [[1752]]<Ref>Asimov, p. 178</ref> In about [[1788]], [[Joseph Louis Lagrange]] elaborated an important new formulation of mechanics using the [[calculus of variations]], the [[principle of least action]] and the [[Euler–Lagrange]] equations<ref>Dugas, Ch. 11.</ref> This led to the development of what is called [[Lagrangian mechanics]], which fuses classical mechanics with [[conservation of momentum]] and [[conservation of energy]]. The end of the 18th century would also witness a historic change as profound if not more than the [[agricultural revolution]]. It began with the conversion of steam into mechanical energy, which would ultimately lead to the [[industrial revolution]]. Various steam engines were developed from [[Thomas Newcomen]]'s to [[James Watts]] steam engines. The [[industrial revolution]] is significant in terms of physics because as various [[steam engines]] were being developed there was a greater need to make them more powerful and [[efficient]]. It was this quest to make [[steam engines]] more efficient that would lead to the development of the branch of physics called [[thermodynamics]] ([[History of thermodynamics]]). It is the subsequent discoveries in thermodynamics that led to technological wonders such as the [[internal combustion engine]] and other forms of [[heat engines]], which are used to power [[airplanes]], [[automobiles]], [[locomotives]], and all forms of mobile transport. The 18th century would witness an explosive growth of [[mathematical physics]], which would help formulation of theories that would come about in the 19th and 20th century. The most important work [[mathematical physics]] came from the development of wave equations. These second-order linear [[partial differential equation]] that describes the propagation of a variety of [[wave]]s, such as [[sound]] waves, [[light]] waves and [[water]] waves. They are extensively used fields such as [[acoustics]], [[electromagnetism|electro magnetics]], and [[fluid dynamics]]. These equations were developed and studied by [[Jean le Rond d'Alembert]], [[Leonhard Euler]], [[Daniel Bernoulli]], and [[Joseph-Louis Lagrange]]. ==Modern physics== ===19th century=== In a letter to the [[Royal Society]] in [[1800]], [[Alessandro Volta]] described his invention of the [[Battery (electricity)|electric battery]], thus providing for the first time the means to generate a constant electric current, and opening up a new field of physics for investigation. In announcing his discovery of the pile, Volta paid tribute to the influences of [[William Nicholson (chemist)|William Nicholson]], [[Tiberius Cavallo]] and [[Abraham Bennet]].<ref>*{{ cite journal | author=Elliott, P. | title=Abraham Bennet F.R.S. (1749-1799): a provincial electrician in eighteenth-century England | journal=Notes and Records of the Royal Society of London | volume=53(1) | pages=59–78 | year=1999 | url=http://www.journals.royalsoc.ac.uk/content/klgdd0umcmvjqnpr/fulltext.pdf |format=PDF}} (</ref> Volta also studied what we now call capacitance, developing separate means to study both electrical potential V and charge Q, and discovering that for a given object they are proportional. This may be called Volta's Law of [[Capacitance]], and likely for this work the unit of electrical potential has been named the [[volt]]. The onset of 1800 also witnessed [[William Herschel]]'s discoverey of [[infrared radiation]] by passing [[sunlight]] through a [[triangular prism (optics)|prism]] and holding a [[thermometer]] just beyond the [[red]] end of the [[visible spectrum]]. This thermometer was meant to be a control to measure the ambient air temperature in the room. He was [[serendipity|shocked when it showed a higher temperature]] than the [[visible spectrum]]. Further experimentation led to Herschel's conclusion that there must be an [[visual perception|invisible]] form of [[light]] beyond the [[visible spectrum]]. Some of the most important experiments during the on set of the 19th century were performed by [[Thomas Young]]. [[Young]] would demonstrate the wave nature of [[light]] and finally provide evidence to overturn a long held theory put forward by [[Isaac Newton]] that light consisted of particles. With the ripple tank he demonstrated the idea of [[interference]] in the context of water waves. With the two-slit, or double-slit experiment, he demonstrated interference in the context of light as a [[wave]]. In the [[two-slit experiment]], c. 1801, Young passed a beam of light through two parallel slits in an opaque screen; on the other side was a white screen, where a pattern of alternating light and dark bands formed. This supported Young's contention that light is composed of waves. Young performed and analyzed a number of experiments, including interference of light from reflection off nearby pairs of micrometer grooves, from reflection off thin films of soap and oil, and from Newton's rings. He also performed two important diffraction experiments using fibers and long narrow strips. Within ten years, much of Young's work was reproduced and then extended by [[Fresnel]]. In 1817, Young had proposed a small transverse component to light, while yet retaining a far larger longitudinal component. [[Fresnel]], by the year 1821, was able to show via mathematical methods that polarization could be explained only if light was entirely transverse, with no longitudinal vibration whatsoever. By [[1808]] [[John Dalton]]'s earlier ideas about the existence of [[Atomic mass|atoms of different weights]] and the [[law of multiple proportions]] had led him to the modern [[Atomic theory|theory of the atom]] and many other theories used today in modern physics. The convergence of various estimates of [[Avogadro's number]] lent decisive evidence for atomic theory. In 1807 [[Thomas Young]] described the characterization of [[elasticity]] that came to be known as [[Young's modulus]], denoted as E, in 1807, and further described it in his subsequent works such as his 1845 Course of Lectures on [[Natural Philosophy]] and the Mechanical Arts, which is used to determine the stiffness of a material. In 1804 Young founded the theory of capillary phenomena on the principle of surface [[tension]]. He also observed the constancy of the angle of contact of a liquid surface with a solid, and showed how from these two principles to deduce the phenomena of capillary action. In 1822, [[Claude-Louis Navier]] and [[George Gabriel Stokes]] would publish a series of papers on equations that are central to [[fluid dynamics]] and would later be called [[Navier–Stokes equations]]. These set of equations describe the motion of fluid substances such as [[liquids]] and gasses. The genius of these set of equations comes from their versatility in several varying branches of [[science]]. They can be used to model [[weather]], [[ocean currents]], water flow in pipes, blood flow, flow around an [[airfoil]], motion of [[star]]s inside a [[galaxy]], and when combined with [[Maxwell's equations]] can be used to model [[Magnetohydrodynamics]]. Therefore; [[Navier–Stokes equations]] play a central role design of [[aircraft]], [[cars]], [[power stations]], and used in the analysis of the effects of [[pollution]]. Claude-Louis Navier would move onto to form the general [[theory of elasticity]] in 1821, and would eventually develop the [[elastic modulus]] in 1826. It is for his work on the elastic modulus that Navier is often referred to as the founder of [[structural analysis]]. The [[Coriolis effect]] was discovered by [[Gaspard-Gustave Coriolis]], in 1835. [[Coriolis effect]] is an apparent deflection of moving objects from a straight path when they are viewed from a [[rotating frame of reference]]. The mathematics used by [[Coriolis]] to describe this phenomenon appeared in the [[Theory of tides|tidal equations]] of [[Pierre-Simon Laplace]] in 1778. The effect has a wide varitey of applications in physics but play a particularly important role in [[meteorology]]. [[Image:Carnot2.jpg|150px|right|thumb|'''[[Nicolas Léonard Sadi Carnot|Sadi Carnot]]''']] Although early investigations into a branch of physics called [[thermodynamics]] were done by [[Boyle]], [[Hooke]], and [[Guericke]] among others, the science did not come into its own until the work of a young French physicist and military engineer called [[Sadi Carnot]]. In 1824 [[Carnot]] published the [[Reflections on the Motive Power of Fire]], which is considered the founding paper in [[thermodynamics]]. In this paper Carnot established a general theory of [[heat engines]]. Carnot outlined the principles of what would later become known as the [[Carnot cycle]], the [[Carnot heat engine]], [[Carnot theorem]], and [[thermodynamic efficiency]], to name a few. This monumental work laid the foundations for the [[first law of thermodynamics]] and the [[second law of thermodynamics]]. The behavior of [[electricity]] and [[magnetism]] was studied by [[Michael Faraday]], [[Georg Ohm]], [[Hans Christian Ørsted]], and others. Faraday, who began his career in chemistry working under [[Humphry Davy]] at the Royal Institution, demonstrated that [[electrostatic]] phenomena, the action of the newly discovered electric pile or [[Battery (electricity)|battery]], electrochemical phenomena, and [[lightning]] were all different manifestations of electrical phenomena.<Ref>Asimov, p. 315 ff</ref>. Faraday further discovered in 1821 that electricity can cause rotational mechanical motion, and in 1831 discovered the principle of [[electromagnetic induction]], by which means a moving [[magnet]] induces an [[electrical current]] in a [[Electrical conductor|conductor]]. Thus it was Faraday who laid the foundations for both the [[electric motor]] and the [[electric generator]]<ref name = "pines"/>. Faraday also formulated a physical conception of [[electromagnetic field]]s. Discoveries in electricity and [[magnetism]] would have a profound effect upon society. The principles of electromagnetism find applications in various allied disciplines such as [[microwave]]s, [[Antenna (radio)|antenna]]s, electric machines, [[satellite communication]]s, bioelectromagnetics, [[Plasma (physics)|plasma]]s, [[nuclear physics|nuclear]] research, [[fiber optic]]s, electromagnetic interference and compatibility, electromechanical energy conversion, [[radar]] [[meteorology]], and [[remote sensing]]. Electromagnetic devices include [[transformer]]s, electric [[relay]]s, [[radio]]/[[TV]], [[telephone]]s, [[electric motor]]s, [[transmission line]]s, [[waveguide]]s, [[optical fiber]]s, and [[laser]]s. Classical mechanics was given a new formulation by [[William Rowan Hamilton]] ([[Hamiltonian Mechanics]]), in [[1833]] with the introduction of what is now called the Hamiltonian, which a century later gave an entry to wave mechanical formulation of quantum mechanics. During its first [[1868]] meeting, notable [[oceanographer]] [[Matthew F. Maury]] helped launch the [[American Association for the Advancement of Science]] (AAAS) by giving a very influential lecture on Wind and Current Charts which gave rise to one of the first examples of international scientific collaboration.<ref>Hearn, Chester G. ''Tracks in the Sea: Matthew Fontaine Maury and the Mapping of the Oceans'' McGraw-Hill (2002) p 127, ISBN 0-07-136826-4</ref> [[Image:James Clerk Maxwell.png|thumb|left|150px|[[James Clerk Maxwell]]]] [[James Clerk Maxwell]] built upon [[Michael Faraday]]'s physical conception of [[electromagnetic fields]] with an interlinked set of twenty equations that explained the interactions between [[electric field|electric]] and [[magnetic field]]s and unified the two phenomena into a single theory of [[electromagnetism]]. [[Maxwell's equations]] were presented to the [[Royal Society]] in [[1864]]. These twenty equations were later reduced, using [[vector calculus]], to a set of four equations by [[Oliver Heaviside]]. A prediction of [[Maxwell's equations]] was that [[light]] is an [[electromagnetic radiation|electromagnetic wave]]. Confirmation of Maxwell's insight into electromagnetism was made with the observation, in [[1888]], and the discovery of [[radio]] by [[Heinrich Hertz]] and in [[1895]] when [[Wilhelm Roentgen]] detected [[X-ray]]s. Aside from Maxwell's work in the electromagnetism, he would also make important contributions to thermodynamics through a set of equations called [[Maxwell Relations]], which provide an experimental way in which to measure [[entropy]]. Maxwell along with [[Ludwig Boltzmann]] would establish [[Maxwell–Boltzmann]], which is a [[probability distribution]] for molecular speeds in a gas. In 1842, an [[Austrian]] [[scientist]] by the name of [[Christian Doppler]] would publish a paper on what would become known as the [[Doppler effect]]. The summation of his work was an equation which described a change in [[frequency]] and [[wavelength]] of a [[wave]] as perceived by an observer moving relative to the source of the waves. In 1848, [[John Scott Russell]] conducted a series of experiments to verify some of the conclusions of the [[Doppler effect]]. The equation has applications has applications in [[astronomy]], temperature measurement, [[radar]], [[medical imaging]], flow measurement, and underwater [[acoustics]]. Building upon the work of physicists before him a young German physicist by the name of [[Gustav Kirchhoff]], while still a student in 1845, would formulate [[Kirchhoff's circuit laws]], which are now used in all of [[electrical engineering]]. In 1859 Kirchoff would proceed to explain what became known as [[Kirchoff's law of thermal radiation]], which provided a general statement about [[emission]] and [[absorption]] in heated objects. Later on in his career Kirchoff would work with [[Robert Bunsen]] to establish the field of [[spectroscopy]], specifically through their formulation of Kirchoff's three laws of spectroscopy. In [[1847]] [[James Prescott Joule]] stated the law of conservation of [[energy]], in the form of heat as well as mechanical energy. However, the principle of conservation of energy had been suggested in various forms by perhaps a dozen German, French, British and other scientists during the first half of the 19th century.{{Fact|date=February 2007}} About the same time, [[entropy]] and the second law of thermodynamics were first clearly described in the work of [[Rudolf Clausius]]. In 1875 [[Ludwig Boltzmann]] made the important connection between the number of possible states that a system could occupy and its entropy. With two installments in 1876 and 1878, [[Willard Gibbs|Josiah Willard Gibbs]] developed much of the theoretical formalism for [[thermodynamics]], and a decade later firmly laid the foundation for [[statistical mechanics]] &mdash; much of which [[Ludwig Boltzmann]] had independently invented. In [[1881]] Gibbs also was very influential in moving much of the notation of physics from Hamilton's [[quaternions]] to [[vector (spatial)|vectors]].<ref>J. W.Gibbs ''Nature'' '''48,''' 364 (1893).</ref><ref>J. W.Gibbs. ''The Scientific Papers of J. Willard Gibbs, Vol. Two,'' Oxbow Press (1994) ISBN 0-881987-06-x</ref> From 1873-76 Gibbs would help to apply thermodynamics to chemical processes, thus laying the foundations of [[chemical thermodynamics]]. Gibbs would publish 3 papers, the most famous being titled [[On the Equilibrium of Heterogeneous Substances]] in which he demonstrated that thermodynamic processes could be graphically analyzed, by studying the [[energy]], [[entropy]], [[volume]], [[temperature]] and [[pressure]] of the thermodynamic system, in such a manner to determine if a process would occur spontaneously. The first and second laws of thermodynamics emerged in the 1850s, primarily out of the works of [[William Rankine]], [[Rudolf Clausius]], and [[William Thomson]]. The [[third law of thermodynamics]], which was established by [[Ludwig Boltzmann]], states that the [[entropy]] of a pure substance approaches zero as the absolute temperature approaches zero. The discovery of the [[Hall effect]] in [[1879]] gave the first direct evidence that the carrier of electricity was negatively charged.{{Fact|date=February 2007}} In 1879, [[Sir William Crookes]] would discover a new form of matter which he called "radiant matter". What Crookes has discovered was what became known as [[plasma]], the most abundant state of matter in the universe. Crookes was able to make his discovery of plasma by inventing the [[Crookes tube]]. The discovery of [[plasma]] is important because it constitutes the first time since a new state of matter had been discovered, aside from common knowledge of solids, liquids, and gases. Secondly, further research into plasma demonstrated its importance not only to science but also many technological applications such as [[plasma displays]], [[fusion energy]] research, and production of [[integrated circuits]] to name a few. [[Dimensional analysis]] was used for the first time in 1878 by [[Lord Rayleigh]] who was trying to understand why the [[Diffuse sky radiation|sky is blue]].<ref>Lord Rayleigh. ''Phil. Mag.'' '''41''', 107 (1871).</ref> In [[1887]] the [[Michelson-Morley experiment]] was conducted and it was interpreted as counter to the generally held theory of the day, that the [[Earth]] was moving through a "[[luminiferous aether]]".{{Fact|date=February 2007}} [[Albert Abraham Michelson]] and [[Edward Morley]] were not fully convinced of the non-existence of the aether. Morley conducted further experiments with [[Dayton Miller]] with improved interferometers, again giving null results.{{Fact|date=February 2007}} [[Image:Marie Curie (Nobel-physics).png|thumb|right|150px|[[Marie Sklodowska-Curie]]]] In [[1887]], [[Nikola Tesla]] investigated [[X-ray]]s using his own devices as well as Crookes tubes. In [[1895]], [[Wilhelm Conrad Röntgen]] observed and analysed X-rays, which turned out to be high-frequency [[electromagnetic radiation]]. [[Radioactivity]] was discovered in [[1896]] by [[Henri Becquerel]], and further studied by [[Pierre Curie|Pierre]] and [[Maria Sklodowska-Curie|Marie Curie]] and others. This initiated the field of [[nuclear physics]]. In the late 19th century [[Johannes Diderik van der Waals]] would postulate the existence of forces which act between molecules, but are weak compared to those in [[chemical bonds]]. These forces would later be named [[Van der Waals]] forces. A German physict by the name of [[Fritz London]] would also discover similar forces which Waals had first proposed. [[Van der Waals]] forces occupy an important role in [[thermodynamics]] and [[chemistry]]. In [[1897]], [[J. J. Thomson]] deduced that [[cathode ray tube|cathode rays]] were composed of negatively charged particles, which he called "''corpuscles''", later realized to be [[electron]]s. [[Philipp Lenard]] showed that the particles ejected in the [[photoelectric effect]] were the same as those in cathode rays, and that their energy was independent of the intensity of the light, but was greater for short wavelengths of the incident light.<ref>{{cite web |url=http://nobelprize.org/nobel_prizes/physics/laureates/1905/lenard-bio.html |title=Biography|accessdate=2007-02-23 }} Lenard's Nobel biography.</ref> These discoveries revealed that the assumption of many physicists, that atoms were the basic unit of [[matter]], was flawed, and prompted further study into the structure of [[atom]]s, such as [[Ernest Rutherford]]'s in 1911. ===20th century=== [[Image:Einstein patentoffice.jpg|thumb|right|150px|[[Albert Einstein]]]] The turn of the [[20th century]] brought the start of a [[revolution]] in physics. This revolution centered around the advent on [[quantum mechanics]] and special and [[general relativity]], the two concepts that mark the advent of [[physics|modern physics]]. Both of these theories would offer fundamental insights into the universe and the laws the govern it. [[Quantum mechanics]] would describe the microscopic nature of matter, while relativity would describe [[space]] and [[time]]. In [[thermodynamics]], [[zeroth law of thermodynamics]], which is a generalized statement about bodies in contact at thermal equilibrium and is the basis for the concept of temperature was formalized, although the principles behind the law were well known in the 19th century, was not until the 20th century that the law finally incorporated into thermodynamics. In 1929, [[Lars Onsager]], would establish [[Onsager reciprocal relations]]-sometimes referred to as the fourth law of thermodynamics. The [[Lorentz transformations]], the fundamental equations of special relativity, were published in 1897 and 1900 and also by [[Joseph Larmor]] and by [[Hendrik Lorentz]] in 1899 and 1904. They both showed that Maxwell's equations were invariant under the transformations. The ability to describe light in electromagnetic terms helped serve as a springboard for [[Albert Einstein]]'s publication of the theory of [[special relativity]] in 1905. This theory combined classical mechanics with Maxwell's equations. The theory of [[special relativity]] unifies space and time into a single entity, [[spacetime]]. Relativity prescribes a different transformation between [[inertial frame of reference|reference frames]] than classical mechanics; this necessitated the development of relativistic mechanics as a replacement for classical mechanics. In the regime of low (relative) velocities, the two theories agree. In [[1900]], [[Max Planck]] published his explanation of [[blackbody radiation]]. This equation assumed that radiators are [[quantum|quantized]], which proved to be the opening argument in the edifice that would become [[quantum mechanics]]. By introducing discrete energy levels, Planck, Einstein, [[Niels Bohr]], and others developed [[quantum]] theories to explain other anomalous experimental results like the [[photoelectric effect]]. The discovery of [[quantum mechanics]] in the early 20th century revolutionized physics, and quantum mechanics is fundamental to most areas of current research. In [[1904]], [[J. J. Thomson]] proposed the first model of the [[atom]], known as the [[atom/plum pudding|plum pudding model]]. In [[1911]], [[Ernest Rutherford]] deduced from [[Rutherford scattering|scattering experiments]] the existence of a compact [[atomic nucleus]], with positively charged constituents dubbed [[proton]]s. The first quantum mechanical model of the atom, the [[Bohr model]], was published in 1913 by [[Niels Bohr]]. Sir [[W. H. Bragg]] and his son Sir [[William Lawrence Bragg]], also in 1913, began to unravel the arrangement of atoms in crystalline matter by the use of [[x-ray diffraction]]. [[Neutron]]s, the neutral nuclear constituents, were discovered in [[1932]] by [[James Chadwick]]. One of the most important concepts in modern physics and one which would help usher in [[quantum mechanics]] was proposed by [[Louis de Broglie]]. Broglie's 1922 doctoral thesis, ''Recherches sur la théorie des quanta'' (Research on Quantum Theory), introduced his theory of electron waves. This included the [[wave-particle duality]] theory of matter, based on the work of [[Albert Einstein]] and [[Planck]]. This research culminated in the [[de Broglie hypothesis]] stating that ''any moving particle or object had an associated wave''. De Broglie thus created a new field in physics, the ''mécanique ondulatoire,'' or wave mechanics, uniting the physics of light and matter. Among the applications of this work has been the development of [[electron microscope]]s to get much better image resolution than optical ones, because of shorter wavelengths of electrons compared with [[photons|photon]]. [[Image:Ernest Rutherford.jpg|thumb|left|150px|[[Ernest Rutherford]]]] In [[1911]], [[Ernest Rutherford]] deduced from [[Rutherford scattering|scattering experiments]] the existence of a compact atomic nucleus, with positively charged constituents dubbed [[proton]]s. Rutheford along with [[Frederick Soddy]] would also achieve the first case of [[Nuclear transmutation]], a phenomenon, which had been speculated since the time of the Greeks. Rutheford and Soddy noticed they has achieved this when during their experiments in 1901 radioactive [[thorium]] was converting itself into radium. [[Neutron]]s, the neutral nuclear constituents, were discovered in [[1932]] by [[James Chadwick|Chadwick]]. The equivalence of mass and energy (Einstein, 1905) was spectacularly demonstrated during [[World War II]], as research was conducted by each side into [[nuclear physics]], for the purpose of creating a [[nuclear weapon|nuclear bomb]]. The German effort, led by Heisenberg, did not succeed, but the Allied [[Manhattan Project]] reached its goal. In America, a team led by [[Enrico Fermi|Fermi]] achieved the first man-made [[nuclear chain reaction]] in [[1942]], and in [[1945]] the world's first [[nuclear weapon|nuclear explosive]] was detonated at [[Trinity site]], near [[Alamogordo]], [[New Mexico]]. In [[1915]], Einstein extended special relativity to describe gravity with the [[general relativity|general theory of relativity]]. One principal result of general relativity is the [[gravitational collapse]] into [[black holes]], which was anticipated two centuries earlier, but elucidated by [[Robert Oppenheimer]]. Important exact solutions of [[Einstein's field equation]] were found by [[Karl Schwarzschild]] in 1915 and [[Roy Kerr]] only in 1963. One part of the theory of general relativity is [[Einstein's field equation]]. This describes how the ''stress-energy tensor'' creates curvature of [[spacetime]] and forms the basis of general relativity. Further work on Einstein's field equation produced results which predicted the [[Big Bang]], [[black hole]]s, and the [[expanding universe]]. Einstein believed in a static universe. He tried, and failed, to fix his equation to allow for this. In [[1929]], however, [[Edwin Hubble]] published his discovery that that the universe is expanding at a possibly exponential rate. This is the basis for understanding that the [[universe]] is expanding. Thus, the universe must have been smaller and therefore hotter in the past. In [[1933]] [[Karl Jansky]] at Bell Labs discovered the radio emission from the [[Milky Way]], and thereby initiated the science of [[radio astronomy]]. By the [[1940]]s, researchers like [[George Gamow]] proposed the ''[[Big Bang]]'' theory,<ref>Alpher, Herman, and Gamow. ''Nature'' '''162''', 774 (1948).</ref> evidence for which was discovered in [[1964]];<ref>{{cite web|last=Wilson |first=Robert W. |authorlink=Robert Woodrow Wilson|date=1978 |url=http://nobelprize.org/physics/laureates/1978/wilson-lecture.pdf |title=The cosmic microwave background radiation |format=PDF |accessdate=2006-06-07 }} Wilson's Nobel Lecture.</ref> [[Enrico Fermi]] and [[Fred Hoyle]] were among the doubters in the 1940s and 1950s. Hoyle had dubbed Gamow's theory the ''Big Bang'' in order to debunk it. Today, it is one of the principal results of [[physical cosmology|cosmology]]. According to [[Cornelius Lanczos]], any [[physical law]] which can be expressed as a [[variational principle]] describes an expression which is [[self-adjoint]]<ref>{{cite book | last = Lanczos | first = Cornelius | title = The Variational Principles of Mechanics | year = 1986 | publisher = Dover Publication | location = New York | id = ISBN 0-486-65067-7 }}</ref> or [[Hermitian]]. Thus such an expression describes an [[invariant]] under a Hermitian transformation. [[Felix Klein]]'s [[Erlangen program]] attempted to identify such invariants under a group of transformations. [[Noether's theorem]] identified the conditions under which the [[Poincaré group]] of transformations (what is now called a [[gauge group]]) for [[general relativity]] define [[conservation law]]s. The relationship of these invariants (the symmetries under a group of transformations) and what are now called conserved currents, depends on a variational principle, or [[Action (physics)|action principle]]. Noether's papers made the requirements for the conservation laws precise. Noether's theorem remains right in line with current developments in physics to this day. [[Image:Erwin Schrödinger.jpg|thumb|150px|right|[[Erwin Schrödinger]]]] In [[1925]] [[Wolfgang Pauli]] elucidated the [[Pauli exclusion principle]] and introduced the notion of quantized [[Spin (physics)|spin]] and [[fermions]]. Over the next several years, quantum mechanics would be formulated by [[Werner Heisenberg]], Erwin Schrödinger and [[Paul Dirac]] in different ways which both explained the preceding heuristic quantum theories. In quantum mechanics, the outcomes of physical measurements are inherently [[probability|probabilistic]]; the theory describes the calculation of these probabilities. It successfully describes the behavior of matter at small distance scales. In 1925 [[Erwin Schrödinger|Schrödinger]] formulated [[wave mechanics]], which provided a consistent mathematical method for describing a wide variety of physical situations such as the [[particle in a box]] and the [[quantum harmonic oscillator]] which he solved for the first time. That same year [[Werner Heisenberg|Heisenberg]] described an alternative mathematical method, called [[matrix mechanics]], which proved to be equivalent to wave mechanics. In [[1928]] [[Paul Dirac|Dirac]] produced a relativistic formulation built on Heisenberg's matrix mechanics, and predicted the existence of the [[positron]] and founded [[quantum electrodynamics]]. During the [[1920s]] Schrödinger, Heisenberg, and [[Max Born]] were able to formulate a consistent picture of the chemical behavior of matter, a complete theory of the electronic structure of the atom, as a byproduct of the quantum theory. Quantum mechanics also provided the theoretical tools for [[condensed matter physics]], whose largest branch is [[solid state physics]]. It studies the physical behavior of solids and liquids, including phenomena such as [[crystal structure]]s, [[semiconductor|semiconductivity]], and [[superconductor|superconductivity]]. The pioneers of condensed matter physics include [[Felix Bloch]], who created a quantum mechanical description of the behavior of electrons in crystal structures in [[1928]]. Much of the behavior of solids was elucidated within a few years with the discovery of the [[Fermi surface]] which was based on the idea of the Pauli exclusion principle applied to systems having many electrons. The understanding of the transport properties in [[semiconductors]] as described in [[William Shockley]]'s ''Electrons and holes in semiconductors, with applications to transistor electronics'' enabled the electronic revolution of the twentieth century through the development of the ubiquitous, ultra-cheap [[transistor]]. The transistor was developed by physicists [[John Bardeen]], [[Walter Houser Brattain]], and [[William Bradford Shockley]] in [[1947]] at [[Bell Labs|Bell Laboratories]]. The transistor is a semiconductor device that can be used to amplify or switch electronic signals. The transistor is the fundamental building block of computers, and all other [[electronics|modern electronic devices]]. The invention of the transistor and the [[integrated circuit]] would usher in the [[electronics|electronics age]] and the subsequent [[information revolution]]. During the early stages of [[particle physics]], physicists noticed a type of [[radioactive decay]] that occurred in the [[atomic nucleus]], which gave of [[alpha particles]] that consisted of two [[protons]] and [[neutrons]] in a particle that resembled the helium nucleus. The phenomenon would be called [[alpha decay]]. In 1928, [[George Gamow]] used the concept of [[quantum tunneling]], formulated earlier in [[quantum mechanics]], to successfully explain [[alpha decay]]. [[Quantum tunneling]] states there is a process by which a particles can penetrate a potential barrier that has a higher [[kinetic energy]] then the particle itself. The principle of quantum tunneling would have important implications for all of particle physics, and as time passed would have practical technological applications. In [[1934]], the Italian physicist [[Enrico Fermi]] had discovered strange results when bombarding [[uranium]] with [[neutron]]s, which he believed at first to have created [[transuranic]] elements. In [[1939]], it was discovered by the chemist [[Otto Hahn]] and the physicist [[Lise Meitner]] that what was actually happening was the process of [[nuclear fission]], whereby the nucleus of uranium was actually being split into two pieces, releasing a considerable amount of energy in the process. At this point it became clear to a number of scientists independently that this process could potentially be harnessed to produce massive amount of energy, either as a civilian power source or as a weapon. [[Leó Szilárd]] actually filed a patent on the idea of a [[nuclear chain reaction]] in 1934. In America, a team led by Fermi and Szilárd achieved the first man-made nuclear chain reaction in [[1942]] in the world's first [[nuclear reactor]], and in [[1945]] the world's first nuclear explosive was detonated at [[Trinity test|Trinity Site]], north of [[Alamogordo, New Mexico]]. After the war, central governments would become the primary sponsors of physics. The scientific leader of the Allied project, theoretical physicist [[Robert Oppenheimer]], noted the change of the imagined role of the physicist when he noted in a speech that: :"''In some sort of crude sense, which no vulgarity, no humor, no overstatement can quite extinguish, the physicists have known sin, and this is a knowledge which they cannot lose.''" Though the process had begun with the invention of the [[cyclotron]] by [[Ernest O. Lawrence]] in the 1930s, nuclear physics in the postwar period entered into a phase of what historians have called "[[Big Science]]", requiring costly huge accelerators and particle detectors, and large collaborative laboratories to test open new frontiers. The primary patron of physics became central governments, who recognized that the support of "basic" research could sometimes lead to technologies useful to both military and industrial applications. Toward the end of the twentieth century, a European collaboration of 20 nations, [[CERN]], became the largest particle physics laboratory in the world. Another "big science" was the science of ionized gases, [[Plasma (physics)|plasma]], which had begun with Crookes tubes late in the 19th century. Large international collaborations over the last half of the twentieth century embarked on a long range effort to produce commercial amounts of electricity through [[fusion power]], which remains a distant goal. Further understanding of the physics of metals, semiconductors and insulators led a team of three men at Bell labs, [[William Shockley]], [[Walter Brattain]] and [[John Bardeen]] in [[1947]] to the first [[transistor]] and then to many important variations, especially the [[bipolar junction transistor]]. Further developments in the fabrication and miniaturization of [[integrated circuits]] in the years to come produced fast, compact computers that came to revolutionize the way physics was done&mdash;simulations and complex mathematical calculations became possible that were undreamed of even a few decades previous. The discovery of [[nuclear magnetic resonance]] in [[1946]] led to many new methods for examining the structures of molecules and became a very widely used tool in analytical chemistry, and it gave rise to an important medical imaging technique, [[magnetic resonance imaging]]. <!-- Image with unknown copyright status removed: [[Image:Feynman-bongos.jpg|thumb|right|150px|[[Richard Feynman]]]] --> [[Quantum field theory]] was formulated in order to extend quantum mechanics to be consistent with special relativity, and was developed in the late 1940s in the work of [[Richard Feynman]], [[Julian Schwinger]], [[Sin-Itiro Tomonaga]], and [[Freeman Dyson]]. They formulated the theory of [[quantum electrodynamics]], which describes the electromagnetic interaction, and successfully explained the [[Lamb shift]]. This provided the framework for modern [[particle physics]], which studies [[fundamental force]]s and [[elementary particles]]. [[Chen Ning Yang]] and [[Tsung-Dao Lee]], in the [[1950s]], discovered an unexpected [[asymmetry]] in the decay of a [[subatomic particle]]. In [[1954]], Yang and [[Robert Mills (physicist)|Robert Mills]] then developed a class of [[gauge theory|gauge theories]] which provided the framework for understanding the nuclear forces (Yang, Mills 1954). The theory for the [[strong nuclear force]] was first proposed by [[Murray Gell-Mann]]. The [[electroweak force]], the unification of the [[weak nuclear force]] with electromagnetism, was proposed by [[Sheldon Lee Glashow]], [[Abdus Salam]], and [[Steven Weinberg]] and confirmed in [[1964]] by [[James Watson Cronin]] and [[Val Fitch]]. This led to the so-called [[Standard Model]] of particle physics in the [[1970s]], which successfully describes all the elementary particles observed to date. The invention of bubble chambers and spark chambers in the 1950s allowed physicists to discover large amounts of particles called [[hadrons]] ([[Timeline of particle discoveries]]). There needed to exist some way of classifying these sub-atomic particles and how they interact with the fundamental forces in nature. This led physicists such as [[Gell-Mann]], [[George Zweig]], and others to development of [[Quantum chromodynamics]], which describes the interaction between [[quarks]] and [[gluons]] found in [[hadrons]]. Two interesting properties of this theory are [[asymptotic freedom]], and [[confinement]]. Asymptotic freedom was later discovered in 1973 by [[David Politzer]], [[Frank Wilczek]], and [[David Gross]]. Starting in [[1960]] the military establishment of the United States began using [[atomic clocks]] to construct the [[global positioning system]] which in [[1984]] achieved its full configuration of 24 satellites in low earth orbits. This came to have many important civilian and scientific uses as well. Investigations into [[quantum electronics]] by [[Charles Hard Townes]], [[Nikolay Basov]], [[Aleksandr Prokhorov]], and [[Theodore Maiman]]in 1960's resulted in the development of [[lasers]]. When lasers were invented, they were called "a solution looking for a problem".[20] Since then, they have become ubiquitous, finding utility in thousands of highly varied applications in every section of modern society, including consumer [[electronics]], [[information technology]], [[science]], [[medicine]], [[industry]], law enforcement, [[entertainment]], and the [[military]]. [[Superconductivity]], discovered in 1911 by [[Kamerlingh Onnes]], was shown to be a quantum effect and was satisfactorily explained in 1957 by [[John Bardeen|Bardeen]], [[Leon Neil Cooper|Cooper]], and [[John Robert Schrieffer|Schrieffer]]. A family of [[High-temperature superconductivity|high temperature superconductors]], based on cuprate perovskite, were discovered in 1986, and their understanding remains one of the major outstanding challenges for condensed matter theorists. In [[1974]] [[Stephen Hawking]] discovered the [[Hawking radiation|spectrum of radiation]] emanating during the collapse of matter into [[black hole]]s. These mysterious objects became of intense interest to astrophysicists and even the general public in the latter part of the twentieth century. The concept of [[quantum tunneling]] would be used to create a [[Scanning tunneling microscope]] in 1981 by [[Gerd Binnig]] and [[Heinrich Rohrer]]. The invention of the [[atomic force microscope]] (AFM) [[Scanning Tunneling Microscope]] (STM) are two early versions of scanning probes that launched [[nanotechnology]]. [[Scanning probe microscopy]] is an important technique both for characterization and synthesis of nanomaterials. [[Atomic force microscope]]s and [[scanning tunneling microscope]]s can be used to look at surfaces and to move atoms around. By designing different tips for these microscopes, they can be used for carving out structures on surfaces and to help guide self-assembling structures. By using, for example, [[feature-oriented scanning]]-[[Feature-oriented positioning|positioning]] approach, atoms can be moved around on a surface with scanning probe microscopy techniques. At present, it is expensive and time-consuming for mass production but very suitable for laboratory experimentation. The independent discovery of a [[quantum mechanical]] effect,[[giant magnetoresistance]], in 1988 by [[Albert Fert]] and [[Peter Grünberg]] is considered as the birth of [[spintronics]]. The effect manifests itself as a significant decrease in [[electrical resistance]] in the presence of a magnetic field. In the [[Zero-point field|absence of an applied magnetic field]] the direction of [[magnetization]] of adjacent [[ferromagnetic]] layers is [[Antiparallel (electronics)|antiparallel]] due to a weak anti-ferromagnetic [[Coupling (physics)|coupling]] between layers, and it decreases to a lower level of resistance when the magnetization of the adjacent layers align due to an applied external field. The [[spin (physics)|spin]]s of the [[electrons]] of the nonmagnetic metal align parallel or antiparallel with an applied magnetic field in equal numbers, and therefore suffer less magnetic [[scattering]] when the magnetizations of the ferromagnetic layers are parallel. The effect is exploited commercially by manufacturers of [[hard disk drive]]s. The two themes of the [[twentieth century]], general relativity and quantum mechanics, appear inconsistent with each other. General relativity describes the [[universe]] on the scale of [[planet]]s and [[solar system]]s, while quantum mechanics operates on sub-atomic scales. This challenge is being attacked by [[string theory]], which treats [[spacetime]] as composed, not of points, but of one-dimensional objects, [[string theory|strings]]. Strings have properties similar to a common string (e.g., [[Tension (mechanics)|tension]] and [[oscillation|vibration]]). The theories yield promising, but not yet testable, results. The search for experimental verification of string theory is in progress. Attempts to unify quantum mechanics and general relativity made significant progress during the 1990s. At the close of the century, a [[Theory of everything]] was still not in hand, but some of its characteristics were taking shape. [[String theory]], [[loop quantum gravity]] and [[black hole thermodynamics]] all predicted [[quantized]] [[spacetime]] on the [[Planck scale]]. A number of new efforts to understand the physical world arose in the last half of the twentieth century that generated widespread interest: [[fractals]] and [[scaling]], [[self-organized criticality]], [[complexity]] and [[chaos]], [[power laws]] and [[noise]], [[Telecommunications network|networks]], [[non-equilibrium thermodynamics]], [[Bak-Tang-Wiesenfeld sandpile|sandpiles]], [[nanotechnology]], [[cellular automata]] and the [[anthropic principle]] were only a few of these important topics. === Future directions === [[Image:WYP2005 logo.gif|right|130px|The [[United Nations]] declared the year [[2005]], the centenary of Einstein's [[Annus Mirabilis Papers|annus mirabilis]], as the [[World Year of Physics]].]] {{main|Unsolved problems in physics}} Research in physics is progressing constantly on a large number of fronts, and is likely to do so for the foreseeable future. In condensed matter physics, the greatest unsolved theoretical problem is the explanation for [[high-temperature superconductivity]]. Strong efforts, largely experimental, are being put into making workable [[spintronics]] and [[quantum computer]]s. In particle physics, the first pieces of experimental evidence for physics beyond the [[Standard Model]] have begun to appear. Foremost amongst these are indications that [[neutrino]]s have non-zero [[mass]]. These experimental results appear to have solved the long-standing [[solar neutrino problem]] in solar physics. The physics of massive neutrinos is currently an area of active theoretical and experimental research. In the next several years, [[particle accelerator]]s will begin probing energy scales in the [[TeV]] range, in which experimentalists are hoping to find evidence for the [[Higgs boson]] and [[supersymmetry|supersymmetric particles]]. [[Image:First Gold Beam-Beam Collision Events at RHIC at 100 100 GeV c per beam recorded by STAR.jpg|thumb|right|300px|Thousands of particles explode from the collision point of two relativistic (100 [[GeV]] per ion) [[gold]] ions in the [[STAR detector]] of the [[Relativistic Heavy Ion Collider]]; an experiment done in order to investigate the properties of a [[quark gluon plasma]] such as the one thought to exist in the ultrahot first few microseconds after the [[big bang]]]] Theoretical attempts to unify [[quantum mechanics]] and [[general relativity]] into a single theory of [[quantum gravity]], a program ongoing for over half a century, have not yet borne fruit. Currently, the leading candidates are [[M-theory]], [[superstring theory]], and [[loop quantum gravity]]. Many [[astronomy|astronomical]] and [[physical cosmology|cosmological]] phenomena have yet to be explained satisfactorily, including the existence of [[GZK paradox|ultra-high energy cosmic rays]], the [[baryon asymmetry]], the nature of non-baryonic [[dark matter]], and the [[accelerating universe|acceleration of the universe]]. Although much progress has been made in high-energy, [[quantum]], and astronomical physics, many everyday phenomena, involving [[complex systems|complexity]], [[chaos]], or [[turbulence]] remain poorly understood. Complex problems that would appear to be soluble by a clever application of dynamics and mechanics, such as the formation of sand piles, nodes in trickling [[water]], the shape of water [[droplet]]s, mechanisms of [[surface tension]] [[catastrophe theory|catastrophes]], or self-sorting in shaken heterogeneous collections are unsolved. These complex phenomena have received growing attention since the 1970s for several reasons, not least of which has been the availability of modern [[mathematics|mathematical]] methods and [[computers]], which enabled [[complex systems]] to be modeled in new ways. The [[interdisciplinary]] [[relevance]] of complex physics also has increased, as exemplified by the study of [[turbulence]] in [[aerodynamics]], or the [[observation]] of [[pattern formation]] in [[biology|biological]] systems. In 1932, [[Horace Lamb]] correctly prophesied the success of the theory of quantum electrodynamics and the near-stagnant progress in the study of turbulence: <blockquote> ''"I am an old man now, and when I die and go to heaven there are two matters on which I hope for enlightenment. One is quantum electrodynamics, and the other is the turbulent motion of fluids. And about the former I am rather optimistic."'' </blockquote> ==Notes== {{reflist}} ==References== * Asimov, Isaac ''Asimov's Biographical Encyclopedia of Science and Technology: The Lives & Achievements of 1510 Great Scientists from Ancient Times to the Present'' Revised second edition, Doubleday (1982) ISBN 0-385-17771-2. * {{Citation | last=Burke | first=James | author-link=James Burke (science historian) | year= | publication-date=2007 | title=Connections | edition= | place= | publication-place= | publisher=Simon & Schuster}}. * Byers, Nina, "E. Noether's Discovery of the Deep Connection Between Symmetries and Conservation Laws," ''Israel Mathematical Conference Proceedings'', vol. 12, 1999[http://www.physics.ucla.edu/~cwp/articles/noether.asg/noether.html] * Dugas, René, ''A History of Mechanics'' Dover, (1988) ISBN 0-486-65632-2 * {{Citation | last=Evans | first=James | author-link= | year=1998 | title=The History and Practice of Ancient Astronomy | publisher=Oxford University Press | isbn =0195095391}}. * Motz, Lloyd and Waver, Jefferson Hane ''The Story of Physics,'' Plenum (1989) ISBN 0-306-43076-2. * {{Citation | last=Needham | first=Joseph | author-link=Joseph Needham | year=1986 | title=Science & Civilisation in China | publisher=Cambridge University Press | volume=IV:1: ''Physics and Physical Technology''}}. * {{Citation | last=Needham | first=Joseph | author-link=Joseph Needham | year=2000 | title=Science & Civilisation in China | publisher=Cambridge University Press | volume=IV:2: ''Mechanical Engineering''}}. * {{Citation | last=Newton | first=Roger G. | author-link= | year=2007 | title=From Clockwork to Crapshoot: A History of Physics | publisher=Harvard University Press | isbn =}}. * {{Citation | last=Pingree | first=David | author-link=David Pingree | year=1998 | contribution=Legacies in Astronomy and Celestial Omens | editor-last=Dalley | editor-first=Stephanie | editor-link= | title=The Legacy of Mesopotamia | publisher=Oxford University Press | pages=pp. 125–137 | isbn =0198149468}}. * {{Citation |last1=Morelon |first1=Régis |last2=Rashed |first2=Roshdi |year=1996 |title=[[Encyclopedia of the History of Arabic Science]] |volume=1 & 3 |publisher=[[Routledge]] |isbn=0415124107 }} * {{Citation | last=Rochberg | first=Francesca | author-link= | year=2004 | title=The Heavenly Writing: Divination, Horoscopy, and Astronomy in Mesopotamian Culture | publisher=Cambridge University Press}}. ==Further reading== {{Wikiversity|History of Physics}} * Kragh, Helge "Quantum Generations: A History of Physics in the Twentieth Century" Fifth printing, and first paperback printing, Princeton University Press (2002) ISBN 0-691-09552-3. *Christa Jungnickel and Russell McCormmach, ''Intellectual Mastery of Nature. Theoretical Physics from Ohm to Einstein, Volume 1: The Torch of Mathematics, 1800 to 1870'' (University of Chicago Press, Paper cover, 1990) ISBN 0-226-41582-1 *Christa Jungnickel and Russell McCormmach, ''Intellectual Mastery of Nature. Theoretical Physics from Ohm to Einstein, Volume 2: The Now Mighty Theoretical Physics, 1870 to 1925'' (University of Chicago Press, Paper cover, 1990) ISBN 0-226-41585-6 *Emilio Segré, ''From Falling Bodies to Radio Waves: Classical Physicists and Their Discoveries'' (W. H. Freeman and Company, 1984) ISBN 0-7167-1482-5 *Nina Byers and Gary Williams, ed., [http://www.cambridge.org/us/catalogue/catalogue.asp?isbn=9780521821971 ''OUT OF THE SHADOWS:Contributions of 20th Century Women to Physics'']Cambridge University Press, 2006 ISBN 0-5218-2197-1 *Emilio Segré, ''From X-Rays to Quarks: Modern Physicists and Their Discoveries'' (W. H. Freeman and Company, 1980) ISBN 0-7167-1147-8 ==See also== * [[Famous physicists]] * [[Nobel Prize in physics]] {{portal|Physics}} [[Category:History of physics| ]] [[Category:Physics]] <!-- interwiki --> [[ar:تاريخ الفيزياء]] [[bn:পদার্থবিজ্ঞানের ইতিহাস]] [[bs:Historija fizike]] [[bg:История на физиката]] [[da:Fysikkens historie]] [[de:Geschichte der Physik]] [[es:Historia de la física]] [[eu:Fisikaren historia]] [[fr:Histoire de la physique]] [[gl:Historia da fí­sica]] [[hr:Povijest fizike]] [[id:Sejarah fisika]] [[it:Storia della fisica]] [[he:היסטוריה של הפיזיקה]] [[ka:ფიზიკის ისტორია]] [[ms:Sejarah fizik]] [[nl:Geschiedenis van de natuurkunde]] [[pl:Historia fizyki]] [[pt:História da física]] [[ru:История физики]] [[scn:Storia dâ fìsica]] [[sk:Dejiny fyziky]] [[sl:Zgodovina fizike]] [[fi:Fysiikan historia]] [[sv:Fysikens historia]] [[th:ประวัติศาสตร์ของฟิสิกส์]] [[vi:Lịch sử vật lý học]]