162-656: In contemporary history , the third millennium is the current millennium in the Anno Domini or Common Era , under the Gregorian calendar . It began on 1 January 2001 ( MMI ) and will end on 31 December 3000 ( MMM ), spanning the 21st to 30th centuries. Ongoing futures studies seek to understand what will likely continue and what could plausibly change in this period and beyond. Contemporary history Contemporary history , in English-language historiography ,
324-498: A G a μ ν , {\displaystyle {\mathcal {L}}_{\text{QCD}}={\overline {\psi }}i\gamma ^{\mu }D_{\mu }\psi -{\frac {1}{4}}G_{\mu \nu }^{a}G_{a}^{\mu \nu },} where ψ {\displaystyle \psi } is a three component column vector of Dirac spinors , each element of which refers to a quark field with a specific color charge (i.e. red, blue, and green) and summation over flavor (i.e. up, down, strange, etc.)
486-614: A μ ν W μ ν a − 1 4 B μ ν B μ ν , {\displaystyle {\mathcal {L}}_{\text{EW}}={\overline {Q}}_{Lj}i\gamma ^{\mu }D_{\mu }Q_{Lj}+{\overline {u}}_{Rj}i\gamma ^{\mu }D_{\mu }u_{Rj}+{\overline {d}}_{Rj}i\gamma ^{\mu }D_{\mu }d_{Rj}+{\overline {\ell }}_{Lj}i\gamma ^{\mu }D_{\mu }\ell _{Lj}+{\overline {e}}_{Rj}i\gamma ^{\mu }D_{\mu }e_{Rj}-{\tfrac {1}{4}}W_{a}^{\mu \nu }W_{\mu \nu }^{a}-{\tfrac {1}{4}}B^{\mu \nu }B_{\mu \nu },} where
648-424: A decline in birth rates in the industrialized world, which had multiple second-order effects. Many regions have also made divorce much easier to officially procure. However, the decline in birth rate is not a universal trend; many nations continue to have high birth rates , and the world's overall population is still growing as of 2022. One of the yet evolving and unknown impacts in the contemporary era has been
810-637: A nuclear war . An all-out "hot" war was avoided, but both sides intervened in the internal politics of smaller nations in their bid for global influence and via proxy wars . The Cold War ultimately ended with the Revolutions of 1989 and the dissolution of the Soviet Union in 1991. The latter stages and aftermath of the Cold War enabled the democratization of much of Europe, Africa, and Latin America. Decolonization
972-401: A "web of data". With the rise of information technology, computer security , and information security in general, is a concern for computers and networks. Concerns include information and services which are protected from unintended or unauthorized access, change or destruction. This has also raised questions of Internet privacy and personal privacy globally. The Space Race was one of
1134-467: A combination of genuine popularity and legal rollbacks, Russia gradually moved toward being a one-party state , a democracy but one where Putin's party always won. Russia has since intervened in a variety of military conflicts in its neighboring countries including the 2008 Russo-Georgian War ; the 2014 Russo-Ukrainian War and Annexation of Crimea ; a 2015 intervention in the Syrian Civil War ; and
1296-453: A commanding large slice of the sources of energy. Even if diminished, coal is still a popular and common style of power plant; it made up a huge proportion of South Africa and India's power grid from 1945 to the present, for example. That said, increasing price, as well as concerns both over the air pollution generated when it is burnt and the landscape destruction when it is mined (such as mountaintop removal mining ), have caused setbacks for
1458-610: A cooling of East-West relations. Germany split into two countries in 1949, liberal-democratic West Germany and communist East Germany . The conflict as a whole would become known as the Cold War . The Western Bloc formed NATO in 1949 while the Eastern Bloc formed the Warsaw Pact in 1955. Direct combat between the new Great Powers was generally avoided, although proxy wars fought in other countries by factions equipped by one side against
1620-438: A graphical representation of the perturbation theory approximation, invoke "force mediating particles", and when applied to analyze high-energy scattering experiments are in reasonable agreement with the data. However, perturbation theory (and with it the concept of a "force-mediating particle") fails in other situations. These include low-energy quantum chromodynamics, bound states , and solitons . The interactions between all
1782-471: A large disincentive to burn oil except when absolutely necessary (such as in the case of aviation fuel ), although oil continues to be one of the most popular sources of energy. Other fossil fuels have continued a prominent role in the world's energy production. Coal energy , usually credited as helping kickstart the Industrial Revolution , has declined somewhat in prominence, but it started from
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#17332029982871944-603: A lesser extent, during the Cold War, something similar happened with the Russian language in the Eastern Bloc and among communist-aligned factions; however, this status was mostly reversed after the collapse of the Soviet Union. The French and German languages saw their prestige as global languages decline after World War II. Religious trends have been disparate and not consistent across countries, often with sharply varying results even between similar and nearby groups. In industrialized and economically prosperous regions, there has been
2106-540: A loose trend toward secularization that deprioritized the role of religion, even among people who still identified as adherents. The decline of Christianity in the Western world has been perhaps the most notable of these trends, although many non-Western cultures have been affected as well, such as the rise of irreligion in China (buttressed by antireligious campaigns ). As an example of how localized this process can be, during
2268-701: A major exporter of consumer goods around the world. Science made new advances after 1945, which included spaceflight , nuclear technology , lasers , semiconductors , molecular biology , genetics , particle physics , and the Standard Model of quantum field theory . The first commercial computers were created, followed by the Internet, beginning the Information Age . In 1945, the Allies of World War II had defeated all significant opposition to them. They established
2430-1043: A member of the group SU(3), and ϕ a ( x ) {\displaystyle \phi ^{a}(x)} is an arbitrary function of spacetime. The electroweak sector is a Yang–Mills gauge theory with the symmetry group U(1) × SU(2) L , L EW = Q ¯ L j i γ μ D μ Q L j + u ¯ R j i γ μ D μ u R j + d ¯ R j i γ μ D μ d R j + ℓ ¯ L j i γ μ D μ ℓ L j + e ¯ R j i γ μ D μ e R j − 1 4 W
2592-535: A new particle with a mass of about 125 GeV/ c (about 133 proton masses, on the order of 10 kg ), which is "consistent with the Higgs boson". On 13 March 2013, it was confirmed to be the searched-for Higgs boson. Technically, quantum field theory provides the mathematical framework for the Standard Model, in which a Lagrangian controls the dynamics and kinematics of the theory. Each kind of particle
2754-459: A non-zero Vacuum expectation value , which generates masses for the Electroweak gauge fields (the Higgs' mechanism), and λ > 0 {\displaystyle \lambda >0} , so that the potential is bounded from below. The quartic term describes self-interactions of the scalar field φ {\displaystyle \varphi } . The minimum of the potential
2916-567: A phenomenon called the Japanese economic miracle . Many explanations are proffered for the enviable results of these years: relative peace (at least outside the " Third World "); a reduction in average family size; technological improvements; and others. The Eastern Bloc, meanwhile, established Comecon as their equivalent to the Marshall Plan and to establish internal trading rules between communist states. The 1970s saw economic headwinds. Notably,
3078-544: A policy of perestroika in the 1980s which allowed tentative market reforms. The fall of the USSR saw differing approaches in the 1990s in the East: some newly independent states went in a capitalist direction such as Estonia , some maintained a strong governmental presence in their economy, and some opted for a mix. The privatization of government firms and resources drew accusations of crony capitalism in many states, however, including
3240-586: A pro-Western stance. The Federation of Malaya was granted independence in 1957, with the concurrent fighting of the Malayan Emergency against communist forces from 1948–1960. The French unsuccessfully fought the First Indochina War in an attempt to hold on to French Indochina ; at the 1954 Geneva Conference , the new states of Cambodia , Laos , the Democratic Republic of Vietnam , and
3402-609: A second €130-billion Greek bailout. In 2013, the European Union agreed to a €10 billion economic bailout for Cyprus. The 2020 coronavirus pandemic caused economic disruption, with wide-ranging economic impacts of COVID-19 such as supply chain changes and an increase in working-from-home, along with the COVID-19 recession . Social changes since 1945 have been vast and disparate, affecting countries and subgroups within those countries in ways specific to each population, meaning there
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#17332029982873564-730: A series of Yugoslav Wars ; NATO eventually intervened in the Kosovo War . In the Middle East, the Israeli–Palestinian peace process offered the prospect of a long-term peace deal to many; the Oslo Accords signed in 1993 seemed to offer a "roadmap" to resolving the conflict . Despite these high hopes, they would be largely dashed in 2000–2001 after a breakdown of negotiations and the Second Intifada . The September 11 attacks were
3726-734: A series of coordinated suicide attacks by al-Qaeda upon the United States on 11 September 2001. On that morning, nineteen al-Qaeda terrorists hijacked four commercial passenger jet airliners . The hijackers intentionally crashed two of the airliners into the Twin Towers of the World Trade Center in New York City, killing everyone on board and many others working in the buildings. Both buildings collapsed within two hours, destroying nearby buildings and damaging others. The hijackers crashed
3888-459: A sharp drop in international trade , rising unemployment and slumping commodity prices. The recession renewed interest in Keynesian economic ideas on how to combat recessionary conditions. However, various industrial countries continued to undertake austerity policies to cut deficits , reduced spending , as opposed to following Keynesian theories. From late 2009 European debt crisis , fears of
4050-927: A shuttle: the Challenger disaster and the Columbia disaster ). The program ultimately had 135 missions. The retirement of NASA's Space Shuttle fleet took place from March to July 2011. The end of the Cold War saw a new era of international cooperation with the International Space Station (ISS). Commercial spaceflight also became possible as governments loosened what had previously been their firm control over satellites, opening new possibilities, but also new risks such as light pollution from satellites . The Commercial Orbital Transportation Services (COTS) program began in 2006. There are various spaceports , including spaceports of human spaceflight and other launch systems ( space logistics ). Private spaceflight
4212-686: A significant marketing feature through the early 2000s (decade), was similarly displaced by emphasis on relevancy ranking, the methods by which search engines attempt to sort the best results first. " Web 2.0 " is characterized as facilitating communication, information sharing , interoperability , User-centered design and collaboration on the World Wide Web . It has led to the development and evolution of web-based communities, hosted services , and web applications . Examples include social-networking sites , video-sharing sites , wikis , blogs, mashups and folksonomies . Social networking emerged in
4374-445: A source of vast revenue that did not require traditional government revenue-raising measures, such as tariffs or income taxation. The rising cost of oil led to the 1970s energy crisis and various adaptations in energy conservation to better conserve oil, such as more efficient engines and better insulation. It has also led to concerns of " peak oil ," that the rising extraction costs of oil will eventually lead to massive shortages and
4536-560: A sovereign debt crisis developed among investors concerning rising government debt levels across the globe together with a wave of downgrading of government debt of certain European states. Concerns intensified early 2010 and thereafter making it difficult or impossible for sovereigns to re-finance their debts. On 9 May 2010, Europe's Finance Ministers approved a rescue package worth €750 billion aimed at ensuring financial stability across Europe. The European Financial Stability Facility (EFSF)
4698-634: A third airliner into the Pentagon in Arlington, Virginia . The fourth plane crashed into a field near Shanksville in rural Somerset County, Pennsylvania , after some of its passengers and flight crew attempted to retake control of the plane. In response, the United States under President George W. Bush enacted the Patriot Act . Many other countries also strengthened their anti-terrorism legislation and expanded law enforcement powers. Major terrorist events after
4860-475: A vast increase in demand for energy development , both to power vehicles such as personal cars as well as on public electrical grids . In particular, petroleum oil has been in ravenous demand across the world. Many of the cheapest and easiest sources of oil to access were largely drained in the 19th and early 20th centuries, leading to a hunt for new sources of oil. The value of oil has spilled over into politics as well, as " petrostates " with access to oil found
5022-491: A way that was less true in the 20th century. For example, diaspora groups of immigrants can more easily stay in contact with their family and friends in their origin region, compared to earlier eras where travel and communication was far more expensive, making a narrative of strictly increasing global homogenization incomplete. International telephone networks, and later Internet telephony, allowed cheaper and easier long-distance communication than previous eras. Language usage in
3rd millennium - Misplaced Pages Continue
5184-600: Is a subset of modern history that describes the historical period from about 1945 to the present. In the social sciences, contemporary history is also continuous with, and related to, the rise of postmodernity . Contemporary history is politically dominated by the Cold War (1947–1991) between the Western Bloc , led by the United States, and the Eastern Bloc , led by the Soviet Union . The confrontation spurred fears of
5346-464: Is conventionally called a " positron ". The Standard Model includes 12 elementary particles of spin 1 ⁄ 2 , known as fermions . Fermions respect the Pauli exclusion principle , meaning that two identical fermions cannot simultaneously occupy the same quantum state in the same atom. Each fermion has a corresponding antiparticle , which are particles that have corresponding properties with
5508-431: Is degenerate with an infinite number of equivalent ground state solutions, which occurs when φ † φ = μ 2 2 λ {\displaystyle \varphi ^{\dagger }\varphi ={\tfrac {\mu ^{2}}{2\lambda }}} . It is possible to perform a gauge transformation on φ {\displaystyle \varphi } such that
5670-412: Is described in terms of a dynamical field that pervades space-time . The construction of the Standard Model proceeds following the modern method of constructing most field theories: by first postulating a set of symmetries of the system, and then by writing down the most general renormalizable Lagrangian from its particle (field) content that observes these symmetries. The global Poincaré symmetry
5832-656: Is flight beyond the Kármán line that is conducted and paid for by an entity other than a government agency. Commercialization of space is the use of equipment sent into or through outer space to provide goods or services of commercial value, either by a corporation or state. Space trade plans and predictions began in the 1960s. Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites . NASA announced in 2011 that its Mars Reconnaissance Orbiter captured photographic evidence of possible liquid water on Mars during warm seasons. On 6 August 2012,
5994-419: Is heavily linked to the concept of a Digital Age or Digital Revolution , and carries the ramifications of a shift from traditional industry that the Industrial Revolution brought through industrialization, to an economy based around the manipulation of information. The period is generally said to have begun in the latter half of the 20th century, though the particular date varies. The term began its use around
6156-477: Is implied. The gauge covariant derivative of QCD is defined by D μ ≡ ∂ μ − i g s 1 2 λ a G μ a {\displaystyle D_{\mu }\equiv \partial _{\mu }-ig_{s}{\frac {1}{2}}\lambda ^{a}G_{\mu }^{a}} , where The QCD Lagrangian is invariant under local SU(3) gauge transformations; i.e., transformations of
6318-405: Is mediated by mesons, such as the pion . The color charges inside the nucleon cancel out, meaning most of the gluon and quark fields cancel out outside of the nucleon. However, some residue is "leaked", which appears as the exchange of virtual mesons, that causes the attractive force between nucleons. The (fundamental) strong interaction is described by quantum chromodynamics, which is a component of
6480-460: Is more matter than anti-matter , incorporate the full theory of gravitation as described by general relativity , or account for the universe's accelerating expansion as possibly described by dark energy . The model does not contain any viable dark matter particle that possesses all of the required properties deduced from observational cosmology . It also does not incorporate neutrino oscillations and their non-zero masses. The development of
6642-427: Is not one single global story of social change. Despite this, one of the major trends has been an increasing interchange between cultures and a wider spread of the most successful works, enabled by new technology and globalization . In earlier periods, a successful musician or theater troupe might be confined to playing in a single city at a time, limiting their reach. The spread of better recording technology, such as
3rd millennium - Misplaced Pages Continue
6804-503: Is often called the "Soviet Union's Vietnam War" in comparison to the American defeat, being an expensive and ultimately unsuccessful war and occupation. More importantly, the intervening decades had seen that Eastern Europe was unable to compete economically with Western Europe, which undermined the promise of communist abundance compared to capitalist poverty. The Western capitalist economies had proven wealthier and stronger, which made matching
6966-404: Is postulated for all relativistic quantum field theories. It consists of the familiar translational symmetry , rotational symmetry and the inertial reference frame invariance central to the theory of special relativity . The local SU(3)×SU(2)×U(1) gauge symmetry is an internal symmetry that essentially defines the Standard Model. Roughly, the three factors of the gauge symmetry give rise to
7128-558: Is the Higgs doublet and φ ~ = i τ 2 φ ∗ {\displaystyle {\tilde {\varphi }}=i\tau _{2}\varphi ^{*}} is its charge conjugate state. The Yukawa terms are invariant under the SU ( 2 ) L × U ( 1 ) Y {\displaystyle \operatorname {SU} (2)_{\text{L}}\times \operatorname {U} (1)_{\text{Y}}} gauge symmetry of
7290-467: Is the electroweak gauge covariant derivative defined above and V ( φ ) {\displaystyle V(\varphi )} is the potential of the Higgs field. The square of the covariant derivative leads to three and four point interactions between the electroweak gauge fields W μ a {\displaystyle W_{\mu }^{a}} and B μ {\displaystyle B_{\mu }} and
7452-469: Is the only long-range force in the Standard Model. It is mediated by photons and couples to electric charge. Electromagnetism is responsible for a wide range of phenomena including atomic electron shell structure , chemical bonds , electric circuits and electronics . Electromagnetic interactions in the Standard Model are described by quantum electrodynamics. The weak interaction is responsible for various forms of particle decay , such as beta decay . It
7614-501: Is usually impossible to connect specific weather events to human impact on the world. Instead, such impact is expected to cause changes in the overall distribution and intensity of weather events, such as changes to the frequency and intensity of heavy precipitation. Broader effects are expected to include glacial retreat , Arctic shrinkage , and worldwide sea level rise . Other effects may include changes in crop yields , addition of new trade routes, species extinctions , and changes in
7776-424: Is weak and short-range, due to the fact that the weak mediating particles, W and Z bosons, have mass. W bosons have electric charge and mediate interactions that change the particle type (referred to as flavour) and charge. Interactions mediated by W bosons are charged current interactions . Z bosons are neutral and mediate neutral current interactions, which do not change particle flavour. Thus Z bosons are similar to
7938-553: The 1964 Brazilian coup d'état , the 1973 Chilean coup d'état , and others. Nicaragua suffered the most, with the Nicaraguan Revolution seeing major military aid from both great powers to their favored factions that extended a civil war in the country for decades. Mexico escaped this unrest, although functioned largely as a one-party state dominated by the PRI . Argentina had a succession of idiosyncratic governments that courted both
8100-660: The Bretton Woods system , a set of practices that governed world trade and currencies from 1945–1971, as well as the World Bank and the International Monetary Fund (IMF). Western Europe also established the European Economic Community in 1957 to ease customs and aid international trade. In general, vast quality of life improvements affected most every corner of the globe during this period, in both
8262-554: The Cuban Missile Crisis in 1963, generally considered one of the incidents most dangerously close to turning the Cold War into a direct military conflict. The 1968 Peruvian coup d'état and also installed a Soviet-friendly government. Despite this, the region ultimately leaned toward the US in this period, with the CIA supporting American-friendly factions in the 1954 Guatemalan coup d'état ,
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#17332029982878424-641: The Czech Republic was one of the most stridently irreligious , with only 15% of its population espousing any religious beliefs at all by 2011. In the Islamic world , a notable trend has been the spread of international schools of thought into regions where belief was previously localized, such as the International propagation of Salafism and Wahhabism funded by the government of Saudi Arabia . While regional Islamic groups remain strong, they are more contested than in
8586-553: The GIM mechanism , predicting the charm quark . In 1973 Gross and Wilczek and Politzer independently discovered that non-Abelian gauge theories, like the color theory of the strong force, have asymptotic freedom . In 1976, Martin Perl discovered the tau lepton at the SLAC . In 1977, a team led by Leon Lederman at Fermilab discovered the bottom quark. The Higgs mechanism is believed to give rise to
8748-742: The Islamic Emirate of Afghanistan to depose the Taliban , who had harbored al-Qaeda terrorists. The War in Afghanistan began in late 2001 and was launched by the UN-authorized ISAF , with the United States and United Kingdom providing most of the troops. The Bush administration policy and the Bush Doctrine stated forces would not distinguish between terrorist organizations and nations or governments that harbor them. Operation Enduring Freedom (OEF)
8910-573: The Six-Day War in 1967 and the Yom Kippur War of 1973. Under Anwar Sadat and later Hosni Mubarak , Egypt switched from Nasserism to favoring the Western Bloc, and signed a peace treaty with Israel. Lebanon, once among the most prosperous countries in the region and a cultural center, collapsed into the decade-long Lebanese Civil War from 1975–1990. Iran's unpopular pro-American government
9072-656: The Suez Crisis in 1956, briefly unify with Syria as the United Arab Republic (UAR) from 1958 to 1961, and expensively intervene in the North Yemen civil war from 1962 to 1970. Decolonization was the most important development across Southeast Asia and Africa from 1946–1975, as the old British, French, Dutch, and Portuguese colonial empires were dismantled. Many new states were given their independence, but soon found themselves having to choose between allying with
9234-471: The atomic nucleus , ultimately constituted of up and down quarks. On the other hand, second- and third-generation charged particles decay with very short half-lives and can only be observed in high-energy environments. Neutrinos of all generations also do not decay, and pervade the universe, but rarely interact with baryonic matter. There are six quarks: up , down , charm , strange , top , and bottom . Quarks carry color charge , and hence interact via
9396-628: The electron , electron neutrino , muon , muon neutrino , tau , and tau neutrino . The leptons do not carry color charge, and do not respond to strong interaction. The main leptons carry an electric charge of -1 e , while the three neutrinos carry a neutral electric charge. Thus, the neutrinos' motion are only influenced by weak interaction and gravity , making them difficult to observe. The Standard Model includes 4 kinds of gauge bosons of spin 1, with bosons being quantum particles containing an integer spin. The gauge bosons are defined as force carriers , as they are responsible for mediating
9558-562: The fundamental interactions . The Standard Model explains the four fundamental forces as arising from the interactions, with fermions exchanging virtual force carrier particles, thus mediating the forces. At a macroscopic scale, this manifests as a force . As a result, they do not follow the Pauli exclusion principle that constrains fermions; bosons do not have a theoretical limit on their spatial density . The types of gauge bosons are described below. The Feynman diagram calculations, which are
9720-504: The magnetophon , meant that a musical act could have their song be played over the radio everywhere without loss of sound quality, creating international superstars such as Elvis Presley and The Beatles . The spread of home television sets allowed people across the globe to easily watch the same show, rather than requiring viewers to attend a local theater. Hollywood in California produced films that dominated cinema; while intended for
9882-549: The masses of all the elementary particles in the Standard Model. This includes the masses of the W and Z bosons , and the masses of the fermions , i.e. the quarks and leptons . After the neutral weak currents caused by Z boson exchange were discovered at CERN in 1973, the electroweak theory became widely accepted and Glashow, Salam, and Weinberg shared the 1979 Nobel Prize in Physics for discovering it. The W and Z bosons were discovered experimentally in 1983; and
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#173320299828710044-651: The mn term giving the coupling of the generations m and n , and h.c. means Hermitian conjugate of preceding terms. The fields Q L {\displaystyle Q_{\text{L}}} and ℓ L {\displaystyle \ell _{\text{L}}} are left-handed quark and lepton doublets. Likewise, u R , d R {\displaystyle u_{\text{R}},d_{\text{R}}} and e R {\displaystyle e_{\text{R}}} are right-handed up-type quark, down-type quark, and lepton singlets. Finally φ {\displaystyle \varphi }
10206-744: The natural environment and human life are, at least in part, already being attributed to global warming. A 2001 report by the Intergovernmental Panel on Climate Change suggests that glacier retreat , ice shelf disruption such as that of the Larsen Ice Shelf , sea level rise , changes in rainfall patterns, and increased intensity and frequency of extreme weather events are attributable in part to global warming. Other expected effects include water scarcity in some regions and increased precipitation in others, changes in mountain snowpack, and adverse health effects from warmer temperatures. It
10368-572: The price of oil started to go up in the 1970s, as the easiest and most accessible wells had already been pumped dry in the preceding century, and oil is a non-renewable resource. Attention was drawn to the abundant oil in the Middle East, where countries in OPEC controlled substantial untapped oil reserves. Political tensions over the Yom Kippur War and the Iranian Revolution led to the 1973 oil crisis and 1979 oil crisis . The Soviet Union called it
10530-585: The strong interaction . The color confinement phenomenon results in quarks being strongly bound together such that they form color-neutral composite particles called hadrons ; quarks cannot individually exist and must always bind with other quarks. Hadrons can contain either a quark-antiquark pair ( mesons ) or three quarks ( baryons ). The lightest baryons are the nucleons : the proton and neutron . Quarks also carry electric charge and weak isospin , and thus interact with other fermions through electromagnetism and weak interaction . The six leptons consist of
10692-491: The universe and classifying all known elementary particles . It was developed in stages throughout the latter half of the 20th century, through the work of many scientists worldwide, with the current formulation being finalized in the mid-1970s upon experimental confirmation of the existence of quarks . Since then, proof of the top quark (1995), the tau neutrino (2000), and the Higgs boson (2012) have added further credence to
10854-609: The " Era of Stagnation ". The 1970s and 80s also saw the rise of the Four Asian Tigers , as South Korea, Taiwan, Singapore, and Hong Kong emulated the Japanese route to prosperity with varying degree of success. In China, the leftist Gang of Four were overthrown in 1976, and Deng Xiaoping pursued a policy of tentatively opening the Chinese economy to capitalist innovations throughout the 1980s, which would be continued by his successors in
11016-512: The 1950s proved overly optimistic, however. Atomic energy grew to be a large part of several nations energy generation strategies, especially nuclear power in France . Nuclear power continues to be controversial. Concerns include its association with nuclear weapons , financial cost , disposal of radioactive nuclear waste , and fears of safety from reactor meltdowns , especially after the 1986 Chernobyl disaster . An anti-nuclear movement arose that
11178-586: The 1970s and 80s, the US took a new approach with the Space Shuttle program , hoping to reduce the cost of launches by creating a re-usable Space Shuttle. The first fully functional Space Shuttle orbiter was Columbia (designated OV-102), launched into low Earth orbit in April 1981. In 1996, Shuttle mission STS-75 conducted research in space with the electrodynamic tether generator and other tether configurations. The program suffered from two incidents that destroyed
11340-514: The 1990s. China's economy, tiny in 1976, would see tremendous growth, and eventually take the spot as second largest economy from Japan in 2010. Among Western economies, the collapse of the Bretton Woods system was replaced by a more flexible era of floating exchange rates. The Group of Seven (G7) first met in 1975 and become one of the main international forums that regulated international trade among developed country . The Soviet Union implemented
11502-717: The Cold War both the Polish People's Republic and the Czechoslovak Socialist Republic endorsed state atheism . However, after the fall of the Iron Curtain in 1989–1990, the people of these bordering states had radically different cultural attitudes toward religion; Poland was one of the more religious states in Europe, with 96% of its population espousing a belief in Catholic Christianity in 2011, while
11664-514: The European Union with the signing of the Maastricht Treaty in 1993, which integrated Europe across borders to a new degree. International coalitions continued to have a role; the Gulf War saw a large international coalition undo Baathist Iraq's annexation of Kuwait, but other "police" style actions were less successful. Somalia and Afghanistan descended into long, bloody civil wars for almost
11826-539: The Higgs boson is massive, it must interact with itself. Because the Higgs boson is a very massive particle and also decays almost immediately when created, only a very high-energy particle accelerator can observe and record it. Experiments to confirm and determine the nature of the Higgs boson using the Large Hadron Collider (LHC) at CERN began in early 2010 and were performed at Fermilab 's Tevatron until its closure in late 2011. Mathematical consistency of
11988-1333: The Higgs' mass could not be predicted beforehand and had to be determined experimentally. The Yukawa interaction terms are: L Yukawa = ( Y u ) m n ( Q ¯ L ) m φ ~ ( u R ) n + ( Y d ) m n ( Q ¯ L ) m φ ( d R ) n + ( Y e ) m n ( ℓ ¯ L ) m φ ( e R ) n + h . c . {\displaystyle {\mathcal {L}}_{\text{Yukawa}}=(Y_{\text{u}})_{mn}({\bar {Q}}_{\text{L}})_{m}{\tilde {\varphi }}(u_{\text{R}})_{n}+(Y_{\text{d}})_{mn}({\bar {Q}}_{\text{L}})_{m}\varphi (d_{\text{R}})_{n}+(Y_{\text{e}})_{mn}({\bar {\ell }}_{\text{L}})_{m}{\varphi }(e_{\text{R}})_{n}+\mathrm {h.c.} } where Y u {\displaystyle Y_{\text{u}}} , Y d {\displaystyle Y_{\text{d}}} , and Y e {\displaystyle Y_{\text{e}}} are 3 × 3 matrices of Yukawa couplings, with
12150-605: The Iraqi Government. Despite government assumptions that the war in Iraq would be over with the fall of Hussein, it continued and intensified. Sectarian groups both fought each other and the occupying coalition forces via asymmetric warfare during the Iraqi insurgency , as Iraq was starkly divided between Sunni, Shia, and Kurdish groups that now competed with each other for power. Al-Qaeda operations in Iraq continued as well. In late 2008,
12312-701: The Mars Science Laboratory Curiosity , the most elaborate Martian exploration vehicle to date, landed on Mars. After the WMAP observations of the cosmic microwave background , information was released in 2011 of the work done by the Planck Surveyor , estimating the Age of the universe to 13.8 billion years old (a 100 million years older than previously thought). Another technological advancement came in 2012 with European physicists statistically demonstrating
12474-465: The Russian Federation, the largest and most important state of the USSR; the beneficiaries of the turbulent period were often called the " Russian oligarchs ". In the beginning of the 2000s, there was a global rise in prices in commodities and housing, marking an end to the 2000s commodities boom . The US mortgage-backed securities, which had risks that were hard to assess, were marketed around
12636-484: The September 11 attacks include the 2002 Bali bombings , the 2002 Moscow theater hostage crisis , the 2003 Istanbul bombings , the 2004 Madrid train bombings , the 2004 Beslan school siege , the 2005 London bombings , the 2005 Delhi bombings , and the 2008 Mumbai attacks , generally from Islamic terrorism . The United States responded to the 11 September 2001 attacks by launching a "Global War on Terrorism", invading
12798-507: The Soviet Union, after which followed the 1948 Arab–Israeli War . Egypt's weak and ineffective king Farouk was overthrown in the 1952 Egyptian revolution , and replaced by General Nasser ; the 1953 Iran coup saw the American-friendly shah Mohammad Reza Pahlavi remove the democratic constraints on his government and take power directly; and Iraq's Western-friendly monarchy was overthrown in 1958 . Nasser's Egypt would go on to face
12960-550: The Soviet defense budget to the American one strain limited resources. The Pan-European Picnic in 1989 then set in motion a peaceful chain reaction with the subsequent fall of the Berlin Wall . The Revolutions of 1989 saw many countries of Eastern Europe throw off their communist governments, and the USSR declined to invade to re-establish them. East and West Germany were reunified . Client state status for many states ended, as there
13122-515: The Soviets deteriorated in the 1960s and 70s, resulting in the Sino-Soviet split , although the two were able to cooperate on some matters. " Ping-pong diplomacy " led to a rapprochement between the US and China and American recognition of the Chinese communist government in the 1970s. China's pro-democracy movement was suppressed after the 1989 Tiananmen Square protests , and China's government survived
13284-510: The Standard Model and generate masses for all fermions after spontaneous symmetry breaking. The Standard Model describes three of the four fundamental interactions in nature; only gravity remains unexplained. In the Standard Model, such an interaction is described as an exchange of bosons between the objects affected, such as a photon for the electromagnetic force and a gluon for the strong interaction. Those particles are called force carriers or messenger particles . Despite being perhaps
13446-476: The Standard Model requires that any mechanism capable of generating the masses of elementary particles must become visible at energies above 1.4 TeV ; therefore, the LHC (designed to collide two 7 TeV proton beams) was built to answer the question of whether the Higgs boson actually exists. On 4 July 2012, two of the experiments at the LHC ( ATLAS and CMS ) both reported independently that they had found
13608-510: The Standard Model was driven by theoretical and experimental particle physicists alike. The Standard Model is a paradigm of a quantum field theory for theorists, exhibiting a wide range of phenomena, including spontaneous symmetry breaking , anomalies , and non-perturbative behavior. It is used as a basis for building more exotic models that incorporate hypothetical particles , extra dimensions , and elaborate symmetries (such as supersymmetry ) to explain experimental results at variance with
13770-496: The Standard Model, such as the existence of dark matter and neutrino oscillations. In 1928, Paul Dirac introduced the Dirac equation which implied the existence of antimatter . In 1954, Yang Chen-Ning and Robert Mills extended the concept of gauge theory for abelian groups , e.g. quantum electrodynamics , to nonabelian groups to provide an explanation for strong interactions . In 1957, Chien-Shiung Wu demonstrated parity
13932-487: The Standard Model. In addition, the Standard Model has predicted various properties of weak neutral currents and the W and Z bosons with great accuracy. Although the Standard Model is believed to be theoretically self-consistent and has demonstrated some success in providing experimental predictions , it leaves some physical phenomena unexplained and so falls short of being a complete theory of fundamental interactions . For example, it does not fully explain why there
14094-510: The U.S. and Iraqi governments approved a Status of Forces Agreement effective through to the end of 2011. The Obama administration re-focused US involvement in the conflict on the withdrawal of its troops from Iraq and a surge of troops and government support in Afghanistan. In May 2011, the bin Laden raid occurred after bin Laden was tracked to his compound in Abbottabad , Pakistan. In 2011,
14256-564: The US and USSR, but generally mismanaged the economy. The Middle East saw events that presaged later conflicts in the 70s and 80s. A few years after the end of the UAR's union between Egypt and Syria, Syria's government was overthrown in the 1966 Syrian coup d'état and replaced with the Neo-Baathist Party, eventually leading to the leadership of the Al-Assad family . Israel and its neighbors fought
14418-491: The United Nations and European Union, emerged during the period after 1945. Countercultures rose and the sexual revolution transformed social relations in western countries between the 1960s and 1980s, as seen in the protests of 1968 . Living standards rose sharply across the developed world because of the post-war economic boom . Japan and West Germany both emerged as exceptionally strong economies. The culture of
14580-533: The United Nations to govern international relations and disputes. A looming question was how to handle the defeated Axis nations and the shattered nations that the Axis had conquered. Following the Yalta Conference , territory was divided into zones for which Allied country would have responsibility and manage rebuilding. While these zones were theoretically temporary (such as the eventual fate of occupied Austria , which
14742-509: The United States spread widely, with American television and movies spreading across the world. Some Western countries began a slow process of deindustrializing in the 1970s; globalization led to the emergence of new financial and industrial centers in Asia. The Japanese economic miracle was later followed by the Four Asian Tigers of Hong Kong, Singapore, South Korea and Taiwan . China launched major economic reforms from 1979 onward, becoming
14904-554: The United States and the United States dollar took a pivotal role in the world economy , displacing the UK. The era is sometimes called " Pax Americana " for the relative liberal peace in the Western world, resulting from the preponderance of power enjoyed by the US, as a comparison to the Pax Romana established at the height of the Roman Empire. New York's financial sector (" Wall Street ") was
15066-505: The United States declared a formal end to the Iraq War . In February 2020, President Donald Trump agreed with the Taliban to withdraw all American troops from Afghanistan over the next year. The Biden administration delayed the withdrawal by a few months, but still largely kept to the deal; the coalition-supported Afghan government soon collapsed, and the Taliban took undisputed control of
15228-522: The United States in 2007, was sparked by the outbreak of the 2007–2008 financial crisis . The modern financial crisis was linked to earlier lending practices by financial institutions and the trend of securitization of American real estate mortgages. The Great Recession spread to much of the developed country , and has caused a pronounced deceleration of economic activity. The global recession occurred in an economic environment characterized by various imbalances. This global recession has resulted in
15390-729: The Western Bloc, Eastern Bloc, or attempting to stay neutral as a member of the Non-Aligned Movement . British India was granted independence in 1947 without an outright war of independence being required. It was partitioned into Hindu-majority India and Muslim-majority Pakistan ( West Pakistan and East Pakistan , future Pakistan and Bangladesh ); Indo-Pakistani wars were fought in 1947, 1965, and 1971. Sukarno took control of an independent Indonesia in 1950, as attempts to reinstate Dutch rule in 1945–1949 had largely failed, and took an independent-to-Eastern leaning stance. He would later be overthrown by Suharto in 1968, who took
15552-401: The Western and Eastern spheres. France called them Les Trente Glorieuses ("The Glorious Thirty [Years]"). Despite being largely destroyed in the war, West Germany soon bounced back to being an economic powerhouse by the 1950s with the wirtschaftswunder . Surprisingly, Japan followed Germany, achieving incredible economic growth and becoming the second largest economy in the world in 1968,
15714-462: The addition of fermion mass terms into the electroweak Lagrangian is forbidden, since terms of the form m ψ ¯ ψ {\displaystyle m{\overline {\psi }}\psi } do not respect U(1) × SU(2) L gauge invariance. Neither is it possible to add explicit mass terms for the U(1) and SU(2) gauge fields. The Higgs mechanism is responsible for the generation of
15876-441: The center of the financial world from 1945–1970 in a dominant way unlikely to be seen again. Unlike the aftermath of World War I, the US strongly aided in the rebuilding of Europe, including aid to the defeated Axis nations, rather than punishment. The Marshall Plan sent billions of dollars of aid to Western Europe to ensure its stability and ward off a potential economic downturn. The 1944 Bretton Woods Conference established
16038-422: The coal industry. Natural gas has grown in its proportion of the market, especially as Liquefied natural gas (LNG) has enabled it to be transported over longer distances than was previously feasible. An entirely new form of energy creation dawned in the 1950s and 1960s: nuclear power for peaceful purposes and the construction of nuclear power plants . Hopes that atomic energy would be " too cheap to meter " in
16200-558: The contemporary era has seen a rise in English as a lingua franca , where people across the world learn the English language as a second language . This has been both to facilitate international communication, especially in places tied to international trade or tourism, as well as to better consume widespread English-language media. This is tied to increased Americanization , as American culture has grown increasingly influential and widespread. To
16362-466: The contemporary era. Wind energy , while used on a small scale for centuries, has seen growth with large distributed groups of windmills used to produce energy for the grid. Solar power has also grown in prominence, with around 4% of the world's overall energy production in 2021 (compared to a much smaller slice before). While these energy sources are considered to be much less environmentally impactful than fossil fuels , concerns have been raised over
16524-655: The country in August 2021 after the successful 2021 Taliban offensive . The Arab Spring began in earnest in 2010 with anti-government protests in the Muslim world , but quickly escalated to full-scale military conflicts in countries like Syria , Libya , and Yemen and also gave the opportunity for the emergence of various militant groups including the Islamic State (IS). The IS was able to take advantage of social media platforms including Twitter to recruit foreign fighters from around
16686-759: The creation of states such as First Nigerian Republic in 1963. Portugal, on the other hand, fiercely held onto their Empire, leading to the Portuguese Colonial War from 1961–1974 in Angola, Guinea-Bissau, and Mozambique until the Estado Novo government fell. Meanwhile, apartheid-era South Africa remained fiercely anti-communist, but withdrew from the British Commonwealth in 1961, and supported various pro-colonial factions across Africa that had lost support from their "home" governments in Europe. Many of
16848-567: The development optimistically; it was thought the world was steadily progressing toward free, liberal democracies. South Africa, no longer able to attract Western support by claiming to be anti-communist, ended apartheid in the early 1990s, and many Eastern European countries switched to stable democracies. While some Americans had anticipated a "peace dividend" from budget cuts to the Defense Department, these cuts were not as large as some had hoped. The European Economic Community evolved into
17010-401: The early 21st century as a popular social communication, largely replacing much of the function of email, message boards and instant messaging services. Twitter, Facebook, and YouTube are all major examples of social websites that gained widespread popularity. The information distribution continued into the early 21st century with mobile interaction and Internet access growing massively in
17172-462: The early 21st century. By the 2010s, a majority of people in the developed world had Internet access and a majority of people worldwide had a mobile phone. Marking the rise of mobile computing , worldwide sales of personal computers fall 14% during the first quarter of 2013. The Semantic Web (dubbed, "Web 3.0") begins the inclusion of semantic content in web pages, converting the current web dominated by unstructured and semi-structured documents into
17334-562: The ease in enabling like-minded people to collaborate at long-distance, even if the digital utopianism of the 1990s is less common. Pessimistic assessments worry about the effects on children such as enabling cyberbullying ; filter bubbles where Internet users are not challenged by outsider views; " cancel culture " where people are pilloried online but sometimes disproportionately; and slacktivism as an appealing but ineffective replacement for older forms of community work. The growing world population and rising standards of living has caused
17496-577: The entirety of the decade ( Somali Civil War , Afghan Civil War (1992–1996) , Afghan Civil War (1996–2001) ). Russia fought a brutal war in Chechnya that failed to suppress the insurgency there from 1994–1996; war would resume during the Second Chechen War in 1999–2000 that saw a resumption of Russian control after Russia successfully convinced enough rebels to join their cause with promises of autonomy. The breakup of Yugoslavia also led to
17658-610: The eventual Republic of Vietnam were created. The division of Indochina eventually led to the Vietnam War in the 1960s and 70s (as well as the Laotian Civil War and Cambodian Civil War ), which ended in communist North Vietnam took over Sai Gon in 1975. In Africa, France fought the grinding Algerian War from 1954–1962 that saw the end of French Algeria and the rise of a new independent Algeria . The British and French both slowly released their vast holdings, leading to
17820-626: The exception of opposite charges . Fermions are classified based on how they interact, which is determined by the charges they carry, into two groups: quarks and leptons . Within each group, pairs of particles that exhibit similar physical behaviors are then grouped into generations (see the table). Each member of a generation has a greater mass than the corresponding particle of generations prior. Thus, there are three generations of quarks and leptons. As first-generation particles do not decay, they comprise all of ordinary ( baryonic ) matter. Specifically, all atoms consist of electrons orbiting around
17982-479: The existence of the Higgs boson . Climate change and global warming reflects the notion of the modern climate . The changes of climate over the past century, have been attributed to various factors which have resulted in a global warming. This warming is the increase in the average temperature of the Earth's near-surface air and oceans since the mid-20th century and its projected continuation. Some effects on both
18144-581: The expansion of the Russo-Ukrainian War to the full-fledged Russian invasion of Ukraine where Russia declared their intent to depose the Ukrainian government and install a compliant, Russia-friendly government. The Russian government has often cited the enlargement of NATO as a major complaint . The end of World War II in 1945 saw an increase in international trade and an interconnected system of treaties and agreements to ease its flow. In particular,
18306-486: The form ψ → ψ ′ = U ψ {\displaystyle \psi \rightarrow \psi '=U\psi } , where U = e − i g s λ a ϕ a ( x ) {\displaystyle U=e^{-ig_{s}\lambda ^{a}\phi ^{a}(x)}} is 3 × 3 {\displaystyle 3\times 3} unitary matrix with determinant 1, making it
18468-862: The gauge boson masses, and the fermion masses result from Yukawa-type interactions with the Higgs field. In the Standard Model, the Higgs field is an SU ( 2 ) L {\displaystyle \operatorname {SU} (2)_{\text{L}}} doublet of complex scalar fields with four degrees of freedom: φ = ( φ + φ 0 ) = 1 2 ( φ 1 + i φ 2 φ 3 + i φ 4 ) , {\displaystyle \varphi ={\begin{pmatrix}\varphi ^{+}\\\varphi ^{0}\end{pmatrix}}={\frac {1}{\sqrt {2}}}{\begin{pmatrix}\varphi _{1}+i\varphi _{2}\\\varphi _{3}+i\varphi _{4}\end{pmatrix}},} where
18630-428: The ground state is transformed to a basis where φ 1 = φ 2 = φ 4 = 0 {\displaystyle \varphi _{1}=\varphi _{2}=\varphi _{4}=0} and φ 3 = μ λ ≡ v {\displaystyle \varphi _{3}={\tfrac {\mu }{\sqrt {\lambda }}}\equiv v} . This breaks
18792-550: The growth of a capitalist private sector in China. In Russia, President Boris Yeltsin pursued a policy of privatization, spinning off former government agencies into private corporations, attempting to handle budget problems inherited from the USSR. The end of Soviet foreign aid caused a variety of changes in countries previously part of the Eastern Bloc; many officially became democratic republics, though some were more accurately described as authoritarian or oligarchic republics and one-party states . Many Western commentators treated
18954-614: The interactions between quarks and gluons, which is a Yang–Mills gauge theory with SU(3) symmetry, generated by T a = λ a / 2 {\displaystyle T^{a}=\lambda ^{a}/2} . Since leptons do not interact with gluons, they are not affected by this sector. The Dirac Lagrangian of the quarks coupled to the gluon fields is given by L QCD = ψ ¯ i γ μ D μ ψ − 1 4 G μ ν
19116-577: The late 1980s and early 1990s, and has been used up to the present with the availability of the Internet. During the late 1990s, both Internet directories and search engines were popular— Yahoo! and Altavista (both founded 1995) were the respective industry leaders. By late 2001, the directory model had begun to give way to search engines, tracking the rise of Google (founded 1998), which had developed new approaches to relevancy ranking . Directory features, while still commonly available, became after-thoughts to search engines. Database size, which had been
19278-642: The left-handed doublet and right-handed singlet lepton fields. The electroweak gauge covariant derivative is defined as D μ ≡ ∂ μ − i g ′ 1 2 Y W B μ − i g 1 2 τ → L W → μ {\displaystyle D_{\mu }\equiv \partial _{\mu }-ig'{\tfrac {1}{2}}Y_{\text{W}}B_{\mu }-ig{\tfrac {1}{2}}{\vec {\tau }}_{\text{L}}{\vec {W}}_{\mu }} , where Notice that
19440-434: The lucrative American market, these films spread across the globe, backed by their large budgets and the cinematic expertise gathered there. The rise of the Internet in the 1990s allowed both for an ever further spread of the most popular and dominant works, but the comparatively cheap cost of publishing there, whether as a personal website, blog, or YouTube video, also allowed specific niche subcultures to connect and thrive in
19602-408: The massive spin-zero particle, was proposed as the Higgs boson , and is a key building block in the Standard Model. It has no intrinsic spin , and for that reason is classified as a boson with spin-0. The Higgs boson plays a unique role in the Standard Model, by explaining why the other elementary particles, except the photon and gluon , are massive. In particular, the Higgs boson explains why
19764-415: The most familiar fundamental interaction, gravity is not described by the Standard Model, due to contradictions that arise when combining general relativity, the modern theory of gravity, and quantum mechanics. However, gravity is so weak at microscopic scales, that it is essentially unmeasurable. The graviton is postulated to be the mediating particle, but has not yet been proved to exist. Electromagnetism
19926-519: The new government, the Islamic Republic of Afghanistan , whose grasp on power outside the major cities was shaky at best. The war was also less successful in restricting al-Qaeda than anticipated. The Iraq War began in March 2003 with the invasion of Iraq by a multinational force . The invasion of Iraq led to an occupation and the eventual capture of Saddam Hussein , who was later executed by
20088-564: The newly independent African governments struggled with the balance between being too weak and overthrown by ambitious coup-plotters, and too strong and becoming dictatorships. Latin America saw gradual economic growth but also instability in many countries, as the threat of coups and military regimes ( juntas ) were a major threat. The most famous was the Cuban Revolution that overthrew Fulgencio Batista 's American-friendly government for Fidel Castro 's Soviet-aligned government. This led to
20250-569: The other side's faction occurred. An arms race to develop and build nuclear weapons happened as policymakers wanted to ensure their side had more if it came to a war. In East Asia, Chiang Kai-shek 's Republic of China was overthrown in the Chinese Communist Revolution from 1945–1949. His government retreated to Taiwan , but both the nationalist KMT government and the new communist mainland government under Mao Zedong continued to claim authority over all of China. Korea
20412-427: The particles described by the Standard Model are summarized by the diagrams on the right of this section. The Higgs particle is a massive scalar elementary particle theorized by Peter Higgs ( and others ) in 1964, when he showed that Goldstone's 1962 theorem (generic continuous symmetry, which is spontaneously broken) provides a third polarisation of a massive vector field. Hence, Goldstone's original scalar doublet,
20574-400: The past. Another social trend has been the rise of urbanization as a larger proportion of the world's population has moved to live in cities and urban areas, and fewer people live in rural areas. In the United States, as the overall population more than doubled from 1930 to 1990, around a third of its counties saw their population decline by around 27%, suggesting that as rural counties empty,
20736-431: The photon has no mass, while the W and Z bosons are very heavy. Elementary-particle masses and the differences between electromagnetism (mediated by the photon) and the weak force (mediated by the W and Z bosons) are critical to many aspects of the structure of microscopic (and hence macroscopic) matter. In electroweak theory , the Higgs boson generates the masses of the leptons (electron, muon, and tau) and quarks. As
20898-423: The photon, aside from them being massive and interacting with the neutrino. The weak interaction is also the only interaction to violate parity and CP . Parity violation is maximal for charged current interactions, since the W boson interacts exclusively with left-handed fermions and right-handed antifermions. In the Standard Model, the weak force is understood in terms of the electroweak theory, which states that
21060-564: The range of disease vectors . Until 2009, the Arctic Northwest Passage pack ice prevented regular marine shipping throughout most of the year in this area, but climate change has reduced the pack ice, and this Arctic shrinkage made the waterways more navigable. Standard Model The Standard Model of particle physics is the theory describing three of the four known fundamental forces ( electromagnetic , weak and strong interactions – excluding gravity ) in
21222-450: The ratio of their masses was found to be as the Standard Model predicted. The theory of the strong interaction (i.e. quantum chromodynamics , QCD), to which many contributed, acquired its modern form in 1973–74 when asymptotic freedom was proposed (a development which made QCD the main focus of theoretical research) and experiments confirmed that the hadrons were composed of fractionally charged quarks. The term "Standard Model"
21384-523: The rivalries of the Cold War, with both the United States space program ( NASA ) and the Soviet space program launching satellites , probes, and planning missions. While the Soviets put the first human into space with Yuri Gagarin , the Americans soon caught up, and the US was the first to launch a successful Moon landing mission with Apollo 11 in 1969, followed by five more landings in the next few years. In
21546-649: The scalar field φ {\displaystyle \varphi } . The scalar potential is given by V ( φ ) = − μ 2 φ † φ + λ ( φ † φ ) 2 , {\displaystyle V(\varphi )=-\mu ^{2}\varphi ^{\dagger }\varphi +\lambda \left(\varphi ^{\dagger }\varphi \right)^{2},} where μ 2 > 0 {\displaystyle \mu ^{2}>0} , so that φ {\displaystyle \varphi } acquires
21708-689: The scale of electroweak physics. This is the only dimensional parameter of the Standard Model and has a measured value of ~ 246 GeV/ c . After symmetry breaking, the masses of the W {\displaystyle {\text{W}}} and Z {\displaystyle {\text{Z}}} are given by m W = 1 2 g v {\displaystyle m_{\text{W}}={\frac {1}{2}}gv} and m Z = 1 2 g 2 + g ′ 2 v {\displaystyle m_{\text{Z}}={\frac {1}{2}}{\sqrt {g^{2}+g'^{2}}}v} , which can be viewed as predictions of
21870-416: The social effects of cheap and common Internet access. As users gradually switched from personal web pages to blogs to social media, many surprising effects have resulted with both positive and negative assessments. Optimistic assessments often praise the decentralized nature that allows anyone to theoretically gain a platform without the need to convince a publisher or media company to back them, as well as
22032-510: The southern half of the country, while the northern reaches are controlled by a mixture of Arab Sunni rebels, Kurds, and Turkey. Vladimir Putin , Yeltsin's successor, was very popular in Russia after his victory in the Second Chechen War. He portrayed himself as a corruption fighter initially, checking Russian oligarchs who had acquired vast wealth during Russia's liberalization period. With
22194-430: The strong force becomes weaker, as the energy scale increases. The strong force overpowers the electrostatic repulsion of protons and quarks in nuclei and hadrons respectively, at their respective scales. While quarks are bound in hadrons by the fundamental strong interaction, which is mediated by gluons, nucleons are bound by an emergent phenomenon termed the residual strong force or nuclear force . This interaction
22356-522: The subscript j {\displaystyle j} sums over the three generations of fermions; Q L , u R {\displaystyle Q_{L},u_{R}} , and d R {\displaystyle d_{R}} are the left-handed doublet, right-handed singlet up type, and right handed singlet down type quark fields; and ℓ L {\displaystyle \ell _{L}} and e R {\displaystyle e_{R}} are
22518-774: The superscripts + and 0 indicate the electric charge Q {\displaystyle Q} of the components. The weak hypercharge Y W {\displaystyle Y_{\text{W}}} of both components is 1. Before symmetry breaking, the Higgs Lagrangian is L H = ( D μ φ ) † ( D μ φ ) − V ( φ ) , {\displaystyle {\mathcal {L}}_{\text{H}}=\left(D_{\mu }\varphi \right)^{\dagger }\left(D^{\mu }\varphi \right)-V(\varphi ),} where D μ {\displaystyle D_{\mu }}
22680-451: The symmetry of the ground state. The expectation value of φ {\displaystyle \varphi } now becomes ⟨ φ ⟩ = 1 2 ( 0 v ) , {\displaystyle \langle \varphi \rangle ={\frac {1}{\sqrt {2}}}{\begin{pmatrix}0\\v\end{pmatrix}},} where v {\displaystyle v} has units of mass and sets
22842-541: The tensions that would roil the Soviet-aligned bloc during the 1980s. South Korea (in the June Democratic Struggle ) and Taiwan (with the lifting of martial law ) would take major steps toward liberalization in 1987–1988, shifting from Western-aligned one-party states to more fully participatory democracies. The 1980s saw a general retreat for the communist bloc. The Soviet–Afghan War (1979–1989)
23004-467: The theory. The photon remains massless. The mass of the Higgs Boson is m H = 2 μ 2 = 2 λ v {\displaystyle m_{\text{H}}={\sqrt {2\mu ^{2}}}={\sqrt {2\lambda }}v} . Since μ {\displaystyle \mu } and λ {\displaystyle \lambda } are free parameters,
23166-434: The three fundamental interactions. The fields fall into different representations of the various symmetry groups of the Standard Model (see table). Upon writing the most general Lagrangian, one finds that the dynamics depends on 19 parameters, whose numerical values are established by experiment. The parameters are summarized in the table (made visible by clicking "show") above. The quantum chromodynamics (QCD) sector defines
23328-418: The urban counties are where the vast majority of inhabitants are moving to. In Eastern Africa, the urban population soared from 11 million in 1920 to 77 million in 2010. Many rural Chinese people moved to large coastal cities such as Shenzhen to work in the 1990s and 2000s, leading to a sharp increase of Urbanization in China . Rural parts of Japan have seen stark population declines, especially among
23490-556: The various rare earth metals used in the production of batteries and solar, which can require destructive mining techniques to gather. The Information Age or Information Era, also commonly known as the Age of the Computer, is an idea that the current age will be characterized by the ability of individuals to transfer information freely, and to have instant access to knowledge that would have been difficult or impossible to find previously. The idea
23652-546: The weak and electromagnetic interactions become united into a single electroweak interaction at high energies. The strong nuclear force is responsible for hadronic and nuclear binding . It is mediated by gluons, which couple to color charge. Since gluons themselves have color charge, the strong force exhibits confinement and asymptotic freedom . Confinement means that only color-neutral particles can exist in isolation, therefore quarks can only exist in hadrons and never in isolation, at low energies. Asymptotic freedom means that
23814-423: The world and a broad based credit boom fed a global speculative bubble in real estate and equities. The financial situation was also affected by a sharp increase in oil and food prices . The collapse of the American housing bubble caused the values of securities tied to real estate pricing to plummet thereafter, damaging financial institutions. The Great Recession , a severe economic recession which began in
23976-801: The world and seized significant portions of territory in Iraq , Syria , Afghanistan , and the Sinai Peninsula of Egypt from 2013 and ongoing. On the other hand, some violent militant organizations were able to negotiate peace with governments including the Moro Islamic Liberation Front in the Philippines in 2014. The presence of IS and the stalemate in the Syrian civil war created a migration of refugees to Europe and also galvanized and encouraged high-profile terrorism attacks and armed conflicts around
24138-627: The world, such as the November 2015 Paris attacks and the Siege of Marawi in the Philippines in 2017. In 2014, the United States decided to intervene against the Islamic State in Iraq , with most IS fighters being driven out by the end of 2018. Russia and Iran also jointly launched a campaign against IS and in support of Syrian President Bashar al-Assad . As of 2022, Assad has largely regained authority in
24300-462: The young, with only the Greater Tokyo area continuing to grow. How to deal with this change is a major issue, as many cities and their transportation networks were not designed to serve the larger populations that now occupy them. A major trend in many industrialized nations was the sexual revolution , an adoption of publicly more tolerant attitudes toward sex and pre-marital sex . " The pill "
24462-444: Was a special purpose vehicle financed by members of the eurozone to combat the European sovereign debt crisis. In October 2011 eurozone leaders agreed on another package of measures designed to prevent the collapse of member economies. The three most affected countries, Greece, Ireland and Portugal, collectively account for six percent of eurozone's gross domestic product (GDP). In 2012, eurozone finance ministers reached an agreement on
24624-503: Was another important trend in Southeast Asia, the Middle East, and Africa as new states gained independence from European colonial empires during the period from 1945–1975. The Middle East also saw a conflict involving the new state of Israel , the rise of petroleum politics , the continuing prominence but later decline of Arab nationalism , and the growth of Islamism . The first supranational organizations of government, such as
24786-581: Was divided similarly to Germany, with the Soviet Union occupying the North and the United States occupying the South (future North Korea and South Korea ). Unlike Germany, the conflict there turned hot, as the Korean War erupted from 1950–1953. Korea was not reunified under either government, however, due to strong support from both the US and China for their favored side; it became a frozen conflict instead. Japan
24948-429: Was first approved for use in 1960 in the United States, and spread rapidly around the world. The pill made birth control easier and more reliable than earlier methods. This made sex for pleasure less likely to result in unintended children. It also allowed for easier family planning , where couples could choose more specifically when to have kids compared to earlier eras. Some analysts credit this as one reason behind
25110-468: Was given a new constitution foreswearing aggressive war in 1947, and the American occupation ended in 1952 , although a treaty of mutual aid with the US was soon signed. The US also granted the Philippines their independence in 1946 while keeping close relations. The Middle East became a hotbed of instability. The new Jewish state of Israel declared its independence, recognized by both the United States and
25272-648: Was introduced by Abraham Pais and Sam Treiman in 1975, with reference to the electroweak theory with four quarks. Steven Weinberg , has since claimed priority, explaining that he chose the term Standard Model out of a sense of modesty and used it in 1973 during a talk in Aix-en-Provence in France. The Standard Model includes members of several classes of elementary particles, which in turn can be distinguished by other characteristics, such as color charge . All particles can be summarized as follows: Notes : [†] An anti-electron ( e )
25434-530: Was no conflict left to fund. The Malta Summit on 3 December 1989, the failure of the August Coup by Soviet hardliners, and the formal dissolution of the Soviet Union on 26 December 1991 sealed the end of the Cold War. The end of the Cold War left the United States the world's sole superpower. Communism seemed discredited; while China remained an officially communist state, Deng Xiaoping's economic reforms and socialism with Chinese characteristics allowed for
25596-508: Was not conserved in the weak interaction . In 1961, Sheldon Glashow combined the electromagnetic and weak interactions . In 1964, Murray Gell-Mann and George Zweig introduced quarks and that same year Oscar W. Greenberg implicitly introduced color charge of quarks. In 1967 Steven Weinberg and Abdus Salam incorporated the Higgs mechanism into Glashow's electroweak interaction , giving it its modern form. In 1970, Sheldon Glashow, John Iliopoulos, and Luciano Maiani introduced
25758-592: Was overthrown in the 1979 Iranian Revolution and was replaced by a new Islamic Republic headed by Ruhollah Khomeini . Iran and Baathist Iraq under Saddam Hussein then fought each other in the Iran–Iraq War from 1980–1988, which ended inconclusively. In East Asia, China underwent the Cultural Revolution from 1966 to 1976, a major internal struggle that saw an intense program of Maoism and persecution of perceived internal enemies. China's relations with
25920-457: Was released to independence as a neutral country), growing tensions between the Western Bloc , led by the United States, with the Eastern Bloc , led by the Soviet Union , meant that many calcified into place. Countries in Soviet zones of Eastern Europe had communist regimes installed as satellite states . The Berlin Blockade of 1948 led to a Western Airlift to preserve West Berlin and signified
26082-511: Was skeptical of atomic energy and has discouraged many projects. Nuclear proponents counter that nuclear energy produces no air pollution compared to traditional fossil fuel plants, and can provide a steady supply of energy regardless of external conditions unlike solar and wind energy. With the supply of Russian natural gas disrupted in 2022 , France is looking to reactivate some of its older decommissioned nuclear plants, for example. Various forms of renewable energy have grown in prominence in
26244-676: Was the United States combat operation involving some coalition partners and operating primarily in the eastern and southern parts of the country along the Pakistan border; the ISAF established by the United Nations Security Council was in charge of securing the capital of Kabul and its surrounding areas. NATO assumed control of ISAF in 2003. Despite initial coalition successes, the Taliban were never entirely defeated, and continued to hold territory in mountainous regions as well as threaten
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