title: Saab AB

text: Saab AB (originally , later just SAAB and Saab Group) is a Swedish aerospace and defence company, founded in 1937. Headquartered in Stockholm, the development and the manufacturing is undertaken in Linköping. Saab produced automobiles from 1947 until 1990 when the automobile division was spun off as Saab Automobile, a joint venture with General Motors. The joint venture ended in 2000 when GM took complete ownership. From 1968 onwards the company was in a merger with commercial vehicle manufacturer Scania-Vabis, known as Saab-Scania. The two were de-merged in 1995 by the new owners, Investor AB. Despite the demerger, both Saab and Scania share the right to use the griffin logo, which originates from the coat of arms of the Swedish region of Scania.


title: Saab AB

text: "Svenska Aeroplan AktieBolag" (Swedish for "Swedish Aeroplane Company Limited") (SAAB) was founded in 1937 in Trollhättan, with the merger of Svenska Aero AB (SAAB) and Linköping based ASJA the headquarters moved to Linköping. The style "Saab" replaced "SAAB" around 1950.


title: Saab AB

text: The basic initial development was the problems for the Swedish government to get quality military aircraft delivered at the beginning of the Second World War. The final trigger was the inability to get a large number of Seversky P-35 delivered from the United States. From then on the Swedish government focused on establishing domestic production and development of military aircraft which Saab became involved in, a policy that has continued to this day.


title: Saab AB

text: Originally manufacturing aircraft, the company sought ways in which to diversify its business. Before the Second World War, a majority of cars in Sweden were imported from the United States. The US car manufacturers have been producing tanks during the war, and the US domestic market took all the US car production in the late 1940s. Hence there was a large supply shortage of private cars in Europe and Sweden, and buyers were facing waiting lists of years on new cars. In the late 1940s, Saab began manufacturing cars at its Saab Automobile division, based in Trollhättan. The first car was the Saab 92; full-scale production started 12 December 1949, based on the prototype Ursaab.


title: Saab AB

text: In the late 1950s Saab ventured into the computer market with Datasaab. The company was a result partly of the need to make a computer that would be small enough to mount in an aeroplane as navigational equipment. During the 1960s several computers were developed and sold to European countries, for uses such as banking. The aircraft computer (CK 37) was used in 1971 in the Viggen. The company was sold in 1975 to Sperry UNIVAC, while Saab retained its flight computer development.


title: Saab AB

text: In 1968 Saab AB merged with the Swedish lorry, bus and heavy-duty diesel engine manufacturer Scania-Vabis, and became Saab-Scania AB.


title: Saab AB

text: In 1990 General Motors bought 51% of the car division Saab Automobile, and acquired the rest a decade later.


title: Saab AB

text: In 1991 Investor AB completed a leveraged buyout of Saab-Scania AB. Investor AB acquired all the outstanding shares in Saab-Scania for approximately SEK 21 billion. Saab-Scania became a wholly owned subsidiary of Investor AB and the company was de-listed.


title: Saab AB

text: In 1995 Saab-Scania was divided by Investor AB into two independent companies, de-merging into Scania AB and Saab AB. The intention by Investor AB was to broaden ownership in the two companies later. Following the sale of 50% of the car division Saab Automobile AB to General Motors, the main reason behind the merger with lorry manufacturer Scania-Vabis in 1968 had disappeared.


title: Saab AB

text: Also in 1995 Saab Military Aircraft and British Aerospace (now BAE Systems) formed the joint venture company Saab-BAe Gripen AB, to manufacture, market and support Gripen internationally. This co-operation was extended in 2001 with the formation of Gripen International for the same purpose. From 1998 until 2005 British Aerospace/BAE was the largest shareholder in Saab following its acquisition of a 35% stake from Investor AB. In January 2005, BAE Systems reduced its shareholding to 20%. Investor AB maintained a 20% share.


title: Saab AB

text: 16 November 1999, Saab announced its intention is to purchase Celsius AB and the acquisition was concluded by early March 2000.


title: Saab AB

text: In September 2000 United Defense Industries (UDI) purchased Bofors Weapon Systems from Saab (the autocannon and tube artillery interests), while Saab retained the missile interests.


title: Saab AB

text: In October 2008 the company announced its intention to merge its operations with that of Simrad Optronics. The new unit will develop high-tech optronics products and will be headquartered in Norway, although other details of the new arrangement have not been finalized.


title: Saab AB

text: In 2010 the company restructured from fifteen business units into five business areas; Aeronautics, Dynamics, Electronic Defence Systems, Security and Defence Solutions, and Support and Services. According to Saab the restructuring was undertaken to become more market and customer oriented.


title: Saab AB

text: In March 2010, BAE Systems sold half of its 20% stake in the company to Investor AB, which then became the major shareholder. In June 2011, the British company sold its remaining stake bringing its 16-year involvement in Saab to an end.


title: Saab AB

text: As of August 2020, Investor AB owns a 30.16% stake in the company (39.69% of the voting rights) and is the top owner.


title: Saab AB

text: The main focus of aircraft production is fighter aircraft. Saab has been making aircraft since the 1930s, and the jet predecessors of the JAS 39 Gripen were the Tunnan, the Lansen, the Draken and the Viggen. The last civilian models made by Saab were the Saab 340 and Saab 2000. Both were mid-range turboprop-powered airliners. The development and the manufacturing of these aircraft is undertaken in Linköping.


title: Saab AB

text: In May 2019, Saab announced plans to locate a new U.S. manufacturing operation in Discovery Park District Aerospace on the west side of the Purdue University campus. The facility will do the final assembly of the T-X advanced jet trainer, which is a plane developed by Boeing and Saab for the United States Air Force.


title: Saab AB

text: Aeronautics offers airborne systems, related subsystems, Unmanned Aerial Systems (UAS) and aerostructures. The business area Aeronautics is responsible for airframe structures for JAS 39 Gripen, and whole sections for Airbus, Boeing and NH90; & system development of the JAS 39 Gripen and the Skeldar VTOL UAV. Aeronautics is also partner in the European joint UAV-project Dassault nEUROn, where Saab develop Avionics and is responsible for the overall architecture and design. Marketing and support of the JAS 39 Gripen fighter jet is also included in the Aeronautics business area.


title: Saab AB

text: Dynamics offers ground combat weapons, missile systems, torpedoes, sensor systems, unmanned underwater vehicles such as "Sabertooth" and signature management systems, remotely operated vehicles for armed forces as well as civil security applications.


title: Saab AB

text: Short range weapons offered include Carl-Gustaf, AT4/AT4 CS, STRIX and NLAW. Missile systems offered are RBS 70, RBS 23 and RBS 15.


title: Saab AB

text: Surveillance offers airborne surveillance solutions (including GlobalEye, Saab 2000 Erieye) AEW&C and fighter radar, ground-based and naval radar (including the Giraffe radar range), electronic warfare (including IDAS and ESTL) and combat systems and C4I solutions.


title: Saab AB

text: Industrial Products and Services was established on 1 January 2015 and comprises the business units Combitech, Avionics Systems, Aerostructures, Traffic Management, Vricon as well as the development of product ideas that fall outside of Saab's core business.


title: Saab AB

text: The business units within Industrial Products and Services differ from Saab's other operations by their focus on business-to-business (B2B) customers or because they are not dependent on Saab's principal end-customers. Other business areas within Saab have a customer base largely consisting of public authorities. With different customer groups come different management strategies and priorities. Opportunities to strengthen these operations in the long term are greater in the new organisation. Industrial Products and Services will work with individual growth strategies for each business unit.


title: Saab AB

text: Support and Services offer maintenance, integrated support solutions, field facilities, logistics and regional aircraft maintenance.


title: Saab AB

text: Saab Aircraft Leasing leases and resells Saab aircraft to airlines. It completed 30 transactions in 2010.


title: Saab AB

text: The Saab Barracuda LLC facility in Lillington, North Carolina, manufactures signature management products and provides customized services. Foremost among the camouflage, concealment and deception products is the Ultra Lightweight Camouflage Net System (ULCANS) which provides multi-spectral protection against visual, near infrared, thermal infrared and broadband radar detection. ULCANS is fielded with the U.S. Army and other Department of Defense organizations and is available in both woodland and desert versions. Saab Barracuda is one of only two qualified suppliers of ULCANS in North America, and currently has a competed $US1.76 billion contract, along with GMA Cover Corp.


title: 1972 Summer Olympics

text: The 1972 Summer Olympics (), officially known as the Games of the XX Olympiad () and commonly known as Munich 1972 (), was an international multi-sport event held in Munich, West Germany, from 26 August to 11 September 1972.


title: 1972 Summer Olympics

text: The event was overshadowed by the Munich massacre in the second week, in which eleven Israeli athletes and coaches and a West German police officer at Olympic village were killed by Palestinian Black September members. The motivation for the attack was the ongoing Palestinian-Israeli conflict.


title: 1972 Summer Olympics

text: The 1972 Summer Olympics were the second Summer Olympics to be held in Germany, after the 1936 Games in Berlin, which had taken place under the Nazi regime, and the most recent Olympics to be held in the country. The West German Government had been eager to have the Munich Olympics present a democratic and optimistic Germany to the world, as shown by the Games' official motto, ""Die Heiteren Spiele"",<ref name="DER SPIEGEL 35/1972"></ref> or "the cheerful Games". The logo of the Games was a blue solar logo (the "Bright Sun") by Otl Aicher, the designer and director of the visual conception commission. The hostesses wore sky-blue dirndls as a promotion of Bavarian cultural heritage. The Olympic mascot, the dachshund "Waldi", was the first officially named Olympic mascot. The Olympic Fanfare was composed by Herbert Rehbein. The Soviet Union won the most gold and overall medals.


title: 1972 Summer Olympics

text: The Olympic Park ("Olympiapark") is based on Frei Otto's plans and after the Games became a Munich landmark. The competition sites, designed by architect Günther Behnisch, included the Olympic swimming hall, the Olympics Hall ("Olympiahalle", a multipurpose facility) and the Olympic Stadium ("Olympiastadion"), and an Olympic village very close to the park. The design of the stadium was considered revolutionary, with sweeping canopies of acrylic glass stabilized by metal ropes, used on such a large scale for the first time.


title: 1972 Summer Olympics

text: Munich won its Olympic bid on 26 April 1966, at the 64th IOC Session in Rome, Italy, over bids presented by Detroit, Madrid, and Montréal. Montréal would eventually host the following Olympic games in 1976.


title: 1972 Summer Olympics

text: The Games were largely overshadowed by what has come to be known as the "Munich massacre". Just before dawn on 5 September, a group of eight members of the Palestinian Black September terrorist organization broke into the Olympic Village and took eleven Israeli athletes, coaches and officials hostage in their apartments. Two of the hostages who resisted were killed in the first moments of the break-in; the subsequent standoff in the Olympic Village lasted for almost 18 hours.


title: 1972 Summer Olympics

text: Late in the evening of 5 September that same day, the terrorists and their nine remaining hostages were transferred by helicopter to the military airport of Fürstenfeldbruck, ostensibly to board a plane bound for an undetermined Arab country. The German authorities planned to ambush them there, but underestimated the numbers of their opposition and were thus undermanned. During a botched rescue attempt, all of the Israeli hostages were killed. Four of them were shot, then incinerated when one of the terrorists detonated a grenade inside the helicopter in which the hostages were sitting. The 5 remaining hostages were then shot and killed with a machine gun.


title: 1972 Summer Olympics

text: All but three of the terrorists were killed as well. Although arrested and imprisoned pending trial, they were released by the West German government on 29 October 1972, in exchange for the hijacked Lufthansa Flight 615. Two of those three were supposedly hunted down and assassinated later by the Mossad. Jamal Al-Gashey, who is believed to be the sole survivor, is still living today in hiding in an unspecified African country with his wife and two children. The Olympic events were suspended several hours after the initial attack for the first time in the modern Olympic Games history, but once the incident was concluded, Avery Brundage, the International Olympic Committee president, declared that "the Games must go on". A memorial ceremony was then held in the Olympic stadium, and the competitions resumed after a stoppage of 34 hours. Due to the suspension, the Games were originally to close on 10 September and had been rescheduled to 11 September. The attack prompted heightened security at subsequent Olympics beginning with the 1976 Winter Olympics. Security at Olympics was heightened further beginning with the 2002 Winter Olympics, as they were the first to take place after the 2001 September 11 attacks.


title: 1972 Summer Olympics

text: The massacre led the German federal government to re-examine its anti-terrorism policies, which at the time were dominated by a pacifist approach adopted after World War II. This led to the creation of the elite counter-terrorist unit GSG 9, similar to the British SAS. It also led Israel to launch a campaign known as Operation Wrath of God, in which those suspected of involvement were systematically tracked down and assassinated.


title: 1972 Summer Olympics

text: The events of the Munich massacre were chronicled in the Oscar-winning documentary, "One Day in September". An account of the aftermath is also dramatized in three films: the 1976 made-for-TV movie "21 Hours at Munich", the 1986 made-for-TV movie "Sword of Gideon" and Steven Spielberg's 2005 film "Munich". In her film "1972", Artist Sarah Morris interviews Dr. Georg Sieber, a former police psychiatrist who advised the Olympics' security team, about the events and aftermath of Black September.


title: 1972 Summer Olympics

text: "The Oxford Olympics Study" established the outturn cost of the Munich 1972 Summer Olympics at US$1.0 billion in 2015-dollars. This includes sports-related costs only, that is, (i) "operational costs" incurred by the organizing committee for the purpose of staging the Games, e.g., expenditures for technology, transportation, workforce, administration, security, catering, ceremonies, and medical services, and (ii) "direct capital costs" incurred by the host city and country or private investors to build, e.g., the competition venues, the Olympic village, international broadcast center, and media and press center, which are required to host the Games. Indirect capital costs are "not" included, such as for road, rail, or airport infrastructure, or for hotel upgrades or other business investment incurred in preparation for the Games but not directly related to staging the Games. The cost for Munich 1972 compares with costs of US$4.6 billion for Rio 2016, US$15 billion for London 2012 (the most costly Summer Olympics to date) and US$21 billion for Sochi 2014 — the most expensive Olympic Games in history. Average cost for Summer Games since 1960 is US$5.2 billion.


title: 1972 Summer Olympics

text: Eleven nations made their first Olympic appearance in Munich: Albania, Dahomey (now Benin), Gabon, North Korea, Lesotho, Malawi, Saudi Arabia, Somalia, Swaziland, Togo, Upper Volta (now Burkina Faso).


title: 1972 Summer Olympics

text: Rhodesia's invitation to take part in the 1972 Summer Games was withdrawn by the International Olympic Committee four days before the opening ceremony, in response to African countries' (such as Ethiopia and Kenya) protests against the Rhodesian government. (Rhodesia did, however, compete in the 1972 Summer Paralympics, held a little earlier in Heidelberg.)


title: 1972 Summer Olympics

text: The report, titled ""Doping in Germany from 1950 to today"", details how the West German government helped fund a wide-scale doping program. Doping of West German athletes was prevalent at the Munich Games of 1972.


title: Pheromone

text: A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavior of the receiving individuals. There are "alarm pheromones", "food trail pheromones", "sex pheromones", and many others that affect behavior or physiology. Pheromones are used by many organisms, from basic unicellular prokaryotes to complex multicellular eukaryotes. Their use among insects has been particularly well documented. In addition, some vertebrates, plants and ciliates communicate by using pheromones. The ecological functions and evolution of pheromones are a major topic of research in the field of chemical ecology.


title: Pheromone

text: The portmanteau word "pheromone" was coined by Peter Karlson and Martin Lüscher in 1959, based on the Greek φερω "pheroo" ('I carry') and ὁρμων "hormon" ('stimulating'). Pheromones are also sometimes classified as ecto-hormones. They were researched earlier by various scientists, including Jean-Henri Fabre, Joseph A. Lintner, Adolf Butenandt, and ethologist Karl von Frisch who called them various names, like for instance "alarm substances". These chemical messengers are transported outside of the body and affect neurocircuits, including the autonomous nervous system with hormone or cytokine mediated physiological changes, inflammatory signaling, immune system changes and/or behavioral change in the recipient. They proposed the term to describe chemical signals from conspecifics that elicit innate behaviors soon after the German biochemist Adolf Butenandt had characterized the first such chemical, bombykol, a chemically well-characterized pheromone released by the female silkworm to attract mates.


title: Pheromone

text: Aggregation pheromones function in mate choice, overcoming host resistance by mass attack, and defense against predators. A group of individuals at one location is referred to as an aggregation, whether consisting of one sex or both sexes. Male-produced sex attractants have been called aggregation pheromones, because they usually result in the arrival of both sexes at a calling site and increase the density of conspecifics surrounding the pheromone source. Most sex pheromones are produced by the females; only a small percentage of sex attractants are produced by males. Aggregation pheromones have been found in members of the Coleoptera, Collembola, Diptera, Hemiptera, Dictyoptera, and Orthoptera. In recent decades, aggregation pheromones have proven useful in the management of many pests, such as the boll weevil ("Anthonomus grandis"), the pea and bean weevil ("Sitona lineatus", and stored product weevils (e.g. "Sitophilus zeamais", "Sitophilus granarius", and "Sitophilus oryzae"). Aggregation pheromones are among the most ecologically selective pest suppression methods. They are non-toxic and effective at very low concentrations.


title: Pheromone

text: Some species release a volatile substance when attacked by a predator that can trigger flight (in aphids) or aggression (in ants, bees, termites) in members of the same species. For example, "Vespula squamosa" use alarm pheromones to alert others to a threat. In "Polistes exclamans", alarm pheromones are also used as an alert to incoming predators. Pheromones also exist in plants: Certain plants emit alarm pheromones when grazed upon, resulting in tannin production in neighboring plants. These tannins make the plants less appetizing to herbivores.


title: Pheromone

text: Epideictic pheromones are different from territory pheromones, when it comes to insects. Fabre observed and noted how "females who lay their eggs in these fruits deposit these mysterious substances in the vicinity of their clutch to signal to other females of the same species they should clutch elsewhere." It may be helpful to note that the word epideictic, having to do with display or show (from the Greek 'deixis'), has a different but related meaning in rhetoric, the human art of persuasion by means of words.


title: Pheromone

text: Laid down in the environment, territorial pheromones mark the boundaries and identity of an organism's territory. In cats and dogs, these hormones are present in the urine, which they deposit on landmarks serving to mark the perimeter of the claimed territory. In social seabirds, the preen gland is used to mark nests, nuptial gifts, and territory boundaries with behavior formerly described as 'displacement activity'.


title: Pheromone

text: Social insects commonly use trail pheromones. For example, ants mark their paths with pheromones consisting of volatile hydrocarbons. Certain ants lay down an initial trail of pheromones as they return to the nest with food. This trail attracts other ants and serves as a guide. As long as the food source remains available, visiting ants will continuously renew the pheromone trail. The pheromone requires continuous renewal because it evaporates quickly. When the food supply begins to dwindle, the trail-making ceases. Pharaoh ants ("Monomorium pharaonis") mark trails that no longer lead to food with a repellent pheromone, which causes avoidance behaviour in ants.


title: Pheromone

text: The army ant "Eciton burchellii" provides an example of using pheromones to mark and maintain foraging paths. When species of wasps such as "Polybia sericea" found new nests, they use pheromones to lead the rest of the colony to the new nesting site.


title: Pheromone

text: Gregarious caterpillars, such as the forest tent caterpillar, lay down pheromone trails that are used to achieve group movement.


title: Pheromone

text: In animals, sex pheromones indicate the availability of the female for breeding. Male animals may also emit pheromones that convey information about their species and genotype.


title: Pheromone

text: At the microscopic level, a number of bacterial species (e.g. "Bacillus subtilis", "Streptococcus pneumoniae", "Bacillus cereus") release specific chemicals into the surrounding media to induce the "competent" state in neighboring bacteria. Competence is a physiological state that allows bacterial cells to take up DNA from other cells and incorporate this DNA into their own genome, a sexual process called transformation.


title: Pheromone

text: Among eukaryotic microorganisms, pheromones promote sexual interaction in numerous species. These species include the yeast "Saccharomyces cerevisiae", the filamentous fungi "Neurospora crassa" and Mucor mucedo, the water mold "Achlya ambisexualis", the aquatic fungus "Allomyces macrogynus", the slime mold "Dictyostelium discoideum", the ciliate protozoan "Blepharisma japonicum" and the multicellular green algae "Volvox carteri". In addition, male copepods can follow a three-dimensional pheromone trail left by a swimming female, and male gametes of many animals use a pheromone to help find a female gamete for fertilization.


title: Pheromone

text: Many well-studied insect species, such as the ant "Leptothorax acervorum", the moths "Helicoverpa zea" and "Agrotis ipsilon", the bee "Xylocopa sonorina," the frog Pseudophryne bibronii, and the butterfly Edith's checkerspot release sex pheromones to attract a mate, and some lepidopterans (moths and butterflies) can detect a potential mate from as far away as . Some insects, such as ghost moths, use pheromones during lek mating. Traps containing pheromones are used by farmers to detect and monitor insect populations in orchards. In addition, "Colias eurytheme "butterflies release pheromones, an olfactory cue important for mate selection.


title: Pheromone

text: The effect of Hz-2V virus infection on the reproductive physiology and behavior of female "Helicoverpa zea" moths is that in the absence of males they exhibited calling behavior and called as often but for shorter periods on average than control females. Even after these contacts virus-infected females made many frequent contacts with males and continued to call; they were found to produce five to seven times more pheromone and attracted twice as many males as did control females in flight tunnel experiments.


title: Pheromone

text: Pheromones are also utilized by bee and wasp species. Some pheromones can be used to suppress the sexual behavior of other individuals allowing for a reproductive monopoly – the wasp "R. marginata "uses this. With regard to the "Bombus hyperboreus" species, males, otherwise known as drones, patrol circuits of scent marks (pheromones) to find queens. In particular, pheromones for the "Bombus hyperboreus," include octadecenol, 2,3-dihydro-6-transfarnesol, citronellol, and geranylcitronellol.


title: Pheromone

text: Sea urchins release pheromones into the surrounding water, sending a chemical message that triggers other urchins in the colony to eject their sex cells simultaneously.


title: Pheromone

text: In plants, some homosporous ferns release a chemical called antheridiogen, which affects sex expression. This is very similar to pheromones.


title: Pheromone

text: This classification, based on the effects on behavior, remains artificial. Pheromones fill many additional functions.


title: Pheromone

text: Releaser pheromones are pheromones that cause an alteration in the behavior of the recipient. For example, some organisms use powerful attractant molecules to attract mates from a distance of two miles or more. In general, this type of pheromone elicits a rapid response, but is quickly degraded. In contrast, a primer pheromone has a slower onset and a longer duration. For example, rabbit (mothers) release mammary pheromones that trigger immediate nursing behavior by their babies.


title: Pheromone

text: Primer pheromones trigger a change of developmental events (in which they differ from all the other pheromones, which trigger a change in behavior). They were first described in "Schistocerca gregaria" by Maud Norris in 1954.


title: Pheromone

text: Signal pheromones cause short-term changes, such as the neurotransmitter release that activates a response. For instance, GnRH molecule functions as a neurotransmitter in rats to elicit lordosis behavior.


title: Pheromone

text: The human trace amine-associated receptors are a group of six G protein-coupled receptors (i.e., TAAR1, TAAR2, TAAR5, TAAR6, TAAR8, and TAAR9) that – with exception for TAAR1 – are expressed in the human olfactory epithelium. In humans and other animals, TAARs in the olfactory epithelium function as olfactory receptors that detect volatile amine odorants, including certain pheromones; these TAARs putatively function as a class of pheromone receptors involved in the olfactive detection of social cues.


title: Pheromone

text: A review of studies involving non-human animals indicated that TAARs in the olfactory epithelium can mediate attractive or aversive behavioral responses to a receptor agonist. This review also noted that the behavioral response evoked by a TAAR can vary across species (e.g., TAAR5 mediates attraction to trimethylamine in mice and aversion to trimethylamine in rats). In humans, hTAAR5 presumably mediates aversion to trimethylamine, which is known to act as an hTAAR5 agonist and to possess a foul, fishy odor that is aversive to humans; however, hTAAR5 is not the only olfactory receptor that is responsible for trimethylamine olfaction in humans. hTAAR5-mediated trimethylamine aversion has not been examined in published research.


title: Pheromone

text: In reptiles, amphibia and non-primate mammals pheromones are detected by regular olfactory membranes, and also by the vomeronasal organ (VNO), or Jacobson's organ, which lies at the base of the nasal septum between the nose and mouth and is the first stage of the accessory olfactory system. While the VNO is present in most amphibia, reptiles, and non-primate mammals, it is absent in birds, adult catarrhine monkeys (downward facing nostrils, as opposed to sideways), and apes. An active role for the human VNO in the detection of pheromones is disputed; while it is clearly present in the fetus it appears to be atrophied, shrunk or completely absent in adults. Three distinct families of vomeronasal receptors, putatively pheromone sensing, have been identified in the vomeronasal organ named V1Rs, V2Rs, and V3Rs. All are G protein-coupled receptors but are only distantly related to the receptors of the main olfactory system, highlighting their different role.


title: Pheromone

text: Olfactory processing of chemical signals like pheromones exists in all animal phyla and is thus the oldest of the senses. It has been suggested that it serves survival by generating appropriate behavioral responses to the signals of threat, sex and dominance status among members of the same species.


title: Pheromone

text: Furthermore, it has been suggested that in the evolution of unicellular prokaryotes to multicellular eukaryotes, primordial pheromone signaling between individuals may have evolved to paracrine and endocrine signaling within individual organisms.


title: Pheromone

text: Some authors assume that approach-avoidance reactions in animals, elicited by chemical cues, form the phylogenetic basis for the experience of emotions in humans.


title: Pheromone

text: Mice can distinguish close relatives from more distantly related individuals on the basis of scent signals, which enables them to avoid mating with close relatives and minimizes deleterious inbreeding. Jiménez et al. showed that inbred mice had significantly reduced survival when they were reintroduced into a natural habitat. In addition to mice, two species of bumblebee, in particular Bombus bifarius and Bombus frigidus, have been observed to use pheromones as a means of kin recognition to avoid inbreeding. For example, B. bifarius males display "patrolling" behavior in which they mark specific paths outside their nests with pheromones and subsequently "patrol" these paths. Unrelated reproductive females are attracted to the pheromones deposited by males on these paths, and males that encounter these females while patrolling can mate with them. Other bees of the Bombus species are found to emit pheromones as precopulatory signals, such as "Bombus lapidarius".


title: Pheromone

text: Pheromones of certain pest insect species, such as the Japanese beetle, acrobat ant, and the gypsy moth, can be used to trap the respective insect for monitoring purposes, to control the population by creating confusion, to disrupt mating, and to prevent further egg laying.


title: Pheromone

text: Pheromones are used in the detection of oestrus in sows. Boar pheromones are sprayed into the sty, and those sows that exhibit sexual arousal are known to be currently available for breeding.


title: Pheromone

text: While humans are highly dependent upon visual cues, when in close proximity smells also play a role in sociosexual behaviors. An inherent difficulty in studying human pheromones is the need for cleanliness and odorlessness in human participants. Though various researchers have investigated the possibility of their existence, no pheromonal substance has ever been demonstrated to directly influence human behavior in a peer reviewed study. Experiments have focused on three classes of possible human pheromones: axillary steroids, vaginal aliphatic acids, and stimulators of the vomeronasal organ.


title: Pheromone

text: Axillary steroids are produced by the testes, ovaries, apocrine glands, and adrenal glands. These chemicals are not biologically active until puberty when sex steroids influence their activity. The change in activity during puberty suggest that humans may communicate through odors. Several axillary steroids have been described as possible human pheromones: androstadienol, androstadienone, androstenol, androstenone, and androsterone.


title: Pheromone

text: While it may be expected on evolutionary grounds that humans have pheromones, these three molecules have yet to be rigorously proven to act as such. Research in this field has suffered from small sample sizes, publication bias, false positives, and poor methodology.


title: Pheromone

text: A class of aliphatic acids (volatile fatty acids as a kind of carboxylic acid) was found in female rhesus monkeys that produced six types in the vaginal fluids. The combination of these acids is referred to as "copulins". One of the acids, acetic acid, was found in all of the sampled female's vaginal fluid. Even in humans, one-third of women have all six types of copulins, which increase in quantity before ovulation. Copulins are used to signal ovulation; however, as human ovulation is concealed it is thought that they may be used for reasons other than sexual communication.


title: Pheromone

text: The human vomeronasal organ has epithelia that may be able to serve as a chemical sensory organ; however, the genes that encode the VNO receptors are nonfunctional pseudogenes in humans. Also, while there are sensory neurons in the human VNO there seem to be no connections between the VNO and the central nervous system. The associated olfactory bulb is present in the fetus, but regresses and vanishes in the adult brain. There have been some reports that the human VNO does function, but only responds to hormones in a "sex-specific manner". There also have been pheromone receptor genes found in olfactory mucosa. Unfortunately, there have been no experiments that compare people lacking the VNO, and people that have it. It is disputed on whether the chemicals are reaching the brain through the VNO or other tissues.


title: Pheromone

text: In 2006, it was shown that a second mouse receptor sub-class is found in the olfactory epithelium. Called the trace amine-associated receptors (TAAR), some are activated by volatile amines found in mouse urine, including one putative mouse pheromone. Orthologous receptors exist in humans providing, the authors propose, evidence for a mechanism of human pheromone detection.


title: Pheromone

text: Although there are disputes about the mechanisms by which pheromones function, there is evidence that pheromones do affect humans. Despite this evidence, it has not been conclusively shown that humans have functional pheromones. Those experiments suggesting that certain pheromones have a positive effect on humans are countered by others indicating they have no effect whatsoever.


title: Pheromone

text: A possible theory being studied now is that these axillary odors are being used to provide information about the immune system. Milinski and colleagues found that the artificial odors that people chose are determined in part by their major histocompatibility complexes (MHC) combination. Information about an individual's immune system could be used as a way of "sexual selection" so that the female could obtain good genes for her offspring. Claus Wedekind and colleagues found that both men and women prefer the axillary odors of people whose MHC is different from their own.


title: Pheromone

text: Some body spray advertisers claim that their products contain human sexual pheromones that act as an aphrodisiac. Despite these claims, no pheromonal substance has ever been demonstrated to directly influence human behavior in a peer reviewed study. Thus, the role of pheromones in human behavior remains speculative and controversial.


title: Atomic clock

text: An atomic clock is a clock that measures time by monitoring the resonant frequency of atoms. It is based on atoms having different energy levels. Electron states in an atom are associated with different energy levels, and in transitions between such states they interact with a very specific frequency of electromagnetic radiation. This phenomenon serves as the basis for the International System of Units' (SI) definition of a second:The second, symbol s, is the SI unit of time. It is defined by taking the fixed numerical value of the caesium frequency, formula_1, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be when expressed in the unit Hz, which is equal to s. This definition is the basis for the system of International Atomic Time (TAI), which is maintained by an ensemble of atomic clocks around the world. The system of Coordinated Universal Time (UTC) that is the basis of civil time implements leap seconds to allow clock time to track changes in Earth's rotation to within one second while being based on clocks that are based on the definition of the second.


title: Atomic clock

text: The accurate timekeeping capabilities of atomic clocks are also used for navigation by satellite networks such as the European Union's Galileo Program and the United States' GPS. The timekeeping accuracy of the involved atomic clocks is important because the smaller the error in time measurement, the smaller the error in distance obtained by multiplying the time by the speed of light is (a timing error of a nanosecond or 1 billionth of a second (10 or second) translates into an almost distance and hence positional error).


title: Atomic clock

text: The main variety of atomic clock uses caesium atoms cooled to temperatures that approach absolute zero. The primary standard for the United States, the National Institute of Standards and Technology (NIST)'s caesium fountain clock named NIST-F2, measures time with an uncertainty of 1 second in 300 million years (relative uncertainty ). NIST-F2 was brought online on 3 April 2014.


title: Atomic clock

text: The Scottish physicist James Clerk Maxwell proposed measuring time with the vibrations of light waves in his 1873 Treatise on Electricity and Magnetism: ‘A more universal unit of time might be found by taking the periodic time of vibration of the particular kind of light whose wave length is the unit of length.’ Maxwell argued this would be more accurate than the Earth's rotation, which defines the mean solar second for timekeeping.


title: Atomic clock

text: The accuracy of mechanical, electromechanical and quartz clocks is reduced by temperature fluctuations. This led to the idea of measuring the frequency of an atom's vibrations to keep time much more accurately, as proposed by James Clerk Maxwell, Lord Kelvin, and Isidor Rabi. He proposed the concept in 1945, which led to a demonstration of a clock based on ammonia in 1949. This led to the first practical accurate atomic clock with caesium atoms being built at the National Physical Laboratory in the United Kingdom in 1955by Louis Essen in collaboration with Jack Parry


title: Atomic clock

text: In 1949, Kastler and Brossel developed a technique for making energy level transitions in atoms with light named optical pumping. This technique is useful for creating much stronger magnetic resonance and microwave absorption signals. Unfortunately, this caused a side effect with a light shift of the resonant frequency. Cohen-Tannoudji and others managed and reduced the light shifts to acceptable levels.


title: Atomic clock

text: Ramsey developed a method, commonly known as Ramsey interferometry nowadays, for higher frequencies and narrower resonances in the oscillating fields. Kolsky, Phipps, Ramsey, and Silsbee used this technique for molecular beam spectroscopy in 1950.


title: Atomic clock

text: After 1956, atomic clocks were studied by many groups, such as the National Institute of Standards and Technology (formerly the National Bureau of Standards) in the USA, the Physikalisch-Technische Bundesanstalt (PTB) in Germany, the National Research Council (NRC) in Canada, the National Physical Laboratory in the United Kingdom, International Time Bureau (French: "Bureau International de l'Heure", abbreviated BIH), at the Paris Observatory, the National Radio Company, Bomac, Varian, Hewlett–Packard and Frequency & Time Systems.


title: Atomic clock

text: During the 1950s, the National Radio Company sold more than 50 units of the first atomic clock, the Atomichron. In 1964, engineers at Hewlett-Packard released the 5060 rack-mounted model of caesium clocks.


title: Atomic clock

text: In 1968, the duration of the second was defined to be vibrations of the unperturbed ground-state hyperfine transition frequency of the caesium-133 atom. Prior to that it was defined by there being seconds in the tropical year 1900. The 1968 definition was updated in 2019 to reflect the new definitions of the ampere, kelvin, kilogram, and mole decided upon at the 2019 redefinition of the International System of Units. Timekeeping researchers are currently working on developing an even more stable atomic reference for the second, with a plan to find a more precise definition of the second as atomic clocks improve based on optical clocks or the Rydberg constant around 2030.


title: Atomic clock

text: Optical clocks were first developed in the 2000s. Although optical clocks are not as mature as caesium clocks, considering caesium clocks have been keeping time since the definition of the second in 1960, they are rapidly reaching new levels of accuracy. Optical clocks that are as accurate as the most accurate caesium clocks available, that is with a relative uncertainty of , are now being further developed.


title: Atomic clock

text: The first advance beyond the precision of caesium clocks occurred at NIST in 2010 with the demonstration of a "quantum logic" optical clock that used aluminum ions to achieve a precision of . Optical clocks are a very active area of research in the field of metrology as scientists work to develop clocks based on elements ytterbium, mercury, aluminum, and strontium. Scientists at JILA demonstrated a strontium clock with a frequency precision of in 2015. Scientists at NIST developed a quantum logic clock that measured a single aluminum ion in 2019 with a frequency uncertainty of . At JILA in September 2021, scientists demonstrated an optical strontium clock with a frequency differential precision of . The second is expected to be redefined when the field of optical clocks matures, sometime around the year 2026 or 2030. In order for this to occur, optical clocks must be capable of measuring time to very high precision consistently. In addition, methods for reliably and accurately comparing different optical clocks around the world in national metrology labs must be demonstrated.


title: Atomic clock

text: Technological developments such as lasers and optical frequency combs in the 1990s led to increasing accuracy of atomic clocks. Lasers enable the possibility of optical-range control over atomic states transitions, which has a much higher frequency than that of microwaves; while optical frequency comb measures highly accurately such high frequency oscillation in light.


title: Atomic clock

text: In addition to increased accuracy, the development of chip scale atomic clocks has expanded the number of places atomic clocks can be used. In August 2004, NIST scientists demonstrated a chip-scale atomic clock that was 100 times smaller than an ordinary atomic clock and had a much smaller power consumption of . The atomic clock was about the size of a grain of rice with a frequency of about 9 GHz. This technology became available commercially in 2011. Atomic clocks on the scale of one chip require less than 30 milliwatts of power.


title: Atomic clock

text: The National Institute of Standards and Technology created a program NIST on a chip to develop compact ways of measuring time with a device just a few millimeters across.


title: Atomic clock

text: Metrologists are currently (2022) designing atomic clocks that implement new developments such as ion traps, and optical combs to reach greater accuracies.


title: Atomic clock

text: An atomic clock is based on a system of atoms which may be in one of two possible energy states. A group of atoms in one state is prepared, then subjected to microwave radiation. If the radiation is of the correct frequency, a number of atoms will transition to the other energy state. The closer the frequency is to the inherent oscillation frequency of the atoms, the more atoms will switch states. Such correlation allows very accurate tuning of the frequency of the microwave radiation. Once the microwave radiation is adjusted to a known frequency where the maximum number of atoms switch states, the atom and thus, its associated transition frequency, can be used as a timekeeping oscillator to measure elapsed time.


title: Atomic clock

text: A number of national metrology laboratories maintain atomic clocks: including Paris Observatory, the Physikalisch-Technische Bundesanstalt (PTB) in Germany, the National Institute of Standards and Technology (NIST) in Colorado and Maryland, USA, JILA in the University of Colorado Boulder, the National Physical Laboratory (NPL) in the United Kingdom, and the All-Russian Scientific Research Institute for Physical-Engineering and Radiotechnical Metrology. They do this by designing and building frequency standards that produce electric oscillations at a frequency whose relationship to the transition frequency of caesium 133 is known, in order to achieve a very low uncertainty. These primary frequency standards estimate and correct various frequency shifts, including relativistic Doppler shifts linked to atomic motion, the thermal radiation of the environment (blackbody shift) and several other factors. The best primary standards currently produce the SI second with an accuracy approaching an uncertainty of one part in .


title: Atomic clock

text: It is important to note that at this level of accuracy, the differences in the gravitational field in the device cannot be ignored. The standard is then considered in the framework of general relativity to provide a proper time at a specific point.


title: Atomic clock

text: The International Bureau of Weights and Measures (BIPM) provides a list of frequencies that serve as secondary representations of the second. This list contains the frequency values and respective standard uncertainties for the rubidium microwave transition and other optical transitions, including neutral atoms and single trapped ions. These secondary frequency standards can be as accurate as one part in ; however, the uncertainties in the list are one part in –. This is because the uncertainty in the central caesium standard against which the secondary standards are calibrated is one part in –.


title: Atomic clock

text: Primary frequency standards can be used to calibrate the frequency of other clocks used in national laboratories. These are usually commercial caesium clocks having very good long-term frequency stability, maintaining a frequency with a stability better than 1 part in over a few months. The uncertainty of the primary standard frequencies is around one part in .


title: Atomic clock

text: Hydrogen masers, which rely on the 1.4 GHz hyperfine transition in atomic hydrogen, are also used in time metrology laboratories. Masers outperform any commercial caesium clock in terms of short-term frequency stability. In the past, these instruments have been used in all applications that require a steady reference across time periods of less than one day (frequency stability of about 1 part in ten for averaging times of a few hours). Because some active hydrogen masers have a modest but predictable frequency drift with time, they have become an important part of the BIPM's ensemble of commercial clocks that implement International Atomic Time.


title: Atomic clock

text: The time readings of clocks operated in metrology labs operating with the BIPM need to be known very accurately. Some operations require synchronization of atomic clocks separated by great distances over thousands of kilometers. Global Navigational Satellite Systems (GNSS) provide a satisfactory solution to the problem of time transfer. Atomic clocks are used to broadcast time signals in the United States Global Positioning System (GPS), the Russian Federation's Global Navigation Satellite System (GLONASS), the European Union's Galileo system and China's BeiDou system.


title: Atomic clock

text: The signal received from one satellite in a metrology laboratory equipped with a receiver with an accurately known position allows the time difference between the local time scale and the GNSS system time to be determined with an uncertainty of a few nanoseconds when averaged over 15 minutes. Receivers allow the simultaneous reception of signals from several satellites, and make use of signals transmitted on two frequencies. As more satellites are launched and start operations, time measurements will become more accurate.


title: Atomic clock

text: These methods of time comparison must make corrections for the effects of special relativity and general relativity of a few nanoseconds.


title: Atomic clock

text: National laboratories usually operate a range of clocks. These are operated independently of one another and their measurements are sometimes combined to generate a scale that is more stable and more accurate than that of any individual contributing clocks. This scale allows for time comparisons between different clocks in the laboratory. These atomic time scales are generally referred to as TA(k) for laboratory k.


title: Atomic clock

text: Coordinated Universal Time (UTC) is the result of comparing clocks in national laboratories around the world to International Atomic Time (TAI), then adding leap seconds as necessary. TAI is a weighted average of around 450 clocks in some 80 time institutions. The relative stability of TAI is around one part in .


title: Atomic clock

text: Before TAI is published, the frequency of the result is compared with the SI second at various primary and secondary frequency standards. This requires relativistic corrections to be applied to the location of the primary standard which depend on the distance between the equal gravity potential and the rotating geoid of Earth. These corrections are about 1 part for every meters of altitude. The values of the rotating geoid and the TAI change slightly each month and are available in the BIPM Circular T publication. The TAI time-scale is deferred by a few weeks as the average of atomic clocks around the world is calculated.


title: Atomic clock

text: TAI is not distributed in everyday timekeeping. Instead, an integer number of leap seconds are added or subtracted to correct for the Earth's rotation, producing UTC. The number of leap seconds is changed so that mean solar noon at the Greenwich meridian does not deviate from UTC noon by more than 0.9 seconds.


title: Atomic clock

text: National metrology institutions maintain an approximation of UTC referred to as UTC(k) for laboratory k. UTC(k) is distributed by the BIPM's Consultative Committee for Time and Frequency. The offset UTC-UTC(k) is calculated every 5 days, the results are published monthly. Atomic clocks record UTC(k) to no more than 100 nanoseconds. In some countries, UTC(k) is the legal time that is distributed by radio, television, telephone, Internet, fiber-optic cables, time signal transmitters, and speaking clocks. In addition, GNSS provides time information accurate to a few tens of nanoseconds or better.


title: Atomic clock

text: The SI second is defined as a certain number of unperturbed ground-state hyperfine transitions of the caesium-133 atom. Caesium standards are therefore regarded as primary time and frequency standards.


title: Atomic clock

text: Caesium clocks include the NIST-F1 clock, developed in 1999, and the NIST-F2 clock, developed in 2013.


title: Atomic clock

text: Caesium has several properties that make it a good choice for an atomic clock. Whereas a hydrogen atom moves at 1,600 m/s at room temperature and a nitrogen atom moves at 510 m/s, a caesium atom moves at a much slower speed of 130 m/s due to its greater mass. The hyperfine frequency of caesium (~9.19 GHz) is also higher than other elements such as rubidium (~6.8 GHz) and hydrogen (~1.4 GHz). The high frequency of caesium allows for more accurate measurements. Caesium reference tubes suitable for national standards currently last about seven years and cost about US$35,000. Primary frequency and time standards like the United States Time Standard atomic clocks, NIST-F1 and NIST-F2, use far higher power.


title: Atomic clock

text: The BIPM defines the unperturbed ground-state hyperfine transition frequency of the rubidium-87 atom, 6 834 682 610.904 312 6 Hz, in terms of the caesium standard frequency. Atomic clocks based on rubidium standards are therefore regarded as secondary representations of the second.


title: Atomic clock

text: Rubidium standard clocks are prized for their low cost, small size (commercial standards are as small as ) and short-term stability. They are used in many commercial, portable and aerospace applications. Modern rubidium standard tubes last more than ten years, and can cost as little as US$50. Some commercial applications use a rubidium standard periodically corrected by a global positioning system receiver (see GPS disciplined oscillator). This achieves excellent short-term accuracy, with long-term accuracy equal to (and traceable to) the US national time standards.


title: Atomic clock

text: The BIPM defines the unperturbed optical transition frequency of the hydrogen-1 neutral atom, 1 233 030 706 593 514 Hz, in terms of the caesium standard frequency. Atomic clocks based on hydrogen standards are therefore regarded as secondary representations of the second.


title: Atomic clock

text: Hydrogen masers have superior short-term stability compared to other standards, but lower long-term accuracy. The long-term stability of hydrogen maser standards decreases because of changes in the cavity's properties over time. The relative error of hydrogen masers is 5 × 10 for periods of 1000 seconds. This makes hydrogen masers good for radio astronomy, in particular for very long baseline interferometry. Hydrogen masers are used for flywheel oscillators in laser-cooled atomic frequency standards and broadcasting time signals from national standards laboratories, although they need to be corrected as they drift from the correct frequency over time. The hydrogen maser is also useful for experimental tests of the effects of special relativity and general relativity such as gravitational red shift.


title: Atomic clock

text: Since 1968, the SI has defined the second as the duration of of radiation corresponding to the transition between two energy levels of the ground state of the caesium-133 atom. In 1997, the International Committee for Weights and Measures (CIPM) added that the preceding definition refers to a caesium atom at rest at a temperature of absolute zero.


title: Atomic clock

text: This definition makes the caesium oscillator the primary standard for time and frequency measurements, called the caesium standard. Following the 2019 redefinition of the SI base units, the definition of every base unit except the mole and almost every derived unit relies on the definition of the second.


title: Atomic clock

text: In this particular design (see simplified block diagram), the time-reference of an atomic clock consists of a quartz clock oscillating at microwave frequency. The oscillator is arranged so that its frequency-determining components include an element that can be controlled by a feedback signal. The feedback signal keeps the oscillator tuned in resonance with the frequency of the hyperfine transition.


title: Atomic clock

text: The core of the radio frequency atomic clock is a tunable microwave cavity containing a gas. In a hydrogen maser clock the gas emits microwaves (the gas "mases") on a hyperfine transition, the field in the cavity oscillates, and the cavity is tuned for maximum microwave amplitude. Alternatively, in a caesium or rubidium clock, the beam or gas absorbs microwaves and the cavity contains an electronic amplifier to make it oscillate. For both types, the atoms in the gas are prepared in one hyperfine state prior to filling them into the cavity. For the second type, the number of atoms that change hyperfine state is detected and the cavity is tuned for a maximum of detected state changes.


title: Atomic clock

text: Most of the complexity of the clock lies in this adjustment process. The adjustment tries to correct for unwanted side-effects, such as frequencies from other electron transitions, temperature changes, and the spreading in frequencies caused by the vibration of molecules including Doppler broadening. One way of doing this is to sweep the microwave oscillator's frequency across a narrow range to generate a modulated signal at the detector. The detector's signal can then be demodulated to apply feedback to control long-term drift in the radio frequency. In this way, the quantum-mechanical properties of the atomic transition frequency of the caesium can be used to tune the microwave oscillator to the same frequency, except for a small amount of experimental error. When a clock is first turned on, it takes a while for the oscillator to stabilize. In practice, the feedback and monitoring mechanism is much more complex.


title: Atomic clock

text: All timekeeping devices use oscillatory phenomena to accurately measure time, whether it is the rotation of the Earth for a sundial, the swinging of a pendulum in a grandfather clock, the vibrations of springs and gears in a watch, or voltage changes in a quartz crystal watch. However all of these are easily affected by temperature changes and are not very accurate. The most accurate clocks use atomic vibrations to keep track of time. Clock transition states in atoms are insensitive to temperature and other environmental factors and the vibrational frequency is much higher than any of the other clocks (in microwave frequency regime and higher). One of the most important factors in a clock's performance is the atomic line quality factor, Q, which is defined as the ratio of the absolute frequency formula_2 of the resonance to the linewidth of the resonance itself formula_3. Atomic resonance has a much higher Q than mechanical devices. Atomic clocks can also be isolated from environmental effects to a much higher degree. Atomic clocks have the benefit that atoms are universal, which means that the oscillation frequency is also universal. This is different from quartz and mechanical time measurement devices that do not have a universal frequency.


title: Atomic clock

text: A clock's quality can be specified by two parameters: uncertainty and stability. Uncertainty is a measurement of the degree to which the clock's ticking rate stays constant without speeding up or slowing down. Stability is a measurement of how the clock performs over time when measurements are averaged related to precision.


title: Atomic clock

text: The instability of a clock is specified by the equation: formula_4 where formula_3 is the spectroscopic linewidth of the clock system, formula_6 is the number of atoms or ions used in a single measurement, formula_7 is the time required for one cycle, and formula_8 is the averaging period. This means instability is smaller when the linewidth formula_3 is smaller and when formula_10 is the signal to noise ratio is larger. The stability improves as the time formula_8 over which the measurements are averaged increases from seconds to hours to days. The stability is most heavily affected by the oscillator frequency formula_3. This is why optical clocks such as strontium clocks (429 terahertz) are much more accurate than caesium clocks (9.19 GHz).


title: Atomic clock

text: The accuracy of atomic clocks has improved continuously since the first prototype in the 1950s. The first generation of atomic clocks were based on measuring caesium, rubidium, and hydrogen atoms. In a time period from 1959 to 1998, NIST developed a series of seven caesium-133 microwave clocks named NBS-1 to NBS-6 and NIST-7 after the agency changed its name from the National Bureau of Standards to the National Institute of Standards and Technology. The first clock had an accuracy of , and the last clock had an accuracy of . The clocks were the first to use a caesium fountain, which was introduced by Jerrod Zacharias, and laser cooling of atoms, which was demonstrated by Dave Wineland and his colleagues in 1978.


title: Atomic clock

text: The next step in atomic clock advances involves going from accuracies of to accuracies of and even . The goal is to redefine the second when clocks become so accurate that they will not lose or gain more than a second in the age of the universe. To do so, scientists must demonstrate the accuracy of clocks that use strontium and ytterbium and optical lattice technology. Such clocks are also called optical clocks where the energy level transitions used are in the optical regime (giving rise to even higher oscillation frequency), which thus, have much higher accuracy as compared to traditional atomic clocks.


title: Atomic clock

text: The goal of an atomic clock with accuracy was first reached at the United Kingdom's National Physical Laboratory's NPL-CsF2 caesium fountain clock and the United States' NIST-F2. The increase in precision from NIST-F1 to NIST-F2 is due to advances in liquid nitrogen cooling technology for atoms.


title: Atomic clock

text: The performance of primary and secondary frequency standards contributing to International Atomic Time (TAI) is evaluated. The evaluation reports of individual (mainly primary) clocks are published online by the International Bureau of Weights and Measures (BIPM).


title: Atomic clock

text: Most research focuses on the often conflicting goals of making the clocks smaller, cheaper, more portable, more energy efficient, more accurate, more stable and more reliable.


title: Atomic clock

text: The Cold Atom Clock Experiment in Space (CACES) testing a Cold Atom Clock in Earth orbit in microgravity conditions and the Atomic Clock Ensemble in Space are examples of clock research.


title: Atomic clock

text: A list of frequencies recommended for secondary representations of the second is maintained by the International Bureau of Weights and Measures (BIPM) since 2006 and is available online. The list contains the frequency values and the respective standard uncertainties for the rubidium microwave transition and for several optical transitions. These secondary frequency standards are accurate at the level of ; however, the uncertainties provided in the list are in the range – since they are limited by the linking to the caesium primary standard that currently (2018) defines the second.


title: Atomic clock

text: Twenty-first century experimental atomic clocks that provide non-caesium-based secondary representations of the second are becoming so precise that they are likely to be used as extremely sensitive detectors for other things besides measuring frequency and time. For example, the frequency of atomic clocks is altered slightly by gravity, magnetic fields, electrical fields, force, motion, temperature and other phenomena. The experimental clocks tend to continue to improve, and leadership in performance has shifted back and forth between various types of experimental clocks.


title: Atomic clock

text: In March 2008, physicists at NIST described a quantum logic clock based on individual ions of beryllium and aluminium. This clock was compared to NIST's mercury ion clock. These were the most accurate clocks that had been constructed, with neither clock gaining nor losing time at a rate that would exceed a second in over a billion years. In February 2010, NIST physicists described a second, enhanced version of the quantum logic clock based on individual ions of magnesium and aluminium. Considered the world's most precise clock in 2010 with a fractional frequency inaccuracy of , it offers more than twice the precision of the original. In July 2019, NIST scientists demonstrated such an Al quantum logic clock with total uncertainty of , which is the first demonstration of such a clock with uncertainty below .


title: Atomic clock

text: The accuracy of experimental quantum clocks has since been superseded by experimental optical lattice clocks based on strontium-87 and ytterbium-171.


title: Atomic clock

text: One theoretical possibility for improving the performance of atomic clocks is to use a "nuclear" energy transition (between different nuclear isomers) rather than the atomic electron transitions which current atomic clocks measure. Most nuclear transitions operate at far too high a frequency to be measured, but in 2003, Ekkehard Peik and Christian Tamm noted that the exceptionally low excitation energy of is within reach of current frequency-measurement techniques, making a clock possible. In 2012, it was shown that a nuclear clock based on a single ion could provide a total fractional frequency inaccuracy of , which is better than existing 2019 atomic clock technology. Although it remains an unrealized theoretical possibility, significant progress toward the development of an experimental nuclear clock has been made.


title: Atomic clock

text: In June 2015, the National Physical Laboratory (NPL) in Teddington, UK; the French department of Time-Space Reference Systems at the Paris Observatory (LNE-SYRTE); the German German National Metrology Institute (PTB) in Braunschweig; and Italy's Istituto Nazionale di Ricerca Metrologica (INRiM) in Turin labs have started tests to improve the accuracy of current state-of-the-art satellite comparisons by a factor of 10, but it will still be limited to one part in . These four European labs are developing and host a variety of experimental optical clocks that harness different elements in different experimental set-ups and want to compare their optical clocks against each other and check whether they agree. In a next phase, these labs strive to transmit comparison signals in the visible spectrum through fibre-optic cables. This will allow their experimental optical clocks to be compared with an accuracy similar to the expected accuracies of the optical clocks themselves. Some of these labs have already established fibre-optic links, and tests have begun on sections between Paris and Teddington, and Paris and Braunschweig. Fibre-optic links between experimental optical clocks also exist between the American NIST lab and its partner lab JILA, both in Boulder, Colorado but these span much shorter distances than the European network and are between just two labs. According to Fritz Riehle, a physicist at PTB, "Europe is in a unique position as it has a high density of the best clocks in the world".


title: Atomic clock

text: In August 2016 the French LNE-SYRTE in Paris and the German PTB in Braunschweig reported the comparison and agreement of two fully independent experimental strontium lattice optical clocks in Paris and Braunschweig at an uncertainty of via a newly established phase-coherent frequency link connecting Paris and Braunschweig, using of telecom fibre-optic cable. The fractional uncertainty of the whole link was assessed to be , making comparisons of even more accurate clocks possible.


title: Atomic clock

text: In 2021, NIST compared transmission of signals from a series of experimental atomic clocks located about apart at the NIST lab, its partner lab JILA, and the University of Colorado all in Boulder, Colorado over air and fiber optic cable to a precision of .


title: Atomic clock

text: The idea of trapping atoms in an optical lattice using lasers was proposed by Russian physicist Vladilen Letokhov in the 1960s. The theoretical move from microwaves as the atomic "escapement" for clocks to light in the optical range (harder to measure but offering better performance) earned John L. Hall and Theodor W. Hänsch the Nobel Prize in Physics in 2005. One of 2012's Physics Nobelists, David J. Wineland, is a pioneer in exploiting the properties of a single ion held in a trap to develop clocks of the highest stability. The first optical clock was started at NIST in 2000 and finished in 2006.


title: Atomic clock

text: The development of femtosecond frequency combs, optical lattices has led to a new generation of atomic clocks. These clocks are based on atomic transitions that emit visible light instead of microwaves. A major obstacle to developing an optical clock is the difficulty of directly measuring optical frequencies. This problem has been solved with the development of self-referenced mode-locked lasers, commonly referred to as femtosecond frequency combs. Before the demonstration of the frequency comb in 2000, terahertz techniques were needed to bridge the gap between radio and optical frequencies, and the systems for doing so were cumbersome and complicated. With the refinement of the frequency comb, these measurements have become much more accessible and numerous optical clock systems are now being developed around the world.


title: Atomic clock

text: As in the radio range, absorption spectroscopy is used to stabilize an oscillator—in this case, a laser. When the optical frequency is divided down into a countable radio frequency using a femtosecond comb, the bandwidth of the phase noise is also divided by that factor. Although the bandwidth of laser phase noise is generally greater than stable microwave sources, after division it is less.


title: Atomic clock

text: These techniques allow the atoms or ions to be highly isolated from external perturbations, thus producing an extremely stable frequency reference. Lasers and magneto-optical traps are used to cool the atoms for improved precision.


title: Atomic clock

text: Atomic systems under consideration include Al, Hg, Hg, Sr, Sr, In, Mg, Ca, Ca, Yb, Yb and Th. The color of a clock's electromagnetic radiation depends on the element that is simulated. For example, calcium optical clocks resonate when red light is produced, and ytterbium clocks resonate in the presence of violet light.


title: Atomic clock

text: The rare-earth element ytterbium (Yb) is valued not so much for its mechanical properties but for its complement of internal energy levels. "A particular transition in Yb atoms, at a wavelength of 578 nm, currently provides one of the world's most accurate optical atomic frequency standards," said Marianna Safronova. The estimated uncertainty achieved corresponds to about one second over the lifetime of the universe so far, 15 billion years, according to scientists at the Joint Quantum Institute (JQI) and the University of Delaware in December 2012.


title: Atomic clock

text: In 2013 optical lattice clocks (OLCs) were shown to be as good as or better than caesium fountain clocks. Two optical lattice clocks containing about of strontium-87 were able to stay in synchrony with each other at a precision of at least , which is as accurate as the experiment could measure. These clocks have been shown to keep pace with all three of the caesium fountain clocks at the Paris Observatory. There are two reasons for the possibly better precision. Firstly, the frequency is measured using light, which has a much higher frequency than microwaves, and secondly, by using many atoms, any errors are averaged. Using ytterbium-171 atoms, a new record for stability with a precision of over a 7-hour period was published on 22 August 2013. At this stability, the two optical lattice clocks working independently from each other used by the NIST research team would differ less than a second over the age of the universe (); this was better than previous experiments. The clocks rely on atoms cooled to and trapped in an optical lattice. A laser at excites the atoms between two of their energy levels. Having established the stability of the clocks, the researchers are studying external influences and evaluating the remaining systematic uncertainties, in the hope that they can bring the clock's accuracy down to the level of its stability. An improved optical lattice clock was described in a 2014 Nature paper. In 2015 JILA evaluated the absolute frequency uncertainty of a strontium-87 optical lattice clock at , which corresponds to a measurable gravitational time dilation for an elevation change of on planet Earth that according to JILA/NIST Fellow Jun Ye is "getting really close to being useful for relativistic geodesy". At this frequency uncertainty, this JILA optical lattice clock is expected to neither gain nor lose a second in more than 15 billion years.


title: Atomic clock

text: In 2017 JILA reported an experimental 3D quantum gas strontium optical lattice clock in which strontium-87 atoms are packed into a tiny three-dimensional (3-D) cube at 1,000 times the density of previous one-dimensional (1-D) clocks, such as the 2015 JILA clock. A synchronous clock comparison between two regions of the 3D lattice yielded a record level of synchronization of in 1 hour of averaging time. The 3D quantum gas strontium optical lattice clock's centerpiece is an unusual state of matter called a degenerate Fermi gas (a quantum gas for Fermi particles). The experimental data shows the 3D quantum gas clock achieved a precision of in about two hours. According to Jun Ye "This represents a significant improvement over any previous demonstrations." Ye further commented "The most important potential of the 3D quantum gas clock is the ability to scale up the atom numbers, which will lead to a huge gain in stability." and "The ability to scale up both the atom number and coherence time will make this new-generation clock qualitatively different from the previous generation." In 2018 JILA reported the 3D quantum gas clock reached a frequency precision of over 6 hours. At this frequency uncertainty, this 3D quantum gas clock would lose or gain about 0.1 seconds over the age of the universe. Recently it has been proved that the quantum entanglement can help to further enhance the clock stability. In 2020 optical clocks were researched for space applications like future generations of global navigation satellite systems (GNSSs) as replacements for microwave based clocks.


title: Atomic clock

text: In February 2022, scientists at the University of Wisconsin-Madison reported a “multiplexed” optical atomic clock, where individual clocks deviated from each other with an accuracy equivalent to losing a second in 300 billion years. The reported minor deviation is explainable as the concerned clock oscillators are in slightly different environments. These are causing differing reactions to gravity, magnetic fields, or other conditions. This miniaturized clock network approach is novel in that it uses an optical lattice of strontium atoms and a configuration of six clocks that can be used to demonstrate relative stability, fractional uncertainty between clocks and methods for ultra-high-precision comparisons between optical atomic clock ensembles that are located close together in a metrology facility.


title: Atomic clock

text: Optical clocks are currently (2022) still primarily research projects, less mature than rubidium and caesium microwave standards, which regularly deliver time to the International Bureau of Weights and Measures (BIPM) for establishing International Atomic Time (TAI). As the optical experimental clocks move beyond their microwave counterparts in terms of accuracy and stability performance, this puts them in a position to replace the current standard for time, the caesium fountain clock. In the future this might lead to redefining the caesium microwave-based SI second, and other new dissemination techniques at the highest level of accuracy to transfer clock signals will be required that can be used in both shorter-range and longer-range (frequency) comparisons between better clocks and to explore their fundamental limitations without significantly compromising their performance. The BIPM reported in December 2021 based on the progress of optical standards contributing to TAI the Consultative Committee for Time and Frequency (CCTF) initiated work towards a redefinition of the second expected during the 2030s.


title: Atomic clock

text: The most accurate caesium clocks based on the caesium frequency of 9.19 GHz have an accuracy between 10–10. Unfortunately, they are big and only available in large metrology labs and not useful for factories or industrial environments that would use an atomic clock for GPS accuracy but can't afford to build a whole metrology laboratory for one atomic clock. Researchers have designed a strontium optical clock that can be moved around in an air-conditioned car trailer.


title: Atomic clock

text: In 2022, the best realisation of the second is done with caesium primary standard clocks such as IT-CsF2, NIST-F2, NPL-CsF2, PTB-CSF2, SU–CsFO2 or SYRTE-FO2. These clocks work by laser-cooling a cloud of caesium atoms to a microkelvin in a magneto-optic trap. These cold atoms are then launched vertically by laser light. The atoms then undergo Ramsey excitation in a microwave cavity. The fraction of excited atoms are then detected by laser beams. These clocks have systematic uncertainty, which is equivalent to 50 picoseconds per day. A system of several fountains worldwide contributes to International Atomic Time. These caesium clocks also underpin optical frequency measurements.


title: Atomic clock

text: The advantage of optical clocks can be explained by the statement that the instability formula_13 , where formula_14 is the instability, f is the frequency, and "S"/"N" is the signal-to-noise ratio. This leads to the equation formula_15.


title: Atomic clock

text: Optical clocks are based on forbidden optical transitions in ions or atoms. They have frequencies around , with a natural linewidth formula_16 of typically 1 Hz, so the Q-factor is about , or even higher. They have better stabilities than microwave clocks, which means that they can facilitate evaluation of lower uncertainties. They also have better time resolution, which means the clock "ticks" faster. Optical clocks use either a single ion, or an optical lattice with – atoms.


title: Atomic clock

text: A definition based on the Rydberg constant would involve fixing the value to a certain value: formula_17. The Rydberg constant describes the energy levels in a hydrogen atom with the nonrelativistic approximation formula_18.


title: Atomic clock

text: The only viable way to fix the Rydberg constant involves trapping and cooling hydrogen. Unfortunately, this is difficult because it is very light and the atoms move very fast, causing Doppler shifts. The radiation needed to cool the hydrogen —— is also difficult. Another hurdle involves improving the uncertainty in quantum electrodynamics/QED calculations.


title: Atomic clock

text: A redefinition must include improved optical clock reliability. TAI must be contributed to by optical clocks before the BIPM affirms a redefinition. A consistent method of sending signals, such as fiber-optics, must be developed before the second is redefined.


title: Atomic clock

text: The development of atomic clocks has led to many scientific and technological advances such as precise global and regional navigation satellite systems, and applications in the Internet, which depend critically on frequency and time standards. Atomic clocks are installed at sites of time signal radio transmitters. They are used at some long-wave and medium-wave broadcasting stations to deliver a very precise carrier frequency. Atomic clocks are used in many scientific disciplines, such as for long-baseline interferometry in radio astronomy.


title: Atomic clock

text: The Global Positioning System (GPS) operated by the United States Space Force provides very accurate timing and frequency signals. A GPS receiver works by measuring the relative time delay of signals from a minimum of four, but usually more, GPS satellites, each of which has at least two onboard caesium and as many as two rubidium atomic clocks. The relative times are mathematically transformed into three absolute spatial coordinates and one absolute time coordinate. GPS Time (GPST) is a continuous time scale and theoretically accurate to about 14 nanoseconds. However, most receivers lose accuracy in the interpretation of the signals and are only accurate to 100 nanoseconds. GPST is related to but differs from TAI (International Atomic Time) and UTC (Coordinated Universal Time). GPST remains at a constant offset from TAI (TAI – GPST = 19 seconds) and like TAI does not implement leap seconds. Periodic corrections are performed to the on-board clocks in the satellites to keep them synchronized with ground clocks. The GPS navigation message includes the difference between GPST and UTC. As of July 2015, GPST is 17 seconds ahead of UTC because of the leap second added to UTC on 30 June 2015. Receivers subtract this offset from GPS Time to calculate UTC.


title: Atomic clock

text: The GLObal NAvigation Satellite System (GLONASS) operated by the Russian Aerospace Defence Forces provides an alternative to the Global Positioning System (GPS) system and is the second navigational system in operation with global coverage and of comparable precision. GLONASS Time (GLONASST) is generated by the GLONASS Central Synchroniser and is typically better than 1,000 nanoseconds. Unlike GPS, the GLONASS time scale implements leap seconds, like UTC.


title: Atomic clock

text: The Galileo Global Navigation Satellite System is operated by the European GNSS Agency and European Space Agency. Galileo started offering global Early Operational Capability (EOC) on 15 December 2016, providing the third, and first non-military operated, global navigation satellite system. Galileo System Time (GST) is a continuous time scale which is generated on the ground at the Galileo Control Centre in Fucino, Italy, by the Precise Timing Facility, based on averages of different atomic clocks and maintained by the Galileo Central Segment and synchronised with TAI with a nominal offset below 50 nanoseconds. According to the European GNSS Agency Galileo offers 30 nanoseconds timing accuracy. The March 2018 Quarterly Performance Report by the European GNSS Service Centre reported the UTC Time Dissemination Service Accuracy was ≤ 7.6 nanoseconds, computed by accumulating samples over the previous 12 months, and exceeding the ≤ 30 ns target. Each Galileo satellite has two passive hydrogen maser and two rubidium atomic clocks for onboard timing. The Galileo navigation message includes the differences between GST, UTC and GPST (to promote interoperability). In the summer of 2021, the European Union settled on a passive hydrogen maser for the second generation of Galileo satellites, starting in 2023, with an expected lifetime of 12 years per satellite. The masers are about 2 feet long with a weight of 40 pounds.


title: Atomic clock

text: The BeiDou-2/BeiDou-3 satellite navigation system is operated by the China National Space Administration. BeiDou Time (BDT) is a continuous time scale starting at 1 January 2006 at 0:00:00 UTC and is synchronised with UTC within 100 ns. BeiDou became operational in China in December 2011, with 10 satellites in use, and began offering services to customers in the Asia-Pacific region in December 2012. On 27 December 2018 the BeiDou Navigation Satellite System started to provide global services with a reported timing accuracy of 20 ns. The final, 35th, BeiDou-3 satellite for global coverage was launched into orbit on 23 June 2020.


title: Atomic clock

text: In April 2015, NASA announced that it planned to deploy a Deep Space Atomic Clock (DSAC), a miniaturized, ultra-precise mercury-ion atomic clock, into outer space. NASA said that the DSAC would be much more stable than other navigational clocks. The clock was successfully launched on 25 June 2019, activated on 23 August 2019 and deactivated two years later on 18 September 2021.


title: Atomic clock

text: In 2022, DARPA announced a drive to upgrade to the U.S. military timekeeping systems for greater precision over time when sensors do not have access to GPS satellites, with a plan to reach precision of 1 part in . The Robust Optical Clock Network will balance usability and accuracy as it is developed over 4 years.


title: Atomic clock

text: A radio clock is a clock that automatically synchronizes itself by means of radio time signals received by a radio receiver. Some manufacturers may label radio clocks as atomic clocks because the radio signals they receive originate from atomic clocks. Normal low-cost consumer-grade receivers that rely on the amplitude-modulated time signals have a practical accuracy uncertainty of ± 0.1 second. This is sufficient for many consumer applications. Instrument grade time receivers provide higher accuracy. Radio clocks incur a propagation delay of approximately 1 ms for every 300 kilometres (186 mi) of distance from the radio transmitter. Many governments operate transmitters for timekeeping purposes.


title: Atomic clock

text: General relativity predicts that clocks tick slower deeper in a gravitational field. Atomic clocks are effective at testing general relativity on smaller and smaller scales. A project to observe 12 atomic clocks from 11 November 1999 to October 2014 resulted in a further demonstration that Einstein's theory of general relativity is accurate at small scales. In 2021 a team of scientists at JILA measured the difference in the passage of time due to gravitational redshift between two layers of atoms separated by 1 millimeter using a strontium optical clock cooled to 100 nanokelvin with a precision of seconds. Given its quantum nature and the fact that time is a relativistic quantity, atomic clocks can also be used to see how time is influenced by general relativity and quantum mechanics at the same time.


title: Atomic clock

text: Atomic clocks keep accurate records of transactions between buyers and sellers to the millisecond or better, particularly in high-frequency trading. Accurate timekeeping is needed to prevent illegal trading ahead of time, in addition to ensuring fairness to traders on the other side of the globe. The current system known as NTP is only accurate to a millisecond.


title: Deontology

text: In moral philosophy, deontological ethics or deontology (from Greek: + ) is the normative ethical theory that the morality of an action should be based on whether that action itself is right or wrong under a series of rules and principles, rather than based on the consequences of the action. It is sometimes described as duty-, obligation-, or rule-based ethics. Deontological ethics is commonly contrasted to consequentialism, virtue ethics, and pragmatic ethics. In this terminology, action is more important than the consequences.


title: Deontology

text: The term "deontological" was first used to describe the current, specialised definition by C. D. Broad in his 1930 book, "Five Types of Ethical Theory". Older usage of the term goes back to Jeremy Bentham, who coined it prior to 1816 as a synonym of "dicastic" or "censorial ethics" (i.e., ethics based on judgement). The more general sense of the word is retained in French, especially in the term "code de déontologie" (ethical code), in the context of professional ethics.


title: Deontology

text: Depending on the system of deontological ethics under consideration, a "moral obligation" may arise from an external or internal source, such as a set of rules inherent to the universe (ethical naturalism), religious law, or a set of personal or cultural values (any of which may be in conflict with personal desires).


title: Deontology

text: Immanuel Kant's theory of ethics is considered deontological for several different reasons. First, Kant argues that in order to act in the morally right way, people must act from duty ("Pflicht"). Second, Kant argued that it was not the consequences of actions that make them right or wrong, but the motives of the person who carries out the action.


title: Deontology

text: Kant's first argument begins with the premise that the highest good must be both good in itself and good without qualification. Something is "good in itself" when it is intrinsically good; and is "good without qualification" when the addition of that thing never makes a situation ethically worse. Kant then argues that those things that are usually thought to be good, such as intelligence, perseverance, and pleasure, fail to be either intrinsically good or good without qualification. Pleasure, for example, appears not to be good without qualification, because when people take pleasure in watching someone suffer, this seems to make the situation ethically worse. He concludes that there is only one thing that is truly good:


title: Deontology

text: Kant then argues that the consequences of an act of willing cannot be used to determine that the person has a good will; good consequences could arise by accident from an action that was motivated by a desire to cause harm to an innocent person, and bad consequences could arise from an action that was well-motivated. Instead, he claims, a person has a good will when he "acts out of respect for the moral law." People "act out of respect for the moral law" when they act in some way "because" they have a duty to do so. Thus, the only thing that is truly good in itself is a good will, and a good will is only good when the willer chooses to do something because it is that person's duty, i.e. out of respect for the law. He defines "respect" as "the concept of a worth which thwarts my self-love."


title: Deontology

text: Kant argued that the only absolutely good thing is a good will, and so the single determining factor of whether an action is morally right is the will, or motive of the person doing it. If they are acting on a bad maxim, e.g. 'I will lie', then their action is wrong, even if some good consequences come of it.


title: Deontology

text: In his essay, "On a Supposed Right to Lie Because of Philanthropic Concerns", arguing against the position of Benjamin Constant, "Des réactions politiques", Kant states that:Hence a lie defined merely as an intentionally untruthful declaration to another man does not require the additional condition that it must do harm to another, as jurists require in their definition ("mendacium est falsiloquium in praeiudicium alterius"). For a lie always harms another; if not some human being, then it nevertheless does harm to humanity in general, inasmuch as it vitiates the very source of right [].… All practical principles of right must contain rigorous truth.… This is because such exceptions would destroy the universality on account of which alone they bear the name of principles.


title: Deontology

text: Although not all deontologists are religious, some believe in the "divine command theory", which is actually a cluster of related theories that essentially state that an action is right if God has decreed that it is right. According to English philosopher Ralph Cudworth, William of Ockham, René Descartes, and 18th-century Calvinists all accepted various versions of this moral theory, as they all held that moral obligations arise from God's commands.


title: Deontology

text: The "divine command theory" is a form of deontology because, according to it, the rightness of any action depends upon that action being performed because it is a duty, not because of any good consequences arising from that action. If God commands people not to work on Sabbath, then people act rightly if they do not work on Sabbath "because God has commanded that they do not do so". If they do not work on Sabbath because they are lazy, then their action is not, truly speaking, "right" even though the actual physical action performed is the same. If God commands not to covet a neighbour's goods, this theory holds that it would be immoral to do so, even if coveting provides the beneficial outcome of a drive to succeed or do well.


title: Deontology

text: One thing that clearly distinguishes Kantian deontologism from divine command deontology is that Kantianism maintains that man, as a rational being, makes the moral law universal, whereas divine command maintains that God makes the moral law universal.


title: Deontology

text: W. D. Ross objects to Kant's monistic deontology, which bases ethics in only one foundational principle, the categorical imperative. He contends that there is a plurality of prima facie duties determining what is right. Some duties originate from our own previous actions, like the "duty of fidelity" (to keep promises and to tell the truth), and the "duty of reparation" (to make amends for wrongful acts). The "duty of gratitude" (to return kindnesses received) arises from the actions of others. Other duties include the "duty of non-injury" (not to hurt others), the "duty of beneficence" (to promote the maximum of aggregate good), the "duty of self-improvement" (to improve one's own condition) and the "duty of justice" (to distribute benefits and burdens equably). One problem the deontological pluralist has to face is that cases can arise where the demands of one duty violate another duty, so-called moral dilemmas. For example, there are cases where it is necessary to break a promise in order to relieve someone's distress. Ross makes use of the distinction between "prima facie duties" and "absolute duty" to solve this problem. The duties listed above are "prima facie duties"; they are general principles whose validity is self-evident to morally mature persons. They are factors that do not take all considerations into account. "Absolute duty", on the other hand, is particular to one specific situation, taking everything into account, and has to be judged on a case-by-case basis. It is "absolute duty" that determines which acts are right or wrong.


title: Deontology

text: Contemporary deontologists (i.e., scholars born in the first half of the 20th century) include Józef Maria Bocheński, Thomas Nagel, T. M. Scanlon, and Roger Scruton.


title: Deontology

text: Scruton (2017), in his book "On Human Nature", is critical of consequentialism and similar ethical theories, such as hedonism and utilitarianism, instead proposing a deontological ethical approach. He implies that proportional duty and obligation are essential components of the ways in which we decide to act, and he defends natural law against opposing theories. He also expresses admiration for virtue ethics, and believes that the two ethical theories are not, as is frequently portrayed, mutually exclusive.


title: Deontology

text: Frances Kamm's "Principle of Permissible Harm" (1996) is an effort to derive a deontological constraint that coheres with our considered case judgments while also relying heavily on Kant's categorical imperative. The principle states that one may harm in order to save more if and only if the harm is an effect or an aspect of the greater good itself. This principle is meant to address what Kamm feels are most people's considered case judgments, many of which involve deontological intuitions. For instance, Kamm argues that we believe it would be impermissible to kill one person to harvest his organs in order to save the lives of five others. Yet, we think it is morally permissible to divert a runaway trolley that would otherwise kill five innocent, immobile people, onto a sidetrack where only one innocent and immobile person will be killed. Kamm believes the Principle of Permissible Harm explains the moral difference between these and other cases, and more importantly expresses a constraint telling us exactly when we may not act to bring about good ends—such as in the organ harvesting case.


title: Deontology

text: In 2007, Kamm published "Intricate Ethics", a book that presents a new theory, the "Doctrine of Productive Purity", that incorporates aspects of her "Principle of Permissible Harm". Like the "Principle", the "Doctrine of Productive Purity" is an attempt to provide a deontological prescription for determining the circumstances in which people are permitted to act in a way that harms others.


title: Deontology

text: Various attempts have been made to reconcile deontology with consequentialism. Threshold deontology holds that rules ought to govern up to a point despite adverse consequences; but when the consequences become so dire that they cross a stipulated threshold, consequentialism takes over. Theories put forth by Thomas Nagel and Michael S. Moore attempt to reconcile deontology with consequentialism by assigning each a jurisdiction. Iain King's 2008 book "How to Make Good Decisions and Be Right All the Time" uses quasi-realism and a modified form of utilitarianism to develop deontological principles that are compatible with ethics based on virtues and consequences. King develops a hierarchy of principles to link his meta-ethics, which is more inclined towards consequentialism, with the deontological conclusions he presents in his book.


title: Deontology

text: Intuition-based deontology is a concept within secular ethics. A classical example of literature on secular ethics is the Kural text, authored by the ancient Tamil Indian philosopher Valluvar. It can be argued that some concepts from deontological ethics date back to this text. Concerning ethical intuitionism, 20th century philosopher C.D. Broad coined the term "deontological ethics" to refer to the normative doctrines associated with intuitionism, leaving the phrase "ethical intuitionism" free to refer to the epistemological doctrines.


title: Tacoma, Washington

text: Tacoma ( ) is the county seat of Pierce County, Washington, United States. A port city, it is situated along Washington's Puget Sound, southwest of Seattle, northeast of the state capital, Olympia, and northwest of Mount Rainier National Park. The city's population was 219,346 at the time of the 2020 census. Tacoma is the second-largest city in the Puget Sound area and the third-largest in the state. Tacoma also serves as the center of business activity for the South Sound region, which has a population of about 1 million.