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11,600 | In March 1904, the Wright Brothers applied for French and German patents. The French patent was granted on July 1, 1904. According to Combs, regarding the U.S. patent, "... by 1906 the drawings in the Wright patents were available to anyone who wanted badly enough to get them. And they gave proof – in vivid, technical detail – of how to get into the air." | https://en.wikipedia.org/wiki?curid=58410 |
11,601 | Attempting to circumvent the patent, Glenn Curtiss and other early aviators devised ailerons to emulate lateral control described in the patent and demonstrated by the Wrights in their public flights. | https://en.wikipedia.org/wiki?curid=58410 |
11,602 | Soon after the historic July 4, 1908, one-kilometer flight by Curtiss in the AEA June Bug, the Wrights warned him not to infringe their patent by profiting from flying or selling aircraft that used ailerons. | https://en.wikipedia.org/wiki?curid=58410 |
11,603 | Orville wrote Curtiss, "Claim 14 of our patent no. 821,393, specifically covers the combination which we are informed you are using. If it is your desire to enter the exhibition business, we would be glad to take up the matter of a license to operate under our patent for that purpose." | https://en.wikipedia.org/wiki?curid=58410 |
11,604 | Curtiss was at the time a member of the Aerial Experiment Association (AEA), headed by Alexander Graham Bell, where in 1908 he had helped reinvent wingtip ailerons for their Aerodrome No. 2, known as the AEA White Wing | https://en.wikipedia.org/wiki?curid=58410 |
11,605 | Curtiss refused to pay license fees to the Wrights and sold an airplane equipped with ailerons to the Aeronautic Society of New York in 1909. The Wrights filed a lawsuit, beginning a years-long legal conflict. They also sued foreign aviators who flew at U.S. exhibitions, including the leading French aviator Louis Paulhan. The Curtiss people derisively suggested that if someone jumped in the air and waved his arms, the Wrights would sue. | https://en.wikipedia.org/wiki?curid=58410 |
11,606 | European companies which bought foreign patents the Wrights had received sued other manufacturers in their countries. Those lawsuits were only partly successful. Despite a pro-Wright ruling in France, legal maneuvering dragged on until the patent expired in 1917. A German court ruled the patent invalid because of prior disclosure in speeches by Wilbur Wright in 1901, and Chanute in 1903. In the U.S. the Wrights made an agreement with the Aero Club of America to license airshows which the Club approved, freeing participating pilots from a legal threat. Promoters of approved shows paid fees to the Wrights. | https://en.wikipedia.org/wiki?curid=58410 |
11,607 | The Wright brothers won their initial case against Curtiss in February 1913 when a judge ruled that ailerons were covered under the patent. The Curtiss company appealed the decision. | https://en.wikipedia.org/wiki?curid=58410 |
11,608 | From 1910 until his death from typhoid fever in 1912, Wilbur took the leading role in the patent struggle, travelling incessantly to consult with lawyers and testify in what he felt was a moral cause, particularly against Curtiss, who was creating a large company to manufacture aircraft. The Wrights' preoccupation with the legal issue stifled their work on new designs, and by 1911 Wright airplanes were considered inferior to those of European makers. Indeed, aviation development in the U.S. was suppressed to such an extent that, when the U.S. entered World War I, no acceptable American-designed airplanes were available, and U.S. forces were compelled to use French machines. Orville and Katharine Wright believed Curtiss was partly responsible for Wilbur's premature death, which occurred in the wake of his exhausting travels and the stress of the legal battle. | https://en.wikipedia.org/wiki?curid=58410 |
11,609 | In January 1914, a U.S. Circuit Court of Appeals upheld the verdict against the Curtiss company, which continued to avoid penalties through legal tactics. Orville apparently felt vindicated by the decision, and much to the frustration of company executives, he did not push vigorously for further legal action to ensure a manufacturing monopoly. In fact, he was planning to sell the company and departed in 1915. In 1917, with World War I underway, the U.S. government pressured the industry to form a cross-licensing organization, the Manufacturers Aircraft Association, to which member companies paid a blanket fee for the use of aviation patents, including the original and subsequent Wright patents. The "patent war" ended, although side issues lingered in the courts until the 1920s. In a twist of irony, the Wright Aeronautical Corporation (successor to the Wright-Martin Company), and the Curtiss Aeroplane company, merged in 1929 to form the Curtiss-Wright Corporation, which remains in business today producing high-tech components for the aerospace industry. | https://en.wikipedia.org/wiki?curid=58410 |
11,610 | Aviation historian C.H. Gibbs-Smith stated a number of times that the Wrights' legal victory would have been "doubtful" if an 1868 patent of "a prior but lost invention" by M.P.W. Boulton of the U.K. had been known in the period 1903–1906. The patent, titled "Aërial Locomotion &c," described several engine improvements and conceptual designs and included a technical description and drawings of an aileron control system and an optional feature intended to function as an autopilot. In fact, this patent was well known to participants in the Wright-Curtiss lawsuit. A U.S. federal judge who reviewed previous inventions and patents and upheld the Wright patent against the Curtiss company reached the opposite conclusion of Gibbs-Smith, saying the Boulton patent "is not anticipatory". | https://en.wikipedia.org/wiki?curid=58410 |
11,611 | The lawsuits damaged the public image of the Wright brothers, who were generally regarded before this as heroes. Critics said the brothers were greedy and unfair, and compared their actions unfavorably to European inventors, who worked more openly. Supporters said the brothers were protecting their interests and were justified in expecting fair compensation for the years of work leading to their successful invention. Their 10-year friendship with Octave Chanute, already strained by tension over how much credit, if any, he might deserve for their success, collapsed after he publicly criticized their actions. | https://en.wikipedia.org/wiki?curid=58410 |
11,612 | The Wright Company was incorporated on November 22, 1909. The brothers sold their patents to the company for $100,000 and also received one-third of the shares in a million dollar stock issue and a 10 percent royalty on every airplane sold. With Wilbur as president and Orville as vice president, the company set up a factory in Dayton and a flying school / test flight field at Huffman Prairie; the headquarters office was in New York City. | https://en.wikipedia.org/wiki?curid=58410 |
11,613 | In mid-1910, the Wrights changed the design of the "Wright Flyer", moving the horizontal elevator from the front to the back and adding wheels although keeping the skids as part of the undercarriage unit. It had become apparent by then that a rear elevator would make an airplane easier to control, especially as higher speeds grew more common. The new version was designated the "Model B", although the original canard design was never referred to as the "Model A" by the Wrights. However, the U.S. Army Signal Corps which bought the airplane did call it "Wright type A". | https://en.wikipedia.org/wiki?curid=58410 |
11,614 | There were not many customers for airplanes, so in the spring of 1910 the Wrights hired and trained a team of salaried exhibition pilots to show off their machines and win prize money for the company – despite Wilbur's disdain for what he called "the mountebank business". The team debuted at the Indianapolis Speedway on June 13. Before the year was over, pilots Ralph Johnstone and Arch Hoxsey died in air show crashes, and in November 1911 the brothers disbanded the team on which nine men had served (four other former team members died in crashes afterward). | https://en.wikipedia.org/wiki?curid=58410 |
11,615 | The Wright Company transported the first known commercial air cargo on November 7, 1910, by flying two bolts of dress silk from Dayton to Columbus, Ohio, for the Morehouse-Martens Department Store, which paid a $5,000 fee. Company pilot Phil Parmelee made the flight – which was more an exercise in advertising than a simple delivery – in an hour and six minutes with the cargo strapped in the passenger's seat. The silk was cut into small pieces and sold as souvenirs. | https://en.wikipedia.org/wiki?curid=58410 |
11,616 | Between 1910 and 1916 the Wright Brothers Flying School at Huffman Prairie trained 115 pilots who were instructed by Orville and his assistants. Several trainees became famous, including Henry "Hap" Arnold, who rose to Five-Star General, commanded U.S. Army Air Forces in World War II, and became the first head of the U.S. Air Force; Calbraith Perry Rodgers, who made the first coast-to-coast flight in 1911 (with many stops and crashes) in a Wright Model EX named the "Vin Fiz" (after the sponsor's grape soft drink); and Eddie Stinson, founder of the Stinson Aircraft Company. | https://en.wikipedia.org/wiki?curid=58410 |
11,617 | In 1912–1913 a series of fatal crashes of Wright airplanes bought by the U.S. Army called into question their safety and design. The death toll reached 11 by 1913, half of them in the Wright model C. All six model C Army airplanes crashed. They had a tendency to nose dive, but Orville insisted that stalls were caused by pilot error. He cooperated with the Army to equip the airplanes with a rudimentary flight indicator to help the pilot avoid climbing too steeply. A government investigation said the Wright model C was "dynamically unsuited for flying", and the American military ended its use of airplanes with "pusher" type propellers, including models made by both the Wright and Curtiss companies, in which the engine was located behind the pilot and likely to crush him in a crash. Orville resisted the switch to manufacturing "tractor-type" propeller aircraft, worried that a design change could threaten the Wright patent infringement case against Curtiss. | https://en.wikipedia.org/wiki?curid=58410 |
11,618 | S.P. Langley, secretary of the Smithsonian Institution from 1887 until his death in 1906, experimented for years with model flying machines and successfully flew unmanned powered fixed-wing model aircraft in 1896 and 1903. Two tests of his manned full-size motor-driven Aerodrome in October and December 1903, however, were complete failures. Nevertheless, the Smithsonian later proudly displayed the Aerodrome in its museum as the first heavier-than-air craft "capable" of manned powered flight, relegating the Wright brothers' invention to secondary status and triggering a decades-long feud with Orville Wright, whose brother had received help from the Smithsonian when beginning his own quest for flight. | https://en.wikipedia.org/wiki?curid=58410 |
11,619 | The Smithsonian based its claim for the Aerodrome on short test flights Glenn Curtiss and his team made with it in 1914. The Smithsonian had allowed Curtiss to make major modifications to the craft before attempting to fly it. | https://en.wikipedia.org/wiki?curid=58410 |
11,620 | The Smithsonian hoped to salvage Langley's aeronautical reputation by proving the Aerodrome could fly; Curtiss wanted to prove the same thing to defeat the Wrights' patent lawsuits against him. The tests had no effect on the patent battle, but the Smithsonian made the most of them, honoring the Aerodrome in its museum and publications. The Institution did not reveal the extensive Curtiss modifications, but Orville Wright learned of them from his brother Lorin and a close friend of his and Wilbur's, Griffith Brewer, who both witnessed and photographed some of the tests. | https://en.wikipedia.org/wiki?curid=58410 |
11,621 | Orville repeatedly objected to misrepresentation of the Aerodrome, but the Smithsonian was unyielding. Orville responded by lending the restored 1903 Kitty Hawk Flyer to the London Science Museum in 1928, refusing to donate it to the Smithsonian while the Institution "perverted" the history of the flying machine. Orville would never see his invention again, as he died before its return to the United States. | https://en.wikipedia.org/wiki?curid=58410 |
11,622 | Charles Lindbergh attempted to mediate the dispute, to no avail. In 1942, after years of bad publicity, and encouraged by Wright biographer F.C. Kelly, the Smithsonian finally relented by publishing, for the first time, a list of the Aerodrome modifications and recanting the misleading statements it had published about the 1914 tests. Orville then privately requested the British museum to return the "Flyer", but the airplane remained in protective storage for the duration of World War II; it finally came home after Orville's death. | https://en.wikipedia.org/wiki?curid=58410 |
11,623 | On November 23, 1948, the executors of Orville's estate signed an agreement for the Smithsonian to purchase the Flyer for one dollar. At the insistence of the executors, the agreement also included strict conditions for display of the airplane. | https://en.wikipedia.org/wiki?curid=58410 |
11,624 | If this agreement is not fulfilled, the "Flyer" can be reclaimed by the heir of the Wright brothers. Some aviation enthusiasts, particularly those who promote the legacy of Gustave Whitehead, have accused the Smithsonian of refusing to investigate claims of earlier flights. After a ceremony in the Smithsonian museum, the "Flyer" went on public display on December 17, 1948, the 45th anniversary of the only day it was flown successfully. The Wright brothers' nephew Milton (Lorin's son), who had seen gliders and the Flyer under construction in the bicycle shop when he was a boy, gave a brief speech and formally transferred the airplane to the Smithsonian, which displayed it with the accompanying label: | https://en.wikipedia.org/wiki?curid=58410 |
11,625 | Both Wilbur and Orville were life-long bachelors. Wilbur once quipped that he 'did not have time for both a wife and an airplane'. The 1909 short silent film "Wilbur Wright und seine Flugmaschine" (which translates to "Wilbur Wright and his Flying Machine") is considered to be the first use of motion picture aerial photography as filmed from a heavier-than-air aircraft. Following a brief training flight he gave to a German pilot in Berlin in June 1911, Wilbur never flew again. He gradually became occupied with business matters for the Wright Company and dealing with different lawsuits. Upon dealing with the patent lawsuits, which had put great strain on both brothers, Wilbur had written in a letter to a French friend: | https://en.wikipedia.org/wiki?curid=58410 |
11,626 | Wilbur spent the next year before his death traveling, where he spent a full six months in Europe attending to various business and legal matters. Wilbur urged American cities to emulate the European – particularly Parisian – philosophy of apportioning generous public space near every important public building. He was also constantly back and forth between New York, Washington, and Dayton. All of the stresses were taking a toll on Wilbur physically. Orville would remark that he would "come home white". | https://en.wikipedia.org/wiki?curid=58410 |
11,627 | It was decided by the family that a new and far grander house would be built, using the money that the Wrights had earned through their inventions and business. Called affectionately Hawthorn Hill, building had begun in the Dayton suburb of Oakwood, Ohio, while Wilbur was in Europe. Katharine and Orville oversaw the project in his absence. Wilbur's one known expression upon the design of the house was that he have a room and bathroom of his own. The brothers hired Schenck and Williams, an architectural firm, to design the house, along with input from both Wilbur and Orville. Wilbur did not live to see its completion in 1914. | https://en.wikipedia.org/wiki?curid=58410 |
11,628 | He became ill on a business trip to Boston in April 1912. The illness is sometimes attributed to eating bad shellfish at a banquet. After returning to Dayton in early May 1912, worn down in mind and body, he fell ill again and was diagnosed with typhoid fever. He lingered on, his symptoms relapsing and remitting for many days. Wilbur died, at age 45, at the Wright family home on May 30. His father wrote about Wilbur in his diary: "A short life, full of consequences. An unfailing intellect, imperturbable temper, great self-reliance and as great modesty, seeing the right clearly, pursuing it steadfastly, he lived and died." | https://en.wikipedia.org/wiki?curid=58410 |
11,629 | Orville succeeded to the presidency of the Wright Company upon Wilbur's death. He won the prestigious Collier Trophy in 1914 for development of his automatic stabilizer on the brothers' Wright Model E. Sharing Wilbur's distaste for business but not his brother's executive skills, Orville sold the company in 1915. The Wright Company then became part of Wright-Martin in 1916. | https://en.wikipedia.org/wiki?curid=58410 |
11,630 | After 42 years living at their residence on 7 Hawthorn Street, Orville, Katharine, and their father, Milton, moved to Hawthorn Hill in spring 1914. Milton died in his sleep on April 3, 1917, at age 88. Up until his death, Milton had been very active, preoccupied with reading, writing articles for religious publications and enjoying his morning walks. He had also marched in a Dayton Woman's Suffrage Parade, along with Orville and Katharine. | https://en.wikipedia.org/wiki?curid=58410 |
11,631 | Orville made his last flight as a pilot in 1918 in a 1911 Model B. He retired from business and became an elder statesman of aviation, serving on various official boards and committees, including the National Advisory Committee for Aeronautics (NACA), and Aeronautical Chamber of Commerce (ACCA). | https://en.wikipedia.org/wiki?curid=58410 |
11,632 | Katharine married Henry Haskell of Kansas City, a former Oberlin classmate, in 1926. Orville was furious and inconsolable, feeling he had been betrayed by his sister Katharine. He refused to attend the wedding or even communicate with her. He finally agreed to see her, apparently at Lorin's insistence, just before she died of pneumonia on March 3, 1929. | https://en.wikipedia.org/wiki?curid=58410 |
11,633 | Orville Wright served in the NACA for 28 years. In 1930, he received the first Daniel Guggenheim Medal established in 1928 by the Daniel Guggenheim Fund for the Promotion of Aeronautics. In 1936, he was elected a member of the National Academy of Sciences. In 1939, President Franklin Delano Roosevelt issued a presidential proclamation which designated the anniversary of Orville's birthday as National Aviation Day, a national observation that celebrates the development of aviation. | https://en.wikipedia.org/wiki?curid=58410 |
11,634 | On April 19, 1944, the second production Lockheed Constellation, piloted by Howard Hughes and TWA president Jack Frye, flew from Burbank, California, to Washington, DC, in 6 hours and 57 minutes (2300 mi, 330.9 mph). On the return trip, the airliner stopped at Wright Field to give Orville Wright his last airplane flight, more than 40 years after his historic first flight. He may even have briefly handled the controls. He commented that the wingspan of the Constellation was longer than the distance of his first flight. | https://en.wikipedia.org/wiki?curid=58410 |
11,635 | Orville's last major project was supervising the reclamation and preservation of the 1905 "Wright Flyer III", which historians describe as the first practical airplane. | https://en.wikipedia.org/wiki?curid=58410 |
11,636 | Orville expressed sadness in an interview years later about the death and destruction brought about by the bombers of World War II: | https://en.wikipedia.org/wiki?curid=58410 |
11,637 | Orville died at age 76 on January 30, 1948, over 35 years after his brother, following his second heart attack, having lived from the horse-and-buggy age to the dawn of supersonic flight. Both brothers are buried in the family plot at Woodland Cemetery, Dayton, Ohio. John T. Daniels, the Coast Guardsman who took their famous first flight photo, died the day after Orville. | https://en.wikipedia.org/wiki?curid=58410 |
11,638 | First powered flight claims are made for Clément Ader, Gustave Whitehead, Richard Pearse, and Karl Jatho for their variously documented tests in years prior to and including 1903. Claims that the first true flight occurred after 1903 are made for Traian Vuia and Alberto Santos-Dumont. Supporters of the post-Wright pioneers argue that techniques used by the Wright brothers disqualify them as first to make successful airplane flights. Those techniques were: A launch rail; skids instead of wheels; a headwind at takeoff; and a catapult after 1903. Supporters of the Wright brothers argue that proven, repeated, controlled, and sustained flights by the brothers entitle them to credit as inventors of the airplane, regardless of those techniques. | https://en.wikipedia.org/wiki?curid=58410 |
11,639 | The aviation historian C.H. Gibbs-Smith was a supporter of the Wrights' claim to primacy in flight. He wrote that a barn door can be made to "fly" for a short distance if enough energy is applied to it; he determined that the very limited flight experiments of Ader, Vuia, and others were "powered hops" instead of fully controlled flights. | https://en.wikipedia.org/wiki?curid=58410 |
11,640 | The U.S. states of Ohio and North Carolina both take credit for the Wright brothers and their world-changing inventions—Ohio because the brothers developed and built their designs in Dayton, and North Carolina because Kitty Hawk was the site of the Wrights' first powered flight. With a spirit of friendly rivalry, Ohio adopted the slogan "Birthplace of Aviation" (later "Birthplace of Aviation Pioneers", recognizing not only the Wrights, but also astronauts John Glenn and Neil Armstrong, both Ohio natives). The slogan appears on Ohio license plates. North Carolina uses the slogan "First in Flight" on its license plates. | https://en.wikipedia.org/wiki?curid=58410 |
11,641 | The site of the first flights in North Carolina is preserved as Wright Brothers National Memorial, while their Ohio facilities are part of Dayton Aviation Heritage National Historical Park. As the positions of both states can be factually defended, and each played a significant role in the history of flight, neither state has an exclusive claim to the Wrights' accomplishment. | https://en.wikipedia.org/wiki?curid=58410 |
11,642 | Notwithstanding the competition between those two states, in 1937 the Wrights' last bicycle shop and home were moved from Dayton, Ohio to Greenfield Village in Dearborn, Michigan, where they remain. | https://en.wikipedia.org/wiki?curid=58410 |
11,643 | NASA named the first Martian take-off and landing area for the 2021 "Ingenuity" helicopter "Wright Brothers Field". "Ingenuity" arrived on Mars stored under the "Perseverance" rover as part of the Mars 2020 mission, was flown five times from Wright Brothers Field between April 19 and May 7, 2021, and was flown away from the field on its fifth flight on May 7. | https://en.wikipedia.org/wiki?curid=58410 |
11,644 | The helicopter carries a small piece of wing fabric from the 1903 "Wright Flyer" attached to a cable underneath its solar panel. In 1969, Neil Armstrong carried a similar "Wright Flyer" artifact to the Moon in the Lunar Module "Eagle" during Apollo 11. | https://en.wikipedia.org/wiki?curid=58410 |
11,645 | Coordinated Universal Time or UTC is the primary time standard by which the world regulates clocks and time. It is within about one second of mean solar time (such as UT1) at 0° longitude (at the IERS Reference Meridian as the currently used prime meridian) and is not adjusted for daylight saving time. It is effectively a successor to Greenwich Mean Time (GMT). | https://en.wikipedia.org/wiki?curid=25453500 |
11,646 | The coordination of time and frequency transmissions around the world began on 1 January 1960. UTC was first officially adopted as CCIR Recommendation 374, "Standard-Frequency and Time-Signal Emissions", in 1963, but the official abbreviation of UTC and the official English name of Coordinated Universal Time (along with the French equivalent) were not adopted until 1967. | https://en.wikipedia.org/wiki?curid=25453500 |
11,647 | The system has been adjusted several times, including a brief period during which the time-coordination radio signals broadcast both UTC and "Stepped Atomic Time (SAT)" before a new UTC was adopted in 1970 and implemented in 1972. This change also adopted leap seconds to simplify future adjustments. This CCIR Recommendation 460 "stated that (a) carrier frequencies and time intervals should be maintained constant and should correspond to the definition of the SI second; (b) step adjustments, when necessary, should be exactly 1 s to maintain approximate agreement with Universal Time (UT); and (c) standard signals should contain information on the difference between UTC and UT." | https://en.wikipedia.org/wiki?curid=25453500 |
11,648 | The General Conference on Weights and Measures adopted a resolution to alter UTC with a new system that would eliminate leap seconds by 2035. | https://en.wikipedia.org/wiki?curid=25453500 |
11,649 | The current version of UTC is defined by International Telecommunication Union Recommendation (ITU-R TF.460-6), "Standard-frequency and time-signal emissions", and is based on International Atomic Time (TAI) with leap seconds added at irregular intervals to compensate for the accumulated difference between TAI and time measured by Earth's rotation. Leap seconds are inserted as necessary to keep UTC within 0.9 seconds of the UT1 variant of universal time. See the "Current number of leap seconds" section for the number of leap seconds inserted to date. | https://en.wikipedia.org/wiki?curid=25453500 |
11,650 | The official abbreviation for Coordinated Universal Time is "UTC". This abbreviation comes as a result of the International Telecommunication Union and the International Astronomical Union wanting to use the same abbreviation in all languages. English speakers originally proposed "CUT" (for "coordinated universal time"), while French speakers proposed "TUC" (for ""). The compromise that emerged was "UTC", which conforms to the pattern for the abbreviations of the variants of Universal Time (UT0, UT1, UT2, UT1R, etc.). | https://en.wikipedia.org/wiki?curid=25453500 |
11,651 | Time zones around the world are expressed using positive or negative offsets from UTC, as in the list of time zones by UTC offset. | https://en.wikipedia.org/wiki?curid=25453500 |
11,652 | The westernmost time zone uses , being twelve hours behind UTC; the easternmost time zone uses , being fourteen hours ahead of UTC. In 1995, the island nation of Kiribati moved those of its atolls in the Line Islands from UTC−10 to so that Kiribati would all be on the same day. | https://en.wikipedia.org/wiki?curid=25453500 |
11,653 | UTC is used in many Internet and World Wide Web standards. The Network Time Protocol (NTP), designed to synchronise the clocks of computers over the Internet, transmits time information from the UTC system. If only milliseconds precision is needed, clients can obtain the current UTC from a number of official internet UTC servers. For sub-microsecond precision, clients can obtain the time from satellite signals. | https://en.wikipedia.org/wiki?curid=25453500 |
11,654 | UTC is also the time standard used in aviation, e.g. for flight plans and air traffic control. Weather forecasts and maps all use UTC to avoid confusion about time zones and daylight saving time. The International Space Station also uses UTC as a time standard. | https://en.wikipedia.org/wiki?curid=25453500 |
11,655 | Amateur radio operators often schedule their radio contacts in UTC, because transmissions on some frequencies can be picked up in many time zones. | https://en.wikipedia.org/wiki?curid=25453500 |
11,656 | UTC divides time into days, hours, minutes and seconds. Days are conventionally identified using the Gregorian calendar, but Julian day numbers can also be used. Each day contains 24 hours and each hour contains 60 minutes. The number of seconds in a minute is usually 60, but with an occasional leap second, it may be 61 or 59 instead. Thus, in the UTC time scale, the second and all smaller time units (millisecond, microsecond, etc.) are of constant duration, but the minute and all larger time units (hour, day, week, etc.) are of variable duration. Decisions to introduce a leap second are announced at least six months in advance in "Bulletin C" produced by the International Earth Rotation and Reference Systems Service. The leap seconds cannot be predicted far in advance due to the unpredictable rate of the rotation of Earth. | https://en.wikipedia.org/wiki?curid=25453500 |
11,657 | Nearly all UTC days contain exactly 86,400 SI seconds with exactly 60 seconds in each minute. UTC is within about one second of mean solar time at 0° longitude, so that, because the mean solar day is slightly longer than 86,400 SI seconds, occasionally the last minute of a UTC day is adjusted to have 61 seconds. The extra second is called a leap second. It accounts for the grand total of the extra length (about 2 milliseconds each) of all the mean solar days since the previous leap second. The last minute of a UTC day is permitted to contain 59 seconds to cover the remote possibility of the Earth rotating faster, but that has not yet been necessary. The irregular day lengths mean that fractional Julian days do not work properly with UTC. | https://en.wikipedia.org/wiki?curid=25453500 |
11,658 | Since 1972, UTC is calculated by subtracting the accumulated leap seconds from International Atomic Time (TAI), which is a coordinate time scale tracking notional proper time on the rotating surface of the Earth (the geoid). In order to maintain a close approximation to UT1, UTC occasionally has discontinuities where it changes from one linear function of TAI to another. These discontinuities take the form of leap seconds implemented by a UTC day of irregular length. Discontinuities in UTC have occurred only at the end of June or December, although there is provision for them to happen at the end of March and September as well as a second preference. The International Earth Rotation and Reference Systems Service (IERS) tracks and publishes the difference between UTC and Universal Time, DUT1 = UT1 − UTC, and introduces discontinuities into UTC to keep DUT1 in the interval (−0.9 s, +0.9 s). | https://en.wikipedia.org/wiki?curid=25453500 |
11,659 | As with TAI, UTC is only known with the highest precision in retrospect. Users who require an approximation in real time must obtain it from a time laboratory, which disseminates an approximation using techniques such as GPS or radio time signals. Such approximations are designated UTC("k"), where "k" is an abbreviation for the time laboratory. The time of events may be provisionally recorded against one of these approximations; later corrections may be applied using the International Bureau of Weights and Measures (BIPM) monthly publication of tables of differences between canonical TAI/UTC and TAI("k")/UTC("k") as estimated in real time by participating laboratories. (See the article on International Atomic Time for details.) | https://en.wikipedia.org/wiki?curid=25453500 |
11,660 | Because of time dilation, a standard clock not on the geoid, or in rapid motion, will not maintain synchronicity with UTC. Therefore, telemetry from clocks with a known relation to the geoid is used to provide UTC when required, on locations such as those of spacecraft. | https://en.wikipedia.org/wiki?curid=25453500 |
11,661 | It is not possible to compute the exact time interval elapsed between two UTC timestamps without consulting a table that shows how many leap seconds occurred during that interval. By extension, it is not possible to compute the precise duration of a time interval that ends in the future and may encompass an unknown number of leap seconds (for example, the number of TAI seconds between "now" and 2099-12-31 23:59:59). Therefore, many scientific applications that require precise measurement of long (multi-year) intervals use TAI instead. TAI is also commonly used by systems that cannot handle leap seconds. GPS time always remains exactly 19 seconds behind TAI (neither system is affected by the leap seconds introduced in UTC). | https://en.wikipedia.org/wiki?curid=25453500 |
11,662 | Time zones are usually defined as differing from UTC by an integer number of hours, although the laws of each jurisdiction would have to be consulted if sub-second accuracy was required. Several jurisdictions have established time zones that differ by an odd integer number of half-hours or quarter-hours from UT1 or UTC. | https://en.wikipedia.org/wiki?curid=25453500 |
11,663 | Current civil time in a particular time zone can be determined by adding or subtracting the number of hours and minutes specified by the UTC offset, which ranges from in the west to in the east (see List of UTC time offsets). | https://en.wikipedia.org/wiki?curid=25453500 |
11,664 | The time zone using UTC is sometimes denoted or by the letter "Z"—a reference to the equivalent nautical time zone (GMT), which has been denoted by a "Z" since about 1950. Time zones were identified by successive letters of the alphabet and the Greenwich time zone was marked by a "Z" as it was the point of origin. The letter also refers to the "zone description" of zero hours, which has been used since 1920 (see time zone history). Since the NATO phonetic alphabet word for "Z" is "Zulu", UTC is sometimes known as "Zulu time". This is especially true in aviation, where "Zulu" is the universal standard. This ensures that all pilots, regardless of location, are using the same 24-hour clock, thus avoiding confusion when flying between time zones. See the list of military time zones for letters used in addition to "Z" in qualifying time zones other than Greenwich. | https://en.wikipedia.org/wiki?curid=25453500 |
11,665 | On electronic devices which only allow the time zone to be configured using maps or city names, UTC can be selected indirectly by selecting cities such as Accra in Ghana or Reykjavík in Iceland as they are always on UTC and do not currently use Daylight Saving Time (which Greenwich and London do, and so could be a source of error). | https://en.wikipedia.org/wiki?curid=25453500 |
11,666 | UTC does not change with a change of seasons, but local time or civil time may change if a time zone jurisdiction observes daylight saving time (summer time). For example, local time on the east coast of the United States is five hours behind UTC during winter, but four hours behind while daylight saving is observed there. | https://en.wikipedia.org/wiki?curid=25453500 |
11,667 | In 1928, the term Universal Time (UT) was introduced by the International Astronomical Union to refer to GMT, with the day starting at midnight. Until the 1950s, broadcast time signals were based on UT, and hence on the rotation of the Earth. | https://en.wikipedia.org/wiki?curid=25453500 |
11,668 | In 1955, the caesium atomic clock was invented. This provided a form of timekeeping that was both more stable and more convenient than astronomical observations. In 1956, the U.S. National Bureau of Standards and U.S. Naval Observatory started to develop atomic frequency time scales; by 1959, these time scales were used in generating the WWV time signals, named for the shortwave radio station that broadcasts them. In 1960, the U.S. Naval Observatory, the Royal Greenwich Observatory, and the UK National Physical Laboratory coordinated their radio broadcasts so that time steps and frequency changes were coordinated, and the resulting time scale was informally referred to as "Coordinated Universal Time". | https://en.wikipedia.org/wiki?curid=25453500 |
11,669 | In a controversial decision, the frequency of the signals was initially set to match the rate of UT, but then kept at the same frequency by the use of atomic clocks and deliberately allowed to drift away from UT. When the divergence grew significantly, the signal was phase shifted (stepped) by 20 ms to bring it back into agreement with UT. Twenty-nine such steps were used before 1960. | https://en.wikipedia.org/wiki?curid=25453500 |
11,670 | In 1958, data was published linking the frequency for the caesium transition, newly established, with the ephemeris second. The ephemeris second is a unit in the system of time that, when used as the independent variable in the laws of motion that govern the movement of the planets and moons in the solar system, enables the laws of motion to accurately predict the observed positions of solar system bodies. Within the limits of observable accuracy, ephemeris seconds are of constant length, as are atomic seconds. This publication allowed a value to be chosen for the length of the atomic second that would accord with the celestial laws of motion. | https://en.wikipedia.org/wiki?curid=25453500 |
11,671 | In 1961, the Bureau International de l'Heure began coordinating the UTC process internationally (but the name Coordinated Universal Time was not formally adopted by the International Astronomical Union until 1967). From then on, there were time steps every few months, and frequency changes at the end of each year. The jumps increased in size to 0.1 seconds. This UTC was intended to permit a very close approximation to UT2. | https://en.wikipedia.org/wiki?curid=25453500 |
11,672 | In 1967, the SI second was redefined in terms of the frequency supplied by a caesium atomic clock. The length of second so defined was practically equal to the second of ephemeris time. This was the frequency that had been provisionally used in TAI since 1958. It was soon decided that having two types of second with different lengths, namely the UTC second and the SI second used in TAI, was a bad idea. It was thought better for time signals to maintain a consistent frequency, and that this frequency should match the SI second. Thus it would be necessary to rely on time steps alone to maintain the approximation of UT. This was tried experimentally in a service known as "Stepped Atomic Time" (SAT), which ticked at the same rate as TAI and used jumps of 0.2 seconds to stay synchronised with UT2. | https://en.wikipedia.org/wiki?curid=25453500 |
11,673 | There was also dissatisfaction with the frequent jumps in UTC (and SAT). In 1968, Louis Essen, the inventor of the caesium atomic clock, and G. M. R. Winkler both independently proposed that steps should be of 1 second only. This system was eventually approved, along with the idea of maintaining the UTC second equal to the TAI second. At the end of 1971, there was a final irregular jump of exactly 0.107758 TAI seconds, making the total of all the small time steps and frequency shifts in UTC or TAI during 1958–1971 exactly ten seconds, so that was exactly, and a whole number of seconds thereafter. At the same time, the tick rate of UTC was changed to exactly match TAI. UTC also started to track UT1 rather than UT2. Some time signals started to broadcast the DUT1 correction (UT1 − UTC) for applications requiring a closer approximation of UT1 than UTC now provided. | https://en.wikipedia.org/wiki?curid=25453500 |
11,674 | The first leap second occurred on 30 June 1972. Since then, leap seconds have occurred on average about once every 19 months, always on 30 June or 31 December. , there have been 27 leap seconds in total, all positive, putting UTC 37 seconds behind TAI. | https://en.wikipedia.org/wiki?curid=25453500 |
11,675 | Earth's rotational speed is very slowly decreasing because of tidal deceleration; this increases the length of the mean solar day. The length of the SI second was calibrated on the basis of the second of ephemeris time and can now be seen to have a relationship with the mean solar day observed between 1750 and 1892, analysed by Simon Newcomb. As a result, the SI second is close to of a mean solar day in the mid‑19th century. In earlier centuries, the mean solar day was shorter than 86,400 SI seconds, and in more recent centuries it is longer than 86,400 seconds. Near the end of the 20th century, the length of the mean solar day (also known simply as "length of day" or "LOD") was approximately 86,400.0013 s. For this reason, UT is now "slower" than TAI by the difference (or "excess" LOD) of 1.3 ms/day. | https://en.wikipedia.org/wiki?curid=25453500 |
11,676 | The excess of the LOD over the nominal 86,400 s accumulates over time, causing the UTC day, initially synchronised with the mean sun, to become desynchronised and run ahead of it. Near the end of the 20th century, with the LOD at 1.3 ms above the nominal value, UTC ran faster than UT by 1.3 ms per day, getting a second ahead roughly every 800 days. Thus, leap seconds were inserted at approximately this interval, retarding UTC to keep it synchronised in the long term. The actual rotational period varies on unpredictable factors such as tectonic motion and has to be observed, rather than computed. | https://en.wikipedia.org/wiki?curid=25453500 |
11,677 | Just as adding a leap day every four years does not mean the year is getting longer by one day every four years, the insertion of a leap second every 800 days does not indicate that the mean solar day is getting longer by a second every 800 days. It will take about 50,000 years for a mean solar day to lengthen by one second (at a rate of 2 ms per century). This rate fluctuates within the range of 1.7–2.3 ms/cy. While the rate due to tidal friction alone is about 2.3 ms/cy, the uplift of Canada and Scandinavia by several metres since the last ice age has temporarily reduced this to 1.7 ms/cy over the last 2,700 years. The correct reason for leap seconds, then, is not the current difference between actual and nominal LOD, but rather the "accumulation" of this difference over a period of time: Near the end of the 20th century, this difference was about of a second per day; therefore, after about 800 days, it accumulated to 1 second (and a leap second was then added). | https://en.wikipedia.org/wiki?curid=25453500 |
11,678 | In the graph of DUT1 above, the excess of LOD above the nominal 86,400 s corresponds to the downward slope of the graph between vertical segments. (The slope became shallower in the 1980s, 2000s and late 2010s to 2020s because of slight accelerations of Earth's rotation temporarily shortening the day.) Vertical position on the graph corresponds to the accumulation of this difference over time, and the vertical segments correspond to leap seconds introduced to match this accumulated difference. Leap seconds are timed to keep DUT1 within the vertical range depicted by the adjacent graph. The frequency of leap seconds therefore corresponds to the slope of the diagonal graph segments, and thus to the excess LOD. Time periods when the slope reverses direction (slopes upwards, not the vertical segments) are times when the excess LOD is negative, that is, when the LOD is below 86,400 s. | https://en.wikipedia.org/wiki?curid=25453500 |
11,679 | As the Earth's rotation continues to slow, positive leap seconds will be required more frequently. The long-term rate of change of LOD is approximately +1.7 ms per century. At the end of the 21st century, LOD will be roughly 86,400.004 s, requiring leap seconds every 250 days. Over several centuries, the frequency of leap seconds will become problematic. A change in the trend of the UT1 – UTC values was seen beginning around June 2019 in which instead of slowing down (with leap seconds to keep the difference between UT1 and UTC less than 0.9 seconds) the earth's rotation has sped up, causing this difference to increase. If the trend continues, a negative leap second may be required, which has not been used before. This may not be needed until 2025. | https://en.wikipedia.org/wiki?curid=25453500 |
11,680 | Some time in the 22nd century, two leap seconds will be required every year. The current practice of only allowing leap seconds in June and December will be insufficient to maintain a difference of less than 1 second, and it might be decided to introduce leap seconds in March and September. In the 25th century, four leap seconds are projected to be required every year, so the current quarterly options would be insufficient. | https://en.wikipedia.org/wiki?curid=25453500 |
11,681 | In April 2001, Rob Seaman of the National Optical Astronomy Observatory proposed that leap seconds be allowed to be added monthly rather than twice yearly. | https://en.wikipedia.org/wiki?curid=25453500 |
11,682 | A resolution has been adopted by the General Conference on Weights and Measures to redefine UTC and abolish leap seconds, but keep the civil second constant and equal to the SI second, so that sundials would slowly get further and further out of sync with civil time. The leap seconds will be eliminated by 2035. The resolution does not break the connection between UTC and UT1, but increases the maximum allowable difference. The details of what the maximum difference will be and how corrections will be implemented is left for future discussions. This will result in a shift of the sun's movements relative to civil time, with the difference increasing quadratically with time (i.e., proportional to elapsed centuries squared). This is analogous to the shift of seasons relative to the yearly calendar that results from the calendar year not precisely matching the tropical year length. This would be a change in civil timekeeping, and would have a slow effect at first, but becoming drastic over several centuries. UTC (and TAI) would be more and more ahead of UT; it would coincide with local mean time along a meridian drifting eastward faster and faster. Thus, the time system will lose its fixed connection to the geographic coordinates based on the IERS meridian. The difference between UTC and UT would reach 0.5 hours after the year 2600 and 6.5 hours around 4600. | https://en.wikipedia.org/wiki?curid=25453500 |
11,683 | ITU‑R Study Group 7 and Working Party 7A were unable to reach consensus on whether to advance the proposal to the 2012 Radiocommunications Assembly; the chairman of Study Group 7 elected to advance the question to the 2012 Radiocommunications Assembly (20 January 2012), but consideration of the proposal was postponed by the ITU until the World Radio Conference in 2015. This conference, in turn, considered the question, but no permanent decision was reached; it only chose to engage in further study with the goal of reconsideration in 2023. | https://en.wikipedia.org/wiki?curid=25453500 |
11,684 | A proposed alternative to the leap second is the leap hour or leap minute, which requires changes only once every few centuries. | https://en.wikipedia.org/wiki?curid=25453500 |
11,685 | Machine learning (ML) is a field of inquiry devoted to understanding and building methods that 'learn', that is, methods that leverage data to improve performance on some set of tasks. It is seen as a part of artificial intelligence. Machine learning algorithms build a model based on sample data, known as training data, in order to make predictions or decisions without being explicitly programmed to do so. Machine learning algorithms are used in a wide variety of applications, such as in medicine, email filtering, speech recognition, agriculture, and computer vision, where it is difficult or unfeasible to develop conventional algorithms to perform the needed tasks. | https://en.wikipedia.org/wiki?curid=233488 |
11,686 | A subset of machine learning is closely related to computational statistics, which focuses on making predictions using computers, but not all machine learning is statistical learning. The study of mathematical optimization delivers methods, theory and application domains to the field of machine learning. Data mining is a related field of study, focusing on exploratory data analysis through unsupervised learning. Some implementations of machine learning use data and neural networks in a way that mimics the working of a biological brain. In its application across business problems, machine learning is also referred to as predictive analytics. | https://en.wikipedia.org/wiki?curid=233488 |
11,687 | Learning algorithms work on the basis that strategies, algorithms, and inferences that worked well in the past are likely to continue working well in the future. These inferences can be obvious, such as "since the sun rose every morning for the last 10,000 days, it will probably rise tomorrow morning as well". They can be nuanced, such as "X% of families have geographically separate species with color variants, so there is a Y% chance that undiscovered black swans exist". | https://en.wikipedia.org/wiki?curid=233488 |
11,688 | Machine learning programs can perform tasks without being explicitly programmed to do so. It involves computers learning from data provided so that they carry out certain tasks. For simple tasks assigned to computers, it is possible to program algorithms telling the machine how to execute all steps required to solve the problem at hand; on the computer's part, no learning is needed. For more advanced tasks, it can be challenging for a human to manually create the needed algorithms. In practice, it can turn out to be more effective to help the machine develop its own algorithm, rather than having human programmers specify every needed step. | https://en.wikipedia.org/wiki?curid=233488 |
11,689 | The discipline of machine learning employs various approaches to teach computers to accomplish tasks where no fully satisfactory algorithm is available. In cases where vast numbers of potential answers exist, one approach is to label some of the correct answers as valid. This can then be used as training data for the computer to improve the algorithm(s) it uses to determine correct answers. For example, to train a system for the task of digital character recognition, the MNIST dataset of handwritten digits has often been used. | https://en.wikipedia.org/wiki?curid=233488 |
11,690 | The term "machine learning" was coined in 1959 by Arthur Samuel, an IBM employee and pioneer in the field of computer gaming and artificial intelligence. Also the synonym "self-teaching computers" were used in this time period. | https://en.wikipedia.org/wiki?curid=233488 |
11,691 | By the early 1960s an experimental "learning machine" with punched tape memory, called Cybertron, had been developed by Raytheon Company to analyze sonar signals, electrocardiograms, and speech patterns using rudimentary reinforcement learning. It was repetitively "trained" by a human operator/teacher to recognize patterns and equipped with a "goof" button to cause it to re-evaluate incorrect decisions. A representative book on research into machine learning during the 1960s was Nilsson's book on Learning Machines, dealing mostly with machine learning for pattern classification. Interest related to pattern recognition continued into the 1970s, as described by Duda and Hart in 1973. In 1981 a report was given on using teaching strategies so that a neural network learns to recognize 40 characters (26 letters, 10 digits, and 4 special symbols) from a computer terminal. | https://en.wikipedia.org/wiki?curid=233488 |
11,692 | Tom M. Mitchell provided a widely quoted, more formal definition of the algorithms studied in the machine learning field: "A computer program is said to learn from experience "E" with respect to some class of tasks "T" and performance measure "P" if its performance at tasks in "T", as measured by "P", improves with experience "E"." This definition of the tasks in which machine learning is concerned offers a fundamentally operational definition rather than defining the field in cognitive terms. This follows Alan Turing's proposal in his paper "Computing Machinery and Intelligence", in which the question "Can machines think?" is replaced with the question "Can machines do what we (as thinking entities) can do?". | https://en.wikipedia.org/wiki?curid=233488 |
11,693 | Modern-day machine learning has two objectives, one is to classify data based on models which have been developed, the other purpose is to make predictions for future outcomes based on these models. A hypothetical algorithm specific to classifying data may use computer vision of moles coupled with supervised learning in order to train it to classify the cancerous moles. A machine learning algorithm for stock trading may inform the trader of future potential predictions. | https://en.wikipedia.org/wiki?curid=233488 |
11,694 | As a scientific endeavor, machine learning grew out of the quest for artificial intelligence. In the early days of AI as an academic discipline, some researchers were interested in having machines learn from data. They attempted to approach the problem with various symbolic methods, as well as what was then termed "neural networks"; these were mostly perceptrons and other models that were later found to be reinventions of the generalized linear models of statistics. Probabilistic reasoning was also employed, especially in automated medical diagnosis. | https://en.wikipedia.org/wiki?curid=233488 |
11,695 | However, an increasing emphasis on the logical, knowledge-based approach caused a rift between AI and machine learning. Probabilistic systems were plagued by theoretical and practical problems of data acquisition and representation. By 1980, expert systems had come to dominate AI, and statistics was out of favor. Work on symbolic/knowledge-based learning did continue within AI, leading to inductive logic programming, but the more statistical line of research was now outside the field of AI proper, in pattern recognition and information retrieval. Neural networks research had been abandoned by AI and computer science around the same time. This line, too, was continued outside the AI/CS field, as "connectionism", by researchers from other disciplines including Hopfield, Rumelhart, and Hinton. Their main success came in the mid-1980s with the reinvention of backpropagation. | https://en.wikipedia.org/wiki?curid=233488 |
11,696 | Machine learning (ML),is reorganized as a separate field, started to flourish in the 1990s. The field changed its goal from achieving artificial intelligence to tackling solvable problems of a practical nature. It shifted focus away from the symbolic approaches it had inherited from AI, and toward methods and models borrowed from statistics, fuzzy logic, and probability theory. | https://en.wikipedia.org/wiki?curid=233488 |
11,697 | The difference between ML and AI is frequently misunderstood. ML learns and predicts based on passive observations, whereas AI implies an agent interacting with the environment to learn and take actions that maximize its chance of successfully achieving its goals. | https://en.wikipedia.org/wiki?curid=233488 |
11,698 | As of 2020, many sources continue to assert that ML remains a subfield of AI. Others have the view that not all ML is part of AI, but only an 'intelligent subset' of ML should be considered AI. | https://en.wikipedia.org/wiki?curid=233488 |
11,699 | Machine learning and data mining often employ the same methods and overlap significantly, but while machine learning focuses on prediction, based on "known" properties learned from the training data, data mining focuses on the discovery of (previously) "unknown" properties in the data (this is the analysis step of knowledge discovery in databases). Data mining uses many machine learning methods, but with different goals; on the other hand, machine learning also employs data mining methods as "unsupervised learning" or as a preprocessing step to improve learner accuracy. Much of the confusion between these two research communities (which do often have separate conferences and separate journals, ECML PKDD being a major exception) comes from the basic assumptions they work with: in machine learning, performance is usually evaluated with respect to the ability to "reproduce known" knowledge, while in knowledge discovery and data mining (KDD) the key task is the discovery of previously "unknown" knowledge. Evaluated with respect to known knowledge, an uninformed (unsupervised) method will easily be outperformed by other supervised methods, while in a typical KDD task, supervised methods cannot be used due to the unavailability of training data. | https://en.wikipedia.org/wiki?curid=233488 |
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