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Topic: International Atomic Time

Ads by Google      Universal Time - Wikipedia, the free encyclopedia Nowadays, UT in relation to International Atomic Time (TAI) is determined by Very Long Baseline Interferometry (VLBI) observations of distant quasars, a method which has an accuracy of micro-seconds. Barycentric Dynamical Time (TDB), a form of atomic time, is now used in the construction of the ephemerides of the planets and other solar system objects, for two main reasons. UTC (Coordinated Universal Time) is the international standard on which civil time is based. http://en.wikipedia.org/wiki/Universal_Time   (1309 words)      Coordinated Universal Time - Open Encyclopedia UTC bases time measurement on atomic standards rather than GMT's celestial ones. Because the rotation of the Earth slows down, GMT lags behind atomic time, measured by atomic clocks. International standard UTC time can only be determined to the highest precision after the fact, as atomic time is determined by the reconciliation of the observed differences between an ensemble of atomic clocks maintained by a number of national time bureaux. http://open-encyclopedia.com/Coordinated_Universal_Time   (637 words)      The Time of Internet - Universal Coordinated Time The UTC time flows essentially like the international atomic time (TAI), when the difference with the universal time (UT) approach 1 second, it is inserted 1 second, called leap second, into the UTC time scale in such a way to keep this difference below 0.9 second. Since 1900, the year when 1 mean solar second= 1 atomic second, until today, the mean solar day is grown 0.002 atomic second longer and consequently the universal time has a delay of about 1 second every 500 days in comparison with the international atomic time. To take into account this progressive phase displacement between the two time scales and to not give up the high accuracy offered by atomic clocks, in 1972 it was found a compromise that led to the definition of the Universal Coordinated Time (UTC), currently used as the official time measurement in the world. http://toi.iriti.cnr.it/uk/utctime.html   (357 words)      Coordinated Universal Time The reference used is International Atomic Time (TAI), a timescale calculated at the BIPM using, in 2000, data from some two hundred atomicclocks in over fifty national laboratories. Atomic Clock Time Servers For Computers and Networks Atomic Clock Time Servers For Computer and Networks http://www.taaclock.fsnet.co.uk/atomic-clock/atomic_time.htm   (435 words)      Time - Free Encyclopedia There are several continuous time scales in current use: Universal Time, International Atomic Time (TAI), which is the basis for other time scales, Coordinated Universal Time (UTC), which is the standard for civil time, Terrestrial Time (TT), etc. Mankind has invented calendars to track the passages of days, weeks, months, and years. The work humanity has done to increasingly understand the nature and measurement of time, through the work of making and improving calendars and clocks, has been a major engine of scientific discovery. also-- block time, Network Time Protocol, philosophy of physics, real-time, spacetime, The Time Machine, time and frequency transfer, time code, time domain, time machine, Time Magazine, Peter Lynds and time, time management, time travel, time-sharing, the age of the Earth, orders of magnitude (time), eternity, time capsule, Wikibooks:English:Time http://www.wacklepedia.com/t/ti/time.html   (845 words)      Coordinated Universal Time - Wikipedia, the free encyclopedia UTC is derived from International Atomic Time (TAI), which is a time scale tracking proper time on the surface of the Earth with no reference to the rotation of the Earth. In particular, the Network Time Protocol, designed to synchronize the clocks of many computers over the Internet (usually to that of a known accurate atomic clock), uses UTC. Because UTC is a discontinuous timescale, it is not possible to compute the exact time interval elapsed between two UTC timestamps without consulting a table that describes how many leap seconds occurred during that interval. http://en.wikipedia.org/wiki/Coordinated_Universal_Time   (2833 words)      Coordinated Universal Time --  Encyclopædia Britannica International Atomic Time (abbreviated TAI, from the name in French) is based on a system consisting of about six primary, laboratory-constructed, cesium-beam atomic... Universal Time replaced the designation Greenwich Mean Time in 1928; it is now used to denote the solar time (q.v.) when an accuracy of about one second suffices. Mean solar time, kept by most clocks and watches, is the solar time that would be measured by observation if the Sun traveled at a uniform apparent speed throughout the year rather than, as it actually does, at a slightly... http://www.britannica.com/eb/article-9026164   (883 words)      GPS World: Time and frequency dissemination: advances in GPS transfer techniques Once a month, BIPM uses these data to produce the standard international references for frequency and time, International Atomic Time (TAI) and UTC, which is equal in rate to TAI, but adjusted by an integer number of seconds to account for variations in the rotation of the Earth. A timing user operating from a known fixed location can derive time from GPS using just one satellite, and with averaging, a timing accuracy of a few nanoseconds is possible. In any event, the intention has always been that time would be derived by first computing the user position and time offset relative to GPS Time, and then applying the UTC correction terms, including the integer seconds offset. http://www.findarticles.com/p/articles/mi_m0BPW/is_11_15/ai_n9770116   (1410 words)      Systems of Time TAI is the International Atomic Time scale, a statistical timescale based on a large number of atomic clocks. Atomic Time, with the unit of duration the Systeme International (SI) second defined as the duration of 9,192,631,770 cycles of radiation corresponding to the transition between two hyperfine levels of the ground state of cesium 133. Barycentric Dynamical Time (TDB), is the independent argument of ephemerides and dynamical theories that are referred to the solar system barycenter. http://tycho.usno.navy.mil/systime.html   (560 words)      Coordinated Universal Time (UTC) The Temps Atomique International (TAI) is the atomic time scale derived by the Bureau International des Poids et Mesures (BIPM); its unit interval is exactly one second of the Systeme International d'Unites (SI) at sea level. It is a compromise between the highly stable atomic time and the irregular earth rotation. Universal Time UT1 is the time of the earth clock, which performs one revolution in about 24h.It has short term instabilities at the level of 10 http://www.iers.org/iers/earth/rotation/utc/utc.html   (288 words)      Coordinated Universal Time See also International Atomic Time; Universal Time; ZULU Time. Coordinated Universal Time (UTC) differs from International Atomic Time by an integral number of seconds; it is maintained within 0.9 seconds of UT1 (see Universal Time) by introduction of Leap Seconds. (DOD) An atomic time scale that is the basis for broadcast time signals. http://www.dtic.mil/doctrine/jel/doddict/data/c/01317.html   (97 words)      Universal Time TAI, International Atomic Time, which is calculated statistically by the BIPM from results of atomic clocks maintained by various nations all over the world. The unpredictable addition of leap-seconds, however, creates a problem for computer timekeeping, especially Global Positioning Systems, resulting in a call for broadcasting some form of atomic time, not UTC. Later the IAU decided that as of 1 January 1956, there would be three versions of Universal Time (the CGPM adopted these in 1960). http://www.sizes.com/time/time_universal.htm   (848 words)      Time Standards Coordinated Universal Time (UTC) is a coordinated time scale maintained by the Bureau International des Poids et Mesures (BIPM), which forms the basis of a coordinated dissemination of standard frequencies and time signals. Scientists try to keep the atomic clocks, which are based on the vibration rates of cesium or hydrogen atoms, within nine-tenths of a second of the Earth's rotation time. H = 3 means that the hardware or software has failed and that the time error is unknown. http://www.beaglesoft.com/mainfaqtime.htm   (2368 words)      World Time Scales In an earlier decision prompted by their own interests and by pressures for a standard timekeeping system from the scientific community — meteorologists, geophysicists and astronomers — the U.S. railroad industry anticipated the international accord when they implemented a "Standard Railway Time System" on November 18, 1883. A compromise time scale was eventually devised, and on January 1, 1972, the new Coordinated Universal Time (UTC) became effective internationally. UTC runs at the rate of the atomic clocks, but when the difference between this atomic time and one based on the Earth approaches one second, a one second adjustment (a "leap second") is made in UTC. http://physics.nist.gov/GenInt/Time/world.html   (646 words)      Time Card - Best prices There are several continuous time scales in current use: universal time, international atomic time tai, which is the basis for other time scales, coordinated universal time utc, which is the basis for civil time, terrestrial time tt, etc humankind has invented calendars to track the passages of days, weeks, months, and years. On the other hand, a large number of biometric devices based on retinal scans have been installed in prisons and other highly secure environments. Voice recognition gives a computer the ability to understand spoken instructions. http://www.timeclockeshop.com/Time-Card.html   (646 words)      USNO Preprint Library Near-term Time Transfer Technologies and International Atomic Time (TAI) Time Transfer Methodologies for International Atomic Time (TAI) On Optimizing the Configuration of Time-Transfer Links Used to Generate TAI http://ad.usno.navy.mil/edboard/preprints.html   (453 words)      TWSTFT The International Bureau of Weights and Measures (BIPM) outside Paris make use of the technique in cooperation with national laboratories to compare atomic clocks as well as for the calculation of the international atomic time scales TAI and UTC. The technique is active in contrast to GPS, that is, time signals are transferred between laboratories via satellite transponders. TWSTFT is in this consideration a more accurate complement to the more common time transfer methods utilizing GPS. http://www.sp.se/metrology/timefreq/eng/TWSTFT.htm   (221 words)      International Association of Geodesy Reference time scales International Atomic Time (TAI) and Universal Coordinated Time (UTC) have been computed regularly and have been published in the monthly BIPM Circular T. Since April 2000 two modifications had been implemented: a new model to characterise the instability of the free atomic scale EAL, and a more complete representation of the uncertainty of the deviation of the TAI scale interval relative to that of the Terrestrial Time TT. Following the recommendations of the Consultative Committee on Time and Frequency, changes were implemented to render the data used in TAI, as well as the results, more accessible to the users and to make the procedures of calculation even more transparent and traceable. http://www.astro.oma.be/IAG/SV9_NEW.htm   (790 words)      Coordinated Universal Time (UTC) NOTE: The word order of Coordinated Universal Time versus the UTC abbreviation (out of order) is intentional -- established by the Bureau International de l'Heure (International Time Bureau) as a language-independent abbreviation. UT -- An abbreviation (for Universal Time) that should be used to show approximation of all the below. Atomic clock-- usually multiple clocks that count seconds (average of all clocks in system) based on the frequency of the cesium 133 atom (Cs) which oscillates at 9,192,631,770 Hertz. http://copradar.com/preview/timeuct.html   (467 words)      UTC - Coordinated Universal Time UTC is defined such that it differs from International Atomic Time (IAT) by an exact whole number of seconds. the rate is defined relative to atomic clock rate but the epoch is defined relative to Universal Time. The accepted abbreviation for "Universal Coordinated Time." This is standard time in Greenwich, England, which is used as a reference time for day and date calculations. http://www.auditmypc.com/acronym/UTC.asp   (323 words)      Two-Way Satellite Time and Frequency Transfer - Wikipedia, the free encyclopedia As of 2003 TWSTFT is being evaluated as an alternative to be used by the Bureau International des Poids et Mesures in the determination of International Atomic Time (TAI), as a complement to the current standard method of simultaneous observations of GPS transmissions. Two-Way Satellite Time and Frequency Transfer (TWSTFT) is a high-precision long distance time and frequency transfer mechanism used between time bureaux to determine and distribute time and frequency standards. This page was last modified 19:17, 25 April 2005. http://en.wikipedia.org/wiki/Two-Way_Satellite_Time_and_Frequency_Transfer   (109 words)      Coordinated Universal Time Definition. Define Coordinated Universal Time. What is Coordinated Universal Time? UTC is derived from {International Atomic Time} (TAI) by the addition of a whole number of "leap seconds" to synchronise it with {Universal Time} 1 (UT1), thus allowing for the eccentricity of the Earth's orbit, the rotational axis tilt (23.5 degrees), but still showing the Earth's irregular rotation, on which UT1 is based. It is used in aeroplane and ship navigation, where it also sometimes known by the military name, "Zulu time". There are no recommended books at this time. http://www.learnthat.com/define/view.asp?id=1477   (236 words)      Definition: coordinated universal time Coordinated Universal Time (UTC): Time scale, based on the second (SI), as defined and recommended by the CCIR, and maintained by the Bureau International des Poids et Mesures (BIPM). Note 4: Adjustments to the atomic, i.e., UTC, time scale consist of an occasional addition or deletion of one full second, which is called a leap second. Historically, adjustments, when necessary, have usually consisted of adding an extra second to the UTC time scale in order to allow the rotation of the Earth to "catch up." Therefore, the last minute of the UTC time scale, on the day when an adjustment is made, will have 59 or 61 seconds. http://www.its.bldrdoc.gov/fs-1037/dir-009/_1277.htm   (257 words)      ipedia.com: Time and frequency transfer Article The technique is commonly used for creating and distributing standard time scales such as International Atomic Time (TAI). Time and frequency transfer describes mechanisms for comparing measurements of time and frequency from one location to another. Time transfer by simultaneous observation of radio astronomy signals http://www.ipedia.com/time_and_frequency_transfer.html   (118 words)      Coordinated Universal Time - Wikipedia, the free encyclopedia Time zones around the world are expressed as positive and negative offsets from UT. UTC differs by an integral number of seconds from International Atomic Time (TAI), as measured by atomic clocks and a fractional number of seconds from UT. International standard UTC time can only be determined to the highest precision after the fact, as atomic time is determined by the reconciliation of the observed differences between an ensemble of atomic clocks maintained by a number of national time bureaus. UTC is a hybrid time scale: the rate of UTC is based on atomic frequency standards but the epoch of UTC is synchronized to remain close to astronomical UT. http://en.wikipedia.org/wiki/UTC   (866 words)      Coordinated Universal Time - Wikipedia, the free encyclopedia International standard UTC time can only be determined to the highest precision after the fact, as atomic time is determined by the reconciliation of the observed differences between an ensemble of atomic clocks maintained by a number of national time bureaus. Time zones around the world are expressed as positive and negative offsets from UT. UTC differs by an integral number of seconds from International Atomic Time (TAI), as measured by atomic clocks and a fractional number of seconds from UT. UTC is a hybrid time scale: the rate of UTC is based on atomic frequency standards but the epoch of UTC is synchronized to remain close to astronomical UT. http://en.wikipedia.org/wiki/UTC   (866 words)      usatomicclocktime Contact us Search: > You are here: scientific work> time> International Atomic Time International Atomic Time Summary International Atomic Time Clock comparisons Joint... This "Us Atomic Clock Time" information is definitely "cutting edge." Whenever you want to come back to this fun "Us Atomic Clock Time" site just click here and you'll be blown away by what happens next. Libby (US), for “atomic time clock” to measure age of objects by measuring their radioactivity Physics: Donald A. Glaser (US), for invention of ""bubble chamber"" to study subatomic particles... http://www.hrtimeclock.com/usatomicclocktime   (866 words)      Coordinated Universal Time - definition of Coordinated Universal Time in Encyclopedia International standard UTC time can only be determined to the highest precision after the fact, as atomic time is determined by the reconciliation of the observed differences between an ensemble of atomic clocks maintained by a number of national time bureaux. Coordinated Universal Time or UTC, also sometimes referred to as " Zulu time ", the basis for civil time, differs by an integral number of seconds from atomic time and a fractional number of seconds from UT1. The UTC time zone is sometimes denoted by the letter Z since the equivalent nautical time zone (GMT) has been denoted by Z since about 1950, and by a "zone description" of zero hours since 1920. http://encyclopedia.laborlawtalk.com/Coordinated_Universal_Time   (866 words)      NodeWorks - Encyclopedia: Coordinated Universal Time International standard UTC time can only be determined to the highest precision after the fact, as atomic time is determined by the reconciliation of the observed differences between an ensemble of atomic clocks maintained by a number of national time bureaus. Time zones around the world are expressed as positive and negative offsets from UT. UTC differs by an integral number of seconds from atomic time and a fractional number of seconds from UT1. UTC also stands for the University of Tennessee at Chattanooga Coordinated Universal Time or UTC, also sometimes referred to as "Zulu time", is an atomic realization of Universal Time or Greenwich mean time, the astronomical basis for civil time. http://pedia.nodeworks.com/C/CO/COO/Coordinated_Universal_Time   (574 words)      Time Scales Despite resolutions calling for an international and interdisciplinary committee to study options for radio broadcast time signals, in 1969 CCIR study committee VII-1 unilaterally deemed that radio time signals should broadcast atomic seconds with occasional full second leaps. In the new, globally self-consistent world of coordinates based on VLBI and satellite geodesy the longitude of Greenwich ceased to be zero, and the timekeeping role formerly held by the Greenwich meridian was conceptually assumed by the nearby, but tectonically moving international meridian. Other localities changed their laws to adopt UTC as the basis for legal time after the IAU, CGPM, and other international organizations recommended its use. http://www.ucolick.org/~sla/leapsecs/timescales.html   (12416 words)

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