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Topic: Time scales

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In the News (Thu 18 Jul 19)

  Time Scales
Although the term GMT was not explicitly used, the standard time for legal purposes in the United States specified by 15USC261 (the Calder Act) was defined to be based on the mean astronomical time of meridians spaced at 15-degree intervals west of Greenwich; i.e., GMT.
Although the term GMT was not explicitly used, the standard time for legal purposes in the United States specified by 15USC261 was clarified and reaffirmed to be based on the mean solar time of meridians spaced at 15-degree intervals west of Greenwich; i.e., GMT.
This time scale is an effort to ascertain corrections to the values of TAI based on retrospective studies of the behavior of the clocks which have contributed to TAI.
www.ucolick.org /~sla/leapsecs/timescales.html   (13267 words)

The standard unit for time is the SI second, from which larger units are defined like the minute, hour, day, week, month, year, decade, and century.
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.
In physics, time is defined as the distance between events along the fourth axis of the spacetime manifold.
www.teachersparadise.com /ency/en/wikipedia/t/ti/time.html   (961 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.
However, it was widely desired to keep civil time synchronised with the Earth's rotation, and many uses of time signals (such as for navigation) relied on their closely matching Universal Time.
The time expressed in such a timezone differs from UTC in its minute number, hour number, and possibly date, but the second number is the same in all timezones.
en.wikipedia.org /wiki/Coordinated_Universal_Time   (2862 words)

 CalendarHome.com - Solar time - Calendar Encyclopedia   (Site not responding. Last check: 2007-10-30)
Apparent solar time is based on the apparent solar day, which is the interval between two successive returns of the Sun to the local meridian.
Mean solar time is artificial clock time adjusted via observations of the diurnal rotation of the fixed stars to agree with average apparent solar time.
Babylonian astronomers knew of the equation of time and were correcting for it as well as the different rotation rate of stars, sidereal time, to obtain a mean solar time much more accurate than their water clocks.
encyclopedia.calendarhome.com /Solar_time.htm   (595 words)

 Time Supplement [Internet Encyclopedia of Philosophy]
That is, time is a distinguished dimension of spacetime, not an arbitrary dimension.
Time dilation is not an illusion of perception; and it's not a matter of the second having different definitions in different reference frames.
Time dilation due to motion is relative in the sense that if your spaceship moves past mine so fast that I measure your clock to be running at half speed, then you will measure my clock to be running at half speed also, provided both of us are in inertial frames.
www.iep.utm.edu /ancillaries/time-sup.htm   (13066 words)

 Time scale - Wikipedia, the free encyclopedia
A time scale specifies divisions (scale) of time.
The geological time scale divides up the history of the Earth into scientifically meaningful periods.
Music may, however, exist "outside" of time when structured through "principles whose defnitions does not imply a temporal order", including scales and many other precompositional techniques, musical instruments, and aleatoric music.
en.wikipedia.org /wiki/Time_scale   (309 words)

Climate changes on all time scales because there are different mechanisms operating over different periods of times which "force" the climate.
Most of these mechanisms are entirely natural in origin, but over the last 20 years, concerns have grown that a man-made change in the composition of the atmosphere may be causing global warming.
Over the shortest time scales of centuries, decades and even individual years, global climate is influenced by changes in the amount of energy from the Sun and the effects of major volcanic eruptions.
www.ace.mmu.ac.uk /eae/Climate_Change/Older/Time.html   (344 words)

 Time Scales   (Site not responding. Last check: 2007-10-30)
International Atomic Time (TAI) is a uniform time scale with a unit of one SI second.
Universal Time (UT, UT1) is a non-uniform time scale tied to the Earth's rotation.
Barycentric Dynamical Time (TDB) was implemented in 1984 as the dynamical time scale for solar-system barycentric phenomena.
ana.lmsal.com /ana/ana/Time_Scales.html   (246 words)

 SOI-TN-94-116: Time Data Type & Representation
The expression of dates and times externally is complicated by the dual aims of supporting a broad variety of "natural" representations and of being able to use multiple time scales.
Note that TAI and TT are the only sensible time scales to use with this representation, as they are the only ones in which a day is always equal to 86,400 seconds (by definition).
The clock time is expressed in the customary colon-separated fields, with an optional decimal point and fractional part of a second.
soi.stanford.edu /general/TechNotes/94.116.html   (1883 words)

 [No title]
Whereas the Universal Time scale is obtained by counting cycles of the earth's rotation from some agreed-upon starting point, an atomic time scale can be obtained by counting cycles of a signal locked to some atomic resonance.
One should be especially cautious if the time interval of interest extends backward into a period where the world time system was not operating on the new UTC time scale (prior to 1972).
The UTC system was developed as a compromise between a purely uniform time scale for scientific applications and the non-uniform measurement of the earth's position for navigation and astronomy.
www.ieee-uffc.org /freqcontrol/fc_utc.html   (2038 words)

 Coordinated Universal Time - Voyager, the free encyclopedia   (Site not responding. Last check: 2007-10-30)
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.
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.
www.voyager.in /Coordinated_Universal_Time   (970 words)

 AMCA: Dynamic Equations on Time Scales by Martin Bohner   (Site not responding. Last check: 2007-10-30)
Time scales have been introduced in order to unify continuous and discrete analysis and in order to extend those theories to cases "in between".
This delta derivative is equal to the usual derivative if the time scale is the set of all real numbers, and it is equal to the usual forward difference operator if the time scale is the set of all integers.
The union of closed intervals (this time scale is interesting in population dynamics; for example, it can model insect populations that are continuous while in season, die out in say winter, while their eggs are incubating or dormant, and then hatch in a new season, giving rise to a nonoverlapping population).
at.yorku.ca /c/a/n/u/21.htm   (401 words)

 World Time Scales
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.
It became clear that shipping would benefit substantially from the establishment of a single "prime" meridian, and the subject was finally resolved in 1884 at a conference held in Washington, where the meridian passing through Greenwich was adopted as the initial or prime meridian for longitude and timekeeping.
physics.nist.gov /GenInt/Time/world.html   (646 words)

 Time and Freqyency Glossary, Local Time, UTC time, DUT1, Daylight Saving Time   (Site not responding. Last check: 2007-10-30)
This is a time scale based on atomic clocks, by definition cesium clocks.
Standard Time, (In Sweden it is named Normal time) The time used during the winter.
Note that the offset between Local time and UTC time is not constant, it varies in locations where Daylight Saving Time is used.
www.timing.se /words.html   (313 words)

 University of Bahçeşehir   (Site not responding. Last check: 2007-10-30)
The study of Dynamic Equations on Time Scales, which goes back to its founder Stefan Hilger (1988), is an area of mathematics that has recently received a lot of attention.
The general idea is to prove a result for a dynamic equation where the domain of the unknown function is a so-called time scale, which may be an arbitrary closed subset of the reals.
Dynamic equations on a time scale have an enormous potential for applications such as in population dynamics.
www.fed.bahcesehir.edu.tr /workshop/about.htm   (347 words)

 Time Scales
If this is your first time using Time Plot graphs, you may have encountered a problem where the times and dates at the bottom of the graph aren't displaying correctly.
Time scales are unique in that they also can have minor scale labels.
As mentioned in "", time scales employ a base unit of measurement to determine what the major and minor scale labels will be.
www.corda.com /docsource/doc5/combo/docs/design_guide/design_scales6.html   (983 words)

 Natural Climate Variability on Decade-to-Century Time Scales
Natural climate variability on decade-to-century time scales is best defined in terms of the bio-chemical-physical system that must be studied, the principal components of that system, the mechanisms active within each component, and the interactions between components.
Natural Climate Variability on Decade-to-Century Time Scales by the cooperative efforts of dynamic meteorologists and physical oceanographers, sustained by long-term scientific coordination and by relatively healthy and stable governmental support, both national and international.
Natural Climate Variability on Decade-to-Century Time Scales Records of past climate change, particularly those reflecting the pre-industrial era, must be actively sought out and refined as a source of valuable new data on the natural component of climate variability.
www.nap.edu /openbook.php?isbn=0309054494&page=1   (2112 words)

 Time Scales   (Site not responding. Last check: 2007-10-30)
There are a number of time scales that are relevant in ATM networks and there are very different approaches used to examine each of them.
This bit scale level is shown in Figure 1.12, and this is relevant at the physical medium sublayer and is on the sub micro-second scale.
When dealing with a particular time scale, especially the longer ones, it is important for simulations to make a number of approximations about the lower time scale effects.
www.eeng.dcu.ie /~murphyj/the/the/node18.html   (313 words)

Think of relative time as physical subdivisions of the rock found in the Earth's stratigraphy, and absolute time as the measurements taken upon those to determine the actual time which has expired.
It is important to realize that with new information about subdivision or correlation of relative time, or new measurements of absolute time, the dates applied to the time scale can and do change.
The time scale is depicted in its traditional form with oldest at the bottom and youngest at the top -- the present day is at the zero mark.
www.geo.ucalgary.ca /~macrae/timescale/timescale.html   (665 words)

 metas: Time and Frequency - Time scales
The UT0 time unit is the average duration of a solar day (based on the hypothetical mean sun), as measured at the Greenwich Observatory (zero meridian).
International Atomic Time: TAI is based on the atomic definition of the second and is maintained and disseminated by the International Bureau of Weights and Measures from the data collected from c.
Since the two time scales UTC and UT1 are based on completely different definitions, their difference is not constant.
www.metas.ch /en/labors/4/zeitskalen.html   (273 words)

 Time scales - The Great American RoadTrip Forum
Any advice that seasoned travelers can give about the kind of time scales involved in going east west (or vice versa) or top to bottom, how much driving in a day, days off etc would be most gratefully received.
However, time and space are relative -- I have driven hundreds of thousands of miles in recent years and figure I have seen something between 10% and 15% of the USA.
I would choose either the eastern or western US because 4 weeks is not a lot of time to visit the whole United States unless you want to spend all the time in your car.
www.roadtripamerica.com /forum/showthread.php?t=7142   (687 words)

 Natural variability of atmospheric temperatures and geomagnetic intensity over a wide range of time scales -- Pelletier ...
intensity from time scales of 1 (Myr) to 100 yr.
The power-spectral density S is given as a function of frequency for time scales of 500 yr to 200 kyr.
(29) time scale and that of the binormal 1/f noise model of intensity variations.
www.pnas.org /cgi/content/full/99/suppl_1/2546   (4776 words)

 USGS Geology in the Parks
These time scales are drawn to scale so you can compare the relative lengths of geologic time divisions.
Notice the immense amount of time that passed prior to the explosion of life that took place at the beginning of the Phanerozoic Eon, about 570 million years ago.
scale, 10,000 years is such a brief period that it too small to draw!
wrgis.wr.usgs.gov /docs/parks/gtime/gtime2.html   (281 words)

 BIPM - time
International Atomic Time (TAI) is the uniform time scale; it is kept as close as possible to the second of the SI.
The atomic time scales TAI and UTC are disseminated monthly through the BIPM Circular T.
Other activities related to the time scales are developed in the section; these contribute to improving the calculation algorithms and increasing knowledge about time transfer techniques.
www.bipm.org /en/scientific/tai   (231 words)

 Natural Climate Variability on Decade-to-Century Time Scales
Natural variations with time scales of decades to centuries may well be masking anthropogenic climate changes that have already been effected, and will continue to do so.
Even after the time scale of interest has been defined, it may be difficult to recognize and classify natural variability as evidenced in modern instrumental observations, because anthropogenic change may already have contaminated them significantly.
The ultimate goals—determining the characteristics of natural climate variability, predicting climate changes on decade-to-century scales, and assessing the effects of human activities—will be realized only through the cooperation of scientists and national and international agencies in all the fields represented.
www.nap.edu /openbook.php?isbn=0309054494&page=5   (2146 words)

 Lift Truck Scales Save Time and Money   (Site not responding. Last check: 2007-10-30)
The scales are built to capacity of the lift trucks, and require no alteration of the existing carriages.
Accuracy: Digital accuracy to 1/10th of 1% of scale capacity with the lift truck mast in a level position (Note: An option is available that would automatically maintain this high degree of accuracy even in an out-of-level condition).
Durability: Filing Lift Truck Scales utilize a system of multiple flexures, which absorbs the constant shock of load-bearing while transferring the weight to a single-cell load mechanism.
www.filing-lts.com /LTS/lift.html   (648 words)

 Astrophysical Ages and Time Scales Conference
Astrophysical ages and time scales provide the basis for a host of studies in astronomy, ranging from the energetics of supernovae to the masses of brown dwarfs, from the concordance of cosmological parameters to the abundances of the elements.
The results of these myriad observational and theoretical advances are now becoming precise enough that conflicts have arisen, for example the well-known tension between the expansion age of the Universe and the ages of globular clusters.
We are organizing a conference to review measurements of astrophysical ages and time scales, including the latest state-of-the-art results, to focus on areas where greater precision is needed, and to expose and discuss conflicts in current astrophysical ages and time scales from solar system formation time scales through the age of the Universe.
www.gemini.edu /science/timescales   (321 words)

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