Misplaced Pages

Time: Difference between revisions

Article snapshot taken from Wikipedia with creative commons attribution-sharealike license. Give it a read and then ask your questions in the chat. We can research this topic together.
Browse history interactively← Previous editNext edit →Content deleted Content addedVisualWikitext
Revision as of 17:23, 27 November 2008 view sourceJimWae (talk | contribs)Extended confirmed users, Pending changes reviewers, Rollbackers37,709 edits Undid revision 254418314 by Solardave123 (talk) ESSAY or POETRY← Previous edit Revision as of 08:19, 28 November 2008 view source 68.83.189.23 (talk) ←Replaced content with 'Time is something you cannot stop referrence - you cannot stop sams weight gain time started in 2008 when members of BMJT decides that a source of time wa...'Next edit →
Line 1: Line 1:
Time is something you cannot stop
:''For other uses, see ]
] shown in ].


referrence - you cannot stop sams weight gain
The motions of ] and ] have demonstrated and symbolized time throughout humanity's existence.<ref name="Rudgley">{{cite book | title=The Lost Civilizations of the Stone Age| last=Rudgley| first=Richard| authorlink=Richard Rudgley| year=1999| pages=86-105| publisher=Simon & Schuster| location=New York}}</ref>]]
] can be used to keep track of elapsed time. It also concretely represents the ] as being between the ] and the ].]]


'''Time''' is a component of a ] used to sequence events, to compare the durations of events and the intervals between them, and to quantify the motions of objects. Time has been a major subject of ], ], and ], but defining time in a non-controversial manner applicable to all fields of study has consistently eluded the greatest scholars.


time started in 2008
In ] and other sciences, ''time'' is considered one of the few ].<ref name="Trialogue">{{cite paper
| author = Duff, Michael J.
| coauthors = Okun, Lev B.; Veneziano, Gabriele
| title = Trialogue on the number of fundamental constants
| version =
| publisher = Institute of Physics Publishing for SISSA/ISAS
| month = March | year = 2002
| url = http://jhep.sissa.it/archive/papers/jhep032002023/jhep032002023.pdf
| format = PDF
| accessdate = 2008-02-02 }} p. 17. "I only add to this the observation that relativity and quantum mechanics provide, in string theory, units of length and time which look, at present, more fundamental than any other."</ref> ''Time'' is used to define other quantities – such as ] – and defining ''time'' in terms of such quantities would result in ].<ref name="TrialogueP3">Duff, Okun, Veneziano, ''ibid.'' p. 3. "There is no well established terminology for the fundamental constants of Nature. … The absence of accurately defined terms or the uses (i.e. actually misuses) of ill-defined terms lead to confusion and proliferation of
wrong statements."</ref> An ] of time, wherein one says that observing a certain number of repetitions of one or another standard cyclical event (such as the passage of a free-swinging pendulum) constitutes one standard unit such as the ], is highly useful in the conduct of both advanced experiments and everyday affairs of life. The operational definition leaves aside the question whether there is something called time, apart from the counting activity just mentioned, that flows and that can be measured. Investigations of a single continuum called ] brings the nature of time into association with related questions into the nature of ], questions that have their roots in the works of early students of ].


when members of BMJT decides that a source of time was needed to count on.]
Among prominent philosophers, there are two distinct viewpoints on ''time''.
One view is that time is part of the fundamental structure of the ], a ] in which events occur in ]. ], in this view, becomes a possibility as other "times" persist like frames of a film strip, spread out across the time line. ] subscribed to this ] view, and hence it is sometimes referred to as ].<ref name=Rynasiewicz>
{{cite web
|url=http://plato.stanford.edu/entries/newton-stm/
|title=Newton's Views on Space, Time, and Motion
|date=2004-08-12
|copyright=2004
|first=Robert : Johns Hopkins University
|last=Rynasiewicz
|publisher=Stanford University
|work=Stanford Encyclopedia of Philosophy
|quote=Newton did not regard space and time as genuine substances (as are, paradigmatically, bodies and minds), but rather as real entities with their own manner of existence as necessitated by God's existence... To paraphrase: Absolute, true, and mathematical time, from its own nature, passes equably without relation the anything external, and thus without reference to any change or way of measuring of time (e.g., the hour, day, month, or year).
|accessdate=2008-01-10}}
</ref><ref>
{{cite encyclopedia
|url=http://plato.stanford.edu/entries/time/#3
|last=Markosian
|first=Ned
|title=Time
|encyclopedia=The Stanford Encyclopedia of Philosophy (Winter 2002 Edition)
|editor=Edward N. Zalta
|quote=The opposing view, normally referred to either as “Platonism with Respect to Time” or as “Absolutism with Respect to Time,” has been defended by Plato, Newton, and others. On this view, time is like an empty container into which events may be placed; but it is a container that exists independently of whether or not anything is placed in it.
|accessddate=2008-01-18}}</ref> The opposing view is that ''time'' does not refer to any kind of "container" that events and objects "move through", nor to any entity that "flows", but that it is instead part of a fundamental intellectual structure (together with ] and ]) within which humans sequence and compare events. This second view, in the tradition of ]<ref name=Burnham>{{cite web
|url=http://www.iep.utm.edu/l/leib-met.htm#H7
|title=Gottfried Wilhelm Leibniz (1646-1716) Metaphysics - 7. Space, Time, and Indiscernibles
|first=Douglas : Staffordshire University
|last=Burnham
|year=2006
|work=The Internet Encyclopedia of Philosophy
|quote=First of all, Leibniz finds the idea that space and time might be substances or substance-like absurd (see, for example, "Correspondence with Clarke," Leibniz's Fourth Paper, §8ff). In short, an empty space would be a substance with no properties; it will be a substance that even God cannot modify or destroy.... That is, space and time are internal or intrinsic features of the complete concepts of things, not extrinsic.... Leibniz's view has two major implications. First, there is no absolute location in either space or time; location is always the situation of an object or event relative to other objects and events. Second, space and time are not in themselves real (that is, not substances). Space and time are, rather, ideal. Space and time are just metaphysically illegitimate ways of perceiving certain virtual relations between substances. They are phenomena or, strictly speaking, illusions (although they are illusions that are well-founded upon the internal properties of substances).... It is sometimes convenient to think of space and time as something "out there," over and above the entities and their relations to each other, but this convenience must not be confused with reality. Space is nothing but the order of co-existent objects; time nothing but the order of successive events. This is usually called a relational theory of space and time.
|accessdate=2008-01-10}}</ref>
and ],<ref name=Mattey>
{{cite web
|url=http://www-philosophy.ucdavis.edu/mattey/kant/TIMELEC.HTM
|title=Critique of Pure Reason, Lecture notes: Philosophy 175 UC Davis
|date=1997-01-22
|last=Mattey
|first=G. J. : UC Davis
|quote=What is correct in the Leibnizian view was its anti-metaphysical stance. Space and time do not exist in and of themselves, but in some sense are the product of the way we represent things. The are ideal, though not in the sense in which Leibniz thought they are ideal (figments of the imagination). The ideality of space is its mind-dependence: it is only a condition of sensibility.... Kant concluded "absolute space is not an object of outer sensation; it is rather a fundamental concept which first of all makes possible all such outer sensation."...Much of the argumentation pertaining to space is applicable, mutatis mutandis, to time, so I will not rehearse the arguments. As space is the form of outer intuition, so time is the form of inner intuition.... Kant claimed that time is real, it is "the real form of inner intuition."
|accessdate=2008-01-10
}}</ref><ref name=McCormick>
{{cite web
|title=Immanuel Kant (1724-1804) Metaphysics : 4. Kant's Transcendental Idealism
|url=http://www.iep.utm.edu/k/kantmeta.htm#H4
|work=The Internet Encyclopedia of Philosophy
|first=Matt : California State University, Sacramento
|last=McCormick
|year=2006
|quote=Time, Kant argues, is also necessary as a form or condition of our intuitions of objects. The idea of time itself cannot be gathered from experience because succession and simultaneity of objects, the phenomena that would indicate the passage of time, would be impossible to represent if we did not already possess the capacity to represent objects in time.... Another way to put the point is to say that the fact that the mind of the knower makes the a priori contribution does not mean that space and time or the categories are mere figments of the imagination. Kant is an empirical realist about the world we experience; we can know objects as they appear to us. He gives a robust defense of science and the study of the natural world from his argument about the mind's role in making nature. All discursive, rational beings must conceive of the physical world as spatially and temporally unified, he argues.
|accessdate=2008-01-10}}
</ref>
holds that ''time'' is neither an event nor a thing, and thus is not itself measurable nor can it be traveled.


Above is a cock clock!
Temporal measurement has occupied scientists and ]s, and was a prime motivation in ] and ].
Periodic events and periodic motion have long served as standards for units of time. Examples include the apparent motion of the sun across the sky, the phases of the moon, the swing of a pendulum, and the beat of a heart. Currently, the international unit of time, the ], is defined in terms of radiation emitted by ] atoms (see ]). Time is also of significant social importance, having economic value ("]") as well as personal value, due to an ] of the limited time in each day and in ].


==Temporal measurement==
Temporal measurement, or ], takes two distinct period forms: the ], a mathematical abstraction for calculating extensive periods of time,<ref name="Richards">{{cite book | title=Mapping Time: The Calendar and its History| last=Richards| first=E. G.| authorlink=| year=1998| pages=3-5| publisher=Oxford University Press}}</ref> and the ], a concrete mechanism that counts the ongoing passage of time. In day-to-day life, the clock is consulted for periods less than a day, the calendar, for periods longer than a day. The number (as on a clock dial or calendar) that marks the occurrence of a specified event as to hour or date is obtained by counting from a fiducial epoch—a central reference point.


-BMJT
===History of the calendar===
{{main|Calendar}}
Artifacts from the ] suggest that the moon was used to calculate time as early as 12,000, and possibly even 30,000 ].<ref name="Rudgley" />

The ]ian civilization of approximately 2000 BC introduced the ] system based on the number 60. 60 seconds in a minute, 60 minutes in an hour – and possibly a calendar with 360 (60x6) days in a year (with a few more days added on).
Twelve also features prominently, with roughly 12 hours of day and 12 of night, and 12 months in a year (with 12 being 1/5 of 60).<!--- use of 60 could not have appeared until people started using minutes - which they would not have done with sundials --->

The reforms of ] in 45 BC put the ] on a ]. This ] was faulty in that its ] still allowed the astronomical ]s and ]es to advance against it by about 11 minutes per year. ] introduced a correction in 1582; the ] was only slowly adopted by different nations over a period of centuries, but is today the one in most common use around the world.

===History of time measurement devices===
] in ] (1833)]]
{{main|History of timekeeping devices}}{{seealso|Clock}}

A large variety of ]s have been invented to measure time. The study of these devices is called ].

An ]ian device dating to c.1500 BC, similar in shape to a bent ], measured the passage of time from the shadow cast by its crossbar on a non-linear rule. The T was oriented eastward in the mornings. At ], the device was turned around so that it could cast its shadow in the evening direction.<ref>Barnett, Jo Ellen ''Time's Pendulum: The Quest to Capture Time—from Sundials to Atomic Clocks'' Plenum, 1998 ISBN 0-306-45787-3 p.28</ref>

A ] uses a ] to cast a shadow on a set of markings which were calibrated to the ]. The position of the shadow marked the hour in ].

The most precise timekeeping devices of the ancient world were the ] or ''clepsydra'', one of which was found in the tomb of Egyptian pharaoh ] (1525–1504 BC). They could be used to measure the hours even at night, but required manual timekeeping to replenish the flow of water. The ] and ] regularly maintained timekeeping records as an essential part of their astronomical observations. ] and ] in particular made improvements on the use of water clocks up to the Middle Ages.<ref>Barnett, ''ibid'', p.37</ref>

The Arab engineers also invented the first mechanical clocks to be driven by ] and ]s in the 11th century.<ref name=Salim>Professor ] (2006), ''1001 Inventions: Muslim Heritage in Our World'', FSTC, ISBN 0955242606</ref><ref name="Where the heart is">, ''1001 Inventions: Muslim Heritage in Our World'', 2006</ref><ref name=Hassan>], , ''History of Science and Technology in Islam''.</ref> Also in the 11th century, the ] and ] invented the first mechanical clocks to be driven by an ] mechanism.

]]]
The ] uses the flow of sand to measure the flow of time. They were used in navigation. ] used 18 glasses on each ship for his circumnavigation of the globe (1522).<ref>Laurence Bergreen, ''Over the Edge of the World: Magellan's Terrifying Circumnavigation of the Globe'', HarperCollins Publishers, 2003, hardcover 480 pages, ISBN 0-06-621173-5</ref>

Incense sticks and candles were, and are, commonly used to measure time in temples and churches across the globe. Waterclocks, and later, mechanical clocks, were used to mark the events of the abbeys and monasteries of the Middle Ages. ] (1292–1336), abbot of St. Alban's abbey, famously built a mechanical clock as an astronomical ] about 1330.<ref>North, J. (2004) ''God's Clockmaker: Richard of Wallingford and the Invention of Time''. Oxbow Books. ISBN 1-85285-451-0</ref><ref>Watson, E (1979) "The St Albans Clock of Richard of Wallingford". ''Antiquarian Horology'' 372-384.</ref>

The English word ] probably comes from the Middle Dutch word "klocke" which is in turn derived from the mediaeval Latin word "clocca", which is ultimately derived from Celtic, and is cognate with French, Latin, and German words that mean ]. The passage of the hours at sea were marked by bells, and denoted the time (see ]). The hours were marked by bells in the abbeys as well as at sea.

]
Clocks can range from ]es, to more exotic varieties such as the ]. They can be driven by a variety of means, including gravity, springs, and various forms of electrical power, and regulated by a variety of means such as a ].

A ] is a portable timekeeper that meets certain precision standards. Initially, the term was used to refer to the ], a timepiece used to determine ] by means of ]. More recently, the term has also been applied to the ], a ] that meets precision standards set by the Swiss agency ].

The most accurate timekeeping devices are ]s, which are accurate to seconds in many millions of years,<ref>{{cite news |url=http://www.canada.com/vancouversun/news/story.html?id=e24ccfa7-44eb-40b7-8b67-daf8263569ff |title=New atomic clock can keep time for 200 million years: Super-precise instruments vital to deep space navigation |date=2008-02-16 |publisher=Vancouver Sun |accessdate=2008-02-16}}</ref> and are used to calibrate other clocks and timekeeping instruments.
Atomic clocks use the spin property of atoms as their basis, and since 1967, the International System of Measurements bases its unit of time, the second, on the properties of ] atoms. ] defines the second as 9,192,631,770 cycles of that radiation which corresponds to the transition between two electron spin energy levels of the ground state of the <sup>133</sup>Cs atom.

Today, the ] in coordination with the ] can be used to synchronize timekeeping systems across the globe.
<br clear=right>

{{As of| 2006}}, the smallest unit of time that has been directly measured is on the ] (10<sup>−18</sup> s) time scale, or around 10<sup>26</sup> Planck times.<ref name="bbcnews_2004">{{cite web |url=http://news.bbc.co.uk/2/hi/science/nature/3486160.stm |title=Shortest time interval measured |publisher=] |date=2004-02-25}}
</ref><ref name="bbcnews_2006">
{{cite web |url=http://news.bbc.co.uk/1/hi/sci/tech/4766842.stm |title=Fastest view of molecular motion |publisher=] |date=2006-03-04}}
</ref><ref>
{{cite web |url=http://www.newscientist.com/article/dn7700 |title=New Scientist article |accessdate=2008-11-27}}
</ref>
== Definitions and standards ==
<!-- BEGIN common units of time table -->
{| class=wikitable align=right style="float:right; margin: 0.5em 0 0.5em 1em; font-size:90%"
|+ Common units of time
|-
! Unit !! Size!!Notes
|-
| ] || 1/10<sup>18</sup> s || smallest measured time
|-
| ] || 1/10<sup>9</sup> s||
|-
| ] || 1/10<sup>6</sup> s||
|-
| ] || 0.001 s||
|-
| ] || ] base unit||
|-
| ] || 60 s||
|-
| ] || 60 minutes||
|-
| ] || 24 hours||
|-
| ] || 7 days|| Also called sennight
|-
| ] || 14 days || 2 weeks
|-
| ] || 28 to 31 days||
|-
| ] || 3 months||
|-
| ] || 12 months||
|-
| common ] || 365 days || 52 weeks + 1 day
|-
| ] || 366 days||52 weeks + 2 days
|-
| ] || 365.24219 days||average
|-
| ] || 365.2425 days||average
|-
| ] || 4 year cycle ||
|-
| ] || 5 years||
|-
| ] || 10 years||
|-
| ] || 15 year cycle ||
|-
| ] || 20 years||
|-
| ] || 17 - 25 years ||approximate
|-
| ] || 50 years ||
|-
| ] || 100 years||
|-
| ] || 1,000 years||
|}
<!-- END common units of time table -->
{{seealso|Time standard|Orders of magnitude (time)}}

The ] for time is the ] ]. From the second, larger units such as the ], ] and ] are defined, though they are "non-SI" units because they do not use the decimal system, and also because of the occasional need for a ]. They are, however, officially accepted for use ''with'' the International System. There are no fixed ratios between seconds and ]s or ]s as months and years have significant variations in length.<ref name="si_units">{{cite book | title = The International System of Units (SI), 7th Edition | url = http://www1.bipm.org/utils/en/pdf/si-brochure.pdf | format = PDF | year = 1998 | author = Organisation Intergouvernementale de la Convention du Métre | accessdate = 2006-06-13}}</ref>

The official SI definition of the second is as follows:<ref name="si_units">{{cite book | title = The International System of Units (SI), 7th Edition | url = http://www1.bipm.org/utils/en/pdf/si-brochure.pdf | format = PDF | year = 1998 | author = Organisation Intergouvernementale de la Convention du Métre | accessdate = 2006-06-13}}</ref><ref name="second">{{cite web | title = Base unit definitions: Second | url = http://physics.nist.gov/cuu/Units/second.html | publisher = ] | accessdate = 2008-01-09}}</ref>
{{Bquote|The second is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the ] 133 atom.}}
<br clear=left>

At its 1997 meeting, the CIPM affirmed that this definition refers to a caesium atom in its ground state at a temperature of 0 K.<ref name="si_units"/>
Previous to 1967, the second was defined as:
{{Bquote|the fraction 1/31,556,925.9747 of the ] for 1900 January 0 at 12 hours ].}}
<br clear=left>

The current definition of the second, coupled with the current definition of the ], is based on the ], which affirms our ] to be a ].

===World time===
The measurement of time is so critical to the functioning of modern societies that it is coordinated at an international level. The basis for scientific time is a continuous count of seconds based on ]s around the world, known as the ]. This is the yardstick for other time scales, including ], which is the basis for civil time.

Earth is split up into a number of ]s. Most time zones are exactly one hour apart, and by convention compute their local time as an offset from UTC or ]. In many locations these offsets vary twice yearly due to ] transitions.

===Sidereal time===
] is the measurement of time relative to a distant star (instead of solar time that is relative to the sun). It is used in astronomy to predict when a star will be overhead. Due to the rotation of the earth around the sun a sidereal day is 1/366 (4 minutes) less than a solar day.

===Chronology===
{{main|Chronology}}
Another form of time measurement consists of studying the ]. Events in the past can be ordered in a sequence (creating a ]), and be put into chronological groups (]). One of the most important systems of periodization is ], which is a system of periodizing the events that shaped the ] and its life. Chronology, periodization, and interpretation of the past are together known as the study of ].

==Religion and mythology==
{{see|:Category:Time and fate deities}}
In the ] book ], traditionally ascribed to ] (970–928 BC), time (as the Hebrew word עדן, זמן ''`iddan(time) zĕman(season)'' is often translated) was traditionally regarded as a medium for the passage of ] events. (Another word, זמן ''zman'', was current as meaning ''time fit for an event'', and is used as the modern ] equivalent to the English word "time".)
] shown ] ]]

<blockquote>
There is an appointed time (''zman'') for everything. And there is a time (’êth) for every event under heaven–<br />
A time (''’êth'') to give birth, and a time to die; A time to plant, and a time to uproot what is planted.<br />
A time to kill, and a time to heal; A time to tear down, and a time to build up.<br />
A time to weep, and a time to laugh; A time to mourn, and a time to dance.<br />
A time to throw stones, and a time to gather stones; A time to embrace, and a time to shun embracing.<br />
A time to search, and a time to give up as lost; A time to keep, and a time to throw away.<br />
A time to tear apart, and a time to sew together; A time to be silent, and a time to speak.<br />
A time to love, and a time to hate; A time for war, and a time for peace.

– {{bibleverse||Ecclesiastes|3:1–8|}}
</blockquote>

===Linear and cyclical time===
{{seealso|Time Cycles|Wheel of time}}
In general, the ] concept, based on the ], is that time is linear, with a beginning, the act of ] by ]. The ] view assumes also an end, the eschaton, expected to happen when ] returns to earth in the ] to judge the living and the dead. This will be the consummation of the world and time (and is, ironically, not a Bible based belief; compare Ecclesiastes 1:4, Psalm 104:5). ]'s '']'' was the first developed application of this concept to world history. The Christian view is that God is uncreated and eternal so that He and the supernatural world are outside time and exist in ].

Ancient cultures such as ], ], ], and other Native American Tribes, plus the ], ], ], ], ], and others have a concept of a ], that regards time as ] and ] consisting of repeating ages that happen to every being of the Universe between birth and extinction.
<br clear=both />

==Philosophy==
{{main|Philosophy of space and time|Temporal finitism}}

The earliest recorded ] of time was expounded by the ]ian thinker ] (c. 2650–2600 BC), who said: "Do not lessen the time of following desire, for the wasting of time is an abomination to the spirit."{{Fact|date=May 2008}} The '']'', the earliest texts on ] and ] dating back to the late ], describe ancient ], in which the ] goes through repeated cycles of creation, destruction and rebirth, with each cycle lasting 4,320,000 years. ] ], including ] and ], wrote essays on the nature of time.<ref>Dagobert Runes, ''Dictionary of Philosophy'', p. 318</ref>

In Book 11 of ] '']'', he ruminates on the nature of time, asking, "What then is time? If no one asks me, I know: if I wish to explain it to one that asketh, I know not." He settles on time being defined more by what it is not than what it is.<ref>St. Augustine, ''Confessions'', Book 11. http://ccat.sas.upenn.edu/jod/augustine/Pusey/book11 (Accessed 5/26/07).</ref>

In contrast to ancient Greek philosophers who believed that the universe had an infinite past with no beginning, ] and ] developed the concept of the universe having a finite past with a beginning. This view was inspired by the ] shared by the three ]: ], ] and ]. The ], ], presented the first such argument against the ancient Greek notion of an infinite past. However, the most sophisticated medieval arguments against an infinite past were developed by the ], ] (Alkindus); the ], ] (Saadia ben Joseph); and the ], ] (Algazel). They developed two logical arguments against an infinite past, the first being the "argument from the impossibility of the existence of an actual infinite", which states:<ref name=Craig>{{citation|title=Whitrow and Popper on the Impossibility of an Infinite Past|first=William Lane|last=Craig|authorlink = William Lane Craig|journal=The British Journal for the Philosophy of Science|volume=30|issue=2|date=June 1979|pages=165-170 }}</ref>

:"An actual infinite cannot exist."
:"An infinite temporal regress of events is an actual infinite."
:"{{Unicode|∴}} An infinite temporal regress of events cannot exist."

The second argument, the "argument from the impossibility of completing an actual infinite by successive addition", states:<ref name=Craig/>

:"An actual infinite cannot be completed by successive addition."
:"The temporal series of past events has been completed by successive addition."
:"{{Unicode|∴}} The temporal series of past events cannot be an actual infinite."

Both arguments were adopted by later Christian philosophers and theologians, and the second argument in particular became more famous after it was adopted by ] in his thesis of the first antimony concerning time.<ref name=Craig/>

] believed time and ] form a container for events, which is as real as the ]s it contains.
{{quotation|Absolute, true, and mathematical time, in and of itself and of its own nature, without reference to anything external, flows uniformly and by another name is called duration. Relative, apparent, and common time is any sensible and external measure (precise or imprecise) of duration by means of motion; such a measure – for example, an hour, a day, a month, a year – is commonly used instead of true time.|''Principia''<ref name="newton">{{cite book | last = Newton | first = Isaac | authorlink = Isaac Newton | title = The Principia, 3rd edition | year = 1726}} Translated by I. Bernard Cohen and Anne Whitman, University of California Press, Berkeley, 1999.</ref>}}

In contrast to Newton's belief in absolute space, and a precursor to Kantian time, ] believed that time and space are relational.<ref>Gottfried Martin, ''Kant's Metaphysics and Theory of Science''</ref> The differences between Leibniz's and Newton's interpretations came to a head in the famous ]. Leibniz thought of time as a fundamental part of an ] conceptual framework, together with ] and ], within which we sequence events, ] their duration, and compare the motions of objects. In this view, ''time'' does not refer to any kind of entity that "flows," that objects "move through," or that is a "container" for events.

], in the '']'', described time as an '']'' intuition that allows us (together with the other ''a priori'' intuition, ]) to comprehend sense experience.<ref name="kant"> {{cite book | last = Kant | first = Immanuel | authorlink = Immanuel Kant | title = The Critique of Pure Reason, 2nd edition | year = 1787}} translated by J. M. D. Meiklejohn, eBooks@Adelaide, 2004—http://ebooks.adelaide.edu.au/k/kant/immanuel/k16p/k16p15.html</ref> With Kant, neither space nor time are conceived as ]s, but rather both are elements of a systematic mental ] that necessarily structures the experiences of any rational agent, or observing subject. Spatial ]s are used to ] how far apart ]s are, and temporal measurements are used to quantify how far apart ]s occur.

In ], time is considered fundamental to the question of ],{{Fact|date=September 2007}} in particular by the philosopher ].{{Fact|date=September 2007}} (See ]).

] believed that time was neither a real homogeneous medium nor a mental construct, but possesses what he referred to as ''Duration''. Duration, in Bergson's view, was creativity and memory as an essential component of reality.<ref>Bergson, Henri (1907) ''Creative Evolution''. trans. by Arthur Mitchell. Mineola: Dover, 1998.</ref>

===Time as "unreal"===
In 5th century BC ], ] the ], in a fragment preserved from his chief work ''On Truth'' held that: ''"Time is not a reality (hypostasis), but a concept (noêma) or a measure (metron)."''
] went further, maintaining that time, motion, and change were illusions, leading to the ] of his follower ].<ref>{{cite web|author=Harry Foundalis|title=You are about to disappear|url=http://www.foundalis.com/phi/WhyTimeFlows.htm|accessdate=2007-04-27}}</ref>
Time as illusion is also a common theme in ] thought,<ref>{{cite web|title=Buddhism and the illusion of time|url=http://www.buddhistinformation.com/buddhism_and_the_illusion_of_time.htm|accessdate=2007-04-27|author=Tom Huston}}</ref> and some modern philosophers have carried on with this theme. ]'s 1908 '']'', for example, argues that time is unreal (see also ]).

However, these arguments often center around what it means for something to be "real". Modern physicists generally consider time to be as "real" as space, though others such as ] in his '']'' argue that quantum equations of the universe take their true form when expressed in the timeless ]realm containing every possible "Now" or momentary configuration of the universe, which he terms 'platonia'.<ref>{{cite web|title=Time is an illusion?|url=http://physicsandphysicists.blogspot.com/2007/03/time-is-illusion.html|accessdate=2007-04-27}}</ref> (See also: ].)

==Physical definition==
{{main|Time in physics}}
From the age of ] up until ] profound reinterpretation of the physical concepts associated with time and space, time was considered to be "absolute" and to flow "equably" (to use the words of Newton) for all observers.<ref>Herman M. Schwartz, ''Introduction to Special Relativity'', McGraw-Hill Book Company, 1968, hardcover 442 pages, see ISBN 0882754785 (1977 edition), pp. 10-13</ref> The science of classical mechanics is based on this Newtonian idea of time.

Einstein, in his ],<ref>A. Einstein, H. A. Lorentz, H. Weyl, H. Minkowski, ''The Principle of Relativity'', Dover Publications, Inc, 2000, softcover 216 pages, ISBN 0486600815, See pp. 37-65 for an English translation of Einstein's original 1905 paper.</ref> postulated the constancy and finiteness of the speed of light for all observers. He showed that this postulate, together with a reasonable definition for what it means for two events to be simultaneous, requires that distances appear compressed and time intervals appear lengthened for events associated with objects in motion relative to an inertial observer.

] showed that if time and space is measured using electromagnetic phenomena (like light bouncing between mirrors) then due to the constancy of the speed of light, time and space become mathematically entangled together in a certain way (called ] ]) which in turn results in ] and in entanglement of all other important derivative physical quantities (like energy, momentum, mass, force, etc) in a certain 4-vectorial way (see ] for more details).
{{Classical mechanics|cTopic=Fundamental concepts}}

===Classical mechanics===
In ] Newton's concept of "relative, apparent, and common time" can be used in the formulation of a prescription for the synchronization of clocks. Events seen by two different observers in motion relative to each other produce a mathematical concept of time that works pretty well for describing the everyday phenomena of most people's experience.

===Modern physics===
In the late nineteenth century, physicists encountered problems with the classical understanding of time, in connection with the behavior of electricity and magnetism. Einstein resolved these problems by invoking a method of synchronizing clocks using the constant, finite speed of light as the maximum signal velocity. This led directly to the result that time appears to elapse at different rates relative to different observers in motion relative to one another.
{{clear}}
]. The past and future ]s are absolute, the "present" is a relative concept different for observers in relative motion.]]

===Spacetime===
{{main|Spacetime}}
Modern ] views the curvature of ] around an object as much a feature of that object as are its ] and ].{{Fact|date=February 2008}}

Time has historically been closely related with ], the two together comprising ] in ] ] and ]. According to these theories, the concept of time depends on the ], and the human perception as well as the measurement by instruments such as clocks are different for observers in relative motion. Even the temporal order of events can change, but the past and future are defined by the backward and forward ]s, which never change.{{Fact|date=February 2008}} The ] is the set of events that can send light signals to the observer, the ] the events to which the observer can send light signals. All else is non-observable and within that set of events the very time-order differs for different observers.{{Fact|date=February 2008}}

===Time dilation===
]: Event B is simultaneous with A in the green reference frame, but it occurred
before in the blue frame, and will occur later in the red frame.]]
{{main|Time dilation}}
"Time is nature's way of keeping everything from happening at once". This quote, attributed variously to ], ], and ], says that time is what separates ]. Einstein showed that people travelling at different speeds, whilst agreeing on cause and effect, will measure different time separations between events and can even observe different chronological orderings between non-causally related events. Though these effects are minute unless one is travelling at a speed close to that of light, the effect becomes pronounced for objects moving at speeds approaching the speed of light. Many ]s exist for only a fixed fraction of a second in a lab relatively at rest, but some that travel close to the speed of light can be measured to travel further and survive much longer than expected (a ] is one example). According to the ], in the high-speed particle's ], it exists, on the average, for a standard amount of time known as its ], and the distance it travels in that time is zero, because its velocity is zero. Relative to a frame of reference at rest, time seems to "slow down" for the particle. Relative to the high-speed particle, distances seems to shorten. Even in Newtonian terms time may be considered the fourth dimension of motion; but Einstein showed how both temporal and spatial dimensions can be altered (or "warped") by high-speed motion.

Einstein (''The Meaning of Relativity''): "Two ]s taking place at the points A and B of a system K are simultaneous if they appear at the same instant when observed from the middle point, M, of the interval AB. Time is then defined as the ensemble of the indications of similar clocks, at rest relatively to K, which register the same simultaneously."

Einstein wrote in his book, ''Relativity'', that ], i.e., two events that appear simultaneous to an observer in a particular inertial reference frame need not be judged as simultaneous by a second observer in a different inertial frame of reference.

===Relativistic time versus Newtonian time===

] of a rapidly accelerating observer in a Newtonian universe. The events ("dots") that pass the horizontal line are the events current to the observer.]]

] of a rapidly accelerating observer in a relativistic universe. The events ("dots") that pass the two diagonal lines in the bottom half of the image (the past ] of the observer in the origin) are the events visible to the observer.]]

The animations on the left and the right visualise the different treatments of time in the Newtonian and the relativistic descriptions. At heart of these differences are the ] and ]s applicable in the Newtonian and relativistic theories, respectively.

In both figures, the vertical direction indicates time. The horizontal direction indicates distance (only one spatial dimension is taken into account), and the thick dashed curve is the ] trajectory ("]") of the observer. The small dots indicate specific (past and future) events in spacetime.

The slope of the world line (deviation from being vertical) gives the relative velocity to the observer. Note how in both pictures the view of spacetime changes when the observer accelerates.

In the Newtonian description these changes are such that ''time'' is absolute: the movements of the observer do not influence whether an event occurs in the 'now' (i.e. whether an event passes the horizontal line through the observer).

However, in the relativistic description the ''observability of events'' is absolute: the movements of the observer do not influence whether an event passes the "]" of the observer. Notice that with the change from a Newtonian to a relativistic description, the concept of ''absolute time'' is no longer applicable: events move up-and-down in the figure depending on the acceleration of the observer.

===Arrow of time===
{{main|Arrow of time}}
Time appears to have a direction – the past lies behind, fixed and incommutable, while the future lies ahead and is not necessarily fixed. Yet the majority of the laws of physics don't provide this ]. The exceptions include the ], which states that ] must increase over time (see ]); the ] arrow of time, which points away from the ], and the radiative arrow of time, caused by ] only traveling forwards in time. In ], there is also the weak arrow of time, from ], and also ] in ] (see ]).

===Quantised time===
{{seealso|Chronon}}
Time quantization is a hypothetical concept. In the modern established physical theories (the ] of Particles and Interactions and ]) time is not quantized.

] (~ ] seconds) is the unit of time in the system of ] known as ]. Current established physical theories are believed to fail at this time scale, and many physicists expect that the Planck time might be the smallest unit of time that could ever be measured, even in principle. Tentative physical theories that describe this time scale exist; see for instance ].

==Time and the Big Bang==
] in particular has addressed a connection between time and the ]. In '']'' and elsewhere, Hawking says that even if time did not begin with the Big Bang and there were another time frame before the Big Bang, no information from events then would be accessible to us, and nothing that happened then would have any effect upon the present time-frame.<ref name=BOT-lecture-B>{{cite web
|url=http://www.hawking.org.uk/lectures/bot.html
|title=The Beginning of Time
|publisher=University of Cambridge
|first=Stephen
|last=Hawking
|quote=Since events before the Big Bang have no observational consequences, one may as well cut them out of the theory, and say that time began at the Big Bang. Events before the Big Bang, are simply not defined, because there's no way one could measure what happened at them. This kind of beginning to the universe, and of time itself, is very different to the beginnings that had been considered earlier.
|accessdate=2008-01-10
}}</ref> Upon occasion, Hawking has stated that time actually began with the Big Bang, and that questions about what happened ''before'' the Big Bang are ''meaningless''.<ref name=BOT-lecture>{{cite web
|url=http://www.hawking.org.uk/lectures/bot.html
|title=The Beginning of Time
|publisher=University of Cambridge
|first=Stephen
|last=Hawking
|quote=The conclusion of this lecture is that the universe has not existed forever. Rather, the universe, and time itself, had a beginning in the Big Bang, about 15 billion years ago.
|accessdate=2008-01-10
}}</ref><ref>{{cite web
|url=http://www.admin.ox.ac.uk/po/news/2005-06/feb/27.shtml
|title=Professor Stephen Hawking lectures on the origin of the universe
|first=Stephen
|last=Hawking
|date=2006-02-27
|publisher=University of Oxford
|quote=Suppose the beginning of the universe was like the South Pole of the earth, with degrees of latitude playing the role of time. The universe would start as a point at the South Pole. As one moves north, the circles of constant latitude, representing the size of the universe, would expand. To ask what happened before the beginning of the universe would become a meaningless question because there is nothing south of the South Pole.'
|accessdate=2008-01-10
}}</ref><ref>{{cite web
|url=http://www.ghandchi.com/312-SpaceEng.htm
|title=Space and New Thinking
|first=Sam : Editor/Publisher
|last=Ghandchi
|date=2004-01-16
|quote=and as Stephen Hawking puts it, asking what was before Big Bang is like asking what is North of North Pole, a meaningless question.
|accessdate=2008-01-10
}}</ref> This less-nuanced, but commonly repeated formulation has received criticisms from philosophers such as ] philosopher ].<ref>{{cite web
|url=http://radicalacademy.com/adlertheology1.htm
|title=Natural Theology, Chance, and God
|first=Mortimer J., Ph.D.
|last=Adler
|quote=Hawking could have avoided the error of supposing that time had a beginning with the Big Bang if he had distinguished time as it is measured by physicists from time that is not measurable by physicists.... an error shared by many other great physicists in the twentieth century, the error of saying that what cannot be measured by physicists does not exist in reality.
|accessdate=2008-01-10
}} {{cite encyclopedia
|title=The Great Ideas Today
|encyclopedia=Encyclopaedia Britannica
|year=1992
}}</ref><ref>
{{cite web
|url=http://radicalacademy.com/adlertheology2.htm
|title=Natural Theology, Chance, and God
|first=Mortimer J., Ph.D.
|last=Adler
|quote=Where Einstein had said that what is not measurable by physicists is of no interest to them, Hawking flatly asserts that what is not measurable by physicists does not exist — has no reality whatsoever.<br>With respect to time, that amounts to the denial of psychological time which is not measurable by physicists, and also to everlasting time — time before the Big Bang — which physics cannot measure. Hawking does not know that both Aquinas and Kant had shown that we cannot rationally establish that time is either finite or infinite.
|accessdate=2008-01-10
}} {{cite encyclopedia
|title=The Great Ideas Today
|encyclopedia=Encyclopaedia Britannica
|year=1992
}}
</ref>

Scientists have come to some agreement on descriptions of events that happened 10<sup>−35</sup> seconds after the Big Bang, but generally agree that descriptions about what happened before one ] (5 × 10<sup>−44</sup> seconds) after the Big Bang will likely remain pure speculation.

===Speculative physics beyond the Big Bang===
<!-- article is about TIME, not about the Big Bang. This section needs to go to ] article -->
] seen on the left. Image from ] press release, 2006.]]

While the Big Bang model is well established in cosmology, it is likely to be refined in the future. Little is known about the earliest moments of the universe's history. The ] require the existence of a singularity at the beginning of cosmic time. However, these theorems assume that ] is correct, but general relativity must break down before the universe reaches the ], and a correct treatment of ] may avoid the singularity.<ref>{{cite book | author=Hawking, Stephen; and Ellis, G. F. R. | title = The Large Scale Structure of Space-Time | location= Cambridge | publisher=Cambridge University Press | year=1973 |id = ISBN 0-521-09906-4}}</ref>

There may also be parts of the universe well beyond what can be observed in principle. If inflation occurred this is likely, for exponential expansion would push large regions of space beyond our observable horizon.

Some proposals, each of which entails untested hypotheses, are:
* models including the ] in which the whole of space-time is finite; the Big Bang does represent the limit of time, but without the need for a singularity.<ref>{{cite journal | author=] and ] | title=Wave function of the universe | journal=Phys. Rev. D | volume=28 | pages=2960 | year=1983 | doi=10.1103/PhysRevD.28.2960}}</ref>
* ] models<ref>{{cite journal | author=Langlois, David | title=Brane cosmology: an introduction | year=2002 | id={{arxiv|archive=hep-th|id=0209261}} }}</ref> in which inflation is due to the movement of branes in ]; the pre-big bang model; the ] model, in which the Big Bang is the result of a collision between branes; and the ], a variant of the ekpyrotic model in which collisions occur periodically.<ref>{{cite journal | last=Linde | first=Andre | year=2002 | title=Inflationary Theory versus Ekpyrotic/Cyclic Scenario | id={{arxiv|archive=hep-th|id=0205259}} }}</ref><ref name="rebirth">{{cite news | url=http://www.space.com/scienceastronomy/060508_mm_cyclic_universe.html | title=Recycled Universe: Theory Could Solve Cosmic Mystery | publisher=] | date=] ] | accessdate=2007-07-03}}</ref><ref name="rebirth2">{{cite web | url=http://www.science.psu.edu/alert/Bojowald6-2007.htm | title=What Happened Before the Big Bang? | accessdate=2007-07-03}}</ref>
* ], in which inflation events start here and there in a random quantum-gravity foam, each leading to a ''bubble universe'' expanding from its own big bang.<ref>{{cite journal | author = A. Linde |title = Eternal chaotic inflation | journal = Mod. Phys. Lett. |volume = A1 |year =1986 | pages=81}}<br />{{cite journal | author = A. Linde |title = Eternally existing self-reproducing chaotic inflationary universe | journal = Phys. Lett. |volume = B175 |year =1986|pages=395&ndash;400}}</ref>

Proposals in the last two categories see the Big Bang as an event in a much larger and older universe, or ], and not the literal beginning.

==Time travel==
{{main|Time travel}}
{{seealso|Time travel in fiction|Grandfather paradox}}

Time travel is the concept of moving backwards and/or forwards to different points in time, in a manner analogous to moving through ] and different than the "normal" flow of time to an earthbound observer. Although time travel has been a ] in ] since the 19th century, and one-way travel into the future is arguably possible given the phenomenon of ] in the ], it is currently unknown whether the ] would allow time travel to the past. Any technological device, whether fictional or hypothetical, that is used to achieve time travel is known as a ].
A central problem with time travel to the past is the violation of ]; should an effect precede its cause, it would give rise to the possibility of ]. Some interpretations of time travel resolve this by accepting the possibility of travel between ] or ]s.

Theory would point toward there having to be a physical ] in which one could travel to, where the ] (i.e. the point that which you are leaving) would be present at a point fixed in either the past or future. Seeing as this theory would be dependent upon the theory of a ], it is uncertain how or if it would be possible to just prove the possibility of time travel.

==Perception of time==
===Psychology===
{{see also|Mental chronometry|Sense of time}}
Even in the presence of timepieces, different individuals may judge an identical length of time to be passing at different rates.{{Fact|date=February 2008}} Commonly, this is referred to as time seeming to "fly" (a period of time seeming to pass faster than possible) or time seeming to "drag" (a period of time seeming to pass slower than possible). The psychologist ] called this form of time perception "lived time."{{Fact|date=February 2008}}

This common experience was used to familiarize the general public to the ideas presented by ]'s theory of relativity in a 1930 cartoon by ]:<ref name=Priestley">{{cite book | last = Priestley | first = J. B. | authorlink = J. B. Priestley | title = Man and Time | publisher = Crescent Books | location = New York | year = 1964 | pages = 96 | doi = | isbn = }}</ref><ref name="Sunrise">{{cite web | last = Sunrise | first = | title = Unified Field Theory: A new interpretation | work = Chapter 2—The Development of the Unified Field Theory, pg. 31 | publisher = Sunrise Information Services | year = 2008 | url = http://www.sunrisepage.com/uft/history.pdf| format =PDF | doi = | accessdate = }}</ref>

{{quotation|'''Man:''' Well, it's like this,—supposing I were to sit next to a pretty girl for half an hour it would seem like half a minute,—<br>'''Einstein:''' Braffo! You haf zee ideah! ]'']<br>'''Man:''' But if I were to sit on a hot stove for two seconds then it would seem like two hours.}}

A form of temporal illusion verifiable by experiment is the ],<ref name="Wada">Wada Y, Masuda T, Noguchi K, 2005, "Temporal illusion called 'kappa effect' in event perception" Perception 34 ECVP Abstract Supplement</ref> whereby time intervals between visual events are perceived as relatively longer or shorter depending on the relative spatial positions of the events. In other words: the perception of temporal intervals appears to be directly affected, in these cases, by the perception of spatial intervals.

Time also appears to pass more quickly as one gets older.{{Fact|date=July 2008}} ] suggests that the perception of time is a ratio: ''Unit of Time : Time Lived''.{{Fact|date=February 2008}} For example, one hour to a six-month-old person would be approximately "1:4368", while one hour to a 40-year-old would be "1:349,440". Therefore an hour appears much longer to a young child than to an aged adult, even though the measure of time is the same.

===Altered states of consciousness===
Altered states of consciousness are sometimes characterized by a different estimation of time. Some psychoactive substances – such as ]s – may also dramatically alter a person's temporal judgement. When viewed under the influence of such substances as ], ], and ], a clock may appear to be a strange reference point and a useless tool for measuring the passage of events as it does not correlate with the user's experience. At higher doses, time may appear to slow down, stop, speed up, go backwards and even seem out of sequence. A typical thought might be "I can't believe it's only 8 o'clock, but then again, what does 8 o'clock mean?" As the boundaries for experiencing time are removed, so is its relevance. Many users claim this unbounded timelessness feels like a glimpse into spiritual infinity. To imagine that one exists somewhere "outside" of time is one of the hallmark experiences of a psychedelic voyage.{{Fact|date=February 2008}} ], a milder psychedelic, may also distort the perception of time to a lesser degree.<ref>{{cite web |url=http://www.erowid.org/plants/cannabis/cannabis_effects.shtml |title=Cannabis Effects |accessdate=2008-02-15 |work=Erowid |quote=Time sense altered: cars seem like they are moving too fast, time dilation and compression are common at higher doses.}}</ref>

The practice of ], central to all Buddhist traditions, takes as its goal the reflection of the mind back upon itself, thus altering the subjective experience of time; the so called, 'entering the now', or 'the moment'.{{Fact|date=February 2008}}

===Culture===
Culture is another variable contributing to the perception of time. Anthropologist ] reported after studying the ] cultures that: "… the Hopi language is seen to contain no words, grammatical forms, construction or expressions or that refer directly to what we call “time”, or to past, present, or future…"<ref>Carroll, John B. (ed.)(1956). ''Language Thought and Reality. Selected Writings of Benjamin Lee Whorf''. MIT Press, Boston, Massachusetts. ISBN 0262730065 9780262730068</ref>

An interesting fact is that in ] (official language of ]), there is only one word ''kal'' for both ''yesterday'' and ''tomorrow''. The Hindi word ''kal'' could mean ''yesterday'' or it could mean ''tomorrow'', depending on the context.

==Use of time==
{{see also|Time management|Time discipline}}
In ] and ], ] is the general name given to ] and ] rules, conventions, customs, and expectations governing the measurement of time, the social currency and awareness of time measurements, and people's expectations concerning the observance of these customs by others.

The use of time is an important issue in understanding ], ], and ]. ] is a developing field of study. The question concerns how time is allocated across a number of activities (such as time spent at home, at work, shopping, etc.). Time use changes with ], as the ] or the ] created new opportunities to use time in different ways. However, some aspects of time use are relatively stable over long periods of time, such as the amount of time spent traveling to work, which despite major changes in ], has been observed to be about 20-30 minutes one-way for a large number of cities over a long period of time. This has led to the disputed ].

] is the organization of tasks or events by first estimating how much time a task will take to be completed, when it must be completed, and then adjusting events that would interfere with its completion so that completion is reached in the appropriate amount of time. Calendars and day planners are common examples of time management tools.

] and ] have written on the use of time from a sociological perspective.

==See also==
]]]
{{portal|Time|MontreGousset001.jpg}}
:''See the Time ] below for an exhaustive list of related articles.''

===Books===
* '']''
* '']''
* '']''

===Organizations===
''Leading scholarly organizations for researchers on the history and technology of time and timekeeping''
* ] - AHS (United Kingdom)
* ] - AFAHA (France)
* ] (Switzerland)
* ] - DGC (Germany)
* ] Associazione Italiana Cultori di Orologeria Antica (Italy)
* ] - NAWCC (United States of America)

{{col-begin}}
{{col-break|width=25%}}
===Miscellaneous arts and sciences===
* ]
* ]
* ]
* ]
* ] (NTP)
* ]
* ]
* ]

{{col-break|width=25%}}
===Miscellaneous units of time===
* ]
* ]
* ]
* ]
* ]
* ]
{{col-end}}

==Notes and references==
{{Refimprove|date=July 2008}}
{{reflist|2}}

==Further reading==
* {{cite book | authorlink = Julian Barbour | last = Barbour | first = Julian | title = The End of Time: The Next Revolution in Physics | Publisher = Oxford University Press | year = 1999 | id = ISBN 0-19-514592-5 |}}
* {{cite book | last = Das | first = Tushar Kanti | title = The Time Dimension: An Interdisciplinary Guide | year = 1990 | location = New York | publisher = Praeger | id=ISBN 0275926818 }}- Research bibliography
* {{cite book | authorlink = Paul Davies | last = Davies | first = Paul | title=About Time: Einstein's Unfinished Revolution | year = 1996|id=ISBN 0-684-81822-1}}
* {{cite book | authorlink = Richard Feynman | last = Feynman | first = Richard | title=The Character of Physical Law | year = 1994|origyear=1965|location=Cambridge (Mass)|publisher=The MIT Press|id=ISBN 0-262-56003-8|pages=108-126|url=http://mitpress.mit.edu/catalog/item/default.asp?ttype=2&tid=5277}}
* {{cite book | authorlink = Peter Galison | last = Galison | first = Peter | title=Einstein's Clocks and Poincaré's Maps: Empires of Time | year = 1992|location=New York|publisher=W. W. Norton|id= ISBN 0-393-02001-0}}
* {{cite book | last = Highfield | first = Roger | title = Arrow of Time: A Voyage through Science to Solve Time's Greatest Mystery | publisher = Random House | year = 1992 | id = ISBN 0-449-90723-6}}
* {{cite book | authorlink=Mermin|last = Mermin | first = N. David | title=It's About Time: Understanding Einstein's Relativity| year = 2005|publisher=Princeton University Press|id=ISBN 0-691-12201-6|url=http://press.princeton.edu/titles/8112.html}}
* {{cite book | authorlink = Roger Penrose | last = Penrose | first = Roger | title=The Emperor's New Mind: Concerning Computers, Minds, and the Laws of Physics | year = 1999|origyear=1989|location=New York|publisher=Oxford University Press|id=ISBN 0-19-286198-0|pages=391-417|url=http://www.oup.com/uk/catalogue/?ci=9780192861986}}
* {{cite book | last = Price | first = Huw | title=Time's Arrow and Archimedes' Point| year = 1996|publisher=Oxford University Press|id=ISBN 0-19-511798-0|url=http://www.usyd.edu.au/time/price/TAAP.html}}
* {{cite book | authorlink = Hans Reichenbach | last = Reichenbach | first = Hans | title=The Direction of Time | year = 1999|origyear=1956|location=New York|publisher=Dover|id=ISBN
0-486-40926-0|url=http://store.doverpublications.com/0486409260.html}}
*], '']''
* {{cite book | authorlink = Gerald James Whitrow | last = Whitrow | first = Gerald J. | title = The Nature of Time | publisher = Holt, Rinehart and Wilson (New York) | year = 1973}}
* {{cite book | last = Whitrow | first = Gerald J. | title = The Natural Philosophy of Time | publisher = Clarendon Press (Oxford) | year = 1980}}
* {{cite book | last = Whitrow | first = Gerald J. | title = Time in History. The evolution of our general awareness of time and temporal perspective | publisher = Oxford University Press | year = 1988 | id = ISBN 0-19-285211-6}}
* {{cite book | last = Rovelli | first = Carlo | title = What is time? What is space? | publisher = Di Renzo Editore |location=Rome | year = 2006|id=ISBN 8883231465|url=http://www.direnzo.it/main.phtml?Language=en&Doc=0001&ISBN=8883231465}}
*], (2005) ''Art, Time and Technology: Histories of the Disappearing Body'', Berg

==External links==
{{external links}}
{{wiktionarypar|time}}
{{Wikiquote}}
{{Wikibooks}}
{{Commonscat}}
===Perception of time===
*

===Physics===
*

===Philosophy===
;'''Eastern Philosophy'''
*
*

;'''Western Philosophy'''
* {{cite web
|url=http://www.onphilosophy.co.uk/time_-_a_dialogue.html
|title=Is there a defensible argument for the non-existence of time?
|first=Will
|last=Crouch
|Copyright James Nicholson
|year=2006-2008
|work=On Philosophy
|accessdate=2008-01-24}}
*{{cite encyclopedia
|url=http://www.iep.utm.edu/t/time.htm
|title=Time
|first=Bradley (California State University, Sacramento)
|last=Dowden
|year=2007
|encyclopedia=The Internet Encyclopedia of Philosophy
|editor=James Fieser, Ph.D., Bradley Dowden, Ph.D.
|accessdate=2008-01-31}}
* {{cite encyclopedia
|url=http://plato.stanford.edu/archives/win2004/entries/time-experience
|title=The Experience and Perception of Time
|last=Le Poidevin
|first=Robin
|year=Winter 2004
|encyclopedia=The Stanford Encyclopedia of Philosophy
|editor=Edward N. Zalta
|accessdate=2008-01-17}}
* {{cite encyclopedia
|url=http://plato.stanford.edu/archives/win2007/entries/leibniz-physics/
|title=Leibniz's Philosophy of Physics
|year=Winter 2007
|copyright=2007
|first=Jeff (Harvard University)
|last=Mcdonough
|encyclopedia=The Stanford Encyclopedia of Philosophy
|editor=Edward N. Zalta
|publisher=Stanford University
|accessdate=2008-01-31}}
* {{cite web
|url=http://www.friesian.com/space.htm#clarke
|title=The Clarke-Leibniz Debate (1715-1716)
|first=Kelley L., Ph.D. (Los Angeles Valley College)
|last=Ross
|publisher=The Proceedings of the Friesian School, Fourth Series (1996, 1999, 2001)
|accessdate=2008-01-17}}
* {{cite web
|url=http://www.friesian.com/space.htm#kant
|title=Three Points in Kant's Theory of Space and Time
|first=Kelley L., Ph.D. (Los Angeles Valley College)
|last=Ross
|publisher=The Proceedings of the Friesian School, Fourth Series (1996, 1999, 2001)
|accessdate=2008-01-17}}
* {{cite encyclopedia
|url=http://plato.stanford.edu/entries/spacetime-bebecome/
|title=Being and Becoming in Modern Physics
|year=Fall 2007
|last=Savitt
|first=Steven, Ph.D. (University of British Columbia)
|encyclopedia=The Stanford Encyclopedia of Philosophy
|editor=Edward N. Zalta
|accessdate=2008-01-17}}
* {{cite encyclopedia
|url=http://plato.stanford.edu/archives/sum2004/entries/kant-leibniz/
|title=Kant and Leibniz
|year=Summer 2004
|first=Catherine (City University of New York)
|last=Wilson
|encyclopedia=The Stanford Encyclopedia of Philosophy
|editor=Edward N. Zalta
|publisher=Stanford University
|issn=1095-5054
|accessdate=2008-01-31}}

===Timekeeping===
*
*
*
*
*

===Miscellaneous===
*
* from Planck Time to the lifespan of the universe

==Navigation templates==<!-- Header linked from "See also" above -->
{{Time Topics}}
{| width="100%" class="collapsible collapsed" style="background:transparent; margin:1em 0 0;"
!style="background:#ee9; border:1px solid silver; padding:0.2em 1em 0.2em 6.5em; <!--to reduce size of "" link:-->font-size:90%;"| {{resize|110%|Time articles: Detailed navigation}}</tr>
|
{{Time measurement and standards}}
{{Chronology}}
{{Time in religion and mythology}}
{{Time in philosophy}}
|}

]
]
]

]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]
]

Revision as of 08:19, 28 November 2008

Time is something you cannot stop

referrence - you cannot stop sams weight gain


time started in 2008

when members of BMJT decides that a source of time was needed to count on.]

Above is a cock clock!


-BMJT