Pikeun ngukurskala waktu anu lumangsung pohara gancang (dina jero dunyaéléktronika sartasemikonduktor), lolobana jelema ngagunakeunhijian mili detik (sapersarébu detik), mikro detik (sapér hiji juta detik), nano detik (nanosecond), piko detik (picosecond), jeung saterusna.
Dina dunyafisika, diménsi waktu jeung diménsi ruang (panjang, lébar, sarta volume) mangrupa diménsi ukuran anu dasar, sajaba ti beurat jeung massa. Gabungan ti waktu, ruang sarta beurat kiwari bisa dipaké pikeun nyaritakeun sarta ngécéskeun rusiah alam sacara kuantitatif (dumasar kana hasil ukur). Contona tanaga (énergi) dinyatakeun dina hijian ukuran kg*(méter/detik)kwadrat atawa anu mindeng dipikawanoh nyaétahijian watt*detik atawajoule.
Inphysics and other sciences,time is considered one of the fewfundamental quantities.[2]Time is used to define other quantities – such asvelocity – and definingtime in terms of such quantities would result incircularity of definition.[3] Anoperational definition 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 thesecond, has a high utility value in the conduct of both advanced experiments and everyday affairs of life. The operational definition léaves aside the question whether there is something called time, apart from the counting activity just mentioned, that flows and that can be méasured. Investigations of a single continuum calledspace-time brings the nature of time into association with related questions into the nature ofspace, questions that have their roots in the works of éarly students ofnatural philosophy.
Among prominent philosophers, there are two distinct viewpoints ontime.One view is that time is part of the fundamental structure of theuniverse, adimension in which events occur insequence.Time travel, in this view, becomes a possibility as other "times" persist like frames of a film strip, spréad out across the time line.Sir Isaac Newton subscribed to thisrealist view, and hence it is sometimes referred to asNewtonian time.[4][5] The opposing view is thattime does not refer to any kind of "container" that events and objects "move through", nor to any entity that "flows", but that it is instéad part of a fundamental intellectual structure (together withspace andnumber) within which humans sequence and compare events. This second view, in the tradition ofGottfried Leibniz[6]andImmanuel Kant,[7][8]holds thattime is neither an event nor a thing, and thus is not itself méasurable nor can it be traveled.
Temporal méasurement has occupied scientists andtechnologists, and was a prime motivation innavigation andastronomy.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 béat of a héart. Currently, the international unit of time, thesecond, is defined in terms of radiation emitted bycaesium atoms (see below).Time is also of significant social importance, having economic value ("time is money") as well as personal value, due to anawareness of the limited time in éach day and inhuman lifespans.
Temporal méasurement, orchronometry, takes two distinct period forms: thecalendar, a mathematical abstraction for calculating extensive periods of time,[9] and theclock, 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.
Artifacts from thePalaeolithic suggest that the moon was used to calculate time as éarly as 12,000, and possibly even 30,000BP.[10]
TheSumerian civilization of approximately 2000 BC introduced thesexagesimal 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 yéar (with a few more days added on).Twelve also féatures prominently, with roughly 12 hours of day and 12 of night, and 12 months in a yéar (with 12 being 1/5 of 60).
A large variety ofdevices have been invented to méasure time. The study of these devices is calledhorology.
AnEgyptian device dating to c.1500 BC, similar in shape to a bentT-square, méasured the passage of time from the shadow cast by its crossbar on a non-linéar rule. The T was oriented éastward in the mornings. Atnoon, the device was turned around so that it could cast its shadow in the evening direction.[11]
Asundial uses agnomon to cast a shadow on a set of markings which were calibrated to thehour. The position of the shadow marked the hour inlocal time.
The most accurate timekeeping devices of the ancient world were thewater clock orclepsydra, one of which was found in the tomb of Egyptian pharaohAmenhotep I (1525–1504 BC). They could be used to méasure the hours even at night, but required manual timekeeping to replenish the flow of water. TheGreeks andChaldeans regularly maintained timekeeping records as an essential part of their astronomical observations.Arab inventors andengineers in particular made improvements on the use of water clocks up to the Middle Ages.[12]
The Arab engineers also invented the first mechanical clocks to be driven byweights andgears in the 11th century.[13][14][15] Also in the 11th century, theChinese inventors andengineers invented the first mechanical clocks to be driven by anescapement mechanism.
Thehourglass uses the flow of sand to méasure the flow of time. They were used in navigation.Ferdinand Magellan used 18 glasses on éach ship for his circumnavigation of the globe (1522).[16]
Incense sticks and candles were, and are, commonly used to méasure 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.Richard of Wallingford (1292–1336), abbot of St. Alban's abbey, famously built a mechanical clock as an astronomicalorrery about 1330.[17][18]
The English wordclock 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 méanbell. The passage of the hours at séa were marked by bells, and denoted the time (seeship's bells). The hours were marked by bells in the abbeys as well as at séa.
A chip-scale atomic clock
Clocks can range fromwatches, to more exotic varieties such as theClock of the Long Now. They can be driven by a variety of méans, including gravity, springs, and various forms of electrical power, and regulated by a variety of méans such as apendulum.
Achronometer is a portable timekeeper that meets certain precision standards. Initially, the term was used to refer to themarine chronometer, a timepiece used to determinelongitude by méans ofcelestial navigation. More recently, the term has also been applied to thechronometer watch, awristwatch that meets precision standards set by the Swiss agencyCOSC.
The most accurate timekeeping devices areatomic clocks, which are accurate to seconds in many millions of yéars,[19] 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 Méasurements bases its unit of time, the second, on the properties ofcaesium atoms.SI 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 the133Cs atom.
TheSI base unit for time is theSIsecond. From the second, larger units such as theminute,hour andday are defined, though they are "non-SI" units because they do not use the decimal system, and also because of the occasional need for aleap-second. They are, however, officially accepted for usewith the International System. There are no fixed ratios between seconds andmonths oryears as months and yéars have significant variations in length.[20]
The official SI definition of the second is as follows:[20][21]
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 thecaesium 133 atom.
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.[20]Previous to 1967, the second was defined as:
The méasurement of time is so critical to the functioning of modérn societies that it is coordinated at an international level. The basis for scientific time is a continuous count of seconds based onatomic clocks around the world, known as theInternational Atomic Time (TAI). This is the yardstick for other time scales, includingCoordinated Universal Time (UTC), which is the basis for civil time.
éarth is split up into a number oftime zones. Most time zones are exactly one hour apart, and by convention compute their local time as an offset from UTC orGreenwich Mean Time. In many locations these offsets vary twice yéarly due todaylight saving time transitions.
Sidereal time is the méasurement of time relative to a distant star (instéad of solar time that is relative to the sun). It is used in astronomy to predict when a star will be overhéad. Due to the rotation of the éarth around the sun a sideréal day is slightly less than a solar day.
Another form of time méasurement consists of studying thepast. Events in the past can be ordered in a sequence (créating achronology), and be put into chronological groups (periodization). One of the most important systems of periodization isgeologic time, which is a system of periodizing the events that shaped theEarth and its life. Chronology, periodization, and interpretation of the past are together known as the study ofhistory.
Allegorical woodcut of Time, who "revealeth all things", guiding his daughter Truth away from the demon of Hypocrisy. John Byddell, 1535.
In theOld Testament bookEcclesiastes, traditionally ascribed toSolomon (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 ofpredestined events. (Another word, זמןzman, was current as meaningtime fit for an event, and is used as the modernHebrew equivalent to the English word "time".)
There is an appointed time (zman) for everything. And there is a time (’êth) for every event under heaven– A time (’êth) to give birth, and a time to die; A time to plant, and a time to uproot what is planted. A time to kill, and a time to heal; A time to tear down, and a time to build up. A time to weep, and a time to laugh; A time to mourn, and a time to dance. A time to throw stones, and a time to gather stones; A time to embrace, and a time to shun embracing. A time to search, and a time to give up as lost; A time to keep, and a time to throw away. A time to tear apart, and a time to sew together; A time to be silent, and a time to speak. A time to love, and a time to hate; A time for war, and a time for peace.
In general, theJudaeo-Christian concept, based on theBible, is that time is linéar, with a beginning, the act ofcreation byGod. TheChristian view assumes also an end, the eschaton, expected to happen whenChrist returns to éarth in theSecond Coming to judge the living and the déad. This will be the consummation of the world and time.St Augustine'sCity of God was the first developed application of this concept to world history. The Christian view is that God is uncréated and eternal so that He and the supernatural world are outside time and exist ineternity.
In Book 11 ofSt. Augustine'sConfessions, 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.[23]
In contrast to ancient Greek philosophers who believed that the universe had an infinite past with no beginning,medieval philosophers andtheologians developed the concept of the universe having a finite past with a beginning. This view was inspired by thecreation myth shared by the threeAbrahamic religions:Judaism,Christianity andIslam. TheChristian philosopher,John Philoponus, 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 theearly Muslim philosopher,Al-Kindi (Alkindus); theJewish philosopher,Saadia Gaon (Saadia ben Joseph); and theMuslim theologian,Al-Ghazali (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:[24]
"An actual infinite cannot exist."
"An infinite temporal regress of events is an actual infinite."
"∴ 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:[24]
"An actual infinite cannot be completed by successive addition."
"The temporal series of past events has been completed by successive addition."
"∴ The temporal series of past events cannot be an actual infinite."
Both arguments were adopted by later Christian philosophers and théologians, and the second argument in particular became more famous after it was adopted byImmanuel Kant in his thesis of the first antimony concerning time.[24]
Isaac Newton believed time andspace form a container for events, which is as réal as theobjects it contains.
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.
In contrast to Newton's belief in absolute space, and a precursor to Kantian time,Leibniz believed that time and space are relational.[26] The differences between Leibniz's and Newton's interpretations came to a héad in the famousLeibniz-Clarke Correspondence. Leibniz thought of time as a fundamental part of anabstract conceptual framework, together withspace andnumber, within which we sequence events,quantify 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.
Immanuel Kant, in theCritique of Pure Reason, described time as ana priori intuition that allows us (together with the othera priori intuition,space) to comprehend sense experience.[27] With Kant, neither space nor time are conceived assubstances, but rather both are elements of a systematic mentalframework that necessarily structures the experiences of any rational agent, or observing subject. Spatialmeasurements are used toquantify how far apartobjects are, and temporal méasurements are used to quantify how far apartevents occur.
Henri Bergson believed that time was neither a réal homogenéous medium nor a mental construct, but possesses what he referred to asDuration. Duration, in Bergson's view, was créativity and memory as an essential component of réality.[28]
In 5th century BCGreece,Antiphon theSophist, in a fragment preserved from his chief workOn Truth held that:"Time is not a reality (hypostasis), but a concept (noêma) or a measure (metron)."Parmenides went further, maintaining that time, motion, and change were illusions, léading to theparadoxes of his followerZeno.[29]Time as illusion is also a common theme inBuddhist thought,[30] and some modérn philosophers have carried on with this theme.J. M. E. McTaggart's 1908The Unreality of Time, for example, argues that time is unréal (see alsoThe flow of time).
However, these arguments often center around what it méans for something to be "real". modérn physicists generally consider time to be as "real" as space, though others such asJulian Barbour in hisThe End of Time argue that quantum equations of the universe take their true form when expressed in the timelessconfiguration spacerealm containing every possible "Now" or momentary configuration of the universe, which he terms 'platonia'.[31] (See also:Eternalism (philosophy of time).)
From the age ofNewton up untilEinstein's 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.[32] The science of classical mechanics is based on this Newtonian idéa of time.
Einstein, in hisspecial theory of relativity,[33] postulated the constancy and finiténess of the speed of light for all observers. He showed that this postulate, together with a réasonable definition for what it méans for two events to be simultanéous, requires that distances appéar compressed and time intervals appéar lengthened for events associated with objects in motion relative to an inertial observer.
Einstein showed that if time and space is méasured 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 (calledMinkowskispace) which in turn results inLorentz transformation and in entanglement of all other important derivative physical quantities (like energy, momentum, mass, force, etc) in a certain 4-vectorial way (seespecial relativity for more details).
Inclassical mechanics 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 éach other produce a mathematical concept of time that works pretty well for describing the everyday phenomena of most péople's experience.
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 appéars to elapse at different rates relative to different observers in motion relative to one another.
Two-dimensional space depicted in three-dimensionalspacetime. The past and futurelight cones are absolute, the "present" is a relative concept different for observers in relative motion.
Time has historically been closely related withspace, the two together comprisingspacetime inEinstein'sspecial relativity andgeneral relativity. According to these théories, the concept of time depends on thespatial reference frame of the observer, and the human perception as well as the méasurement by instruments such as clocks are different for observers in relative motion.[rujukan?] Even the temporal order of events can change, but the past and future are defined by the backward and forwardlight cones, which never change.[rujukan?] Thepast is the set of events that can send light signals to the observer, thefuture 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.[rujukan?]
Relativity of simultaneity: Event B is simultanéous with A in the green reference frame, but it occurred before in the blue frame, and will occur later in the red frame.
"Time is nature's way of keeping everything from happening at once". This quote, attributed variously toEinstein,John Archibald Wheeler, andWoody Allen, says that time is what separatescause and effect. Einstein showed that péople traveling at different speeds, whilst agreeing on cause and effect, will méasure 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 traveling at a speed close to that of light, the effect becomes pronounced for objects moving at speeds approaching the speed of light. Manysubatomic particles 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 méasured to travel further and survive much longer than expected (amuon is one example). According to thespecial theory of relativity, in the high-speed particle'sframe of reference, it exists, on the average, for a standard amount of time known as itsmean lifetime, 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): "Twoevents 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, thatsimultaneity is also relative, i.e., two events that appéar simultanéous to an observer in a particular inertial reference frame need not be judged as simultanéous by a second observer in a different inertial frame of reference.
Views of spacetime along theworld line of a rapidly accelerating observer in a Newtonian universe. The events ("dots") that pass the horizontal line are the events current to the observer.Views of spacetime along theworld line 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 pastlight cone of the observer in the origin) are the events visible to the observer.
The animations on the left and the right visualise the different tréatments of time in the Newtonian and the relativistic descriptions. At héart of these differences are theGalilean andLorentz transformations applicable in the Newtonian and relativistic théories, 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 thespacetime trajectory ("world line") 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 thattime 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 theobservability of events is absolute: the movements of the observer influences whether an event passes the light cone of the observer. Notice that with the change from a Newtonian to a relativistic description, the concept ofabsolute time is no longer applicable: events move up-and-down in the figure depending on the acceleration of the observer.
Time quantization is a hypothetical concept. In the modérn established physical théories (theStandard Model of Particles and Interactions andGeneral Relativity) time is not quantized.
Planck time (~5.4 × 10−44 seconds) is the unit of time in the system ofnatural units known asPlanck units. Current established physical théories 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 méasured, even in principle. Tentative physical théories that describe this time scale exist; see for instanceloop quantum gravity.
Stephen Hawking in particular has addressed a connection between time and theBig Bang. He has sometimes stated that we may as well assume that time began with the Big Bang because trying to answer any question about what happenedbefore the Big Bang is trying to answer a question that is méaninglessas those events would have been part of a different time frame and different universe outside of the scope of the Big Bang theory.[34][35][36]
Aristotelian philosopherMortimer J. Adler,[37][38] has criticized some expositions that Hawking has given stating that time didn't exist before the big bang.
Hawking, inA Brief History of Time and elsewhere, along with several other modérn physicists, has stated his position more cléarly and less controversially: 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.[39]
Scientists have come to some agreement on descriptions of events that happened 10−35 seconds after the Big Bang, but generally agree that descriptions about what happened before onePlanck time (5 × 10−44 seconds) after the Big Bang will likely remain pure speculation.
A graphical representation of the expansion of the universe with the inflationary epoch represented as the dramatic expansion of themetric seen on the left. Image fromNASA, 2006.
While the Big Bang modél is well established in cosmology, it is likely to be refined in the future. Little is known about the éarliest moments of the universe's history. ThePenrose-Hawking singularity theorems require the existence of a singularity at the beginning of cosmic time. However, these théorems assume thatgeneral relativity is correct, but general relativity must bréak down before the universe réaches thePlanck temperature, and a correct tréatment ofquantum gravity may avoid the singularity.[40]
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, éach of which entails untested hypotheses, are:
modéls including theHartle-Hawking boundary condition 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.[41]
brane cosmology modéls[42] in which inflation is due to the movement of branes instring theory; the pre-big bang modél; theekpyrotic modél, in which the Big Bang is the result of a collision between branes; and thecyclic model, a variant of the ekpyrotic modél in which collisions occur periodically.[43][44][45]
chaotic inflation, in which inflation events start here and there in a random quantum-gravity foam, éach léading to abubble universe expanding from its own big bang.[46]
Proposals in the last two categories see the Big Bang as an event in a much larger and older universe, ormultiverse, and not the literal beginning.
Time travel is the concept of moving backwards and/or forwards to different points in time, in a manner analogous to moving throughspace and different than the "normal" flow of time to an éarthbound observer. Although time travel has been aplot device infiction since the 19th century, and one-way travel into the future is arguably possible given the phenomenon oftime dilation in thetheory of relativity, it is currently unknown whether thelaws of physics would allow time travel to the past. Any technological device, whether fictional or hypothetical, that is used to achieve time travel is known as atime machine.
A central problem with time travel to the past is the violation ofcausality; should an effect precede its cause, it would give rise to the possibility oftemporal paradox. Some interpretations of time travel resolve this by accepting the possibility of travel betweenparallel realities oruniverses.
Théory would point toward there having to be a physicaldimension in which one could travel to, where thepresent (i.e. the point that which you are léaving) would be present at a point fixed in either the past or future. Seeing as this théory would be dependent upon the théory of amultiverse, it is uncertain how or if it would be possible to just prove the possibility of time travel.
Even in the presence of timepieces, different individuals may judge an identical length of time to be passing at different rates.[rujukan?] 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 psychologistJean Piaget called this form of time perception "lived time."[rujukan?]
This common experience was used to familiarize the general public to the idéas presented byEinstein's théory of relativity in a 1930 cartoon bySidney "George" Strube:[47][48]
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,— Einstein: Braffo! You the idea haf! [sic] 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 thekappa effect,[49] 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 appéars to be directly affected, in these cases, by the perception of spatial intervals.
Time also appéars to pass more quickly as one gets older.[rujukan?]Stephen Hawking suggests that the perception of time is a ratio:Unit of Time : Time Lived.[rujukan?] For example, one hour to a six-month-old person would be approximately "1:4032", while one hour to a 40-yéar-old would be "1:349,440". Therefore an hour appéars much longer to a young child than to an aged adult, even though the méasure of time is the same.
Altered states of consciousness are sometimes characterized by a different estimation of time. Some psychoactive substances – such asentheogens – may also dramatically alter a person's temporal judgement. When viewed under the influence of such substances asLSD,psychedelic mushrooms andpeyote, a clock may appéar to be a strange reference point and a useless tool for méasuring the passage of events as it does not correlate with the user's experience. At higher doses, time may appéar 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.[rujukan?]Marijuana, a milder psychedelic, may also distort the perception of time to a lesser degree.[50]
The practice ofmeditation, 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'.[rujukan?]
Culture is another variable contributing to the perception of time. AnthropologistBenjamin Lee Whorf reported after studying theHopi 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…"[51] Whorf's assertion has been challenged and modified. Pinker debunks Whorf's claims about time in the Hopi language, pointing out that the anthropologist Malotki (1983) has found that the Hopi do have a concept of time very similar to that of other cultures; they have units of time, and a sophisticated calendar.[52]
Insociology andanthropology,time discipline is the general name given tosocial andeconomic rules, conventions, customs, and expectations governing the méasurement of time, the social currency and awareness of time méasurements, and péople's expectations concerning the observance of these customs by others.
The use of time is an important issue in understandinghuman behaviour,education, andtravel behaviour.Time use research 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 withtechnology, as thetelevision or theInternet créated 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 intransport, 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 disputedtime budget hypothesis.
Time management 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 réached in the appropriate amount of time. Calendars and day planners are common examples of time management tools.
Artikel atawa bagian artikel ieu butuh leuwih loba réferénsi sangkan pasti. Mangga bantosngédit artikel ieu kalawan nambihkeun réferénsi. Tag ieu dibéré dina July 2008
↑Duff, Michael J.. "Trialogue on the number of fundamental constants" (PDF). Institute of Physics Publishing for SISSA/ISAS. Diakses pada 2 Pébruari 2008. 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."
↑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 ofwrong statements."
↑Rynasiewicz, Robert : Johns Hopkins University (2004-08-12)."Newton's Views on Space, Time, and Motion".Stanford Encyclopedia of Philosophy. Stanford University. Diakses tanggal2008-01-10.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 [sic~to] anything external, and thus without reference to any change or way of measuring of time (e.g., the hour, day, month, or year).Unknown parameter|copyright= ignored (bantuan)
↑Markosian, Ned "Time". The Stanford Encyclopedia of Philosophy (Winter 2002 Edition). Ed. Edward N. Zalta. “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.”
↑Burnham, Douglas : Staffordshire University (2006)."Gottfried Wilhelm Leibniz (1646-1716) Metaphysics - 7. Space, Time, and Indiscernibles".The Internet Encyclopedia of Philosophy. Diakses tanggal2008-01-10.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.
↑Mattey, G. J. : UC Davis (1997-01-22)."Critique of Pure Reason, Lecture notes: Philosophy 175 UC Davis". Diakses tanggal2008-01-10.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."Archived 2005-03-14 diWayback Machine
↑McCormick, Matt : California State University, Sacramento (2006)."Immanuel Kant (1724-1804) Metaphysics : 4. Kant's Transcendental Idealism".The Internet Encyclopedia of Philosophy. Diakses tanggal2008-01-10.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.
↑Richards, E. G. (1998).Mapping Time: The Calendar and its History. Oxford University Press. pp. 3–5.
↑Salah ngutip: Tag<ref> tidak sah; tidak ditemukan teks untuk ref bernamaRudgley
↑Barnett, Jo EllenTime's Pendulum: The Quest to Capture Time - from Sundials to Atomic Clocks Plenum, 1998ISBN 0-306-45787-3 p.28
↑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
↑North, J. (2004)God's Clockmaker: Richard of Wallingford and the Invention of Time. Oxbow Books.ISBN 1-85285-451-0
↑Watson, E (1979) "The St Albans Clock of Richard of Wallingford".Antiquarian Horology 372-384.
↑abcCraig, William Lane (June 1979), "Whitrow and Popper on the Impossibility of an Infinite Past",The British Journal for the Philosophy of Science30 (2): 165-170 [165-6]
↑Newton, Isaac (1726).The Principia, 3rd edition. Translated by I. Bernard Cohen and Anne Whitman, University of California Press, Berkeley, 1999.
↑Gottfried Martin,Kant's Metaphysics and Theory of Science
↑Herman M. Schwartz,Introduction to Special Relativity, McGraw-Hill Book Company, 1968, hardcover 442 pages, seeISBN 0-88275-478-5 (1977 edition), pp. 10-13
↑A. Einstein, H. A. Lorentz, H. Weyl, H. Minkowski,The Principle of Relativity, Dover Publications, Inc, 2000, softcover 216 pages,ISBN 0-486-60081-5, See pp. 37-65 for an English translation of Einstein's original 1905 paper.
↑Hawking, Stephen."The Beginning of Time". University of Cambridge. Diakses tanggal2008-01-10.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.Archived 2007-12-28 diWayback Machine
↑Hawking, Stephen (2006-02-27)."Professor Stephen Hawking lectures on the origin of the universe". University of Oxford. Diakses tanggal2008-01-10.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.'Archived 2007-05-14 diWayback Machine
↑Ghandchi, Sam : Editor/Publisher (2004-01-16)."Space and New Thinking". Diakses tanggal2008-01-10.and as Stephen Hawking puts it, asking what was before Big Bang is like asking what is North of North Pole, a meaningless question.
↑Adler, Mortimer J., Ph.D."Natural Theology, Chance, and God". Diakses tanggal2008-01-10.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. "The Great Ideas Today". Encylopaedia Britannica. (1992).
↑Adler, Mortimer J., Ph.D."Natural Theology, Chance, and God". Diakses tanggal2008-01-10.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. 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. "The Great Ideas Today". Encylopaedia Britannica. (1992).
↑Hawking, Stephen."The Beginning of Time". University of Cambridge. Diakses tanggal2008-01-10.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.Archived 2007-12-28 diWayback Machine
↑Hawking, Stephen; and Ellis, G. F. R. (1973).The Large Scale Structure of Space-Time. Cambridge: Cambridge University Press.ISBN 0-521-09906-4.
↑Wada Y, Masuda T, Noguchi K, 2005, "Temporal illusion called 'kappa effect' in event perception" Perception 34 ECVP Abstract Supplement
↑"Cannabis Effects".Erowid. Diakses tanggal2008-02-15.Time sense altered: cars seem like they are moving too fast, time dilation and compression are common at higher doses.
↑Carroll, John B. (ed.)(1956).Language Thought and Reality. Selected Writings of Benjamin Lee Whorf. MIT Press, Boston, Massachusetts.ISBN 0-262-73006-5 9780262730068
Barbour, Julian (1999).The End of Time: The Next Revolution in Physics.ISBN 0-19-514592-5.Unknown parameter|Publisher= ignored (|publisher= suggested) (bantuan)
Das, Tushar Kanti (1990).The Time Dimension: An Interdisciplinary Guide. New York: Praeger.ISBN 0-275-92681-8.- Reséarch bibliography
Whitrow, Gerald J. (1973).The Nature of Time. Holt, Rinehart and Wilson (New York).
Whitrow, Gerald J. (1980).The Natural Philosophy of Time. Clarendon Press (Oxford).
Whitrow, Gerald J. (1988).Time in History. The evolution of our general awareness of time and temporal perspective. Oxford University Press.ISBN 0-19-285211-6.
Dowden, Bradley (California State University, Sacramento) (2007). "Time". The Internet Encyclopedia of Philosophy. Ed. James Fieser, Ph.D., Bradley Dowden, Ph.D.. Retrieved on2008-01-31.
Mcdonough, Jeff (Harvard University) (Winter 2007). "Leibniz's Philosophy of Physics". The Stanford Encyclopedia of Philosophy. Ed. Edward N. Zalta. Stanford University. Retrieved on2008-01-31.
Ross, Kelley L., Ph.D. (Los Angeles Valley College)."The Clarke-Leibniz Debate (1715-1716)". The Proceedings of the Friesian School, Fourth Series (1996, 1999, 2001). Diakses tanggal2008-01-17.
Ross, Kelley L., Ph.D. (Los Angeles Valley College)."Three Points in Kant's Theory of Space and Time". The Proceedings of the Friesian School, Fourth Series (1996, 1999, 2001). Diakses tanggal2008-01-17.
Savitt, Steven, Ph.D. (University of British Columbia) (Fall 2007). "Being and Becoming in Modern Physics". The Stanford Encyclopedia of Philosophy. Ed. Edward N. Zalta. Retrieved on2008-01-17.
Wilson, Catherine (City University of New York) (Summer 2004). "Kant and Leibniz". The Stanford Encyclopedia of Philosophy. Ed. Edward N. Zalta. Stanford University. Retrieved on2008-01-31.
Exploring Time from Planck Time to the lifespan of the universe
Time ServerArchived 2008-09-15 diWayback Machine Calling to a different time zone; This site can be used to work out what time you should call. Also has some good "history of time" information and information about computer time servers and gps time.
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