There are two distinct views on the meaning of the word '''Time'''.
One view is that time is part of the fundamental structure of the
universe, a
dimension in which events occur in
sequence, and time itself is something that can be measured. This is the
realist's view, to which
Sir Isaac Newton subscribed, and hence is sometimes referred to as
Newtonian time.
[1]
A contrasting view is that time is part of the fundamental intellectual structure (together with
space and
number). Within this structure, humans sequence events,
quantify the duration of events and the intervals between them, and compare the
motions of objects. In this second view, time does not refer to any kind of entity that "flows", that objects "move through", or that is a "container" for events. This view is in the tradition of
Gottfried Leibniz[2] and
Immanuel Kant,
[3][4] in which time, rather than being an objective thing to be measured, is part of the measuring system used by humans.
In
physics, time and space are considered
fundamental quantities (i.e. they cannot be defined in terms of other quantities because other quantities - such as
velocity,
force,
energy, etc - are already defined in terms of them). Thus the only definition possible is an
operational one, in which time is defined by the process of
measurement and by the
units chosen.
Periodic events and periodic motion have long served as standards for units of time. Examples are the apparent motion of the sun across the sky, the phases of the moon, the swing of a pendulum, heartbeats, etc. Currently, the unit of time interval (the
second) is defined as a certain number of
hyperfine transitions in
Cesium atoms (see below).
Time has long been a major subject of
science,
philosophy, and
art. Its measurement has occupied scientists and
technologists, and was a prime motivation in
astronomy. Time is also of significant social importance, having economic value ("
time is money") as well as personal value, due to an
awareness of the limited time in each day and in human lifespans.
Measurement
Time is currently one of the few
fundamental quantities. These are quantities which cannot be defined via other quantities because there is nothing more fundamental that is presently known. Thus, similar to definitions of other fundamental quantities (like
space and
mass), time is defined by the
units used to measure it and the
method of its measurement. In essence, this definition defines time itself which otherwise is left undefined.
The origins of our current measurement system go back to the
Sumerian civilization of approximately 2000
BC.
This is known as the Sumerian
Sexagesimal 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.
Measurement devices
A large variety of
devices have been invented to measure time. The study of these devices is called
horology.
An
Egyptian device dating to c.
1500 BCE, similar in shape to a bent
T-square, 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
noon, the device was turned around so that it could cast its shadow in the evening direction.
[5]
A
sundial uses a
gnomon to cast a shadow on a set of markings which were calibrated to the
hour. The position of the shadow marked the hour in
local time.
Pliny the Elder records that the first sundial in Rome was looted from
Catania,
Sicily (
264 BCE), which gave the incorrect time for a century, until the markings appropriate for the latitude of
Rome were used (
164 BCE).
[6] Noontime was an event which could be marked by the time of the shortest shadow on a sundial. This was used in Rome to judge when a court of law was open; lawyers had to be at the court by that time.
The most accurate timekeeping devices of the ancient world were the
waterclock or ''clepsydra'', first found in Egypt. A waterclock was found in the tomb of
pharaoh Amenhotep I (1525 - 1504 BCE). Waterclocks were used in
Alexandria, and then worldwide, for example in Greece, from c.
400 BCE. They could be used to measure the hours even at night, but required manual timekeeping to replenish the flow of water.
Plato is said to have invented a water-based alarm clock. It depended on the nightly overflow of a vessel containing lead balls, which would float in a columnar vat. The vat would hold an increasing supply of water supplied by a cistern. Eventually the vessel would float high enough to tip over. The lead balls would then cascade onto a copper platter. The resultant clangor would then awaken his students at the Academy (
378 BCE).
[7] The
Greeks and
Chaldeans regularly maintained timekeeping records as an essential part of their astronomical observations. In particular, Arab engineers improved on the use of waterclocks up to the Middle Ages.
[8]
The
hourglass uses the flow of sand to measure the flow of time. They were used in navigation.
Ferdinand Magellan used 18 glasses on each ship for his circumnavigation of the globe (
1522).
[9] The English word
clock actually comes from French, Latin, and German words that mean
bell. The passage of the hours at sea were marked by bells, and denoted the time (see
ship's bells). The hours were marked by bells in the abbeys as well as at sea.
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.
Richard of Wallingford (1292–1336), abbot of St. Alban's abbey, famously built a
mechanical clock as an astronomical
orrery about 1330.
[10][11]
The most common devices in day-to-day life are the
clock, for periods less than a day, and the
calendar, for periods longer than a day. Clocks can range from
watches, to more exotic varieties such as the
Clock of the Long Now. 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
pendulum. There are also a variety of different
calendars, for example the
Lunar calendar and the
Solar calendar, although the
Gregorian calendar is the most commonly used.
A "chronometer" is a portable timekeeper that meets certain precision standards. Initially, the term was used to refer to the
marine chronometer, a timepiece used to determine
longitude by means of
celestial navigation. More recently, the term has also been applied to the
chronometer watch, a
wristwatch that meets precision standards set by the Swiss agency
COSC. Over 1,000,000 "Officially Certified Chronometer" certificates, mostly for mechanical wrist-chronometers (wristwatches) with sprung balance oscillators, are being delivered each year, after passing the COSC's most severe tests and being singly identified by an officially recorded individual
serial number. According to COSC, a chronometer is a high-precision watch capable of displaying the seconds and housing a movement that has been tested over several days, in different positions, and at different temperatures, by an official, neutral body (COSC). Each movement is individually tested for several consecutive days, in five positions and at three temperatures. Any watch with the denomination "chronometer" is provided with a certified movement.
The most accurate type of timekeeping device is currently the
atomic clock, which are used to calibrate other clock and timekeeping instruments.
Today, the
GPS global positioning systems in coordination with the
NTP network time protocol can be used to synchronize timekeeping systems across the globe.
Definitions and standards
The
SI base unit for time is the
SI second. From the second, larger units such as the
minute,
hour and
day 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
leap-second. They are, however, officially accepted for use ''with'' the International System. There are no fixed ratios between seconds and
months or
years as months and years have significant variations in length.
[12]
The official SI definition of the second is as follows:
[12][14]
Previous to 1967, the second was defined as:
The definition of time is extremely important in
science and for our everyday life. All known properties of time follow directly from this definition. For example, this definition of time coupled with current definition of
space makes our space and time to be
Minkowski space-time and makes
special relativity theory absolutely correct (
true) by definition.
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
atomic clocks around the world, known as the
International Atomic Time (TAI). This is the yardstick for other time scales, including
Coordinated Universal Time (UTC), which is the basis for civil time.
Earth is split up into a number of
time zones. Most time zones are exactly one hour apart, and by convention compute their local time as an offset from UTC or
Greenwich Mean Time. In many locations these offsets vary twice yearly due to
daylight saving time transitions.
Chronology
Another form of time measurement consists of studying the
past. Events in the past can be ordered in a sequence (creating a
chronology), and be put into chronological groups (
periodization). One of the most important systems of periodization is
geologic time, which is a system of periodizing the events that shaped the
Earth and its life. Chronology, periodization, and interpretation of the past are together known as the study of
history.
Interpretations
Many ancient philosophers wrote lengthy essays on time. A famous analogy compared the time of life to the passing of sand through an hourglass (a common measuring device for time in the past). The sand at the top is associated with the future, and, one tiny grain at a time, the future flows through the present into the past (associated with the sandpile at the bottom of hourglass). The past: ever expanding, the future: ever decreasing, but the future grains become amassed into the past through the present. This was widely discussed in around the 3rd century CE.
The earliest recorded philosophy of time was expounded by
Ptahhotep, who lived c.2650–2600 BCE said: ''"Do not lessen the time of following desire, for the wasting of time is an abomination to the spirit."''
In the
Old Testament book
Ecclesiastes, thought to have been written by
Solomon (970–928 BCE), time (as the Hebrew word עת ''’êth'' is often translated, as well as "season") was traditionally regarded as a medium for the passage of
predestined events. (Another word, זמן ''zman'', was current as meaning ''time fit for an event'', and is used as the modern
Hebrew equivalent to the English word "time".)
Around 500 BC
Heraclitus, held that the passage of time and the future both lay beyond the possibility of human influence: ''"Everything flows and nothing abides; everything gives way and nothing stays fixed.'' ''You cannot step twice into the same river, for other waters and yet others, go flowing on.'' ''Time is a child, moving counters in a game; the royal power is a child's."''
Time in philosophy
Main articles: Philosophy of time
In Book 11 of
St. Augustine's Confessions, 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.
[15] Newton believed time and
space form a
container for
events, which is as
real as the
objects it contains.
In contrast to Newton's belief in absolute space, and closely related to Kantian time,
Leibniz believed that time and space are a conceptual apparatus describing the interrelations between events. The differences between Leibniz's and Newton's interpretations came to a head in the famous
Leibniz-Clarke Correspondence. Leibniz thought of time as a fundamental part of an
abstract conceptual framework, together with
space and
number, 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 the ''
Critique of Pure Reason'', described time as an ''
a priori'' intuition that allows us (together with the other ''a priori'' intuition,
space) to comprehend sense experience. With Kant, neither space nor time are conceived as
substances, but rather both are elements of a systematic mental
framework necessarily structuring the experiences of any rational agent, or observing subject. Spatial
measurements are used to
quantify how far apart
objects are, and temporal measurements are used to quantify how far apart
events occur. Similarly,
Schopenhauer stated in the preface to his ''On the Will in Nature'' that "Time is the condition of the ''possibility'' of succession."
In
Existentialism, time is considered fundamental to the question of
being, in particular by the philosopher
Martin Heidegger. See
Ontology.
Einstein 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
Minkowski space) which in turn results in
Lorentz transformation and in entanglement of all other important derivative physical quantities (like energy, momentum, mass, force, etc) in a certain 4-vectorial way (see
special relativity for more details).
Henri Bergson 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.
[16]
Time as "unreal"
In 5th century BC
Greece,
Antiphon the
Sophist, in a fragment preserved from his chief work ''On Truth'' held that: ''"Time is not a reality (hupostasis), but a concept (noêma) or a measure (metron)."''
Parmenides went further, maintaining that time, motion, and change were illusions, leading to the
paradoxes of his follower
Zeno.
[17]
Time as illusion is also a common theme in
Buddhist thought,
[18] and some modern philosophers have carried on with this theme.
J. M. E. McTaggart's 1908 ''
The Unreality of Time'', for example, argues that time is unreal (see also
The flow of time).
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
Julian Barbour in his
The End of Time argue that quantum equations of the universe take their true form when expressed in the timeless
configuration spacerealm containing every possible "Now" or momentary configuration of the universe, which he terms 'platonia'.
[19]
Linear time
In general, the
Judaeo-Christian concept, based on the
Bible, is that time is linear, with a beginning, the act of
creation by
God. The
Christian view assumes also an end, the eschaton, expected to happen when
Christ returns to earth in the
Second Coming to judge the living and the dead. This will be the consummation of the world and time.
St Augustine's
City of God was the first developed application of this concept to world history. The Christian view is that God and the supernatural world are outside time and exist in
eternity. This view relies on interpretation however, for some Jewish and Christian sects believe time may in fact be cyclical. It is also possible to see time as having more than one dimension. In this view, over time the universe branches into multiple alternative universes where different events have occurred.
Cyclical time
Main articles: Time Cycles,
Wheel of time
The
Indian religions such as
Hinduism,
Buddhism and
Jainism, have a concept of a
wheel of time, that regards time as
cyclical and
quantic consisting of repeating ages that happen to every being of the Universe between birth and extinction. In recent years this cyclical vision of time has been embraced by theorists of
quantic space-time and
systems theory. This view has also not been scientifically verified.
Time in the physical sciences
From the age of
Newton up until
Einstein'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.
[20] The science of classical mechanics is based on this Newtonian idea of time.
Einstein, in his
special theory of relativity,
[21] 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.
Time in classical mechanics
In
classical 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 each other produce a mathematical concept of time that works pretty well for describing the everyday phenomena of most people's experience.
Time in 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.
Spacetime
A
tesseract, a cube in 3 dimensions extended to a fourth, as a description of time; adhering to defined finite bounds, all possibilities for this configuration are conceptually representable.
Modern
physics views the curvature of
spacetime around an object as much a feature of that object as are its
mass and
volume.
Time has historically been closely related with
space, the two together comprising
spacetime in
Einstein's special relativity and
general relativity. According to these theories, the concept of time depends on the
spatial reference frame of the observer(s), 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
light cones, which never change. The ''past'' is the set of events that can send light signals to the observer, the future the events to which s/he can send light signals. All else is the ''present'' and within that set of events the very time-order differs for different observers.
Natural unit of time
Main articles: Planck time
'Planck time' (~
5.4 × 10−44 seconds) is the unit of time in the system of
natural units known as
Planck units. 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
loop quantum gravity.
Time quanta
Time quanta is a hypothetical concept. In the modern quantum theory (the
Standard Model of particle physics) and in
general relativity time is not quantized.
Time dilation
Main articles: Time dilation
Einstein said that "The only reason for time is so that everything does not happen at once". In this regard, Einstein said that time was basically what a clock reads; the clock can be any action or change, like the movement of the sun. Einstein showed that people traveling at different speeds will measure different times for events and different distances between objects, though these differences are minute unless one is traveling at a speed close to that of light. Many
subatomic 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 measured to travel further and survive longer than expected (a
muon is one example). According to the
special theory of relativity, in the high-speed particle's
frame of reference, it exists, on the average, for a standard amount of time known as its
mean 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''): "Two
events 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 simultaneity is also relative, 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.
Arrow of time
Main articles: 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 'arrow of time'. The exceptions include the
Second law of thermodynamics, which states that
entropy must increase over time (see
Entropy); the
cosmological arrow of time, which points away from the
Big Bang, and the radiative arrow of time, caused by
light only traveling forwards in time. In
particle physics, there is also the weak arrow of time, from
CPT symmetry, and also
measurement in
quantum mechanics (see
Measurement in quantum mechanics).
Time and the Big Bang
According to some of the latest scientific theories, time began with the
Big Bang.
Stephen Hawking (borrowing a line of thought from
Augustine of Hippo) has commented that trying to ascertain what happened before time began is like trying to find out what is north of the North Pole, and that such questions are self-contradictory, and thus without meaning.
[22] Hawking has also stated, along with other theorists, 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.
[23] 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 one
Planck time (5 × 10
−44 seconds) after the Big Bang will likely remain pure speculation.
Time travel in science fiction
Main articles: Time travel
Time travel is the concept of moving backward or forward to different points in time, in a manner analogous to moving through
space. Additionally, some interpretations of time travel take the form of travel between
parallel realities or
universes. A central problem with time travel is that of logic - say, violation of
causality (when effect precedes the cause it is the consequence of) — which has given rise to a number of paradoxes (see
grandfather paradox).
Psychology
Different people may judge identical lengths of time quite differently. Time can "fly"; that is, a long period of time can seem to go by very quickly. Likewise, time can seem to "drag," as in when one performs a boring task. The psychologist
Jean Piaget called this form of time perception "lived time."
Time also appears to pass more quickly as one gets older. For example, a year for a five-year-old child is 20% of his entire life so far, however for a 50 year old adult a year is only 2% of his entire life so far; so with increasing age, each segment of time is a decreasing percentage of the person's total experience.
Altered states of consciousness are sometimes characterized by a different estimation of time. Some psychoactive substances--such as
entheogens--may also dramatically alter a person's temporal judgement. When viewed under the influence of such substances as
LSD,
psychedelic mushrooms and
peyote, 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, and even go backwards when under the influence of these agents. 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.
Marijuana may also distort the perception of time, although, to a lesser degree than psychedelics.
The practice of
meditation, 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'.
In explaining his
theory of relativity,
Albert Einstein is often quoted as saying that although sitting next to a pretty girl for an hour feels like a minute, placing one's hand on a hot stove for a minute feels like an hour. This is similar to the
Kappa effect. These are both intended to introduce the listener to the concept of the interval between two events being perceived differently by different observers.
Culture
Culture is another variable contributing to the perception of time. Anthropologist
Benjamin Lee Whorf reported after studying the Hopi 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…”
[24] 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 – and in fact have units of time, and a sophisticated calendar.
[25]
Use of time
The use of time is an important issue in understanding
human behaviour,
education, and
travel 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 with
technology, as the
television or the
Internet 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
transport, 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
time 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 reached in the appropriate amount of time. Calendars and day planners are common examples of time management tools.
Arlie Russell Hochschild and
Norbert Elias have written on the use of time from a sociological perspective.
References
1. Newton's Views on Space, Time, and Motion - Stanford University http://plato.stanford.edu/entries/newton-stm/
2. Leibniz on Space, Time, and Indiscernibles - Against the Absolute Theory -- Internet Encyclopedia of Philosophy http://www.iep.utm.edu/l/leib-met.htm#H7
3. Critique of Pure Reason - Lecture notes of G. J. Mattey, UC Davis http://www-philosophy.ucdavis.edu/mattey/kant/TIMELEC.HTM
4. Kant's Transcendental Idealism - Internet Encyclopedia of Philosophy http://www.iep.utm.edu/k/kantmeta.htm#H4
5. Jo Ellen Barnett, ''Time's Pendulum'' ISBN 0-306-45787-3 p.28
6. Jo Ellen Barnett, ''Time's Pendulum'' p.31
7. Jo Ellen Barnett, ''Time's Pendulum'' p.38
8. Jo Ellen Barnett, ''Time's Pendulum'' p.37
9. 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
10. North, J. (2004) ''God's Clockmaker: Richard of Wallingford and the Invention of Time''. Oxbow Books. ISBN 1-85285-451-0
11. Watson, E (1979) "The St Albans Clock of Richard of Wallingford". ''Antiquarian Horology'' 372-384.
12. The International System of Units (SI), 7th Edition, Organisation Intergouvernementale de la Convention du Métre, , , , 1998,
13. The International System of Units (SI), 7th Edition, Organisation Intergouvernementale de la Convention du Métre, , , , 1998,
14. Base unit definitions: Second
15. St.,Augustine, ''Confessions'', Book 11. http://ccat.sas.upenn.edu/jod/augustine/Pusey/book11 (Accessed 5/26/07).
16. ''Creative Evolution''. Translated by Arthur Mitchell. Mineola: Dover, 1998.
17. You are about to disappear Harry Foundalis
18. Buddhism and the illusion of time Tom Huston
19. Time is an illusion?
20. Herman M. Schwartz, ''Introduction to Special Relativity'', McGraw-Hill Book Company, 1968, hardcover 442 pages, see ISBN 0882754785 (1977 edition), pp. 10-13
21. 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.
22. http://www.ghandchi.com/312-SpaceEng.htm
23. Public lecture on the beginning of time by Hawking http://www.hawking.org.uk/lectures/bot.html
24. Carroll, John B. (ed.)(1956). [Language Thought and Reality. Selected Writings of Benjamin Lee Whorf. MIT Press, Boston, Massachusetts. [a href="http://worldcat.org/isbn/0262730065" ISBN 0262730065 9780262730068]
25. http://www.aber.ac.uk/media/Students/njp0001.html
See also
★
Anachronistic
★
Causality
★
Change
★
Chronology
★
Date and time notation by country
★
Duration
★
Eternal recurrence
★
Eternalism (philosophy of time)
★
Eternity
★
Exponential time
★
History
★
Horology
★
Kalachakra
★
Kappa Effect
★
List of cycles
★
Network Time Protocol (NTP)
★
Nonlinear (arts)
★
Multilinear
★
Periodization
★
Peter Lynds
★
Philosophy of physics
★
Presentism (philosophy of time)
★
Polynomial time
★
Quality time
★
Rate
★
Sense of time
★
Spacetime
★
System time
★
The growing block view
★
Time cube
★
Time scales and time standards
★
Time zone
★
Yuga
★ ''
A Brief History of Time''
★ ''
An Experiment with Time''
★ Leading scholarly organisations for researchers on the history and technology of time and timekeeping are:
★
★
Antiquarian Horological Society - AHS (United Kingdom)
★
★
Association Française des Amateurs d'Horlogerie Ancienne - AFAHA (France)
★
★
Chronometrophilia (Switzerland)
★
★
Deutsche Gesellschaft fur Chronometrie - DGC (Germany)
★
★
HORA Associazione Italiana Cultori di Orologeria Antica (Italy)
★
★
National Association of Watch and Clock Collectors - NAWCC (United States of America)
Special units of time
Further reading
★
The End of Time: The Next Revolution in Physics, , Julian, Barbour, , 1999, ISBN 0-19-514592-5
★
The Time Dimension: An Interdisciplinary Guide, , Tushar Kanti, Das, Praeger, 1990, ISBN 0275926818 - Research bibliography
★
About Time: Einstein's Unfinished Revolution, , Paul, Davies, , 1996, ISBN 0-684-81822-1
★
The Character of Physical Law, , Richard, Feynman, The MIT Press, 1994, ISBN 0-262-56003-8
★
Einstein's Clocks and Poincaré's Maps: Empires of Time, , Peter, Galison, W. W. Norton, 1992, ISBN 0-393-02001-0
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Arrow of Time: A Voyage through Science to Solve Time's Greatest Mystery, , Roger, Highfield, Random House, 1992, ISBN 0-449-90723-6
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It's About Time: Understanding Einstein's Relativity, , N. David, Mermin, Princeton University Press, 2005, ISBN 0-691-12201-6
★
The Emperor's New Mind: Concerning Computers, Minds, and the Laws of Physics, , Roger, Penrose, Oxford University Press, 1999, ISBN 0-19-286198-0
★
Time's Arrow and Archimedes' Point, , Huw, Price, Oxford University Press, 1996, ISBN 0-19-511798-0
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The Direction of Time, , Hans, Reichenbach, Dover, 1999, ISBN 0-486-40926-0
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Stiegler, Bernard, ''
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The Nature of Time, , Gerald J., Whitrow, Holt, Rinehart and Wilson (New York), 1973,
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The Natural Philosophy of Time, , Gerald J., Whitrow, Clarendon Press (Oxford), 1980,
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Time in History. The evolution of our general awareness of time and temporal perspective, , Gerald J., Whitrow, Oxford University Press, 1988, ISBN 0-19-285211-6
★
What is time? What is space?, , Carlo, Rovelli, Di Renzo Editore, 2006, ISBN 8883231465
External links
Perception of time
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Time and Its Discontents
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Subjective Perception of Time and a Progressive Present Moment: The Neurobiological Key to Unlocking Consciousness
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Time Perception I and
II
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The Order of Time: Platform for an Alternative Time Consciousness
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Time Perception Research at the University of Manchester
Physics
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A walk through Time
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Time Travel and Multi-Dimensionality
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Time and classical and quantum mechanics: Indeterminacy vs. discontinuity
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Time as a universal consequence of quanta
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Theories With Problems: What Is Time?
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Exploring the Nature of Time
Philosophy
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The Experience and Perception of Time from the
Stanford Encyclopedia of Philosophy.
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Is there a defensible argument for the non-existence of time?
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The Conceptual Sheme of Chinese Philosophical Thinking - Time
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Article on Time as Subjective Perception rather than Reified Abstract
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An article on Time and Universal Consciousness
Timekeeping
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Different systems of measuring time
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non-SI units
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UTC/TAI Timeserver
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Leapsecond
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Hex Time
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Florencetime.net
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BBC article on shortest time ever measured
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Federation of the Swiss Watch Industry FH
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American Watchmakers-Clockmakers Institute
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The World Clock - Time Zones
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World Local Times on Google Map by single click
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Current time in cities all over the world
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Interactive Map of World Time
Miscellaneous
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GMT and all other timezones...
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TimeTicker and the time tickers...
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World Time and Zones
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Official US time
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