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Past
Vassily Maximov, "Everything is in the past" (1889).
The past is the portion of time that has already occurred;[1] it is the opposite of the future.
Contents
- 1 Overview
- 2 Philosophy and science
- 3 Quote
- 4 See also
- 5 References
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The past is contrasted with the present. It is also regarded as the conglomerate of events that happened in a certain point in time, within the Space-time continuum. The aforementioned conception is closely related to Albert Einstein's relativity theory. The past is the object of such fields as history, archaeology, archaeoastronomy, chronology, geology, (historical geology), historical linguistics, law, paleontology, paleobotany, paleoethnobotany, palaeogeography, paleoclimatology, and cosmology.
Humans have recorded the past since ancient times, and to some extent, one of the defining characteristics of human beings is that they are able to record the past, recall it, remember it and confront it with the current state of affairs, thus enabling them to plan accordingly for the future, and to theorise about it as well.
According to presentism, the past does not strictly exist; however, the methods of all sciences study the world's past, through the process of evaluating evidence. Presentism is compatible with Galilean relativity, in which time is independent of space but is probably incompatible with Lorentzian/Einsteinian relativity in conjunction with certain other philosophical theses which many find uncontroversial.
A visualisation of the past light cone (at bottom), the present, and the future light cone in 2D space.
In classical physics the past is just a half of the timeline. In special relativity the past is considered as absolute past or the past cone. In Earth's scale the difference between "classical" and "relativist" past is less than 0.05 s, so it can be neglected in most cases.
In the modern theory of relativity, the conceptual observer is at a geometric point in both space and time at the apex of the 'light cone' which observes events laid out in time as well as space. Different observers can disagree on whether two events at different locations occurred simultaneously depending if the observers are in relative motion (see relativity of simultaneity). This theory depends upon the idea of time as an extended thing and has been confirmed by experiment and has given rise to a philosophical viewpoint known as four dimensionalism. However, although the contents of an observation are time-extended, the conceptual observer, being a geometric point at the origin of the light cone, is not extended in time or space. This analysis contains a paradox in which the conceptual observer contains nothing, even though any real observer would need to be the extended contents of an observation to exist. This paradox is partially resolved in Relativity theory by defining a 'frame of reference' to encompass the measuring instruments used by an observer. This reduces the time separation between instruments to a set of constant intervals.[2]
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For more details on axis of time, see Arrow of time.
Those who cannot remember the past are condemned to repeat it.
– George Santayana, The Life of Reason[3]
Look up past in
Wiktionary, the free dictionary.
- Antiquarian
- Fossil
- Memory
- Past tense
- Retro
- ^ Hegeler, E. C., & Carus, P. (1890). The Monist. La Salle, Ill. [etc.]: Published by Open Court for the Hegeler Institute. page 443.
- ^ Petkov 2005
- ^ Santayana, George (1905). The Life of Reason: Reason in Common Sense. New York: Charles Scribner's Sons, 284.
 Time |
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| Major concepts |
Time · Eternity · Arguments for eternity · Immortality
Deep time · History · Past · Present · Future · Futurology
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| Measurement and Standards |
Chronometry · UTC · UT · TAI · Second · Minute · Hour · Sidereal time · Solar time · Time zone
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Calendar · Day · Week · Month · Year · Tropical year · Julian · Gregorian · Islamic
Intercalation · Leap second · Leap year
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| Chronology |
Astronomical chronology · Geologic Time · Geological history · Geochronology · Archaeological dating
Calendar era · Regnal year · Chronicle · Timeline · Periodization
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| Religion and Mythology |
Time and fate deities · Wheel of time · Kāla · Kalachakra · Prophecy · Dreamtime
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| Philosophy |
Causality · Eternalism · Eternal return · Event · The Unreality of Time · A-series and B-series · B-Theory of time
Endurantism · Four dimensionalism · Perdurantism · Presentism · Temporal finitism · Temporal parts
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| Physical Sciences |
Time in physics · Spacetime · Absolute time and space · T-symmetry
Arrow of time · Chronon · Fourth dimension · Planck epoch · Planck time · Time domain
Theory of relativity · Time dilation · Gravitational time dilation · Coordinate time · Proper time
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| Biology |
Chronobiology · Circadian rhythms
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| Psychology |
Consciousness and spacetime · Mental chronometry · Reaction time · Sense of time · Specious present
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| Sociology and Anthropology |
Futures studies · Long Now Foundation · Time discipline · Time use research
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| Economics |
Newtonian time in economics · Time value of money · Time Banking · Time-based currency
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| Related topics |
Space · Duration · Time capsule · Time travel · Time signature · System time · Metric time · Hexadecimal time · Carpe diem · Tempus fugit
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