Physics:Present

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Short description: Period of time occurring now

The present is the period of time that is occurring now. The present is contrasted with the past, the period of time that has already occurred, and the future, the period of time that has yet to occur.

It is sometimes represented as a hyperplane in space-time,[1] typically called "now", although modern physics demonstrates that such a hyperplane cannot be defined uniquely for observers in relative motion. The present may also be viewed as a duration.[2][3]

Historiography

Contemporary history describes the historical timeframe immediately relevant to the present time and is a certain perspective of modern history.

Philosophy and religion

Quotations

You shouldn't chase after the past or place expectations on the future. What is past is left behind. The future is as yet unreached. Whatever quality is present you clearly see right there, right there.

– Buddha, Bhaddekaratta Sutta[4]

What we perceive as present is the vivid fringe of memory tinged with anticipation.

– Alfred North Whitehead, The Concept of Nature[5]

Philosophy of time

"The present" raises the question: "How is it that all sentient beings experience now at the same time?"[6] There is no logical reason why this should be the case and no easy answer to the question.[citation needed]

In Buddhism

Buddhism and many of its associated paradigms emphasize the importance of living in the present moment—being fully aware of what is happening, and not dwelling on the past or worrying about the future.[7] This does not mean that they encourage hedonism, but merely that constant focus on one's current position in space and time (rather than future considerations, or past reminiscence) will aid one in relieving suffering. They teach that those who live in the present moment are the happiest.[8] A number of meditative techniques aim to help the practiser live in the present moment.

Christianity and eternity

Christianity views God as being outside of time and, from the divine perspective past, present and future are actualized in the now of eternity. This trans-temporal conception of God has been proposed as a solution to the problem of divine foreknowledge (i.e. how can God know what we will do in the future without us being determined to do it) since at least Boethius.[9] Thomas Aquinas offers the metaphor of a watchman, representing God, standing on a height looking down on a valley to a road where past, present and future, represented by the individuals and their actions strung out along its length, are all visible simultaneously to God.[10] Therefore, God's knowledge is not tied to any particular date.[11]

Physical science

Special relativity

A visualisation of the present (dark blue plane) and past and future light cones in 2D space.

The original intent of the diagram on the right was to portray a 3-dimensional object having access to the past, present, and future in the present moment (4th dimension).[clarification needed]

It follows from Albert Einstein's Special Theory of Relativity that there is no such thing as absolute simultaneity. When care is taken to operationalise "the present", it follows that the events that can be labeled as "simultaneous" with a given event, can not be in direct cause-effect relationship. Such collections of events are perceived differently by different observers. Instead, when focusing on "now" as the events perceived directly, not as a recollection or a speculation, for a given observer "now" takes the form of the observer's past light cone. The light cone of a given event is objectively defined as the collection of events in causal relationship to that event, but each event has a different associated light cone. One has to conclude that in relativistic models of physics there is no place for "the present" as an absolute element of reality, and only refers to things that are close to us.[12] Einstein phrased this as: "People like us, who believe in physics, know that the distinction between past, present, and future is only a stubbornly persistent illusion".[13][14]

Cosmology

Further information: Astronomy:Physical cosmology, Astronomy:Cosmic time, and Astronomy:Chronology of the universe

In physical cosmology, the present time in the chronology of the universe is estimated at 13.8 billion years after the singularity determining the arrow of time. In terms of the cosmic expansion history, it is in the dark-energy-dominated era, after the universe's matter content has become diluted enough for dark energy to dominate the total energy density. It is also in the universe's Stelliferous Era, after enough time for superclusters to have formed (at about 5 billion years), but before the accelerating expansion of the universe has removed the local supercluster beyond the cosmological horizon (at about 150 billion years).[15]

Archaeology, geology, etc.

In radiocarbon dating, the "present" is defined as AD 1950.

Grammar

In English grammar, actions are classified according to one of the following twelve verb tenses: past (past, past continuous, past perfect, or past perfect continuous), present (present, present continuous, present perfect, or present perfect continuous), or future (future, future continuous, future perfect, or future perfect continuous).[16] The present tense refers to things that are currently happening or are always the case.[16] For example, in the sentence, "she walks home everyday," the verb "walks" is in the present tense because it refers to an action that is regularly occurring in the present circumstances.

Verbs in the present continuous tense indicate actions that are currently happening and will continue for a period of time.[16] In the sentence, "she is walking home," the verb phrase "is walking" is in the present continuous tense because it refers to a current action that will continue until a certain endpoint (when "she" reaches home). Verbs in the present perfect tense indicate actions that started in the past and is completed at the time of speaking.[17] For example, in the sentence, "She has walked home," the verb phrase "has walked" is in the present perfect tense because it describes an action that began in the past and is finished as of the current reference to the action. Finally, verbs in the present perfect continuous tense refer to actions that have been continuing up until the current time, thus combining the characteristics of both the continuous and perfect tenses.[16] An example of a present perfect continuous verb phrase can be found in the sentence, "she has been walking this route for a week now," where "has been walking" indicates an action that was happening continuously in the past and continues to happen continuously in the present.

See also

References

  1. ↑ Sattig, Thomas (2006-05-11) (in en). The Language and Reality of Time. Clarendon Press. pp. 37. ISBN 978-0-19-927952-4. https://books.google.com/books?id=qYNv2zpHOmwC. 
  2. ↑ James, William (1890) (in en). The Principles of Psychology. H. Holt. pp. 609. https://books.google.com/books?id=JLcAAAAAMAAJ. 
  3. ↑ Hodder, Alfred (1901) (in en). The Adversaries of the Sceptic: Or, The Specious Present, a New Inquiry Into Human Knowledge. S. Sonnenschein & Company, Limited. pp. 36–56. https://books.google.com/books?id=uZ5RAAAAMAAJ&pg=PA36. 
  4. ↑ "Bhaddekaratta Sutta: An Auspicious Day". https://www.accesstoinsight.org/tipitaka/mn/mn.131.than.html. 
  5. ↑ Whitehead, Alfred North. The Concept of Nature (Cambridge: Cambridge University Press, 1930), p. 73
  6. ↑ McInerney, Peter K. (1992). Time and Experience. Temple University Press. p. 44. ISBN:978-1-56639-010-1.
  7. ↑ Hạnh, Thích Nhất (1990). Our appointment with life: the Buddha's teaching on living in the present. Parallax Press. p. 53. ISBN:978-0-938077-36-7.
  8. ↑ Rahula, Walpola (1974). What the Buddha Taught. Grove Press. p. 72. ISBN 9780802130310. https://books.google.com/books?id=_WduwVbiLSsC&q=what+the+buddha+taught. Retrieved 2010-04-28. 
  9. ↑ Consolatio Philosophae, Bk. 4
  10. ↑ Cline, Austin. "God Is Eternal: Timeless vs. Everlasting" (in en). https://www.learnreligions.com/god-is-eternal-251051. 
  11. ↑ Irwin, William; White, Mark D. (2009). Watchmen and Philosophy: A Rorschach Test. John Wiley and Sons. p. 128.
  12. ↑ Rovelli, Carlo (8 May 2018). The order of time. Segre, Erica; Carnell, Simon (translation). New York. ISBN 978-0-7352-1610-5. OCLC 1020300173. 
  13. ↑ Letter from Einstein to the family of his lifelong friend Michele Besso, after learning of his death, (March 1955) as quoted in Science and the Search for God: Disturbing the Universe (1979) by Freeman Dyson, Ch. 17, "A Distant Mirror",
  14. ↑ Tippett, Krista. "Einstein's God (NPR)". Speaking of Faith. American Public Media. http://speakingoffaith.publicradio.org/programs/einsteinsgod/unheardcuts.shtml. 
  15. ↑ Krauss, Lawrence M.; Starkman, Glenn D. (2000). "Life, the Universe, and Nothing: Life and Death in an Ever-expanding Universe". Astrophysical Journal 531 (1): 22–30. doi:10.1086/308434. Bibcode: 2000ApJ...531...22K. 
  16. ↑ 16.0 16.1 16.2 16.3 "Verb tenses". Oxford University Press. https://en.oxforddictionaries.com/grammar/verb-tenses. 
  17. ↑ "Present Perfect" (Web). Merriam-Webster. n.d.. https://www.merriam-webster.com/dictionary/present%20perfect. 

Bibliography

  • Greene, Brian, (2004). The Fabric of the Cosmos: Space, Time, and the Texture of Reality Knopf. ISBN:0-375-41288-3
  • Stepath, Katrin, (2006). Gegenwartskonzepte, Würzburg. ISBN:3-8260-3292-6

External links



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