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===Special relativity=== [[Image:World line.svg|upright=1.2|right|thumb|A visualisation of the present (dark blue plane) and past and future [[light cone]]s 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).{{clarify|date=March 2015}} It [[Logical consequence|follows from]] [[Albert Einstein]]'s [[Special relativity|Special Theory of Relativity]] that there is [[Relativity of simultaneity|no such thing as absolute simultaneity]]. When care is taken to [[Operational definition|operationalise]] "the present", it follows that the events that can be labeled as "simultaneous" with a given event, can not be in [[Causality (physics)|direct cause-effect relationship]]. Such collections of events are perceived differently by different observers. Instead, when focusing on "now" as the events [[perception|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 [[Causality (physics)|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.<ref>{{Cite book|last1=Rovelli |first1=Carlo |author-link1=Carlo Rovelli |title=The order of time|others=Segre, Erica; Carnell, Simon (translation) |date=8 May 2018|isbn=978-0-7352-1610-5|location=New York|oclc=1020300173}}</ref> 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"''.<ref>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", <!--p. 193--></ref><ref>{{cite web |url = http://speakingoffaith.publicradio.org/programs/einsteinsgod/unheardcuts.shtml |title = Einstein's God (NPR) |archive-url = https://web.archive.org/web/20080105183119/http://speakingoffaith.publicradio.org/programs/einsteinsgod/unheardcuts.shtml |archive-date = 5 January 2008 |access-date = 31 March 2018 |work = [[Speaking of Faith]] |last = Tippett |first = Krista |author-link = Krista Tippett |publisher = [[American Public Media]] }}</ref>
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