Arrow of Time











The Arrow of Time, or Time's Arrow, is a concept developed in 1927 by the British astronomer Arthur Eddington involving the "one-way direction" or "asymmetry" of time. This direction, according to Eddington, can be determined by studying the organization of atoms, molecules, and bodies, might be drawn upon a four-dimensional relativistic map of the world ("a solid block of paper").

Physical processes at the microscopic level are believed to be either entirely or mostly time-symmetric: if the direction of time were to reverse, the theoretical statements that describe them would remain true. Yet at the macroscopic level[when defined as?] it often appears that this is not the case: there is an obvious direction (or flow) of time.

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In the News ...





Arrow of time: New understanding of causality, free choice, and why we remember the past but not the future   Science Daily - July 28, 2015

Theoretical physicists have developed a fully-symmetric formulation of quantum theory which establishes an exact link between asymmetry and the fact that we can remember the past but not the future. The laws of classical mechanics are independent of the direction of time, but whether the same is true in quantum mechanics has been a subject of debate. While it is agreed that the laws that govern isolated quantum systems are time-symmetric, measurement changes the state of a system according to rules that only appear to hold forward in time, and there is difference in opinion about the interpretation of this effect. Now theoretical physicists have developed a fully time-symmetric formulation of quantum theory which establishes an exact link between this asymmetry and the fact that we can remember the past but not the future -- a phenomenon that physicist Stephen Hawking has named the "psychological" arrow of time. The laws of classical mechanics are independent of the direction of time, but whether the same is true in quantum mechanics has been a subject of debate. While it is agreed that the laws that govern isolated quantum systems are time-symmetric, measurement changes the state of a system according to rules that only appear to hold forward in time, and there is difference in opinion about the interpretation of this effect.




Why Time Can't Go Backward: Physicists Explain   Live Science - December 3, 2014

In a recent study published in the journal Physical Review Letters, a group of theoretical physicists re-investigate the 'Arrow of Time' - a concept that describes the relentless forward march of time - and highlight a different way of looking at how time manifests itself over universal scales. The Arrow of Time, or Time's Arrow, is a concept developed in 1927 by the British astronomer Arthur Eddington involving the "one-way direction" or "asymmetry" of time. This direction, which can be determined, according to Eddington, by studying the organization of atoms, molecules and bodies, might be drawn upon a four-dimensional relativistic map of the world ("a solid block of paper"). Read more ...




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