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What is Time? Implications in Physical Modelling and Numerical Analysis

This talk examines the human concept of 'time' from a multitude of points of consideration - philosophy, perception of time and neurology, mathematics....
When Jun 18, 2014
from 07:45 PM to 09:00 PM
Where Friends Meeting House, Jesus Lane, Cambridge
Contact Name
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Vassilis S. Vassiliadis, Ph.D., DIC, Dipl. (M.Eng.) NTUA,

Senior Lecturer, Department of Chemical Engineering and Biotechnology, University of Cambridge.


Time is the central theme of this talk, as a perceptual and philosophical concept to its implications in our understanding of fundamental physical laws.  From Antiphon the Sophist to St. Augustin, to Albert Einstein and modern established physics, to speculative ideas such as digital physics, a narrative is built to illustrate why in the end the very concept of time is as elusive as it is paramount in our understanding of Nature.  To paraphrase the words of the physicist John Wheeler, “understanding what time is, is to understand what existence is”. The speculative element presented is the ideas associated with “digital physics” as a paradigm that is shown to resolve the circularity in definitions associated with what time is — if the ideas it puts forward are correct.  Although the paradigm is by far not proven yet, it is nonetheless demonstrated that similar ideas either motivated its inception or exist in the domain of numerical calculations associated with dynamical phenomena (i.e. time-changing systems, as for example associated with the motion of planets, chemical reactions, radioactive decay, etc.).  Basic algorithms are explained and highlighted via numerous figures obtained from computational examples, chosen for their particular way of treating time.  In these, time is either a directly quantised property, or it arises out of some form of quantisation associated with the modelling of time-changing systems.   Traditional computational methods, similar to traditional physics, consider time as some totally decoupled coordinating parameter that ‘flows’ independently as a property underlying physical reality.  The parallel between theoretical concepts and numerical practice is one of the aims of this presentation.  As far as numerical computations are concerned it is discussed that this approach leads to phenomenal performance enhancements in computational algorithms.  The talk is split in three major parts.  The first part is largely a conceptual presentation of key ideas in modern physics in a simplified manner.  The second part presents the ideas forming the foundation of computational algorithms that do not treat time as an independent parameter to simulate the evolution of dynamical systems.  Although some mathematical concepts are inevitably contained in this part, it is largely made up of simple explanations and a large number of results from computational simulations.  The final third part is a speculative discussion of the idea of “parallel timelines”.  This part contains some more advanced mathematical manipulations (equations and algebra!) but it can be either summarised very briefly or described qualitatively.

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