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15 - Can we change the past?

Published online by Cambridge University Press:  04 May 2010

Igor D. Novikov
Translated by
Vitaly Kisin
Igor D. Novikov
Affiliation:
University of Copenhagen
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Summary

‘I'm not kidding you at all, Phil,’ Barney insisted. ‘I have produced a workable Time Machine, and I am going to use it to go back and kill my grandfather.’

‘A Gun for Grandfather’ by F. M. Busby in Getting Home, (New York: Ace) 1987

I found this epigraph in Paul Nahin's book Time Machines (New York: AIP) published in 1993 and kindly mailed to me. Another quotation from this book that impressed me with its precision of analysis is:

Time travel is so dangerous it makes H–bombs perfectly safe gifts for children and imbeciles. I mean, what's the worst that can happen with a nuclear weapon? A few million people die: trivial. With time travel we can destroy the whole Universe, or so the theory goes.

Millennium Varley, 1983

Indeed, if a chance to visit the past is available, it seems that by modifying this past we could modify the lot of some individuals, the fate of mankind or even the evolution of the entire Universe. Is this true?

The argument that is especially popular in debates of this sort is the so–called ‘grandfather paradox’. It goes roughly like this: ‘If I could go back into the past in which my grandfather was very young, I could kill him and thereby make my own birth impossible’. Or another version of the same paradox: ‘I return into my own past, meet myself in my youth and kill my younger version.’

In both cases this unnatural homicide generates complete nonsense. Should we infer that such an event is impossible? But why? I have my ‘free will’, don't I? Hence I can realize this ‘free will’, at least in principle.

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The River of Time , pp. 251 - 264
Publisher: Cambridge University Press
Print publication year: 2001

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