Time travel and coincidence-free local dynamical theories
- PDF / 671,176 Bytes
- 12 Pages / 439.37 x 666.142 pts Page_size
- 87 Downloads / 186 Views
Time travel and coincidence-free local dynamical theories Giuliano Torrengo1
Received: 26 September 2014 / Accepted: 2 May 2017 © Springer Science+Business Media Dordrecht 2017
Abstract I criticize Lockwood’s solution to the “paradoxes” of time travel, thus endorsing Lewis’s more conservative position. Lockwood argues that only in the context of a 5D space-time-actuality manifold is the possibility of time travel compatible with the Autonomy Principle (according to which global constraints cannot override what is physically possible locally). I argue that shifting from 4D space-time to 5D space-time-actuality does not change the situation with respect to the Autonomy Principle, since the shift does not allow us to have a coincidence-free local dynamical theory. Keywords Time travel · Wormoholes · Multiverse
1 The paradoxical train: local and global constraints In his book The Labyrinth of Time, Michael Lockwood has argued that the possibility of time travel poses a threat to the Autonomy Principle: (AUTONOMY) Any configuration of matter and energy that is locally consistent with the laws of physics is also globally consistent with these laws.1 If AUTONOMY holds, configurations of matter and energy that are allowed by the laws of physics, given their immediate surroundings, cannot turn out to be impossible given the way in which matter and energy are globally distributed. For instance, if we buy a functioning electric stove, and we connect it to the power supply, the stove will start to 1 Lockwood (2005: p. 172 and p. 327). See also Deutsch and Lockwood (1994: p. 71).
B 1
Giuliano Torrengo [email protected] Università degli Studi di Milano, Milan, Italy
123
Synthese
produce heat, regardless of what is happening in other areas of the universe. Of course, something in the surroundings of the stove may hinder its normal functioning: a high level of air humidity might damage some essential part of its circuits, say. But what happens far away from its surroundings—on the Moon or on Mars—cannot constrain the way the stove works. The idea underlying the AUTONOMY is that global constraints are just the result of “adding up” local ones, and thus cannot override local possibilities. As Lockwood points out, AUTONOMY is not only very intuitive, but it underlies common experimental practices in science: “[w]e normally regard it as a live option to set up our apparatus in any state allowed by physical law, and assume that we can rely upon the rest of the universe to take care of itself” (Lockwood 2005: p. 172). However, in time travel scenarios AUTONOMY is no longer secured.2 A time travel scenario is one in which the space-time manifold is curved in such a way as to encompass closed time-like curves (CTC). A moving object or a light signal that follows a CTC can start at a spacetime point with temporal coordinate t’ and reach a point with temporal coordinate t that temporally precedes t’, without ever going faster than light. In such scenarios, backwards causation is allowed: an event c can be the cause of anot
Data Loading...
