<!DOCTYPE html><HTML lang="en"> <head><meta charset="utf-8"> <title>Earman (John), Smeenk (Christopher) & Wuthrich (Christian) - Do the Laws of Physics Forbid the Operation of Time Machines (Theo Todman's Book Collection - Paper Abstracts) </title> <link href="../../TheosStyle.css" rel="stylesheet" type="text/css"><link rel="shortcut icon" href="../../TT_ICO.png" /></head> <BODY> <CENTER> <div id="header"><HR><h1>Theo Todman's Web Page - Paper Abstracts</h1><HR></div><A name="Top"></A> <TABLE class = "Bridge" WIDTH=950> <tr><th><A HREF = "../../PaperSummaries/PaperSummary_19/PaperSummary_19242.htm">Do the Laws of Physics Forbid the Operation of Time Machines</A></th></tr> <tr><th><A HREF = "../../Authors/E/Author_Earman (John).htm">Earman (John)</a>, <A HREF = "../../Authors/S/Author_Smeenk (Christopher).htm">Smeenk (Christopher)</a> & <A HREF = "../../Authors/W/Author_Wuthrich (Christian).htm">Wuthrich (Christian)</a></th></tr> <tr><th>Source: PhilSci Archive website</th></tr> <tr><th>Paper - Abstract</th></tr> </TABLE> </CENTER> <P><CENTER><TABLE class = "Bridge" WIDTH=600><tr><td><A HREF = "../../PaperSummaries/PaperSummary_19/PaperSummary_19242.htm">Paper Summary</A></td><td><A HREF = "../../PaperSummaries/PaperSummary_19/PaperCitings_19242.htm">Books / Papers Citing this Paper</A></td><td><A HREF="#ColourConventions">Text Colour-Conventions</a></td></tr></TABLE></CENTER></P> <hr><P><FONT COLOR = "0000FF"><U>Author s Abstract</U><FONT COLOR = "800080"><ol type="1"><li>We address the question of whether it is possible to operate a <a name="1"></a><A HREF="../../Notes/Notes_11/Notes_1133.htm">time machine</A><SUP>1</SUP> by manipulating matter and energy so as to manufacture closed timelike curves. This question has received a great deal of attention in the physics literature, with attempts to prove no-go theorems based on classical general relativity and various hybrid theories serving as steps along the way towards quantum gravity. </li><li>Despite the effort put into these no-go theorems, there is no widely accepted definition of a <a name="2"></a><A HREF="../../Notes/Notes_11/Notes_1133.htm">time machine</A><SUP>2</SUP>. We explain the conundrum that must be faced in providing a satisfactory definition and propose a resolution. Roughly, we require that all extensions of the <a name="3"></a><A HREF="../../Notes/Notes_11/Notes_1133.htm">time machine</A><SUP>3</SUP> region contain closed timelike curves; the actions of the <a name="4"></a><A HREF="../../Notes/Notes_11/Notes_1133.htm">time machine</A><SUP>4</SUP> operator are then sufficiently  potent to guarantee that closed timelike curves appear. </li><li>We then review no-go theorems based on classical general relativity, semiclassical quantum gravity, quantum field theory on curved spacetime, and Euclidean quantum gravity. </li><li>Our verdict on the question of our title is that no result of sufficient generality to underwrite a confident  yes has been proven. </li><li>Our review of the no-go results does, however, highlight several foundational problems at the intersection of general relativity and quantum physics that lend substance to the search for an answer. </li></ol> </FONT><BR><U>Contents</U><FONT COLOR = "800080"><ol type="1"><li>Introduction </li><li><a name="5"></a><A HREF="../../Notes/Notes_11/Notes_1133.htm">Time travel</A><SUP>5</SUP> and its paradoxes</li><li>Operating a <a name="6"></a><A HREF="../../Notes/Notes_11/Notes_1133.htm">time machine</A><SUP>6</SUP></li><li>Chronology protection and no-go results for <a name="7"></a><A HREF="../../Notes/Notes_11/Notes_1133.htm">time machines</A><SUP>7</SUP> in classical GTR</li><li>No-go results using semi-classical quantum gravity</li><li>No-go results from quantum field theory on curved spacetime</li><li>No-go results from Euclidean quantum gravity</li><li>Conclusion </li></ol> </FONT><hr><FONT COLOR = "0000FF"><B>Comment: </B><ul type="disc"><li>Recommended by <a name="8"></a>"<A HREF = "../../Abstracts/Abstract_19/Abstract_19191.htm">Richmond (Alasdair) - Time Travel and Philosophy</A>". </li><li>24 July 2006; </li><li>Later version of <a name="9"></a>"<A HREF = "../../Abstracts/Abstract_19/Abstract_19243.htm">Earman (John), Smeenk (Christopher) & Wuthrich (Christian) - Take a Ride on a Time Machine</A>". </li><li>For the full text, follow <a name="W990W"></a><A HREF = "http://philsci-archive.pitt.edu/4240/" TARGET = "_top">Link</A>. </li></ul><BR><FONT COLOR = "0000FF"><HR></P><a name="ColourConventions"></a><p><b>Text Colour Conventions (see <A HREF="../../Notes/Notes_10/Notes_1025.htm">disclaimer</a>)</b></p><OL TYPE="1"><LI><FONT COLOR = "0000FF">Blue</FONT>: Text by me; &copy; Theo Todman, 2018</li><LI><FONT COLOR = "800080">Mauve</FONT>: Text by correspondent(s) or other author(s); &copy; the author(s)</li></OL> <BR><HR><BR><CENTER> <TABLE class = "Bridge" WIDTH=950> <TR><TD WIDTH="30%">&copy; Theo Todman, June 2007 - August 2018.</TD> <TD WIDTH="40%">Please address any comments on this page to <A HREF="mailto:theo@theotodman.com">theo@theotodman.com</A>.</TD> <TD WIDTH="30%">File output: <time datetime="2018-08-02T09:03" pubdate>02/08/2018 09:03:33</time> <br><A HREF="../../Notes/Notes_10/Notes_1010.htm">Website Maintenance Dashboard</A></TD></TR> <TD WIDTH="30%"><A HREF="#Top">Return to Top of this Page</A></TD> <TD WIDTH="40%"><A HREF="../../Notes/Notes_11/Notes_1140.htm">Return to Theo Todman's Philosophy Page</A></TD> <TD WIDTH="30%"><A HREF="../../index.htm">Return to Theo Todman's Home Page</A></TD> </TR></TABLE></CENTER><HR> </BODY> </HTML>