Abstract
Irrespective of local conditions imposed on the metric, any extendible spacetime U has a maximal extension containing no closed causal curves outside the chronological past of U. We prove this fact and interpret it as impossibility (in classical general relativity) of the time machines insofar as the latter are defined to be causality-violating regions created by human beings (as opposed to those appearing spontaneously).
Access this article
The computer you are using is not registered by an institution with a subscription to this article. Please choose one of the options below.