Can We Know the Global Structure of Spacetime?

Here, we briefly review the notion of observational indistinguishability within the context of classical general relativity. We settle a conjecture given by Malament (1977) concerning the subject and then strengthen the result considerably. The upshot is this: There seems to be a robust sense in which the global structure of every cosmological model is underdetermined

Global Spacetime Structure

Here, we outline the basic structure of relativistic spacetime and record a number of facts. We then consider a distinction between local and global spacetime properties and provide important examples of each. We also examine two clusters of global properties and question which of them should be regarded as physically reasonable. The properties concern "singularities" and "time travel" and are therefore of some philosophical interest

On the Inextendibility of Spacetime

It has been argued that spacetime must be inextendible – that it must be “as large as it can be” in some sense. Here, we register some skepticism with respect to this position

Malament-Hogarth Machines

We show a clear sense in which general relativity allows for a type of "machine" which can bring about a spacetime structure suitable for the implementation of "supertasks.

Global Spacetime Structure

Here, we outline the basic structure of relativistic spacetime and record a number of facts. We then consider a distinction between local and global spacetime properties and provide important examples of each. We also examine two clusters of global properties and question which of them should be regarded as physically reasonable. The properties concern "singularities" and "time travel" and are therefore of some philosophical interest

Malament-Hogarth Machines

We show a clear sense in which general relativity allows for a type of "machine" which can bring about a spacetime structure suitable for the implementation of "supertasks.

On the Inextendibility of Spacetime

It has been argued that spacetime must be inextendible – that it must be “as large as it can be” in some sense. Here, we register some skepticism with respect to this position

Global spacetime structure

Here, we outline the basic structure of relativistic spacetime and record a number of facts. We then consider a distinction between local and global spacetime properties and provide important examples of each. We also examine two clusters of global properties and question which of them should be regarded as physically reasonable. The properties concern "singularities" and "time travel" and are therefore of some philosophical interest