  The topic of time machines is the subject of a sizable and growing  physics literature, some of which has filtered down to popular and  semi-popular   presentations.[1]  The issues raised by this topic are largely oblique, if not  orthogonal, to those treated in the philosophical literature on time   travel.[2]  Most significantly, the so-called paradoxes of time travel do not  play a substantial role in the physics literature on time machines.  This literature equates the possibility of time travel with the  existence of closed timelike curves (CTCs) or worldlines for material particles that are smooth, future-directed timelike curves with   self-intersections.[3]  Since time machines designate devices which bring about the existence of CTCs and thus enable time travel, the paradoxes of time travel are irrelevant for attempted “no-go” results for time  machines because these results concern what happens before the  emergence of   CTCs.[4]  This, in our opinion, is fortunate since the paradoxes of time travel are nothing more than a crude way of bringing out the fact that the  application of familiar local laws of relativistic physics to a  spacetime background which contains CTCs typically requires that  consistency constraints on initial data must be met in order for a  local solution of the laws to be extendable to a global solution. The nature and status of these constraints is the subject of ongoing  discussion. We will not try to advance the discussion of this issue   here;[5]  rather, our aim is to acquaint the reader with the issues addressed  in the physics literature on time machines and to connect them with  issues in the philosophy of space and time and, more generally, with  issues in the foundations of physics.