The "Time Travel" article from The Internet Encyclopedia of Philosophy opens with a general definition of time travel as well as a basic discussion of the philosophy and physics of time. Then it takes a careful look at the physics and causation involved in time travel. It covers the grandfather paradox, causal loops and personal identity.

The "Time Traveler" page at the companion site to NOVA's "Einstein's Big Idea" episode focuses on Einstein’s theory of relativity and how that plays into the possibility of time travel, explaining how time is affected by relative motion. Time dilation is explained. The twin paradox described as an effect of time dilation.

"How Time Travel Will Work" provides a general overview of time travel. It starts by looking at time and then moves to the physics of time travel with simple descriptions of black holes, wormholes, cosmic strings and some of the paradoxes. This article has built-in links to other articles explaining all the topics in more depth; there is also a list of additional links to other time-travel sites.

The "Time Travel and Modern Physics" article from The Stanford Encyclopedia of Philosophy presents a scientifically informed, technical discussion of models for time travel. The primary issue is whether there must be surprising constraints on behavior to prevent what has already happened from being made not to have happened. The discussion bears on auto-infanticide, the grandfather paradox, and bilking arguments.

"Time Machines" is another scientifically informed, technical article from The Stanford Encyclopedia of Philosophy. This one focuses on the physical possibility of time machines that alter space-time structure to permit closed time-like curves. The focus is on no-go theorems from the physics literature; these are attempts to show “that, under physically plausible assumptions, the operation of a time machine is impossible.”