Time Travel, courtesy of Peter David

In H.G. Wells' novel The Time Machine, Wells makes a big fuss over the fact that the time machine travels through time but not space.

Yesterday at the comic book convention, Peter David pointed out the fundamental flaw with that premise, and it is not with the physics. There are a few theories that could permit time travel, and at least one of them backs up the travel-through-time-but-not-space scenario. The problem is that space doesn't give a rodent's rear end about our quaint little system of latitude and longitude. As time passes, the Earth revolves around the sun (and, I might add, the entire solar system revolves around the center of the galaxy, which is itself hurtling through the universe). If the Time Traveler moved through time but not space, the odds of him reappearing anywhere near the surface of any planet at all are at best astronomical, and good luck timing the trip so he'd reappear on the 25-30% of Earth's surface that isn't water. The odds get even worse yet if our time traveller would want to avoid reappearing in the carpool lane during rush hour.

There are, of course, theories of time travel that require travel through space. These have their own problems, principally that they are one-way trips and you run a very real risk of being torn apart by gravitational forces and sucked atom-by-atom into a black hole. Still, since there is a spacecraft, presumably with life support, involved, the odds are a lot better than the time-but-not-space-travel machines, HOV lane or no.