& Time Travel
In his Theory of Relativity,
Einstein proposed--and later proved--that time and space cannot be separated.
Therefore, a time traveler must really be a time-and-space traveler.
Imagine, as writer John Gribbin did
in his book Timewarps, that a time traveler decides to go half a year
backward in time to the same location. He steps into a time machine, adjusts the
controls to the right day and time, activates the machine, makes the trip, and
steps out of the machine.
Where will the time traveler find
Gribbin answers the question by
saying that the time traveler will step into "empty space--since six months
ago the Earth was on the other side of the Sun in its year-long orbit! A time
machine must also be a space machine if our hero is to get anywhere he
H. G. Wells's time
machine never considers the relationship of space to time travel either.