Time travel is the ability to move forward or backwards through time, at will. Doing this would make the person or entity involved, a time traveler. There are many different theories on how one might move through time, however science pretty much rules out the means to do so. While time travel is one of the staples of science fiction, one of the biggest problems with time travel is often overlooked. And that is the motion of matter through space, over time. For example, if a time traveler wanted to travel to this time yesterday, he or she must also take into consideration the point on the Earth's surface movement through space. Since yesterday, the Earth has rotated on its axis, has moved around the sun, has rotated around the center of the galaxy and so on. If a time traveler does not account for this motion, they will end up in empty space.
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