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The idea of a hyperdrive in most science fiction relies on the existence of a separate and adjacent dimension most commonly called "hyperspace," though various other names have been used. When activated, the hyperdrive shunts the starship into what appears to be another dimension, where it can cover vast distances in an amount of time greatly reduced from the time it would take in "real" space. Once it reaches the point in hyperspace that corresponds to its destination in real space, it re-emerges. Usually, hyperdrive refers to a method of travel in which it takes a measurable amount of time to go from one point to another. When the distance is covered instantaneously, the term jump drive is often used.
Fictional explanations of why ships can travel faster than light in hyperspace often accompany the storyline of novels, television programs, and films in which they are featured. Distances in hyperspace may be smaller than or geometrically inverse in relation to real space; it may provide a shortcut between two points in real space, thus effectively increasing the ship's speed by reducing distance travelled rather than time taken; perhaps the speed of light in hyperspace is not a speed barrier as it is in real space. Whatever the reasoning, the general effect is that ships traveling in hyperspace seem to have broken the speed of light, appearing at their destinations much more quickly and without the time dilation predicted by the Special Theory of Relativity.
While in hyperspace, spaceships are typically isolated from the normal universe; they cannot communicate with, nor perceive things in real space until they emerge. Often there can be no interaction between two ships even when both are in hyperspace. To people traveling in hyperspace, time typically moves at its normal pace, with little or no time dilation; 24 hours in hyperspace equates to 24 hours in real space. This is due to the fact that typical hyperdrive scenarios involve only changing the position of the craft, without altering its velocity (i.e. a ship will emerge with the same momentum, kinetic energy and direction of travel that it had upon entering hyperspace, thereby avoiding relativistic effects). One exception is David Brin's Uplift Universe; here, hyperspace is divided into "levels" where time passes at different rates. Hyperspace, itself, may be portrayed as swirling colors, rapid-moving stars or as something that would drive a human mind insane if viewed by the naked eye.
In most science fiction, hyperdrive jumps require a considerable amount of planning and calculation, with any error carrying a threat of dire consequences. Therefore, jumps may cover a much shorter distance than would actually be possible so that the navigator can stop to "look around": take his bearings, plot his position, and plan the next jump. The time it takes to travel in hyperspace also varies. Travel times may be in hours, days, weeks or more, and in those cases can provide a setting in itself for a story that takes place during an extremely long journey.
In Star Wars, hyperspace travel is portrayed as potentially dangerous due to the chance that the route through hyperspace may take the ship too close to a celestial body with a large gravitational field, such as a star, or a black hole. In such scenarios, if a starship passes too close to a large gravitational field while in hyperspace, the ship is forcibly pulled out of hyperspace and reverts to normal space, or in some stories, is destroyed. Therefore, certain hyperspace "routes" may be mapped out that are safe, not passing too close to stars or other dangers. Other science fiction have hyperspace travel occur outside of normal space, such as in subspace in Stargate SG-1.