"Traveling through hyperspace ain't like dusting crops, boy!"
- Han Solo
Subspace, Hyperspace, Ultraspace, Infraspace, Warpspace, Jumpspace, Otherspace (and probably several other words that end with "space") are all terms used for a speculative fiction trope relating to spacecraft. The concept is related to FTL, spacetime, and the Fourth Dimension. Most commonly, subspace or hyperspace is used as another dimension that a starship may travel into or through, usually to speed up a journey between the stars.
Beyond that, however, the various depictions of these otherspaces diverge heavily:
- Sometimes a setting will have more than one form of subspace or hyperspace. In such cases, one (subspace, usually) is used for FTL communication, and the other (hyperspace) for FTL Travel.
- Some versions of hyperspace have different laws of physics than normal space, such as not obeying Relativity or removing the limit it imposes of not being able to move at or beyond the speed of light. In other words, within hyperspace, you can just accelerate continuously, and there's no time dilation.
- Some versions of hyperspace are connected to real space in a complicated way, with bizarre topology like a wormhole. Instead of moving faster than light, you move at normal speeds. It's just that while two points are millions of miles away in real space, they're connected by a hyperspace corridor that's only a couple of yards long.
- Some versions of hyperspace are depicted as an empty void, either featureless darkness or just a place of swirling colors.
- Some versions of hyperspace assume it has it's own form of life or interstellar terrain, to make travel exciting.
Old school science fiction writers refer to subspace as "sub-ether"
For the even older school - or for those that like to mix technology and magic - *space and the Astral Plane may (or may not) be the same thing (or closely related).
Game and Story Use
- Hyperspace or Subspace are one way to get FTL in your setting without completely throwing Relativity and Physics out the window. Einstein was right - about our layer of reality. You can't go faster than light, unless you slip outside our spacetime completely. This also allows for FTL travel without all the ugly causality problems.
- In general, hyperspace can justify all sorts of negative space wedgies.
- Hyperspace could be the current home of the precursors. If a PC manages to Ascend To A Higher Plane Of Existence, he's essentially learned how to travel (and survive) in hyperspace without a spaceship.
- Hyperspace could be the point-of-origin of an alien race. Perhaps a space war or alien invasion started once hyperspace became cheaply accessible. We were just using it as a shortcut through space, but to the aliens it seemed like we'd invaded their reality.
- For that matter, creatures from hyperspace or another dimension might use our "real"space in much the same way we use their hyperspace. Being multiply connected spaces, we can take shortcuts through their reality, and they can take shortcuts through ours. This may lead to traffic jams or other complications.
- Certain types of Swirly Energy Thingy only appear in hyperspace, or at least get started there.