As far as I know,
Saxton claims, that hyperspace is realspace above light speed. (There is no evidence in the movies or somewhere else for this claim, as far as I know.)
The special theory of relativity shows, that it is impossible to reach light speed in real space. But as a mathematical equation, it shows, that theoretical it is possible to have a speed above light speed as long as you never are as fast as light speed.
That's where the idea of tachyons
[1] descend from. The tachyons are quasi mirror particles of known sublight particels [baryons] with contrariwise properties. (For example, they would have only an imaginary rest mass, because per definition, they have to move with speed above light speed. That means, that their mass to the second is negative. But physical values like energy and momentum have to have real values. Furthermore they move in time back and not forward. If you would send a message with tachyons, you would get it, before you have sended it.)
The problem is, that there is no evidence, that tachyonen exist. They are only a mathematical result.
But sometimes mathematics doesn't makes sense.
For example:
You know the Pythagoras' theorem: The sum of the areas of the two squares on the legs (a and b) equals the area of the square on the hypotenuse (c) or better known as a²+b²=c². If you want to know, how long c is, you have to extract the square root of a²+b². The problem is, that you get two solutions, the positive root and the negative root. But the hypotenuse of your triangle can only have a positive length. The negative solution is a mathematical solution, but it doesn't makes sense.
In calculus of probabilities, with different equations, you get sometimes different results. Mathematical, they are all correct. But obviously, only one result can describe the reality, the probability of the implementation of an event.
There are enough other examples, in which mathematics provides one with values, which don't make sense.
Bertrand Russell wrote:Thus mathematics may be defined as the subject in which we never know what we are talking about, nor whether what we are saying is true.
With tachyons, it could be the same. They are mathematical possible but don't really exist. At least, there is no evidence for them although many tests were made to prove their existence. All have failed.
To date, the existence of tachyons has been neither confirmed nor explicitly ruled out. The latter could turn out to be impossible because that would be a negative evidence. But the absence of a proof is never a proof for absence!
Insofar, the explaination of Saxton, which is build allone on one possible result of the special theory of relativity, is nothing more than a speculation.
- And even if it is assumed, that there are tachyons, the theory of Saxton lacks every attempt of a sientifical explanation, how a ship would accelerate to a speed above light speed without passing light speed.
Saxton at theforce.net wrote:For common starships, the jump to hyperspace involves a brief but violent acceleration to high relativistic speeds and then a leap beyond the lightspeed threshold
by some unknown mechanism.
[...]
A starship can exist comfortably above or below lightspeed but cannot pass through lightspeed via ordinary physical means. However all of ordinary physical existence becomes imprecisely defined below a certain subatomic scale, and
we can speculate that this may have something to do with the super-technology that permits hyperdrive in STAR WARS. The leap beyond the lightspeed
may be an event which exploits some kind of quantum-mechanical effect in order to slip from subluminal to superluminal speed without ever being at intermediate speeds. As seen by an external observer, the jump must be accomplished within Plank time, a tiny time unit below which time itself becomes meaningless.
- That's nothing but pseudo-science. To an illiterate person, it sounds good, especially because there are some truths in it. But it explains really nothing.
That is not more scientifical, than the warp drive, if not even less scientifical.
The
string theories claim, that our universe has
several dimensions and that
parallel to our universe are unlimited other universes with other physical laws. You could call these dimensions or the other universes subspace. Fact is, that Gene Roddenberry was more concerned about the physical realizability of the warp drive, than George Lucas about the hyperdrive.