A bit of a problem that faced the sci-fi writers was the fact that other worlds around other stars were distant. Extremely distant. In fact, to quote Douglas Adams "You may think that it's a long walk down the road to the chemist, but that's peanuts compared to space."
However, Einstein, the eternal pessimist he was, stated in his many wonderful papers that any object with mass could ever reach c -- the speed of light, meaning a trip to the nearest star, Proxima Centauri (at about 4 light years away) would take at least 4 years to acomplish. Then along comes the lovely concept of time dilation which states that the rate that time beats within a space craft is variable depending on the speed that the craft is travelling at. For example, a trip to a star could seem to take a few years to the crew of the ship, but would seem to take a few thousand years to the people on Earth.
Of course, these little ideas have a plethora of sci-fi potential of their own -- something that was hinted at in Planet of the Apes. Whether Earth is destined to be taken over by apes remains to be seen, but Einstein's theories did stir the creative juices of many writers, and the race to beat Relativity, not in practice, but in the imagination, was on.
And so, those lovely star drives that now bless so many sci-fi stories were invented. And here are a few that we've come across in our voyages across the galaxy:
Probably the most famous star drive is Star Trek's warp drive. The load of technical information that the people responsible for Star Trek have churned out over the years, give us a fantastic insight into 23rd century science. Stuff such as subspace fields and inertial dampers decorate the many series and films give it that extra bit of realism.
The warp drive itself employs 'warp fields' to propell the Starships Enterprise and Voyager along their paths through the galaxy. In the warp engine, the 'warp plasma' travels through the fictional material 'verterium cortenide'. This manages to change the geometry of space around the warp nacells and this warping of space propells the starship along.
I'm not sure how much of this idea was actually borrowed from Miguel Alcubierre's idea, and how much of Miguel Alcubierre's idea was borrowed from Star Trek. Alcubierre proposed the idea of a 'warp drive' as a semi-realistic means of Faster Than Light propulsion in his paper "The Warp Drive: Hyper fast travel within General Relativity" to the "Classical and Quantum Gravity" journal.
The idea is similar to Star Trek's in that it creates distortions in space around the space craft. At the front of the ship, space is contracted to bring whatever is ahead of the ship closer, and space behind the ship is expanded to put whatever is behind, further behind. The ship remains in exactly the same spot with respect the the space immediately surrounding it, and so the crew of the ship feel no acceleration forces and do not experience time dilation.
Alcubierre's idea fits in with all of Star Trek's dreams -- Faster Than Light propulsion (ie. popping back and to between stars in a matter of hours rather than centuries), no effects from time dilation (the clocks on board the ship remain synchronised with the clocks back on Earth.), and, maybe the best thing, a cool sounding name.
Too good to be true? I'm afraid so. Alcubierre's idea needs large amounts of 'negative' energy in order to work. Negative energy is required to 'warp' the space in a certain way. And the idea requires space to be warped a lot, so a lot a negative energy is required. Negative energy isn't available on demand -- it's not even known how to get any negative energy.
Shame really....
I think that the name "hyperdrive" was fixed to a means of FTL propulsion in stories that didn't rely to heavily on their technology. The prime aims of Star Wars, for example, was just to be a huge wad of great fun. I don't think George Lucas ever intended for the films' background to be embedded in real world science.
But still, like all things in the Star Wars universe, the hyperdrive has been catlogued, and some fictional characteristics have been invented around it.
The Star Wars hyperdrive is just yer basic "shove your ship up to a velocity faster than that of light" drive. When a ship hits the "Big L", (see the Star Wars Encyclopedia for that one -- it just means to reach lightspeed) it jumps out of normal space and enters another "shadow dimension" known as hyperspace.
The Star Wars hyperspace is a dimension similar to the normal universe, but is smaller, allowing distances to be traversed in shorter time. The stars and planets in real space cast dangerous gravity shadows into hyperspace, that need to be avoided lest the unfortunate crew of the space craft be turned into a thinly spread pat�. When the destination is reached in hyperspace, the ship is flung back into real space and the crew of the ship carry on their journey.
Apparantly, "hyperspace" is the name given to whatever lies outside of our universe. Not a lot is known about it, as all information we collect about anything is contained within our own universe.
Another sci-fi favourite, and one that is grounded in "sci-fa" is the concept of wormholes. The idea is that two points in space can be connected by a tunnel. The two points in space may be thousands of light years apart, but the distance through the tunnel may only be a couple of light years.
I find this concept difficult to wrap my head around. It opens up such things as time travel -- when the mouths of the wormhole are moving due to the expansion of the universe, they experience time dilation with respect the the other mouth. In essence, by entering the wormhole, there is a chance you may come out the other side a year ago.
And, from the Back To The Future films, we all know what touble that causes.
I think the idea belongs to Kip Thorn, the famous physicist at Caltech, who sprung the idea when helping Carl Sagan with his novel "Contact". I'm probably mistaken here however.
The idea has the same flaws as Mr Alcubierre's warp drive, in that negative energy is required to keep the mouths of the wormhole open.
The wormhole has been used in sci-fi many times. Probably the most famous wormhole in sci-fi is the Bajoran wormhole in Star Trek -- Deep Space 9. In this wormhole live a race of Prophets who are able to live in all points in time. This suggests that the wormhole tunnel is not real space at all, but maybe the arforementioned hyperspace, where time seems not to exist. Whether this is true or not, I don't know!
What do you think?The Warp Drive
Hyperdrives
Wormholes