Along with parallel universes, wormholes are an extreme oddity whose existence is stated by relativity. But unlike parallel universes, there are no observations or vague experiments to give us proof that they're out there.

A wormhole is, simply, a turnnel through space-two 'mouths' connected by a throat. The mouths would be like black holes minus the singularity at the center so one could pass through. As for the structure of the tunnel... well, this is all theoretical. However, it is known that space-time behaves differently in a wormhole, so whether a wormhole looks like the longer path or not, it is the shortest distance between two points.

Wormholes sound like a great way for us to boost our space exploration program, but if they do exist, there's a major problem-they're sub-mircoscopic. In fact, many physicists theorize that space is made of 'space foam'- an unstable web of constantly appearing and disappearing wormholes. What would it take to make a wormhole travelable?

First of all, it would have to be enlarged and stabilized. To do this, we'd need to find a way to 'stretch space'. Once enlarged, the wormhole would have to be propped open with a so-called 'exotic material' that has an outward tension that equals the pressure at the center of the neutron star. (Recalling that neutron star is what collapses to form a black hole, you can imagine that kinds of pressure.) Then once we have a sizable and stable wormhole, we'd have to find away to move the ends so that they took us where we wanted to go. Obviously a shuttle with a trailer hitch is not going to accomplish this.

Supposing that we could accomplish this, we'd have the setup for the most classic of all science-fiction plots: Time Travel.

To accomplish this, one mouth of the wormhole would have to be accelerated at close to the speed of light until it was the desired amount of time behind the other mouth. (Remember, time moves more slowly as you move faster). If one entered the regular end, you would arrive 'back in time' at the accelerated end.

Time travel has its limits. One cannot travel back beyond the time when the wormhole was created. So to see the dinosaurs, we'd have to find a wormhole built by an ancient civilizatin from another planet.

The best way to see the limitations and possibilities of wormholes is to use the classic puzzel of going back in time to kill a parent before you were born. If you killed your father before you were born, you would not exist, so therefore you couldn't go back and kill him, but you DO exist... it seems like an endless loop. But now tie it in to the parallel universe theory-could a wormhole be a gateway to a parallel universe where you did kill your father? Or if not, how could you kill someone that already exists? If you traveled back in time, wouldn't you just be interacting with light signals?

The scientific community can explain wormholes, but the consequences of them are unknown. Should we ever create a functional one, it will certainly raise many new scientific and moral issues.

Diagram 1 exhibits the classic image of a wormhole in curved space-time. It seems obvious in this way that a wormhole is the shortest distance between points A and B. In diagram 2, it might seem as thought the wormhole would be longer, but space-time behaves differently in wormholes, so it would be the shortest distance, not the straight line.