Its currantly believed that wormholes are made of quantum foam, which consists of a boiling sea of virtual particles constantly appearing and disappearing at the sub-atomic level of space. Within the quantum foam it is believed that its full of wormholes connecting differant parts of space together. They may also connect different parallel worlds or universes together.
The drawback is their very small size, to small for particles to go through. Scientists at Caltech came up with the idea of using a strange type of matter called exotic matter to hold a wormhole open so a machine or device can travel through the wormhole to another point in space or even in time. Another drawback is the energy needed to hold open a wormhole would be extremely high.
The term wormhole has also been used to discribe a possible zone of transition in the centre of a rotating black hole.
Your have a job ordering a wormhole but you can get some good books with info on wormholes, from bookstores, via mail order.
Blackholes and timewarps by Kip S.Thorne.
Has a chapter on wormholes and overcoming the Average Weak Energy Condition (AWEC), etc.
Time: A traveller's guide by Clifford A Pickover.
You can also check out the Stardrive website at www.stardrive.org. On the main page is a paper on wormholes, timetravel and hyperspace,etc. Its in pdf format.
It is my contention that wormholes have not even been discovered yet. I know this because we still have lots of trash, toxic waste and diet soda all over the place. Now, doesn't it stand to reason that if ANYBODY had ever come up with a functioning wormhole they would have already opened up the worlds most profitable land-fill? (click here for speedy HyperDump service!)
Like you said wormholes have not yet been discovered yet. This does not prove wormholes do not exist. No one has yet developed the means to actually observe one up close and personal.
Wormholes currantly exist at present as mathematical equations within GR theory and quantum theory.
Even if travellers in the future were using wormholes to travel back in time to our present. They may witness a seeing a wormhole, we in our present moment in time would witness unexplained phenomenon.
So if wormhole did suddenly appear most people would not report seeing a wormhole, they would report seeing something strange and unknown!.
Cause no one at present has actually seen a wormhole up close and personal. (That's if wormholes do actually exist. And I think they do)
Ok fine, Tom, I commend you for blowing it in the final few seconds.
Give your ego a banana and a pat on the back. It always works for me. And 'wormhole' is STILL lousy terminoligy (when not referring to the noble quest of fish bait that is). If we can time travel by the use of wormholes, immagine what we could do with the worms themselves!