Lorentzian wormholes are essentially short-cuts through space and time. They are mainly studied by experts in Einstein gravity, and if they exist in real life would be more-or-less similar to the wormhole on Star Trek: Deep Space 9. (But remember, the show is just entertainment, so don't try to extract detailed physics from DS9; at best it will give you a vague general idea of what is going on.)
The good news about Lorentzian wormholes is that, after about ten years of hard work, we cannot prove that they do not exist. The bad news is that they are very strange objects: If they exist at all they need large amounts of negative mass to hold them open and stop them from collapsing. (Negative mass is not anti-matter, it's a region where the energy of the universe is less than that of ordinary vacuum---definitely weird stuff.) We can get small amounts of negative energy in the laboratory (the Casimir effect), but getting the large amounts needed to hold a decent size Lorentzian wormhole open looks to be hopeless with current technologies. (And there may be deep issues of principle preventing us from collecting a lot of negative energy in one place.)
If Lorentzian wormholes do exist, then it seems classically to be relatively easy to turn them into time machines. This embarrassing feature has led Stephen Hawking to promulgate his Chronology Protection Conjecture. According to this conjecture, quantum effects will conspire to effectively prevent time travel even when it looks like classical physics might allow time travel to occur.
Euclidean wormholes are even stranger: they live in "imaginary time" and are intrinsically virtual quantum mechanical processes. These Euclidean wormholes are of interest mainly to the particle physicists (quantum field theorists). You cannot give them a nice classical interpretation in terms of a well-behaved classical gravitational field, and unfortunately have to know a lot of quantum physics to appreciate even their basic properties.
A good popular level description of Lorentzian wormholes can be found in the book Black Holes and Time Warps: Einstein's Outrageous Legacy by Kip. S. Thorne (Norton, New York, 1994).
The BBC has a documentary in the Horizon series: The Time Lords, Judith Bunting, December 2, 1996.
If you know some differential geometry, some general relativity and some quantum field theory (not for the faint of heart), you might want to take a look at Lorentzian Wormholes: from Einstein to Hawking by Matt Visser (AIP Press, New York, 1995).
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Add CommentThe past has already been created, so if you killed your grandfather, all it would create is a hole in time and the rest of the timeline would continue as it was. Also, just because Physics doesn't know how to control a wormhole doesn't mean it can't be done---only that, at the present time, Physics it too stupid to know how. If control of a wormhole is the only drawback to riding your skateboard along the length of it, it is highlly unlikely that, at some future time, someone won't shoot the worm, much as the do rapids, nowadays.
Reply | Report Abuse | Link to thisthe paradox is that if you kill your grandfather then your father is not born then you are not born and cant go back and kill your grandfather, thus a fatal paradox. But there is alot in what you say that i do agree with.
Reply | Report Abuse | Link to thisIf we can create a wormhole SAFELY then there is no reason not to experiment with it, however as i have stated elsewere, we as a species are too arrogent to do such a thing SAFLY. we think that just becouse we can do it it will not rip space time to shreds. It would be theoretically possable to "empty" space of emergy to facilitate the negative mass energy migrating to that point, howevere there is a lot to be said about "poking sticks at wild bears".
hello, this is a very interesting topicof mine..
Reply | Report Abuse | Link to thisthus i request to all those who know any thing about wormhole, then please send me to my e-mail
bikash9090@gmail.com
I would simply disagree with that paradox effect. In some points, what I understand is that dimension and time are two different scenarios whereas dimension is a parallel in space but not time. Wormhole if true can make us travel multi-parallel dimension connection in two different points in time. It means that once you travel through the wormhole you will be in another dimension of space and time, and if it is possible to transport physical objects or body through that wormhole, that object/body will not effect the state of time and events because of the two-dimensional world scenario. If you kill your grandfather in another space and time that will not cause an effect to the dimension where you came from. cheers! :)
Reply | Report Abuse | Link to thisI would simply disagree with that paradox effect. In some points, what I understand is that dimension and time are two different scenarios whereas dimension is a parallel in space but not time. Wormhole if true can make us travel multi-parallel dimension connection in two different points in time. It means that once you travel through the wormhole you will be in another dimension of space and time, and if it is possible to transport physical objects or body through that wormhole, that object/body will not effect the state of time and events because of the two-dimensional world scenario. If you kill your grandfather in another space and time that will not cause an effect to the dimension where you came from. cheers! :)
Reply | Report Abuse | Link to thisWormholes are made of dark matter particles that cannot be consumed by black holes and do not interact with normal matter except by being gravitational reverse black holes called white holes. No evidence refutes this, even scientists want to claim that dark matter is intemediate or millimeter sized black holes which would collide explode radiate if so densely packed into clumpy galactic halos around visible matter. Check out the latest news and theories at www.quantauniverse.com
Reply | Report Abuse | Link to thisI've always felt this paradox is more a function of our egos. After all, unless I am mistaken (which happens often in science!) particles from the past are constantly showing up in the present to "kill" other particles, some of which might be their future selves. To the universe, we are just a collection of such particles so why couldn't that collection go back and kill the collection it came from?
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