Worm Holes - White Holes
In physics, a wormhole, also known as an Einstein-Rosen bridge (and less commonly as an Einstein-Rosen-Podolsky bridge or Einstein-Podolsky-Rosen bridge), is a hypothetical topological feature of spacetime that is essentially a "shortcut" through space and time.
A wormhole has at least two mouths which are connected to a single throat. Matter can 'travel' from one mouth to the other by passing through the throat.The name "wormhole" comes from the following analogy used to explain the phenomenon: imagine that the universe is the skin of an apple, and a worm is traveling over its surface. The distance from one side of the apple to the other is equal to half the apple's circumference if the worm stays on the apple's surface, but if it instead burrows a wormhole directly through the apple the distance it has to travel is considerably less.
Intra-universe wormholes connect one location of a universe to another location of the same universe. A wormhole should be able to connect distant locations in the universe by bending spacetime, allowing travel between them that is faster than it would take light to make the journey through normal space. See the image above.
Inter-universe wormholes connect one universe with another. This gives rise to the speculation that such wormholes could be used to travel from one parallel universe to another. A wormhole which connects (usually closed) universes is often called a Schwarzschild wormhole.
Another application of a wormhole might be time travel. In that case it is a shortcut from one point in space and time to another. In string theory a wormhole has been envisioned to connect two D-branes, where the mouths are attached to the branes and are connected by a flux tube. Finally, wormholes are believed to be a part of spacetime foam.
There are two main types of wormholes: Lorentzian wormholes and Euclidean wormholes. Lorentzian wormholes are mainly studied in semiclassical gravity and Euclidean wormholes are studied in particle physics. Traversable wormholes are a special kind of Lorentzian wormholes which would allow a human to travel from one side of the wormhole to the other.
Serguei V. Krasnikov tossed the term spacetime shortcut as a more general term for (traversable) wormholes and propulsion systems like the Alcubierre drive and the Krasnikov tube to indicate hyperfast interstellar travel.
It is unknown whether (Lorentzian) wormholes are possible or not within the framework of general relativity. Most known solutions of general relativity which allow for wormholes require the existence of exotic matter, a theoretical substance which has negative energy density. However, it has not been mathematically proven that this is an absolute requirement for wormholes, nor has it been established that exotic matter cannot exist. Recently Amos Ori envisioned a wormhole which allowed time travel, did not require any exotic matter, and satisfied the weak, dominant, and strong energy conditions. Since there is no established theory of quantum gravity, it is impossible to say with any certainty whether wormholes are possible or not within that theoretical framework.
It is unknown whether (Lorentzian) wormholes are possible or not within the framework of general relativity. Most known solutions of general relativity which allow for wormholes require the existence of exotic matter, a theoretical substance which has negative energy density. However, it has not been mathematically proven that this is an absolute requirement for wormholes, nor has it been established that exotic matter cannot exist. Recently Amos Ori envisioned a wormhole which allowed time travel, did not require any exotic matter, and satisfied the weak, dominant, and strong energy conditions. Since there is no established theory of quantum gravity, it is impossible to say with any certainty whether wormholes are possible or not within that theoretical framework.
Lorentzian traversable wormholes would allow travel from one part of the universe to another part of that same universe very quickly or would allow travel from one universe to another universe. Because wormholes not only connect spatial locations they would also allow time travel.
Often there is confusion about the idea that wormholes allow superluminal (faster-than-light) space travel. In fact there is no real superluminal travel involved. Assume that the wormhole connects two remote locations. While traveling through a wormhole subluminal (slower-than-light) speeds can be used. The time in which the distance was traveled would appear faster than it would take light to make the journey through normal space.
A wormhole could potentially allow time travel. This could be accomplished by accelerating one end of the wormhole relative to the other, and then sometime later bringing it back; relativistic time dilation would result in less time having passed for the accelerated wormhole mouth compared to the stationary one, meaning that anything which entered the stationary wormhole mouth would exit the accelerated one at a point in time prior to its entry.
The path through such a wormhole is called a closed timelike curve, and a wormhole with this property is sometimes referred to as a "timehole."It is thought that it may not be possible to convert a wormhole into a time machine in this manner, however; some mathematical models indicate that a feedback loop of virtual particles would circulate through the timehole with ever-increasing intensity, destroying it before any information could be passed through it.
This has been called into question by the suggestion that radiation would disperse after traveling through the wormhole, therefore preventing infinite accumulation. There is also the Roman ring, which is a very stable configuration of more than one wormhole.
This ring allows a closed time loop with stable wormholes. The debate on this matter is described by Kip S. Thorne in the book Black Holes and Time Warps, and will likely require a theory of quantum gravity to resolve.Many physicists, including Stephen Hawking, believe that due to the problems a wormhole would theoretically create, including allowing time travel, that something fundamental in the laws of physics would prohibit them.
However, this remains speculation, and the notion that nature would censor inconvenient objects has already failed in the case of the cosmic censorship principle.
Wormholes known as Schwarzschild wormholes are theoretical bridges between areas of space that are thought to be found in the center of a black hole and white hole, joining two universes. They exist in solutions to Einstein's equations, and are thought to be extremely unstable, and would instantly fall apart once created. Some speculation exists that quasars are actually white holes instead of supermassive black holes.
It is impossible for a traveller to go through this type of wormhole because they can only go through a horizon in one direction. If the traveler is formed of non-exotic matter once they reach the center of the Schwarzschild wormhole then, they can't leave the other side, and they can't leave through where they came since the side they came in though was a black hole, meaning nothing can escape it once inside the Schwarzschild radius.
Wormholes are also a feature of science fiction.
They are a centerpiece of Carl Sagan's novel Contact, for which Kip Thorne advised Sagan on the possibilities of wormholes.
Wormholes are also the principal means of space travel in the Stargate movie and the spin-off television series, Stargate SG-1 and Stargate Atlantis. The central plot device of the programs is a transportation network consisting of the ring-shaped devices known as Stargates, which generate wormholes that allow one-way matter transmission between gates when the correct spatial coordinates are "dialed".
White Holes are the theoretical exact opposite of black
holes, and their existence is implied by a negative square
root solution to the Schwarzchild metric. The Schwarzchild
metric is based on General Relativity, which is time
symmetric. This means that the most technical definition of
white hole is simply a black hole running backwards in time. It
is a location in space time that, instead of being impossible
to escape, is impossible to reach.
Under the definition given by the solution to this equation they repel everything, including massive particles as well as photons, nothing can enter them. We have never discovered a white hole, and given these properties we believe that they would be rather difficult to miss. Furthermore, an object that acts in this manner directly violates the second law of thermodynamics which states that heat naturally flows from a region of high temperature to a region of low temperature.
The contradiction this causes is that any object with heat should eventually dissipate it's heat energy to its surroundings, and a white hole by definition never runs out of heat or mass, thus standing in violation of every other major law of physics we have in order to hold true to the second law of thermodynamics.
This, however, only applies to our universe. The same equations that suggest the existence of white holes also seem to imply that they exist in a universe parallel to our own, and would exist connected to a black hole by way of a worm hole in order to complete the Schwarzchild geometry suggested by the equation which predicted the existence of black holes. This worm hole joining 2 separate universes is known as the Einstein-Rosen bridge and is one of the most fascinating concepts in theoretical physics.
While the concept of this connection is extremely exciting we know very little about it, as we have no white holes to observe and black holes are extremely hard to detect given their light absorbing nature. Given our current understanding of black holes and white holes we are not even sure of such a connection could exist, or if it did, where it would take us. Current knowledge does not even give enough information to suggest if such a link would even be to somewhere else in our own universe.
Unfortunately, current theory does not even allow for the ultimate destination of a worm hole to be much of a worry because it is believed that passing through a worm hole is impossible. Instant death would be a near certainty given any imaginable method of protection, and no matter the circumstances return would be impossible given everything we know about black holes and the way they would interact with white holes.
The only method where death would not be a near certainty is if a worm hole could somehow be stabilized for longer than the brief amount of time under which they are naturally believed to remain stable. This is an impossibility given our current understanding of science and would obviously be grander in scope than anything ever attempted by mankind in the history of Earth.
It is theoretically possible, although highly improbable that a worm hole could somehow be stabilized to allow safe passage through it. The only theoretical way this could be done that I was able to find involves using 'exotic matter', or matter unlike any we know, highly exotic matter. In order to stabilize the worm hole the throat of the singularity would have to be threaded with this matter which would be spherical in nature. The properties this matter would have to have would be negative mass, and yet still be capable of exerting a positive surface pressure.
It must have these two properties for very specific reasons, the negative mass ensures the the throat of the worm hole lies outside the protected region and the positive surface pressure is the property that prevents the throat of the worm hole for collapsing. These properties of matter are not arbitrary or purely theoretical, we have determined this is the type of space-time geometry most likely needed to produce a stable worm hole. Einstein's equations then specify what the energy-momentum content of matter must be in an area to produce the needed geometry. From as general a standpoint as a matter such as this can be, these are the properties normally suggested to be needed to stabilize a worm hole. As a side note, the notion of negative mass matter is certainly rather disturbing, however because of vacuum fluctuations near a black hole it is not considered to be an impossibility.
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In astrophysics, a white hole is a postulated celestial body that spews out matter, in other words an anti-black hole, or the time reversal of a black hole.
White holes have long been speculated about in Science Fiction. They have been postulated as a means of transport between points of spacetime and even different universes. Due to a black hole's suggested funnel-like nature, matter travelling through a black hole and exiting through a white hole would be crushed to an immensely dense but small size, this would go against transportation because it is very unlikely that a white hole would have the ability to recompose the matter to its original state prior to entering the black hole. The existence of white holes is hypothetical, as they appear to violate the second law of thermodynamics.
Other speculations include the hypothesis that quasars are actually white holes instead of supermassive black holes.
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