WORMHOLES


A wormhole is a hypothetical tunnel-like object connecting two different points in space. A trip through the wormhole could take much less time than a journey between the same starting and ending points in normal space. Because no wormhole has ever been seen or physically created, many details have yet to become uncovered. Some scientists believe that the ends of a wormhole could be intra-universe (both exist in the same universe), while others believe it to be inter-universe (exist in different universes, and thus serve as a connecting passage between the two).

Wormholes arise as solutions to the equations of Einstein's Theory of Relativity. In fact, they crop up so readily in this context that some theorists are encouraged to think that real counterparts may eventually be fabricated and, perhaps, used for high-speed space travel and/or time travel. One problem with this theory is a known property of wormholes – they are highly unstable and would probably collapse instantly if even the tiniest amount of matter, such as a single photon, attempted to pass through them. Scientists have worked around the clock to find an answer for this called exotic matter.


TABLE OF CONTENTS


HISTORY

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Albert Einstein, the Wormhole's theoretical creator
The theory of wormholes goes back to 1916, shortly after Einstein published his general theory, when Ludwig Flamm, an obscure Austrian physicist, looked at the simplest possible solution of Einstein's field equations, known as the Schwarzschild solution. This describes the gravitational field around a spherically-symmetric non-rotating mass. If the mass is adequately dense, the solution describes a particular form of the phenomenon now called a black hole – the Schwarzschild black hole. Flamm realized that Einstein's equations allowed a second solution, known as a white hole, and that the two solutions, describing two different regions of space time were connected by a space time conduit.1 Because Einstein’s theory has nothing to say about where these regions of space time might be in the real world, the black hole "entrance" and white hole "exit" could be in different parts of the same universe or in different universes.

In 1935, Einstein and Nathan Rosen further explored the theory of intra- or inter-universe connections in a paper whose actual purpose was to try to explain fundamental particles, such as electrons, in terms of spacetime tunnels threaded by electric lines of force. Their work gave rise to the formal name Einstein-Rosen bridge for what the physicist John Wheeler would later call a "wormhole." Wheeler's 1955 paper3 provides the first diagram of a wormhole as a tunnel connecting two openings in different regions of spacetime
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For more on the history of wormholes, click here .

SCHWARZSCHILD WORMHOLE

The Schwarzschild metric admits negative square root as well as positive square root solutions for the geometry. The complete Schwarzschild geometry consists of a black hole, a white hole, and two Universes connected at their horizons by a wormhole. The negative square root solution inside the horizon represents a white hole. A white hole is a black hole running backwards in time. Just as black holes swallow things irretrievably, so also do white holes spit them out. White holes cannot exist, since they violate the second law of thermodynamics. General Relativity is time symmetric. It does not know about the second law of thermodynamics, and it does not know about which way cause and effect go. The negative square root solution outside the horizon represents another Universe. The wormhole joining the two separate Universes is known as the Einstein-Rosen bridge. Schwarzschild wormholes certainly exist as exact solutions of Einstein's equations.

In contrast, there is a current debate on whether a Schwarzschild wormhole is even possible. The answer is yes, it certainly is possible, however there are a few circumstances that hinder such a wormhole:
  • When a realistic star collapses to a black hole, it does not produce a wormhole
  • The complete Schwarzschild geometry includes a white hole, which violates the second law of thermodynamics
  • Even if a Schwarzschild wormhole were somehow formed, it would be unstable and fly apart

For more on the Schwarzschild Wormhole, click here


PARTS OF A WORMHOLE

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A picture that shows the parts of a wormhole
Many different parts make up a wormhole. It is first formed by a black hole (which is created at the end stage of a star's life). The black hole sucks in all matter, including light, and has a singularity in its center. The singularity has no length, no width, no height, but essentially has the mass of the collapsing star. It has a large gravitational field strength, allowing it to overtake many things in the universe. However, this field strength is also so strong that it alters the physical laws and warps space.


The throat of the wormhole is the tube connecting the black hole and the white hole. The throat by itself is extremely small and cannot stay open. The strength is so massive, exceeding a billion quadrillion tons per square inch. In order to counter-act this force, a theoretical substance called negative matter is needed. Negative matter would have negative mass, and therefore possess anti-gravity properties.




TIME TRAVEL

external image speed-of-light-wormhole.gifIn theory, it is possible to time travel through a wormhole. Because a wormhole joins two different space times, you can travel starting in one and finish in another time period. Time travel through a wormhole consists of one side of the wormhole starting in one point in space-time and the end point at another point in space-time. Because the wormhole is not stable, negative matter would have to be used to keep it open (you must use an equal amount of negative matter as actual matter to balance out and keep the wormhole open). For this to occur one side of the wormhole would have to be accelerated to light speed. However, there are many potential dangers of time travel. If a ship brushes up against the sides of the wormhole throat, it would be completely and immediately destroyed by the vast gravitational forces hardly held in check there. Another danger is the instability of a wormhole and its ability to spontaneously collapse. Any ship caught in a collapsing wormhole would be immediately obliterated. Because a wormhole has never been physically created, the fate of a ship trapped inside a collapsing wormhole is unknown. Some experts say it might be crushed, while other believe it might precipitate out somewhere in normal space or it might be launched into a different universe altogether.

external image speed_of_light_fold.JPG

CURRENT OPINION

Until recently, theorists believed that wormholes could exist for only an instant of time, and anyone trying to pass through would run into a singularity. But more recent calculations show that a truly advanced civilization might be able to make wormholes work. By using something physicists call “exotic matter,” which has a negative energy, the civilization could prevent a wormhole from collapsing on itself. The stuff of science fiction, to be sure. But perhaps some day in the far future, it could also turn into science fact.

REFERENCES



    1. Flamm, L. "Comments on Einstein's theory of gravity," Physikalische Zeitschrift, 17, 48 (1916).
    2. Einstein, A., and Rosen, N. "The Particle Problem in the General Theory of Relativity", Physical Review, 48, 73 (1935)
    3. Wheeler, J. A. "Geons," Physical Review, 97, 511–536 (1955).
    4. http://www.speed-light.info/wormholes.htm
    5. http://www.mmaidana.com.ar/scw.html
    6. http://www.daviddarling.info/encyclopedia/W/wormhole.html
    7. http://www.wisegeek.com/what-is-a-wormhole.htm
    8. http://www.scientificamerican.com/article.cfm?id=follow-up-what-exactly-is