Wormholes
Sarah Steiner
Physics 4D
May 9, 2003
Semester Project
Have you ever wondered about traveling through time maybe to see the future or take a peek at your family’s past? Some scientists predict that wormholes could be the key to time travel in the future.
Wormholes are theoretically a possible consequence of Einstein’s theory of General Relativity. Einstein conceived the idea that mass warps space. Arthur Eddington proved this in 1919 when he used a solar eclipse to prove that the moon bent the light from the sun. The larger the mass, the more space will be indented. Einstein suggested that objects don’t fall; rather they roll into the depressions in space. Objects that are orbiting are just rolling around the depression. “Theoretically, a wormhole could be formed when two or more massive bodies warp space and the fabric of space collides, forming a tunnel between distant places (bcc).”
A wormhole is the combination of a white hole and a black hole. At the other end of every black hole it is believed that there is a white hole. Scientists believe that there could be a great distance between the white hole and the black hole. The black and white holes are connected by a wormhole. So in theory, if a person entered a black hole they could exit through the white hole. The process of traveling through the wormhole may move the traveler to a different universe or dimension or possibly allow them to travel through time.
Think about space as a piece of cloth. If a large weight is set on the cloth it will sag towards the center. If you also had a weight on a piece of cloth parallel to the first also with a weight, the two weights will sag towards one another. These super massive black holes cause a tear in space-time and this tear is the wormhole. These two regions would meet and form a wormhole. The wormhole will connect the two regions and depending where the holes are located, they may connect different universes or they may just connect different regions in the same universe (Figure 1). This would allow for time travel because by jumping through a worm hole it would be possible to exceed the speed of light and travel into the future.
The theory of wormholes for time travel is fascinating but there are some problems with the idea. It is thought that wormholes could only exist on a very small scale. John Wheeler says, “Larger wormholes would collapse under their own gravity so rapidly that even a beam of light would not have enough time to travel through them.” In order to overcome this barrier negative energy is needed. It is thought that if negative energy were used to hold the wormholes open, then travel might be possible. The negative energy is also important if a light signal is to be passed through the hole. In order to have a wormhole that can at least carry light, negative energy would be required. The light is converging as it enters the wormhole but in order to exit again it must diverge somewhere inside the wormhole. The negative energy acts like a diverging lens inside and would allow the light to leave again (Figure 2). In order to engineer a wormhole that would allow for space travel, large amounts of very thin negative energy would be needed. Visser calculated that, “the maximum allowed thickness of the negative energy band is proportional to the cube root of the throat radius.” So if it were possible to increase the radius of the wormhole to one light year the negative energy layer would still need to be thinner than the radius of a proton. Although the layer of negative energy would be very thin there would still be a huge amount needed. Visser estimates, “The negative energy required has a magnitude equivalent to the total energy output of a star over its 10,000,000,000 year lifespan.” In order to use wormholes for time travel, engineers would have to figure out how to create and contain large amounts of negative energy.
Negative energy is not completely science fiction. Some has been produced in the lab. It arises from Heisenberg’s uncertainty principle, which requires “that the energy density on an electric, magnetic or other field fluctuate randomly (Ford).” When the average energy density is zero there is still fluctuation in a vacuum. “In quantum theory, the usual notion of zero energy corresponds to the vacuum with all these fluctuations. So if one can somehow contrive to dampen the undulations, the vacuum will have less energy than it normally does – that is, less than zero energy (Ford).” Researchers have created special states, “in which destructive quantum interference suppresses the vacuum fluctuations (Ford).” These squeezed states involve negative energy (Figure 4).
Another problem with wormhole travel is the huge gravitational force inside the throat of the wormhole. It is thought that negative energy could be used to keep this huge gravitational force from crushing anything that dared to pass through it. The throat of the wormhole compresses objects and greatly increases their density (mass/volume), as the huge gravitational force is simultaneously closing off the wormhole. Once an object enters the wormhole it not only would be smashed, but it would also never be able to leave because the hole closes off. Large quantities of negative energy would be needed to allow for travel.
Currently wormholes are still science fiction. But in the future people may be able to use wormholes to travel to distant galaxies. Artists have illustrated the possibility of dragging a wormhole with a space shuttle and using them to build bridges to distant places (Figure 3). Based on Einstein’s general theory of relativity wormholes are a possibility. But for the moment they are only science fiction.
Bibliography
Greene, Brian (1999). The Elegant Universe (p. 264-265). New York. W. W. Norton & Company.
Hawking, Stephen (2001). The Universe in a Nutshell (p. 135-137). USA. Bantam.
Ford, Lawrence H. Negative Energy, Wormholes and Warp Drive. Scientific America. January 2000.
BCC News. Wormholes take on a new dimension. Http://news.bbc.co.uk/1/hi/sci/tech/710812.stmWormholes.
Wormholes and such: Principle of Equivalence. http://zebu.uoregon.edu/~imamura/122/mar13/travel.html
Wormholes.
http://www.tcnj.edu/~hofmann/worm%20holes.htm
http://image.gsfc.nasa.gov/poetry/ask/a11339.html
Figure 1:
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Figure 4:
Waves of light ordinarily have a positive or zero energy density at different points in space (top). But in a so-called squeezed state, the energy density at a particular instant in time can become negative at some locations (bottom). To compensate, the peak positive density must increase.