Science fiction writers often look for a device which can transport objects through space and time. A wormhole is a theoretical device which might allow such a transport. According to theoretical physics there might be a shortcut through spacetime which could be exploited.
When the theory of general relativity was developed, scientists began to think of the universe as a four dimensional construct in which the dimensions of space and time are interlinked. Wormholes raise the possibility that it might be possible to “jump” between the dimensions. The easiest analogy is to consider life on a sphere like the Earth. In everyday life people travel around on a two dimensional surface. A flight from New York to New Zealand takes place over the surface. The journey would be substantially shorter if only we could travel through the centre of the Earth. For a long time scholars thought that humans lived on a two dimensional world rather than a three dimensional surface. The conclusion from general relativity is that they live on a three dimensional surface in a four dimensional world. In the same way that a tunnel through the Earth could be a three dimensional cut through a two dimensional world, a wormhole may be a four dimensional cut through a three dimensional world. Theoretically, a wormhole could be a jump to another point in space, or to another point in time. It is often useful to think of a wormhole as a tunnel between two points in space and time.
Albert Einstein formulated his General Theory of Relativity in 1915. In the same year, Karl Schwarzchild surprised everybody including Einstein by finding a unique solution to the Einstein equations. Schwarzchild’s achievement is especially remarkable because he was suffering form a skin disease while serving in the trenches with the German army in Russia. Schwarzchild discovered the equations that define a black hole.
In 1921 the German mathematician Hermann Weyl speculated that there might be mass and energy distributions that distort space and time into loops that he called wormholes,
When Albert Einstein and Nathan Rosen reviewed the Schwarzchild equations in 1935 they realised that the equations were symmetric in time. The equations defined a black hole which sucked in matter and also defined a white hole that spewed out matter. The scientists reasoned that a wormhole, or a Einstein-Rosen bridge could connect one universe to another through a black hole. When John Archibald Wheeler and Robert W. Fuller studied the Rinstein Rosen Bridge, or Schwarzchild wormhole in more detail they found that it was unstable. Their result published in 1962 stated that the connection between the two universes would break off before a particle, even travelling at the speed of light, had time to traverse the black hole.
John Archibald Wheeler claims that he popularised the term wormhole in America in 1957. Although apparently not feasible in science wormholes have become a popular device in science fiction plots. Wormholes potentially allow inter-galactic travel within a human lifetime.
More recent research has focused upon traversable wormholes in which the wormhole tunnel is held open long enough for particles and/or light to transit. The leading protagonist is Kip Thorne a theoretical physicist whose interest was stimulated by Carl Sagan who came to him to check the scientific accuracy of his novel Contact published in 1985.
Kip Thorne and his graduate student Mikie Morris published a ground breaking paper in 1988 which showed that the wormhole could be held open by exotic particles not yet known in nature. The exotic particles would require a mysterious negative mass. Scientists have subsequently speculated that if the universe is made of more than four dimensions the wormhole tunnel can be kept open without the need for exotic particles.
One of the great mysteries in science concerns how gravitational theory interacts with quantum theory. The mathematical theory which predicts the wormhole is entirely derived from general relativity which defines the very large. Quantum theory defines the world of the ver6y small and is relevant because the wormhole tunnels currently envisaged are extremely thin. At present scientists are considering whether individual particles could traverse them not humans or spaceships.
Wormholes are an intriguing theoretical idea which has not been seen in practice. Despite this, many scientists believe that they exist. In physics mathematical solutions have a habit of anticipating new physical phenomena.
