Why wormholes are a possibility

The researchers chose a comparatively simple "semiclassical" approach. They combined elements of relativity theory with elements of quantum theory and classic electrodynamics theory. In their model they consider certain elementary particles such as electrons and their electric charge as the matter that is to pass through the wormhole. As a mathematical description, they chose the Dirac equation, a formula that describes the probability density function of a particle according to quantum theory and relativity as a so-called Dirac field.

As the physicists report in their study, it is the inclusion of the Dirac field into their model that permits the existence of a wormhole traversable by matter, provided that the ratio between the electric charge and the mass of the wormhole exceeds a certain limit. In addition to matter, signals—for example electromagnetic waves—could also traverse the tiny tunnels in spacetime.

The microscopic wormholes postulated by the team would probably not be suitable for interstellar travel. Moreover, the model would have to be further refined to find out whether such unusual structures could actually exist.

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Study of such strange geometries can help better distinguish the boundaries of behavior permitted in the theory of general relativity, and also possibly provide insights into effects related to quantum gravity. A wormhole has two mouths connected by a "throat," and provides a path that a traveler could follow to a distant point. The path through the wormhole is topologically distinct from other routes one could follow to the same destination.

What is meant by topologically distinct? If an ant wished to crawl from one side of an apple to another, there are many possible paths on the surface connecting the starting point to the destination.

These paths are not distinct topologically: a piece of elastic string fixed at the starting and ending points, and lying along one such path, could be slid and stretched over the surface to lie along any other such path.

Now imagine that the ant instead crawls through a wormhole in the apple. A piece of string passing through the wormhole cannot be smoothly moved in such a way as to lie along one of the surface paths or through another wormhole with the same end points but different route.

For the purposes of science fiction, it is usually assumed that a wormhole in space-time represents a shortcut--that by traveling a small distance through the wormhole tunnel, you might end up at a destination which could be light-years away through conventional space.

In terms of the theoretical physics of wormholes, however, there is no particular reason why the distance must be shorter; the wormhole might actually be the longer route analogous to a long, complicated, twisting hole that a worm might leave in an apple, where the entrance and exit mouths might be quite close to each other on the surface. Wormholes can exist within the classical black hole solutions of the Einstein equations.

These wormholes are useless for travel, however, as they collapse before any spaceship or even a ray of light could pass through them. In addition, the black holes formed by a collapsing star have no associated wormhole at all. Interest in such wormhole solutions in general relativity was stimulated when Michael Morris and Kip Thorne of the California Institute of Technology examined the general properties necessary for a wormhole to remain open. They found that if a wormhole is static and unchanging in time, then it must contain "exotic" matter.

Such matter has negative energy density and a large negative pressure or tension --larger in magnitude than the energy density. Such matter is called "exotic" because it so little resembles all forms of known matter.

All the forms of matter familiar to physicists and chemists have positive energy density or, equivalently, positive mass , and pressures or tensions that are always less than the energy density in magnitude.

In a stretched rubber band, for example, the density is 10 14 , or million million times, greater than the tension. The one possible source of "exotic" matter known to theoretical physics lies in the behavior of certain vacuum states in quantum field theory.

This possibility is the focus of most current theoretical research involving wormholes. Such research has shown that it appears difficult to use quantum effects to open a wormhole much larger than the characteristic length associated with quantum gravity, known as the Planck length about 10 centimeter. If the wormhole were not much larger than this, then not only would it be useless for transporting spaceships, but quantum gravity would be needed to describe the hole.

Young Star Clusters Oct 12, Apr 15, Sep 10, Recommended for you. Black hole found hiding in star cluster outside our galaxy 10 hours ago. Nov 10, Data from the Fermi Large Area Telescope suggests there is a particle accelerator in the galactic center Nov 10, Load comments Let us know if there is a problem with our content.

Your message to the editors. Your email only if you want to be contacted back. Send Feedback. Thank you for taking time to provide your feedback to the editors. E-mail the story Scientists investigate the possibility of wormholes between stars. Your friend's email. Your email. I would like to subscribe to Science X Newsletter. Learn more. But it won't be easy: "It would take a Herculean effort to turn a wormhole into a time machine.

It's going to be tough enough to pull off a wormhole. However, British cosmologist Stephen Hawking has argued that such use is not possible. Although adding exotic matter to a wormhole might stabilize it to the point that human passengers could travel safely through it, there is still the possibility that the addition of "regular" matter would be sufficient to destabilize the portal. Today's technology is insufficient to enlarge or stabilize wormholes, even if they could be found.

However, scientists continue to explore the concept as a method of space travel with the hope that technology will eventually be able to utilize them. Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at: community space. Nola Taylor Tillman is a contributing writer for Space. She loves all things space and astronomy-related, and enjoys the opportunity to learn more. In her free time, she homeschools her four children.