Wormholes are more properly called Einstein-Rosen Bridges, after the two men whose work in the early 20th century led to the first theories involving the extreme warping of space. However, the theory was considered too fantastic to be taken seriously at the time and was little more than an aberrant curiosity for decades. Then, in the 1980s, physicist Kip Thorne, trying to help his pal Carl Sagan create a believable means of interstellar travel for the novel Contact, looked hard at the old equations and, with the help of graduate students Michael Morris and Ulvi Yurtsever, found that wormholes perhaps werenít that far-fetched after all. In the years since, the theoretical study of wormholes has been expanded considerably by a number of leading physicists.
The actual physics behind wormhole formation are incredibly complex; in order to save on space and the readersí sanity, only extremely simplified versions are presented here. Links and references to more complete and technical works on the subject are provided at the end of this article.
In their simplest definition, wormholes are four-dimensional tunnels bored through the fabric of space-time itself. They can be created by warping space with very unlikely tools--either with singularities, which lie at the heart of those fear-inducing objects called black holes, or by tapping into the basic, planck-scale firmament of the universe itself.
A black hole is a spherical area in space that absorbs all light, energy, and matter that encounters it; a singularity is a pinpoint of super-collapsed matter, the remnant of a massive dead star, that lies at a black holeís center. The singularity has infinite density and no physical dimensions--no length, no width, no height. It is quite literally an infinitesimally tiny point with the mass of an entire star packed into it. Its gravity field is so immense that its escape velocity exceeds lightspeed--hence its radius of utter darkness as seen from the outside. This gravity field also warps space to such a degree that physical laws as we know them break down.
But a sufficiently advanced species could also use this warping of space to their own benefit, to drill shortcuts through the fabric of the universe to reach across the cosmos.
Despite what has been depicted in a number of sci-fi sources, naturally-occurring black holes do not give birth to wormholes--at least, wormholes that a spaceship could survive passage through. These wormholes form only at the birth of certain rare singularities, go nowhere except to space-time dead ends, and last only microseconds. Any ship unlucky enough to be caught in one would be crushed instantly by the immense gravitational forces crashing in on them as the wormhole collapsed, if it could survive passage that close to a black hole to begin with.
Black holes are not all alike; they come in a number of different varieties. It is only the artificial combination of very specific black hole characteristics that can give birth to a type of traversible wormhole called a Kerr-Newman Ringwarp.
A Kerr-Newman black hole must possess two important factors: a massive electrical charge and a high spin rate. These two factors affect the way the singularity warps space. By manipulating these as the original mass collapses allows the newly-born singularity to punch a hole through the fabric of space. At both ends of the new wormhole will be two black holes with the same singularity at their center.
Because the singularity has no physical dimensions, it does not actually "spin." Rather, the angular momentum oblates the singularity--"flattens" it out--into a ring. The more spin it has, the larger the ring will be. Inside the ring is the tunnel that the singularity has bored through the fabric of space at its creation, pried open. It is possible to expand the ring so its diameter can exceed the black holeís event horizon, the distance from the singularity at which its escape velocity exceeds light speed. At this point, the event horizon reconfigures itself around the singularity ring, allowing a ship to enter the Ringwarp through its center without being trapped by the black holeís gravity. And thus a traversible wormhole is born.
Expanding the ring diameter is tricky at best once the ringwarp is formed, so the best means of ensuring a large wormhole opening is piling on the angular momentum as the black hole is formed. Spinning the target mass to near lightspeed as it collapses is the best way. Extremely advanced and powerful gravity manipulation would also help. The ringwarp mouth can also be held open or expanded with generous amounts of negative energy, as explained below.
Instead of creating a tunnel to another portion of our universe, a Kerr-Newman Ringwarp can be used to punch a hole into hyperspace. It is possible ringwarps could all open into the same hyperspace, allowing the creation of "hypergates." The ship would enter one Kerr-Newman Ringwarp, travel through hyperspace, and exit through another Ringwarp in another star system. However, its also as likely that all ringwarps open into their own hyperspatial dead-ends, and canít be used for FTL travel this way.
A civilization that had to depend on Kerr-Newman Ringwarps for FTL travel would have their work cut out for them. First of all, they would have to sacrifice already-existing masses--planets and stars--to create them. Vast expenditures of energy would be needed to create them (spinning the mass up to near lightspeed, then collapsing it artificially) and to maintain them. They would also be quite delicate--even a relatively small mass (say, that of an average automobile) hitting the star-heavy ring could upset its equilibrium and send the entire wormhole collapsing.
The alien Cheela in the novel Starquake used a Kerr-Newman Ringwarp to save several human astronauts stranded in orbit around a neutron star. In the novel Ring by Stephen Baxter, the alien Xeelee constructed this type of wormhole using cosmic strings, in order to create an "escape hatch" out of the universe.
Tech Level: 23
|Wormhole openings are spherical and show 'reflections' of what's on the farside. Here, we see the distorted image of Earth and the moon from the far side of a wormhole. Artist unknown.|
Currently the "common" type of wormhole used by much of modern science fiction, it was first proposed by Michael Morris, Kip Thorne, and Ulvi Yurtsever in a famous paper in 1988. One of the best examples of it, naturally enough, can be found in Carl Saganís novel Contact. A wormhole was a central feature of the TV series Star Trek: Deep Space Nine. In the novel the Ring of Charon, by Roger MacBride Allen, an immensely powerful alien species called the Charonians use wormhole technology to steal the planet Earth itself.
One method of accessing wormholes involves not so much creating the tunnels through space/time as mining them from the subatomic quantum foam. According to theory, wormholes are constantly forming and collapsing at the planck-scale level of existence, the point where physical measurements become meaningless, around 10^-33 meters. At this level of existence, space/time is ruled by chaos and is far from stable or "firm," allowing structures like wormholes to form with relative ease.
The vast majority of the wormholes found here lead to only a few planck-lengths away. However, some can stretch many light years, and some may even lead to the other side of the cosmos. We can imagine a species with spectacularly advanced technology might possess the means to detect, stabilize, and expand these otherwise brief-lived quantum wormholes for macroscopic use.
However, expanding the wormhole mouth to usable dimensions and keeping it open takes enormous energies. The gravitational forces at work in the wormhole keeps trying to collapse its openings, requiring some counter-force to keep it open. To think of it another way, the "ocean" of space-time keeps trying to rush in and fill the "drainage" hole created by the wormhole. This creates unbelievable pressure at the wormhole mouth, far exceeding a billion quadrillion tons per square inch for a wormhole with an opening large enough to accommodate most spaceships, say several kilometers wide. This level of pressure is akin to having millions of earth-sized planets balanced on your thumb.
This problem of pressure can be counteracted in several ways. The first is the use of copious amounts of an as-yet theoretical substance called negative matter. Negative matter would have negative mass and would therefore possesses anti-gravity properties. Negative matter would line the wormhole mouths, counteracting the crushing wave of space-time trying to force its way in. Another way to keep the openings apart would be to use electromagnetic force fields or powerful artificial gravity fields, but keeping the wormhole mouth from collapsing with these methods may require the constant energy output of an entire star. Interstellar species might be forced to build dyson spheres or similar mega-artifacts in order to power their wormholes.
Passage through a wormhole would be as simple as flying through a large spherical chamber or tunnel; a vessel no more advanced than John Glennís original Mercury capsule could transit from one star system to the next once the wormhole was built and stabilized. Passage time would be mere minutes at most.
However, wormhole travel has its hazards. Brushing up against the sides of the wormhole throat would mean instant destruction for a ship, as it is shredded and crushed by the immense gravitational forces barely held in check there. Also, too large a mass passing through a wormhole might disrupt the delicate balance keeping it open, causing it to spontaneously collapse. Any ship caught in the mouth of a collapsing wormhole is instantly annihilated. The fate of a ship trapped inside a collapsing wormhole throat is unknown. It might be crushed, it might precipitate out somewhere in normal space, it might be launched into a different universe altogether, or it might be forever trapped in an isolated bubble of space/time with no hope of escape.
There is no limit to how far a wormhole can stretch. A wormhole can span the length of our entire universe as easily as it can the length of a football field. Also, wormholes mouths are not static fixtures; they can be moved. Because they can be electrically charged, a sufficiently powerful fleet of ships can move them using immense magnetic fields. The process would be slow, but one wormhole mouth can be "dragged" in this manner anywhere in the universe while its other opening can stay at its point of origin, allowing its builders to slowly explore the entire universe one far-flung star system at a time.
A Morris-Thorne-Yurtsever Wormhole could also be created from the collapse of matter or energy into a black hole, but this method is assumed to be much more difficult and risky because of the immense energies and forces involved beyond just stabilizing the wormhole. Instead of sacrificing worlds as in the Kerr-Newman scheme, however, a standard wormhole can also be made by creating a kugelblitz--a black hole formed by the collapse of highly concentrated energy as opposed to matter. Basically, if one can pile on enough energy in a small enough space in the right way, a kugelblitz will form, and with it a singularity with the right properties that could be expanded into a wormhole. In the novel Kaleidoscope Century by John Barnes, a small wormhole was formed by specially-tamped, overlapping thermonuclear explosions on the opposite side of the sun from Earth.
Though wormholes are traditionally envisioned as being space-borne objects, its certainly possible for them to be located on the surface of a planet or even on a spaceship. However, unless theyíre "locked" in place with electromagnetic or gravitational fields, they will tend to wander as the ship or planet moves about. They are singularities after all, and will still behave like point sources of gravity. On a planet, it is even likely the wormhole would start to orbit the planetís center of gravity once free of its moorings, completely unmindful of any matter in its way. Assuming it does not instantly collapse, it could plunge up and back through the planetís crust and mantle on an elliptical orbit around the core, sending megatons of matter through itself every second, leading to catastrophe at both ends. However, this effect can be of beneficial use as well. In the novel Ring by Stephen Baxter, the human civilization used wormholes in this manner to "mine" the interiors of stars.
The usual way wormholes are envisioned in science fiction is as a two-dimensional door. For a Morris-Thorne-Yurtsever wormhole, however, a wormhole mouth would be spherical. You could enter into it in any direction and still come out the other side, which would also have a spherical opening. Remember that wormholes are four-dimensional tunnels with three-dimensional openings, much like a three-dimensional hallway has two-dimensional openings (doorways.) When looking at the wormhole mouth, you would see a spherical "reflection" of what lay on the other side of the wormhole.
Standard wormholes can also be used as time machines. This will be discussed in a future section dealing with time travel.
Tech Level: 25
|A cubical Visser wormhole in orbit about Earth. Artist unknown.|
An admittedly bizarre idea originally proposed by Matt Visser of Washington University in St. Louis. A Visser wormhole suggests using cosmic strings of negative matter to pry open a wormhole mouth, much like struts of metal or wood can hold open mundane tunnels. The strings would be configured into a cube, with a flat-space wormhole mouth stretched out on each "face" of the cube. The entire cube may be the wormhole mouth, much like a standard wormhole, only cubical in shape instead of spherical. Or each side of the cube may be a different wormhole mouth, each leading to different cubical wormhole mouths at different destinations.
Even if negative matter cosmic strings exist, acquiring them as well as manipulating them into so precise a configuration would require vast technological sophistication beyond what we can easily imagine.
The Fourth Dimension (and how to get there) by Rudy Rucker
Cosmic Wormholes by Paul Halpern
Hyperspace: A Scientific Odyssey Through Parallel Universes, Time Warps, and the 10th Dimension by Michio Kaku
"Wormholes & Time Machines" by Michael S. Morris, Kip S. Thorne, and Ulvi Yurtsever, Physical Review Letters 61, 1446 (1988).
On The Web:
http://casa.colorado.edu/~ajsh/schww.htmlhttp://www.npl.washington.edu/AV/altvw33.html http://www.daviddarling.info/encyclopedia/W/wormhole.html http://www.zamandayolculuk.com/cetinbal/wwormholew.htm http://www.zamandayolculuk.com/cetinbal/NEGATIVEENERGYWORMHOLESWARP.HTM