Worm Holes are the hypothetical theoretical connection between a black hole and a white hole.
Specifically defined, a black hole is a region in space where the velocity of escape exceeds the speed of light in that medium. When a star dies and begins to shrink a name is given to the size below which it must shrink in order to become a black hole. The name for this size is the star's "Schwarzchild Radius" and the primary factor which determines whether or not a star will shrink below it's Schwarzchild Radius is its initial mass.
Schwarzschild Radius also called gravitational radius, distance that defines the size at which a spherical astronomical object such as a star becomes a black hole. A black hole is an object so dense that not even light can escape the pull of its gravitational force. If an object collapses to within its Schwarzschild radius, it becomes a black hole. The radius is named after German astronomer Karl Schwarzschild, who derived the first model of a black hole in 1916. Nothing, not even a particle moving at the speed of light, can escape the gravitational pull of a black hole.
Therefore, the Schwarzschild radius is the largest radius that a body with a specific mass can have and still keep light from escaping. The formula for the Schwarzschild radius of a body is the Schwarzschild radius of the body, G is a constant known as the universal constant of gravitation, M is the mass of the object, and c is the speed of light.
To find the equation for the Schwarzschild radius of an object, Schwarzschild needed to know how massive a body has to be to keep light from escaping and how light behaves in such a strong gravitational field. French astronomer Pierre Laplace found the equation for escape velocity, or the speed an object needs to overcome the gravitational force of a body. Laplace noted in 1800 that the escape velocity would be greater than the speed of light for an object leaving a very small, dense body. German American physicist Albert Einstein explained how light behaves in a strong gravitational field in his general theory of relativity, published in 1916. In 1916 Karl Schwarzschild derived the first model of a black hole with help from the work of Laplace and Einstein.
The Schwarzschild radius of a black hole marks its event horizon, or the boundary past which light can enter but not escape. Astronomers believe that once an object collapses to within its Schwarzschild radius, it continues collapsing until it becomes a singularity, or a point with infinite density and a radius of zero.
The sun has a mass of 2x1030 kg (4x1030 lb) and a radius of about 700,000 km (about 400,000 mi). Its Schwarzschild radius is about 3 km (about 2 mi). If the sun were to collapse into a sphere with a radius of less than 3 km, light from the sun would be trapped and the sun would become a black hole. The sun, however, is not massive enough for it to collapse to this size and become a black hole.
An object with a mass equal to that of the earth would have a Schwarzschild radius of about 3 mm (about 0.1 in). For an object with Mount EverestŐs mass, the Schwarzschild radius is only about 1x10-11 mm (4x10-13 in). Some astronomers believe that any black hole smaller than this would be relatively unstable and would evaporate quickly, releasing gamma rays (seeX Ray). Astronomers have speculated that the mysterious sources of celestial gamma ray bursts may be evaporating primordial black holes.
Only stars that expire with around 3 times a much mass as the sun can hope to attain black hole status. In order for a star to have much of a chance of having a mass this high after it's inner nuclear fire is extinguished it must have begun its life with more than 50 times the mass of the sun. The name for this lower mass limit which a star must have after death to become a black hole is "Oppenheimer's Limit."
A star much smaller than this will not have enough mass to collapse into a black hole and will have a very different death in store for it that is not within the scope of our discussion here. If a star does shrink below it's Schwarzchild Radius there is a name assigned to the imaginary sphere at the Schwarzchild Radius, the "Event Horizon." At twice the distance of the Event Horizon is the "Photon Sphere," or the distance at which a photon may be caught in orbit around a black hole.
This discussion of escape speeds and trapped photons should prove somewhat startling and/or disturbing. It leads to the simple question, "if not even light can escape, and no particle with mass can go faster than light, then what happens to anything caught in the pull of a black hole?" The simple answer is that it never escapes, it is drawn into the black hole with an unescapable gravitational force. However there are other possibilities, and it is here that we look to relativity for an explanation. From a relativistic viewpoint, a black hole is a location of extreme distortion in the space time continuum.
Looking at things this way, every object of mass in the universe creates a distortion in space time, the more massive the object, the larger the distortion. A black hole is different in its definition however, because it is a distortion so extreme that it has infinite curvature, it is actually a tear in space time. Under this definition at the center of every black hole is a space time singularity. What this singularity leads to or could be used for are completely theorized, but will be discussed in more depth later.
White Holes are the theoretical exact opposite of black holes, and their existence is implied by a negative square root solution to the Schwarzchild metric. The Schwarzchild metric is based on General Relativity, which is time symmetric. This means that the most technical definition of white hole is simply a black hole running backwards in time. It is a location in space time that, instead of being impossible to escape, is impossible to reach.
Under the definition given by the solution to this equation they repel everything, including massive particles as well as photons, nothing can enter them. We have never discovered a white hole, and given these properties we believe that they would be rather difficult to miss. Furthermore, an object that acts in this manner directly violates the second law of thermodynamics which states that heat naturally flows from a region of high temperature to a region of low temperature.
The contradiction this causes is that any object with heat should eventually dissipate it's heat energy to its surroundings, and a white hole by definition never runs out of heat or mass, thus standing in violation of every other major law of physics we have in order to hold true to the second law of thermodynamics.
This, however, only applies to our universe. The same equations that suggest the existence of white holes also seem to imply that they exist in a universe parallel to our own, and would exist connected to a black hole by way of a worm hole in order to complete the Schwarzchild geometry suggested by the equation which predicted the existence of black holes. This worm hole joining 2 separate universes is known as the Einstein-Rosen bridge and is one of the most fascinating concepts in theoretical physics.
While the concept of this connection is extremely exciting we know very little about it, as we have no white holes to observe and black holes are extremely hard to detect given their light absorbing nature. Given our current understanding of black holes and white holes we are not even sure of such a connection could exist, or if it did, where it would take us. Current knowledge does not even give enough information to suggest if such a link would even be to somewhere else in our own universe.
Unfortunately, current theory does not even allow for the ultimate destination of a worm hole to be much of a worry because it is believed that passing through a worm hole is impossible. Instant death would be a near certainty given any imaginable method of protection, and no matter the circumstances return would be impossible given everything we know about black holes and the way they would interact with white holes.
The only method where death would not be a near certainty is if a worm hole could somehow be stabilized for longer than the brief amount of time under which they are naturally believed to remain stable. This is an impossibility given our current understanding of science and would obviously be grander in scope than anything ever attempted by mankind in the history of Earth.
It is theoretically possible, although highly improbable that a worm hole could somehow be stabilized to allow safe passage through it. The only theoretical way this could be done that I was able to find involves using 'exotic matter', or matter unlike any we know, highly exotic matter. In order to stabilize the worm hole the throat of the singularity would have to be threaded with this matter which would be spherical in nature. The properties this matter would have to have would be negative mass, and yet still be capable of exerting a positive surface pressure.
It must have these two properties for very specific reasons, the negative mass ensures the the throat of the worm hole lies outside the protected region and the positive surface pressure is the property that prevents the throat of the worm hole for collapsing. These properties of matter are not arbitrary or purely theoretical, we have determined this is the type of space-time geometry most likely needed to produce a stable worm hole. Einstein's equations then specify what the energy-momentum content of matter must be in an area to produce the needed geometry. From as general a standpoint as a matter such as this can be, these are the properties normally suggested to be needed to stabilize a worm hole. As a side note, the notion of negative mass matter is certainly rather disturbing, however because of vacuum fluctuations near a black hole it is not considered to be an impossibility.
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