What is Wormhole ?

The first problem is size. Primordial wormholes are predicted to exist on microscopic levels, about 10–33 centimeters. However, as the universe expands, it is possible that some may have been stretched to larger sizes.

Another problem comes from stability. The predicted Einstein-Rosen wormholes would be useless for travel because they collapse quickly.

"You can go into the future or into the past using traversable wormholes," astrophysicist Eric Davis told LiveScience. 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."

"You would need some very exotic type of matter in order to stabilize a wormhole," said Hsu, "and it's not clear whether such matter exists in the universe."

However, British cosmologist Stephen Hawking has argued that such use is not possible. [Weird Science: Wormholes Make the Best Time Machines]

A wormhole is a theoretical passage through space-time that could create shortcuts for long journeys across the universe. Wormholes are predicted by the theory of general relativity. But be wary: wormholes bring with them the dangers of sudden collapse, high radiation and dangerous contact with exotic matter.

But more recent research found that a wormhole containing "exotic" matter could stay open and unchanging for longer periods of time.

"A wormhole is not really a means of going back in time, it's a short cut, so that something that was far away is much closer," NASA's Eric Christian wrote.

Exotic matter, which should not be confused with dark matter or antimatter, contains negative energy density and a large negative pressure. Such matter has only been seen in the behavior of certain vacuum states as part of quantum field theory.

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.

Wormholes were first theorized in 1916, though that wasn't what they were called at the time. While reviewing another physicist's solution to the equations in Albert Einstein's theory of general relativity, Austrian physicist Ludwig Flamm realized another solution was possible.

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.

If a wormhole contained sufficient exotic matter, whether naturally occurring or artificially added, it could theoretically be used as a method of sending information or travelers through space. Unfortunately, human journeys through the space tunnels may be challenging.

The whole thing is very hypothetical at this point," said Stephen Hsu, a professor of theoretical physics at the University of Oregon, told our sister site, LiveScience. "No one thinks we're going to find a wormhole anytime soon."

Wormholes contain two mouths, with a throat connecting the two. The mouths would most likely be spheroidal. The throat might be a straight stretch, but it could also wind around, taking a longer path than a more conventional route might require.

Certain solutions of general relativity allow for the existence of wormholes where the mouth of each is a black hole. However, a naturally occurring black hole, formed by the collapse of a dying star, does not by itself create a wormhole.

Science fiction stories make wormhole travel look relatively straightforward, if not exactly easy. The physicists' conception is more conservative and less encouraging: Naturally occurring wormholes, if they exist at all, are likely to be extremely small, about 10 septillion (10 25) times smaller than a typical atom.

Science fiction is filled with tales of traveling through wormholes. But the reality of such travel is more complicated, and not just because we've yet to spot one.

Creating a large wormhole, or artificially enlarging a small naturally occurring wormhole, would require the manipulation of large quantities of matter—planet loads of mass.

The first problem is size. Primordial wormholes are predicted to exist on microscopic levels, about 10–33 centimeters. However, as the universe expands, it is possible that some may have been stretched to larger sizes.

A wormhole 1 meter (about 1 yard) across would require the manipulation of objects with the mass of the planet Jupiter and the squeezing of them into a region about a meter wide.

"You would need some very exotic type of matter in order to stabilize a wormhole," said Hsu, "and it's not clear whether such matter exists in the universe

Worse, because the gravitational field of a wormhole is in some sense repulsive (one would not want a black hole to form), one would need to manipulate large quantities of what is called "exotic matter," which is basically negative energy matter with less energy than the energy of an equal volume of vacuum.

Exotic matter, which should not be confused with dark matter or antimatter, contains negative energy density and a large negative pressure. Such matter has only been seen in the behavior of certain vacuum states as part of quantum field theory.

Wormholes can most likely access parallel universes, different time periods within the universe and or places within a single universe.