Wormholes

For the record, the existence of wormholes was actually a prediction developed from Einstein's field equations. Wormholes are also known as Einstein-Rosen bridges in the honor of the scientists behind their prediction. Wormholes have never been discovered in our universe, even though general relativity predicts that it exists whatsoever.

Let me just start off by saying that a wormhole is just a black hole without a singularity (core point). A wormhole is just like it sounds, it's in fact a tunnel in space-time that connects two different points in our space. It can connect two different stars, planets, galaxies or even parallel universes (i e.; if it exists). The tunnel is actually formed out of space-time that's highly curved due to forces just like that of a black hole. The other difference between a black hole and a wormhole is that a black hole has only one opening (event horizon or entrance) but in a wormhole, there are two different event horizons. One of them is an entry port while the other being an exit port. To be more clear, the wormhole's entrance would be a black hole that would be sucking matter inside and the exit would be a white hole, which would be spewing matter outside.

But even though the concept of wormholes pretty much makes sense hypothetically, many physicists still think that wormholes can't happen in reality at all. A fair argument for that is that a traversable wormhole cannot survive because of the strong force of gravity that compresses it into a singularity just to end up like a black hole. The attractive forces are far larger than the repulsive forces in space that right after a wormhole is created, it will collapse into a singularity before anything could pass through it. For a wormhole to exist in a stable manner, a new ingredient called 'exotic matter' is needed. Exotic matter is nothing like ordinary matter. All ordinary matter (including living things) has a positive energy density which causes gravity to act as an attractive force. Now when a particle has negative energy, the gravitational force due to this particle would be repulsive and will tend to push away from itself. 

Physicists believe that the presence of this exotic matter in wormholes could actually prevent them from closing down or collapsing due to the repulsive forces and negative energy density. Now the real question is how do we get access to negative energy particles. It can be observed through the Casimir Effect, an experiment that proves that empty space or vacuum is actually not empty at all. Instead, space is filled with particle-antiparticle pairs that momentarily appear and disappear. The so-called 'exotic matter' actually comes from the energy fluctuations created by the antiparticles (opposite to its ordinary particle pair). However, this not possible practically because a large amount of exotic matter or negative energy is required and the above effect isn't actually a feasible option.

Yet, there is also a chance these wormholes could actually pave the way in time travel and teleportation.